Journal of Colloid And Interface Science (v.367, #1)
Nanotribological and nanomechanical properties of skin with and without cream treatment using atomic force microscopy and nanoindentation
by Bharat Bhushan (pp. 1-33).
Display Omitted► Skin cream reduces the surface roughness and increases the hydrophilic properties of skin. ► The cream film unevenly distributes on skin surface. ► The higher viscosity results in higher friction and longer durability. ► Cream treated skin reduces the charge build up on skin surface. Relative humidity facilitates charge dissipation. ► Synthetic skin provides a good simulation for the skin and can be used in nanotribology research.Various beauty care products involve surface interaction between the product and the skin surface they are applied to. Friction, adhesion and wear during sliding between the treated surface and the rubbing surfaces need to be optimized. Skin cream is used to improve skin health and create a smooth, soft, and flexible surface with moist perception by altering the surface roughness, friction, adhesion, elastic modulus, and surface charge of the skin surface. Rheology of skin cream as a function of cream thickness and strain rate and the binding interaction between skin cream and skin surface and operating environment are some of the important factors affecting the smooth feel and repair of the skin surface.Atomic force microscopy (AFM) and nanoindentation have recently become important tools for studying the micro/nanoscale properties of human hair, hair conditioner, skin, and skin cream. In this paper, we present an overview of the nanotribological and nanomechanical properties of skin with and without cream treatment as a function of operating environment. Relevant mechanisms are discussed. Next, the result of a triboelectrification study of skin with and without cream treatment is presented. Finally, an overview of attempts to develop a synthetic skin for research purposes is presented.
Keywords: Skin; Skin cream; Surface roughness; Friction; Adhesion; Wear; Static charge; Mechanical properties
Structural analysis of zeolite NaA synthesized by a cost-effective hydrothermal method using kaolin and its use as water softener
by A.R. Loiola; J.C.R.A. Andrade; J.M. Sasaki; L.R.D. da Silva (pp. 34-39).
The graph shows the action of zeolite on the NAA heavy water.Display OmittedSquare 1 - zeolite with sodium promotes ion exchange of calcium and magnesium present in water hard. ► Square 2 - water free of calcium and magnesium captured by zeolite. ► Square 3 - calcium and magnesium present in hard water withheld in the sites of adsorption.Zeolite 4A (LTA) has been successfully synthesized by a hydrothermal method, where kaolin was used as silica and alumina source. The synthesized zeolite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser granulometry, and FTIR spectroscopy. XRD data from the Rietveld refinement method confirmed only one crystallographic phase. Zeolite A morphology was observed by SEM analysis, and it showed well-defined crystals with slightly different sizes but with the same cubic shape. Particle size distribution of the crystals was confirmed by laser granulometry, whereas FTIR spectroscopy revealed significant structural differences between the starting material and the final zeolite product used as water softener.
Keywords: Zeolite NaA; Metakaolin; Rietveld refinement; Water softener
Using colloid lithography to fabricate silicon nanopillar arrays on silicon substrates
by Jem-Kun Chen; Jia-Qi Qui; Shih-Kang Fan; Shiao-Wei Kuo; Fu-Hsiang Ko; Chih-Wei Chu; Feng-Chih Chang (pp. 40-48).
Display Omitted► Generating a density adjustable AuNP self-assembly layer onto the Si surface. ► Self-assembled AuNP layer is patterned as 200nm resolution line by lithography. ► Si nanopillars featured high density and aspect ratio are generated by AuNP mask. ► We fabricate Si nanopillar array as 200nm resolution line patterns on the surface.In this study, we partially grafted geminal silanol groups in the protecting organic shells on the surfaces of gold nanoparticles (AuNPs) and then assembled the alkyl-AuNP-Si(OH)4 particles onto the surfaces of silicon (Si) wafers. The density of assembled AuNPs on the Si surface was adjusted by varying the geminal silanol group content on the AuNP surface; at its optimal content, it approached the high assembly density (0.0254particles/nm2) of an AuNP assembled monolayer. Using reactive-ion etching (RIE) with the templates as masks, we transferred the patterned AuNP assemblies to form large-area, size-tunable, Si nanopillar arrays, the assembly density of which was controlled by the dimensions of the AuNPs. Using this colloidal lithography (CL) process, we could generate Si nanopillars having sub-10-nm diameters and high aspect ratios. The water contact angles of the high-aspect-ratio Si nanopillars approached 150°. We used another fabrication process, involving electron beam lithography and oxygen plasma treatment, to generate hydrophilic 200-nm-resolution line patterns on a Si surface to assemble the AuNPs into 200-nm-resolution dense lines for use as an etching mask. Subsequent CL provided a patterned Si nanopillar array having a feature size of 200nm on the Si surface. Using this approach, it was possible to pattern sub-10-nm Si nanopillar arrays having densities as high as 0.0232nm−2.
Keywords: Silicon nanopillar array; Very-large-scale integration; Colloidal lithography
A novel orchid-like polyaniline superstructure by solvent–thermal method
by Mu Yang; Zhaojun Xiang; Ge Wang (pp. 49-54).
Display Omitted► A new orchid-like polyaniline has been obtained by solvent–thermal method. ► The morphology of the synthesized polyaniline can be well controlled. ► The formation mechanism is proposed based on the experimental results.An orchid-like polyaniline (PANI) structures was synthesized by initialing the polymerization at 80°C and growing at 25°C using ethanol and water as co-solvent in the presence of toluene-p-sulfonic acid (p-TSA) as the dopant. The “flowers” are consisted of 8–14 pieces of “petals” with 5–8μm in length. By adjusting the molar ratio of p-TSA/aniline, the cooling rate and the component of the solvent, flake-like and peony-like morphology can also be obtained. The formation mechanism of the orchid-like structure is proposed.
Keywords: Orchid-like; Polyaniline; Assemble; Superstructure
Characterization of paraffin oil emulsions stabilized by hydroxypropyl methylcellulose
by Taiki Futamura; Masami Kawaguchi (pp. 55-60).
S–S sweep curves of paraffin oil emulsions stabilized at various HPMC concentrations below C*.Display Omitted► Paraffin oil was almost emulsified by HPMC above C*/20. ► Yield stress of the emulsion increased as the HPMC concentration increased. ► All emulsions behaved as solid-like viscoelastic matter.To study the relationship between emulsion stability and polymer emulsifier concentration, the preparation of paraffin oil emulsions by hydroxypropyl methylcellulose (HPMC) was carried out with HPMC concentrations below the overlapping concentration ( C*) of HPMC. The stability of the emulsions incorporating HPMC was investigated by measuring the creaming velocity, volume fraction of emulsified paraffin oil, oil droplet size, and some rheological responses such as the stress–strain sweep curve and strain and frequency dependences of dynamic viscoelastic moduli. The paraffin oil was almost emulsified by HPMC above C*/20: the volume fraction of paraffin oil in the emulsion was higher than 0.72. Increasing in the HPMC concentration led to decreases in both the average oil droplet size and creaming velocity and an increase in the yield stress. All emulsions behaved as solid-like viscoelastic matter. Additionally, the measured dynamic storage moduli were compared with those calculated from a relationship based on functions of the volume fraction of oil in the emulsions and Laplace pressure; good agreement between the measured and calculated moduli was obtained. On the other hand, at HPMC concentrations below C*/50, the emulsified paraffin oil became unstable and the oil and the HPMC solution eventually separated.
Keywords: Paraffin oil emulsion; Hydroxypropyl methylcellulose; Overlapping concentration; Creaming velocity; Rheological responses; Laplace pressure
Magnetic-fluorescent nanohybrids of carbon nanotubes coated with Eu, Gd Co-doped LaF3 as a multimodal imaging probe
by Bingdi Chen; Hui Zhang; Ning Du; Bo Zhang; Yulian Wu; Donglu Shi; Deren Yang (pp. 61-66).
.Display Omitted► Magnetic-fluorescent nanohybrids were designed by a LBL self-assembly technique. ► The nanohybrids consist of lanthanide doped nanocrystals on the surface of MWNTs. ► We circumvented the PL quenching of lanthanide by growth of a SiO2 shell spacer. ► The nanohybrids showed powerful T1 and T2-weighted MRI signal. ► The nanohybrids were promising for multimodal MRI/optical imaging.Multifunctional magnetic-fluorescent nanohybrids were successfully fabricated by a facile layer-by-layer (LBL) self-assembly of in situ generated Eu, Gd co-doped LaF3 nanocrystals (LaF3:Eu:Gd) on the surface of multi-walled carbon nanotubes (MWNTs). Photoluminescence (PL) quenching occurred when LaF3:Eu:Gd nanoparticles were directly coated on the surface of MWNTs. By growth of a SiO2 shell spacer between MWNTs and LaF3:Eu:Gd nanocrystals, we circumvented the PL quenching and achieved the magnetic-fluorescent MWNTs. Moreover, the nanohybrids showed powerful T1 and T2-weighted magnetic resonance imaging (MRI) signal in water and could be used as MRI contrast agents. As a result, the nanohybrids can be expected to act as a promising multimodal MRI/optical imaging probe.
Keywords: Carbon nanotubes; Lanthanide doped nanoparticles; Magnetic-fluorescent nanohybrids; Layer-by-layer; Multimodal imaging
One-pot synthesis and surface modifications of organically modified silica (ORMOSIL) particles having multiple functional groups
by Chan Yoon Jung; Jung Soo Kim; Ha Young Kim; Jung Min Ha; Yong Hyun Kim; Sang Man Koo (pp. 67-73).
Display Omitted► ORMOSIL particles with multiple functional groups are prepared by one pot synthesis. ► Distribution of functional groups are demonstrated by chemical reactions with dyes. ► Surface reaction of ORMOSIL particles endows additional functionalities to particles. ► The reaction with inorganic materials produces metallic hybrid composite particles.Here we report a facile one-pot synthetic method for organically modified silica (ORMOSIL) particles having multiple functional groups and demonstrate the homogeneous distribution of functional groups in ORMOSIL particles by chemical reactions of each surface functional group with fluorescent dyes such as fluroescamine and rhodamine B isothiocyanate. Dye-tagged ORMOSIL particles having tri-functional groups are exhibited two fluorescent emission peaks at 475 (blue) and 570nm (red), indicating the positions of functional groups. The surface reaction of these functionalized ORMOSIL particles with various organic or inorganic materials not only endowed additional functionalities and physical properties, but also produced metallic hybrid composite particles. Chemical and physical properties of functionalized ORMOSIL particles were characterized by FT-IR, solid state13C and29Si NMR, thermogravimetric analysis (TGA), electron microscopy (SEM and TEM), and X-ray diffraction (XRD) analysis.
Keywords: Organically modified silica (ORMOSIL) particles; Surface modification; Dye-tagging; Hybrid composites
Fabrication and characterization of biocompatible nacre-like structures from α-zirconium hydrogen phosphate hydrate and chitosan
by Sajjad M. Waraich; Britta Hering; Zaklina Burghard; Joachim Bill; Peter Behrens; Henning Menzel (pp. 74-82).
Display Omitted► Preparation and characterization of composites with nacre-like hierarchical structure. ► Components with proven biocompatibility. ► Composites assembled employing the layer-by-layer deposition method. ► Systematic variation of concentration and pH. ► Influence on structural order and the mechanical properties studied.Composite materials with an ordered layered structure resembling that of nacre were fabricated by layer-by-layer assembly making use of presynthesized α-zirconium hydrogenphosphate hydrate (ZrP) platelets and chitosan. These two biocompatible materials were chosen in view of possible applications in the biomedical field, e.g., as bone or joint replacement implants. The effect of different concentrations of the inorganic ZrP platelets and the organic components (chitosan) on the composite assembly and structure was investigated. A high concentration of chitosan (0.1wt.%) resulted in a misalignment of the inorganic platelets, while at very low concentrations (0.001wt.%), the substrate was not fully covered by the polymer, again leading to misalignment. Also, the concentration of the α-ZrP platelets affected the composite assembly and structure. The number of dipping cycles was varied between 70 and 220, yielding a maximum thickness of approximately 6μm. The pH value of the chitosan solution was also varied to investigate its influence on the composite assembly. The mechanical properties of the composites were tested with a nanoindenter. For samples prepared with the same number of dipping cycles, higher values of Young’s modulus and hardness were obtained with improved alignment of the platelets in the samples. For samples prepared with 220 dipping cycles, a Young’s modulus of 2.6GPa and a hardness of 70MPa were observed. Important general relationships are recognized between the preparation parameters, the degree of order within the nacre-like films and the resulting mechanical properties.
Keywords: Layer-by-layer assembly; Nacre; Chitosan; Mechanical properties
Viscosity contribution of an arbitrary shape rigid aggregate to a dilute suspension
by Yogesh M. Harshe; Marco Lattuada (pp. 83-91).
Display Omitted► Generalized formulation for the estimation of viscosity contribution of arbitrary shape rigid body. ► Viscosity contribution of fractal clusters with a range of cluster morphologies and masses to a dilute suspension. ► Relation between viscosity contribution and cluster fractal dimension. ► Equivalent ellipsoid to represent complex fractal geometries. ► Study of linear viscoelasticity of fractal clusters.The study of rheological response of solid suspensions is essential in understanding the relationships governing their kinematics and dynamics. However the study is complicated mainly by the complex interplay between suspension rheology and hydrodynamic behavior of the suspended solids, which for most of the practically occurring situations have complex and arbitrary shapes, and exact equations accounting for their hydrodynamic contribution are not available. For this reason, using a recently developed methodology capable of computing the average rigid body resistance matrix of arbitrary shaped clusters made of uniform sized spheres, Brownian dynamic simulations under shear conditions are performed for clusters with different geometries with the objective of estimating their intrinsic viscosity. The population of clusters chosen encompassed a broad range of morphologies, such as fractals with a wide range of masses and fractal dimension values, dense clusters with spherical and spheroidal aspect ratios, similar to those produced during coagulation experiments of colloidal suspensions. It was found that fractal clusters with low fractal dimensions and spheroidal clusters have sufficient structural anisotropies to show deviations from Einstein’s relationship, and display a moderate shear thinning behavior, as well as a non-negligible linear viscoelasticity. On the other hand, clusters with high fractal dimensions tend to behave progressively more like spheres as their fractal dimension increases. We also found that the intrinsic viscosity of all clusters, independent of their morphology, can be quantitatively predicted by means of an equivalent ellipsoid model, in which clusters are modeled as ellipsoids with the same principal moments of inertia.
Keywords: Rheology; Dilute suspensions; Fractal aggregates; Intrinsic viscosity; Stokesian dynamics; Brownian dynamics; Grand resistance matrix; Rigid body; Viscoelasticity
Synthesis, characterization and magnetic properties of hollow microspheres with micro-mesoporous shells assembled from cobalt-based ferrocenyl coordination polymers
by Jia Huo; Li Wang; Elisabeth Irran; Haojie Yu; Liang Ma; Jingming Gao; Dengsen Fan; Wenbing Ding; Abid Muhammad Amin; Yulei Tai (pp. 92-100).
Hollow magnetic microspheres with porous shells are constructed with layered cobalt-based ferrocenyl coordination polymers, which exhibit micro-mesoporosity in their shells and spin-canted antiferromagnetism with weak ferromagnetic ordering below 52K.Display Omitted► Novel hollow magnetic microspheres are constructed with coordination polymers. ► Microspheres exhibit hierarchical porous structures. ► Microspheres show spin-canted antiferromagnetism with ferromagnetic ordering. ► Microspheres have the potential applications in drug delivery, catalysis, etc.Hollow magnetic microspheres with micro-mesoporous shells were constructed with layered cobalt-based ferrocenyl coordination polymers (Co-Fc-HCPS) through a one-step Ostwald ripening process. The diameters of microspheres and corresponding cavities were controlled in the range of several microns by tuning the reaction time and reactant concentration, which would attribute the microspheres with high loading, and enhanced mass diffusion and transfer efficiency. The high crystallinity of hollow microspheres allowed determination of the crystal structure of cobalt-based ferrocenyl coordination polymer, which crystallized in Brucite-type layered structure with the formula of Co4(OH)4(FcDC)2, (H2FcDC=1,1′-ferrocenedicarboxylic acid), by combination of powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), element analysis (EA), and Fourier transform infrared spectroscopy (FT-IR). N2 adsorption/desorption investigation revealed the existence of both mesopores around 3.81nm and micropores of ca. 1nm in the shells. The hollow microspheres exhibited spin-canted antiferromagnetism with weak ferromagnetic ordering below ∼52K, which showed a remanent magnetization (Mr) of 1.0 μB and a large coercive field (Hc) of 5 kOe at 7K.
Keywords: Hollow microspheres; Micro-mesoporosity; Magnetism; Ferrocenyl; Coordination polymers
Shape-directing role of cetyltrimethylammonium bromide in the preparation of silver nanoparticles
by Zaheer Khan; Shaeel Ahmed AL-Thabaiti; Abdullah Yousif Obaid; Ziya Ahmad Khan; Abdulrahman A.O. Al-Youbi (pp. 101-108).
Shape of the surface resonance Plasmon band of silver nanoparticle depends on the concentrations of cetyltrimethylammonium bromide.Display Omitted► Silver nanoparticles have been synthesized in water by using tyrosine. ► Pre-, post-, and dilution-micellar effects are responsible for the different morphology of silver nanoparticles. ► Absorbance of surface resonance plasmon band decreases with tyrosine concentrations. ► Size, shape, and anisotropy strongly depend on the adsorption of ions onto the different faces of particles.We report a simple chemical reduction method for the synthesis of different colored silver nanoparticles, AgNP, using tyrosine as a reducing agent. Effects of cetyltrimethylammonium bromide, CTAB, and tyrosine concentrations are analyzed by UV–visible measurements and scanning electron microscopy (SEM) to evaluate the mode of AgNP aggregation. The position and shape of the surface resonance plasmon absorption bands strongly depend on the reaction conditions, i.e., [CTAB], [tyrosine], and reaction time. Sub-, post-, and dilution-micellar effects are accountable for the fast and slow nucleation and growth processes. Spectrophotometric measurement also shows that the average size and the polydispersity of AgNP increase with [CTAB] in the solution. CTAB acted as a shape-directing agent.
Keywords: Shape directing; UV–visible spectrum; Tyrosine; Silver nanoparticles
Photoswitching in azobenzene self-assembled monolayers capped on zinc oxide: Nanodots vs nanorods
by Syed Mujtaba Shah; Cyril Martini; Jörg Ackermann; Frédéric Fages (pp. 109-114).
Display Omitted► ZnO nanodots and nanorods as scaffolds for organic inorganic hybrid materials. ► Functionalization of ZnO nanocrystals with a photochromic azobenzene ligand. ► We observe photoisomerization of azobenzenes grafted on the metal oxide surface. ► ZnO nanorods enable the formation of tightly packed azobenzene monolayers. ► Photoisomerization is less efficient on nanorods as compared to nanodots.We report the synthesis and spectroscopic characterization of nanohybrid structures consisting of an azobenzene compound grafted on the surface of zinc oxide nanoparticles. Characteristic bathochromic shifts indicate that the azobenzene photochromic molecules self-assemble onto the surface of the nanocrystals. The extent of packing is dependent on the shape of the nanoparticle. ZnO nanorods, with flat facets, enable a tighter organization of the molecules in the self-assembled monolayer than in the case of nanodots that display a more curvated shape. Consistently, the efficiency of photochromic switching of the self-assembled monolayer on ZnO nanoparticles is also shown to be strongly affected by nanoparticle shape.
Keywords: Nanomaterials; Azobenzene; Zinc oxide; Nanorods; Photoisomerization
Synthesis and characterization of TiO2@C core-shell nanowires and nanowalls via chemical vapor deposition for potential large-scale production
by Hao Liu; Yong Zhang; Ruying Li; Mei Cai; Xueliang Sun (pp. 115-119).
Display Omitted► TiO2@C core shell nanostructures were selectively synthesized by a CVD method. ► Morphology of the structures can be controlled by modulating the growth temperature. ► A growth mechanism was proposed based on a solid-state diffusion process.TiO2 nanowires and nanowalls core structures covered with carbon shell were selectively synthesized by a simple chemical vapor deposition (CVD) method using commercial titanium powder as the starting material. Morphology and structure of the products were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The core shell structure is composed of single crystalline rutile titanium dioxide wrapped by amorphous carbon shell. By adjusting the growth temperature, morphology of the products can be controlled from one-dimensional nanowires to two-dimensional nanowalls. While TiO2@C nanowires were a preferred structure at higher temperature, TiO2@C nanowalls dominated the final product at lower temperature. A growth mechanism was proposed based on the initial growth state of these nanostructures, in which solid-state diffusion of the elements involved in the reaction was assumed to play an essential role. The obtained TiO2@C core shell structures may find potential applications in various nanoscale realms such as optoelectronic, electronic and electrochemical nanodevices and the simple synthesis procedure promises large scale production and commercialization of the titanium oxide@carbon nanostructures.
Keywords: Chemical vapor deposition; Carbon covered TiO; 2; nanostructure
An efficient route to aqueous phase synthesis of nanocrystalline γ-Al2O3 with high porosity: From stable boehmite colloids to large pore mesoporous alumina
by Rudina Bleta; Pierre Alphonse; Lisa Pin; Marie Gressier; Marie-Joëlle Menu (pp. 120-128).
N2 adsorption–desorption isotherms and pore size distributions (inset) for mesoporous γ-Al2O3 samples annealed at 500°C. After addition of the copolymer F127, we show that the porosity of γ-Al2O3 can be enhanced by 400% and the average pore diameter can be expanded from 5nm to about 14nm.Display Omitted► Block copolymer directed synthesis of mesoporous γ-Al2O3. ► A strong increase of porosity occurs above the CMC of the copolymer. ► Pore size can be tailored by adjusting the EO/Al ratio or by adding swelling agents. ► Copolymer promotes the alignment of nanoparticles in a fibre-like morphology.In this paper we emphasise the important role of Pluronic F127 on the porosity of mesoporous alumina prepared from boehmite colloids. By focusing on the F127/boehmite interactions we show how the concepts of interface science may help to predict and improve the textural characteristics of mesoporous alumina. By varying the synthetic parameters, in particular the copolymer content, we show that the porosity of γ-Al2O3 can be enhanced by 400% and the average pore diameter can be expanded from 5 to 14nm. These results are discussed in terms of interactions between the Pluronic F127 and boehmite colloids, and are correlated to the critical micelle concentration (CMC) of the copolymer. The textural characteristics of the mesoporous alumina can be further improved either by introducing hydrocarbons in the preformed boehmite/copolymer sols or by concentrating the sols. In comparison with as-synthesised alumina, those prepared with F127 showed improved thermal stability. Furthermore, boehmite/copolymer sols were stable for all surfactant concentrations investigated and can give high quality coatings suitable for catalytic applications.
Keywords: Mesoporous γ-Al; 2; O; 3; Sol–gel; Boehmite colloids; Triblock copolymer; CMC
Effect of cosolvent organic molecules on the adsorption and structural properties of soft-templated ordered mesoporous alumina
by Stacy M. Grant; Mietek Jaroniec (pp. 129-134).
Display Omitted► Aromatic expanders affect the properties of mesoporous alumina differently than silica. ► Pore width was only slightly increased by 1,3,5-trimethylbenzene (TMB) and TPB. ► Ordered mesoporous aluminas (OMAs) are obtained at lower amounts of TMB and TPB. ► These additives greatly improve the surface area, pore volume and microporosity of OMA.Ordered mesoporous aluminas with high surface areas (up to 783m2/g), large pore volumes (up to 0.82cm3/g) and the presence of complementary micropores (up to 0.17cm3/g) are synthesized with Pluronic® F127 or P123 triblock copolymers in a one-pot synthesis of metal alkoxide, template and cosolvent molecules such as 1,3,5-trimethylbenzene or 1,3,5-triisopropylbenzene in an acidic ethanol solution at 15°C. Materials are characterized by nitrogen adsorption analysis, small-angle X-ray diffraction and transmission electron microscopy.
Keywords: Aluminum oxide; Triblock copolymer template; Expander molecules; 1,3,5-Trimethylbenzene; 1,3,5-Triisopropylbenzene; Evaporation induced self assembly
Dynamic control of gold nanoparticle morphology in a microchannel flow reactor by glucose reduction in aqueous sodium hydroxide solution
by Takayuki Ishizaka; Atsushi Ishigaki; Hajime Kawanami; Akira Suzuki; Toshishige M. Suzuki (pp. 135-138).
Display Omitted► Continuous and environmentally benign synthesis of gold nanoparticles in a micro channel reactor. ► Dynamic color and spectral change by control of NaOH addition rate. ► Novel star like morphology as quasi stable intermediates transformed into round shape together with the spectral change. ► The series of color change was responsible to the relative number of star particles.Continuous flow synthesis of gold nanoparticles was demonstrated using a microchannel reactor with glucose reduction in aqueous alkaline medium. Particle size, morphology, and visual/optical properties of the dispersion liquid were controlled dynamically by tuning of the rate of NaOH addition. Characteristic star-like nanoparticles formed spontaneously as a quasi-stable state, but they changed the morphology to round shape and showed spectral change over time.
Keywords: Gold nanoparticles; Star-like nanoparticles; Glucose reduction; Micro channel reactor
Uniform distribution of TiO2 nanocrystals on reduced graphene oxide sheets by the chelating ligands
by Thuy-Duong Nguyen-Phan; Viet Hung Pham; Hyukmin Kweon; Jin Suk Chung; Eui Jung Kim; Seung Hyun Hur; Eun Woo Shin (pp. 139-147).
Display Omitted► Reduced graphene oxide–TiO2 hybrids were synthesized by a hydrothermal method. ► Triethanolamine and acetylacetone were used as the chelating agents (CAs). ► The presence of CAs facilitated the regular spread of TiO2 onto exfoliated RGO sheets. ► Photocatalytic degradation of Rhodamine B was significantly enhanced.Reduced graphene oxide–TiO2 hybrids were successfully prepared by the hydrothermal approach using triethanolamine and acetylacetone as the chelating agents. Without any additive, large aggregated TiO2 clusters were randomly distributed dominantly at the edge and less on the basil plane of coagulated reduced graphene oxide (RGO) layers. The presence of chelating ligands remarkably facilitated the selective growth and regular spread of TiO2 nanocrystals onto individually exfoliated RGO sheet. Such sandwich-like structure with stronger coupling and chemical interaction resulted in the surface area increase, the rearrangement of energy level, the enhanced concentration of oxygen vacancies, leading to much higher adsorbability and photocatalytic degradation of Rhodamine B under both UV and visible irradiations. These RGO–TiO2 hybrid systems are potentially beneficial for widely practical applications in air/water purification, electronic devices, batteries, solar cells or supercapacitors.
Keywords: TiO; 2; Reduced graphene oxide; Hybrids; Chelating agent; Adsorption; Photocatalysis
Synthesis of uniform gold nanoparticles using non-pathogenic bio-control agent: Evolution of morphology from nano-spheres to triangular nanoprisms
by P. Mukherjee; Mainak Roy; B.P. Mandal; Sipra Choudhury; R. Tewari; A.K. Tyagi; S.P. Kale (pp. 148-152).
Display Omitted► Room temperature synthesis of Au-nps/nano Δ’s using non-pathogenic bio-control agent. ► Formation of exotic phases: fusion of nanospheres to form optically flat prisms. ► Detailed electron microscopic study on the evolution of morphology. ► Isolation of the desired phase by differential centrifugation.Green synthesis of gold nanospheres with uniform diameter and triangular nanoprisms with optically flat surface was carried out using a non-pathogenic bio-control agent Trichoderma asperellum for reduction of HAuCl4. Kinetics of the reaction was monitored by UV–Vis absorption spectroscopy. No additional capping/complexing agent was used for stabilizing the gold nanoparticles. Evolution of morphology from pseudospherical nanoparticles to triangular nanoprisms was studied by transmission electron microscopy (TEM). It revealed that three or more pseudospheres fused to form nanoprisms of different shapes and sizes. Slow rate of reduction of HAuCl4 by constituents of cell-free fungal extract was instrumental in producing such exotic morphologies. Isolation of gold nanotriangles from the reacting masses was achieved by differential centrifugation.
Keywords: Gold nanoparticle; Gold nanoprisms; Biological synthesis; Non-pathogenic; Exotic morphology
Manufacturing of agarose-based chromatographic adsorbents – Effect of ionic strength and cooling conditions on particle structure and mechanical strength
by Nicolas Ioannidis; James Bowen; Andrzej Pacek; Zhibing Zhang (pp. 153-160).
Display Omitted► The effect of processing conditions on the properties of agarose beads was examined. ► AFM and micromanipulation was used for characterization of the particles. ► Pore size and mechanical strength increase with ionic strength. ► The same trends are observed when particles are cooled slowly. ► The results can be used to prepare particles with improved properties.The effect of ionic strength of agarose solution and quenching temperature of the emulsion on the structure and mechanical strength of agarose-based chromatographic adsorbents was investigated. Solutions of agarose containing different amounts of NaCl were emulsified at elevated temperature in mineral oil using a high-shear mixer. The hot emulsion was quenched at different temperatures leading to the gelation of agarose and formation of soft particles. Analysis of Atomic Force Microscopy (AFM) images of particle surfaces shows that pore size of particles increases with ionic strength and/or high quenching temperature. Additionally it has been found that the compressive strength of particles measured by micromanipulation also increases with ionic strength of the emulsion and/or high quenching temperature but these two parameters have no significant effect on the resulting particle size and particle size distribution. Results from both characterization methods were compared with Sepharose 4B, a commercial agarose-based adsorbent. This is the first report examining the effect of ionic strength and cooling conditions on the microstructure of micron-sized agarose beads for bioseparation.
Keywords: Agarose beads; Microstructure; Pore size; Mechanical properties; AFM; Micromanipulation
Multicolored and white-light phosphors based on doped GdF3 nanoparticles and their potential bio-applications
by Farheen N. Sayed; V. Grover; V. Sudarsan; B.N. Pandey; A. Asthana; R.K. Vatsa; A.K. Tyagi (pp. 161-170).
Display Omitted► Synthesis of readily redispersible GdF3 nanoparticles by low-temperature route. ► Stabilization of hexagonal polytype of GdF3. ► White-light-emitting phosphor with CIE co-ordinates very close to broad daylight. ► Binding of nanoparticles to MCF-7 cells resulted in intense emission from cells.Rare-earth-doped gadolinium fluoride nanocrystals were synthesized by a single step synthesis employing ethylene glycol as solvent. Based on X-ray diffraction studies, stabilization of hexagonal modification of GdF3 has been inferred. The microscopic studies show formation of uniformly distributed nanocrystals (∼15nm). The nanoparticles are readily dispersible in water and show bright luminescence in colloidal solution. The luminescence properties have been investigated as a function of activator concentrations, and enhanced optical properties have been attributed to efficient energy transfer from the Gd3+ to the activator RE3+ ions, which has further been confirmed by steady-state and time-resolved optical studies. It has been demonstrated that on doping appropriate amount of activators in host GdF3, a novel white-light-emitting phosphor is obtained with CIE co-ordinates and correlated color temperature (CCT) very close to broad daylight. This can have promising applications as phosphor for white-light ultraviolet-light-emitting diodes (UV-LEDs). Our experiments showed efficient labeling of human breast carcinoma cells (MCF-7) by Tb3+-doped GdF3 nanoparticles. The fluorescence intensity was found to be dependent on the surface modifying/coating agent, and the results were validated using confocal microscopy in terms of localization of these functionalized nanoparticles.
Keywords: Nanofluoride; Luminescence; Phosphors; Gadolinium fluoride
Transparent polymeric hybrid film of ZnO nanoparticle quantum dots and PMMA with high luminescence and tunable emission color
by Kiyoshi Matsuyama; Kenji Mishima; Takafumi Kato; Keiichi Irie; Kenichi Mishima (pp. 171-177).
Display Omitted► ZnO nanoparticle QDs/PMMA composite is well dispersed in THF and shows high emissions. ► TPM acts as the stabilizer and promotes the compatibility between the ZnO nanoparticle QDs and the PMMA matrix. ► The hybrid film exhibited a high quantum yield and PL emission under ultraviolet excitation. ► PL emission has been successfully tuned from blue to yellow.ZnO nanoparticle quantum dots (QDs)/poly(methyl methacrylate) (PMMA) composites are synthesized by conventional radical polymerization in the presence of 3-(trimethoxysilyl)propylmethacrylate (TPM)-modified ZnO nanoparticle QDs. Although unmodified ZnO nanoparticle QDs were precipitated in tetrahydrofuran (THF) and show only weak emissions under UV irradiation, ZnO nanoparticle QDs/PMMA composite is well dispersed in THF and shows high emissions. TPM acts as the stabilizer and promotes the compatibility between the ZnO nanoparticle QDs and the PMMA matrix. After evaporation of THF from the ZnO nanoparticle QDs/PMMA composite solution, transparent polymeric hybrid films of ZnO nanoparticle QDs and PMMA are obtained. These polymeric hybrid films are characterized by photoluminescence (PL) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and thermogravimetric analysis. The hybrid film exhibited a high quantum yield and PL emission under ultraviolet excitation. PL emission has been successfully tuned from blue to yellow.
Keywords: ZnO quantum dot; ZnO colloid; Photoluminescence; Polymeric hybrid film; 3-(Trimethoxysilyl)propylmethacrylate; Poly(methyl methacrylate); Polymerization
Synthesis and characterization of Mn doped ZnS d-dots with controllable dual-color emissions
by Bohua Dong; Lixin Cao; Ge Su; Wei Liu (pp. 178-182).
The high-quality Mn doped ZnS d-dots exhibit tunable dual-color emissions, which can be well manipulated by controlling the Mn doped concentration.Display Omitted► Synthesis of Mn doped ZnS d-dots with controlled sizes and optical properties. ► The obtained d-dots demonstrate tunable dual-color (orange and blue) emissions. ► The color hue of the Mn doped ZnS d-dots can be tuned from blue to orange by controlling the Mn doping concentration. ► The Mn doped ZnS d-dots can be made to be water soluble by ligand exchange.High-quality Mn doped ZnS d-dots were successfully synthesized via an alternative route based on the solvothermal method using oleic acid as stabilizing agent. X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as photoluminescence (PL) spectra were employed to characterize the obtained samples. The as-obtained d-dots are highly crystalline and uniform sized, and they can be well dispersed in hexane to form stable and clear colloidal solution. The optical properties of the d-dots with different Mn doped concentration are investigated in detail. The Mn doped ZnS d-dots have two emission bands, including surface state emission (blue) and Mn emission (orange), which are both sensitivity to the Mn doped concentration. By varying the Mn doped concentration, the relative PL intensities of dual-color emissions can be well manipulated, showing their application in tunable color output. Furthermore, a subsequent ligand exchange has been introduced to give the d-dots hydrophilic surfaces, which are favorable for biological applications.
Keywords: Quantum dots; Luminescence; Mn doped ZnS; D-dots
Supercritical carbon dioxide swelling of fluorinated and hydrocarbon surfactant templates in mesoporous silica thin films
by Kaustav Ghosh; Hans-Joachim Lehmler; Stephen E. Rankin; Barbara L. Knutson (pp. 183-192).
Display Omitted► CO2 penetration in surfactant mesophase evaluated from CO2 based pore expansion of templated film. ► The structure of the fluorocarbon/hydrocarbon surfactant tail determines the pore expansion. ► Preferential CO2 solvation in fluorocarbon segments of the surfactant template is demonstrated. ► Dip-coating of thin films demonstrated on low energy fluorinated-modified substrate.The penetration of compressed CO2 in hydrocarbon and fluorocarbon regions of concentrated surfactant mesophases are interpreted from differences in the CO2-processed pore expansion of mesoporous silica thin films templated by three surfactants containing varying degrees of hydrocarbon and fluorocarbon functionality. Ordered silica thin films are synthesized for the first time using the 16-carbon (C16) partly fluorinated surfactant, 11,11,12,12,13,13,14,14,15,15,16,16,16-tridecafluorocetyl pyridinium bromide (HFCPB), as a templating agent. Silica films templated with surfactants containing a 8-carbon (C8) fluorocarbon tail (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl pyridinium chloride (HFOPC)) and a 16-carbon (C16) hydrocarbon tail (cetyl pyridinium bromide (CPB)) and HFCPB (C16) are processed in compressed CO2 (69–172bar, 25°C and 45°C) during synthesis. CO2 processing results in significant pore expansion for films templated with both fluorinated surfactants, while pore expansion is negligible for the hydrocarbon templated material suggesting that preferential CO2 penetration occurs in the ‘CO2-philic’ fluorocarbon segments of the surfactant template. The effect of substrate surface energy on the final uniformity of the dip-coated films is studied by varying the substrate from unmodified glass to a fluorocarbon-capped substrate. The ability to create dip-coated thin films on low surface energy substrates through favorable interaction of surfactant template tail with the substrate surface functional groups is demonstrated.
Keywords: Carbon-dioxide penetration; ‘CO; 2; -philic’ surfactants; Surfactant templated silica; Dip-coated films; Surfactant solution spreading
Influence of temperature on the colloidal stability of the F-DPPC and DPPC liposomes induced by lanthanum ions
by Paula Toimil; Rocío Daviña; Juan Sabín; Gerardo Prieto; Félix Sarmiento (pp. 193-198).
Display Omitted► Influence of ions La3+ on the colloidal stability of DPPC and F-DPPC liposomes. ► Dynamic light scattering and electrophoretic mobility was used to study the stability. ► The behavior of DPPC and F-DPPC liposomes was studied varying the temperature. ► At 25°C, the DPPC liposomes are more resistant to aggregation than F-DPPC liposomes. ► This difference disappears at 60°C, when both bilayers have the same conformation.The influence of La3+ on the colloidal stability of liposomes made up by two zwitterionic phospholipids, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-[16-fluoropalmitoyl-phosphatidylcholine (F-DPPC), in aqueous media has been investigated by dynamic light scattering and electrophoretic mobility. The critical aggregation concentration (c.a.c.) of La3+ for F-DPPC and DPPC liposomes were experimentally obtained, and the results were compared with theoretical predictions using the Derjaguin–Landau–Verwey–Overbeek theory. In order to evaluate the influence of the state of the bilayer on the stability of liposomes, all experiments were performed at temperatures below and above the chain-melting phase-transition temperature of lipids (transition temperature of lipids). Changes in the size of both types of liposomes and high values of polydispersity in the presence of La3+ showed that these ions induce aggregation of liposomes at 25°C and at 60°C.At 25°C, when the bilayer of F-DPPC liposomes is interdigited, DPPC liposomes are more resistant to aggregation than the liposomes formed with F-DPPC. However, this difference disappears at 60°C, when both bilayers have the same conformation.The experimental results also indicate that the c.a.c. is higher at 60°C than at 25°C for both types of liposomes. In fact, it has been observed by dynamic light scattering measurements that aggregation of liposomes at 25°C can be prevented by increasing the solution temperature for La3+ concentrations near to the c.a.c. Moreover, the behavior of these liposomes in the presence of the ion was studied at temperatures above and below the transition temperature of the phospholipids.
Keywords: Liposomes; DPPC; F-DPPC; Lanthanum; DLS; Electrophoretic mobility; Aggregation; Colloidal stability; DLVO
In situ synthesis of Pt/carbon nanofiber nanocomposites with enhanced electrocatalytic activity toward methanol oxidation
by Dawei Wang; Yang Liu; Jianshe Huang; Tianyan You (pp. 199-203).
Display Omitted► A facile in situ method to synthesis Pt nanoparticles on electrospun CNFs. ► Electrospun CNFs are used as catalysts support, which are cheap and easy to prepare. ► The Pt nanoparticles on CNFs present uniform size and good distribution. ► The as-prepared Pt/CNF nanocomposites exhibit high electrocatalytic activity.Pt/carbon nanofiber (Pt/CNF) nanocomposites were facilely synthesized by the reduction of hexachloroplatinic acid (H2PtCl6) using formic acid (HCOOH) in aqueous solution containing electrospun carbon nanofibers at room temperature. The obtained Pt/CNF nanocomposites were characterized by TEM and EDX. The Pt nanoparticles could in situ grow on the surface of CNFs with small particle size, high loading density, and uniform dispersion by adjusting the concentration of H2PtCl6 precursor. The electrocatalytic activities of the Pt/CNF nanocomposites were also studied. These Pt/CNF nanocomposites exhibited higher electrocatalytic activity toward methanol oxidation reaction compared with commercial E-TEK Pt/C catalyst. The results presented may offer a new approach to facilely synthesize direct methanol fuel cells (DMFCs) catalyst with enhanced electrocatalytic activity and low cost.
Keywords: Electrospun carbon nanofiber; Nanocomposites; Electrocatalytic activity; Methanol oxidation
Deposition of gold nanoparticles on β-FeOOH nanorods for detecting melamine in aqueous solution
by Jeffrey Yue; Xuchuan Jiang; Yusuf Valentino Kaneti; Aibing Yu (pp. 204-212).
Display Omitted► Controllable synthesis of Au/Pt@β-FeOOH nanocomposites without any linking mediates. ► Au@β-FeOOH nanostructure is very stable during phase transition into Fe3O4. ► Au@β-FeOOH nanocomposite shows high sensitivity toward melamine (<0.5ppm).This study demonstrates a facile but efficient approach to deposit metallic (gold) nanoparticles on β-FeOOH nanorods to obtain Au/β-FeOOH nanocomposites without the assistance of any polymers or surfactants at ambient conditions. In this method, a strong reducing agent (NaBH4) can be used to extensively produce Au nanoparticles, converting β-FeOOH into Fe3O4 and depositing gold particles onto magnetic Fe3O4 simultaneously. The microstructure, composition, and chemical properties of the obtained nanocomposites are characterized by various advanced techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–vis spectroscopy. Moreover, the Au/β-FeOOH nanocomposite can be used to detect trace melamine using UV spectrum in the ultraviolet wavelength range (190–260nm), in which the nanocomposites show a higher sensitivity toward melamine due to the promotion of symmetry-forbidden bands ( n→ π*) of melamine molecules and also avoid the disturbance of commercial products containing solid colloids or food colorings that distort visual spectrum during the detection of chemical sensing. The deposition mechanisms and their sensing detection toward melamine are discussed.
Keywords: Noble metals; Iron oxyhydroxide; Metal/iron oxide nanocomposites; Melamine
Pickering emulsions stabilized by surface-modified Fe3O4 nanoparticles
by Jun Zhou; Lijun Wang; Xiuying Qiao; Bernard P. Binks; Kang Sun (pp. 213-224).
Display Omitted► We modified Fe3O4 nanoparticles to increase their hydrophobicity. ► The stability of the resultant Pickering emulsions was investigated. ► Carboxylic acid-coated particles can only stabilize dodecane–water emulsions. ► Stability of emulsions decreases as alkyl group length and coating extent increase. ► Silane-coated particles can stabilize O/W emulsions with butyl butyrate or dodecane.Unmodified Fe3O4 nanoparticles do not stabilize Pickering emulsions of a polar oil like butyl butyrate. In order to obtain stable emulsions, the Fe3O4 nanoparticles were modified by either carboxylic acid (RCOOH) or silane coupling agents (RSi(OC2H5)3) to increase their hydrophobicity. The influence of such surface modification on the stability of the resultant Pickering emulsions was investigated in detail for both a non-polar oil (dodecane) and butyl butyrate in mixtures with water. The stability of dodecane-in-water emulsions in the presence of carboxylic acid-coated particles decreases as the length of the alkyl group (R) and the coating extent increase. However, such particles are incapable of stabilizing butyl butyrate-water emulsions even when the carboxylic acid length is decreased to two. However, the silane-coated Fe3O4 nanoparticles can stabilize butyl butyrate-in-water emulsions, and they also increase the stability of dodecane-in-water emulsions. Thermal gravimetric analysis indicates that the molar quantity of silane reagent is much higher than that of carboxylic acid on nanoparticle surfaces after modification, raising their hydrophobicity and enabling enhanced stability of the resultant polar oil–water emulsions.
Keywords: Pickering emulsion; Fe; 3; O; 4; Nanoparticles
Percolation-dominated superhydrophobicity and conductivity for nanocomposite coatings from the mixtures of a commercial aqueous silica sol and functionalized carbon nanotubes
by Mao Peng; Honglei Guo; Zhangjie Liao; Ji Qi; Zhi Zhou; Zhengping Fang; Lie Shen (pp. 225-233).
Display Omitted► We prepare superhydrophobic conductive coatings from aqueous silica sol and MWCNTs. ► MWCNTs are hydroxylated or physically functionalized by a polysoap. ► The coatings are prepared by air-spraying and are easy to repair. ► The superhydrophobicity and conductivity of the coatings are percolation dominated. ► The percolation threshold for superhydrophobicity is extremely low.Superhydrophobic conductive nanocomposite coatings are prepared for the first time from the simple mixture of a commercial aqueous silica sol and functionalized multiwalled carbon nanotubes (MWNTs) by air-spraying at ambient conditions followed by fluorosilane treatment. The relationship between MWNT content and the structure and properties of the nanocomposite coatings is investigated systematically. An ultra-low threshold (<5vol.%) for superhydrophobicity is observed, which suggests that MWNTs are superior to any other spherical fillers for the construction of superhydrophobic nanocomposite coatings. When the content of nanotubes is below the threshold, the surface roughness mainly caused by the silica nanoparticles is not enough for creating superhydrophobic surfaces. Only above the threshold, the multiscale hierarchical structure is enough for both high water contact angles (>165°) and extremely low sliding angles (<2°). The conductivity is also percolation dominated, while the threshold for conductivity is much higher than that for superhydrophobicity, which can be ascribed to the encapsulated structure and the agglomeration of nanotubes in the composite coatings during air-spraying. Moreover, the aqueous silica sols hold merits of great film-forming capability at relatively low calcination temperatures, and being free of organic solvents.
Keywords: Carbon nanotube; Silica sol; Superhydrophobicity; Conductivity; Percolation
Forming highly fluorescent near-infrared emitting PbS quantum dots in water using glutathione as surface-modifying molecule
by Dawei Deng; Junfei Xia; Jie Cao; Lingzhi Qu; Junmei Tian; Zhiyu Qian; Yueqing Gu; Zhongze Gu (pp. 234-240).
Display Omitted► We developed a new facile method for transferring oil-soluble PbS QDs into water with glutathione. ► The resulting water-soluble GSH-capped PbS QDs show strong NIR fluorescence (PL QY>30%). ► We revealed the influence of ligand exchange with five different types of thiol molecules. ► We explored the conditions of QD water solubilization, the stability, and cytotoxicity. ► The resultant water-soluble NIR-emitting PbS QDs are promising for the imaging of living animals.We present a new facile procedure for transferring oil-soluble oleic acid-capped NIR-emitting PbS quantum dots (QDs) into water, using hydrophilic thiol ligands as the surface-modifying agents of the primary capping molecules (oleic acid). The influence of exchange of the primary capping molecules with five different types of thiol molecules is investigated. The results show that highly fluorescent water-soluble PbS QDs are obtained using glutathione as a surface-modifying agent (photoluminescence quantum yield (PL QY), >30%); significantly less fluorescent water-soluble QDs were obtained usingl-cysteine (PL QY, ∼5%); with other three thiol molecules, PbS QDs lose almost completely their fluorescence in aqueous solution. This striking difference among the five thiol molecules may be attributed to the difference in the molecular structure. Next, we explored systematically the conditions of QD water solubilization, storage stability, photostability and cytotoxicity and tested further the resulting water-soluble PbS QDs for the imaging of living animals. The preliminary results from these studies illustrate that our synthesis procedure is very facile and that the as-prepared water-soluble PbS QDs are stable and low-cytotoxic and will be an important potential probe in the imaging of living animals due to free carboxyl and amino groups on the external surface of the QDs.
Keywords: Water transfer; PbS quantum dots; Glutathione; Near-infrared emitting; Biomedical imaging
Adsorption of cadmium(II) on humic acid coated titanium dioxide
by Qiqing Chen; Daqiang Yin; Shujiang Zhu; Xialin Hu (pp. 241-248).
Display Omitted► Humic acid (HA) coated titanium dioxide (HA–TiO2) was prepared and well characterized. ► HA coating on nano-TiO2 significantly enhanced the adsorption of Cd(II). ► The adsorption mechanisms of Cd(II) onto HA–TiO2 were interpreted with X-ray photoelectron spectroscopy(XPS).The rapid increase in nanotechnology has led to growing concerns on environmental effects and health risks of nanoparticles (NPs). Many studies investigated the adsorption of toxic pollutants on NPs; however, the interaction between heavy metals and natural organic matter (NOM) coated metal oxide NPs was scarcely studied. In this study, using humic acid (HA) as model NOM, the adsorption of Cd(II) on humic acid coated titanium dioxide (HA–TiO2) NPs was investigated. Solution parameters such as pH and salinity were investigated to exploit the mechanisms. Our results demonstrated that the adsorption isotherms of Cd(II) to both TiO2 and HA–TiO2 complied well with Freundlich model.q e values increased with pH increase, mainly due to electrostatic attraction, whereasq e values increased initially and then decreased at 100mmolL−1 with salinity increase, mainly due to complexation and electrostatic effects. It is noteworthy that an overall trend of higher Cd(II) adsorption was observed on HA–TiO2 compared to that on TiO2, implying that HA coating might modify bioavailability of heavy metals in aquatic environment. The possible adsorption mechanisms in views of electrostatic interactions and covalent effects were interpreted, and the X-ray photoelectron spectroscopy (XPS) results also verified the possible mechanisms.
Keywords: Nanoparticles; Titanium dioxide; Humic acid; Cadmium; Interaction mechanisms
Fabrication of hierarchical microparticles by depositing the in situ synthesized surface nanoparticles on microspheres during the seed emulsion polymerization
by Da Wang; Rui Yan; Xicai Liu; Yang Su; Minchao Zhang; Wangqing Zhang (pp. 249-256).
Display Omitted► General strategy for the synthesis of hierarchical microparticles is proposed. ► Monomer miniemulsion is added during the seed emulsion polymerization. ► Hierarchical microparticles containing 20–36nm surface nanoparticles are synthesized. ► Advantages including well-control and convenience are demonstrated.A general strategy for the synthesis of polymeric hierarchical microparticles containing surface nanoparticles through modified seed emulsion polymerization is proposed. This modified seed emulsion polymerization has a character that suitable amount of monomer miniemulsion is added during the polymerization. The in situ synthesized surface nanoparticles which are resulted from the monomer miniemulsion as well as the shell-forming polymer coagulate on the seed particles and therefore hierarchical microparticles are fabricated. Various polymeric hierarchical microparticles containing 20–36nm poly(styrene- co-acrylamide), poly(styrene- co-acrylic acid), and polystyrene surface nanoparticles are synthesized following the proposed method. The advantages in the present synthesis including both the well controls in the size, the composition, and the number of the surface nanoparticles and the convenience are demonstrated. The proposed strategy is anticipated to be a general method to fabricate hierarchical microparticles and is believed to have promising application in particle surface modification.
Keywords: Emulsion polymerization; Hierarchical particles; Miniemulsion; Nanoparticles; Surface modification
Selective surface reactions for Janus ORMOSIL particles with multiple functional groups using an ordered monolayer film at liquid–liquid interface
by Chan Yoon Jung; Jung Soo Kim; Hae Sung Kim; Jung Min Ha; Sun Taek Kim; Hyung Jun Lim; Sang Man Koo (pp. 257-263).
Display Omitted► Monodispersed Janus ORMOSIL particles with multiple functional groups were prepared. ► A monolayer film was obtained by self-assembly of ORMOSIL particles at interface. ► Photopolymerization of a monolayer yield a rigid film to perform further reaction. ► Selective surface reaction of a rigid film produced Janus ORMOSIL particles.Monodispersed, submicron-sized Janus ORMOSIL particles with multiple functional groups were prepared by the selective surface reaction of a monolayer film formed at a hexane–water interface. A well-ordered monolayer film was obtained by self-assembly of ORMOSIL particles with multiple functional groups at hexane–water interface. The photopolymerization of an ordered monolayer containing ORMOSIL particles yields a rigid film strong enough to maintain its integrity for transfer and further chemical reaction. The chemical reaction of this ordered film with organic and inorganic functional groups produced Janus ORMOSIL particles with multiple functional groups. The morphologies, structures, and chemical compositions of monolayer films and Janus ORMOSIL particles were characterized by FT-IR, solid state NMR, X-ray diffraction (XRD), optical microscopy (OM), electron microscopies (SEM and TEM), and confocal laser scanning microscopy.
Keywords: Janus ORMOSIL particles; Surface reaction; Monolayer film; Self-assembly; Photopolymerization
Effective adsorption of sodium dodecylsulfate (SDS) by hydrocalumite (CaAl-LDH-Cl) induced by self-dissolution and re-precipitation mechanism
by Ping Zhang; Guangren Qian; Zhi Ping Xu; Huisheng Shi; Xiuxiu Ruan; Jing Yang; Ray L. Frost (pp. 264-271).
Display Omitted► We prepared the CaAl-LDH-Cl materials synthesized by hydrating freshly prepared tricalcium aluminate (C3A) in CaCl2 solution. ► The modified materials were characterized by XRD, FTIR, XPS, and SEM. ► We showed the distances and morphologies of resulting materials reacted with different concentration of SDS, respectively. ► We concluded the mechanism of the CaAl-LDH-Cl reacted with different concentration of SDS.Hydrocalumite (CaAl-LDH-Cl) was synthesized through a rehydration method involving a freshly prepared tricalcium aluminate (C3A) with CaCl2 solution. To understand the intercalation behavior of sodium dodecylsulfate (SDS) with CaAl-LDH-Cl, X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-atomic emission spectrometer (ICP), and elemental analysis have been undertaken. The sorption isotherms with SDS reveal that the maximum sorption amount of SDS by CaAl-LDH-Cl could reach 3.67mmolg−1. The results revealed that CaAl-LDH-Cl holds a self-dissolution property, about 20–30% of which is dissolved. And the dissolved Ca2+ and Al3+ ions are combined with SDS to form CaAl-SDS or Ca-SDS precipitation. It has been highlighted that the composition of resulting products is strongly dependent upon the SDS concentration. With increasing SDS concentrations, the main resulting product changes from CaAl-SDS to Ca-SDS, and the value of interlayer spacing increased to 3.27nm.
Keywords: Hydrocalumite; Sodium dodecylsulfate; Mechanism; Self-dissolution; Precipitation; X-ray photoelectron spectroscopy (XPS)
Micellar evolution in mixed nonionic/anionic surfactant systems
by Shaohua Lu; Jun Wu; Ponisseril Somasundaran (pp. 272-279).
Display Omitted► Micellar evolution quantitatively investigated in surfactant mixtures. ► Synergistic interaction revealed in anionic/nonionic surfactant mixture. ► Coexistence of two types of micellar species identified for the first time.Surfactant mixtures are widely used in industrial applications due to their favorable synergistic interactions. For instance, anionic and nonionic mixtures are often employed in detergent, personal care, and enhanced oil recovery. It is useful to understand micellization behaviors of such mixtures, as they are important for formulation optimizations. A range of techniques including surface tensiometry, fluorescence spectroscopy, ultrafiltration, and analytical ultracentrifugation (AUC), were employed in this work to obtain information on the micellization behaviors of the mixed n-dodecyl-β-d-maltoside (DM)/sodium dodecyl sulfonate (SDSN) system. The interaction parameter, monomer concentration, and micellar size and shape distribution were obtained for this mixed surfactant system as a function of total surfactant concentration as well as mixing ratio to achieve a full understanding of their aggregation behaviors. The coexistence of two types of micelles was identified in this mixed anionic/nonionic surfactant system for the first time. A model is proposed to explain such coexistence based on the surface activities and the interactions between the two types of surfactants. These findings are useful for optimizing the composition of mixed surfactant systems and enhancing the synergetic efficiency of the system to achieve more effective and economical formulations.
Keywords: Surfactant mixture; Micellization; Surface tension; Fluorescence; Analytical ultracentrifugation
Self-assembly in surfactant-based liquid mixtures: Octanoic acid/Bis(2-ethylhexyl)amine systems
by Pietro Calandra; Vincenzo Turco Liveri; Pietro Riello; Isidora Freris; Andrea Mandanici (pp. 280-285).
Display Omitted► Evolution and control of properties in Bis(2-ethylhexyl)amine plus octanoic acid mixtures. ► Proton transfer from the octanoic acid to Bis(2-ethylhexyl)amine triggers self-assembly. ► More than seven orders of magnitude enhancement in conductivity in the mixtures.The physico-chemical properties of Bis(2-ethylhexyl)amine (BEEA) plus octanoic acid (OA) mixtures have been investigated by IR, SAXS, WAXS, viscosimetry, and AC complex impedance spectroscopy in the whole composition range. Mainly driven by proton transfer from the acidic OA to the basic BEEA, the formation of stoichiometrically well-defined adducts takes place in the mixtures. This causes the slowing down of molecular dynamics and the increase in charge carrier number density. Interestingly, while the pure components possess no significant conductivity (about 10−12Scm−1 at 25°C), their mixtures show a composition-dependent enhanced conductivity (up to about 10−5Scm−1), i.e., more than seven orders of magnitude higher than that of the pure components. The comparison of the composition dependence of viscosity, direct-current conductivity, and static permittivity indicates the concurrence of contributions of different adducts and that the dynamics controlling molecular reorientation and momentum and charge transfer, even if ultimately related to the proton transfer from OA to BEEA, are different. The results can be used not only to design novel materials for application purposes, but also to shed more light on the principles regulating molecular self-assembly in surfactant-based liquid systems.
Keywords: Bis(2-ethylhexyl)amine; Octanoic acid; Liquid mixtures; Conducting materials; Self-assembly
Interactions between β-cyclodextrin and an amino acid-based anionic gemini surfactant derived from cysteine
by Célia M.C. Faustino; António R.T. Calado; Luís Garcia-Rio (pp. 286-292).
Display Omitted► Anionic gemini surfactant derived from the amino acid cysteine forms a 1:1 inclusion complex with β-cyclodextrin. ► The binding constant is in the order of 102dm3mol−1, typical of a weakly bound β-CD–surfactant complex. ► Increasing β-CD concentration shifts the surfactant apparent critical micelle concentration to higher values.The interaction between β-cyclodextrin ( β-CD) and an amino acid-based anionic gemini surfactant derived from cysteine (C8Cys)2 was studied by three independent techniques: electrical conductivity, UV–Vis spectral displacement technique using phenolphthalein as probe, and1H NMR spectroscopy. The data obtained indicated the formation of a 1:1 inclusion complex between β-CD and the gemini surfactant studied and allowed for the determination of the binding constant, K1, by considering this stoichiometry. Electrical conductivity, spectral displacement technique, and NMR chemical shift measurements, obtained for aqueous β-CD–surfactant systems, yielded consistent K1 values in the order of 102dm3mol−1, typical of a weakly bound β-CD–surfactant complex. The influence of the presence of the inclusion complex on the micellization process of the gemini surfactant has also been studied and the apparent critical micelle concentration (cmc∗) has been obtained. Increasing β-CD concentration was found to shift the cmc∗ to higher values, as complexed surfactant monomers are not available to form micelles and aggregation takes place only when all β-CD cavities are occupied.
Keywords: Amino acids; Complexation constant; Cyclodextrins; Cysteine; Gemini surfactants; Inclusion complexes
Headgroup effects on the krafft temperatures and self-assembly of ω-hydroxy and ω-carboxy hexadecyl quaternary ammonium bromide bolaform amphiphiles: Micelles versus molecular clusters?
by Simon J. Holder; Bruntha C. Sriskantha; Stephen A. Bagshaw; Ian J. Bruce (pp. 293-304).
Display Omitted► Eight asymmetric bolaform amphiphiles with different polar end-groups have been synthesized. ► All of the amphiphiles dissolved and aggregated in water above a given temperature. ► Aggregation temperature was dependent upon molecular structure and pH. ► The aggregates for the alcohol ammonium amphiphiles formed small classical micellar structures. ► The carboxylic acid ammonium amphiphiles formed larger and looser molecular clusters.Eight bolaform amphiphiles were synthesised and characterised; 4 α,ω-hydroxy-alkane trialkyl (and pyridyl) ammonium bromides and 4 α,ω-carboxy-alkane trialkyl (and pyridyl) ammonium bromides where the alkyl groups were methyl, ethyl and propyl. Four of these represented new compounds. Overall the Krafft temperatures (T K) of the eight amphiphiles were high, with 6 of the eight possessingTK s greater than 45°C. Thus most of the amphiphiles could only expect to find applications at raised temperatures limiting their potential utility. However in addition to the previously reported α,ω-hydroxy-hexadecyl triethylammonium bromide (2b) with aT K of 19.1°C, another amphiphile, α,ω-carboxy-hexadecyl tripropylammonium bromide (2c) has been identified with aT K near ambient temperatures (T K of 22.1°C). This provides an acid functional ammonium bolaform amphiphile that micellises at ambient temperatures to complement the hydroxyl derivative. A correlation betweenT K and the product of the enthalpies andTm s of the compounds was observed for 7 of the eight compounds. No correlation between the amphiphile critical micelle concentrations (cmc) andTK s was observed confirming previous reports thatT K values are predominantly determined by crystalline stability rather than solubility. Considerable differences were observed between the various amphiphileTK s at different pHs but no clear trend was apparent for the various compounds (despite the degree to which the compounds’ carboxylic acid and hydroxyl functionalities were likely to be ionised). The cmcs for the amphiphiles were an order of magnitude larger than those for analogous mono-ammonium amphiphiles with little difference in between the hydroxyl- and carboxy-functionalised compounds. The aggregation numbers ( Nagg) obtained for all compounds were very low ( Nagg<7) and the apparent micellar diameters for the hydroxyl-bolaforms were in the range 1.0–1.4nm whereas those for the carboxy-compounds were in the range 2.1–2.4nm. These results strongly suggest a difference in the packing of the two sets of amphiphiles with loose low density aggregates or ‘molecular clusters’ for the carboxy compounds and denser classical micellar type aggregates for the hydroxyl-compounds. In both cases however the sizes and the low aggregation numbers point suggest that these aggregates are more characteristic of the pre-micellar aggregates observed for many amphiphiles but in particular gemini surfactants.
Keywords: Micelle; Aggregate; Pre-micellar; Ammonium; Bolaform; Amphiphile; Self-assembly; Dynamic light scattering; Krafft temperature; Aggregation number; Critical micelle concentration
Aggregation and adsorption of sodium dioctylsulfosuccinate in aqueous ammonium chloride solution: Role of mixed counterions
by J. Dey; U. Thapa; K. Ismail (pp. 305-310).
Sodium and ammonium mixed counterions produce synergism in the critical micelle concentration.Display Omitted► The binding of counterions to sodium dioctylsulfosuccinate micelle has been studied. ► Binding of sodium and ammonium mixed counterions is similar to that of sodium ion. ► Synergism in the critical micelle concentration occurs due to mixed counterions. ► An equation for the surface excess in presence of mixed counterions is derived.The critical micelle concentration (cmc) of sodium dioctylsulfosuccinate (AOT) was determined at 25°C from surface tension and fluorescence methods in aqueous NH4Cl solution for assessing the influence of mixed counterions on the special counterion binding behavior (SCB) of AOT. The SCB of AOT refers to a sudden twofold increase in the value of the counterion binding constant ( β) in aqueous medium when the concentration ( c*) of the added 1:1 sodium salt is about 0.015molkg−1, and it has been tested so far for sodium ion only. In the presence of sodium and ammonium mixed counterions also the SCB of AOT exist, but with lower c* (0.009molkg−1 NH4Cl). Synergism in the cmc occurs due to mixed counterions. In the case of inorganic counterions, unlike the case with organic counterions, the cmc is dependent on the total counterion concentration in solution and negligibly on the specific type of counterion. Na+ andNH4+ bind almost equally to the micelle in the region of low β (below c*), but in the region of high β (above c*)NH4+ binds predominantly. It has been shown that the theoretical expression for the surface excess of ionic surfactant+electrolyte system containing a single counterion can also be used to evaluate the surface excess in the presence of mixed counterions if the two counterions are considered to undergo Henry-type adsorption at the air–solution interface.
Keywords: AOT; Critical micelle concentration; Counterion binding constant; Mixed counterions; Synergism; Surface excess
Production and characterization of biosurfactant from marine Streptomyces species B3
by Abhijit Khopade; Biao Ren; Xiang-Yang Liu; Kakasaheb Mahadik; Lixin Zhang; Chandrakant Kokare (pp. 311-318).
Display Omitted► The isolated marine Streptomyces species B3 was potential source for biosurfactant production. ► The maximum biosurfactant production was observed with sucrose and yeast extract. ► Biosurfactant reduced surface tension up to 29mN/m, and the critical micelle concentration was 110mg/l. ► The biosurfactant consist of 58, 33, and 8% w/w lipid, carbohydrate, and protein respectively. ► Biosurfactant was highly effective over wide range of temperature, pH, and salt concentration.The present study demonstrates the production and properties of a biosurfactant isolated from marine Streptomyces species B3. The production of the biosurfactant was found to be higher in medium containing sucrose and lower in the medium containing glycerol. Yeast extract was the best nitrogen source for the production of the biosurfactant. The isolated biosurfactant reduced the surface tension of water to 29mN/m. The purified biosurfactant was shown critical micelle concentrations of 110mg/l. The emulsifying activity and stability of the biosurfactant was investigated at different salinities, pH, and temperature. The biosurfactant was effective at very low concentrations over a wide range of temperature, pH, and salt concentration. The purified biosurfactant was shown strong antimicrobial activity. The biosurfactant was produced from the marine Streptomyces sp. using non-hydrocarbon substrates such as sucrose that was readily available and not required extensive purification procedure. Streptomyces species B3 can be used for microbially enhanced oil recovery process.
Keywords: Biosurfactant; Streptomyces; Surface tension; Stability; Critical micelle concentration; Antimicrobial activity
Self-organization at the interface and in aqueous solution of a cationic gemini surfactant from the dioctyl ester of cystine
by S. Angayarkanny; R. Vijay; Geetha Baskar; A.B. Mandal (pp. 319-326).
Display Omitted► Dioctyl ester of cystine hydrochloride (DOEC) forms stable viscoelastic films at the air–water interface. ► CMC is about one order lower than the equivalent anionic surfactant from cystine. ► The molecular cross-sectional area at the interface was measured as 0.70±0.01nm2molecule−1. ► DOEC exhibits a tilted conformation at the interface, and the large packing parameter P of 0.58 suggests the formation of elongated micelles. ► DOEC favors one-dimensional growth to form fibril like structures.The cationic surfactant, dioctyl ester of cystine hydrochloride (DOEC), was characterized for interfacial adsorption and aggregation behavior in water. The cmc of DOEC was measured as 1.42±0.27×10−5moldm−3 using the techniques of tensiometry, conductivity and fluorimetry. From specific conductivity measurements, the degree of dissociation ( α) of the amine hydrochloride was measured as 0.612. The standard free energy change of micellization(ΔGm°) and adsorption(ΔGa°) were calculated to be −25.07 and −44.37kJmol−1, respectively. The aggregated structures provide non-polar microdomains as inferred from the I3/ I1 emission intensity ratio of 1.05 of pyrene fluoroprobe and also a blue shift of fluorescence emission wave length ( λemi.) maximum down to 470nm with enhanced intensity of ANS probe in micellar solutions. From Langmuir film balance experiments, it is shown that DOEC forms stable viscoelastic films at the interface with A0 at 0.69nm2molecule−1 that agree with the result from surface tension measurements. Molecular modeling suggests the tilted orientation of DOEC at the interface. A large packing parameter ( P) of 0.58 and the fibril structures as observed from microscopy studies demonstrate that DOEC favors one-dimensional growth to form elongated micelles.
Keywords: Gemini surfactants; Cystine; Langmuir film balance; Adsorption isotherms; Interfacial characteristics; Fluroprobes
Self-assembling systems based on amphiphilic alkyltriphenylphosphonium bromides: Elucidation of the role of head group
by Gulnara A. Gainanova; Guzalia I. Vagapova; Victor V. Syakaev; Alsu R. Ibragimova; Farida G. Valeeva; Elena V. Tudriy; Irina V. Galkina; Olga N. Kataeva; Lucia Ya. Zakharova; Shamil K. Latypov; Alexander I. Konovalov (pp. 327-336).
Display Omitted► Micellization of surfactants with phosphonium and ammonium head group is compared. ► Solubilization and micellization capacity monotonously change with alkyl chain length. ► Surface tension isotherms and counterion binding differ for low and high homologues. ► Krafft temperatures for phosphonium series are lower compared to ammonium series. ► Solubilization capacity of phosphonium series is higher compared to that of ammonium series.A systematic study of the aggregation behavior of alkyltriphenylphosphonium bromides (TPPB- n; n=8, 10, 12, 14, 16, 18; here n is the number of carbon atoms in alkyl groups) in aqueous solutions has been carried out and compared with trimethyl ammonium bromides (TMAB- n). Critical micelle concentrations (cmcs) of TPPB- n and TMAB- n decrease with the number of carbon atoms with the slope parameter of ca.0.3. The low cmcs and effective solubilization power toward Orange OT indicate high micellization capacity of phosphonium surfactants. The low counterion binding parameter β is revealed for TPPB-10 and TPPB-12, while high counterion binding of ⩾80% is observed for high TPPB- n homologs. Values of the surface potential ψ calculated on the basis of p Ka shifts of p-nitrophenols is similar for both series and monotonously increase with alkyl chain length. Several points indicate non-monotonic changes within TPPB- n series. There are peculiarities of the tensiometry and solubilization plots for high homologs and above mentioned increases in counterion binding on transiting from low to high molecular weight surfactants. Differences in aggregation behavior between TPPB and TMAB series and between low and high homologs can be due to the specific structural character of the TPP+ cation, which is supported by X-ray data.
Keywords: Alkyltriphenylphosphonium bromides; Solution; Aggregation; Solubilization
Microemulsion synthesis and electrocatalytic properties of carbon-supported Pd–Co–Au alloy nanoparticles
by Ch. Venkateswara Rao; B. Viswanathan (pp. 337-341).
Display Omitted► Pd–Co–Au/C nanocatalysts are prepared by microemulsion technique. ► Similar redox behavior of Pd–Co–Au/C catalysts with Pt is evident. ► Pd–Co–Au/C exhibited high ORR activity compared to Pd/C. ► The role of alloying elements on the enhanced activity of Pd is studied.Carbon-supported Pd and Pd–Co–Au alloy electrocatalysts are prepared by water-in-oil microemulsion technique using water as aqueous phase, non-ionic Triton-X-100 as surfactant, and cyclohexane as oil phase. The materials are characterized using XRD, TEM, and EDX. Face-centered cubic structure of Pd and presence of respective elements with controllable composition is evident from the analysis of XRD and EDX. The role of alloying elements on the redox behavior as well as catalytic activity of Pd is studied by cyclic voltammetry and ultraviolet photoelectron spectroscopy. Electrochemical measurements performed by rotating disk electrode voltammetry indicate the good ORR activity of Pd–Co–Au/C compared to Pd/C.
Keywords: Pd–Co–Au alloy; Oxygen reduction; Water-in-oil microemulsion; Cyclic voltammetry
Synthesis and electrocatalytic activity of Au/Pt bimetallic nanodendrites for ethanol oxidation in alkaline medium
by Xinyi Han; Dawei Wang; Dong Liu; Jianshe Huang; Tianyan You (pp. 342-347).
Display Omitted► Bimetallic Au/Pt nanodendrites were successfully prepared by seeded growth method. ► Pt/Au catalysts show high activity for ethanol oxidation in alkaline condition. ► The finding will be avail to develop advanced catalysts in direct ethanol fuel cell. ► First report about Pt/Au nanostructures as catalysts for ethanol electro-oxidation.Gold/Platinum (Au/Pt) bimetallic nanodendrites were successfully synthesized through seeded growth method using preformed Au nanodendrites as seeds and ascorbic acid as reductant. Cyclic voltammograms (CVs) of a series of Au/Pt nanodendrites modified electrodes in 1M KOH solution containing 1M ethanol showed that the electrocatalyst with a molar ratio (Au:Pt) of 3 exhibited the highest peak current density and the lowest onset potential. The peak current density of ethanol electro-oxidation on the Au3Pt1 nanodendrites modified glassy carbon electrode (Au3Pt1 electrode) is about 16, 12.5, and 4.5 times higher than those on the polycrystalline Pt electrode, polycrystalline Au electrode, and Au nanodendrites modified glassy carbon electrode (Au dendrites electrode), respectively. The oxidation peak potential of ethanol electro-oxidation on the Au3Pt1 electrode is about 299 and 276mV lower than those on the polycrystalline Au electrode and Au dendrites electrode, respectively. These results demonstrated that the Au/Pt bimetallic nanodendrites may find potential application in alkaline direct ethanol fuel cells (ADEFCs).
Keywords: Au/Pt bimetallic nanodendrites; Ethanol electro-oxidation; Alkaline direct ethanol fuel cells
Modeling carbon dioxide adsorption on polyethylenimine-functionalized TUD-1 mesoporous silica
by Nicola Gargiulo; Francesco Pepe; Domenico Caputo (pp. 348-354).
Display Omitted► Polyethylenimine-loaded mesoporous silica is synthesized for CO2 adsorption. ► CO2 adsorption isotherms at different temperatures are collected. ► CO2 adsorption isotherms are modeled by means of the Langmuir equation. ► A good fit between model curves and experimental data is pointed out. ► Isosteric heat of CO2 adsorption versus adsorbent fractional coverage is estimated.Samples of porous, foam-like TUD (Technische Universität Delft)-1 mesoporous silica were functionalized with polyethylenimine and were used as a substrate for CO2 adsorption. Produced solids were characterized by means of electron microscopy, thermogravimetric analysis, and N2 adsorption/desorption at 77K, in order to prove that polymer chains efficiently filled the pores of functionalized samples. CO2 adsorption isotherms on polyethylenimine-containing TUD-1 were evaluated at T=298, 313, 328, and 348K for pressures up to 100kPa by means of a volumetric technique. The CO2 adsorption capacity proved to be significantly dependent on temperature, with the highest capacity encountered at T=348K. The experimental data for CO2 adsorption were satisfactorily described by means of the Langmuir isotherm, and the dependence of the isosteric heat on the fractional coverage of the adsorbent was evaluated by means of the van’t Hoff equation, showing values in the order of 80kJ/mol for a fractional coverage of about 50%.
Keywords: Mesoporous silica; Polyethylenimine; Carbon dioxide; Adsorption; Langmuir isotherm; Isosteric heat
Synthesis and properties of bisphenol A molecular imprinted particle for selective recognition of BPA from water
by Yueming Ren; Weiqing Ma; Jun Ma; Qing Wen; Jun Wang; Fangbo Zhao (pp. 355-361).
Display Omitted► BPA-MIP by the surface molecular imprinting technique with a sol–gel process. ► DTPA as a functional monomer and TEOS as a cross-linker. ► The saturate binding capacity of BPA-MIP is 30.26μmolg−1. ► BPA-MIP shows an efficient selectivity toward BPA in water phase.Molecularly imprinted particle for bisphenol A (BPA-MIP) was prepared using the surface molecular imprinting technique with a sol–gel process on the surface of silica nanoparticles. The dosages of diethylenetriaminepentaacetic acid (DTPA) as a functional monomer and teraethyl orthosilicate (TEOS) as a cross-linker were optimized, respectively. The prepared BPA-MIP was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Fourier transform infrared spectrometer (FTIR), thermogravimetric analysis (TGA), and a standard Brunauer–Emett–Teller (BET) analysis. Moreover, the proper binding and selective recognition ability were also investigated by a single batch binding experiment. The equilibrium data fitted well to the pseudo-second-order kinetic and the Langmuir model for BPA binding onto BPA-MIP, respectively. The saturate binding capacity of BPA-MIP was found to be 30.26μmolg−1, which was three times higher than that of BPA non-molecular imprinted particle (BPA-NIP). The satisfactory results demonstrated that the obtained BPA-MIP showed an appreciable binding specificity toward BPA than similar structural compounds in water phase. The BPA-MIP could serve as an efficient selective material for determining or removing BPA from water environment.
Keywords: Surface molecular imprinting; BPA; Sol–gel; Equilibrium binding; Selectivity recognition
Removal of methylated arsenic using a nanostructured zirconia-based sorbent: Process performance and adsorption chemistry
by Yu-Ming Zheng; Ling Yu; J. Paul Chen (pp. 362-369).
Display Omitted► A zirconia-based sorbent is efficient for methylated arsenic removal from water. ► The maximum adsorption capacity for monomethylarsonic acid (MMA) is 1.43mmol/g. ► The adsorption of MMA by the nanostructured sorbent is highly pH-dependent. ► Pseudo-first order and Langmuir models descript the kinetics and isotherm well. ► From spectroscopic analysis, an anion exchange adsorption mechanism is proposed.A readily prepared nanostructured zirconia-based sorbent was developed and demonstrated to be effective on adsorption of monomethylarsonic acid (MMA) from water with a capacity of 1.43mmolMMA/gsorbent, which is much higher than that of sorbents reported. It was found that the MMA uptake is highly pH-dependent. Better adsorption is obtained at lower pH, and the optimal pH is from 2.5 to 3.5. Most of the MMA uptake occurs rapidly in the first 48h, followed by a relatively slow process. The adsorption kinetics and isotherm can be well described by pseudo-first order rate model and Langmuir equation, respectively. The temperature does not great influence on the adsorption isotherm. The MMA adsorption is independent on background electrolyte concentration, which implies the MMA forms inner-sphere complexes on the sorbent. The presence of humic acid does not pose noticeable effect on the adsorption. The coexistingHCO3- or F− obviously hinders the adsorption of MMA; however, the existence ofPO43- slightly enhances the adsorption. FTIR and XPS analyses demonstrated that hydroxyl and sulfur-containing functional groups are involved in the uptake of MMA. Based on the adsorption experimental results and spectroscopic analysis, an anion exchange mechanism is proposed for the adsorption of MMA.
Keywords: Adsorption; Anion exchange; Methylated arsenic; Monomethylarsonic acid; Spectroscopic analysis; Zirconia-based sorbent
The interaction of an azo compound with a surfactant and ion pair adsorption to solid phases
by Ana Carolina Ribeiro Gomes; Luciene Dias Fernandes Cafer; Paula Homem-de-Mello; Maurício Domingues Coutinho-Neto; Ivanise Gaubeur (pp. 370-377).
Display Omitted► The study on adsorption of an azo dye and their ion pairs was done onto solid phase. ► Kinetic models elucidate ionic pair adsorption process onto different solid phases. ► Experimental and theoretical studies give insight into ion pair formation. ► This study on adsorption may improve understanding about various chemical processes.The adsorption of SPADNS (trisodium salt of 2-(p-sulfophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid) onto resins XAD 2, XAD 7 and silica gel was studied in the presence and in the absence of the cationic surfactant CTAB (cetyl trimethylammonium bromide). At a ratio of 2.5 CTAB to 1 SPADNS, the surfactant caused a marked increase in SPADNS adsorption. The experimental results for adsorption versus time were applied on the basis of three kinetic models (pseudo-first-order Lagergren, pseudo-second-order, and intraparticle diffusion). The interaction between CTAB and SPADNS was investigated using spectrophotometric, conductometric, and computational techniques. Theoretical results point to the formation of an ion pair between CTAB and SPADNS that influences the solution spectra, in agreement with conductometric and spectrophotometric data.
Keywords: Azo dye; Cationic surfactant; Ion pair; Molecular dynamics; DFT; ZIndo
Removal of Cd2+ from contaminated water by nano-sized aragonite mollusk shell and the competition of coexisting metal ions
by Yang Du; Lingyan Zhu; Guoqiang Shan (pp. 378-382).
Display Omitted► Nano-sized aragonite mollusk shells display high sorption capacity to Cd2+ in water. ► Epitaxial growth of otavite inhibits the sorption of Cd2+ on nano-sized calcite. ► Coexisting metals display competing effect in the order of Cu2+>Cr3+>Pb2+>Zn2+>Ca2+. ► Sorption of Cd2+ on the nano-ARA is a spontaneous and endothermic process.The potential of using nano-sized aragonite mollusk shell (nano-Bio-ARA) to remove Cd2+ from contaminated water was investigated by comparing the sorption kinetics and isotherms with the nano-sized calcite-type mollusk shell (nano-Bio-CAL) and nano-sized geological calcite (nano-Geo-CAL). Nano-Bio-ARA displayed extremely high sorption capacity to Cd2+ (8.91mmol/g), much higher than nano-Bio/Geo-CAL, and many other natural or engineered materials. The results of thermodynamic experiments indicated that the sorption of Cd2+ on the nano-ARA was a spontaneous and endothermic process. The coexisting metals in the solution displayed competition effect to the sorption of Cd2+ on nano-Bio-ARA in the following order: Cu2+>Cr3+>Pb2+>Zn2+>Ca2+. EDTA impeded the sorption of Cd2+ on nano-Bio-ARA due to its strong chelating capacity to Cd2+ in the solution. The results demonstrate that nano-Bio-ARA is a potential high-effective material to treat Cd2+ contaminated water.
Keywords: Nano; Mollusk shell; Aragonite; Cadmium
High resolution N2 adsorption isotherms at 77.4K and 87.3K by carbon blacks and activated carbon fibers – Analysis of porous texture of activated carbon fibers byα s-method
by Kazuyuki Nakai; Yoko Nakada; Masako Hakuman; Masayuki Yoshida; Yousuke Senda; Yuko Tateishi; Joji Sonoda; Hiromitsu Naono (pp. 383-393).
Display Omitted► New αs-curve of N2 gas adsorption on nongraphitized and graphitized carbon black at 87.3K. ► Porosity characterization of microporous activated carbon fiber by the high resolution αs-plot. ► Adsorption enthalpies and entropies of N2 gas adsorption on activated carbon fiber.The standardαs -data of N2 at 87.3K by graphitized and nongraphitized carbon black samples (GCB-I and NGCB) ( cf.) have been determined on the basis of the high resolution adsorption isotherms of N2 at 87.3K, which were repeatedly measured in the pressure range of p/ po=5×10−8–0.4. The high resolution adsorption isotherms of N2 by two kinds of activated carbon fibers (ACF-I and ACF-II) were measured from p/po=10−7 to p/po=0.995 at 77.4K and from p/po=10−7 to p/po=0.4 at 87.3K. Combination of the adsorption isotherms by ACF-I and ACF-II with the standardαs -data by NGCB at 77.4K and 87.3K make it possible to construct the high resolutionα s-plots from very low filling (1%) to complete filling (100%). The high resolutionα s-plots of N2 at 77.4K and 87.3K were analyzed. On the basis of the analyzed result, the porous textures of ACF-I and ACF-II will be discussed.
Keywords: Graphitized carbon black; Nongraphitized carbon black; Activated carbons fibers; N; 2; adsorption isotherm; α; s; -Plot; Porous textures; Micropore; Isosteric heat of adsorption; Differential adsorption entropy; Micropore filling
Sulfonic acid functionalized poly(ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole) as a high-performance solid acid catalyst for the esterification of lactic acid with methanol
by Beyhan Erdem; Ali Kara (pp. 394-397).
Display Omitted► We used poly(EGDMA-VTAZ-SO3H) solid catalyst for the esterification of methyl lactate. ► We investigated the effect of water production during the esterification reaction. ► The activation energies are compared with those of other traditional acid catalysts. ► From nitrogen physisorption data, high surface area and type II isotherm are obtained. ► High density of acid sites is detrimental for the esterification reaction.Sulfonic acid functionalized poly(ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole), poly(EGDMA-VTAZ-SO3H), is evaluated in the esterification of lactic acid with methanol. From nitrogen physisorption data, high surface area (220m2/g) and type IV isotherm are obtained. Conversion measurements indicate a stronger interaction of poly(EGDMA-VTAZ-20%SO3H) with water molecules than that occurring in poly(EGDMA-VTAZ-10%SO3H). Hence, the higher catalytic activity of poly(EGDMA-VTAZ-10%SO3H) is related to the more hydrophobic microenvironment of –SO3H sites, which reduces the acid site deactivation associated with adsorption of water generated during the reaction. Moreover, apparent activation energy is found to be 48.02kJmol−1, which can be comparable with the literature values.
Keywords: Esterification; Lactic acid; Heterogeneous catalyst; Poly(EGDMA-VTAZ)
Ultrasound-assisted preparation and characterization of crystalline cellulose–ionic liquid blend polymeric material: A prelude to the study of its application toward the effective adsorption of chromium
by S. Kalidhasan; A. Santhana KrishnaKumar; Vidya Rajesh; N. Rajesh (pp. 398-408).
Display Omitted► Novel cellulose–ionic liquid blend polymeric sorbent was prepared by ultrasonication. ► The mechanism of interaction involves a bilayer assembly. ► Structural characteristics of the adsorbent were studied in detail. ► The polymeric sorbent has an adsorption capacity of 38.94mg/g for chromium. ► Adsorbent is effectively regenerated with ascorbic acid making the process green.The molecular interaction of biopolymers with an array of substrates offers interesting insight into the adsorption phenomenon. The present work proposes the preparation and characterization of cellulose–methyltrioctylammonium chloride (MeTOACl)–a room temperature ionic liquid (IL) blend polymeric sorbent and its application for the adsorption of carcinogenic chromium(VI). The blend adsorbent material was synthesized in a relatively green solvent (methylisobutylketone) medium by ultrasonication. The mechanism of interaction of biopolymer with the ionic liquid could be conceptualized as electrostatic attraction, hydrogen bonding, and Van der Waals force of attraction with the hydroxyl groups of cellulose as a bilayer assembly. The composition, crystallinity, and the surface area of the prepared material were comprehensively characterized using FT-IR, solid-state13C NMR, TGA, XRD, SEM, EDX, XPS, and BET isotherm study. The adsorption capacity of chromium(VI) calculated from Langmuir isotherm model was found to be 38.94mgg−1 with adherence to the second-order kinetics. The study of thermodynamic parameters that affect the sorption process indicated the spontaneity and exothermic nature of adsorption. The green aspect in the methodology is brought out in the regeneration of the adsorbent, where Cr(VI) could be effectively reduced to the less toxic Cr(III) using ascorbic acid.
Keywords: Chromium; Cellulose; Ionic liquid; Adsorption; Sonication
Water adsorption–desorption isotherms of two-dimensional hexagonal mesoporous silica around freezing point
by Akira Endo; Toshio Yamaura; Kyohei Yamashita; Fumio Matsuoka; Eiji Hihara; Hirofumi Daiguji (pp. 409-414).
Display Omitted► Zr-MPS could adsorb water vapor without freezing at 263K. ► The relative pressure of capillary condensation changes in consecutive measurements. ► The relative pressure of capillary evaporation depends on temperature. ► The curvature radii during capillary condensation and evaporation were elucidated.Zr-doped mesoporous silica with a diameter of approximately 3.8nm was synthesized via an evaporation-induced self-assembly process, and the adsorption–desorption isotherms of water vapor were measured in the temperature range of 263–298K. The measured adsorption–desorption isotherms below 273K indicated that water confined in the mesopores did not freeze at any relative pressure. All isotherms had a steep curve, resulting from capillary condensation/evaporation, and a pronounced hysteresis. The hysteresis loop, which is associated with a delayed adsorption process, increased with a decrease in temperature. Furthermore, the curvature radius where capillary evaporation/condensation occurs was evaluated by the combined Kelvin and Gibbs–Tolman–Koening–Buff (GTKB) equations for the modification of the interfacial tension due to the interfacial curvature. The thickness of the water adsorption layer for capillary condensation was slightly larger, whereas that for capillary evaporation was slightly smaller than 0.7nm.
Keywords: Desiccant materials; Cylindrical mesopores; GTKB–Kelvin equation; Curvature effect; Temperature effect
Adsorption of Pb(II) and Cu(II) from aqueous solution on magnetic porous ferrospinel MnFe2O4
by Yueming Ren; Nan Li; Jing Feng; Tianzhu Luan; Qing Wen; Zhanshuang Li; Milin Zhang (pp. 415-421).
.Display Omitted► Magnetic macroporous spinel MnFe2O4 was prepared by a sol–gel process. ► Adsorption capacity obtained 333.3 and 952.4μmolg−1 for Pb(II) and Cu(II). ► Carboxyl and hydroxyl groups banding on MnFe2O4 were involved in the mechanism.The adsorption of Pb(II) and Cu(II) from aqueous solution on magnetic porous ferrospinel MnFe2O4 prepared by a sol–gel process was investigated. Single batch experiment was employed to test pH effect, sorption kinetics, and isotherm. The interaction mechanism and the regeneration were also explored. The results showed that Pb(II) and Cu(II) removal was strongly pH-dependent with an optimum pH value of 6.0, and the equilibrium time was 3.0h. The adsorption process could be described by a pseudo-second-order model, and the initial sorption rates were 526.3 and 2631.5μmolg−1min−1 for Pb(II) and Cu(II) ions, respectively. The equilibrium data were corresponded well with Langmuir isotherm, and the maximum adsorption capacities were 333.3 and 952.4μmolg−1 for Pb(II) and Cu(II) ions, respectively. The adsorbed Pb(II) and Cu(II) ions were in the form of the complex with oxygen in carboxyl and hydroxyl groups binding on the surface of magnetic porous MnFe2O4. The sorbent could be reused for five times with high removal efficiency.
Keywords: MnFe; 2; O; 4; Magnetic; Porous; Pb(II) and Cu(II); Adsorption
Copper release kinetics from a long-term contaminated acid soil using a stirred flow chamber: Effect of ionic strength and pH
by David Fernández-Calviño; Alipio Bermúdez-Couso; Beatriz Garrido-Rodríguez; Susana Peña Rodríguez; Manuel Arias-Estévez (pp. 422-428).
Display Omitted► Cu release was affected by both pH and the ionic strength. ► For pH below 4.5, the effect of pH was greater than ionic strength effect. ► For pH above 4.5, the effect of pH was less than ionic strength effect. ► Cu release was higher in the presence of Ca than in the presence of Na for the same ionic strength.The effect of pH and ionic strength on copper release in a long-term Cu-polluted soil was studied using a stirred flow chamber. The presence of Ca2+ and Na+ was also evaluated. More copper was released as the ionic strength increased, and it was significantly higher in the presence of Ca2+ than in the presence of Na+. The maximum amount of Cu that could be released under experimental conditions increased logarithmically as the ionic strength increased, and the release rate parameters were not significantly correlated with ionic strength values. The maximum amount of Cu that could be released was similar for solutions with pH values between 5.5 and 8.5. For solutions with a pH value below 4.5, the amount of Cu released increased exponentially as the pH decreased. The release rate parameters and Cu release pattern were affected by pH, especially for more acidic solutions (pH values of 2.5 and 3.5).
Keywords: Cu release; Kinetics; pH; Ionic strength
Adsorption of Cu(II) from aqueous solution by anatase mesoporous TiO2 nanofibers prepared via electrospinning
by Dinhthao Vu; Zhenyu Li; Hongnan Zhang; Wei Wang; Zhaojie Wang; Xiuru Xu; Bo Dong; Ce Wang (pp. 429-435).
Display Omitted► Anatase mesoporous titanium nanofibers (m-TiO2 NFs) have been synthesized by electrospinning. ► The adsorption kinetics of Cu(II) onto m-TiO2 NFs were the best fitting by a pseudo-second order model. ► The optimum pH for Cu(II) adsorption was found to be 6.0. ► The isotherm adsorption data were well fitted by the Freundlich isotherm.Anatase mesoporous titanium nanofibers (m-TiO2 NFs) have been synthesized from calcination of the as-spun TiO2/polyvinyl pyrrolidone (PVP)/pluronic123 (P123) composite nanofibers at 450°C in air for 3h. The structures and the physicochemical properties of m-TiO2 NFs are characterized by scanning electron microscopy, X-ray diffraction, nitrogen adsorption–desorption isotherm analysis, and determination point of zero charge, respectively. An investigation of Cu(II) adsorption onto m-TiO2 NFs has been studied in this research. The pH effect, adsorption kinetics, and adsorption isotherms are examined in batch experiments. Experimental data were analyzed using pseudo-first order and pseudo-second order kinetic models. It was found that adsorption kinetics were the best fitting by a pseudo-second order kinetic model. The optimum pH for Cu(II) adsorption was found to be 6.0. The equilibrium data were analyzed by the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models, which revealed that the Freundlich isotherm is the best-fit isotherm for the adsorption of Cu(II). Compared to the TiO2 NFs (regular anatase titanium nanofibers) in the same experimental conditions to elucidate the role of the mesoporous structure of m-TiO2 NFs, experimental results showed that the m-TiO2 NFs had a better adsorption capacity for Cu(II) due to its higher surface area.
Keywords: Adsorption/adsorbents; Electrospinning; Titanium dioxide; Porous materials; Copper/copper compounds
An investigation of the mode of sorption of inositol hexaphosphate to goethite
by Bruce B. Johnson; Eben Quill; Michael J. Angove (pp. 436-442).
Display Omitted► IP6 adsorbs to goethite by outer-sphere complexation. ► IP6 solution and sorbed ATR-FTIR spectra are analysed. ► Infrared bands assigned to vibrational modes. ► Hydrogen-bonding plays an important role in adsorption across the pH range.Adsorption of inositol hexaphosphate (IP6) on goethite has been studied as a function of pH and concentration, and by use of Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR). While adsorption was highest at low pH, a significant amount remained adsorbed above pH 10 where, in the absence of IP6, the surface is expected to have a net negative charge. The adsorption isotherm at pH 5.5 indicated strong binding to the surface with each adsorbed species occupying about 2.5nm2. ATR-FTIR spectra of IP6 solutions in the pH range from 2 to 12 were fitted with a single set of IR bands which were assigned primarily by analogy with phosphate spectra. From its variation in intensity with pH the band at 1040cm−1 was assigned to the effect of hydrogen bonding on the PO vibration. No additional bands were required to fit the spectra of IP6 adsorbed to goethite, indicating that adsorption occurs by outer-sphere complexation in this system. At all pH values studied the band associated with hydrogen bonding was more intense for the adsorbed species than in solution at the corresponding pH indicating that hydrogen bonding plays an important role in binding IP6 to goethite.
Keywords: Adsorption; Inositol hexaphosphate; Phytate; Goethite; ATR-FTIR; Outer-sphere complexation; Hydrogen-bonding
Facile fabrication of a superamphiphobic surface on the copper substrate
by Xiaotao Zhu; Zhaozhu Zhang; Xianghui Xu; Xuehu Men; Jin Yang; Xiaoyan Zhou; Qunji Xue (pp. 443-449).
The surface can support a composite interface and display high contact angles (CAs) with several liquids possessing low surface tension.Display Omitted► The superamphiphobic surface was fabricated by a facile method. ► The surface wettability can be tuned by surface constitution and geometrical structure. ► The superamphiphobic surface can remain the Cassie state after immersion and compression test. ► The superamphiphobic property can be easily restored when damaged.A simple solution-immersion technique was developed for the fabrication of a superamphiphobic surface on the copper sheet. Hierarchical structure composed of nanorod arrays and microflowers was formed on the copper surface by an alkali assistant oxidation process; after fluorination, the surface became super-repellent toward water and several organic liquids possessing much lower surface tension than that of water, such as hexadecane. Such superamphiphobicity is attributed to the synergistic effect of their special surface chemicals and microscopic structures, which allows for the formation of a composite interface with all probing liquids tested. We also discuss the effects of surface chemical constituent and geometrical structure on hydrophobicity and oleophobicity; such information allows us to engineer surfaces with specific oleophobic behavior. Additionally, the stability of the composite interface on the created superamphiphobic surface is studied by the compression and immersion test.
Keywords: Simple fabrication; Superhydrophobic; Superoleophobic; Controllable surface wettability; Solution-immersion process; Re-entrant texture
Ratchet composite thin film for low-temperature self-propelled Leidenfrost droplet
by Ruotao Feng; Wenjie Zhao; Xuedong Wu; Qunji Xue (pp. 450-454).
The LFP of a water droplet on the composite hydrogenated carbon film was lower than that on the alumina film.Display Omitted► Wettability of ratchet film is effective to the LFP of self-propelled droplet. ► The more hydrophobic surface may have a higher Leidenfrost point than the less one. ► The sawtooth width should be smaller than the droplet radius to propel the droplet.The droplet control, especially for the self-propelled Leidenfrost droplet, has attracted many researchers’ attention in applied and fundamental fields. In this paper, the ratchet thin film was fabricated by magnetron sputtering and hybrid ion beams deposition. The micro- and nanoscale structure of the film was characterized by field emission scanning electron microscope. This study reports an interesting phenomenon that the self-propelled Leidenfrost water droplet was initiated at low temperature. The Leidenfrost point of droplets was controlled by the surface wettability and parameters of the asymmetric ratchet substrate. This novel self-propelled interfacial material and preparation technology can be expanded to the manufacture process and constructed a temperature-dependent tubule for microfluidic systems.
Keywords: Thin film; Wettability; Leidenfrost droplet; Droplet control; Microfluidic system
Wafer-scale thin encapsulated two-dimensional nanochannels and its application toward visualization of single molecules
by H.T. Hoang; H.D. Tong; I.M. Segers-Nolten; N.R. Tas; V. Subramaniam; M.C. Elwenspoek (pp. 455-459).
Display Omitted► Sub-20nm dimensions channels are fabricated based on conventional microfabrication techniques. ► These fabricated channels with 10mm length have been successfully filled by capillary action. ► Initial experiment result and analyses of single fluorescent Alexa molecules at the static mode are presented.We present a new and simple approach to fabricate wafer-scale, thin encapsulated, two-dimensional nanochannels by using conventional surface-micromachining technology and thin-film evaporation. The key steps to the realization of two-dimensional nanochannels are a fine etching of a sacrificial layer to create underetching spaces at the nanometer regime, and an accurate thin-film evaporation for encapsulation. Well-defined cross-sectional, encapsulated nanochannel arrays with dimensions as small as 20nm in both width and height have been realized at the wafer-scale. The fabricated nanochannels with a channel length of 10mm have been used as a suitable fluidic platform for confining a solution containing nanomolar concentrations of Alexa fluorescent molecules. Initial results toward visualization of single Alexa molecules in the confined solution are reported.
Keywords: Nanochannels; Fabrication; Single-molecule; Confinement
Multi-functional nanopatterned optical films fabricated using capillary force lithography
by Moon Kyu Kwak; Yong-Woon Lim (pp. 460-466).
Display Omitted► We fabricate nanopatterned optical film that has multi-function. ► Capillary force lithography with surface treatment is used for clean patterning. ► Fabricated film acts roles of retardation, LC alignment, and anchoring enhanced film. ► By choosing fluorine treated surface, certain LC alignment is able to be expressed.We demonstrate anisotropic optical films based on liquid crystalline polymer (LCP) using a capillary force lithography (CFL). The fabricated optical films can be used as both an optical component and a self-aligning capability of liquid crystal molecules introduced on the film. Additionally, HA or PA LC can be induced on same material by controlling the water repellency of LCP surface. Moreover, surface anchoring transitions could be controlled by variation of pattern sizes and surface treatment. In this point of view, one thin optical film can act both retarder and alignment layer and then shows good retardation, LC alignment, and transmittance at the same time.
Keywords: Capillary force lithography (CFL); Liquid crystalline polymer (LCP); Surface anchoring energy; Contact angle
Nanostructured films from phthalocyanine and carbon nanotubes: Surface morphology and electrical characterization
by Jackeline B. Brito; Douglas J.C. Gomes; Vanessa D. Justina; Aline M.F. Lima; Clarissa A. Olivati; Josmary R. Silva; Nara C. de Souza (pp. 467-471).
Display Omitted► We obtained nanostructured films of NiTsPc with MWNT using the LbL technique. ► Surface morphology was investigated by using fractal concepts and dynamic scale laws. ► We correlated the fractality of the films with the wettability of surfaces.We report on the investigation of the surface morphology and DC conductivity of nanostructured layer-by-layer (LbL) films from nickel tetrasulfonated phthalocyanine (NiTsPc) alternated with either multi-walled carbon nanotubes (MWNTs/NiTsPc) or multi-walled carbon nanotubes dispersed in chitosan (MWNTs+Ch/NiTsPc). We have explored the surface morphology of the films by using fractal concepts and dynamic scale laws. The MWNTs/NiTsPc LbL films were found to have a fractal dimension of ca. 2, indicating a quasi Euclidean surface. MWNTs+Ch/NiTsPc LbL films are described by the Lai–Das Sarma–Villain (LDV) model, which predicts the deposition of particles and their subsequent relaxation. An increase in the wetting contact angle of MWNTs+Ch/NiTsPc LbL films was observed, as compared with MWNTs/NiTsPc LbL films, which presented an increase in the fractal dimension of the first system. Room temperature conductivities were found be ca. 0.45S/cm for MWNTs/NiTsPc and 1.35S/cm for MWNTs+Ch/NiTsPc.
Keywords: Multi-walled carbon nanotubes; Nickel tetrasulfonated phthalocyanine; Layer-by-layer (LbL) self-assembly films; Wetting contact angle; DC electrical conductivity; LDV model
Contact angles of drops on curved superhydrophobic surfaces
by Goutham Viswanadam; George G. Chase (pp. 472-477).
Display Omitted► An equation is derived for estimating the apparent contact angle on spherical surfaces. ► The equation compares well for experimental data reported in literature for drops on spheres. ► Experiments are conducted with drops on cylindrical superhydrophobic surfaces. ► The equation compares well for drops on cylindrical superhydrophobic surfaces.Superhydrophobic surfaces have contact angles that exceed 150 degrees and are known to reduce surface fouling, protect surfaces, and improve liquid–liquid separations. Electrospun sub-micron fiber mats can perform as superhydrophobic surfaces. Superhydrophobic behavior is typically measured on planar surfaces, whereas applications may require curved surfaces. This paper discuses the measurement of water contact angles of fiber mats formed on cylindrical surfaces to create superhydrophobic behavior on curved surfaces. Equations are derived that relate the radius of curvature of spherical and cylindrical surfaces and drop size to the observed contact angle on the curved surfaces. Calculations from the equations agree well with experimental observations on spherical surfaces reported in literature and on cylindrical surfaces created in our lab.
Keywords: Contact angle; Nanofibers; Electrospinning; Superhydrophobic; Drops; Droplets; Wetting
The effect of polymer adsorption on the wetting properties of partially hydrophobized magnetite
by E. Potapova; M. Grahn; A. Holmgren; J. Hedlund (pp. 478-484).
Display Omitted► Cationic, anionic, and non-ionic polymers adsorbed on magnetite coated with surfactant. ► Ammonium polyacrylate improved wetting of magnetite coated with surfactant. ► Hydrophilic polyacrylate chains shielded adsorbed surfactant from the water phase. ► Polyacrylate adsorbed on magnetite via calcium ions. ► Contact angle remained low at high pH and after storing magnetite in air for 24h.Upon reverse flotation of iron ore, the surface of the iron ore concentrate may become partially hydrophobized due to adsorption of flotation collector, which is facilitated by the calcium ions present in the process water. Hydrophobic areas on the concentrate surface may introduce problems in subsequent pelletization of the concentrate. A possible way to restore the wettability of the surface could be by modifying the surface with a hydrophilic polymer. The effect of hydrophilic polymers of different types, viz. cationic, anionic, and non-ionic, on the wettability of the magnetite surface after adsorption of a surfactant was investigated. Although all the polymers could adsorb on magnetite at pH 8.5, the contact angle measurements revealed that only anionic ammonium polyacrylate could decrease the contact angle of synthetic magnetite after surfactant adsorption to a level close to that of as-synthesized magnetite. Such effect was probably achieved due to shielding of the hydrophobic surfactant chains from the aqueous phase by hydrophilic polyacrylate molecules. The fact that polyacrylate adsorption on magnetite occurred via calcium ions makes polyacrylate suitable for application in calcium-rich process water. The results presented in this work illustrate that ammonium polyacrylate could be successfully used to improve the wettability of magnetite after adsorption of surfactants.
Keywords: Adsorption; ATR–FTIR; Contact angle; Magnetite; Polymer; Wettability; Surfactant; Polyacrylate
Cobalt (II) chloride promoted formation of honeycomb patterned cellulose acetate films
by Olga Naboka; Anke Sanz-Velasco; Per Lundgren; Peter Enoksson; Paul Gatenholm (pp. 485-493).
Display Omitted► Honeycomb patterned films were prepared from cellulose acetate (CA)/CoCl2 solutions. ► Water droplets condensed on the (CA)/CoCl2 solution surface act as a template. ► Size and pore regularity in films depends on the CA/CoCl2 molar ratio and humidity. ► Pore formation is caused by hygroscopicity of CoCl2 and its low interaction with CA.CoCl2 containing honeycomb patterned films were prepared from cellulose acetate (CA)/CoCl2/acetone solutions by the breath figure method in a wide range of humidities. Size and pore regularity depend on the CA/CoCl2 molar ratio and humidity. When replacing CoCl2 with Co(NO3)2 or CoBr2, no formation of ordered porosity in the cellulose acetate films is observed. According to data from scanning electron microscopy (SEM), Energy Dispersive X-ray Microanalysis (EDX), X-ray Diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, the key role in the formation of honeycomb structures can be attributed to the physical and chemical properties of CoCl2 – hygroscopicity, low interaction with CA, and extraction from CA/CoCl2/acetone solution by water droplets condensed on the surface of the CA/CoCl2 solution. Obtained films are prospective for using in catalysis, hydrogen fuel cells, and optical sensing materials.
Keywords: Abbreviations; BSE; back scattering electrons; CA; cellulose acetate; C; concentration, g/100; ml; EDX; Energy Dispersive X-ray Microanalysis; FTIR; Fourier transform infrared; Glc; acetylated β-; d; -glucopyranose unit; SEM; scanning electron microscopy; XRD; X-ray DiffractionHoneycomb patterned film; Cellulose acetate; Cobalt (II) chloride; Breath figure method
Synthesis of a thermosensitive surface by construction of a thin layer of poly ( N-isopropylacrylamide) on maleimide-immobilized polypropylene
by Thelma S.P. Cellet; Marcos R. Guilherme; Rafael Silva; Guilherme M. Pereira; Marcos R. Mauricio; Edvani C. Muniz; Adley F. Rubira (pp. 494-501).
Display Omitted► A thin layer of PNIPAAm was constructed on activated polypropylene surface. ► PNIPAAm layer corrected both depressions and fissures of the surfaces. ► Water contact angles of the layered surfaces revealed a transition at 33.5–36.5°C. ► Modified polypropylene surfaces showed nature both hydrophilic and hydrophobic.Thermosensitive surfaces were developed by the grafting of a thin layer of PNIPAAm through an UV-induced photopolymerization reaction of vinyl monomers with a free radical-activated polypropylene (PP) surface. PNIPAAm layer covering the PP surface corrected, to some extension, both depressions and fissures of the previously modified PP surfaces. The layered surfaces have morphological characteristic different from those of the non-layered surfaces, and their thickness was dependent on irradiation time. Water contact angles of the layered surfaces revealed a transition at approximately 33.5–36.5°C as a result of a response to the variation of temperature. There was an increase in the values of the contact angles with an increase in temperature from 26°C to 44°C, revealing the nature both hydrophilic and hydrophobic of the surfaces due to a conformational rearrangement of PNIPAAm exposing its isopropyl groups to the liquid drop. This work offers a chemically stable thermosensitive surface (because it is covalently structured) with great potential for use as sensors and actuators.
Keywords: Graft copolymers; Layer growth; Photopolymerization; Stimuli-sensitive polymers; Surfaces
Super-hydrophobic, highly adhesive, polydimethylsiloxane (PDMS) surfaces
by Morgan M. Stanton; Robert E. Ducker; John C. MacDonald; Christopher R. Lambert; W. Grant McGimpsey (pp. 502-508).
Display Omitted► The facile fabrication of a super-hydrophobic, adhesive surface has been accomplished with a simple templating technique. ► Polymer surface exhibits a static, aqueous, contact angle of >153.5°. ► The adhesive surface will allow a 25μL drop to be suspended from it when inverted. ► The system mimics the water interaction behavior of the rose petal.Super-hydrophobic surfaces have been fabricated by casting polydimethylsiloxane (PDMS) on a textured substrate of known surface topography, and were characterized using contact angle, atomic force microscopy, surface free energy calculations, and adhesion measurements. The resulting PDMS has a micro-textured surface with a static contact angle of 153.5° and a hysteresis of 27° when using de-ionized water. Unlike many super-hydrophobic materials, the textured PDMS is highly adhesive, allowing water drops as large as 25.0μL to be inverted. This high adhesion, super-hydrophobic behavior is an illustration of the “petal effect”. This rapid, reproducible technique has promising applications in transport and analysis of microvolume samples.
Keywords: Super-hydrophobic adhesive; Petal effect; Templating
pH-responsive interpenetrating network hydrogel beads of poly(acrylamide)- g-carrageenan and sodium alginate for intestinal targeted drug delivery: Synthesis, in vitro and in vivo evaluation
by Raghavendra V. Kulkarni; Rashmi Boppana; G. Krishna Mohan; Srinivas Mutalik; Navanath V. Kalyane (pp. 509-517).
Display Omitted► Novel pH-responsive IPN hydrogel beads were synthesized for drug delivery application. ► IPN hydrogel beads offered pulsatile swelling and drug release behavior in response to pH. ► A maximum drug release of 10% in pH 1.2 solution and 90% in pH 7.4 was recorded. ► Stomach histopathology of albino rats suggested the usefulness of IPN hydrogel beads.In the present work, we synthesized pH-responsive interpenetrating network (IPN) hydrogel beads of polyacrylamide grafted κ-carrageenan (PAAm- g-CG) and sodium alginate (SA) for targeting ketoprofen to the intestine. The PAAm- g-CG was synthesized by free radical polymerization followed by alkaline hydrolysis under nitrogen gas. The PAAm- g-CG was characterized by elemental analysis, FTIR spectroscopy and thermogravimetric analysis (TGA). The drug-loaded IPN hydrogel beads were prepared by simple ionotropic gelation/covalent crosslinking method. The amorphous nature of drug in the beads was confirmed by differential scanning calorimetry and X-ray diffraction studies. The spherical shape of the beads was confirmed by scanning electron microscopic analysis. The beads exhibited ample pH-responsive behavior in the pulsatile swelling study. The ketoprofen release was significantly increased when pH of the medium was changed from acidic to alkaline. The beads showed maximum of 10% drug release in acidic medium of pH 1.2, and about 90% drug release was recorded in alkaline medium of pH 7.4. Stomach histopathology of albino rats indicated that the prepared beads were able to retard the drug release in stomach leading to the reduced ulceration, hemorrhage and erosion of gastric mucosa.
Keywords: Interpenetrating polymer network; Polymer grafting; Drug targeting; Ketoprofen; Stomach histopathology
Self-assembled amorphous drug–polyelectrolyte nanoparticle complex with enhanced dissolution rate and saturation solubility
by Wean Sin Cheow; Kunn Hadinoto (pp. 518-526).
Display Omitted► Amorphous nanoparticle complex (nanoplex) of sparingly soluble drug. ► Prepared by sustainable self-assembly drug–polyelectrolyte complexation process. ► Spherical nanoplex with 80% drug loading, >80% complexation efficiency and yield. ► Twice higher dissolution rate and solubility, stable in storage. ► Promising bioavailability-enhanced formulation of poorly soluble drugs.The dissolution rate and solubility of poorly soluble drugs can be enhanced by formulating them into stable amorphous nanoparticle complex (nanoplex). For this purpose, a highly sustainable self-assembly drug–polyelectrolyte complexation process is developed, with ciprofloxacin and dextran sulfate as the drug and polyelectrolyte models, respectively. The nanoplex are prepared by mixing two aqueous salt solutions – one containing the drug and the other containing the oppositely charged polyelectrolyte. The nanoplex suspension is transformed into stable dry-powder form by freeze-drying. The effects of drug concentration, drug-to-polyelectrolyte charge ratio, and salt concentration on the complexation efficiency, yield, drug loading, and nanoplex morphology are examined. The dissolution rates and solubility of the nanoplex are characterized and compared to raw drug crystals. Nearly spherical amorphous nanoplex having fairly uniform sizes in the range of 200−400nm and 80% drug loading are successfully produced at ⩾80% complexation efficiency and yield. The complexation efficiency is governed by the drug concentration and its ratio to the salt concentration. The nanoplex powders exhibit approximately twice higher dissolution rate and solubility than raw drug crystals and remain stable after one-month storage. Overall, amorphous nanoplex represent a promising bioavailability-enhanced formulation of poorly soluble drugs owed to their superior characteristics and ease of preparation.
Keywords: Abbreviations; API; active pharmaceutical ingredients; ATCC; American Type Culture Collection; CE; complexation efficiency; CIP; ciprofloxacin; CIP nanoplex; nanoparticles of ciprofloxacin–dextran complex; CTAB; cationic alkyl trimethylammonium bromide; DSC; differential scanning calorimetry; DXT; dextran sulfate; FE−SEM; field emission scanning electron microscopy; HPMC; hydroxypropylmethylcellulose; MHB; Mueller Hinton broth; nano-API; API nanoparticles; OD; optical density; PBS; phosphate buffer saline; PEI; polyethyleneimine; PVP; polyvinylpyrrolidone; PXRD; powder X-ray diffraction; SDS; sodium dodecyl sulfate; TGA; thermogravimetric analysisNanoparticle; Amphiphile–polyelectrolyte complexation; Self-assembly; Solubility; Amorphous
Particle sizing of colloidal suspensions by low-coherence fiber optic dynamic light scattering
by Hui Xia; Yuan Yuan Xiao; Hao Huang; Shao Hua Tao; Xu Lin (pp. 527-530).
Display Omitted► We present a particle sizing technique combining low-coherence interferometry and FODLS. ► The temporal electric field autocorrelation function of singly scattered light can be measured. ► We can estimate the particle size in a broad volume fraction range use CONTIN method. ► The particle size can be obtained with the accuracy 5% in the volume fraction range from 0.01 to 0.1.A low-coherence fiber optic dynamic light scattering technique is used to measure the particle size distributions of colloidal suspensions with different volume fractions. We detect electric field autocorrelation function of the singly backscattered light from a sample and use the CONTIN algorithm to obtain the particle size distributions. As a result, in the range of volume fractions from 0.01 to 0.10 of monodispersive colloidal suspensions, the mean particle size with the deviation within 4% and the polydispersity approximate 5% can be determined for particles of different radii. The results demonstrate that the low-coherence fiber optic dynamic light scattering technique is effective in measuring particle size of colloidal suspensions.
Keywords: Colloidal suspensions; Particle sizing; Low-coherence fiber optic dynamic light scattering; CONTIN
Mesoporous hollow spheres from soap bubbling
by Xianglin Yu; Fuxin Liang; Jiguang Liu; Yunfeng Lu; Zhenzhong Yang (pp. 531-536).
The schematic preparative method of hollow spheres via blowing bubbles, the dependence of particulate morphologies on gas flows, the hollow spheres, and the mesoporous structure.Display Omitted► A novel method for preparation of hollow spheres by blowing bubbles of a sol containing surfactants. ► Morphological evolution depends on flow rates of interior and exterior gas. ► A mesoporous shell could be obtained by introducing porogen into the sol.The smaller and more stable bubbles can be generated from the large parent bubbles by rupture. In the presence of a bubble blowing agent, hollow spheres can be prepared by bubbling a silica sol. Herein, the trapped gas inside the bubble acts as a template. When the porogen, i.e., other surfactant, is introduced, a mesostructured shell forms by the co-assembly with the silica sol during sol–gel process. Morphological evolution emphasizes the prerequisite of an intermediate interior gas flow rate and high exterior gas flow rate for hollow spheres. The method is valid for many compositions from inorganic, polymer to their composites.
Keywords: Soap bubble; Hollow spheres; Mesoporous structure
Rheological and rheo-SALS investigation of the multi-lamellar vesicle formation in the C12E3/D2O system
by Luigi Gentile; Cesare Oliviero Rossi; Ulf Olsson (pp. 537-539).
Display Omitted► Shear-induced structures: shear-induced lamellar-to-MLV transition in 50wt% C12E3/D2O system. ► Rheo-SALS and rheology elucidate the shear-induced transition. ► The SALS patterns give the size distributions of the MLVs obtained at different shear rates (10, 20, 40s−1).Usually in nonionic surfactant aqueous systems of the C nE m type, a lamellar phase occurs over a wide temperature and concentration range. For some C nE m surfactants, multi-lamellar vesicle (MLV) formation has been observed when the lamellar phase is subjected to shear flow.This communication reports the shear flow behavior at different shear rate values of a C nE m (where “ n” is 12 and “ m” is 3) aqueous system at 34°C. The typical transient viscosity behavior of the shear-induced MLV formation in C12E3/D2O at 50wt% of surfactant has been observed. The MLV formation is confirmed by time-resolved rheo-small angle light scattering (SALS) experiments. The experimental data show an intermediate structure that has been attributed to a multi-lamellar cylinders (MLCs).
Keywords: Rheology; Rheo-SALS; MLV formation; Onions; C; n; E; m