Journal of Colloid And Interface Science (v.362, #2)
Spectral and electrochemical studies of bis(diimine)copper(II) complexes in anionic, cationic and nonionic micelles
by N. Anitha; R. Balamurugan; M. Palaniandavar (pp. 243-252).
The complexes [Cu(diimine)2Cl]Cl exist as [Cu(diimine)2(H2O)2]2+ species in aqueous SDS but as [Cu(diimine)2Cl2] and/or [Cu(diimine)2(H2O)Cl]+ species in aqueous CTAB and TX-100 micelles and tend to exhibit reversible Cu(II)/Cu(I) redox in micellar microenvironments.Display Omitted► [Cu(diimine)2(H2O)2]2+ interacts strongly with SDS than with CTAB and Triton X-100 micelles. ► The Cu(II)/Cu(I) coupleattains electrochemical reversibility in micellar microenvironments. ► The substituents on the diimine ligands determine the type of interaction in the micellar interior.The spectral and redox behavior of bis(diimine)copper(II) complexes, where diimine is bipyridine, 1,10-phenanthroline, 4-methyl-1,10-phenanthroline, 5-methyl-1,10-phenanthroline, 5-nitro-1,10-phenanthroline, 4,7-dimethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline and dipyrido-[3,2- d:2′,3′- f]-quinoxaline, are significantly different in aqueous and in aqueous SDS, CTAB and Triton X-100 micellar solutions. The1H NMR spectral study in aqueous (D2O) and aqueous micelles reveals that the Cu(II) complexes interact more strongly with SDS than with CTAB and Triton X-100 micelles and at sites on SDS micelles different from those on the latter. Ligand Field spectral studies reveal that the complexes exist as the dicationic aquated species [Cu(diimine)2(H2O)2]2+, which interacts strongly with the anionic SDS micelles through columbic forces. However, they exist as [Cu(diimine)2(H2O)Cl]+ and/or [Cu(diimine)2H2] located in the hydrophobic microenvironments in Triton X-100 and CTAB micelles. The attainment of reversibility of the redox systems in the micellar microenvironments is remarkable and this illustrates that the Cu(II) and Cu(I) species undergo stereochemical changes suitable for reversible electron-transfer. The remarkable differences in spectral and electrochemical properties of Cu(II) complexes in aqueous and aqueous micellar solutions illustrate that the complexes are nestled largely within the micellar environments and imply that the accessibilities of the complexes to electron-transfer are different and are dependent on the nature of micelles as well as the nature and hydrophobicity of the diimine ligands.
Keywords: Bis(diimine)copper(II) complexes; Micelles; Redox behavior
Silicon dioxide hollow microspheres with porous composite structure: Synthesis and characterization
by Xiuli Yan; Zhongli Lei (pp. 253-260).
Procedure for preparation of SiO2 hollow microspheres with porous. SEM images show a perfectly whole microsphere and the spherical surface morphology is flowerlike structure.Display Omitted► We used template replication method to prepare the hollow porous silica spheres. ► The pore size is changed with the concentration of ammonium hydroxide. ► The surface morphologies are changed with the volume of TEOS. ► Hollow porous silica microspheres with ideally flower structure was obtained.In this paper, a strategy for hollow porous silica microspheres with ideally flower structure is presented. SiO2/PAM hybrid composite microspheres with porous were synthesized by the reaction that the porous polyacrylamide (PAM) micro-gels immersed in tetraethoxysilane (TEOS) anhydrous alcohol solution and water in a moist atmosphere, with ammonium hydroxide as a catalyst. The SiO2 hollow microspheres with porous were obtained after calcination of the composite microspheres at 550°C for 4h. The morphology, composition, and crystalline structure of the microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FI-IR), and X-ray diffraction (XRD), N2 absorption analysis, respectively. The results indicated that the obtained hollow porous SiO2 microspheres were a perfect flower structure.
Keywords: Hollow porous SiO; 2; microsphere; Micro-gel template; Surface morphology
Tailoring the carbon nanostructures grown on the surface of Ni–Al bimetallic nanoparticles in the gas phase
by Whi Dong Kim; Ji Young Ahn; Dong Geun Lee; Hyung Woo Lee; Suck Won Hong; Hyun Seol Park; Soo H. Kim (pp. 261-266).
Gas-phase tailoring of carbon nanostructures was made by taking advantage of synergistic effect between the size of spray-pyrolized Ni–Al bimetallic nanoparticles and the reacting temperature in the thermal CVD.Display Omitted► Gas-phase growth of straight, coiled, and sea urchin carbon nanostructures is made. ► The size of Ni–Al nanoparticles and temperature determine the carbon nanostructures. ► Straight carbon nanotubes are grown on Ni–Al nanoparticles <100nm at 650–800°C. ► Coiled carbon nanotubes are grown on Ni–Al nanoparticles <100nm at 500–650°C. ► Sea urchin carbon nanotubes are grown on Ni–Al nanoparticles >100nm at 500–800°C.A gas-phase, one-step method for producing various aerosol carbon nanostructures is described. The carbon nanostructures can be selectively tailored with either straight, coiled, or sea urchin-like structures by controlling the size of Ni–Al bimetallic nanoparticles and the reaction temperature. The carbon nanostructures were grown using both conventional spray pyrolysis and thermal chemical vapor deposition. Bimetallic nanoparticles with catalytic Ni (guest) and non-catalytic Al (host) matrix were reacted with acetylene and hydrogen gases. At the processing temperature range of 650–800°C, high concentration straight carbon nanotubes (S-CNTs) with a small amount of coiled carbon nanotubes (C-CNTs) can be grown on the surface of seeded bimetallic nanoparticle size <100nm, resulting from consumption of the melting Al matrix sites; sea urchin-like carbon nanotubes (SU-CNTs) of small diameter (∼10±4nm) can be grown on the bimetallic nanoparticle size >100nm, resulting from the significant size reduction of the available Ni sites due to thermal expansion of molten Al matrix sites without consumption of Al matrix. However, at the processing temperature range of 500–650°C, C-CNTs can be grown on the bimetallic nanoparticle size <100nm due to the presence of Al matrix in the bimetallic nanoparticles; SU-CNTs of large diameter (∼60±13nm) can also be grown on the bimetallic nanoparticle size >100nm due to the isolation of Ni sites in the Al matrix.
Keywords: Carbon nanostructures; Bimetallic nanoparticles; Spray pyrolysis; Thermal chemical vapor deposition; Aerosol synthesis
Mechanistic studies on the formation of silver nanowires by a hydrothermal method
by Takuya Tetsumoto; Yasuo Gotoh; Tsutomu Ishiwatari (pp. 267-273).
The side of the Ag nanowire is covered with a 5−10nm-thick layer consisting of graphite and/or polymer derived from glucose.Display Omitted► Cl− ions and reaction conditions are important for preparation of Ag nanowires. ► Ag nanowire surfaces possessed carbon-based layer derived from glucose. ► Diameter of Ag nanowires increased with reaction time. ► Carbon-based layer possessing carboxyl groups bound with Ag+ ions could be produced. ► Surface energy differences in Ag crystals led to anisotropic growth of Ag particles.Silver (Ag) nanowires were fabricated from silver chloride (AgCl) by the hydrothermal method. The successful formation of Ag nanowires relied on the low solubility of AgCl as a precursor and the structural change of glucose to polymer on the Ag nanowire (protective layer). The Ag+ ion concentration in the reaction solution containing AgCl was initially low, but after a reaction time of over 12h, Ag+ gradually reduced to Ag metal. Transmission electron microscope, Raman spectrometery, and X-ray photoelectron spectroscopy revealed that the surface of the obtained Ag nanowires possessed a carbon-rich layer with a carboxyl group, and the Ag+ ion coordinated with the carboxyl group of this layer. The difference in the surface-free energy of Ag crystals changed the crystal growth rate that impelled the anisotropic growth of the Ag particles. By examining various reaction conditions, it was determined that the ratio of Cl− to Ag+, reaction temperature, and reaction time are important factors for successful preparation of Ag nanowires. Under the reaction condition that the molar ratio of Cl− to Ag+ at 160°C for 24h is above equimolar concentration, uniform Ag nanowires were successfully prepared.
Keywords: Silver nanowires; Hydrothermal method; Anisotropic nanofillers; Silver chloride
UV-curable low surface energy fluorinated polycarbonate-based polyurethane dispersion
by Hyeon-Deuk Hwang; Hyun-Joong Kim (pp. 274-284).
Very low concentrations of PFPE resulted in an efficient decrease in surface free energy to 19–27mN/m because PFPE in soft segment was tailored easily to the surface.Display Omitted► The surface free energy decreased with increasing PFPE concentration. ► A hydrophobic UV-cured film surface enriched with fluorinated species. ► The incorporation of PFPE decreased effectively the refractive index.UV-curable low surface energy fluorinated polycarbonate-based polyurethane dispersions were synthesized by incorporating a hydroxy-terminated perfluoropolyether (PFPE) into the soft segment of polyurethane. The effects of the PFPE content on the UV-curing behavior, physical, surface, thermal properties and refractive index were investigated. The UV-curing behavior was analyzed by photo-differential scanning calorimetry. The surface free energy of the UV-cured film, which is related to the water or oil repellency, was calculated from contact angle measurements using the Lewis acid–base three liquids method. The surface free energy decreased significantly with increasing fluorine concentration because PFPE in the soft segment was tailored to the surface and produced a UV-cured film with a hydrophobic fluorine enriched surface, as confirmed by X-ray photoelectron spectroscopy. With increasing the fluorine content, the refractive indices of UV-cured films decreased. However, the UV-curing rate and final conversion was decreased with increasing contents of PFPE, which resulted in the decrease of the glass transition temperature (T g), crosslink density, tensile strength and surface hardness.
Keywords: Perfluoropolyether; Polyurethane; Polycarbonate diol; Surface free energy; Waterborne; UV-curing
Spreading of triple line and dynamics of bubble growth inside nanoparticle dispersions on top of a substrate plate
by Saeid Vafaei; Dongsheng Wen (pp. 285-291).
Different developments of triple line and bubble volume are shown for bubbles growing in pure water and an aqueous gold nanofluid.Display Omitted► Surface wettability is engineered by introducing nanoparticles in the liquid phase. ► Different nanoparticles affect surface wettability differently. ► Gold particle shows an early-pinning of the triple line during bubble formation. ► Alumina particle shows a late-pinning of the triple line during bubble formation. ► The variation of solid surface tensions at the triple line shall be responsible.This work investigates the feasibility of engineering surface wettability by using different nanoparticles. As an illustration, detailed formation of gas bubbles on top of a stainless steel substrate plate in a quiescent pool of aqueous gold and alumina nanofluids is studied. The presence of nanoparticles is shown to be able to modify the dynamics of triple line and bubble growth significantly. An early pinning of the bubble triple line is observed and a larger bubble contact angle is found for bubbles growing in a gold nanofluid, whereas an opposite phenomenon is observed for bubbles growing in an alumina nanofluid compared to those of pure water. Other bubble parameters such as departure volume, bubble frequency, and waiting time of bubble formation are also affected by the presence of nanoparticles. The variation of solid surface tensions due to the existence of nanoparticles and the resultant force at the triple line should be responsible for such differences. Such results illustrate the big potential of nanoparticle in engineering surface wettability of a solid–liquid–gas system.
Keywords: Bubble; Boiling; Critical heat flux; Surface wettability; Bubble contact angle; Droplet contact angle; Gold nanofluids; Alumina nanofluids; Solid surface tensions; Surface tension
Synthesis of zinc tin oxide (ZTO) nanocrystallites at room temperature through association with peptide-containing bolaamphiphile molecules
by Sungjun Ahn; Tae-Geun Kwon; Sang-Yup Lee (pp. 292-299).
Using self-assembly of peptide-containing bolaamphiphile molecules, ZTO nanocrystallites were synthesized at room temperature whose banfgap energy is comparable to that of nanoparticles prepared by hydrothermal method.Display Omitted► ZTO nanocrystallite was prepared using a peptide-containing bolaamphiphile molecule. ► Prepared ZTO has same electrooptical property with conventionally prepared ones. ► Ligation of bolaamphiphile with the metal ions promotes crystalline ZTO formation.Single crystalline zinc tin oxide (ZTO) nanocrystallites were prepared at room temperature through association with a peptide-containing bolaamphiphile molecule. The bolaamphiphile molecules self-assembled to form spherical structures with creation of ZTO nanocrystallites inside. ZTO nanocrystallite synthesis was achieved only when the bolaamphiphile molecule was present, while a mixture of amorphous Sn and Zn precipitates was formed in the absence of the bolaamphiphile molecule. The bolaamphiphile molecule is thought to stabilize the Zn2+ and Sn4+ precursor ions by ligation and to induce subsequent condensation forming crystalline ZTO. The ZTO formation was achieved only at a strong acidic condition that promotes dissociation and ionization of Zn and Sn precursors and represses formation of ZnO and H2SnO3. The prepared ZTO nanocrystallites had almost the same band gap energy as ZTO nanoparticles prepared by the conventional hydrothermal process. The outcomes of this study indicate that the controlled mineralization of metal precursor ions in a peptide-containing bolaamphiphile molecule suspension can be an alternative method to synthesize metal oxides at room temperature, while maintaining their crystalline structure and optoelectrical properties.
Keywords: Zinc tin oxide; Nanocrystallites; Bolaamphiphile; Biomimetic synthesis
Elaboration of nano-structured grafted polymeric surface
by Tjasa Vrlinic; Dominique Debarnot; Miran Mozetic; Alenka Vesel; Janez Kovac; Arnaud Coudreuse; Gilbert Legeay; Fabienne Poncin-Epaillard (pp. 300-310).
The grafting of polymers and surfactant molecules thanks plasma irradiation and dip-coating allows a large spectrum of functional groups and topographies controlling the surface properties like adhesion, wettability and biocompatibility. The grafting of mixtures of PNIPAM and CTAB or Tween 20 leads to a nano-structure polypropylene surface.Display Omitted► New polymeric surfaces having controlled physicochemical properties. ► New polymeric surfaces composed of mixtures of polymers and surfactant molecules. ► New polymeric surfaces with a topographic organization (nano-structuration). ► Simple elaboration routs of these new surfaces thanks plasma and coating technics.The surface grafting of multi-polymeric materials can be achieved by grafting as components such as polymers poly(N-isopropylacrylamide) and/or surfactant molecules (hexatrimethylammonium bromide, polyoxyethylene sorbitan monolaurate). The chosen grafting techniques, i.e. plasma activation followed by coating, allow a large spectrum of functional groups that can be inserted on the surface controlling the surface properties like adhesion, wettability and biocompatibility. The grafted polypropylene surfaces were characterized by contact angle analyses, XPS and AFM analyses. The influence of He plasma activation, of the coating parameters such as concentrations of the various reactive agents are discussed in terms of hydrophilic character, chemical composition and morphologic surface heterogeneity. The plasma pre-activation was shown inevitable for a permanent polymeric grafting. PNIPAM was grafted alone or with a mixture of the surfactant molecules. Depending on the individual proportion of each component, the grafted surfaces are shown homogeneous or composed of small domains of one component leading to a nano-structuration of the grafted surface.
Keywords: Polymer; Surfactant; Grafting; Plasma; PNIPAM; Nano-structuration
Defect induced photoluminescence and ferromagnetic properties of bio-compatible SWCNT/Ni hybrid bundles
by Vinay Gupta; Bipin Kumar Gupta; R.K. Kotnala; T.N. Narayanan; Vaneet Grover; Jyoti Shah; Vikash Agrawal; Suresh Chand; Virendra Shanker (pp. 311-316).
Demonstration of highly desirable bio-compatible SWCNT/Ni hybrid bundles with ferromagnetic as well as defect induced photoluminescence properties. .Display Omitted► The motivation of the present work is the realization of magnetic, luminescent and biocompatible structured nanostructures for possible biomedical applications.We could attain this goal. ► Moreover, a detailed mechanism is discussed in the manuscript for the observed interesting magnetic properties. ► The mechanism is verified using various experimental tools. ► A defect induced photoluminescence was observed and it is explained here in the manuscript with a detailed mechanism. ► Biocompatibility of the resultant structures is verified using standard assays. Such a novel and hybrid structure was not investigated so far in the literature according to the best of our knowledge.Designing of bio-compatible nanomagnets with multiple functionalities receives immense scientific attention due to their potential applications in bio-labeling, medical diagnosis and treatment. Here we report the synthesis of Nickel (Ni) incorporated single-walled carbon nanotube (SWCNT) hybrid and bio-compatible bundles having interesting magnetic and photoluminescence (PL) properties. The SWCNT exhibits a high-crystallinity and it has an average diameter of ∼1.7nm. Ni particles of 10–20nm were incorporated within the SWCNT bundles. These hybrid bundles exhibit PL and it is attributed to the presence of delocalized π electrons and their recombination at the defective sites of SWCNT. Magnetic characterization revealed that the SWCNT/Ni hybrid bundle possesses a high (50Oe) coercivity compared to bulk Ni and a long range ferromagnetic ordering at room temperature. MTT-assay has been conducted to study the cytotoxicity of these hybrid nanostructures.
Keywords: SWCNT; Nickel; Hybrid nanostructures; Photoluminescence; Ferromagnetic; Biocompatibility
Bio-dissolution of colloidal-size clay minerals entrapped in microporous silica gels
by Malgorzata Grybos; Patrick Billard; Sylvie Desobry-Banon; Laurent J. Michot; Jean-François Lenain; Christian Mustin (pp. 317-324).
A study of the bio-dissolution of size-selected anisotropic nontronite particles immobilized in a silica gel reveals that microbial dissolution of NAu-2 is dependant on the metabolism of bacteria rather than on the reactivity of mineral surfaces.Display Omitted► We examine how reactivity of mineral surfaces affects microbial dissolution. ► We use of size-selected anisotropic minerals (NAu-2) to vary surface reactivity. ► Bio-dissolution of NAu-2 seems to be controlled by bacterial metabolism. ► Silica gels as original approach for studying mineral–bacteria interactions.Four colloidal-size fractions of strongly anisotropic particles of nontronite (NAu-2) having different ratios of basal to edge surfaces were incubated in the presence of heterotrophic soil bacteria to evaluate how changes in mineral surface reactivity influence microbial dissolution rate of minerals. To avoid any particle aggregation, which could change the reactive surface area available for dissolution, NAu-2 particles were immobilized in a biocompatible TEOS-derived silica matrix. The resulting hybrid silica gels support bacterial growth with NAu-2 as the sole source of Fe and Mg. Upon incubation of the hybrid material with bacteria, between 0.3% and 7.5% of the total Fe included in the mineral lattice was released with a concomitant pH decrease. For a given pH value, the amount of released Fe varied between strains and was two to twelve-fold higher than under abiotic conditions. This indicates that complexing agents produced by bacteria play an important role in the dissolution process. However, in contrast with proton-promoted NAu-2 dissolution (abiotic incubations) that was negatively correlated with particle size, bacterial-enhanced dissolution was constant for all size fractions used. We conclude that bio-dissolution of nontronite particles under acidic conditions seems to be controlled by bacterial metabolism rather than by the surface reactivity of mineral.
Keywords: Microbial dissolution; Phyllosilicates; Surface reactivity; Colloids
Dense aqueous colloidal gold nanoparticles prepared from highly concentrated precursor solution
by Tetsuro Soejima; Seisaku Oshiro; Yasuji Nakatsuji; Seishiro Ito (pp. 325-329).
Gold and silver nanoparticle powders protected by casein proteins from milk are prepared from highly concentrated precursor solutions. Highly concentrated, stable colloidal metal nanoparticles are obtained by dissolving the powders in aqueous solution.Display Omitted► Casein protein emerges as a novel protective agent for metal nanoparticles. ► A highly concentrated synthetic route to Au and Ag nanoparticle powder is developed. ► Highly stable dense metal nanoparticle colloids is obtained by dissolving the powders. ► The conformational structures of the proteins change during the growth of the nanoparticles.Gold nanoparticles were fabricated by reduction of highly concentrated Au(III) ions (200mM) with casein proteins from milk. The gold nanoparticles were converted to nanoparticle-powders after washing and subsequent vacuum drying without aggregation. The nanoparticle-powders completely re-dispersed in aqueous solution, and stable colloidal gold nanoparticles were obtained. UV–vis extinction spectra and dynamic light scattering (DLS) measurements revealed that large assemblies (size, ca. 3μm) and subaggregates (size, <0.5μm) composed of gold nanoparticle–casein protein chain–Au(III) ion were dynamically formed and disintegrated over the course of the growth of the gold nanoparticles. Fourier transform infrared (FT-IR) spectra indicated conformational changes of casein proteins induced by the interaction of casein protein–Au(III) ion and -gold nanoparticle. Finally, rapid, one-pot, and highly concentrated synthetic procedures of gold and silver nanoparticle powders protected by casein (mean diameters below 10nm) were successfully developed using 3-amino-1-propanol aqueous solutions as reaction media. Dense colloidal gold (40gL−1) and silver (22gL−1) nanoparticle aqueous solutions were obtained by re-dispersing the metal nanoparticle powders.
Keywords: Gold nanoparticles; Silver nanoparticles; Inorganic synthesis; Casein
Submicrometer intermediates in the citrate synthesis of gold nanoparticles: New insights into the nucleation and crystal growth mechanisms
by Yuri Mikhlin; Anton Karacharov; Maxim Likhatski; Tatyana Podlipskaya; Yan Zubavichus; Alexey Veligzhanin; Vladimir Zaikovski (pp. 330-336).
Submicrometer “dense” liquid domains and aggregates of globules about 30nm in diameter are found as intermediates in the citrate synthesis of gold nanoparticles.Display Omitted► Liquid domains and globules 30–50nm in diameter are found as intermediates by AFM. ► DLS shows abrupt appearance of species about 30nm and larger. ► Growing Au nanoparticles are confined within aggregated globules. ► Colors of the reaction solutions are due to interparticle distances.The reduction of tetrachloroaurate by citrate ions in aqueous solutions yielding gold nanoparticles (GNPs) has been studied using in situ tapping mode atomic force microscopy (AFM), UV–vis absorption and dynamic light scattering (DLS) spectroscopies, small-angle X-ray scattering (SAXS) along with ex situ TEM, EDX and XPS. Special attention is given to mesoscale intermediates responsible for the intense coloring of the transient solutions and their role in nucleation and crystal growth. AFM detects liquid droplet-like domains, globules 30–50nm in diameter arranged in submicrometer aggregates in the gray and blue solutions, and well separated individual particles in the final red sols. DLS shows abrupt appearance of species about 30nm and larger but not growing Au nanoparticles, while SAXS reveals gradually increasing nanoparticles and no aggregates. The mesoscale structures observed in TEM become looser as the reaction proceeds; they contain signatures of oxidized Au and other solutes. The results are interpreted in terms of decomposition of supersaturated solutions to afford domains (“dense droplets”) enriched by gold, and then, after nucleation and coalescence of Au nuclei inside them, rather slow growth of gold nanoparticles within the associated globules; the color changes of the transient solutions are due to increasing interparticle distances.
Keywords: Gold nanoparticles; Citrate reduction; Mechanism; Liquid intermediates; In situ; AFM; Dynamic light scattering; Small-angle X-ray scattering
Functionalization of tungsten oxide into MWCNT and its application for sunlight-induced degradation of rhodamine B
by Tawfik A. Saleh; Vinod K. Gupta (pp. 337-344).
Schematic representation of MWCNT/WO3 composite.Display Omitted► Synthesis of multiwall carbon nanotube/tungsten oxide composite. ► Photocatalytic performance is enhanced by functionalized composite. ► MWCNTs acts as dispersing agent and controls the morphology of catalyst. ► Method has the potential as technology for environmental purification.A composite of multi-walled carbon nanotube/tungsten oxide (MWCNT/WO3) has been successfully synthesized. The prepared composite was characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR). The catalytic activity was investigated by rhodamine B degradation under solar irradiation. The influence of various degradation parameters such as solar illumination time, initial dye concentration, dosage and pH was investigated. It was found that the composite exhibits an enhanced photocatalytic activity as compared with WO3 and a mechanical mixture of MWCNTs and WO3. The enhancement in photocatalytic performance of the MWCNT/WO3 composite has been explained based on adsorption ability and electron transportation as a result of a strong interaction between WO3 and MWCNTs. Besides, MWCNTs acts as dispersing agent preventing WO3 from agglomerating during the catalytic process, providing a high active surface area of the catalyst. A reasonable mechanism for the enhanced reactivity was proposed.
Keywords: Multi-walled carbon nanotube; Tungsten oxide; Rhodamine B; Degradation
Reaction-induced phase separation of bis(triethoxysilyl)ethane upon sol–gel polymerization in acidic conditions
by Jyothirmai Ambati; Stephen E. Rankin (pp. 345-353).
Illustration of how partial hydrolysis of bis(triethoxysilyl)ethane can produce an amphiphilic compound which subsequently undergoes aggregation. This extreme example illustrates the type of phenomenon proposed to be responsible NMR signal loss during polymerization of bis(triethoxysilane) under some conditions.Display Omitted► Phase behavior of ethanol/(acidic) water/bis(triethoxysilyl)ethane system established. ► Phenomenon of slow NMR signal loss observed for some clear solutions. ► NMR signal loss attributed to microphase separation of partially hydrolyzed oligomers. ► Results may be related to microphase separation observed in other silane-based materials.While organically bridged alkoxysilane precursors such as bis(triethoxysilyl)ethane (BTESE) find increasing use in materials synthesis, their polymerization still has not been subject to detailed kinetic investigations. One factor complicating the measurement and interpretation of the behavior of these monomers is their tendency to aggregate during polymerization into small clusters or particles. Here, the phase behavior and kinetics of BTESE during polymerization in acidic water–ethanol solutions are investigated in situ using29Si NMR spectroscopy. Based on macroscopic observation of the colloidal stability of the reacting solutions, a ternary pseudo-phase diagram is constructed and solutions that seem from a macroscopic point of view to be favorable for kinetic investigation are probed in situ using29Si NMR. However, even when the solutions remain optically clear, the polymerization mixtures are sometimes prone to gradual loss of NMR signal. The rate of signal loss is found to be dependent on the initial composition as well as the pH of the reacting mixtures. We speculate that this phenomenon is caused by microphase separation of reaction intermediates formed early in the polymerization process. This phenomenon is likely to affect the formation and distribution of oligomers in the solution that eventually react together to form a material.
Keywords: Organoalkoxysilane; Sol–gel polymerization; NMR; Signal loss; Microphase separation; Alkoxysilane; Bridged; Polymerization; In situ
Mesoporous silica SBA-15 sheet with perpendicular nanochannels
by Yi-Qi Yeh; Hong-Ping Lin; Chih-Yuan Tang; Chung-Yuan Mou (pp. 354-366).
The proper interplay between C16TMAB/SDS bilayers (confined walls) and P123/silicate (polymer segments) determines the formation of SBA-15 sheet with perpendicular nanochannels and open-ended pore structure.Display Omitted► SBA-15 thin sheet with perpendicular nanochannels was synthesized in confined space of vesicle. ► The ends of the channels are open and the channel length is uniform in the range of 60–300nm. ► The thickness and orientation of the mesostructure show pH and temperature-dependence. ► Orientation controls of the pores in SBA-15 are analyzed with modern theory of assembly of block-copolymer.Free-standing thin sheet form of mesoporous silica materials with perpendicular orientation is a much desired materials for its possible applications in catalysis, mask, and separation. A three component amphiphile system of sodium dodecyl sulfate/hexadecyltrimethylammonium bromide/pluronic-123(C16TMAB/SDS/P123) was employed to template the condensation of sodium silicates for the formation of SBA(⊥), a thin sheet of SBA-15 with perpendicular nanochannels. SBA(⊥) can be synthesized at SDS/C16TMAB=1.5 and T⩾40°C and shows pH-dependent morphology. It has uniform pore size ∼9nm, homogeneous sheet thickness in the range of 60–300nm and dimension of several microns. We studied in details the structure and morphology of the SBA(⊥) with variation of three experimental parameters: the SDS/C16TMAB ratio, the temperature, and the pH condition in the synthetic gel. It is proposed that the mixed surfactants of SDS and C16TMAB form catanionic vesicle in which the P123 and silicates are condensed. The balanced interaction of P123/silicate with the narrow confinement under surfactant bi-layers of C16TMAB/SDS promoted the formation of perpendicular nanochannels. Low temperature and pH conditions favor stronger segregation of the PPO and PEO–oligosilicate segments in the SBA(⊥) structure which gives the basis of thickness control of the sheet. The control of structure and morphology are discussed with modern theory of microphase separation in block copolymers under confinement.
Keywords: SBA-15; Thin sheet; Mesopore orientation; Silica deposition vesicle; Sodium dodecyl sulfate; SDS; Hexadecyltrimethylammonium bromide; CTMAB; Pluronic-123
Electrophoretic deposition of polyacrylic acid and composite films containing nanotubes and oxide particles
by Y. Wang; I. Deen; I. Zhitomirsky (pp. 367-374).
A method is presented for the electrophoretic deposition of polyacrylic acid and composite films, containing multiwalled carbon nanotubes, hollow halloysite nanotubes, MnO2, NiO, TiO2 and SiO2 in polyacrylic acid matrix.Display Omitted► Polyacrylic acid polymer films were prepared by electrophoretic deposition. ► Polymer-multiwalled carbon and polymer-halloysite nanotube films were obtained. ► Composite films containing MnO2, NiO, TiO2, SiO2 in polymer matrix were obtained. ► The deposition mechanism and kinetics of deposition were investigated. ► The film thickness and composition can be varied and controlled.Electrophoretic deposition (EPD) method has been developed for the deposition of thin films of polyacrylic acid (PAA). This method allowed the formation of uniform films of controlled thickness on conductive substrates. It was shown that PAA can be used as a common dispersing agent suitable for charging and EPD of various materials, such as multiwalled carbon nanotubes, halloysite nanotubes, MnO2, NiO, TiO2 and SiO2. The feasibility of EPD of composite films containing the nanotubes and oxide particles in a PAA matrix has been demonstrated. The kinetics of deposition and deposition mechanisms were investigated and discussed. The films were studied by thermogravimetric analysis, differential thermal analysis, X-ray diffraction and scanning electron microscopy. The results indicated that film thickness and composition can be varied. Obtained results pave the way for the fabrication of PAA and composite films for biomedical, electrochemical and other applications.
Keywords: Electrophoretic deposition; Carbon nanotube; Halloysite nanotube; Polyacrylic acid; Film; Oxide
Creation of coating surfaces possessing superhydrophobic and superoleophobic characteristics with fluoroalkyl end-capped vinyltrimethoxysilane oligomeric nanocomposites having biphenylene segments
by Yuki Goto; Hiroki Takashima; Katsuhisa Takishita; Hideo Sawada (pp. 375-381).
Creation of superhydrophobic and superleophobic surface with fluorinated oligomeric nancomposites.Display Omitted► Fluorinated vinyltrimethoxysilane oligomeric nanocomposites having biphenylene units can be applicable to the surface modification. ► The modified surface can exhibit not only a good oleophobicity imparted by fluorine but also a fluorescent emission ability. ► Fluorinated nanocomposites can exhibit both superhydrophobic and superleophobic characteristics on the modified surface.Fluoroalkyl end-capped vinyltrimethoxysilane oligomeric nanocomposites having biphenylene units [RF-(VM-SiO2) n-RF/Ar-SiO 2] were prepared by the sol–gel reaction of the corresponding oligomer [RF-(VM) n-RF] with 4,4′-bis(triethoxysilyl)-1,1′-biphenyl [Ar-Si(OEt) 3] under alkaline conditions. RF-(VM-SiO2) n-RF/Ar-SiO 2 nanocomposites were applied to the surface modification of PMMA to exhibit not only a good oleophobicity imparted by fluorine but also a fluorescent emission ability on the surface. Methanol sol solutions of RF-(VM-SiO2) n-RF/Ar-SiO 2 nanocomposites were effective for the surface modification of glass through the dipping technique to exhibit good oleophobicity with superhydrophobicity on the modified glass surface. On the other hand, 1,2-dichloroethane sol solutions enabled RF-(VM-SiO2) n-RF/Ar-SiO 2 nanocomposites to exhibit both superhydrophobic and superoleophobic characteristics on the modified surface through dipping the glass in these sol solutions.
Keywords: Superhydrophobicity; Superoleophobicity; Surface modification; Fluorinated oligomer; Organic-bridged silica; Silica nanocomposite; Contact angle; Fluorescent emission; DFM; FE-SEM
Solvation forces between molecularly rough surfaces
by Kan Yang; Yangzheng Lin; Xiancai Lu; Alexander V. Neimark (pp. 382-388).
Solvation pressures at P/ P0=1 as a function of the pore width for pore walls of different roughness. The curves are shifted by 100MPa. No oscillations of solvation pressure when the roughness parameter exceeds 0.37 σff (0.13nm).Display Omitted► A QSDFT study of the effects of surface roughness on the solvation pressure. ► The surface roughness effectively damps the oscillations of solvation pressure. ► The LJ model of nitrogen sorption at 74.4K in slit-shaped carbon nanopores is used.Surface heterogeneity affects significantly wetting and adhesion properties. However, most of the theories and simulation methods of calculating solid–fluid interactions assume a standard thermodynamic model of the Gibbs’ dividing solid–fluid interface, which is molecularly smooth. This assumption gives rise to a layering of the fluid phase near the surface that is displayed in oscillating density profiles in any theories and simulation models, which account for the hard core intermolecular repulsion. This layering brings about oscillations of the solvation (or disjoining) pressure as a function of the gap distance, which are rarely observed in experiments, except for ideal monocrystal surfaces. We present a detailed study of the effects of surface roughness on the solvation pressure of Lennard-Jones (LJ) fluids confined by LJ walls based on the quenched solid density functional theory (QSDFT). In QSDFT, the surface roughness is quantified by the roughness parameter, which represents the thickness of the surface “corona” – the region of varying solid density. We show that the surface roughness of the amplitude comparable with the fluid molecular diameter effectively damps the oscillations of solvation pressure that would be observed for molecularly smooth surfaces. The calculations were done for the LJ model of nitrogen sorption at 74.4K in slit-shaped carbon nanopores to provide an opportunity of comparing with standard adsorption experiments. In addition to a better understanding of the fundamentals of fluid adsorption on heterogeneous surfaces and inter-particle interactions, an important practical outcome is envisioned in modeling of adsorption-induced deformation of compliant porous substrates.
Keywords: Solvation pressure; Surface roughness; QSDFT; Adsorption and Adhesion
Controllable synthesis and up-conversion properties of tetragonal BaYF5:Yb/Ln (Ln=Er, Tm, and Ho) nanocrystals
by Na Niu; Piaoping Yang; Yanchao Liu; Chunxia Li; Dong Wang; Shili Gai; Fei He (pp. 389-396).
Luminescent BaYF5:Yb/Ln (Ln=Er, Tm, Ho) nanocrystals with different morphology and structure were successfully synthesized via a facile hydrothermal process.Display Omitted► A facile and effective hydrothermal route was used to fabricate fluorescent nanocrystals. ► Uniform nanocrystals with spherical morphology and excellent up-conversion properties were obtained. ► The possible formation scheme for the nanocrystals prepared at different conditions is presented.The nanocrystals (NCs) of tetragonal barium yttrium fluoride (BaYF5) doped 1mol% Ln3+ (Ln=Er, Tm, Ho) and 20mol% Yb3+ with different morphologies and sizes have been successfully synthesized through a facile hydrothermal method. The influences of pH values of the initial solution and fluorine sources on the final structure and morphology of the products have been well investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the size, structure and morphology of these samples prepared at different conditions. And it is found that BaYF5:Yb/Ln NCs prepared at pH value of 10 using NaBF4 as F− source have a uniform spherical morphology with average diameter of 25nm. Additionally, the up-conversion (UC) properties of Yb/Er, Yb/Tm, and Yb/Ho doped BaYF5 nanoparticles were also discussed. Under 980nm laser excitation, the BaYF5:Yb/Er, BaYF5:Yb/Tm, and BaYF5:Yb/Ho NCs exhibit green, whitish blue, and yellow green UC luminescence, respectively. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.
Keywords: Hydrothermal synthesis; Nanocrystals; Up-conversion
Adsorption of multilamellar tubes with a temperature tunable diameter at the air/water interface
by Anne-Laure Fameau; Jean-Paul Douliez; François Boué; Frédéric Ott; Fabrice Cousin (pp. 397-405).
Multilamellar tubes of the 12-hydroxy stearic acid adsorb at the air/water interface. The structure at the interface can be tuned by the temperature.Display Omitted► Multilamellar tubes of the ethanolamine salt of 12-hydroxy stearic acid adsorb at the air/water interface. ► Similarly to what has been observed in bulk, the tubes have a temperature tunable diameter at the interface. ► All structural transitions at the interface display reversibility. ► The structure at the air/water interface can be tuned easily by temperature.The ethanolamine salt of 12-hydroxy stearic acid is known to form tubes having a temperature tunable diameter. Here, we study the behavior of those tubes at the air/water interface by using Neutron Reflectivity. We observed that tubes indeed adsorbed at this interface below a fatty acid monolayer and exhibit the same temperature behavior as in bulk. There is however a peculiar behavior at around 50°C for which the increase of the diameter of the tubes at the interface yields an unfolding of those tubes into a multilamellar layer. Upon further heating, the tubes re-fold and their diameter re-decreases after which they melt into micelles as observed in the bulk. All structural transitions at the interface are nevertheless reversible. This provides to the system a high interest for its interfacial properties because the structure at the air/water interface can be tuned easily by the temperature.
Keywords: Hydroxy fatty acid; Multilamellar tubes; Air/water interface; Neutron Reflectivity
Synthesis, aggregation behavior and interfacial activity of branched alkylbenzenesulfonate gemini surfactants
by Qun Zhang; Maozhang Tian; Yuchun Han; Chunxian Wu; Zhibo Li; Yilin Wang (pp. 406-414).
Three branched alkylbenzenesulfonate gemini surfactants were synthesized, and spherical vesicles were observed in the surfactant solutions. The increase in the branching factor leads to much more endothermic enthalpy of aggregation.Display Omitted► Three branched alkylbenzenesulfonate gemini surfactants have been synthesized. ► Alkyl side branches generate significant increases in CAC and Amin. ► The branching factor does not change the air/water surface tension regularly. ► The surfactants display high efficiency in reducing toluene/water interfacial tension. ► These branched gemini surfactants form spherical vesicles in aqueous solution.Branched alkylbenzenesulfonate gemini surfactants: sodium 6,6′-(propane-1,3-diylbis(oxy))bis(3-(2-propylpentyl)benzenesulfonate) (C8BC3C8B), sodium 6,6′-(propane-1,3-diylbis(oxy))bis(3-(3,5,5-trimethylhexyl)benzenesulfonate) (C9BC3C9B), and sodium 6,6′-(propane-1,3-diylbis(oxy))bis(3-(2,4,4-trimethylpentan-2-yl)benzenesulfonate) (T-C8BC3C8B) have been synthesized. Their interfacial activity and aggregation behavior in aqueous solution were studied by surface/interface tension measurement, electrical conductivity, isothermal titration microcalorimetry,1H NMR spectroscopy, dynamic light scattering, steady-state fluorescence and cryogenic transmission electron microscopy. The critical aggregation concentration (CAC) and the minimum average surface area/molecule ( Amin) decrease with the decrease of the branching factor, i.e., in the order of T-C8BC3C8B, C8BC3C8B and C9BC3C9B. Moreover, alkyl side chain branches generate much more significant increases in CAC and Amin for the gemini surfactants than single-chain surfactants. However, the branching factor does not change the air/water surface tension at CAC regularly. Instead, the air/water surface tension decreases with the increase of the carbon number of the hydrocarbon chains. In addition, it is noted that the branched gemini surfactants display high efficiency in reducing toluene/water interfacial tension. Interestingly, the increase in the branching factor leads to much more endothermic enthalpy of aggregation. All these three surfactants form spherical vesicles in aqueous solution and may present a parallel-displaced structure with a directional arrangement of the benzene ring in the vesicles.
Keywords: Gemini surfactants; Branched surfactants; Interfacial tension; Vesicle
Influence of the Hofmeister anions on self-organization of 1-decyl-3-methylimidazolium chloride in aqueous solutions
by Justyna Łuczak; Marta Markiewicz; Jorg Thöming; Jan Hupka; Christian Jungnickel (pp. 415-422).
Conductivity and ITC have been used to study the effect of salts on aggregation of [DMIM][Cl] in aqueous solutions. The salts decreased the CMC and micelle ionization in the order of Cl−
−−.Display Omitted► Micelle formation of an IL with K+ salts was investigated with conductivity and calorimetry. ► Effect of concentration, nature of the anion and temperature on micelle formation were studied. ► CMC and degree of micelle ionization were influenced by salts in the order of Cl−
−−.Inorganic salts usually influence water structure affecting the hydration of the molecules which lead to a salting-in or a salting-out effect of hydrophobic compounds. Specific conductivity and isothermal titration calorimetry have been used to study the effect of inorganic salts on aggregation of the cationic surfactant 1-decyl-3-methylimidazolium chloride in aqueous solutions. The effect of the concentration, the nature of the anion and temperature on micelle formation were studied.A decreasing critical micelle concentration (CMC) due to the weakening electrostatic repulsion between the headgroups was observed. The salts used in this investigation decreased the CMC and degree of micelle ionization in the order of Cl−
−− which parallels the Hofmeister series of ions. The effect of the electrolyte concentration on the CMC, and a relationship between the electrolyte counter-ion concentration and the CMC were also shown.
Keywords: Self-organization; Micelle formation; Imidazolium ionic liquids; Inorganic salt influence; Hofmeister
Influence of surfactant amphiphilicity on the phase behavior of IL-based microemulsions
by Agnes Harrar; Oliver Zech; Angelika Klaus; Pierre Bauduin; Werner Kunz (pp. 423-429).
IL-based “cold” microemulsions have been studied in order to determine the effect of surfactant amphiphilicity on these ternary systems.Display Omitted► “Cold” microemulsions have been formulated and investigated. ► Microemulsions with IL as continuous phase do not phase separate down to −35°C. ► A general concept for the formulation of “cold” microemulsions is proposed.In this work, we report on the phase behavior of 1-ethyl-3-methyl-imidazolium-ethylsulfate ([emim][etSO4])/limonene/polyethylene glycol tert-octylphenyl ether (Triton X-114 or TX-114) microemulsions as a function of ionic liquid (IL) content and temperature. Phase diagrams, conductivity measurements, and small angle X-ray scattering (SAXS) experiments will be presented. A hydrophilic IL, instead of water is used with the goal to enlarge the temperature range on which stable microemulsions can be formed. Indeed, the system shows remarkably large temperature stability, in particular down to −35°C. We will emphasize on a comparison with a recently published work about microemulsions composed of [emim][etSO4], limonene, and Triton X-100 that to some extent are stable at temperatures well below the freezing point of water. The key parameter responsible for the difference in phase behavior, microstructure, and temperature stability is the average repeating number of ethylene oxide units in the surfactant head group, which is smaller for Triton X-114 compared to Triton X-100. Among the fundamental interest, how the amphiphilicity of the surfactant influences the phase diagram and phase behavior of IL-based microemulsions, the exchange of Triton X-100 by Triton X-114 results in one main advantage: along the experimental path the temperature where phase segregation occurs is significantly lowered leading to single phase microemulsions that exist at temperatures beneath 0°C.
Keywords: Low temperatures; Ionic liquid; Microemulsion; “Fish”-cut; SAXS; Surfactant amphiphilicity
Light and host–guest inclusion mediated salmon sperm DNA/surfactant interactions
by Yiyang Lin; Yudong Zhang; Yan Qiao; Jianbin Huang; Baocai Xu (pp. 430-438).
Light input and host–guest inclusion controlled DNA complexation by a novel cationic surfactant is reported.Display Omitted► Azobenzene-derived cationic surfactant (AzoC6Mim) is synthesized. ► Cationic surfactant AzoC6Mim can be used to compact salmon sperm DNA. ► AzoC6Mim/DNA complexation can be regulated by light or host–guest interaction.DNA/cationic surfactant interaction is relevant from the viewpoint of gene therapy, where the complexation and resulting compaction are essential to protect DNA from nuclease, and to allow entry of DNA into cells. In this work, light input and host–guest inclusion controlled DNA complexation by a novel cationic surfactant 1-[6-(4-phenylazo-phenoxy)-hexyl]-3-methylimidazolium bromide (AzoC6Mim) is reported. The surfactant is covalently attached with an azobenzene group, which undergoes reversible photoisomerizations by changing light input. Under visible light, trans-AzoC6Mim can bind to salmon sperm DNA through electrostatic attraction and hydrophobic interaction, resulting into DNA compaction. Under UV light, although cis-AzoC6Mim still binds to DNA chain, DNA/surfactant complex is decompacted owing to the decrease of surfactant hydrophobicity. On the other hand, azobenzene group can form an inclusion complex with α-CD through host–guest interaction, which removes AzoC6Mim from DNA chain and decompacts the DNA/surfactant complex.
Keywords: DNA complexation; Surfactant; Light; Host–guest interaction; Azobenzene
Interrelations between charging, structure and electrokinetics of nanometric polyelectrolyte films
by Jérôme F.L. Duval; David Küttner; Mirko Nitschke; Carsten Werner; Ralf Zimmermann (pp. 439-449).
Interrelations between charging and structure of plasma-immobilized poly(acrylic acid) (PAA) and poly(ethylene imine) (PEI) thin-films are derived and discussed on the basis of theory for electrohydrodynamics of diffuse soft interfaces.Display Omitted► Charging and structure of plasma-immobilized polyelectrolyte films were analyzed. ► Swelling of PAA films is accompanied by an increase in interfacial diffuseness. ► The segment density distribution is nearly independent on pH for PEI films. ► Limitations of electrokinetics for analyzing interfacial structure are discussed.Streaming current, surface conductivity and swelling data of poly(acrylic acid) (PAA) and poly(ethylene imine) (PEI) thin films are analyzed on the basis of the theory for diffuse soft interfaces (J.F.L. Duval, R. Zimmermann, A.L. Cordeiro, N. Rein, C. Werner, Langmuir 25 (2009) 10691). Focus is put on ways to unravel the electroosmotic and migration contributions of the measured surface conductivity, which is crucial for appropriate electrokinetic analysis of films carrying high densities of dissociable groups. Results demonstrate that the osmotically-driven swelling of the PAA films with increasing pH is accompanied by an increase in diffuseness for the interphasial polymer segment density distribution. This heterogeneity is particularly marked at low ionic strength with a non-monotonous dependence of the streaming current on pH and the presence of a maximum at pH∼6.5. The analysis of the PEI films evidences heterogeneous swelling with lowering pH, i.e. upon protonation of the amine groups. The characteristic decay length in the interphasial PEI segment density distribution is found to be nearly independent of the pH, which is in line with the moderate swelling determined by ellipsometry. A critical discussion is given on the strengths and limitations of electrokinetics/surface conductivity for quantifying the coupled electrohydrodynamic and structural properties of moderately to highly swollen polyelectrolyte thin films.
Keywords: Soft surface electrokinetics; Polyelectrolyte layers; Interfacial charge formation; Streaming current; Surface conductivity
Preparation, characterization and application in deep catalytic ODS of the mesoporous silica pillared clay incorporated with phosphotungstic acid
by Baoshan Li; Zhenxing Liu; Jianjun Liu; Zhiyuan Zhou; Xiaohui Gao; Xinmei Pang; Huiting Sheng (pp. 450-456).
A facile method was reported to prepare as-synthesized mesoporous silica pillared clay materials with HPW heteropoly acid encapsulated into the framework, which exhibited high and stable activity in deep oxidative desulfurization.Display Omitted► HPW heteropoly acid encapsulated into the mesoporous SPC. ► HPW was dispersed homogeneously in the HPW-SPC-SG samples. ► HPW-SPC-SG samples showed better catalytic performance than HPW-SPC-IM samples. ► HPW-SPC-SG catalysts exhibited good reusability.Mesoporous silica pillared clay (SPC) materials with different contents of H3PW12O40 (HPW) heteropoly acid were synthesized by introducing HPW into clay interlayer template in an acidic suspension using sol–gel method. Samples with similar HPW loadings were also prepared by impregnation method using SPC as the support. The results of the characterizations showed that HPW was dispersed more homogeneously in the encapsulated samples than in the impregnated samples. The encapsulated materials exhibited better catalytic performance than the impregnated samples in oxidative desulfurization of dibenzothiophene-containing model oil. The sulfur removal reached up to 98.6% for the model oil under the experiential conditions.
Keywords: Phosphotungstic acid; Mesoporous silica pillared clay; Montmorillonite; Catalytic oxidative desulfurization
Adsorption process of methyl orange dye onto mesoporous carbon material–kinetic and thermodynamic studies
by Nourali Mohammadi; Hadi Khani; Vinod Kumar Gupta; Ehsanollah Amereh; Shilpi Agarwal (pp. 457-462).
pH and salt effect on the removal of methyl orange dye.Display Omitted► The prepared CMK-3 is a good replica of its template SBA-15. ► Adsorption process was fast enough, and 60min contact time is sufficient. ► CMK-3 is an excellent adsorbent for dye removal. ► It is a good replacement of commercially available carbons.The mesoporous carbon CMK-3 adsorbent was prepared, characterized, and used for the removal of anionic methyl orange dye from aqueous solution. Adsorption experiments were carried out as batch studies at different contact time, pH, initial dye concentration, and salt concentration. The dye adsorption equilibrium was rapidly attained after 60min of contact time. Removal of dye in acidic solutions was better than in basic solutions. The adsorption of dye increased with increasing initial dye concentration and salt concentration. The equilibrium data were analyzed by the Langmuir and Freundlich models, which revealed that Langmuir model was more suitable to describe the methyl orange adsorption than Freundlich model. Experimental data were analyzed using pseudo-first-order and pseudo-second-order kinetic models. It was found that kinetics followed a pseudo-second-order equation. Thermodynamic study showed that the adsorption was a spontaneous and exothermic process.
Keywords: CMK-3; Adsorption; Methyl orange; Kinetics; Thermodynamics
Adsorption of several gases on flexible metal organic framework [Cu(dhbc)2(4,4′-bpy)]·H2O
by Tatsuya Yamazaki; Yoshihiko Takahashi; Daisuke Yoshida (pp. 463-469).
The adsorption isotherms for methane on flexible MOFs can be generalized to a characteristic curve using the adsorption potential energy ( ε) and the adsorption volume.Display Omitted► Adsorption isotherms on Cu(db) were generalized to a characteristic curve using ε. ► The gate pressures of gases can be deduced using εgate. ► Gate effect is governed by interaction energy between adsorbent and adsorbate.The adsorption of ten gases on the flexible metal organic framework material [Cu(dhbc)2(4,4′-bpy)]·H2O (Cu(db)) has been measured over a wide range of temperatures and pressures. The gate opening condition and driving force behind gate adsorption for Cu(db) were discussed by examining the adsorption isotherms. The adsorption isotherms for each adsorbate can be generalized to a characteristic curve using the adsorption potential energy ( ε) and the adsorption volume. The adsorption potential ( εgate) at gate opening is almost constant over a wide range of temperatures; thus, the gate pressure at a desired temperature can be deduced using the εgate evaluated from one adsorption isotherm. The gate opening capacity of the gases was arranged in the order: CO2≒N2O>C2H4≒Xe>CH4>CO>O2>Ar≒N2>H2, which is governed by the interaction energy between the outer surface of Cu(db) and the adsorbate. It is suggested that the gate effect is brought about when the integral interaction energy of adsorbates with the Cu(db) surface exceeds a defined limit correlating with the π−π stacking energy of Cu(db) layers.
Keywords: Flexible metal organic framework; Gas adsorption; Gate effect; Adsorption potential energy
Synthesis and photocatalytic activity of TiO2 nanoparticles prepared by chemical vapor condensation method with different precursor concentration and residence time
by Sungmin Chin; Eunseuk Park; Minsu Kim; Gwi-Nam Bae; Jongsoo Jurng (pp. 470-476).
Decreasing both the rates of coagulation and coalescence are instrumental in reducing the particle size, which can be achieved by reducing the precursor concentration and residence time.Display Omitted► The specific surface area (92.5–163.5 m2 g–1) of the CVC-prepared TiO2 powders depends on the synthesis conditions. ► The photocatalytic activity of the prepared TiO2 samples is strongly dependent on the crystallinity and SSA. ► The photocatalytic activities are in the order of 7.0TiO20.7 > 7.4TiO20.3 > 7.2TiO20.5 > 6.8TiO20.9 > P25TiO2.Nanosized TiO2 photocatalysts were synthesized using a chemical vapor condensation method under a range of synthesis conditions (precursor vapor concentration and residence time in a tubular electric furnace). X-ray diffraction showed that the prepared TiO2 powders consisted mainly of anatase (>94%) with a small amount of rutile. The mean particle diameter from the Brunauer–Emmett–Teller surface area and transmission electron microscopy measurements ranged from 9.4 to 16.6nm. The specific surface area (92.5–163.5m2g−1) of the prepared TiO2 powders was found to be dependent on the synthesis conditions. The content of hydroxyl groups on the surface of the prepared TiO2 sample was higher than those on commercial TiO2, resulting in increased photocatalytic oxidation. The photocatalytic activity of the TiO2 samples prepared in a methylene blue solution was strongly dependent on the crystallinity and specific surface area, which were affected by the TTIP vapor concentration and residence time.
Keywords: Chemical vapor condensation; TiO; 2; nanoparticle; Anatase; Crystallinity; Photocatalyst
Synthesis of 3D porous ferromagnetic NiFe2O4 and using as novel adsorbent to treat wastewater
by Xiangyu Hou; Jing Feng; Xiaohan Liu; Yueming Ren; Zhuangjun Fan; Tong Wei; Jian Meng; Milin Zhang (pp. 477-485).
3D porous NiFe2O4 was synthesized by sol–gel method. It showed excellent adsorption properties for organic dye and could be magnetic separated easily.Display Omitted► Porous NiFe2O4 was synthesized by a simple sol–gel method using egg white. ► The pore structure forming process was studied. ► Porous NiFe2O4 shows large adsorption capacity for organic dye and heavy metal ions. ► The ferromagnetic property of NiFe2O4 resulting in excellent magnetic separation.Three dimensions (3D) porous NiFe2O4 is synthesized by a sol–gel method using egg white. The obtained NiFe2O4 shows both good ferromagnetic properties and high adsorption capacity. The porous NiFe2O4 shows good adsorption properties for organic dyes (Methylene Blue (138.50mg/g), Fuchsine Red (14.61mg/g), Methyl Violet (19.06mg/g)) and heavy metal ions (Cu (II) (55.83mg/g), Cr (VI) (36.95mg/g) and Ni (II) (37.02mg/g)) due to its 3D interconnected porous structure. The maximum adsorption of Methylene Blue (MB) fit the pseudo-second-order model and Langmuir isotherm equation well. More interestingly, the ferromagnetic NiFe2O4 can be separated under a magnetic field conveniently and keeps high removal efficiency (>97%) during seven reusable cycles. These results suggest that the porous NiFe2O4 is a promising favorable and reusable adsorbent.
Keywords: NiFe; 2; O; 4; 3D pore; Ferromagnetism; Adsorption; Magnetic separation
Magnetic alginate beads for Pb(II) ions removal from wastewater
by Agnès Bée; Delphine Talbot; Sébastien Abramson; Vincent Dupuis (pp. 486-492).
Magnetic beads (magsorbent) of chitosan containing citrate-coated maghemite nanoparticles are efficiently used to remove Pb(II) ions from aqueous solution.Display Omitted► Green synthesis of a magsorbent based on alginate. ► Encapsulation of nanoparticles in alginate does not alter their magnetic properties. ► Magnetic alginate beads are efficient for the removal of Pb(II) ions (100mg/g). ► Adsorption of Pb(II) ions by the magsorbent is pH-dependent. ► The magsorbent could be reused after regeneration with HNO3 2mol/L.A magnetic adsorbent (called magsorbent) was developed by encapsulation of magnetic functionalized nanoparticles in calcium-alginate beads. The adsorption of Pb(II) ions by these magnetic beads was studied and the effect of different parameters, such as initial concentration, contact time and solution pH value on the adsorption of Pb(II) ions was investigated. Our magsorbent was found to be efficient to adsorb Pb(II) ions and maximal adsorption capacity occurred at pH 2.3–6. The classical Langmuir model used to fit the experimental adsorption data showed a maximum sorption capacity close to 100mgg−1. The experimental kinetic data were well correlated with a pseudo second-order model, 50% of the Pb(II) ions were removed within 20min and the equilibrium was attained around 100min. Moreover our magsorbent was easily collected from aqueous media by using an external magnetic field. These results permitted to conclude that magnetic alginate beads could be efficiently used to remove heavy metals in a water treatment process.
Keywords: Magnetic alginate beads; Ferrofluid; Adsorption; Pb(II); Magsorbent; Alginate
Near 100% selectivity in anion exchange reactions of layered zinc hydroxy nitrate
by Nygil Thomas; Michael Rajamathi (pp. 493-496).
The anion exchange reaction of zinc hydroxy nitrate is highly selective. When stirred in a mixture of halide ions, the hydroxysalt selectively intercalates fluoride ions. Chloride was selectively (94%) intercalated from a mixture of chloride, bromide and iodide.Display Omitted► Selective uptake of halide ions by zinc hydroxy nitrate observed. ► Selectivity order is F−>Cl−>Br−, I−. ► Selectivity for fluoride ions was 70% from a mixture of fluoride and chloride. ► Selectivity for chloride ions was 100% from a mixture of chloride and bromide. ► Selectivity observed here is different from what has been observed in LDHs.The anionic clay, zinc hydroxy nitrate was found to selectively intercalate fluoride ions from a mixture of halide ions and chloride ions from a mixture of chloride, bromide and iodide ions. In a binary mixture of chloride and bromide ions, the selectivity for chloride ions was very high (94%) even when the bromide concentration was eight times in excess. The selectivity was achieved in both concentrated and dilute salt solutions. The trend in selectivity observed here is different from what has been observed for layered double hydroxides.
Keywords: Anionic clay; Layered hydroxy salt; Intercalation; Selective anion exchange; Separation of halide ions
Kinetics and equilibrium studies on the treatment of nitric acid with Mg–Al oxide obtained by thermal decomposition ofNO3--intercalated Mg–Al layered double hydroxide
by Tomohito Kameda; Yuki Fubasami; Toshiaki Yoshioka (pp. 497-502).
Proposal for the treatment of HNO3 using Mg–Al oxide.Display Omitted► Mg–Al oxide could treat HNO3, acting as both a neutralizer and fixative forNO3-. ► TheNO3- removal increased with time, Mg–Al oxide quantity and temperature. ► TheNO3- removal by Mg–Al oxide proceeded under chemical reaction control. ► The adsorption isotherm could be expressed by Langmuir type.Mg–Al oxide obtained by thermal decomposition ofNO3--intercalated Mg–Al layered double hydroxide (NO3·Mg–Al LDH) was found to treat HNO3, acting as both a neutralizer and fixative forNO3-. The degree ofNO3- removal increased with time, Mg–Al oxide quantity, and temperature. TheNO3- removal could be represented by a first-order reaction. The apparent activation energy was 52.9kJmol−1, confirming thatNO3- removal by Mg–Al oxide proceeded under chemical reaction control. Furthermore, the adsorption ofNO3- on Mg–Al oxide could be expressed by a Langmuir-type adsorption isotherm. The maximum adsorption amount and equilibrium adsorption constant were 3.8mmolg−1 and 1.33, respectively. The Gibbs free energy change was −18kJmol−1, confirming that the uptake ofNO3- from HNO3 by Mg–Al oxide proceeded spontaneously.
Keywords: Nitric acid; Mg–Al oxide; NO; 3; -; -intercalated Mg–Al layered double hydroxide; Treatment; Kinetics; Equilibrium
Investigation into adsorption mechanisms of sulfonamides onto porous adsorbents
by Weiben Yang; Fangfang Zheng; Xiaoxu Xue; Yiping Lu (pp. 503-509).
Adsorption of sulfonamides to porous adsorbents is influenced by adsorption mechanism. Four types of non-covalent interactions provide different contributions to the resins at different pH. The hypercrosslinked structure, high surface area, and suitable pore size distribution make MN-200 superior antibiotic adsorbents with high adsorption capacity.Display Omitted► Sulfonamide adsorption relates to the properties of adsorbents and adsorbates. ► Four interactions provide different contributions to the adsorbents at different pH. ► The adsorbents exhibited different ionic strengths and temperature dependence. ► The hypercrosslinked adsorbent presents much higher adsorption capacity.The presence of sulfonamide antibiotics in aquatic environments poses potential ecological risks and dangers to human health. In this study, porous resins as adsorbents for the removal of two sulfonamides, sulfadiazine and sulfadimidine, from aqueous solutions were evaluated. Activated carbon F-400 was included as a comparative adsorbent. Despite the different surface properties and pore structures of the three resins, similar patterns of pH-dependent adsorption were observed, implying the importance of sulfonamide molecular forms to the adsorption process on the resins. Sulfonamide adsorption to the three resins exhibited different ionic strengths and temperature dependence consistent with sulfonamide speciation and the corresponding adsorption mechanism. Adsorption of sulfadiazine to F-400 was relatively insensitive to pH and ionic strength as micropore-filling mainly contributed to adsorption. The adsorption mechanism of sulfadiazine to the hypercrosslinked resin MN-200 was similar to that of the macroporous resin XAD-4 at lower pH values, whereas it was almost identical to the aminated resin MN-150 at higher pH. This work provided an understanding of adsorption behavior and mechanism of sulfonamide antibiotics on different adsorbents and should result in more effective applications of porous resin for antibiotics removal from industrial wastewater.
Keywords: Antibiotics; Sulfonamide; Hypercrosslinked; Surface; Temperature
A molecular dynamics study of the interaction of oleate and dodecylammonium chloride surfactants with complex aluminosilicate minerals
by Beena Rai; P. Sathish; Jyotsna Tanwar; Pradip; K.S. Moon; D.W. Fuerstenau (pp. 510-516).
The interaction energies of oleate molecule on spodumene (110) and (001) planes, as obtained through our molecular modelling computations, compare well with the experimental findings wherein the contact angles on the nominal (001) plane are found to be much smaller than those on the cleavage (110) plane.Display Omitted► Complex aluminosilicates: spodumene, jadeite, feldspar, and muscovite are modeled. ► Adsorption mechanisms of oleate and dodecylammonium chloride molecules are studied. ► Molecular modeling describes the crystal structure specificity of oleate molecules. ► A remarkable match between molecular modeling results and experiments is observed. ► Design of selective reagents for separation among complex aluminosilicates.Surface characteristics of complex aluminosilicate minerals like spodumene [LiAl(SiO3)2], jadeite [NaAl(SiO3)2], feldspar [KAlSi3O8], and muscovite [K2Al4(Al2Si6O20)(OH)4]) are modeled. Surface energies are computed for the cleavage planes of these minerals. Adsorption mechanisms of anionic chemisorbing type oleate and cationic physisorbing type dodecylammonium chloride molecules on two different crystal planes, that is (110) and (001), of spodumene and jadeite are studied in terms of the surface–surfactant interaction energies computed using molecular dynamics (MD) simulations. The conclusions drawn from purely theoretical computations match remarkably well with our experimental results.
Keywords: Molecular dynamics; Spodumene; Jadeite; Feldspar; Muscovite; Oleate; Dodecylammonium chloride; Aluminosilicates
Diagnosis of dengue infection using a modified gold electrode with hybrid organic–inorganic nanocomposite and Bauhinia monandra lectin
by Cesar A.S. Andrade; Maria D.L. Oliveira; Celso P. de Melo; Luana C.B.B. Coelho; Maria T.S. Correia; Maurício L. Nogueira; Pankaj R. Singh; Xiangqun Zeng (pp. 517-523).
The BmoLL recognition for dengue serotypes may be attributed to different patterns of glycoproteins in the sera..Display Omitted► A sensitive and selective biosensor for dengue serotype was successfully developed. ► BmoLL recognition may be attributed to different patterns of glycoproteins in the sera. ► AuNpPANI-BmoLL was used to fabricate a dengue nanobiosensor with low detection limit.A sensitive and selective biosensor for dengue serotyping was successfully developed. The biosensor uses a novel gold nanoparticles-polyaniline hybrid composite (AuNpPANI) for the immobilization of Bauhinia monandra lectin (BmoLL). The nanocomposite was applied to a bare gold electrode surface by chemical adsorption, and BmoLL was subsequently electrostatically adsorbed to the nanocomposite-modified surface. Atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance (EI) techniques were applied to evaluate the immobilization of BmoLL on AuNpPANI. The AFM images for AuNpPANI-BmoLL-DEN systems indicate a homogenous, compact and dense film of the conjugate. In the EI analyses, an obvious difference of the electron transfer resistance between the AuNpPANI-modified electrode and the bare gold electrode was observed. Among three dengue serotypes studied, dengue serotype 2 (DEN2) has higher values for RCT, and lower values for both n and Q. These are indications of a larger blocking effect and smaller capacitive dispersion, resulting from the higher agglutination of glycoproteins from the DEN2 sera. The selective BmoLL recognition for various dengue serotypes may be attributed to different patterns of glycoproteins in the sera produced by the glycoprotein immunoresponse from patients infected by the dengue virus.
Keywords: Impedance spectroscopy; Cyclic voltammetry; Dengue; Lectin; Bauhinia monandra
Diffusion-controlled evaporation of sodium dodecyl sulfate solution drops placed on a hydrophobic substrate
by Merve Dandan Doganci; Belma Uyar Sesli; H. Yildirim Erbil (pp. 524-531).
When SDS anionic surfactant is added to a water drop, it changes the mode of drop evaporation without affecting the diffusion-controlled evaporation rate.Display Omitted► The effect of SDS on the diffusion-controlled evaporation rate was investigated. ► SDS did not alter water evaporation rate, only evaporation mode was changed. ► The constant contact angle mode was operative up to 80 mM SDS concentration. ► Lucassen-Reynders approach was applied to determine SDS adsorption on solid surface. ► An equation was developed to compare evaporation rates of drops with differentθ i.In this work, the effect of SDS anionic surfactant on the diffusion-controlled evaporation rate of aqueous solution drops placed on TEFLON–FEP substrate was investigated with 11 different SDS concentrations. Drop evaporation was monitored in a closed chamber having a constant RH of 54–57% by a video camera. The initial contact angle,θ i decreased from 104±2° down to 68±1° due to the adsorption of SDS both at the water–air and the solid–water interfaces. The adsorption of SDS on the solid surface was found to be 76% of that of its adsorption at the water–air interface by applying Lucassen-Reynders approach. An equation was developed for the comparison of the evaporation rates of drops having differentθ i on the same substrate. It was found that the addition of SDS did not alter the drop evaporation rate considerably for the first 1200s for all the SDS concentrations. The main difference was found to be the change of the mode of drop evaporation by varying the SDS concentration. The constant θ mode was operative up to 80mM SDS concentration, whereas constant contact area mode was operative after 200mM SDS concentrations due to rapid drop pining on the substrate.
Keywords: Drop evaporation; SDS; Sodium dodecyl sulfate; Contact angle; Surfactant adsorption layers
Modification of polystyrene surface in aqueous solutions
by J.A. Mielczarski; Y.L. Jeyachandran; E. Mielczarski; B. Rai (pp. 532-539).
Proposed chemical modification scheme of polystyrene when treated with phosphate buffered saline solution under ambient conditions. The multi-step mechanism for the wet modification includes: photo-oxidation/reduction, swelling and conformational changes and rearrangement of polystyrene chain.Display Omitted► Fast surface modification of polystyrene (PS) is possible under ambient conditions with phosphate buffered saline. ► The modification results from photo-oxidation/reduction, swelling, conformational changes and re-arrangement of PS chain. ► The modification can be controlled by pre-adsorption of bovine serum albumin or thermal annealing of PS. ► The process is facilitated by phosphate ions and suitable ionic strength.Herein, we report our analysis of the surface modification of polystyrene (PS) when treated under ambient conditions with a common biological buffer such as phosphate buffered saline (PBS) or aqueous solutions of the ionic constituents of PBS. Attenuated total reflection Fourier transform infrared spectroscopy was used for the analysis because the resultant spectra are very sensitive to minor changes in the chemical and structural properties of PS films. In addition, ultraviolet–visible spectroscopy was applied to characterize the surface modifications of PS. Treatment with PBS resulted in the most significant chemical and structural surface modifications of the PS films, as compared with each of the solutions of the constituents of PBS, which were tested separately. A multistep mechanism for the wet modification of PS is discussed. We postulate that the observed surface modifications are the result of photo-oxidation/reduction, swelling, and conformational changes and re-arrangement of the polymer chain. The resultant surface modifications could be similar to those produced by commonly used dry processes such as plasma treatments and electron, ion or ultraviolet irradiation. We found that the modifications that occurred in PBS were more stable than those initiated by dry processes. The formation of active groups on the surface of PS can be controlled by adsorption of bovine serum albumin or thermal annealing of PS before PBS treatment. This approach provides a simple and efficient method for the surface modification of PS for biomedical applications.
Keywords: Polystyrene; Surface modifications; Adsorption of bio-reagents; ATR infrared spectroscopy; Surface active groups; Photo-oxidation/reduction
Study of the coalescence/splash threshold of droplet impact on liquid films and its relevance in assessing airborne particle release
by C. Motzkus; F. Gensdarmes; E. Géhin (pp. 540-552).
The purpose of this work was to study experimentally the particle emission in atmosphere during the impact of droplets on a liquid film according to the coalescence/splash threshold. Result provides reliable experimental data for further validation of computer simulation and allows assessing workers’ exposure in industrial facility in case of dripping pollutant liquid.Display Omitted► We model airborne particle release during the impact of droplets on a liquid film. ► New correlation distinguishes prompt splash threshold from classical splash. ► Threshold relation is relevant to qualitatively assess particulate airborne release. ► Increasing Weber number involves an increase in airborne release fraction. ► Decreasing Ohnesorge number increases the airborne release fraction.Impingement of droplets on surfaces occurs in many industrial and natural processes. The study of droplet break-up is fundamental in order to determine the potential sources of airborne contamination for scenarios of hazardous liquid falls such as dripping. There are very few data in the literature describing the case of impact of millimetre-size droplets. The purposes of this work were to study experimentally particle emission during the impact of droplets on a liquid film and to assess the use of coalescence/splash relations to predict airborne particle release. The results are described using dimensionless numbers taking into account the inertial, viscosity and surface tension forces. Experiments were carried out for Weber numbers between 62 and 1754 and for Ohnesorge numbers between 2.0×10−3 and 1.5×10−2. New results on coalescence/splash thresholds are obtained using highly sensitive aerosol measurement and allow a prediction concerning the presence or absence of airborne particles according to a threshold relation. Moreover, we propose a modification of the Cossali et al.’s relation in order to describe the coalescence/prompt splash threshold.
Keywords: Droplet; Aerosol; Resuspension; Airborne release fraction; Prompt splash
Spontaneous periodic pulsation of contact line in oil/water system – Frequency control with divalent cations and applied voltage
by Katsuhito Oomiya; Daishi Mori; Takahiko Ban; Akihisa Shioi (pp. 553-559).
Ion-sensitive pulsation of contact line in oil/water system..Display Omitted► We found a quasi-periodic pulsation of contact line for an oil/water system. ► The frequency increased with the increase in applied voltage across the interface. ► The frequency depended on cation species, and its order was Ba2+>Sr2+>Mg2+≫Ca2+. ► This order agreed with the order of ion concentrations in the oil phase.Periodic oscillatory change of hydrophilicity (or hydrophobicity) of a glass surface was studied. A glass capillary was immersed normally at an oil/water interface. The water phase contained the cationic surfactant trimethyloctadecylammoniumchloride, and the oil phase contained bis(2ethylhexyl) phosphate. Adsorption of the surfactant molecules and their desorption via anionic chemicals dissolved in the oil generated a gradual wetting by the water, followed by a rapid wetting by oil. The three phase contact line exhibited a pulse-like motion that continued, at least for a few minutes. The frequency depended on the cation species dissolved in water and the applied voltage across the oil/water interface. Four kinds of cations, Mg2+, Ca2+, Sr2+ and Ba2+ were used. While the frequency order was Ba2+>Sr2+>Mg2+, the Ca2+-containing interface did not show any motion irrespective of the applied voltage. There was a threshold voltage and concentration of anionic chemical that was necessary for the onset of this motion. The pulsation mechanism and its ion selectivity are also discussed. This interfacial motion was a typical nonlinear oscillation with an ion-selective nature. In this regard, this interfacial motion had biomimetic characteristics.
Keywords: Contact line motion; Nonlinear oscillation; Oil/water system; Wetting and dewetting
One-step electrophoretic deposition for the preparation of superhydrophobic silica particle/trimethylsiloxysilicate composite coatings
by Hitoshi Ogihara; Takafumi Katayama; Tetsuo Saji (pp. 560-566).
Superhydrophobic silica/silicon resin composite coatings were prepared by one-step electrophoretic deposition. By controlling coating thickness, transparent superhydrophobic coatings were formed.Display Omitted► Superhydrophobic SiO2 particle/silicon resin composite coatings were prepared by one-step electrophoretic deposition. ► A hydrophobic silicon resin added in electrophoretic deposition baths had a great influence on wettability. ► Both SiO2 particles and a hydrophobic silicon resin were electrophoretically deposited. ► Transparent superhydrophobic SiO2/silicon resin composite coatings were prepared by adjusting the amount of the deposits.SiO2 particle/silicone resin (trimethylsiloxysilicate (TMSS)) composite coatings were prepared by electrophoretic deposition (EPD), and their wettability was examined. SiO2 coatings prepared by EPD baths without TMSS were hydrophilic, while superhydrophobicity was observed for SiO2/TMSS composite coatings. IR spectra and EDS analyses revealed that not only SiO2 particles but also TMSS electrophoretically moved toward a cathode; as a result, hydrophilic SiO2 particles turned into superhydrophobic composite coatings by one-step EPD. SEM and AFM images of the superhydrophobic SiO2/TMSS composite coatings showed the presence of both nanometer- and micrometer-sized roughness in their surfaces. Particle size of SiO2 had a great influence on the wettability of the composite coatings. The superhydrophobic SiO2/TMSS composite coatings showed excellent water repellency; they repelled running water continuously. In addition, by controlling the amount of deposited SiO2 particles and TMSS, transparent superhydrophobic SiO2/TMSS composite coatings were prepared.
Keywords: Superhydrophobic; Transparent; Coating; Electrophoretic deposition; Silica; Nanoparticle
High-speed droplet actuation on single-plate electrode arrays
by Arghya Narayan Banerjee; Shizhi Qian; Sang Woo Joo (pp. 567-574).
High-speed actuation of liquid droplet in air is achieved at a relatively lower DC voltage on an all-in-a-single-plate co-planar electrode arrays.Display Omitted► High droplet speed in air. ► All-in-a-single-plate co-planar electrodes. ► High permittivity material. ► Higher speed in co-planer system with respect to parallel-plate system.This paper reports a droplet-based microfluidic device composed of patterned co-planar electrodes in an all-in-a-single-plate arrangement and coated with dielectric layers for electrowetting-on-dielectric (EWOD) actuation of discrete droplets. The co-planar arrangement is preferred over conventional two-plate electrowetting devices because it provides simpler manufacturing process, reduced viscous drag, and easier liquid-handling procedures. These advantages lead to more versatile and efficient microfluidic devices capable of generating higher droplet speed and can incorporate various other droplet manipulation functions into the system for biological, sensing, and other microfluidic applications. We have designed, fabricated, and tested the devices using an insulating layer with materials having relatively high dielectric constant (SiO2) and compared the results with polymer coatings (Cytop) with low dielectric constant. Results show that the device with high dielectric layer generates more reproducible droplet transfer over a longer distance with a 25% reduction in the actuation voltage with respect to the polymer coatings, leading to more energy efficient microfluidic applications. We can generate droplet speeds as high as 26cm/s using materials with high dielectric constant such as SiO2.
Keywords: Co-planar electrode; Electrowetting-on-dielectric; Droplet; Microfluidics
Bioreducible insulin-loaded nanoparticles and their interaction with model lipid membranes
by Rickard Frost; Gregory Coué; Johan F.J. Engbersen; Michael Zäch; Bengt Kasemo; Sofia Svedhem (pp. 575-583).
Synthesis and characterization of poly(amido amine) based polyelectrolyte complexes, proving their responsiveness towards glutathione and a decrease in pH while adsorbed to a model lipid membrane.Display Omitted► Novel nanodrugs based on protein-loaded polyelectrolyte complexes were produced. ► Nanodrug–model membrane interactions were studied with surface sensitive techniques. ► The nanodrugs collapsed into thin layers on top of oppositely charged lipid membranes. ► The bioreducible nanodrugs disintegrated when exposed to glutathione. ► The nanodrugs disintegrated when the ambient pH was reduced from 7.3 to 5.1.To improve design processes in the field of nanomedicine, in vitro characterization of nanoparticles with systematically varied properties is of great importance. In this study, surface sensitive analytical techniques were used to evaluate the responsiveness of nano-sized drug-loaded polyelectrolyte complexes when adsorbed to model lipid membranes. Two bioreducible poly(amidoamine)s (PAAs) containing multiple disulfide linkages in the polymer backbone (SS-PAAs) were synthesized and used to form three types of nanocomplexes by self-assembly with human insulin, used as a negatively charged model protein at neutral pH. The resulting nanoparticles collapsed on top of negatively charged model membranes upon adsorption, without disrupting the membrane integrity. These structural rearrangements may occur at a cell surface which would prevent uptake of intact nanoparticles. By the addition of glutathione, the disulfide linkages in the polymer backbone of the SS-PAAs were reduced, resulting in fragmentation of the polymer and dissociation of the adsorbed nanoparticles from the membrane. A decrease in ambient pH also resulted in destabilization of the nanoparticles and desorption from the membrane. These mimics of intracellular environments suggest dissociation of the drug formulation, a process that releases the protein drug load, when the nanocomplexes reaches the interior of a cell.
Keywords: Poly(amidoamine)s; Nanoparticle; Protein delivery; QCM-D; Supported lipid bilayer
A pH dependent thermo-sensitive copolymer drug carrier incorporating 4-amino-2,2,6,6-tetramethylpiperidin-1-oxyl (4-NH2-TEMPO) residues for electron spin resonance (ESR) labeling
by Ronghua Yu; Hongli Zhao; Zijun Zhao; Yuanyuan Wan; Huihui Yuan; Minbo Lan; Leonard F. Lindoy; Gang Wei (pp. 584-593).
The LCST was pH dependent and varied in a narrow practical range, 35.4°C at pH 5.0, 37.5°C at pH 6.5 and 39.4°C at pH 7.4, which was below, near and above nominal physiological temperature respectively.Display Omitted► A pH dependent thermo-sensitive copolymer with narrow window of LCST was synthesized. ► The CMC of micelles was corresponded to 4.0523mg/L. ► The situation of TEMPO carrying micelles can be detected by ESR. ► The micelles showed non-toxicity towards cells, pointed to their biocompatibility.The fabrication of a new amphiphilic block copolymer composed of a polydl-lactic acid (PLA) hydrophobic backbone and pH dependent thermo-sensitive poly ( N-isopropyl) methacrylamide-co- N-isopropylmaleamic acid-co-10-undecenoic acid (PNIPAAm-co-NIPMMA-co-UA) entities as hydrophilic domains as well as carrying 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) residues for electron spin resonance (ESR) labeling is reported. The lower critical solution temperature (LCST) of the copolymer was determined by optical absorbance measurements. The LCST was pH dependent and varied in a narrow practical range, 35.4°C at pH 5.0, 37.5°C at pH 6.5 and 39.4°C at pH 7.4, which was below, near and above nominal physiological temperature respectively. The assembly of the copolymer into micelles in aqueous solution at temperatures below the LCST was confirmed by FT-IR,1H NMR and fluorescence spectroscopy. It is demonstrated that the anticancer drug, 5-fluorouracil (5-FU) can be loaded effectively within the polymeric micelles and released in response to environmental stimuli- namely, pH and temperature.
Keywords: pH; Thermo-sensitive copolymer; TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl); Micelles; Electron spin resonance (ESR)
Biomimetic gelatin–octacalcium phosphate core–shell microspheres
by Elisa Boanini; Adriana Bigi (pp. 594-599).
Both calcium and alendronate functionalization improves octacalcium phosphate deposition on the surface of gelatin microspheres.Display Omitted► Gelatin microspheres coated with octacalcium phosphate. ► Functionalization of microspheres with calcium ions. ► Functionalization of microspheres with a bisphosphonate (alendronate). ► Calcium phosphate porous shell modulates gelatin and alendronate release. ► Biomimetic mineralization based on molecular recognition.Calcium phosphate/polymeric microparticles synthesized through a biomimetic approach are regarded with increasing interest for their various potential applications, including tissue engineering and regenerative medicine. Herein we report the synthesis and characterization of gelatin/octacalcium phosphate core/shell microspheres. Deposition of the calcium phosphate shell on the polymeric microspheres was obtained through bio-inspired mineralization on the surface of functionalized gelatin microparticles. Gelatin microspheres stabilized by alginate dialdehyde were prepared using an inverse microemulsion. Functionalization was achieved by enriching the microspheres composition with calcium ions or, alternatively, with alendronate, a bisphosphonate widely employed for the treatment of bone diseases. Functionalization and synthesis of the inorganic phase in the microemulsion environment were key factors for the achievement of a complete coating of the microspheres with calcium phosphate. The inorganic shell is constituted of small crystals of octacalcium phosphate, which control gelatin and alendronate release.
Keywords: Microspheres; Calcium phosphate; Gelatin; Biomimetic material; Bisphosphonate
Interfacial properties of hydrophilized poly(lactic-co-glycolic acid) layers with various thicknesses
by G. Gyulai; Cs.B. Pénzes; M. Mohai; T. Lohner; P. Petrik; S. Kurunczi; É. Kiss (pp. 600-606).
Distribution of surface modifying Pluronic in the PLGA film varies with layer thickness. According to that BSA adsorption is highly dependent on the thickness of the polymer blend layer.Display Omitted► Improved surface biocompatibility of PLGA film by blending with Pluronic127. ► Reduced protein adsorption in accordance with surface hydrophilicity and composition. ► Layer thickness greatly affected surface properties and protein repellency of the film. ► Blend layers go through swelling and partial dissolution of Pluronic.Biodegradable polyesters such as poly(lactic-co-glycolic acid) copolymers (PLGA) are preferred materials for drug carrier systems although their surface hydrophobicity greatly limits their use in controlled drug delivery. PLGA thin films on a solid support blended with PEG-containing compound (Pluronic) were used as model systems to study the interfacial interactions with aqueous media. Degree of surface hydrophilization was assessed by wettability, and X-ray photoelectron spectroscopy (XPS) measurements. Protein adsorption behavior was investigated by in situ spectroscopic ellipsometry. The degree of protein adsorption showed a good correlation with the hydrophilicity, and surface composition. Unexpectedly, the layer thickness was found to have a great impact on the interfacial characteristics of the polymer films in the investigated regime (20–200nm). Thick layers presented higher hydrophilicity and great resistance to protein adsorption. That special behavior was explained as the result of the swelling of the polymer film combined with the partial dissolution of Pluronic from the layer. This finding might promote the rational design of surface modified biocompatible nanoparticles.
Keywords: Protein adsorption; Ellipsometry; Surface modification; PLGA-Pluronic blends; Biocompatibility; Wettability; XPS
Hydrophilicity/porous structure-tuned, SiO2/polyetherimide-coated polyimide nonwoven porous substrates for reinforced composite proton exchange membranes
by Jung-Ran Lee; Ji-Hye Won; Na-Young Kim; Moo-Seok Lee; Sang-Young Lee (pp. 607-614).
SiO2 nanoparticles/polyetherimide binders-coated polyimide nonwoven porous substrates for reinforced composite proton exchange membranes were developed. Properties of the porous substrates were improved by controlling hygroscopic SiO2 particle size..Display Omitted► Porous substrate-reinforced Nafion composite membrane. ► Silica (SiO2)/polyetherimide (PEI)-coated PI nonwoven porous substrates. ► Importance of SiO2 size in tuning porous structure and properties of the substrates. ► Porous substrate crucially affects performance of reinforced composite membranes.Porous substrate-reinforced composite proton exchange membranes have drawn considerable attention due to their promising application to polymer electrolyte membrane fuel cells (PEMFCs). In the present study, we develop silica (SiO2) nanoparticles/polyetherimide (PEI) binders-coated polyimide (PI) nonwoven porous substrates (referred to as “S-PI substrates”) for reinforced composite membranes. The properties of S-PI substrates, which crucially affect the performance of resulting reinforced composite membranes, are significantly improved by controlling the hygroscopic SiO2 particle size. The 40nm S-PI substrate (herein, 40nm SiO2 particles are employed) shows the stronger hydrophilicity and highly porous structure than the 530nm S-PI substrate due to the larger specific surface area of 40nm SiO2 particles. Based on the comprehensive understanding of the S-PI substrates, the structures and performances of the S-PI substrates-reinforced composite membranes are elucidated. In comparison with the 530nm S-PI substrate, the hydrophilicity/porous structure-tuned 40nm S-PI substrate enables the impregnation of a large amount of a perfluorosulfonic acid ionomer (Nafion), which thus contributes to the improved proton conductivity of the reinforced Nafion composite membrane. Meanwhile, the reinforced Nafion composite membranes effectively mitigate the steep decline of proton conductivity with time at low humidity conditions, as compared to the pristine Nafion membrane. This intriguing finding is further discussed by considering the unusual features of the S-PI substrates and the state of water in the reinforced Nafion composite membranes.
Keywords: Polymer electrolyte membrane fuel cells; Reinforced composite membranes; Porous substrates; Silica; Polyimide nonwovens; Nafion
Optimization of Co2+ ions removal from water solutions via polymer enhanced ultrafiltration with application of PVA and sulfonated PVA as complexing agents
by Niğmet Uzal; Agnieszka Jaworska; Agnieszka Miśkiewicz; Grażyna Zakrzewska-Trznadel; Corneliu Cojocaru (pp. 615-624).
The removal of cobalt (II) ions from aqueous solutions by PEUF process was investigated using two different water-soluble polymers: non-modified PVA and PVA modified by sulfonation. The results showed that sulfonation of polymer has improved significantly the binding ability of PVA.Display Omitted► In this study, we examined UF-complexation process for the removal of Co2+ ions from water solutions. ► Two different water-soluble polymers were used, non-modified PVA and modified PVA by sulfonation. ► The method of experimental design and response surface methodology have been employed. ► Co2+ removal ability of sulfonated PVA was much higher than its non-sulfonated precursor.The paper presents the results of the studies of UF-complexation process applied for the removal of Co2+ ions from water solutions. As binding agents for cobalt ions, the PVA polymer (M w=10,000) and its sulfonated form, synthesized in the laboratory, have been used. The method of experimental design and response surface methodology have been employed to find out the optimal conditions for the complexation process and to evaluate the interaction between the input variables, i.e., initial cobalt concentration, pH and amount of the polymer used, expressed as a polymer/Co2+ ratio r.The data collected by the designed experiments showed that sulfonation of polymer has improved significantly the binding ability of PVA. The optimal conditions of cobalt ions complexation established by response surface model for non-sulfonated PVA polymer have been found to be as follows: the initial concentration of Co2+=5.70mgL−1, the ratio between polymer and metal ions, r=8.58 and pH=5.93. The removal efficiency of Co2+ in these conditions was 31.81%.For sulfonated PVA polymer, the optimal conditions determined are as follows: initial concentration of [Co2+]0=10mgL−1, r=1.2 and pH=6.5. For these conditions, a removal efficiency of 99.98% has been determined. The experiments showed that Co2+ removal ability of sulfonated PVA was much higher than its non-sulfonated precursor. Although the polymer concentrations used in the tests with sulfonated PVA were approximately ten times lower than the non-sulfonated one, the removal efficiency of cobalt ions was significantly higher.
Keywords: Water-soluble polymers; Cobalt; Optimization; Ultrafiltration
Optimizing the matching between the acid and the base of cooperative catalysis to inhibit dehydration in the aldol condensation
by Bo Liu; Shujie Wu; Xiaofang Yu; Jingqi Guan; Qiubin Kan (pp. 625-628).
The adjustment of the matching between the acid and the base both facilitates the cooperative activation and inhibits the subsequent dehydration, all without affecting the yield.Display Omitted► Acid-base bifunctionalized Al-SBA-15. ► High yields and excellent selectivity for the aldol condensation. ► Dehydration of aldol product.A series of acid–base bifunctional catalysts were prepared, and high yields and excellent selectivity in the aldol condensation were achieved through adjustment of the matching between the acid and the base. The results indicated that proper matching between the acid and the base can both efficiently activate the substrate through cooperative activation and inhibit dehydration without diminishing the yield.
Keywords: Cooperative catalysis; Aldol condensation; Inhibition of dehydration; Acid–base bifunctional catalysts
Study on the wettability of polyethylene film fabricated at lower temperature
by Weixin Hou; Lizhi Zhang; Yi Long (pp. 629-632).
Reversible wettability transition of the PE films prepared at different temperatures.Display Omitted► The wettability and microstructure of PE films prepared at lower temperature have been studied. ► The wettability of the as-prepared PE films can be altered by varying the environmental temperatures. ► A rough surface is not beneficial to the increase of water contact angle particularly at lower temperatures.Polyethylene films were prepared with phase separation at lower temperatures. The wettability of such films varied from hydrophobicity to superhydrophobicity as the processing temperature decreased owing to the increase of surface roughness. Storing the as-prepared films at subzero temperature (−15°C), it was found that the water contact angle of the film decreased obviously, and the decrease depended on the corresponding roughness. Further keeping the as-prepared films at room temperature for 30min, the water contact angle would return to the normal value, which indicated that the reversible switching of surface wettability can be controlled by the environmental temperature.
Keywords: Polyethylene; Phase separation; Superhydrophobicity; Lower temperature
Bimodal colloidal mixtures: From fast to slow aggregation regions
by Junjun Jia; Zehong Jia; Shuichi Iwata (pp. 633-637).
The characteristics of the initial stability in bimodal colloidal mixtures with different sizes but similar surface chemistries are given in the graphical abstract. In the fast aggregation region, the homo- aggregation dominates the initial stability, while the hybrid aggregation (homo- and hetero-aggregation) becomes the main characteristics in the slow aggregation region.Display Omitted►We model the aggregation kinetics of bimodal colloidal mixtures with different sizes but similar surface chemistries. ► Under fast aggregation conditions, the homoaggregation of least stable component dominates the initial stability. ► With the electrolyte ionic strength decreasing (toward the slow aggregation), the hybrid aggregation including the homo- and hetero-aggregation gradually dominates the initial stability.A Brownian dynamics simulation has been used to investigate the aggregation kinetics of bimodal colloidal mixtures with similar surface chemistries but different sizes, driven by the DLVO interaction potential. The time evolution of structural formation is examined by the mean number of neighbors under fast and slow aggregation regions. It was found that the electrolyte ionic strength affects the kinetic pattern of colloidal aggregation. Under the high electrolyte ionic strength conditions (fast aggregation), the selective aggregation of the least stable single component can take place in the early stage, while the other component is enriched in this least stable component in the later stage. With the ionic strength decreasing (towards the slow aggregation), the hybrid aggregation (selective aggregation and heteroaggregation) gradually dominates the aggregation kinetics. Also in the early stage, this evolves to the heteroaggregation of different components under lower ionic strength conditions. The volume fraction has no obvious influence on this kinetic pattern in the early stage.
Keywords: Bimodal colloidal mixture; Brownian dynamics; Mean number of neighbors; Selective aggregation; Secondary minimum