Journal of Colloid And Interface Science (v.356, #2)
Interactions of biomacromolecules with reverse hexagonal liquid crystals: Drug delivery and crystallization applications
by Dima Libster; Abraham Aserin; Nissim Garti (pp. 375-386).
Schematic presentation of HII mesophase, showing the packing of water-filled rods, surrounded by lipid layers.Display Omitted► Monoolein-based HII mesophases, which are stable at room temperature. ► Structural characterization of the HII mesophases. ► Incorporation of peptides and proteins into reverse hexagonal mesophases. ► Sustained delivery of biomacromolecules via HII mesophases. ► Crystallization of biomacromolecules within HII mesophases.Recently, self-assembled lyotropic liquid crystals (LLCs) of lipids and water have attracted the attention of both scientific and applied research communities, due to their remarkable structural complexity and practical potential in diverse applications.The phase behavior of mixtures of glycerol monooleate (monoolein, GMO) was particularly well studied due to the potential utilization of these systems in drug delivery systems, food products, and encapsulation and crystallization of proteins. Among the studied lyotropic mesophases, reverse hexagonal LLC (HII) of monoolein/water were not widely subjected to practical applications since these were stable only at elevated temperatures. Lately, we obtained stable HII mesophases at room temperature by incorporating triacylglycerol (TAG) molecules into the GMO/water mixtures and explored the physical properties of these structures.The present feature article summarizes recent systematic efforts in our laboratory to utilize the HII mesophases for solubilization, and potential release and crystallization of biomacromolecules. Such a concept was demonstrated in the case of two therapeutic peptides—cyclosporin A (CSA) and desmopressin, as well as RALA peptide, which is a model skin penetration enhancer, and eventually a larger macromolecule—lysozyme (LSZ). In the course of the study we tried to elucidate relationships between the different levels of organization of LLCs (from the microstructural level, through mesoscale, to macroscopic level) and find feasible correlations between them. Since the structural properties of the mesophase systems are a key factor in drug release applications, we investigated the effects of these guest molecules on their conformations and the way these molecules partition within the domains of the mesophases. The examined HII mesophases exhibited great potential as transdermal delivery vehicles for bioactive peptides, enabling tuning the release properties according to their chemical composition and physical properties. Furthermore, we showed a promising opportunity for crystallization of CSA and LSZ in single crystal form as model biomacromolecules for crystallographic structure determination.The main outcomes of our research demonstrated that control of the physical properties of hexagonal LLC on different length scales is key for rational design of these systems as delivery vehicles and crystallization medium for biomacromolecules.
Keywords: Monoolein; Proteins; Skin penetration; Peptide; Cyclosporin A; Desmopressin; Phosphatidylcholine
Deflection and pull-in instability of nanoscale beams in liquid electrolytes
by James G. Boyd; Jaesang Lee (pp. 387-394).
The separation between the double-wall carbon nanotube cantilever beam tip at potential ψ1 and the substrate at potential − ψ1 as a function of ψ1 with various values of bulk ion concentration..Display Omitted► Carbon nanotube with electric, osmotic, and van der Waals forces. ► Sum of electric and osmotic forces can be either repulsive or attractive. ► Nanotube deflection is not a monotonic function of its arguments. ► Pull-in voltage increases as bulk ion concentration increases.An elastic beam suspended horizontally over a substrate in liquid electrolyte was subjected to electric, osmotic, and van der Waals forces. The problem, which is governed by four non-dimensional parameters, was solved using the finite element method. The sum of the electric and osmotic forces, the electrochemical force, is usually attractive. However, the electrochemical force can be repulsive for a narrow range of the ion concentration, the initial separation and surface potentials. Furthermore, the beam deflection is not a monotonic function of the applied surface potentials, the bulk ion concentration, or the initial separation between the beam and the substrate. As these parameters are increased monotonically, the beam bends up and then down. The pull-in voltage increases as the bulk ion concentration increases. The pull-in voltage of a double-wall carbon nanotube suspended over a graphite substrate in liquid can be less than or greater than the pull-in voltage in air, depending on the bulk ion concentration. The critical separation between the DWCNT and the substrate increases with the bulk ion concentration. However, for a given bulk ion concentration, the critical separation is independent of the electric potentials. Furthermore, the critical separation is approximately equal in liquid and air.
Keywords: Electric force; Osmotic force; van der Waals force; Poisson-Boltzmann; Pull-in instability
Titania–silver and alumina–silver composite nanoparticles: Novel, versatile synthesis, reaction mechanism and potential antimicrobial application
by Tanushree Bala; Gordon Armstrong; Fathima Laffir; Roibeard Thornton (pp. 395-403).
A facile, reproducible synthesis of titania–silver and alumina–silver composite nanoparticles is reported. Both composite nanoparticles formed via different modes of assembly. Epoxy nanocomposites formulated using these nanoparticles exhibited antimicrobial activity against E. coli and S. epidermidis.Display Omitted► Facile, synthesis of titania–silver and alumina–silver composite nanoparticles. ► Oxide surfaces modified using oleic acid as intermediate. ► Titania–silver and alumina–silver nanoparticles form via different modes of assembly. ► Epoxy composites exhibit antimicrobial activity against E. coli and S. epidermidis.Titania–silver (TiO2–Ag) and alumina–silver (Al2O3–Ag) composite nanoparticles were synthesised by a simple, reproducible, wet chemical method under ambient conditions. The surface of the oxides was modified with oleic acid, which acted as an intermediate between the oxide surface and the silver nanoparticles. The resulting composite nanoparticles were thoroughly characterised by XRD, TEM, XPS, FTIR and TGA to elucidate the mode of assembly of Ag nanoparticles on the oxide surfaces. Epoxy nanocomposites were formulated with TiO2–Ag and Al2O3–Ag to examine potential applications for the composite nanoparticles. Preliminary results from disc diffusion assays against Escherichia coli DH5α and Staphylococcus epidermidis NCIMB 12721 suggest that these TiO2–Ag and Al2O3–Ag composite nanoparticles have potential as antimicrobial materials.
Keywords: TiO; 2; –Ag; Al; 2; O; 3; –Ag; Composite; Nanoparticle; Epoxy polymer; Antimicrobial; Staphylococcus epidermidis; Escherichia coli
Colloidal and chemical aspects of nanosized hydrated zirconium dioxide synthesized via a sol–gel process
by Iryna Chepurna; Roman Smotraev; Valentyn Kanibolotsky; Volodymyr Strelko (pp. 404-411).
This study demonstrates turbidimetric investigations of hydrated zirconia sols firstly obtained by (a) two-step neutralization of zirconium oxychloride and (b) its homogeneous hydrolysis at neutral pH.Display Omitted► The sol–gel transition point during hydrated zirconium dioxide synthesis was determined. ► The effect of preparation conditions on average particles size and pH of ZrO2⋅ nH2O sols was established. ► Coagulation constant, activation energy, and thermal effect of ZrO2⋅ nH2O gelation were calculated.The processes of coagulation and gelation of sols in zirconium oxychloride aqueous solutions and the properties of hydrated zirconium dioxide sols (pH, particles size, dynamic viscosity) depending on the aging conditions of partially neutralized zirconium oxychloride feedstock solution–zirconyl hydroxychloride used for the synthesis and molar ratio of initial reagents (Zr/NaOH, Zr/CH3COO−) were first studied in the paper. The concentration and temperature limits of hydrated zirconium dioxide sols stability were determined. The coagulation constant, gelation activation energy, and gelation thermal effect values were found.
Keywords: Hydrated zirconium oxide; Sol–gel process; Particle size; Turbidimetric analysis; Gelation; Activation energy; Coagulation constant
Self-assembly of disk-like multiring ZnO–SnO2 colloidal nanoparticles
by Hongjun Ji; Xiaoheng Liu; Xin Wang; Shiming Liang; Xiutao Ge; Yonghong Li (pp. 412-415).
The image shows self-assembled disk-like multiring ZnO–SnO2 (Zn/Sn=1/1) colloidal nanoparticles.Display Omitted► Disk-like multiring ZnO-SnO2 colloidal nanoparticles have been self-assembled. ► The tenacity of ZnO-SnO2 ring-like lamellae determines multiring structures. ► Self-assembly is due to electrostatic interactions between (Zn-O-Sn-O)n2n+ and DBSA.ZnO–SnO2 colloidal nanoparticles have been successfully synthesized by using the composite of ZnCl2 and Sn(OC4H9)4 as inorganic precursor and dodecylbenzenesulfonic acid (DBSA) as an organic template. The assembled nanostructures of ZnO–SnO2 products have been carefully investigated by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is found that ZnO–SnO2 colloidal nanoparticles take a disk-like multiring nanostructure. This interesting structure is predominantly determined by the tenacity for ZnO–SnO2 mixtures to stabilize lamellae. A mechanism based on electrostatic interactions between the precursor and template has been proposed to illustrate the resulting nanoparticle structure.
Keywords: Multiring nanodisks; Tenacity; Self-assembly; ZnO; SnO; 2
Synthesis and surface photochemistry of graphitized carbon quantum dots
by Yun Liu; Chun-yan Liu; Zhi-ying Zhang (pp. 416-421).
Graphitized CQD synthesized from carbohydrates through hydrothermal process consisted of the stack of graphene sheets and their excitation-dependent PL should be attributed to the n→ π* transition of surface CO bonds.Display Omitted► Graphitized CQDs were prepared from organic molecule through hydrothermal method. ► Esterification with glycol made the PL of CQDs reached to the QY of ∼10%. ► The excitation-dependent PL may be due to the n→ π* transition of surface CO bond. ► Esterification of surface CO bond played a dominant role in the PL jump of CQDs.Graphitized carbon quantum dots (CQDs) were synthesized by a simple hydrothermal process with cetyltrimethylammonium bromide (CTAB) as the starting material and nitric acid as surface oxidant. The photoluminescent quantum yield (QY) of CQDs could be greatly enhanced through surface esterification with glycol. Based on the structure characterization, we proposed that the CQDs consisted of the stack of graphene sheets sized several nanometers and their excitation-dependent photoluminescence (PL) should be attributed to the n→ π* transition of CO bond of surface carboxylic groups. And the PL of CQDs was obviously enhanced by the esterification of carboxylic groups, possibly due to the increase of the molecular coplanarity or the rigidity.
Keywords: Carbon; Quantum dot; Photoluminescence; Hydrothermal; Surface passivation
Oil droplet size determination in complex flavor delivery systems by diffusion NMR spectroscopy
by Wolfgang Fieber; Valeria Hafner; Valéry Normand (pp. 422-428).
With PFG diffusion NMR spectroscopy flavor oil droplet size distribution in yeast encapsulation systems (unimodal, left) and in glassy encapsulation systems (bimodal, right) can be discriminated..Display Omitted► Oil droplet size distribution was determined for solid flavor delivery systems. ► Microscopy (SEM, TEM) methods were combined with PFG diffusion NMR spectroscopy. ► Size distribution is unimodal in yeast and multimodal in glassy systems. ► NMR data were fitted to uni- and bimodal distribution functions..Droplet size distribution of flavor oils in two different solid flavor delivery systems were determined with pulsed field gradient NMR spectroscopy: yeast encapsulation system, a spray dried flavor encapsulation system based on empty yeast cells, and glassy encapsulation system, an extruded solid water soluble carbohydrate delivery system. The oil droplet sizes are limited by the yeast cell walls in the yeast encapsulation system and the size distribution is unimodal according to images from transmission electron microscopy. The droplet size determination with diffusion NMR is based on the Murday and Cotts theory of restricted diffusion of liquids in geometrical confinements. Good fits of the diffusion data could be obtained by applying a unimodal, log-normal size distribution model and average droplet sizes of about 2μm were found that correspond approximately to the inner diameter of the yeast cells. Scanning electron microscopy images showed a multimodal droplet size distribution in the glassy extruded delivery systems. To fit the NMR data a bimodal log-normal distribution function with five independent fitting parameters was implemented that yielded consistent and robust results. The two size populations were found in the micron and sub-micron range, respectively. The method was sufficiently accurate to depict variation of droplet size distributions in glassy encapsulation systems of different formulation.
Keywords: PFG–NMR; Restricted diffusion; Droplet size distribution; Flavor encapsulation; Food delivery systems; Transmission electron microscopy; Scanning electron microscopy
Synthesis of dissymmetrical nanoparticles with a new hybrid silica template
by Zhen Meng; Chunyan Xue; Luyao Lu; Bo Yuan; Xuehai Yu; Kai Xi; Xudong Jia (pp. 429-433).
An effective method has been developed using a new type of template for obtaining large amounts of uniform Janus particles and nano-bowls (several grams) with tunable shapes through seed-emulsion polymerization.Display Omitted► A new type of template to synthesis eccentrical core–shell nanoparticles. ► Synthesis of uniform Janus nanoparticles with tunable shapes in large amounts. ► Different shapes of nanoparticles (from mushroom-like to bowl-like) can be obtained by hydrofluoric acid etch. ►The bowl-like nanoparticles’ inner and outer surfaces have distinct properties.An easy, novel route to prepare Janus nanoparticles and nano-bowls with tunable shapes has been developed. This approach uses a new kind of monodisperse vinyl-silica nanoparticles as templates to obtain large amounts of uniform Janus particles and nano-bowls (several grams). The efficient method adopts water-based hydrolysis-condensation and seed-emulsion polymerization. The uniform Janus nanoparticles and nano-bowls will display wide potential applications in many fields, such as: chemical sensors, construction of complex superstructures and nano-bioreactors.
Keywords: Polysiloxanes; Colloids; Template; Janus nanoparticles; Nano-bowls
Synthesis and application of colloidal nanocrystals of theMFI-type zeolites
by Ryota Watanabe; Toshiyuki Yokoi; Takashi Tatsumi (pp. 434-441).
The colloidal dispersion containing the nanosized zeolites with theMFI topology including silicalite-1 av. 62nm in size and TS-1 av. 100nm in size, has been successfully prepared. Fabrication of the multilayer and monolayer films of silicalite-1 and TS-1 nanocrystals has also been attained by a dip-coating technique using the colloidal dispersion of the nanosized zeolites.Display Omitted► Colloidal nanocrystals of silicalite-1 av. 62 nm in size and TS-1 av. 100 nm in size were successfully prepared. ► Te TS-1 nanocrystals showed a higher catalytic activity in the epoxidation of cyclohexene than micro-sized TS-1. ► Multilayer and monolayer films of the silicalite-1 and TS-1 nanocrystals were also prepared.The colloidal dispersion containing the nanosized zeolites with theMFI topology has been successfully prepared. A pre-aging process of the mother gel at 80°C for 24h before the crystallization was important for the formation of the nanosized zeolites. We have also found that silicalite-1 nanocrystals av. 62nm in size were formed by the addition of acidic amino acids into the mother gel. The particle size of the zeolites can be controlled ranging from 62 to 530nm by changing the amount of water, aging process, crystallization time and temperature and the addition of organic molecules. Furthermore, nanosized titanium silicalite-1 (TS-1) with the size of 50–130nm has been successfully synthesized by the addition of a Ti source into the synthesis gel of the silicalite-1 nanocrystals. The nanosized TS-1 exhibits a higher catalytic activity in the epoxidation of cyclohexene than the microsized ones. Finally, we demonstrate the preparation of thin films of the silicalite-1 and TS-1 nanocrystals onto a silicon substrate by a dip-coating technique.
Keywords: MFI; zeolites; Nanocrystals; Zeolite thin films
Influence of surface conductivity on the apparent zeta potential of TiO2 nanoparticles
by Philippe Leroy; Christophe Tournassat; Mohamed Bizi (pp. 442-453).
TiO2 zeta potential in NaCl solution. Symbols represent values from electrophoresis and lines the ESM surface complexation model predictions at the OHP. ESM is only calibrated by titration data.Display Omitted► Surface conductivity can diminish the electrophoretic mobility. ► Electrophoretic mobility can be corrected of surface conductivity. ► Surface complexation models allow surface conductance estimation. ► Surface conductance can explain the low apparent zeta potential of TiO2.Zeta potential is a physico-chemical parameter of particular importance in describing ion adsorption and electrostatic interactions between charged particles. Nevertheless, this fundamental parameter is ill-constrained, because its experimental interpretation is complex, particularly for very small and charged TiO2 nanoparticles. The excess of electrical charge at the interface is responsible for surface conductance, which can significantly lower the electrophoretic measurements, and hence the apparent zeta potential. Consequently, the intrinsic zeta potential can have a larger amplitude, even in the case of simple 1:1 electrolytes like NaCl and KCl. Surface conductance of TiO2 nanoparticles immersed in a NaCl solution is estimated using a surface complexation model, and this parameter and particle size are incorporated into Henry’s model in order to determine a constrained value of the zeta potential from electrophoresis. Interior conductivity of the agglomerates is calculated using a differential self-consistent model. The amplitude of estimated zeta potential is greater than that derived from the von Smoluchowski equation and corresponds to the electric potential at the outer Helmholtz plane calculated by our surface complexation model. Consequently, the shear plane may be located close to the OHP, contradicting the assumption of the presence of a stagnant diffuse layer at the TiO2/water interface.
Keywords: Zeta potential; Electrophoretic mobility; TiO; 2; Nanoparticle; Surface conductivity; Extended Stern model
Deposition of colloid particles on protein layers: Fibrinogen on mica
by Z. Adamczyk; M. Nattich; M. Wasilewska; M. Sadowska (pp. 454-464).
Enhancement of protein layers on solid substrates can be achieved by controlled deposition of colloid particles. Then, one can determine quantitatively protein coverage using optical microscopy.Display Omitted► Charge distribution over Fb molecules is strongly heterogeneous. ► Charge fluctuations govern colloid deposition on Fb monolayers. ► Fb layers can be detected by colloid enhancement. ► Superadsorbing surfaces are created via Fb preadsorption.Colloid particle deposition was applied to characterize fibrinogen (Fb) monolayers on mica, which were produced by controlled adsorption under diffusion transport. By adjusting the time of adsorption and the bulk Fb concentration, monolayers of desired surface concentration were obtained. The surface concentration of Fb was determined directly by AFM enumeration of single molecules adsorbed over the substrate surface. It was proven that Fb adsorbed irreversibly on mica both at pH 3.5 and at pH 7.4 with the rate governed by bulk transport. The electrokinetic properties of Fb monolayers produced in this way were studied using the streaming potential method. The dependence of the apparent zeta potential of Fb monolayers was determined as a function of the coverage. It was shown that for pH 3.5 the initial negative zeta potential of the mica substrate was converted to positive for Fb coverage exceeding 0.16. On the other hand, for pH 7.4, the zeta potential of a Fb-covered mica remained negative for the entire coverage range. The charge distribution in Fb monolayers was additionally studied using the colloid deposition method, in which negatively and positively charged polystyrene latex particles (ca. 800nm in diameter) were used. An anomalous deposition of negative latex particles on substrates exhibiting a negative zeta potential was observed. Results of these experiments were quantitatively interpreted in terms of the fluctuation theory assuming that adsorption sites consisted of two and three Fb molecules, for pH 3.5 and 7.4, respectively. These results suggested that for pH 7.4, the distribution of charge on Fb molecules was heterogeneous, characterized by the presence of positive patches, whereas the average zeta potential was negative, equal to −19mV. The utility of the colloid deposition method for studying Fb monolayers was further demonstrated in deposition experiments involving positive latex particles. It was shown that for a rather broad range of fibrinogen coverage, both the positive and the negative latex particles can adsorb on surfaces covered by Fb, which behaved, therefore, as superadsorbing surfaces. It was also concluded that the colloid deposition method can be used to determine the Fb bulk concentration for the range inaccessible for other methods.
Keywords: Colloid particle deposition; DLVO theory; Fibrinogen layers on mica; Heterogeneous surface deposition; Streaming potential measurements; Zeta potential of fibrinogen-covered mica
WO3/BiOCl, a novel heterojunction as visible light photocatalyst
by Sajjad Shamaila; Ahmed Khan Leghari Sajjad; Feng Chen; Jinlong Zhang (pp. 465-472).
BiOCl prepared via new low temperature route is developed in a novel hetrerojunction of WO3/BiOCl as an efficient visible light active photocatalyst for environmental cleanup purposes.Display Omitted► 2D nanoflakes of BiOCl are prepared by a new and facile low temperature route. ► A novel heterojunction is developed between BiOCl and WO3. ► The WO3/BiOCl heterojunction extends the absorption edge to the visible region. ► WO3 in this junction acts as the photosensitizer absorbing visible light. ► The WO3/BiOCl composite induces complete decomposition of RhB under visible light.A bismuth oxychloride (BiOCl) nanostructure is prepared by a new low temperature route using sodium dodecyl sulfate as template and urea as hydrolytic agent. A novel heterojunction is developed between BiOCl and tungsten oxide (WO3) to make it an efficient visible light photocatalyst. The catalysts were characterized by X-ray diffraction analysis, Raman spectroscopy, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, and N2 sorption isotherms. The WO3/BiOCl heterojunction system extends the absorption edge to the visible region efficiently. BiOCl works as a main photocatalyst while WO3 acts as the photosensitizer absorbing visible light in the WO3/BiOCl composite. The individual BiOCl and WO3 show very low photocatalytic efficiency under visible light irradiation but their heterojunction provides unexpectedly high efficiency in decomposing rhodamine B as compared to Degussa P25, pure BiOCl, and WO3.
Keywords: BiOCl; WO; 3; /BiOCl; Rhodamine B; Heterojunction; Photocatalysis
Fabrication of cerium oxide nanoparticles: Characterization and optical properties
by Elaheh K. Goharshadi; Sara Samiee; Paul Nancarrow (pp. 473-480).
A facile and environmentally friendly microwave irradiation method has been developed to prepare ceria nanoparticles with the average size 7nm using a set of ionic liquids.Display Omitted► This is the first report on using this type of ionic liquids used in this work in ceria nanoparticle synthesis. ► The method is found to be convenient, rapid, cost-effective, and efficient. No surfactant was used. ► This is the first paper on determining the band gap of ceria nanoparticles using diffuse reflectance spectroscopy.Ceria (CeO2) is a technologically important rare earth material because of its unique properties and various engineering and biological applications. A facile and rapid method has been developed to prepare ceria nanoparticles using microwave with the average size 7nm in the presence of a set of ionic liquids based on the bis (trifluoromethylsulfonyl) imide anion and different cations of 1-alkyl-3-methyl-imidazolium. The structural features and optical properties of the nanoparticles were determined in depth with X-ray powder diffraction, transmission electron microscope, N2 adsorption–desorption technique, dynamic light scattering (DLS) analysis, FTIR spectroscopy, Raman spectroscopy, UV–vis absorption spectroscopy, and Diffuse reflectance spectroscopy. The energy band gap measurements of nanoparticles of ceria have been carried out by UV–visible absorption spectroscopy and diffuse reflectance spectroscopy. The surface charge properties of colloidal ceria dispersions in ethylene glycol have been also studied. To the best of our knowledge, this is the first report on using this type of ionic liquids in ceria nanoparticle synthesis.
Keywords: Ceria nanoparticle; Ionic liquid; Microwave; Optical property
Stable polydiacetylene/ZnO nanocomposites with two-steps reversible and irreversible thermochromism: The influence of strong surface anchoring
by Nisanart Traiphol; Nopparat Rungruangviriya; Ruttayapon Potai; Rakchart Traiphol (pp. 481-489).
This contribution introduces a versatile method to fabricate polydiacetylene/ZnO nanocomposite with core–shell structure. This new class of nanomaterial exhibits two-steps reversible and irrevesible thermochromism.Display Omitted► Polydiacetylene/ZnO nanocomposites with core–shell structure are prepared. ► Strong interfacial interactions reduce segmental dynamics of polydiacetylene. ► The nanocomposites exhibits reversible color transition at ∼100°C. ► The irreversible color transition occurs at ∼145°C. ► Our method offers a new route to control optical property of polydiacetylene.This contribution introduces a versatile method to prepare a new class of polydiacetylene(PDA)-based material. ZnO nanoparticle is used as a nano-substrate for spontaneous assembling of diacetylene monomer, 10,12-pentacosadiynoic acid, on its surface. An irradiation of the organized assemblies by UV light results in PDA/ZnO nanocomposites with deep blue color. Strong ionic interaction and hydrogen bonding at the ZnO surface restrict the dynamics of alkyl side chains and promote the PDA ordering, which in turn drastically affects its thermochromic behaviors. We have found that the PDA/ZnO nanocomposite exhibits two-steps color transition upon increasing temperature. The first transition of the nanocomposite in aqueous suspension, causing the color change from blue to purple, occurs reversibly at ∼90°C. The transition temperature shifts to ∼100°C when the nanocomposite is embedded in polyvinyl alcohol matrix. Further increasing temperature to 145°C induces the second transition, which causes irreversible color change from purple to red.
Keywords: Polydiacetylene; Conjugated polymer; Color transition; Reversible thermochromism; Optical sensor
A simple mixed-solvothermal route for LaPO4 nanorods: Synthesis, characterization, affecting factors and PL properties of LaPO4:Ce3+
by Kai Mi; Yonghong Ni; Yanwei Xu; Xiang Ma; Jianming Hong (pp. 490-495).
The morphology of LaPO4 nanocrystals can be tuned in a water/ethyleneglycol system. The PL property of LaPO4:Ce3+ nanocrystals is investigated.Display Omitted► LaPO4 nanorods have been successfully prepared by a simple mixed-solvothermal route. ► The morphology of the final product can be tuned by the volume ratio of water/EG. ► ExcessH2PO4- ions are found to be unfavorable to the formation of LaPO4 nanorods.In this paper, LaPO4 nanorods have been successfully synthesized via a simple water–ethyleneglycol (H2O–EG) mixed-solvothermal route, employing lanthanum nitrate (La(NO3)3· xH2O) as a La3+ ion source and monobasic sodium phosphate (NaH2PO4·2H2O) as aPO43- ion source. The as-obtained products were characterized by means of X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), (high resolution) transmission electron microscopy (HR/TEM), selected area electron diffraction (SAED) and field emission scanning electron microscopy (FESEM). Some factors influencing the formation of LaPO4 nanorods, including the reaction temperature, the volume ratio of water/EG and the original amount ofH2PO4- ions, were investigated. Experiments showed that the volume ratio of water/EG and the original amount ofH2PO4- ions could markedly affect the morphology of the final product.
Keywords: LaPO; 4; nanorods; Mixed solvothermal synthesis; Scanning electron microscopy; Optical property
Hierarchical positioning of gold nanoparticles into periodic arrays using block copolymer nanoring templates
by Li Wang; Franck Montagne; Patrik Hoffmann; Harry Heinzelmann; Raphaël Pugin (pp. 496-504).
Electrostatic-driven positioning of gold nanoparticles was achieved in one-step during the spontaneous phase inversion of PS -b-P2VP copolymer micelles into nanorings templates. Gold arrays with tunable dimensions were produced.Display Omitted► Single gold nanoparticles are guided at predetermined positions onto silicon surfaces using a simple self-assembly process. ► Gold arrays with controlled densities and periodicities are produced. ► The positioning method can be used for controlling the assembly of a large variety of nanoscale building blocks onto large scale surfaces.We report a simple and versatile self-assembly method for controlling the placement of functional gold nanoparticles on silicon substrates using micellar templates. The hierarchical positioning of gold nanoparticles is achieved in one-step during the spontaneous phase inversion of spherical poly(styrene)- block-poly(2-vinylpyridine) copolymer micelles into nanoring structures. The placement is mainly driven by the establishment of electrostatic interactions between the nanoparticle ligands and the pyridine groups exposed at the interface. In particular, we show the formation of ordered arrangements of single gold nanoparticles or nanoparticle clusters and demonstrate that their morphologies, densities and periodicities can be tuned by simply varying the initial block copolymer molecular weight or the deposition conditions. Besides gold nanoparticles, the method can be used for controlling the assembly of a large variety of nanoscale building blocks, thus opening an attractive pathway for generating functional hybrid surfaces with periodic nanopatterns.
Keywords: Self-assembly; Block copolymers; Gold nanoparticles; Electrostatic-driven positioning
On the friction coefficient of straight-chain aggregates
by Lorenzo Isella; Yannis Drossinos (pp. 505-512).
Calculated friction coefficients of straight chains composed of k=2–64 spherical monomers for motion parallel (a) and perpendicular (b) to the chain symmetry axis plotted against the number of monomers. Comparison with previous results.Display Omitted► A methodology is proposed to calculate the friction coefficient of aggregates in the continuum regime from the fluid diffusion equation. ► The friction coefficient is related to the ratio of two molecular collision rates. ► The calculated friction coefficients and mobility radius of straight chains are in good agreement with previous results. ► The monomer shielding factors determine the chain friction and diffusion coefficients.A methodology to calculate the friction coefficient of an aggregate in the continuum regime is proposed. The friction coefficient and the monomer shielding factors, aggregate-average or individual, are related to the molecule-aggregate collision rate that is obtained from the molecular diffusion equation with an absorbing boundary condition on the aggregate surface. Calculated friction coefficients of straight chains are in very good agreement with previous results, suggesting that the friction coefficients may be accurately calculated from the product of the collision rate and an average momentum transfer, the latter being independent of aggregate morphology. Langevin-dynamics simulations show that the diffusive motion of straight-chain aggregates may be described either by a monomer-dependent or an aggregate-average random force, if the shielding factors are appropriately chosen.
Keywords: Straight-chain aggregates; Friction coefficient; Diffusion coefficient; Collision rate; Langevin simulations
Application of anisotropic silver nanoparticles: Multifunctionalization of wool fabric
by Bin Tang; Jinfeng Wang; Shuping Xu; Tarannum Afrin; Weiqing Xu; Lu Sun; Xungai Wang (pp. 513-518).
The wool fabrics were modified by anisotropic silver nanoparticles with localized surface plasmon resonance property, presenting different colors. The treated fabrics also show strong antibacterial activity against Escherichia coli.Display Omitted► Anisotropic silver nanoparticles (NPs) are effectively assembled on the wool fibers. ► The assembling process is through the electrostatic interaction. ► Treated wool presents different colors due to optical property of silver NPs. ► Colors of wool fabrics are tunable by changing the morphologies of silver NPs. ► Fabrics treated with silver NPs exhibit obvious antibacterial activity.Anisotropic silver nanoparticles (NPs) were successfully employed to color the wool fabrics in this study. The modified wool fabrics exhibited brilliant colors due to the localized surface plasmon resonance (LSPR) properties of silver NPs. The colors of wool fabrics altered with the morphologies of silver NPs. These modified wool fabrics were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicated that anisotropic silver NPs were effectively assembled on the surface of wool fibers when the solution pH and temperature was about 4 and 40°C, respectively. This assembling of silver NPs on the wool fibers was realized by the electrostatic interaction between wool fibers and silver NPs. This technique was also applied to gold NPs. The fabrics treated with anisotropic silver NPs showed high antibacterial activity against the bacteria of Escherichia coli. This study opens a new approach to color and functionalize conventional textile materials.
Keywords: Functional coatings; Silver nanoparticles; Surface plasmon resonance; Color; Antibacterial; Wool fiber
Effect of Ni cations and microwave hydrothermal treatment on the related properties of layered double hydroxide–ethylene vinyl acetate copolymer composites
by Lili Wang; Bin Li; Mingfei Yang; Chunxia Chen; Yongsheng Liu (pp. 519-525).
The thermal decomposition of OH− andCO32- for NiMgAl-MHT with microwave hydrothermal treatment occurs not only earlier but also faster than that of other LDHs.Display Omitted► We examine the effect of Ni cations and microwave treatment on the properties of LDH-EVA composites. ► The microwave treatment samples MgAl-MHT and NiMgAl-MHT have higher crystallinity. ► NiMgAl-MHT shows the highest hydrophobicity. ► The flame retardance of NiMgAl-MHT-EVA is highest in all composites.The effect of Ni cations and synthetic methods on the crystallinity, morphology, thermal stability and hydrophobic properties of carbonate-containing layered double hydroxides (LDHs) was investigated. The conventional hydrothermal treatment (CHT) and microwave hydrothermal treatment (MHT) methods were used to synthesize LDHs. The microwave treatment LDHs (MgAl-MHT and NiMgAl-MHT) have higher crystallinity and smaller crystal sizes than the conventional hydrothermal treatment LDHs (MgAl-CHT and NiMgAl-CHT). IR results indicate that the interactions of both OH−–CO32- andCO32-–CO32- in NiMgAl-MHT are weaker. Furthermore, the thermal decomposition of OH− andCO32- in the NiMgAl-MHT sample occurred earlier and faster than that of other LDHs. The contact angle values indicate that NiMgAl-MHT has the highest hydrophobicity. The influences of the LDHs on the thermal degradation and flame retardance of ethylene vinyl acetate copolymer (EVA)–LDH composites have also been studied in detail. NiMgAl-MHT has the more homogeneous nano-dispersed layers in EVA matrix. All composites enhance the thermal stability compared with the pure EVA because of the release of H2O and CO2. Flame retardance of NiMgAl-MHT-EVA was obviously higher than that of the pure EVA and other composites.
Keywords: Layered double hydroxides; Polymer; Microwave radiation; Thermal stability; Ethylene vinyl acetate copolymer; Composites
Multifunctional NO-delivery vessel derived from aminopropyl-modified mesoporous zeolites
by Feng Wei; Qian Hou; Jia Yuan Yang; Jian Hua Zhu (pp. 526-535).
Aminopropyl-functionalized mesoporous zeolite adopts a “preadsorption–release–resorption” manner for delivery of NO and capturing of NPYR in a one-step process, which affords a potential multifunctional biochemical vessel for life science.Display Omitted► Both NO release and nitrosamine adsorption are performed simultaneously in mimic gastric juice. ► NO release is acid triggered, so the activation of zeolites vessel is omitted. ► Aminopropyltriethoxysilane modification enables zeolite to release 10 times more NO. ► The zeolite vessel also efficiently traps nitrosamine in gastric juice after releasing NO.A new strategy, releasing nitric oxide (NO) and adsorbing nitrosamines simultaneously by zeolitic materials in the digestive system, is validated in this paper. Three types of moisture-saturated molecular sieves, HZSM-5 zeolite, mesoporous zeolite, and mesoporous silica MCM-41, are used as NO-delivery vessels in mimic gastric juice after modification of γ-aminopropyltriethoxysilane (APTES). APTES modification dramatically increased the capability of zeolite and mesoporous silica in NO release in acidic solution, because more NO can be adsorbed in the composite and stored in the form of nitrite. Some composites released the NO 10 times more than their parent materials, and synchronously captured the carcinogen nitrosamines in mimic gastric juice. The influences of APTES modification on the porous structure and surface state of zeolite and mesoporous silica were investigated by XRD, N2 adsorption, and FTIR tests, through which the mesoporous zeolite is proven to be the optimal support. With this hierarchical material a controllable APTES modification is realized in which a lot of aminopropyl groups are grafted in mesopores while the zeolitic structure is maintained, so the resulting sample exhibits a high capability in releasing NO and adsorbing nitrosamines. This investigation provides a clue for elevating the efficiency of zeolites in the application of life science.
Keywords: NO delivery; Mesoporous zeolite; Aminopropyl functionization; Adsorption of nitrosamines; Bifunctional material
Spontaneous formation of dye-functionalized gold nanoparticles using reverse micellar systems
by Masaki Takahashi; Shuhei Ohno; Norifumi Fujita; Tetsuya Sengoku; Hidemi Yoda (pp. 536-542).
Detailed exploratory and mechanistic investigations on spontaneous formation of dye-functionalized gold nanoparticles using dye-based reverse micellar systems are described in this publication.Display Omitted► Water molecules play a significant role for GNP formations. ► GNPs are assumed to have approximately constant size distributions. ► Photophysical property can be tuned by changing medium polarity. ► Dye-functionalized GNPs exhibit excellent film-forming properties. ► Synthetic protocol has broad applications for dye analogues.Detailed exploratory and mechanistic investigations on spontaneous formation of dye-functionalized gold nanoparticles (GNPs) using dye-based reverse micellar systems are described in this publication. The accumulated results from spectroscopic and microscopic investigations demonstrated that water molecules confined within nanoscopic enclosure of the self-assembled reverse micelles played critical role in the redox processes of aurate ions to produce GNPs, which are assumed to have approximately constant size distributions. The resulting dye-functionalized GNPs were found to offer their absorption and fluorescence emission tunability by changing the medium polarity as well as to exhibit excellent film-forming properties to give optically homogeneous polystyrene thin films. These key findings in addition to broad applicability of the self-assembling process with a variety of dye analogues have led to a conclusion that the protocol presented here serves as a versatile synthetic method to provide a potential convenience for future development of new organic–inorganic hybrid nanomaterials.
Keywords: Hybrid nanomaterial; Gold nanoparticles; Anthracene; Perylene; Spontaneous formationAbbreviations; GNP; gold nanoparticle; NTCA; naphthalene-1,4,5,8-tetracarboxylic dianhydride; PTCA; perylene-3,4,9,10-tetracarboxylic dianhydride; NMP; N; -methylpyrrolidone; THF; tetrahydrofuran; SPR; surface plasmon resonance; W; 0; molar ratio of water to dye molecules; t; s; sonication time for complexation of dye with HAuCl; 4; t; i; incubation time for complexation of dye with HAuCl; 4; r; stoichiometric ratio of HAuCl; 4; /dye
Synthesis of graphene oxide-based biocomposites through diimide-activated amidation
by Jianfeng Shen; Bo Yan; Min Shi; Hongwei Ma; Na Li; Mingxin Ye (pp. 543-549).
A novel and facile method for attachment of biomaterials to graphene oxide sheets was developed. The covalently bonded biomaterial retained its bioactivity.Display Omitted► Diimide-activated amidation was used to attach biomaterials to graphene oxide sheets. ► It causes no denaturing of the biomaterials and guaranties the uniform attachment. ► The same method can be used to introduce GOS into other biosystems.In this work, a novel and facile method for covalent attachment of biomaterials to graphene oxide sheets (GOS) was developed. Four conjugates were obtained via the diimide-activated amidation reaction under ambient conditions. Final products were characterized by FT-IR spectroscopy, atomic force microscopy and transmission electron microscopy. Electrochemical characterization of the composite showed that the covalently bonded biomaterial retained its bioactivity. This method may provide a way for further preparation of graphene-based biodevices.
Keywords: Graphene oxide; Diimide-activated amidation; Biomaterial; Bioactivity
Electrical potentials of two identical particles with fixed surface charge density in a salt-free medium
by Jyh-Ping Hsu; Chih-Hua Huang; Shiojenn Tseng (pp. 550-556).
Electrical distribution for the case of two charged particles in a salt-free medium.Display Omitted► Problem considered simulates a wide class of colloidal systems including micelles. ► Electrical potentials of two planar and nonplanar particles are derived. ► Accurate approximate analytical expressions are obtained. ► Results are readily applicable to the evaluation of electrical energy.The electrical potentials of two identical planar, cylindrical, and spherical particles immersed in a salt-free dispersion are solved analytically by a perturbation approach for the case of constant surface charge density. The system under consideration simulates, for example, micelles, where the ionic species in the liquid phase come mainly from the dissociation of the functional groups on the droplet surface. We show that for planar particles, the present zero-order perturbation solution is exact, and for cylindrical and spherical particles, the first-order perturbation solution provides sufficiently accurate results, with an averaged percentage deviation on the order of 1% under typical conditions. In general, the higher the surface charge density, the higher the valence of counterions, the smaller the separation distance between two particles, and the smaller the curvature of particle surface, the better the performance of the perturbation solution.
Keywords: Electrical potential; Constant surface charge; Two planar, cylindrical, and spherical particles; Salt-free medium; Perturbation solution
Dual-stimuli responsive behaviors of diblock polyampholyte PDMAEMA-b-PAA in aqueous solution
by Zhiying Xiong; Baoliang Peng; Xia Han; Changjun Peng; Honglai Liu; Ying Hu (pp. 557-565).
The proposed model for two PDMAEMA-b-PAA aggregation behavior responded to changes in temperature and pH in aqueous solutions.Display Omitted► PDMAEMA-b-PAA copolymers have pH and thermo dual-stimuli sensitivities. ► Thermal sensitivity of PDMAEMA-b-PAA is reversible. ► LCST varies with solution concentration, pH and thermal-segment lengths. ► LCST can be exactly estimated by surface tension experiment.Two poly(2-(dimethylamino)ethyl methacrylate)-b-poly(acrylic acid) diblock copolymers, PDMAEMA84-b-PAA18 and PDMAEMA50-b-PAA18, were synthesized by the atom transfer radical polymerization (ATRP) and their dual-stimuli responsive behaviors to the changes in temperature and pH in aqueous solutions were investigated by UV–vis spectroscopy, dynamic light scattering (DLS),1H NMR spectroscopy and surface tension measurement. Different from PDMAEMA84-b-PAA18 solutions where no aggregation is observed between pH 7.0 and 9.5, the PDMAEMA50-b-PAA18 aggregates can exist in this broad pH range due to the hydrophobic interactions among the charge-balanced polyampholyte chains. At high pH, e.g., 11.0, the DMAEMA segments collapse to form the core of micelles due to the hydrophobic property of the de-protonized DMAEMA stabilized with the highly ionized AA segments on the surface of the micelles upon heating. At pH around the IEP, e.g., 9.5, large micelles can be formed in PDMAEMA84-b-PAA18 solution upon heating, just like that at pH 11.0, while PDMAEMA50-b-PAA18 first formed the micelles due to the electrostatic attraction between ionized AA segments and protonated DMAEMA segments, but the aggregation of the micelles was hardly happened upon heating due to the smaller DMAEMA segment. Moreover, LCST can be exactly estimated by surface tension experiment.
Keywords: Diblock polyampholyte; Dual-stimuli response; Lower critical solution temperatures (LCST); Aggregation behavior
Aerosol-assisted self-assembly of hybrid Layered Double Hydroxide particles into spherical architectures
by Vanessa Prevot; Claire Szczepaniak; Maguy Jaber (pp. 566-572).
Spray drying technique has been applied to a colloidal suspension of hybrid NiAl-Layered Double Hydroxide prepared by polyol process. Interestingly, the spherical form is maintained upon both thermal treatment and anion exchange.Display Omitted► Spherical hybrid LDH particles are prepared by spray-drying. ► The spherical form is retained under thermal treatment. ► The spherical form is maintained during anionic exchange with DDS.Acetate intercalated NiAl-Layered Double Hydroxide nanoparticles were prepared by polyol process and further used as building blocks to form hybrid LDH spheres by a spray drying technique. The spherical aggregated LDH particles display a polydispersed size with a diameter ranging from 47nm to 2μm. The analysis of the thermal behavior evidenced that the spherical form was maintained upon calcination up to 1100°C, giving rise to derived mixed oxide (NiO+NiAl2O4) nanospheres. Interestingly, the spherical morphology of the LDH materials was also retained during anion exchange process. The replacement of the intercalated acetate anion by of a voluminous anion such as dodecylsulfate induces an increase of the nanosphere mean diameter of 65%. The different materials were deeply characterized using X-ray diffraction, FTIR spectroscopy, scanning and transmission electron microscopies, dynamic light scattering, thermal analysis and nitrogen sorption.
Keywords: Layered Double Hydroxide (LDH); Nanospheres; Aerosol; Polyol process; Hybrid materials
Poorly water-soluble drug nanoparticles via an emulsion-freeze-drying approach
by Neil Grant; Haifei Zhang (pp. 573-578).
Drug nanoparticles are produced by freeze-drying oil-in-water emulsions.Display Omitted► A unique emulsion-freeze-drying approach. ► Poorly water-soluble drug nanoparticles within porous polymer. ► Dissolution of the materials to make aqueous nanoparticles dispersions. ► Size and loading of drug nanoparticles tuneable.Low water solubility of a high percentage of pharmaceuticals is a big issue for pharmaceutical applications due to the resulting low bioabsorption and hence limited therapeutic efficacy. Preparation of drug nanoparticles has been one of the mostly investigated routes to address this problem. In this study, we reported the preparation of nanoparticles via an emulsion-freeze-drying approach. Indomethacin (IMC, a poorly water-soluble drug) nanoparticles were formed in situ within porous poly(vinyl alcohol). The IMC nanoparticles could be released into water to form stable nanodispersions simply by rapid dissolution of the porous polymeric scaffold. This study focused on how preparation conditions including phase volume ratios in the emulsions and the concentrations of polymer, surfactant and drug influenced the formation of IMC nanoparticles. It was concluded that the loading and size of IMC nanoparticles could be easily tuned by changing the preparation conditions.
Keywords: Poorly water-soluble drugs; Nanoparticles; Freeze drying; Emulsion
Dynamic assembly of anionic surfactant into highly-ordered vesicles
by H. Gevgilili; D. Kalyon; E. Birinci; M. Malik; L. Goovaerts; R. Bacon; P. Mort (pp. 579-588).
A combination of pressure and drag flows was used for the dynamic assembly and transformation of the initial spongy lamellar structure of concentrated linear alkylbenzene sulfonate into highly ordered spherulitic vesicles.Display Omitted► Highly-efficient method for dynamic assembly of vesicules is demonstrated. ► Assembly method relies on combination of drag and pressure flows. ► The assembly method mitigates viscoplasticity and wall slip of surfactant paste. ► Backmixing during assembly generates uniform vesicles within 300–600nm. ► Vesicular structure transformation increases elasticity and viscosity.A highly-efficient dynamic assembly method for the transformation of the initial spongy lamellar structure of concentrated linear alkylbenzene sulfonate, LAS, incorporated with sodium silicate, into spherulitic vesicles is presented. A combination of drag and pressure flows, via twin screw extrusion, was used to mitigate the ubiquitous viscoplasticity and the wall slip behavior of the anionic surfactant paste and gave rise to the dynamic assembly of stable vesicular nanostructures within a narrow size range, that was not possible with either pure drag or pure pressure flows. Concomitantly with the structure transformation of the paste during assembly under the combination of pressure and drag flows, significant changes in its viscoelasticity, i.e., order of magnitude increases in storage and loss moduli and magnitude of complex viscosity, were observed. The demonstrated dynamic assembly of stable vesicular nanostructures, with vesicle diameters within the relatively narrow range of 300–600nm, from a commodity surfactant is relevant to myriad templating and encapsulation applications, as well as shedding light on the mechanisms of the deformation-induced planar lamellar to vesicle transformation of concentrated amphiphiles.
Keywords: Surfactant; Alkylbenzene sulfonate; Lamellar; Vesicle; Assembly; Gel; Rheology
Location of anti-TB drugs and microstructural changes in organized surfactant media using optical properties
by S.K. Mehta; Gurpreet Kaur (pp. 589-597).
Microemulsion structure elucidation has been carried out by photophysical properties using hydrophobic (Nile red), hydrophilic (tris(2,2′-bipyridine)ruthenium(II) dichloride), and pyrene as probes. The dyes also act as markers to elucidate the position of anti-TB drugs.Display Omitted► Microstructure elucidation of Tween 80 microemulsions using photophysical properties. ► Microemulsion structural changes have been monitored using pyrene. ► Different hydrophobic and hydrophilic solvatochromic probes have also been employed. ► Dependence of the emission/absorbance of probes on ω was observed. ► These probes have been used to locate the position of anti-Tuberculosis drugs.Microstructure elucidation is a critical step in the understanding of organized surfactant media such as microemulsions. In this work, a systematic approach for revelation of microstructure changes of Tween 80 microemulsion has been carried out using photophysical properties. Microemulsion structural changes have been monitored using pyrene and different solvatochromic probes for the presence of oil-rich, water-rich, and bicontinuous microstructures. The hydrophobic optical probe, Nile red (NR), has been used to report from the side of the oil–surfactant interface and to complement this, a hydrophilic optical probe tris(2,2′-bipyridine)ruthenium(II) dichloride (RC) from the side of the water–surfactant interface. The results show the partitioning of probes into different microenvironments within the system. NR occupies the interface toward the apolar side and RC toward the polar. The analysis also indicates conspicuous dependence of the emission/absorbance behavior of optical probes on the water:surfactant molar ratio ( ω). Quantitative estimates have been obtained for the polarities (ET(30)) of solubilization sites of the probes in different regions of microemulsions and are well correlated with a Stokes shift. Lastly, these probes of different solubilities have been used to locate the position of anti-tuberculosis drugs, i.e., rifampicin (hydrophobic), pyrazinamide, and isoniazid (hydrophilic) of variable solubilities loaded in Tween 80 systems.
Keywords: Non-ionic microemulsion; Fluorescence; Tris(2,2′-bipyridine)ruthenium(II) dichloride; Nile red; Microenvironment; Anti-TB drugs; Water:surfactant molar ratio
Thermodynamic parameters and counterion binding to the micelle in binary anionic surfactant systems
by Atthaphon Maneedaeng; Kenneth J. Haller; Brian P. Grady; Adrian E. Flood (pp. 598-604).
Counterion binding of Na+ and Ca2+ to micelles, and thermodynamic parameters of mixed micellization in mixed-surfactant systems have been measured. Binding has been modeled using a chemical equilibrium model.Display Omitted► A study of micellization behavior in mixed anionic surfactant systems. ► Measurement of Na+ and Ca2+ binding to the micelle using ion-selective electrodes. ► An original model predicts the competitive binding of Na+ and Ca2+. ► The model is able to predict counterion binding of the two ions very successfully.Competitive counterion binding of sodium and calcium to micelles, and mixed micellization have been investigated in the systems sodium dodecylsulfate (NaDS)/sodium decylsulfate (NaDeS) and NaDS/sodium 4-octylbenzenesulfonate (NaOBS) in order to accurately model the activity of the relevant species in solution. The critical micelle concentration (CMC) and equilibrium micelle compositions of mixtures of these anionic surfactants, which is necessary for determining fractional counterion binding measurements, is thermodynamically modeled by regular solution theory. The mixed micelle is ideal (the regular solution parameterβ M=0) for the NaDS/NaOBS system, while the mixed micelle for NaDS/NaDeS hasβ M=−1.05 indicating a slight synergistic interaction. Counterion binding of sodium to the micelle is influenced by the calcium ion concentration, and vice versa. However, the total degree of counterion binding is essentially constant at approximately 0.65 charge negation at the micelle’s surface. The counterion binding coefficients can be quantitatively modeled using a simple equilibrium model relating concentrations of bound and unbound counterions.
Keywords: Mixed anionic surfactants; Regular solution theory; Counterion binding; Sodium dodecylsulfate; Sodium decylsulfate; Sodium 4-octylbenzenesulfonate
Properties of binary surfactant systems of nonionic surfactants C12E10, C12E23, and C12E42 with a cationic gemini surfactant in aqueous solutions
by Changchao Hu; Rongqiang Li; Hui Yang; Jinben Wang (pp. 605-613).
Cryogenic Transmission Electron Microscopy image of micelles and vesicles formed by binary surfactant system of nonionic surfactant and cationic gemini surfactant.Display Omitted► The aggregation properties of three binary surfactant systems were investigated. ► The presence of nonionic surfactants has an effect on CMC and aggregate morphology. ► There are strong synergistic interactions between the constituent surfactant. ► Surfactant composition and PEO chain length affect the aggregation properties. ► The work contributes to understand the aggregation behavior and the mixing effect.Properties of binary surfactant systems of nonionic surfactants poly(ethylene oxide) (PEO) lauryl ethers (C12E10, C12E23, C12E42) with a cationic gemini surfactant, butanediyl-α,ω-bis(tetradecyldimethylammonium bromide) (14-4-14), have been investigated by Steady-state Fluorescence (FL), zeta potential, Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), Cryogenic Transmission Electron Microscopy (CryoTEM), and X-ray Diffraction (XRD). Through FL measurements, critical micelle concentration (CMC) of the three binary systems for different mixing mole fractions is determined and the values fall between those of pure constituent surfactants. Ideal CMC (CMCideal), mole fraction in aggregates ( X), interaction parameter ( β), activity coefficients ( f1 and f2), and excess free energy of mixing (Δ Gex) have been calculated. All these parameters indicate nonideal behavior and synergistic interactions between the constituent surfactants, which is explained in terms of electrostatic attraction between headgroups of constituent surfactants and reduction of electrostatic repulsion between headgroups of 14-4-14 due to the presence of nonionic surfactants. DLS, TEM and CryoTEM results show that nonionic surfactants facilitate the formation of larger aggregates. Micelles and vesicles in larger size compared with those of 14-4-14 coexist in the mixed solutions. Both surfactant composition and PEO chain length are found to play a strong effect on the properties of the binary systems.
Keywords: Binary surfactant system; Nonionic surfactant; Gemini surfactant; Interaction; Aggregate morphology
Unexpected differences in the behavior of ovotransferrin at the air–water interface at pH 6.5 and 8.0
by Cécile Le Floch-Fouéré; Stéphane Pezennec; Michel Pézolet; Jean-François Rioux-Dubé; Anne Renault; Sylvie Beaufils (pp. 614-623).
Surface pressure versus surface concentration for the lowest subphase concentrations for which the surface pressure is initiated at pH 6.5 (filled circles) and pH 8.0 (open squares): a weak barrier to adsorption is evidenced at pH 6.5.Display Omitted► Adsorption is delayed at pH 8.0 (negative charge) and low concentration. ► Stronger interactions in the first steps of adsorption are evidenced at pH 8.0. ► Interfacial shear elastic properties are weak. ► Interfacial ovotransferrin conformation depends on the bulk pH (6.5 or 8.0). ► Protein spectral signature is non standard at pH 8.0.Adsorption of purified apo-ovotransferrin at the air–water interface was studied by ellipsometry, surface tension, polarization–modulation infrared reflection–absorption spectroscopy (PM-IRRAS), and shear elastic constant measurements. No significant difference was observed between pH 6.5 and 8.0 as regards the final value of surface concentration and surface pressure. However at low concentration, a weak barrier to adsorption is evidenced at pH 6.5 and confirmed by PM-IRRAS measurements. At a pH where the protein net charge is negative (pH 8.0), the behavior of ovotransferrin at the air–water interface is more influenced by charge effects rather than bulk concentration effects. At this pH, the interface exhibits a low shear elastic constant and a spectral signature not usual for globular proteins.
Keywords: Protein; Adsorption; Air–water interface; Conformation; Ovotransferrin; Charge
Effect of double quaternary ammonium groups on micelle formation of partially fluorinated surfactant
by Keisuke Matsuoka; Nagisa Chiba; Tomokazu Yoshimura; Emi Takeuchi (pp. 624-629).
Freeze fracture TEM images ofCnFC3-2Am ( n=8 and 10) micelles.Display Omitted►The surfactants are composed of fluorocarbons and double quaternary ammonium groups. ► The divalent head group results in an advantageous increase in their solubility. ► The electrostatic repulsion between divalent cations decreases surface activity. ► The surfactants form small micelles ranging from 10 to 100nm.To investigate the effect of divalency on the micelle properties, we synthesized divalent cationic surfactants composed of fluorocarbons and double quaternary ammonium groups N, N-dimethyl- N-[2-( N′-trimethylammonium)ethyl]-1-(3-perfluoroalkyl-2-hydroxypropyl) ammonium bromide [CnFC3-2Am; where n (=8 or 10) represents the number of carbon atoms in the fluorocarbon chain]. The double quaternary ammonium groups are continuously combined by the ethylene spacer in the surfactant head group, which clearly distinguishes the molecular design of the surfactant from those of the other typical divalent surfactants, bolaform and gemini types. The presence of the divalent head group results in an advantageous increase in their solubility [i.e., rise in the critical micelle concentration (cmc)]; however, the extra electrostatic repulsion between divalent cations decreases the surface activity in comparison with monovalent homologous fluorinated surfactants. The cmc, surface tension at cmc, and area occupied by a surfactant molecule in aqueous solution at 298.2K are 4.32mM, 30.6mNm−1, and 0.648nm2molecule−1, respectively, forC8FC3-2Am, and 1.51mM, 30.4mNm−1, and 0.817nm2molecule−1, respectively, forC10FC3-2Am. The micellar size and shape were investigated by dynamic light scattering and freeze-fracture transmission electron microscopy (TEM). The TEM micrographs show thatCnFC3-2Am ( n=8 and 10) mainly forms ellipsoidal micelles approximately 10–100nm in size for n=8 and approximately 10–20nm in size for n=10. The degree of counterion binding to micelle was determined by selective electrode potential measurements, and the results of 0.7–0.8 agree with the average values for conventional monovalent ionic surfactants.
Keywords: Fluorinated surfactant; Micelle; Divalent surfactant; Fluorocarbon; Surface tension
Properties of ionic liquids containing silver(I) or protic alkylethylenediamine cations with a bis(trifluoromethanesulfonyl)amide anion
by Masayasu Iida; Sayaka Kawakami; Emi Syouno; Hua Er; Eiji Taguchi (pp. 630-638).
Formation of silver(0) nanoparticles by the reaction with aqueous NaBH4 solution depends on a slight difference in the alkyl chains of the silver(I) ionic liquids.Display Omitted► Novel ionic liquids having ethylenediamine head group were prepared. ► Ethyl side-chain is effective on the physical properties of Ag-ILs and PILs. ► Both the hydrogen-bondings and alkyl chains govern the unique properties of PILs. ► Formation of silver nanoparticles depends on the ordering of nanostructures of Ag-ILs.Ionic liquids of an N-alkylethylenediamine-silver(I) complex cation (alkyl=hexyl, 2-ethylhexyl, and octyl) or a protic N-alkylethylenediaminium cation (alkyl=butyl, hexyl, 2-ethylhexyl, octyl, decyl, and dodecyl) with a bis(trifluoromethanesulfonyl)amide counter anion (Ag-ILs and PILs, respectively) were prepared and their physicochemical properties were investigated. The trend of solidification decreased in the order octyl≫hexyl>2-ethylhexyl for the Ag-ILs, and butyl>dodecyl>decyl>octyl>hexyl≫2-ethylhexyl for the PILs. The diffusion coefficients of the cations indicated stronger intermolecular interactions in PILs than in the Ag-ILs because of hydrogen-bonding networks, and it has been revealed that the intermolecular interactions increase in the order, hexyl4 solution, whereas the 2-ethylhexyl and hexyl complexes did not form silver(0) sols. This difference can be attributed to the ordering of the nanostructures in the Ag-ILs.
Keywords: Ionic liquids; Alkylethylenediamines; Silver(I) metal complexes; Silver(0) nanoparticles; Protic ionic liquids; Self-diffusions
Imidazolium camphorsulfonamides: Chiral catanionic liquid crystals with tunable thermal properties
by Eva Rettenmeier; Alexey Tokarev; Christophe Blanc; Philippe Dieudonné; Yannick Guari; Peter Hesemann (pp. 639-646).
The combination of long-chain substituted chiral imidazolium camphorsulfonamide cations with anionic sulfate or sulfonate surfactants yielded catanionic ionic liquid crystals with tuneable thermal properties.Display Omitted► Straightforward synthesis of catanionic ionic liquid crystals bearing chiral camphorsulfonamide groups. ► Formation of lamellar SmA phases. ► Change from separated bilayers in the crystalline state to interdigitated bilayers in the LC state. ► Control of the thermal properties via the alkyl chain lengths on both cation and anion. ► No macroscopic evidence for the formation of chiral mesophases was obtained.We report the synthesis of novel chiral catanionic liquid crystals bearing camphorsulfonamide substructures. The phase behaviour of these long-chain substituted imidazolium sulphates and sulfonates was investigated using X-ray diffraction (XRD), polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). We observed that the phase behaviour clearly depends on the substitution of both cation and anion. The chiral camphorsulfonamide substructures have an unfavourable influence on the formation of liquid crystalline (LC-) phases. Contrary to N, N′-di-alkyl-imidazolium salts, the formation of LC phases was only observed when both cation and anion are substituted with long alkyl chains (C12 or C16). Furthermore, the phase transition temperatures depend on the chain length of the alkyl groups, as higher phase transition temperatures were observed for compounds bearing longer alkyl chains. However, no macroscopic evidence for the formation of chiral mesophases was obtained.
Keywords: Chiral ionic liquids; Liquid crystals; Catanionic surfactants; Camphorsulfonamides
The effects of the addition of the polyelectrolyte, poly(ethyleneimine), on the adsorption of mixed surfactants of sodium dodecylsulfate and dodecyldimethylaminoacetate at the air–water interface
by X.L. Zhang; D.J.F. Taylor; R.K. Thomas; J. Penfold (pp. 647-655).
Surface adsorption for SDS, dodecyl betaine mixtures in presence of PEI at pH 7 showing extreme partitioning in favor of SDS due to the strong surface interaction between SDS and PEI.Display Omitted► Strong adsorption of SDS/dodecyl betaine/PEI mixtures at interface. ► SDS/PEI ion–dipole interaction dominates at high pH. ► At low pH the electrostatic interaction dominates. ► SDS–PEI interaction is dominant.The effects of the addition of the polyelectrolyte, poly(ethyleneimine), PEI, on the adsorption of the mixed surfactants of sodium dodecylsulfate, SDS, and dodecyldimethylaminoacetate, dodecyl betaine, at the air–water interface have been investigated using neutron reflectivity and surface tension. In the absence of PEI the SDS and dodecyl betaine surfactants strongly interact and exhibit synergistic adsorption at the air–water interface. The addition of PEI, at pH 7 and 10, results in a significant modification of the surface partitioning of the SDS/dodecyl betaine mixture. The strong surface interaction at high pH (pH 7 and 10) between the PEI and SDS dominates the surface behavior. For solution compositions in the range 20/80–80/20mol ratio dodecyl betaine/SDS at pH 7 the surface composition is strongly biased towards the SDS. At pH 10 a similar behavior is observed for a solution composition of 50/50mol ratio dodecyl betaine/SDS. This strong partitioning in favor of the SDS at high pH is attributed to the strong ion–dipole attraction between the SDS sulfate and the PEI imine groups. At pH 3, where the electrostatic interactions between the surfactant and the PEI are dominant, the dodecyl betaine more effectively competes with the SDS for the interface, and the surface composition is much closer to the solution composition.
Keywords: Mixed surfactant adsorption; Polyelectrolyte–surfactant mixtures; Sodium dodecylsulphate; Dodecyl betaine; Polyethyleneimine; Air–water interface; Neutron reflectivity; Surface tension
The role of electrolyte and polyelectrolyte on the adsorption of the anionic surfactant, sodium dodecylbenzenesulfonate, at the air–water interface
by X.L. Zhang; D.J.F. Taylor; R.K. Thomas; J. Penfold (pp. 656-664).
Enhanced LAS adsorption at low surfactant concentrations, due to surface complexation with polyelectrolyte, is most pronounced at high pH.Display Omitted► Pronounced adsorption down to low surfactant concentrations. ► Pattern of adsorption is substantially altered by pH and added electrolyte. ► Layered structures at high pH and in the presence of NaCl and CaCl2. ► Surfactant architecture and addition of electrolyte manipulates adsorption.The role of the polyelectrolyte, poly(ethyleneimine), PEI, and the electrolytes NaCl and CaCl2, on the adsorption of the anionic surfactant, sodium dodecylbenzenesulfonate, LAS, at the air–water interface have been investigated by neutron reflectivity and surface tension. The surface tension data for the PEI/LAS mixtures are substantially affected by pH and the addition of electrolyte, and are consistent with a strong adsorption of surface polymer/surfactant complexes down to relatively low surfactant concentrations. The effects are most pronounced at high pH, and this is confirmed by the adsorption data obtained directly from neutron reflectivity. However, the effects of the addition of PEI and electrolyte on the LAS adsorption are not as pronounced as previously reported for PEI/SDS mixtures. This is attributed primarily to the steric hindrance of the LAS phenyl group resulting in a reduction in the ion–dipole attraction between the LAS sulfonate and amine groups that dominates the interaction at high pH.
Keywords: Mixed surfactant adsorption; Polyelectrolyte–surfactant mixtures; Linear alkyl benzene sulfonate; Polyethyleneimine; Air–water interface; Neutron reflectivity; Surface tension; Ion–dipole interaction
Optimizing organoclay stabilized Pickering emulsions
by Yannan Cui; Mhairi Threlfall; Jeroen S. van Duijneveldt (pp. 665-671).
Stable oil-in-water Pickering emulsions were formed using hydrophilic surfactant pre-treated montmorillonite particles. The clay platelets were found to be lying flat at the water oil interface using polarizing microscopy..Display Omitted► Montmorillonite treated with quaternary amine surfactants was used in Pickering emulsions. ► The most hydrophilic surfactant Berol formed the most stable and mono-disperse emulsions. ► Polarizing microscopy showed the clay platelets were lying flat at the water oil interface. ► The clay particles at the water oil interface formed stacks.Oil-in-water emulsions were prepared using montmorillonite clay platelets, pre-treated with quaternary amine surfactants. In previous work, cetyl trimethylammonium bromide (CTAB) has been used. In this study, two more hydrophilic quaternary amine surfactants, Berol R648 and Ethoquad C/12, were used and formed Pickering emulsions, which were more stable than the emulsions prepared using CTAB coated clay. The droplets were also more mono-disperse. The most hydrophilic surfactant Berol R648 stabilizes the emulsions best. Salt also plays an important role in forming a stable emulsion. The droplet size decreases with surfactant concentration and relatively mono-disperse droplets can be obtained at moderate surfactant concentrations. The time evolution of the droplet size indicates a good stability to coalescence in the presence of Berol R648. Using polarizing microscopy, the clay platelets were found to be lying flat at the water oil interface. However, a significant fraction (about 90%) of clay stayed in the water phase and the clay particles at the water–oil interface formed stacks, each consisting of four clay platelets on average.
Keywords: Pickering emulsions; Montmorillonite; Hydrophilic surfactant; Adsorption; Emulsion stability; Clay orientation
A critical assessment of capillary condensation and evaporation equations: A computer simulation study
by A. Wongkoblap; D.D. Do; G. Birkett; D. Nicholson (pp. 672-680).
Snap shot of argon particles in a carbon nanotube.Display Omitted► Critical assessment of the commonly used Kelvin and Cohan equations. ► The molar volume and surface tension in a pore space differ from the bulk phase. ► The pore size derived from the Kelvin equation is less than the correct pore size.Grand Canonical Monte Carlo simulation (GCMC) is used to study the capillary condensation and evaporation of argon adsorption in finite-length carbon cylindrical nanopores. From the simulation results of local density distributions in the radial and axial directions we obtain the contact angle and the core radii just before condensation and just after evaporation. These are then used in the Kelvin equation (evaporation) and Cohan equation (condensation) to obtain the product of surface tension and liquid molar volume. This product is found to be always greater than for the bulk liquid. We test this deviation with pores of different length and radius and find that both affect the derived product of surface tension and liquid molar volume. The implication of this finding is that if the values of surface tension and liquid molar volume of the bulk phase are used in the Kelvin equation the pore radius will be underestimated. For argon adsorption in cylindrical pores we propose that the Kelvin and Cohan equations should be modified to take account of the difference between the fluid in the adsorbed phase in the confined space and that in the bulk phase.
Keywords: Adsorption; Argon; Contact angle; Finite length; Kelvin equation
The use of dielectric spectroscopy for the characterisation of polymer-induced flocculation of core–shell particles
by Peter Vittrup Christensen; Morten Lykkegaard Christensen; Kristian Keiding (pp. 681-689).
The figure shows the dieelectric relaxation time of core–shell particles as a function of added polymer. The changes are caused by the collapse of the shell and the aggregation of the particles.Display Omitted► Aggregation of core–shell particles causes an increase in the dielectric relaxation time. ► Charge neutralisation of core–shell particles results in a decrease in the magnitude of the dielectric dispersion. ► Aggregation of core–shell particles causes an increase in the magnitude of the dielectric dispersion.Flocculation is an important process in separation science, but only few methods are available for on-line evaluation of the process. Recently, it has been shown that dielectric spectroscopy can be used to characterise the flocculation process of hard polystyrene particles. As many “real life” suspensions contain particles covered with a porous layer of organic material, it is of interest to investigate the potential of dielectric spectroscopy to characterise the flocculation of such suspensions as well. In this paper dielectric spectroscopy is used to investigate the flocculation process of core–shell particles. The flocculation process is characterised using a photometric dispersion analyser as a reference method, and the results are compared to the dielectric dispersions measured by dielectric spectroscopy. It is found that the use of the relaxation time of the dielectric dispersion for an evaluation of the flocculation process is commensurate with the use of the photometric dispersion analyser. Furthermore, the magnitude of the dielectric dispersion is observed to decrease as the charge of the core–shell particles is neutralised. Dielectric spectroscopy is thus found to have potential as an on-line flocculation monitor.
Keywords: Aggregation; Dielectric spectroscopy; Dielectric dispersion; Core–shell particle; PolyDADMAC polymer; Relaxation time
Adsorption and wetting characterization of hydrophobic SBA-15 silicas
by Frank Bernardoni; Alexander Y. Fadeev (pp. 690-698).
P123+TEOS+(EtO)3SiC nH2 n+1.Display Omitted► A series of alkyl-SBA-15 silicas were prepared by grafting and co-condensation. ► While bulk composition was similar, surface properties of silicas were different. ► Grafting produced high quality hydrophobic silicas with uniform pores. ► Co-condensation yielded materials with disordered pores and heterogeneous surfaces.This work describes adsorption and wetting characterization of hydrophobic ordered mesoporous silicas (OMSs) with the SBA-15 motif. Three synthetic approaches to prepare hydrophobic SBA-15 silicas were explored: grafting with (1) covalently-attached monolayers (CAMs) of C nH2 n+1Si(CH3)2N(CH3)2, (2) self-assembled monolayers (SAMs) of C nH2 n+1Si(OEt)3, and (3) direct (“one-pot”) co-condensation of TEOS with C nH2 n+1Si(OEt)3 in presence of P123 ( n=1–18). The materials prepared were characterized by nitrogen adsorption, TEM, and chemical analysis. The surface properties of the materials were assessed by water contact angles (CAs) and by BET C constants. The results showed that, while loadings of the alkyl groups (%C) were comparable, the surface properties and pore ordering of the materials prepared through different methods were quite different. The best quality hydrophobic surfaces were prepared for SBA-15 grafted with CAMs of alkylsilanes. For these materials, the water CAs were above ∼120°/100° (adv/rec) and BET C constants were in the range of ∼15–25, indicating uniform low-energy surfaces of closely packed alkyl groups on external and internal surfaces of the pores respectively. Moreover, surfaces grafted with the long-chained (C12–C18) silanes showed super-hydrophobic behavior (CAs∼150–180°) and extremely low adhesion for water. The pore uniformity of parental SBA-15 was largely preserved and the pore volume and pore diameter were consistent with the formation of a single layer of alkylsilyl groups inside the pores. Post-synthesis grafting of SBA-15 with SAMs worked not as well as CAMs: the surfaces prepared demonstrated lower water CAs and higher BET C constants, thereby indicating a small amount of accessible polar groups (Si–OH) related to packing constrains for SAMs supported on highly curved surfaces of mesopores. The co-condensation method produced substantially more disordered materials and less hydrophobic surfaces than any of the grafting methods. The surfaces of these materials showed low water CAs and high BET C constants (∼100–200) thereby demonstrating a non-uniform surface coverage and presence of unmodified silica. It is concluded that CAMs chemistry is the most efficient approach in preparation of the functionalized OMS materials with uniform surfaces and pores.
Keywords: SBA-15; Alkylsilane; Hydrophobic; Nitrogen adsorption; Water contact angle
The pH-dependence and reversibility of uranium and thorium binding on a modified bauxite refinery residue using isotopic exchange techniques
by M.W. Clark; J.J. Harrison; T.E. Payne (pp. 699-705).
The figure shows that the proportions of initially sorbed238U against the exchange isotope232U (as UVI) are linear over the sample pHs investigated. However, up to 16% of the238U is irreversibly bound to the solids during the initial loading. Moreover the higher the initial loading the greater bound. This increase is because of the development of higher concentration gradients and increased intra-particle diffusion. In mixed238U and232Th loadings,232Th appears to reduce the irreversible binding of238U most likely through competition for binding sites.Display Omitted► Thorium binding to MBRR’s is irreversible over pH range 3–8. ► Uranium binding is largely reversible, but up to 16% is irreversibly bound. ► U binding is restricted over a narrow pH range, pH 6–7. ► U and Th compete for similar sites as mixed U/Th sample reduces irreversibility. ► Irreversible U binding likely from intra-particle diffusion.The pH-dependence and reversibility of uranium and thorium binding onto a modified bauxite refinery residue (MBRR) were studied in laboratory uptake/leaching experiments. Natural238U and232Th isotopes were contacted with MBRR in an 8day loading period (equilibrium pH≈8.5) then leached in pH-dependent experiments, where the pH was decreased from 8 to 3 over several hours following addition of exchange isotopes232U and229Th. Relative concentrations of the thorium isotope pair (232Th and229Th) indicate that Th is very strongly bound to MBRR, and although at pH 3, some de-sorption is observed232Th (≈3%) and229Th (≈2.5%), released thorium is partially re-adsorbed during an overnight equilibration. During the initial equilibration, approximately 50% of the238U was adsorbed, and a U adsorption maximum occurs between pH 5 and pH 6, where <0.5% of the U remains in solution. However, at a pH between 5 and 3, some 60% of the bound U releases, hence the pH range of maximum U retention on the MBRR is relatively narrow. When equilibrated overnight, the MBRR releases additional U, suggesting a kinetically controlled de-sorption linked to mineral dissolution. Plots of U isotope exchange between232U and238U are linear, and suggest that U adsorption is mostly reversible. Data for adsorption in mixed systems of U and Th suggest that Th and U compete for similar binding sites.
Keywords: Adsorption; Radio-nuclides; Sequestration; Red mud; Isotopic exchange; Static titration
Tin oxide (SnO2) nanoparticles/electrospun carbon nanofibers (CNFs) heterostructures: Controlled fabrication and high capacitive behavior
by Jingbo Mu; Bin Chen; Zengcai Guo; Mingyi Zhang; Zhenyi Zhang; Changlu Shao; Yichun Liu (pp. 706-712).
The SnO2/CNFs heteroarchitectures are successfully fabricated by combining the electrospinning technique and the hydrothermal method showing high capacitive behavior as the electrode materials for supercapacitors.Display Omitted► Easy synthesis of SnO2/CNFs heteroarchitectures. ► Controllable SnO2 nanoparticles on the surfaces of the CNFs. ► The SnO2/CNFs heterostructures possess excellent capacitive performance.Tin oxide (SnO2)/carbon nanofibers (CNFs) heterostructures were fabricated by combining the versatility of the electrospinning technique and template-free solvent–thermal process. The results revealed that the SnO2 nanostructures were successfully grown on the primary electrospun carbon nanofibers substrates. And, the coverage density of SnO2 nanoparticles coating on the surface of the CNFs could be controlled by simply adjusting the mass ratio of CNFs to SnCl4·5H2O in the precursor during the solvent–thermal process for the fabrication of SnO2/CNFs heterostructures. The electrochemical performances of the SnO2/CNFs heterostructures as the electrode materials for supercapacitors were evaluated by cyclic voltammetry (CV) and galvanostatic charge–discharge measurement in 1M H2SO4 solution. At different scan rates, all the samples with different coverage densities of SnO2 showed excellent capacitance behavior. And, the sample CS2 (the mass ratio of CNFs to SnCl4·5H2O reached 1:7) exhibited a maximum specific capacitance of 187F/g at a scan rate of 20mV/s. Moreover, after 1000 cycles, the specific capacitance retention of this sample was over 95%. The high capacitive behavior could be ascribed to the low resistance of SnO2/CNFs heterostructures and rapid transport of the electrolyte ions from bulk solution to the surface of SnO2.
Keywords: Electrospinning; Carbon nanofibers; Tin oxide; Heterostructures; Electrochemical performance
Thermodynamic quantities of surface formation of aqueous electrolyte solutions X. Aqueous solution of 2:1 valence-type salts
by Norihiro Matubayasi; Ken Takayama; Ryoko Ito; Ryusei Takata (pp. 713-717).
Surface tension increments of 2:1 valence-type salts were studied in comparison with those of other type.Display Omitted► An aqueous solution of 2:1 valence-type salts show larger increments in surface tension than 1:1 type salts. ► The surface tensions of solutions of calcium salts were found to increase in the order CaCl2>CaBr2>CaI2. ► Cations of 2:1 type salts have a less pronounced effect on surface tension than the halide anions.The behaviors of a series of calcium halides and of alkali earth metal chlorides in the air/water surface region were studied in comparison with those of alkali metal halides by measuring the surface tension increments of solutions. The effect of salts with divalent cations on the surface tension increments is more pronounced than that of uni-univalent salts, but there are some similarities between these two types. It seems that the anions cause a marked effect on surface tension which is proportional to the magnitude of hydration in the bulk water. We also observed a decrease in the entropy change of surface formation with increasing concentration. The importance of an electrical double layer at the surface is discussed in relation to these surface tension increments.
Keywords: Surface tension; Electrolyte solutions; Electrical double layer
Adsorption on montmorillonite prevents oligomerization of Bt Cry1Aa toxin
by N. Helassa; M. Revault; H. Quiquampoix; P. Déjardin; S. Staunton; S. Noinville (pp. 718-725).
Adsorption of multi-domains Cry1Aa toxin on clay depends on its monomeric state (A) or oligomeric states (B).Display Omitted► Oligomerization of Cry1Aa toxin: solution vs. adsorbed state. ► The Cry1Aa toxin, prone to oligomerization in solution, is retained on the clay in its native form. ► Two types of oligomers at pH 7 and pH 10.4 are adsorbed with small conformational changes.The adsorption of the insecticidal Cry1Aa protein from Bacillus thuringiensis ( Bt-toxin) on a model clay surface was studied to understand the structural changes of the protein induced by the clay surface. We studied the adsorption of the monomeric and soluble oligomeric forms of the Cry1Aa toxin as a function of pH and ionic strength conditions on montmorillonite, which is an electronegative phyllosilicate. Cry1Aa secondary structure was determined from the amide I′ FTIR absorption profiles. Accessibility to the solvent was determined by NH/ND exchange to characterize conformational flexibility of the different states of the Cry1Aa protein. The size distribution of Cry1Aa solutions was obtained by dynamic light scattering (DLS). From combined DLS and FTIR measurements, we conclude that montmorillonite traps the Cry1Aa toxin in its monomeric state, preventing the oligomerization of the protein. The oligomeric forms were adsorbed onto the clay without significant structural changes.
Keywords: Protein adsorption; Bacillus thuringiensis; Cry1Aa toxin; Conformational change; Oligomerization; Fourier transform infrared spectroscopy
In situ growth of CuS thin films on functionalized self-assembled monolayers using chemical bath deposition
by Yongjuan Lu; Xu Meng; Gewen Yi; Junhong Jia (pp. 726-733).
The –N of APTS–SAMs can form complexes with Cu2+ in the planting solutions, and then, the heterogenous nucleation reaction incessantly takes place on the interface.Display Omitted► CNH2-terminated SAMs is required in order to obtain CuS thin films with good quality. ► The CuS films on the APTS-SAMs show obvious photoelectrochemical response. ► The growth of CuS on the varying SAMs surface shows different deposition mechanisms.Nano-structured CuS thin films were deposited on the functionalized –NH2-terminated self-assembled monolayers (SAMs) surface by chemical bath deposition (CBD). The deposition mechanism of CuS on the –NH2-terminated group was systematically investigated using field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS), UV–vis absorption. The optical, electrical and photoelectrochemical performance of CuS thin films incorporating with the X-ray diffraction (XRD) analysis confirmed the nanocrystalline nature of CuS with hexagonal crystal structure and also revealed that CuS thin film is a p-type semiconductor with high electrical conductivity (12.3Ω/□). The functionalized SAMs terminal group plays a key role in the deposition of CuS thin films. The growth of CuS on the varying SAMs surface shows different deposition mechanisms. On –NH2-terminated surfaces, a combination of ion-by-ion growth and cluster-by-cluster deposition can interpret the observed behavior. On –OH- and –CH3-terminated surfaces, the dominant growth mechanism on the surface is cluster-by-cluster deposition in the solution. According to this principle, the patterned CuS microarrays with different feature sizes were successfully deposited on –NH2-terminated SAMs regions of –NH2/–CH3 patterned SAMs surface.
Keywords: Copper sulfide; Chemical bath deposition; Self-assembled monolayer; Selective deposition
Fabrication and characterization of core/shell structured TiO2/polyaniline nanocomposite
by Sitao Yang; Yoshie Ishikawa; Hiroshi Itoh; Qi Feng (pp. 734-740).
A core/shell structured TiO2/polyaniline nanocomposite was fabricated by grafting aniline on aminobenzoate monolayer that is chemically adsorbed on the TiO2 nanocrystal surface.Display Omitted► A novel core/shell structured TiO2/polyaniline nanocomposite was prepared. ► The shell thickness in the nanocomposite can be controlled in a few nanometers. ► The nanocomposite can be applied to a new type of dye-sensitized solar cell.A novel core/shell structured TiO2/polyaniline nanocomposite was fabricated by grafting aniline on aminobenzoate monolayer that is chemically adsorbed on the TiO2 nanocrystal surface. The formation and nanostructure of the nanocomposite were investigated by FT-IR and UV–Vis spectra, TEM, FE-SEM, and TG–DTA analysis. Adsorption of aminobenzoate on the TiO2 surface is an effective method to obtain the uniform nanocomposite. The thickness of polyaniline layer coating on the TiO2 nanocrystal surface can be controlled in a range of 2–5nm by this method. A photoelectrochemical study was carried out on the TiO2/polyaniline nanocomposite, and found that polyaniline in the nanocomposite acted as a visible-light sensitizer in a photoelectrochemical reaction. The sensitization effect increased with increasing binding strength between polyaniline and TiO2. A dye-sensitized solar cell with a short circuit current density of 0.19mA/cm2 and an open circuit voltage of 0.35V was fabricated by using the TiO2/polyaniline nanocomposite film as a sensitized electrode.
Keywords: TiO; 2; /polyaniline nanocomposite; Chemical absorption; Photoelectrochemical reaction; Sensitization effect
Characterization of hexavalent chromium interaction with Sargassum by X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and quantum chemistry calculation
by Yu-Ming Zheng; Tao Liu; Jianwen Jiang; Lei Yang; Yanping Fan; Andrew T.S. Wee; J. Paul Chen (pp. 741-748).
During the biosorption of Cr(VI) onto Sargassum biomass, it was reduced to Cr(III) and coordinated with oxygen from either carboxyl or hydroxyl groups to form octahedral structural metal complexes.Display Omitted► Biosorption of Cr(VI) onto seaweed adsorbent was highly pH dependent. ► The adsorbed Cr(V) was reduced to Cr(III) by the biomass. ► The reduced Cr(III) coordinated with oxygen atoms to form octahedral structural metal complexes. ► QC calculation indicated that Cr(III) may complex with carboxyl and/or hydroxyl groups. ► A three-step removal mechanism of Cr(VI) by Sargassum was confirmed.Hexavalent chromium represents higher toxicity in aqueous solutions. It can be removed by such low-cost biosorbents as Sargassum sp. In this study, X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and quantum chemistry (QC) calculation were used to study the interactions between hexavalent chromium and Sargassum sp. during the biosorption. It was found that most of the adsorbed Cr(VI) ions were reduced to Cr(III) after the biosorption. The electrons for the reduction of Cr(VI) were possibly supplied from the Sargassum biomass, some organic compounds of which were oxidized. Cr(III) ions were coordinated with the oxygen atoms from either carboxyl or hydroxyl functional groups to form an octahedral structural metal complex. The coordination numbers of the formed Cr complex were 4–6, and bond length of Cr–O was 1.98Å. QC calculation proved the possible formation of the Cr(III) metal complex, and revealed that carboxyl from biomass could be strongly bound with Cr(III). A three-step removal mechanism of Cr(VI) by Sargassum was proposed.
Keywords: Biosorption; Chromium; Complexation; Spectroscopic analysis; Quantum chemistry calculation; Reduction
Highly efficient adsorbents of poly( o-phenylenediamine) solid and hollow sub-microspheres towards lead ions: A comparative study
by J. Han; J. Dai; R. Guo (pp. 749-756).
Adsorption behaviors of PoPD hollow and solid sub-microspheres towwards Pb(ІІ) ions in water have been investigated in detail, where enhanced adsorption performances of P oPD hollow sub-microspheres have been evidenced..Display Omitted► P oPD hollow and solid sub-microspheres with similar size have been synthesized. ► Comparative adsorption properties of Pb(ІІ) ions onto P oPD have been investigated. ► P oPD also show high adsorption capacity for other heavy-metal ions.Two kinds of different-shaped poly( o-phenylenediamine) (P oPD) polymers: solid and hollow sub-microspheres with both size of about 700nm synthesized by a solution route without any additional directing agents, were employed as efficient adsorbents for removal of Pb(ІІ) ions from water. Firstly, chemical structures of P oPD sub-microspheres were performed by Fourier-transform infrared (FT-IR), UV–vis,1H NMR spectra, X-ray diffraction (XRD) and GPC analysis. When used as adsorbents, both P oPD hollow and solid sub-microspheres showed high adsorptivity and adsorption capacity towards Pb(ІІ) ions in water, and mechanisms of adsorption behaviors were revealed by XRD and X-ray photoelectron spectra (XPS). It was found that the pH and concentration of Pb(ІІ) ion solution, as well as contact time and adsorbent dosage affect the degree of adsorption. Adsorption isotherms and kinetics of Pb(ІІ) ions onto P oPD sub-microspheres were also investigated according to experimental data. Comparative investigations of adsorption behaviors revealed that hollow sub-microspheres showed enhanced adsorptivity adsorption capacity towards Pb(ІІ) ions as compared with solid sub-microspheres typical at low adsorbent dosage. P oPD hollow sub-microspheres also showed good adsorptivity for other heavy-metal ions, such as Hg(ІІ), Cd(ІІ) and Cu(ІІ), which implied their potential applications as effective adsorbents for heavy-metal ions in water.
Keywords: Adsorption; Conducting polymer; Hollow microspheres; Lead ions; Morphology
The application of novel spindle-like polypyrrole hollow nanocapsules containing Pt nanoparticles in electrocatalysis oxidation of nicotinamide adenine dinucleotide (NADH)
by Hui Mao; Yongxin Li; Xincai Liu; Wanjin Zhang; Ce Wang; Salem S. Al-Deyab; Mohamed El-Newehy (pp. 757-762).
Novel spindle-like polypyrrole hollow nanocapsules containing Pt nanoparticles can be successfully prepared and acted as a good steady electrode material for electrocatalytic oxidation of NADH.Display Omitted► A novel Pt NPs/PPy composite hollow nanospindles were fabricated. ► The chemical structure of the Pt NPs/PPy composite hollow nanospindles was studied. ► The composite hollow nanospindles showed good electrocatalysis oxidation of NADH.Novel spindle-like polypyrrole hollow nanocapsules containing Pt nanoparticles (Pt NPs/PPy composite hollow nanospindles) were successfully prepared by using beta-akaganeite (β-Fe3+O(OH,Cl)) nanospindles as templates and methanoic acid as a reducing agent. The β-Fe3+O(OH,Cl) templates can be easily obtained in ethanol/water mixing solution in the presence of thiophene and FeCl3·6H2O, and after coating by PPy shell, they can be gradually and completely etched during the reduction of H2PtCl6 into Pt nanoparticles (Pt NPs) with the average size of 3.6nm on spindle-like polypyrrole hollow nanocapsules, which could still keep their integrality of morphologies with the thickness of PPy shell of 18–20nm. The investigation of Pt NPs/PPy composite hollow nanospindles modified glassy carbon electrode (GCE) for the application to detect nicotinamide adenine dinucleotide (NADH) with cyclic voltammetry (CV) and amperometry indicated good linearity and sensitivity of responses in the certain range of NADH concentration. The influence of Pt NPs content to the NADH oxidation current was also studied. This new kind of unique spindle-like noble metal/conducting polymer hollow nanostructured complex can be acted as a good steady electrode material for electrocatalytic oxidation of NADH.
Keywords: Conducting polymers; Polypyrrole; Beta-akaganeite; Nanocapsules; Pt nanoparticles; Electrocatalysis
On the shape of a hydrostatic meniscus attached to a corrugated plate or wavy cylinder
by A.I. Hill; C. Pozrikidis (pp. 763-774).
Shape of an interface attached to a vertical plate with periodic corrugations for contact angle π/4.Display Omitted► Physical description of the meniscus shape attached to an irregular surface. ► Asymptotic analysis of the meniscus shape attached to a wavy vertical plate. ► Asymptotic analysis of the meniscus shape attached to a wavy cylinder. ► Numerical solutions of the meniscus shape attached to a corrugated vertical plate.The shape of a hydrostatic meniscus attached at a fixed contact angle to a vertical plate or circular cylinder with periodic corrugations is studied by analytical and numerical methods, and the effect of wall irregularities on the shape of the contact line and vertical component of the capillary force is discussed. An asymptotic analysis for a plate with small-amplitude sinusoidal corrugations is carried out to first order with respect to the corrugation amplitude, and a boundary-value problem is formulated and solved by a shooting method to determine the meniscus shape and elevation of the contact line. The meniscus attached to a corrugated plate with rounded corners produced by a Schwarz–Christoffel mapping function for a triangular wave is considered by numerical methods. The Laplace–Young equation determining the meniscus shape is solved in orthogonal curvilinear coordinates generated by conformal mapping using a finite-difference method. The numerical results are successfully compared with the predictions of the perturbation expansion for small amplitudes and discussed with reference to the rise of a meniscus inside a dihedral angle for large amplitudes. A companion asymptotic analysis is presented for a meniscus outside a vertical circular cylinder with small-amplitude sinusoidal corrugations. The analytical predictions are successfully compared with numerical solutions of the Laplace–Young equation for a meniscus outside an elliptical cylinder with aspect ratio near unity, regarded as a deformed circle.
Keywords: Hydrostatic meniscus; Laplace–Young equation; Asymptotic expansions; Conformal mapping; Dihedral corner
J-aggregation of a sulfonated amphiphilic porphyrin at the air–water interface as a function of pH
by Gustavo de Miguel; Kohei Hosomizu; Tomokazu Umeyama; Yoshihiro Matano; Hiroshi Imahori; Marta Pérez-Morales; María T. Martín-Romero; Luis Camacho (pp. 775-782).
The aggregation of (OD)3TPPS3 in MONOLAYERS at neutral and acid pHs is triggered by ZWITTERION formation, whereas in the basic subphase, aggregation is reversibly controlled by applying surface pressure.Display Omitted► The amphiphilic porphyrin ((OD)3TPPS3) forms stable mono-molecular layers at the air–water interface under different conditions of pH. ► J-aggregation is triggered by electrostatic interactions and may be reversibly controlled as a function of pH. ► The splitting of the Soret band is also affected by the subphase pH. π– A isotherms, ellipsometric measurements, Brewster angle microscopy (BAM) and reflection spectroscopy have been utilized to characterize the films of an amphiphilic porphyrin ((OD)3TPPS3) at the air–water interface as a function of pH. This porphyrin forms stable mono-molecular layers at such interfaces, and exhibits different J-aggregation as a function of pH. The J-aggregation of (OD)3TPPS3 on neutral pH subphases is notable considering that the nitrogen atoms at the central macrocycle have a p Ka≈4.9. The type of aggregates at neutral pH is like those detected at pH<4, because the central porphyrin ring is already protonated. However at basic pH the aggregation happens without protonation of the central ring but can be instead controlled by application of the surface pressure. At the air–water interface, (OD)3TPPS3 shows two bands, a red component and a blue component, which have characteristics of non-degenerate linear oscillators being perpendicularly polarized between each other. The spectral behavior observed on subphases at different pHs is qualitatively interpreted by means of exciton coupling theory, assuming that the degenerate transitions attributed to the Soret band are split. Additionally, highly oriented molecular films of these J-aggregates were deposited onto transparent quartz slides.
Keywords: J; -aggregation; Soret band splitting; Porphyrinoids; Air–water interface; pH; Thin films
Temperature-assisted photochemical construction of CdS-based ordered porous films with photocatalytic activities on solution surfaces
by Zhenxun Huang; Fengqiang Sun; Yu Zhang; Kaiyuan Gu; Xueqiong Zou; Yuying Huang; Qingsong Wu; Zihe Zhang (pp. 783-789).
Free-standing CdS/Cd and CdS ordered porous films were controlled to be prepared by a temperature-assisted photochemical strategy. They showed regular variations of photocatalytic activities with changes of compositions.Display Omitted► Photochemical method was first used to construct semiconductor ordered porous film. ► These films were prepared on a precursor solution surface. ► Temperature could control the type of the interface and the compositions of films. ► Free-standing ordered porous films were first used in photocatalysis. ► Properties of films showed regular variations with the compositions.Taking a colloidal monolayer floating on the surface of a precursor solution as template, free-standing CdS/Cd composites and pure CdS (CdS-based) ordered porous films had been prepared by a temperature-assisted photochemical strategy. After irradiation with UV-light and heat treatment, the films formed hemi-spherical pores due to the preferable deposition of CdS and Cd onto the PS spheres during the photochemical and interfacial reactions. When the temperature increased from 15 to 60°C, the air/water interface gradually changed into a vapor/water interface on the surface of the solution, resulting in variations of the final compositions. The optical properties of the films were hence changed. Because of the free-standing characteristic, the ordered porous films were first transferred on surface of polluted solutions as photocatalysts, which was a new mode in application of photocatalysts. The photocatalytic activities of films showed regular variations with the compositions in photodegradation of Rhodamine B. This method provides a simple route for tuning the properties of porous films through control of its composition and a flexible application of films on any surface.
Keywords: Photochemical preparation; Ordered porous film; CdS; Photocatalysis
Crystallization of calcium sulfate on polymeric surfaces
by Nancy H. Lin; Wen-Yi Shih; Eric Lyster; Yoram Cohen (pp. 790-797).
The kinetics of gypsum surface crystallization on polymeric surfaces was studied using a quartz crystal microbalance demonstrating the importance of both surface topography and chemistry on crystal nucleation and growth.Display Omitted► Gypsum crystallization on polymeric surfaces was evaluated via QCM measurements. ► Gypsum mass density, for same surfaces polarity, was lower for smoother surfaces. ► Surface chemical functionality impacts surface crystallization.Surface crystallization of calcium sulfate dihydrate (gypsum) on a series of polymeric surfaces was studied using a quartz microbalance system. Polyelectrolyte multilayer films (positively and negatively charged surfaces) were formed on the quartz crystal microbalance (QCM) sensors utilizing a layer-by-layer spin-assembly method. The kinetics of gypsum surface crystallization was quantified in terms of the evolution of gypsum mineral scale on the different surfaces. For comparison mineral scaling was also evaluated on silica and polyamide surfaces. For surfaces of the same charge polarity (+/-), the mass density of gypsum scale was lower (PSS
Keywords: Surface crystallization; Calcium sulfate dihydrate; Polymer surfaces; Quartz crystal microbalance; Mineral scaling
Micelle formation of nonionic surfactants in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate: Surfactant chain length dependence of the critical micelle concentration
by Tohru Inoue; Haruka Yamakawa (pp. 798-802).
The effect of hydrocarbon chain length on cmc of C nE m is much weaker in bmimBF4 than in aqueous solution, whereas that of polyoxyethylene chain length is slightly stronger in bmimBF4 than in aqueous solution.Display Omitted► POE-type nonionic surfactants form micelles in imidazolium-based IL, bmimBF4. ► The effect of hydrocarbon chain length on the cmc is much weaker than in aqueous systems. ► The effect of POE chain length on the cmc is slightly stronger than in aqueous systems. ► Solvophobic interactions between hydrocarbon chains induce surfactant self-assembly in bmimBF4.Micellization behavior was investigated for polyoxyethylene-type nonionic surfactants with varying chain length (C nE m) in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4). Critical micelle concentration (cmc) was determined from the variation of1H NMR chemical shift with the surfactant concentration. The logarithmic value of cmc decreased linearly with the number of carbon atoms in the surfactant hydrocarbon chain, similarly to the case observed in aqueous surfactant solutions. However, the slope of the straight line is much smaller in bmimBF4 than in aqueous solution. Thermodynamic parameters for micelle formation estimated from the temperature dependence of cmc showed that the micellization in bmimBF4 is an entropy-driven process around room temperature. This behavior is also similar to the case in aqueous solution. However, the magnitude of the entropic contribution to the overall micellization free energy in bmimBF4 is much smaller compared with that in aqueous solution. These results suggest that the micellization in bmimBF4 proceeds through a mechanism similar to the hydrophobic interaction in aqueous surfactant solutions, although the solvophobic effect in bmimBF4 is much weaker than the hydrophobic effect.
Keywords: Micellization in ionic liquid; Nonionic surfactant; Ionic liquids; cmc; Thermodynamics of micellization; Solvophobic interaction