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Journal of Colloid And Interface Science (v.361, #1)

Cover 1 (pp. ofc).

A molecular simulation of interactions between graphene nanosheets and supercritical CO2 by Bin Wu; Xiaoning Yang (pp. 1-8).
The interactions between supercritical CO2 and graphene have been simulated. Higher density scCO2 can provide a stronger solvent-induced free energy barrier due to the increased number of single-layer confined CO2 molecules between graphene sheets.Display Omitted► The potential of mean force (PMF) of graphene nanosheets in supercritical CO2 was simulated. ► The effect of scCO2 density and temperature on the interactions of the graphenes has been clarified. ► The confined solvent arrangement within the interfacial region between the graphenes is responsible for the solvent-induced interaction.The colloidal dispersion stability of nano-sized graphene sheets in supercritical fluid (SCF) media is very important for developing SCF-based exfoliation and dispersion technologies for stabilization and solubilization of graphenes. We carried out molecular dynamics simulations to elucidate the stability mechanism of graphene in supercritical CO2 (scCO2). The potential of mean force (PMF) between two graphene nanosheets in scCO2 was simulated, and the effect of scCO2 density and temperature on the PMF behavior has been investigated. The simulation results demonstrate that there exists a free energy barrier between graphenes in the scCO2 fluid, possibly obstructing the aggregation of graphenes. The single-layer confined CO2 molecules between the graphene sheets can induce a dominating repulsion interaction between graphene sheets. At higher scCO2 fluid density, there are more confined CO2 molecules within the interplate regions, resulting in a stronger repulsive free energy barrier. The effect of temperature on the PMF is relatively minor. The scCO2 solvent structure shows layered confined arrangement in the interfacial region near the graphene nanosheets, which is correlated well with the PMF profile curve.

Keywords: Graphene nanosheets; Supercritical CO; 2; Potential of mean force (PMF); Colloidal dispersion; Molecular dynamics simulation

Controlled self-assembly of hydrophobic quantum dots through silanization by Ping Yang; Masanori Ando; Norio Murase (pp. 9-15).
Hydrophobic quantum dots were assembled into nanocomposites with well-defined solid or hollow spherical, ring-like, fiber-like, sheet-like, and pearl-like morphologies by QD silanization..Display Omitted► Hydrophobic QDs were assembled into nanocomposites by silanization. ► The silanization was carried out by using partially hydrolyzed silicon alkoxide. ► The nanocomposites with solid or hollow spherical, ring-like, fiber-like, sheet-like, and pearl-like morphologies. ► The nanocomposites retained high photoluminescence efficiency (maximum∼50%).We demonstrate the formation of one-, two-, and three-dimensional nanocomposites through the self-assembly of silanized CdSe/ZnS quantum dots (QDs) by using a controlled sol–gel process. The self-assembly behavior of the QDs was created when partially hydrolyzed silicon alkoxide monomers replaced hydrophobic ligands on the QDs. We examined systematically self-assembly conditions such as solvent components and QD sizes in order to elucidate the formation mechanism of various QD nanocomposites. The QD nanocomposites were assembled in water phase or on the interface of water and oil phase in emulsions. The partially hydrolyzed silicon alkoxides act as intermolecules to assemble the QDs. The QD nanocomposites with well-defined solid or hollow spherical, fiber-like, sheet-like, and pearl-like morphologies were prepared by adjusting the experimental conditions. The high photoluminescence efficiency of the prepared QD nanocomposites suggests partially hydrolyzed silicon alkoxides reduced the surface deterioration of QDs during self-assembly. These techniques are applicable to other hydrophobic QDs for fabricating complex QD nanocomposites.

Keywords: Quantum dots; Self-assembly; Silanization; Nanocomposite

Synthesis and characterization of pore size-tunable magnetic mesoporous silica nanoparticles by Jixi Zhang; Xu Li; Jessica M. Rosenholm; Hong-chen Gu (pp. 16-24).
Magnetic mesoporous silica nanoparticles with controlled pore sizes are prepared based on the cetyltrimethylammonium bromide (CTAB) stabilized magnetic seeds in the presence of pore swelling agents.Display Omitted► We perform the pore size tuning during the mesoporous silica growth on Fe3O4 seeds. ► The interactions of auxiliary organics with seeds and reagents regulate the efficiency. ► A joint incorporation of swelling agents maximizes pore size in a controlled fashion. ► The great potential of these nanoparticles as DNA carrier is demonstrated.Magnetic mesoporous silica nanoparticles (M-MSNs) are emerging as one of the most appealing candidates for theranostic carriers. Herein, a simple synthesis method of M-MSNs with a single Fe3O4 nanocrystal core and a mesoporous shell with radially aligned pores was elaborated using tetraethyl orthosilicate (TEOS) as silica source, cationic surfactant CTAB as template, and 1,3,5-triisopropylbenzene (TMB)/decane as pore swelling agents. Due to the special localization of TMB during the synthesis process, the pore size was increased with added TMB amount within a limited range, while further employment of TMB lead to severe particle coalescence and not well-developed pore structure. On the other hand, when a proper amount of decane was jointly incorporated with limited amounts of TMB, effective pore expansion of M-MSNs similar to that of analogous mesoporous silica nanoparticles was realized. The resultant M-MSN materials possessed smaller particle size (about 40–70nm in diameter), tunable pore sizes (3.8–6.1nm), high surface areas (700–1100m2/g), and large pore volumes (0.44–1.54cm3/g). We also demonstrate their high potential in conventional DNA loading. Maximum loading capacity of salmon sperm DNA (375mg/g) was obtained by the use of the M-MSN sample with the largest pore size of 6.1nm.

Keywords: Magnetic; Mesoporous silica nanoparticles; Seeded growth; Pore swelling; DNA adsorption

Mesoporous zirconosilicate doughnuts with high performance in liquid oxidative dehydrogenation of hydroquinone to quinone by Arnaud Lemaire; Bao-Lian Su (pp. 25-32).
Unusual partially crystalline ordered mesoporous zirconosilicate doughnuts with Si/Zr ratio as low as 1.5 with high catalytic activity, selectivity and stability in the liquid oxidative dehydrogenation of hydroquinone to 1,4-benzoquinone were synthesized from the aqueous polymerisation of a single source molecular precursor Zr[OSi(O t-BuO)3]4 without the use of any templating agent.Display Omitted► Template-free and low temperature synthesis. ► Ordered lamella mesoporous zirconosilicate doughnuts. ► Single-source molecular precursor Zr[OSi(O t-BuO)3]4. ► Oxidative dehydrogenation of hydroquinone to 1,4-benzoquinone.Unusual partially crystalline ordered mesoporous zirconosilicate doughnuts with Si/Zr ratio as low as 1.5 were synthesized from the aqueous polymerisation of a single source molecular precursor Zr[OSi(O t-BuO)3]4 without the use of any templating agent. A radial homogenous mesoporosity (4nm) was observed inside these very regular sub-micrometric (600nm) doughnuts. These structures were partially crystallized in hydrothermal conditions (100°C) into an analogous zircon (ZrSiO4) framework. The formation mechanism has been investigated. It is evidenced that chlorine anions Cl concentration and pH value are essential to achieve the process, even if their role is still a matter of investigations. The obtained materials demonstrated even higher catalytic activity, selectivity and stability in the liquid oxidative dehydrogenation of hydroquinone to 1,4-benzoquinone compared to TS-1 zeolite catalysts and amorphous highly ordered mesoporous zirconosilicate materials.

Keywords: Zirconosilicate; Mesoporous; Single molecular source; Partially crystalline; Doughnut shape morphology; Oxidative dehydrogenation

Synthesis, characterization and comparative evaluation of phenoxy ring containing long chain gemini imidazolium and pyridinium amphiphiles by Avinash Bhadani; Hardeep Kataria; Sukhprit Singh (pp. 33-41).
Phenoxy ring containing long chain gemini imidazolium amphiphite synthesized from renewable cardanol oil and its interaction with pDNA to form lipoplexes..Display Omitted► Eight gemini imidazolium and pyridinium amphiphiles have been synthesized. ► Phenoxy ring containing long chain gemini amphiphiles have lower cmc values compared to other cationic gemini surfactants. ► Gemini amphiphiles demonstrate high DNA binding affinity. ► Amphiphiles form stable lipoplex with DNA. ► Display low cytotoxicity on C6 Glioma cell.Two series of phenoxy ring containing long chain imidazolium and pyridinium based gemini amphiphiles have been synthesized from renewable cardanol oil having different spacers (i. e.S(CH2) nS, where n is 2, 3, 4 & 6). Critical micelle concentration (cmc) of these new gemini amphiphiles has been determined by conductivity method. Further, these new cationic amphiphiles have been evaluated for their DNA binding capability by agarose gel electrophoresis, ethidium bromide exclusion experiments and transmission electron microscopy (TEM). The cytotoxicity of these new amphiphiles have been evaluated by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Comparative studies of these phenoxy ring containing long chain gemini imidazolium amphiphiles and their pyridinium analogues depicted low cmc values of the later but greater DNA interaction capability and low cytotoxicity of the former series of amphiphiles.

Keywords: Gemini imidazolium amphiphile; Gemini pyridinium amphiphile; cmc; DNA interaction; Cytotoxicity

Effects of pharmaceutical excipients on cloud points of amphiphilic drugs by Andleeb Z. Naqvi; Malik Abdul Rub; Kabir-ud-Din (pp. 42-48).
Effect of addition of anionic hydrotropes on the cloud point of 50 mM AMT solution; ▴: NaSal, ●: NaBenz, ■: NaTos.Display Omitted► Effects of different pharmaceutical excipients on the clouding phenomenon of amphiphilic drugs are seen. ► As clouding concentrates the components in a small volume, it may increase the drug concentration which may be fatal for the body. ► Hence knowledge of clouding phenomenon of drugs in presence of carriers is important for preparing pharmaceutical formulations.The clouding behavior, i.e., formation of phase separation at elevated temperature (the temperature being known as cloud point (CP)), of three amphiphilic drugs, amitriptyline (AMT), clomipramine (CLP) and imipramine (IMP) hydrochlorides in the presence of various additives, like cationic surfactants (conventional and gemini), nonionic surfactants, bile salts, anionic hydrotropes, sodium salts of fatty acids and cyclodextrin has been investigated. These additives are generally used as drug delivery systems. The drugs used are tricyclic antidepressants. All the surfactants increase the CP of mixed micelles formed by cationic (conventional and gemini) and nonionic surfactants. Hydrotropes, bile salts and fatty acid salts, when added in low concentrations, increase the CP, whereas at high concentrations, they decrease it. β-Cyclodextrin behaves as simple sugar and decreases the CP of the drug solutions.

Keywords: Amphiphilic drugs; Cloud point; Surfactants; Hydrotropes; Fatty acids; β-Cyclodextrin

Controllable preparation of high-yield magnetic polymer latex by Chun-Chao Wu; Xiang-Ming Kong; Hai-Long Yang (pp. 49-58).
Four different miniemulsion polymerization procedures was designed and implemented. Magnetic template-dosage procedure is found to be the most effective for synthesizing high yield magnetic polymer latex.Display Omitted► A reproducible method, characterized by latex with high monomer conversion and high magnet content is introduced. ► Four different miniemulsion polymerization procedures was designed and implemented. ► The detail discussion on the preparation parameter is also given for accomplishing the systematic work.In order to overcome the low conversion and complex post-treatment, four different polymerization procedures were adopted to prepare the magnetic polymer latexes. The results clearly show that the strategy using magnetic emulsion template-dosage is the most effective and feasible. Based on the optimized procedure, various factors including the type of initiators such as oil soluble initiator, water soluble initiator, redox initiator system, crosslinking agent, functional monomers etc. were systematically studied. Magnetic polymer latex with high monomer conversion of 83% and high magnet content of 31.8% was successfully obtained. Besides, core–shell structured magnetic polymer latex with good film forming property was also prepared, which is promising for potential applications such as magnetic coatings and modification of cementitious materials with controlled polymer location.

Keywords: Miniemulsion polymerization; Magnetic polymers; Morphology; Polymerization procedure

The bis( p-sulfonatophenyl)phenylphosphine-assisted synthesis and phase transfer of ultrafine gold nanoclusters by Junyu Zhong; Jianglan Qu; Feng Ye; Caixia Wang; Lijing Meng; Jun Yang (pp. 59-63).
A bis( p-sulfonatophenyl)phenylphosphine-assisted approach for the synthesis and phase transfer of ultrafine gold nanoclusters was developed. Au nanoclusters obtained this way were dominated by {200} facets.Display Omitted► We develop a facile route to prepare ultrafine Au nanoclusters (NCs) at room temperature. ► The Au NCs thus prepared are dominated by the {200} facets. ► We use bis( p-sulfonatophenyl)phenylphosphine (BSPP) to stabilize the Au NCs and to facilitate the transfer of Au NCs from aqueous to an organic medium. ► The Au NCs after transfer can maintain their original size and morphology. ► The Au NCs transferred into toluene are used as seeds for the formation of core-shell Au@Ag2S nanocrystals.Gold nanoclusters (Au NCs) have attracted intensive attention for their molecular-like properties such as luminescence and unique charging behavior. A facile route has been developed for the preparation of ultrafine Au NCs at room temperature. Bis( p-sulfonatophenyl)phenylphosphine dihydrate dipotassium was used to stabilize the Au NCs obtained by NaBH4 reduction of HAuCl4 at pH of ∼12 and facilitated the phase transfer of Au NCs from aqueous phase to an organic medium based on electrostatic interaction. From the analyses of TEM, HRTEM, and XRD patterns, the formation of fcc structured Au NCs dominated by {200} facets was identified. The Au NCs transferred into toluene could be used as seeds for the formation of core–shell Au@Ag2S nanoparticles, providing for a promising strategy for the metal doping in semiconductor nanocrystals.

Keywords: Gold nanocluster; BSPP; Synthesis; Phase transfer; Core–shell

Selective adsorption of protein molecules on phase-separated sapphire surfaces by Kenji Yamazaki; Takayuki Ikeda; Toshinari Isono; Toshio Ogino (pp. 64-70).
Atomic force microscopy topographic image of a cross-stepped sapphire surface to which bovine serum albumin molecules are adsorbed.Display Omitted► We found a structural and chemical phase separation on sapphire surfaces. ► Protein molecules are site-selectively adsorbed to the phase-separated surfaces. ► The observed site-selective adsorption is attributed to electrostatic interactions.Site-selective adsorption of protein molecules was found on sapphire surfaces that exhibit a phase separation into two domains: weakly charged hydrophobic domain and negatively charged hydrophilic one. Ferritin and bovine serum albumin molecules, which are negatively charged in a buffer solution, are adsorbed to the hydrophobic domains. Avidin molecules, which are positively charged, are adsorbed to the other domain. Fibrinogen molecules, which consist of both negative and positive modules, are adsorbed to the whole sapphire surface. Hemoglobin molecules, whose net charge is almost zero, are also adsorbed to the whole surfaces. These results indicate that electrostatic double layer interaction is the primary origin of the observed selectivity. Dependence of protein adsorption or desorption behaviors on the pH value can also be interpreted by the proposed model.

Keywords: Protein adsorption; Biointerfaces; Sapphire; Atomic force microscopy

Photosensitive chitosan to control cell attachment by Nan Cheng; Xudong Cao (pp. 71-78).
4,5-Dimethoxy-2-nitrobenzyl chloroformate (NVOC)-modified chitosan surface (NVOC-CS) can control cell adhesion by two UV illuminations and the following immobilization of biomolecules, poly(ethylene glycol) and RGDS, respectively.Display Omitted► Photoliable molecule-modified chitosan was developed for selective cell attachment. ► Two illuminations and the following immobilizations help create surface heterogeneity. ► Cell attachment can be controlled by the heterogeneity of surface cues. ► Fibroblast cells enable to form cell pattern on the designed surface.An approach to control cell adhesion using a photocleavable molecule on chitosan has been developed and studied. Photocleavable 4,5-dimethoxy-2-nitrobenzyl chloroformate (NVOC) was introduced into chitosan to control the surface properties. The two UV illuminations with a photomask controlled the cleavage of NVOC and the presentation of deprotected amines on one chitosan surface spatially and temporally. The following immobilizations of cell repulsive poly(ethylene glycol) after the first illumination and cell adhesive sequence Arg–Gly–Asp–Ser (RGDS) after the second illumination on the surface helped create surface heterogeneity. Fourier transform infrared spectroscopy (FTIR), water contact angle, and UV–visible spectroscopy were used to characterize the surfaces and photoactivation during the process. To study the cell attachment and morphology on our designed surfaces, NIH/3T3 fibroblast cell was used. Cell number and morphology on the surfaces were investigated. The cell study demonstrated the feasibility of the surfaces on the control of cell adhesion and the formation of cell patterns by UV illuminations and the following immobilizations of different biomolecules.

Keywords: Chitosan; Poly(ethylene glycol); 2-Nitrobenzyl; Cell attachment

Impact of pulsed electric field on electrodialysis process performance and membrane fouling during consecutive demineralization of a model salt solution containing a high magnesium/calcium ratio by Nicolás Cifuentes-Araya; Gérald Pourcelly; Laurent Bazinet (pp. 79-89).
Mineral membrane fouling was diminished by applying pulsed electric fields during consecutive electrodialysis treatments of a high Mg/Ca ratio solution. The application of adequate pause lapse durations was demonstrated.Display Omitted► Pulsed electric field (PEF) modes of electrodialysis reduce membrane fouling. ► PEF ratio 1 enhances demineralization and lowers energy consumption. ► PEF ratio 0.3 enhances demineralization and highly diminishes mineral fouling. ► Excessively long pause lapses lead to diffusion phenomena and high power consumption. ► Dc current leads to severe membrane fouling by calcium and magnesium salts deposition.Pulsed electric fields (PEFs), hashed modes of current consisting in the application of a constant current density during a fixed time (Ton) followed by a pause lapse (Toff), were recently demonstrated as an effective alternative for mineral fouling mitigation and process intensification during electrodialysis (ED) treatments. Recent ED studies have continuously reported a considerable mineral fouling formation on ion-exchange membranes, especially during the demineralization of solutions containing a high Mg/Ca ratio and a basified concentrate solution. The aim of this study was to evaluate the process performance under two different PEF conditions on a mineral solution containing a mineral mixture giving a high Mg2+/Ca2+ ratio of 2/5. Two different pause-lapse durations (PEF ratio 1 (Ton/Toff 10s/10s); PEF ratio 0.3 (Ton/Toff 10s/33.3s)) during consecutive ED treatments and their comparison with dc current were evaluated at a current density of 40mA/cm2. Our results showed that PEFs resulted in an intensification of ED process, enhancing the demineralization rates (DRs), reducing the system resistance (SR), and reducing the fouling and energy consumption (EC). PEF ratio 1 was the most optimal condition among the current regimes applied, leading to faster and higher demineralization rates due to a lower fouling and with low energy consumption during all consecutive runs.

Keywords: Electrodialysis; Ion-exchange membrane; Calcium; Magnesium; Pulsed electric field; Pause duration; Mineral fouling; Process intensification

Amyloid-mediated synthesis of giant, fluorescent, gold single crystals and their hybrid sandwiched composites driven by liquid crystalline interactions by Sreenath Bolisetty; Jijo J. Vallooran; Jozef Adamcik; Stephan Handschin; Fabian Gramm; Raffaele Mezzenga (pp. 90-96).
The gold single crystals were produced by reducing an aqueous solution of chloroauric acid by β-lactoglobulin amyloid protein fibrils. Remarkably, these single crystalline gold crystals show auto fluorescence when illuminated to UV lamp and they self-assemble into hierarchical, layered protein-gold hybrid composites.Display Omitted► A novel method on the templating effect of β-lactoglobulin amyloid fibrils to synthesize giant gold single crystals. ► Green synthesis of the fluorescent gold microplates. ► Hybrid sandwiched gold single crystal composites. ► Nematic liquid crystals.We report for the first time on the templating effect of β-lactoglobulin amyloid-like fibrils to synthesize gold single crystals of several decades of μm in dimensions. The gold single crystals were produced by reducing an aqueous solution of chloroauric acid by β-lactoglobulin amyloid protein fibrils. Atomic force microscopy, conventional and scanning transmission electron microscopy, electron diffraction and optical microscopy techniques were combined to characterize the structure of the gold crystals. The single-crystalline features of these macroscopic gold crystals are witnessed by their distinctive hexagonal and triangular shape and are confirmed by selected area electron diffraction (SAED). UV–vis absorption spectrum, recorded after a reaction time of 6h at the heating temperature of 55°C showed a surface plasmon resonance peak at 540nm. With the increase of reaction time to 24h, the absorption spectrum peaks shift to a very broad and higher wavelength region extending up to near infrared region. Remarkably, these single crystalline gold crystals show auto fluorescence when illuminated to UV lamp. Further increase in β-lactoglobulin amyloid fibrils concentration above the isotropic-nematic transition, drives the formation of gold single crystals microplates stacking together and self-assembling into new hierarchical, layered protein-gold hybrid composites.

Keywords: Amyloid fibrils; Single crystals; Gold nanoparticles; Salt reduction; Green chemistry; Fluorescence; β; -Lactoglobulin; Liquid crystals

Supramolecular assembled nanogel made of mannan by Sílvia A. Ferreira; Paula Pereira; Paula Sampaio; Paulo J.G. Coutinho; Francisco M. Gama (pp. 97-108).
New supramolecular assembled amphiphilic mannan-C16 nanogel was designed and characterized in terms of structure, size, shape, surface charge, stability, ability to entrap molecules and cytotoxicity in vitro.Display Omitted► Nanogel synthesis: Michael addition of hexadecanethiol to vinyl methacrylated mannan. ► Nanogel was designed with a versatile, easy, reproducible and low-cost method. ► Nanogel is near neutral, polydisperse with 50–140nm mean hydrodynamic diameter. ► Nanogel size is stable over storage and at pH 3–8, salt or urea solutions. ► Nanogel is non-toxic to mouse fibroblast 3T3 but toxic to mouse macrophage-like J774.The supramolecular assembly of amphiphilic mannan, synthesized by the Michael addition of hydrophobic 1-hexadecanethiol to vinyl methacrylated mannan, originates in aqueous medium the formation of a nanogel, stabilized by hydrophobic interactions among alkyl chains. The critical aggregation concentration, calculated by fluorescence spectroscopy ranged between 0.002 and 0.01mg/mL, depending on the polymer degree of substitution. The cryo-field emission scanning electron microscopy showed spherical macromolecular micelles with diameters between 100 and 500nm. The dynamic light scattering analysis revealed a polydisperse colloidal system, with mean hydrodynamic diameter between 50 and 140nm, depending on the polymer degree of substitution. The nanogel is negatively charged, stable over a 6months storage period, and stable at pH 3–8, salt or urea solutions. Bovine serum albumin and curcumin were spontaneously incorporated in the nanogel, being stabilized by the hydrophobic domains, opening the possibility for future applications as potential delivery systems for therapeutic molecules. In vitro assays were carried out to characterize the biocompatibility of the nanogel. A toxic effect of mannan-C16 was observed, specific to mouse macrophage-like cell line J774, not affecting mouse embryo fibroblast cell line 3T3 viability.

Keywords: Mannan; Nanogel; Supramolecular assembly; Michael addition; Biocompatibility

Variable on-demand release function of magnetoresponsive hybrid capsules by Kiyofumi Katagiri; Yuji Imai; Kunihito Koumoto (pp. 109-114).
Magnetoresponsive hybrid capsules were prepared via the colloid-templating technique. The release rate of the hybrid capsules was variable through controlling the deposition amount of Fe3O4 nanoparticles on the capsules.Display Omitted► Magnetoresponsive hybrid capsules were successfully prepared by collloid templating technique. ► The hybrid capsules consisted of polyelectrolytes, amphiphile bilayers and Fe3O4 nanoparticles (NPs). ► The deposition amount of Fe3O4 NPs is variable by changing the concentration of Fe3O4 NP dispersion. ► Encapsulated maerials were released on-demand by irradiation with an alternating magnetic field. ► The release rate of the capsules was variable by controlling the deposition amount of Fe3O4 NPs.Magnetoresponsive hybrid capsules formed with polyelectrolytes, amphiphile bilayers and Fe3O4 nanoparticles were fabricated by a colloid-templating technique. Melamine–formaldehyde (MF) core particles with polyelectrolyte multilayer shell were prepared by layer-by-layer assembly. Fe3O4 nanoparticles were additionally deposited on the capsular surface. Hollow capsules were obtained by the removal of the MF core particles. Amphiphile bilayer was finally coated on the obtained hollow capsules. The deposition amount of the Fe3O4 nanoparticles is variable by changing the concentration of Fe3O4 dispersion using for preparation of capsules. Encapsulated dyes were released on-demand by irradiation with an alternating magnetic field, due to a phase transition in the amphiphile membrane, induced by heating of the magnetic nanoparticles. The release rate of the hybrid capsules was controllable through controlling the deposition amount of Fe3O4 nanoparticles on the capsules.

Keywords: Drug delivery; Hollow capsules; On-demand release; Layer-by-layer assembly; Magnetic nanoparticles

Characterization of cephalexin loaded nonionic microemulsions by Monzer Fanun; Vassiliki Papadimitriou; Aristotelis Xenakis (pp. 115-121).
Biocompatible fully dilutable microemulsions based on water/propylene glycol/sucrose laurate/ethoxylated mono-di-glyceride/isopropylmyristate/peppermint oil, were prepared and structurally characterized to be used as potential transdermal carriers of cephalexin.Display Omitted► U-type newly formulated biocompatible microemulsions enhance the solubilization of cephalexin. ► Electrical conductivity, dynamic light scattering, ultrasonic velocity and EPR spectroscopy methods were applied. ► Cephalexin solubilization capacity is microstructure dependent and remains solubilized at the interface upon dilution. ► These formulations can be progressively and fully diluted by aqueous phase.Water/propylene glycol/sucrose laurate/ethoxylated mono-di-glyceride/isopropyl myristate/peppermint oil U-type microemulsions were used to solubilize cephalexin. Microemulsion dilution and interfacial factors contributing to the cephalexin solubilization were evaluated. Cephalexin solubilization capacity increases with the increase in the aqueous phase volume fraction ( φ) up to 0.4 then decreases. Electrical conductivity of drug loaded and drug free microemulsions increases with φ. The hydrodynamic radius measured by dynamic light scattering of the oil-in-water loaded microemulsions decreases with temperature. The microemulsions were characterized by the volumetric parameters, density, excess volume, ultrasonic velocity and isentropic compressibility. The microemulsion densities increase with φ up to 0.8 then decrease. The excess volume decreases with φ up to 0.8 then stabilizes. Ultrasonic velocities increase with the increase in φ while isentropic compressibility decreases. Analysis of the volumetric parameters enabled the characterization of structural transition along the microemulsion phase region. The presence of water-in-oil, bicontinuous and oil-in-water microemulsions, at aqueous phase volume fractions below 0.2, between 0.3 and 0.7 and above 0.8, respectively were found. Interfacial properties and dynamic structure of the monolayer for drug loaded and drug free microemulsions, were studied by electron paramagnetic resonance spectroscopy employing the nitroxide spin probe 5-doxylstearic acid. The rigidity of the interface was affected by the water content and also the presence of cephalexin.

Keywords: Solubilization capacity; Dilution factor; Interfacial factor; Hydrodynamic radius; Structural transitions; Electron paramagnetic resonance spectroscopy

Tunable disintegration of layer-by-layer assembly multilayer films based on hydrolytical-polybetaine at wide-range time by Zhangliang Gui; Jinwen Qian; Yuan He; Quanfu An; Xuesan Wang; Chengpeng Tian; Wendan Sun (pp. 122-128).
Controllable disintegration of hydrolytical-polybetaine multilayer films and tunable release of polyelectrolyte at wide-range time.Display Omitted► A cationic hydrolytical-polycarboxybetaine (HPCB) was firstly synthesized. ► HPCB could assemble with poly (sodium 4-styrenesulfonate) PSS to form multilayer films. ► A very wide-range disintegration time (from 2 min to 30 days) of HPCB/PSS multilayer films was successfully realized.A cationic hydrolytical-polycarboxybetaine (HPCB), poly(N-ethyl acetate-4-vinylpyridinium bromide) was synthesized by incorporating ester group into the side chain of polycarboxybetaine (PCB). The hydrolytic behaviors of HPCB samples in pH 7.4 phosphate buffer saline (PBS) were investigated by FT-IR and1H NMR. The layer-by-layer (LbL) assembly of HPCB/poly (sodium 4-styrenesulfonate) PSS and the disintegration of HPCB/PSS multilayer films were monitored by UV–vis absorption spectroscopy, quartz crystal microbalance (QCM) and atomic force microscopy (AFM). The disintegrated behavior of multilayer films was studied in detail by changing the cationic degree of HPCB and the pH of the immersion solution (PBS) in the disintegration process. The disintegration time of HPCB/PSS multilayer films could be controlled widely from 2min to 30days in PBS.

Keywords: Hydrolytical-polybetaine; Layer-by-layer assembly; Tunable disintegration; Wide-range time

Morphological and chemical features of nano and macroscale carbons affecting hydrogen peroxide decomposition in aqueous media by Kateryna V. Voitko; Raymond L.D. Whitby; Vladimir M. Gun’ko; Olga M. Bakalinska; Mykola T. Kartel; Krisztina Laszlo; Andrew B. Cundy; Sergey V. Mikhalovsky (pp. 129-136).
The decomposition of hydrogen peroxide at a surface of a variety of nano and microforms of carbons depends differently on presence of O- and N-containing surface functionalities.Display Omitted► Detailed study of the decomposition of hydrogen peroxide on nano and microforms of carbons. ► Doping of nano or microforms of carbons increases the reaction rate, but only for a limited number of reaction cycles. ► SLGO and pure CNT exhibit greater stability in their performance over subsequent cycles compared with other carbons. ► Incremental function distribution analysis of the reaction rate offers deep insight to material performance.Chemical and structural factors of carbon materials affect their activity in adsorption and surface reactions in aqueous media. Decomposition of hydrogen peroxide studied is a probe reaction for exploring parameters of carbons that might be involved, such as specific surface area, nitrogen and oxygen doping and conformational changes. To date, a detailed comparison of the behavior of carbon nanoscale (Carbon Nanotubes, CNT, Single Layer Graphene Oxide, SLGO) with macroscale (Activated carbons, AC) materials in this reaction has not been forthcoming. Herein, we demonstrate that on their first cycle, ACs in doped and undoped forms outperform all nanoscale carbons tested in the H2O2 decomposition. Among the nanocarbons, nitrogen-doped CNT exhibited the highest activity in this reaction. However, subsequent recycling of each carbon, without chemical regeneration between uses, reveals SLGO exhibits greater reaction rate stability over an extended number of cycles ( n>8) than other carbons including nitrogen-doped CNT and ACs. The effects of pH, temperature and concentration on the reaction were analyzed. Quantum-chemical modeling and reaction kinetics analysis reveal key processes likely involved in hydrogen peroxide decomposition and show evidence that the reaction rate is linked to active sites with N-and O-containing functionalities.

Keywords: Single Layer Graphene Oxide; Carbon nanotubes; Activated carbons; H; 2; O; 2; decomposition; Reaction rate constant distributions; Quantum-chemical modeling

When dissolved is not truly dissolved—The importance of colloids in studies of metal sorption on organic matter by Johan Schijf; Alison M. Zoll (pp. 137-147).
In sorption studies involving biomaterials, the release of organic colloids may preclude proper separation of the ‘dissolved’ and ‘particulate’ metal fractions with conventional filtration techniques.Display Omitted► Biosorbents may release organic colloids that interact strongly with trace metals. ► Ignoring colloid-bound metals may bias distribution coefficient calculations. ► Distribution coefficients can be corrected with a multi-site Langmuir isotherm. ► Ultra-filtration should become routine practice in all metal biosorption studies. ► Colloid release may cause premature break-through of packed-bed biosorbent columns.In controlled metal sorption experiments, the equilibrium distribution coefficient is a key variable quantifying sorbate partitioning across the solid–solution interface. Separation of metals into ‘dissolved’ and ‘particulate’ fractions is commonly achieved with syringe filtration, where the boundary is somewhat arbitrarily dictated by the limited selection of available pore sizes. Investigations involving natural organic matter, such as bacterial cells or plant tissues, are especially prone to experimental artifacts if the substrate releases abundant colloidal compounds that contribute to sorption by binding free metal cations in a pH-dependent fashion yet pass through conventional filters, causing the truly dissolved fraction to be grossly overestimated.We observed this phenomenon during a study of lanthanide sorption on a marine macroalga, Ulva lactuca, as a function of pH. At low ionic strength, distribution coefficients calculated for a 0.22-μm size cutoff falsely imply that metal sorption reverses to gradual release above pH 4.6, instead of continuing to increase. Centrifuging the filtrates in Amicon® Ultra units (30 and 3kDa molecular weight cutoff) revealed a mounting proportion of colloid-bound metal, constituting up to 95% of the ‘dissolved’ (<0.22μm) fraction near pH 8. Measurements of DOC concentrations suggest this being due to pH-dependent binding of free metal cations to a fixed pool of organic colloids. The process is well described with a simple 2-site Langmuir isotherm in 0.05, 0.5, and 5.0M NaCl. Using this model to correct the original distribution coefficients not only removed the spurious reversal at low ionic strength, but also uncovered a prominent suppressive effect on the intermediate and high ionic strength data that had initially gone undetected. Ultra-filtration may thus be an essential analytical tool for proper characterization and interpretation of metal sorption on organic matter over a wide range of experimental conditions. Some implications are discussed for the use of biosorbents in the remediation of metal-contaminated waste waters.

Keywords: Macroalgae; Sorption; Colloids; Ultra-filtration; Lanthanides; Remediation

Head group effects on molecular packing in lamellar liquid crystals by Chika Ishizuka; Satoshi Arima; Kenji Aramaki (pp. 148-153).
By employing compact head-type surfactants, tighter molecular packing is obtained.Display Omitted► Surfactants having both linear POE chain and sucrose were employed. ► The mean and partial molecular areas in lamellar liquid crystal were evaluated. ► Looser molecular packing for more tails with POE and sucrose head groups.In this study, molecular packing in lamellar liquid crystals in poly(oxyethylene) dodecyl ether(C12EO n) pure systems and the two surfactant mixtures of C12EO8/1-dodecanol(C12EO0), C12EO8/lipophilic sucrose laurate (L-595), hydrophilic sucrose laurate (L-1695)/C12EO2 is investigated in terms of mean molecular area and partial molecular area (PMA). Lamellar liquid crystals formed in the C12EO8/C12EO0 mixed system show higher melting temperatures than those in the C12EO n pure systems, even though the average number of EO units in the mixed surfactant system is the same as in the pure system. We compared the mean molecular area at the interface between hydrophilic and lipophilic moieties in the lamellar liquid crystals in each system. In the mixed system, the molecules are packed more tightly than in the pure system. Among the C12EO n and sucrose laurate mixtures, the L-1695/C12EO2 mixed system showed a smaller mean molecular area per lipophilic chain than the C12EO8/L-595 mixed system. We investigated the effect of mixing two surfactants with different head group geometry on molecular packing by comparing the PMA of each surfactant.

Keywords: Lamellar liquid crystal; Sucrose laurate; Poly(oxyethylene) dodecyl ether; Molecular packing; Molecular area; Partial molecular area

Micellisation of triblock copolymers of ethylene oxide and 1,2-butylene oxide: Effect of B-block length by Adriana Cambón; Manuel Alatorre-Meda; Josué Juárez; Antonio Topete; Dharmista Mistry; David Attwood; Silvia Barbosa; Pablo Taboada; Víctor Mosquera (pp. 154-158).
Change in the dependence the critical micelle concentration of poly(butylene oxide)-poly(ethylene oxide) block copolymer with hydrophobic block length denoting variation in the micelle equilibrium.Display Omitted► Triblock oxybutylene/oxyethylene copolymers (BEB) with long B-blocks have been synthesized. ► Micellisation in aqueous solution have been compared with that of diblock analogues. ► Effects seen on increasing B-block length are assigned to unimolecular micellisation.We have used pyrene fluorescence spectroscopy and isothermal titration calorimetry (ITC) to investigate the effect of hydrophobic-block length on values of the critical micelle concentration (cmc) for aqueous solutions of triblock poly(butylene oxide)–poly(ethylene oxide)–poly(butylene oxide) block copolymers (B nE mB n, where m and n denote the respective block lengths) with hydrophobic block lengths in the range n=12–21. Combined with results from previous work on B nE mB n copolymers with shorter B blocks, plots of log10(cmc) (cmc in molar units and reduced to a common E-block length) against total number of B units (n t= n for diblock orn t=2 n for triblock copolymers) display transitions in the slopes of the two plots, which indicate changes in the micellisation equilibrium. These occur at values ofn twhich can be assigned to the onset and completion of collapse of the hydrophobic B blocks, an effect not previously observed for reverse triblock copolymers. The results are compared with related data for diblock E mB n copolymers.

Keywords: Block copolymer; Critical micelle concentration; Isothermal titration calorimetry

Electrolyte effect on adsorption and the phase transition from microstructures to nanostructures in ionic/ionic surfactants mixture by Maryam Moallemi; Beheshteh Sohrabi; Sara Fazeli (pp. 159-169).
Variations of electrostatic, transform and steric free energies vs the concentration of salt in cationic-rich region.Display Omitted► Energies are calculated by utilizing the new model of our previous work in various concentrations of salt. ► The obtained results show that transfer free energy decreased with increase of salt concentration. ► The variations of electrostatic, transfer and steric free energies were determined by using cyclic voltammetry data. ► The phase transition between mixed micelle and vesicle in presence of electrolyte was investigated by modified capacitor model.The effect of salt concentration on intermicellar interactions and aggregate structures of anionic and cationic-rich mixtures of CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecyl sulfate) were investigated with conductometry, surface tension, zeta potential, cyclic voltammetry measurements and by determining the surfactant NMR self-diffusion coefficients. The critical aggregate concentration (CAC), surface excess ( Γmax), and mean molecular surface area ( Amin) were determined from plots of the surface tension ( γ) as a function of the log of total surfactant concentration. The electrochemical behavior of cationic–anionic (catanionic) mixed surfactant and self-assembled surfactant monomers at Pt wire electrode were studied by cyclic voltammetry (CV). A variation in the peak current versus the total concentration of surfactant allow us to evaluate the CAC and related parameters from regular solution theory along with the diffusion coefficient of the electroactive species. It was observed that, for both the planar air/aqueous interface and micellar systems, the nonideality decreased as the amount of electrolyte in the aqueous medium was increased. Finally, we investigated the variations of electrostatic, transfer and steric free energy in phase transition between mixed micelle and vesicle in the presence of electrolyte using the presented model by our groups.

Keywords: Catanionic surfactant mixtures; Anionic-rich; Cationic-rich; Stern layer; Mixed monolayers

Shear-induced coalescence of oil-in-water Pickering emulsions by Catherine P. Whitby; Franziska E. Fischer; Daniel Fornasiero; John Ralston (pp. 170-177).
The extent of coalescence in silica particle-stabilized emulsions under shear depends on the salt concentration.Display Omitted► Shear flow can cause coalescence in oil-in-water Pickering emulsions which are stable when at rest. ► Susceptibility to orthokinetic coalescence is linked to salt concentration. ► Shearing breaks down drop-particle network and weakly aggregated particles are easily displaced as drops collide together.This work reports on coalescence in oil-in-water Pickering emulsions subjected to simple shear flow. The emulsions were stabilized by silanized fumed silica particles forming layers a few hundred nanometers thick around drops that are tens of micrometers in size. The drop size and particle concentration in the emulsions were fixed, while the salt concentration was varied to adjust the colloidal interactions between the drops and particles. At rest the oil drops do not coalesce. The susceptibility of the drops to orthokinetic coalescence was found to depend on the extent of particle flocculation in the attached particle layer. The evolution of the drop size with time and shear rate was consistent with phenomenological models used to describe the behavior of emulsions under shear.

Keywords: Orthokinetic; Aggregation; Particle-stabilized emulsion; Shear stress

Characterization of mixed non-ionic surfactants n-octyl-β-d-thioglucoside and octaethylene–glycol monododecyl ether: Micellization and microstructure by C. Carnero Ruiz; J.A. Molina-Bolívar (pp. 178-185).
Dehydration produced by an increase of temperature induces micellar growth, but this is inhibited by the participation of the sugar surfactant in the mixed micelles.Display Omitted► A study of the micellar properties in a mixed non-ionic surfactant system. ► Effect of composition, temperature, and concentration on the size of micelles. ► Changes in the micellar microstructure with composition.Mixed micelles of n-octyl-β-d-thioglucoside (OTG) and octaethylene–glycol monododecyl ether (C12E8), two non-ionic surfactants belonging to the alkyl glucosides and polyoxyethylene alkyl ether families, respectively, were investigated by using light scattering and fluorescence probe techniques. From the determination of the critical micelle concentration (cmc), by the well-established pyrene 1:3 ratio method, it was found that the mixed system behaves ideally, the micellization process being clearly controlled by the ethoxylated surfactant. The micellar hydrodynamic radius as a function of temperature, composition and concentration was obtained by dynamic light scattering measurements. It was observed that the micellar size increases with temperature, this growth being more pronounced as the relative proportion of the ethoxylated surfactant was increased. The behavior of the micellar size with the total surfactant concentration was also found to be dependent on temperature and composition. The clouding temperature, characteristic of the ethoxylated surfactants, was increased with the addition of the sugar surfactant. Lastly, possible structural changes in the micellar palisade layer were examined by steady-state fluorescence anisotropy in conjunction with time-resolved fluorescence studies with the hydrophobic probe coumarin 6 (C6). The obtained results indicate that the participation of the ethoxylated surfactant induces a slightly more polar palisade layer, whereas the probe carries out a faster rotational reorientation as a result of a less compact environment. All these observations were attributed to the different structure of the head groups of both surfactants and, as a consequence, to their different hydration.

Keywords: OTG; C; 12; E; 8; Mixed micelles; Light scattering; Fluorescence

Surface active ionic liquids: Study of the micellar properties of 1-(1-alkyl)-3-methylimidazolium chlorides and comparison with structurally related surfactants by Paula D. Galgano; Omar A. El Seoud (pp. 186-194).
Surface-active ionic liquids, SAILs; Effects of structure modification on the micellar properties of SAILs; Thermodynamic parameters of micellization.Display Omitted► Properties of 1-R-3-methylimidazolim chlorides, R=decyl to tetradecyl investigated. ► Effects of chain length and T on thermodynamics of micellar surfactant ionic liquids. ► Novel, expedient procedure to calculate micellar aggregation numbers at different T. ► Comparison of SAILs with conventional cationic surfactants. ► Influence of H2 of the imidazolium group.The impetus for the increasing interest in studying surface active ionic liquids (SAILs; ionic liquids with long-chain “tails”) is the enormous potential for their applications, e.g., in nanotechnology and biomedicine. The progress in these fields rests on understanding the relationship between surfactant structure and solution properties, hence applications. This need has prompted us to extend our previous study on 1-(1-hexadecyl)-3-methylimidazolium chloride to 1-(1-alkyl)-3-methylimidazolium chlorides, with alkyl chains containing 10, 12, and 14 carbons. In addition to investigating relevant micellar properties, we have compared the solution properties of the imidazolium-based surfactants with: 1-(1-alkyl)pyridinium chlorides, and benzyl (2-acylaminoethyl)dimethylammonium chlorides. The former series carries a heterocyclic ring head-group, but does not possess a hydrogen that is as acidic as H2 of the imidazolium ring. The latter series carries an aromatic ring, a quaternary nitrogen and (a hydrogen-bond forming) amide group. The properties of the imidazolium and pyridinium surfactants were determined in the temperature range from 15 to 75°C. The techniques employed were conductivity, isothermal titration calorimetry, and static light scattering. The results showed the important effects of the interactions in the interfacial region on the micellar properties over the temperature range studied.

Keywords: Surface active ionic liquids; 1-Alkyl-3-methylimidazolium chlorides; 1-Alkylpyridinium chlorides; Conductivity of micellar solutions; Isothermal titration calorimetry; Thermodynamic properties of micelle formation; Effect of temperature on micelle formation

Isolation and partial characterization of a biosurfactant mixture produced by Sphingobacterium sp. isolated from soil by C. Burgos-Díaz; R. Pons; M.J. Espuny; F.J. Aranda; J.A. Teruel; A. Manresa; A. Ortiz; A.M. Marqués (pp. 195-204).
Sphingobacterium sp. reduces surface tension due to the production of a biosurfactant mixture. Phospholipids, lipopeptides and glycolipids have been identified, apparently showing two distinct cmcs.Display Omitted► Crude extract of Sphingobacterium sp. 6.2S reduces surface tension to 22mN/m. ► There are no previous reports on BS production from Sphingobacterium. ► Fraction A reduces surface tension to 33mN/m and has a cmc of 0.18g/L. ► Fraction B reduces surface tension (23mN/m) and shows a triple break in cmc curves. ► Strain 6.2S produces a BS mixture of phospholipids, lipopeptides and a glycolipid.Strain 6.2S, isolated from soil and identified as a Sphingobacterium sp., is the first strain in this genus to be reported as a biosurfactant producer, being able to reduce the surface tension of its culture supernatant to 32mN/m. In this work, biosurfactants from the culture supernatant were purified and partially characterized. The crude extract (10g/L) was very effective in reducing surface tension (22mN/m). Thin layer chromatography (TLC) indicated that a mixture of various biosurfactants was present in the 6.2S crude extract. After purification, Fraction A, a phospholipid mixture, reduced surface tension to 33mN/m. Fraction B was a mixture of lipopetides and at least one glycolipid. The surface tension–concentration curve showed two plateaux, the first of which can be attributed to a critical aggregation concentration of the biosurfactant with a protein (2.7g/L) and the second to the true cmc in water (6.3g/L).

Keywords: Biosurfactant; Sphingobacterium; sp.; Surface tension; Interfacial tension; cmc; Phosphatidyletanolamine

Effect of alkyl chain length, head group and nature of the surfactant on the hydrolysis of 1,3-benzoxazine-2,4-dione and its derivatives by Abdullah S. Al-Ayed; Mohd. Sajid Ali; Hamad A. Al-Lohedan; Adel M. Al-Sulaim; Zuheir A. Issa (pp. 205-211).
The rate of alkaline hydrolysis of 1,3-benzoxazine-2,4-dione and its derivatives show maxima as the concentration of cationic surfactant, CTAB, increases. The anionic surfactant, SDS, inhibits the rate of alkaline hydrolysis.Display Omitted► N-substitution in 1,3-benzoxazine-2,4-dione accelerates the rate of alkaline hydrolysis. ► Surfactants with greater hydrophobicity have more influence on the rate of hydrolysis. ► The hydrolysis can also be inhibited by the addition of salts.The alkaline hydrolysis of carsalam (2H-1,3-benzoxazine-2,4(3H)-dione), denoted as I, and its N-substituted derivatives i.e., N-methyl-1,3-benzoxazine-2,4-dione (II) and N-benzoyl-1,3-benzoxazine-2,4-dione (III) was studied spectrophotometrically at physiological temperature. The rate of hydrolysis was found to be independent on the substrate concentration. In case of I, the reaction was fractional order with respect to [OH] while for II and III, reaction obeyed the first order kinetics. Effect of cationic surfactants with varying hydrophobic chains (cetyltrimethylammonium bromide, CTAB, tetradecyltrimethylammonium bromide, TTAB and dodecyltrimethylammonium bromide, DTAB) and with different head-group (cetyl pyridinium chloride, CPC) and anionic surfactant (sodium dodecyl sulfate, SDS) was also seen on the rate of alkaline hydrolysis of the carsalam and its derivatives. Cationic surfactants first catalyzed the rate of hydrolysis at lower concentrations followed by the inhibition at higher concentrations. The length of the alkyl chain had remarkable effect on the catalytic efficiency of the surfactants. Similarly N-substitution on substrate also increased the catalysis by micelles. The anionic surfactant SDS inhibited the rate of hydrolysis at all of the concentrations studied. The catalysis by cationic micelles followed by inhibition was treated in terms of the pseudophase ion-exchange model, while for the inhibition by SDS micelles the Menger–Portnoy model was used to fit the data. The effect of salts (NaCl, NaBr and (CH3)4NBr) was also seen on the hydrolysis of II and it was found that all salts inhibited the rate of reaction. The inhibition follows the trend NaCl3)4NBr.

Keywords: 1,3-Benzoxazine-2,4-dione; Cationic surfactants; Anionic surfactants; Alkaline hydrolysis; Micellar catalysis

Novel ultrasonic–modified MnO x/TiO2 for low-temperature selective catalytic reduction (SCR) of NO with ammonia by Yaping Zhang; Xiaoyuan Zhao; Haitao Xu; Kai Shen; Changcheng Zhou; Baosheng Jin; Keqin Sun (pp. 212-218).
The ultrasonic process significantly improved the dispersion behavior and surface acid property of manganese oxide on TiO2 as well as the catalytic activity, especially at temperature below 120°C. The NO conversion could reach 90% at 100°C.Display Omitted► The ultrasonic-modified process introduced ultrasound in the solution impregnation for MnOx/TiO2 catalyst preparation. Ultrasonic process significantly improved the catalytic activity. The NO conversion could reach 90% at 100°C. The combination analysis of XRD and HRTEM confirmed that manganese oxide was in a highly dispersed state and Ti and Mn had strong interaction. In situ FT-IR studies revealed there were significant amounts of Lewis acidity and high Mn atom concentration on the surface of the novel catalysts.A novel ultrasonic–modified MnO x/TiO2 catalyst was prepared and compared with two different kinds of MnO x/TiO2 catalysts in the process of low-temperature selective catalytic reduction of NO with NH3. The physicochemical properties of the catalysts were studied by using various characterization techniques, such as Brunauer–Emmett–Teller (BET) surface measurement, X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and in situ Fourier transform infrared spectroscopy (in situ FT-IR). The ultrasonic–modified process introduced ultrasound in the solution impregnation step of traditional impregnation method for MnO x/TiO2 catalyst preparation. In this study, ultrasonic process significantly improved the dispersion behavior and surface acid property of manganese oxide on TiO2 as well as the catalytic activity, especially at temperature below 120°C. The NO conversion could reach 90% at 100°C. For the novel ultrasonic–modified catalyst, the combination analysis of XRD and HRTEM confirmed that manganese oxide was in a highly dispersed state and Ti and Mn had strong interaction. Furthermore, in situ FT-IR studies revealed that there were significant amounts of Lewis acidity and high Mn atom concentration on the surface of the novel catalysts.

Keywords: Selective catalytic reduction; Low-temperature; MnO; x; /TiO; 2; catalysts; Ultrasonic impregnation; NO reduction

Anion exchange membranes based on semi-interpenetrating polymer network of quaternized chitosan and polystyrene by Jilin Wang; Ronghuan He; Quantong Che (pp. 219-225).
The semi-interpenetrating polymer network provides the membranes, based on the cross-linked quaternized chitosan and polystyrene, a higher tolerance to alkaline solutions.Display Omitted► Preparation of anion exchange membranes with semi-interpenetrating polymer network. ► The semi-IPN membranes of QCS and PS entail high tolerance to alkaline medium. ► Less swelling of the semi-IPN membrane due to the presence of hydrophobic PS. ► Improved stress of the semi-IPN membrane as a result of the semi-IPN.Anion exchange membranes with semi-interpenetrating polymer network (semi-IPN) were prepared based on quaternized chitosan (QCS) and polystyrene (PS). The PS was synthesized by polymerization of styrene monomers in the emulsion of the QCS in an acetic acid aqueous solution under nitrogen atmosphere at elevated temperatures. The semi-IPN system was formed by post-cross-linking of the QCS. A hydroxyl ionic conductivity of 2.80×10−2Scm−1 at 80°C and a tensile stress at break of 20.0MPa at room temperature were reached, respectively, by the semi-IPN membrane containing 21wt.% of the PS. The durability of the semi-IPN membrane in alkaline solutions was tested by monitoring the variation of the conductivity and the mechanical strength. The degradation of the conductivity at 80°C was about 5% by immersing the membrane in a 1molL−1 KOH solution at room temperature for 72h and at 60°C for 50h, respectively. The tensile stress at break at room temperature could maintain about 20.0MPa for the membrane soaking in a 10molL−1 KOH solution at ambient temperature for more than 70h. The water swelling of the semi-IPN membranes was discussed based on the stress relaxation model of polymer chains, and it obeyed the Schott’s second-order swelling kinetics.

Keywords: Anion exchange membrane; Semi-interpenetrating polymer network; Quaternized chitosan; Polystyrene; Conductivity; Strength; Emulsion

The influence of acid demineralization on surface characteristics of black carbon and its sorption for pentachlorophenol by Liping Lou; Ling Luo; Lina Wang; Guanghuan Cheng; Xinhua Xu; Jiaai Hou; Bei Xun; Baolan Hu; Yingxu Chen (pp. 226-231).
SEM photographs and PCP sorption isotherms of rice straw BC with different acid demineralization process.Display Omitted► The acid demineralization has different effect on various BC of different origins. ► It changed rice straw BC’s surface characteristics and increased its PCP sorption. ► But it has little influence on the fly ash BC and soot BC. ► It was caused by the change of surface area, pore volume, and acidic functional group.Acid treatment is a routine demineralization process to obtain black carbon (BC), but there has been little systematic research about its influence on BC’s characteristics. In this study, elemental analysis, SEM, FTIR, and Boehm titration were used to investigate that effect. Our results showed that the acid treatment had little influence on the sorption of fly ash and soot to pentachlorophenol (PCP), but it greatly increased the sorption of rice chars to PCP. There were two competing effects of acid demineralization on the adsorption capacity of BC. On one hand, it increased the amount of the acidic functional groups, which decreased the adsorption capacity. On the other hand, it increased the surface and pore volume of BC and caused the emergence of hidden carbon enclosed by minerals, which in turn increased the sorptivity significantly. Especially for rice chars (600°C), after acid treatment, their surface area increased from 3.52 to 235m2g−1 and the sorption capacity coefficient increased from 2.12 to 4.10.

Keywords: Black carbon (BC); Pentachlorophenol (PCP); Acid dimineralization; Adsorption

Efficient removal of boron acid by N-methyl-d-glucamine functionalized silica–polyallylamine composites and its adsorption mechanism by Xin Li; Ru Liu; Shan Wu; Jiong Liu; Shushan Cai; Dongsheng Chen (pp. 232-237).
Novel boron adsorbent was fabricated by grafting a boric acid chelating group, i.e., N-methyl-d-glucamine, onto silica–polyallylamine composites.Display Omitted► Boron-specific adsorbent was prepared. ► Boron adsorbent maintained its integrity and high efficiency of boron removal after multiple adsorption–regeneration cycles. ► Boron adsorption is attributed to specific affinity between the N-methyl-d-glucamine and H3BO3, and physical adsorption.A novel boron adsorbent was fabricated by grafting a boric acid chelating group, i.e., N-methyl-d-glucamine, onto the hydrophilic silica–polyallylamine composites (SPC). The boron adsorbent was characterized by scanning electron microscopy (SEM) and TGA method. The adsorption experiment indicated a maximum boron load capacity of ca. 1.55mmolg−1. The high load capacity was attributed to specific chemical affinity and physical adsorption. Highly effective removal of boric acid from aqueous solution was observed for the adsorbent even in the synthetic seawater containing high concentration of foreign ions. Analysis of adsorption thermodynamic and kinetics revealed a spontaneous sorption process that is driven by enthalpy change and limited by chemical reaction. The exhausted adsorbent was regenerated for repeated use by treating with 3% HCl solution, followed by neutralizing with 3% NH3·H2O at ambient temperature. Only 7% capacity loss was observed after five continuous adsorption–regeneration cycles.

Keywords: Boron adsorbent; Silica–polyallylamine composites; N-methyl-; d; -glucamine

Pb(II) and Zn(II) adsorption onto Na- and Ca-montmorillonites in acetic acid/acetate medium: Experimental approach and geochemical modeling by Mariem Ghayaza; Lydie Le Forestier; Fabrice Muller; Christophe Tournassat; Jean-Michel Beny (pp. 238-246).
Lead sorption isotherm onto Na-montmorillonite at pH 5 and contribution of the different sorption mechanisms: cation exchange (CE-Pb) and surface complexation onto the strong (SSOPb) and weak (SWOPb) sites.Display Omitted► Higher Zn and Pb sorption onto Na-montmorillonite than onto the calcic clay at pH 5. ► Increasing acetic acid/acetate concentration decreases Pb and Zn adsorption. ► Determination of new selectivity coefficients for PbNa and PbCa equilibria. ► Contribution of cation exchange and surface complexation onto strong and weak sites.Smectites are usually used as a clay barrier at the bottom of subsurface waste landfills due to their low permeability and their capacity to retain pollutants. The Na- and Ca-saturated SWy2 montmorillonites were interacted with initial Zn(NO3)2 or Pb(NO3)2 concentrations ranging from 10−6 to 10−2M with a solid/liquid ratio of 10gL−1 and using acetic acid/acetate as buffer at pH 5 in order to reproduce a biodegradable leachate of a young landfill. These experiments revealed that Zn and Pb sorption onto Na-SWy2 is higher than that onto Ca-SWy2 in the whole range of concentrations. Metal retention into both montmorillonites increases with the decrease in acetic acid/acetate concentration. The two-site protolysis model with no electrostatic term (2SPNE model) was used to model these experiments. As the experimental data of Zn sorption were well fitted, this model was validated and has been improved by taking into account the metal–acetate complexation in solution. In order to validate the model for Pb sorption, new selectivity coefficients have been determined, namely log Kc(PbNa)=0.5 for Na-montmorillonite and log Kc(PbCa)=0.3 for Ca-montmorillonite.

Keywords: Adsorption; Lead; Zinc; Cation exchange; Surface complexation

Adsorption of tetracycline onto goethite in the presence of metal cations and humic substances by Yanping Zhao; Jinju Geng; Xiaorong Wang; Xueyuan Gu; Shixiang Gao (pp. 247-251).
Copper (II) significantly enhanced tetracycline adsorption via acting as a bridge ion to form goethite–Cu2+–tetracycline complex because Cu2+ could form strong and specific inner-sphere surface complexes.Display Omitted► Background electrolyte cations showed almost no effect on tetracycline adsorption onto goethite. ► Copper (II) and humic acid enhanced the adsorption to different extent. ► Tetracycline was adsorbed by goethite through inner-sphere complextion. ► Copper (II) and humic acid have great effects on tetracycline mobility in soils.Adsorption of tetracycline, one of the most widely used antibiotics, onto goethite was studied as a function of pH, metal cations, and humic acid (HA) over a pH range 3–10. Five background electrolyte cations (Li+, Na+, K+, Ca2+, and Mg2+) with a concentration of 0.01M showed little effect on the tetracycline adsorption at the studied pH range. While the divalent heavy metal cation, Cu2+, could significantly enhance the adsorption and higher concentration of Cu2+, stronger adsorption was found. The results indicated that different adsorption mechanisms might be involved for the two types of cations. Background electrolyte cations hardly interfere with the interaction between tetracycline and goethite surfaces because they only form weak outer-sphere surface complexes. On the contrary, Cu2+ could enhance the adsorption via acting as a bridge ion to form goethite–Cu2+–tetracycline surface complex because Cu2+ could form strong and specific inner-sphere surface complexes. HA showed different effect on the tetracycline sorption under different pH condition. The presence of HA increased tetracycline sorption dramatically under acidic condition. Results indicated that heavy metal cations and soil organic matters have great effects on the tetracycline mobility in the soil environment and eventually affect its exposure concentration and toxicity to organisms.

Keywords: Tetracycline; Adsorption; Goethite; Inner-sphere complex; Cations; Humic acid

A proton NMR study on the specific sorption of yttrium(III) and europium(III) on gamma-alumina [γ-Al2O3] by N. Huittinen; P. Sarv; J. Lehto (pp. 252-258).
The specific sorption of the trivalent metals europium and yttrium on γ-Al2O3 was investigated.1H NMR spectra of γ-alumina with varying concentrations of europium (blue colors) and yttrium (red colors) are presented.Display Omitted►1H NMR investigation of Eu(III) and Y(III) sorption on γ-alumina. ► Physisorbed water is not fully removed from the γ-alumina surface upon drying. ► Surface complexation of Y3+ removes a wide range of protons from the mineral surface. ► Bridging and terminal hydroxyls participate in surface complexation reactions.The specific sorption of Eu(III) and Y(III) on γ-alumina was investigated with solid-state1H NMR. Solution pH was shown to influence the recorded1H NMR spectra of γ-alumina, and thus, metal ion-containing samples were prepared under constant pH conditions, 8.00±0.05. The metal ion concentration in the samples was varied between 6.58×10−7 M–3.95×10−4 M in case of Y3+ and 6.58×10−8 M–1.32×10−4 M in case of Eu3+. The mineral concentration was kept constant at 4g/l. After separation of the liquid phase, the samples were dried under vacuum to remove physisorbed water from the mineral surface. However, even after 48h of drying at 150°C and 20 mTorr, water was still detected in the proton spectra as two distinct peaks with chemical shifts at 1.3 and 0.9ppm. The europium addition to the γ-alumina samples induced significant spectral changes in comparison with yttrium-containing samples. These changes were attributed to the paramagnetism of europium rather than to complexation reactions occurring on the mineral surface. Proton spectra obtained for yttrium samples were therefore used to detect the spectral changes induced by the sorption reaction itself. The results revealed a large distribution of protons being removed from the mineral surface upon yttrium complexation. Removed protons were assigned to both bridging surface hydroxyls such as (AlVI)2–OH as well as to terminal hydroxyls, e.g., of type AlVI–OH. Acidic protons belonging to (AlVI)3–OH groups were not observed to participate in the surface reaction.

Keywords: 1; H NMR; Sorption; Eu(III); Y(III); Proton spectrum; Chemical shift

Formation of uniform ferrocenyl-terminated monolayer covalently bonded to Si using reaction of hydrogen-terminated Si(111) surface with vinylferrocene/ n-decane solution by visible-light excitation by Hikaru Sano; Mingxiu Zhao; Daiji Kasahara; Kuniaki Murase; Takashi Ichii; Hiroyuki Sugimura (pp. 259-269).
Uniform ferrocenyl-terminated monolayer covalently bonded to Si was formed using reaction of H–Si(111) surface with vinylferrocene/ n-decane solution by visible-light excitation, and the resulting VFC-SAM on n-type Si showed positive photo-responsivity.Display Omitted► Ferrocenyl-terminated monolayer was directly formed on Si by visible-light excitation. ► The uniformity of the resulting VFC-SAM was examined by AFM. ► The resulting VFC-SAM on n-type Si showed positive photo-responsivity.Electrochemically active self-assembled monolayers (SAM) have been successfully fabricated with atomic-scale uniformity on a silicon (Si)(111) surface by immobilizing vinylferrocene (VFC) molecules through Si–C covalent bonds. The reaction of VFC with the hydrogen-terminated Si (H–Si)(111) surface was photochemically promoted by irradiation of visible light on a H–Si(111) substrate immersed in n-decane solution of VFC. We found that aggregation and polymerization of VFC was avoided when n-decane was used as a solvent. Voltammetric quantification revealed that the surface density of ferrocenyl groups was 1.4×10−10molcm−2, i.e., 11% in substitution rate of Si–H bond. VFC-SAMs were then formed by the optimized preparation method on n-type and p-type Si wafers. VFC-SAM on n-type Si showed positive photo-responsivity, while VFC-SAM on p-type Si showed negative photo-responsivity.

Keywords: Self-assembled monolayer; Ferrocenyl group; Vinylferrocene; Electrochemically active; AFM; Cyclic voltammetry

Graphene and graphene oxide as effective adsorbents toward anionic and cationic dyes by G.K. Ramesha; A. Vijaya Kumara; H.B. Muralidhara; S. Sampath (pp. 270-277).
Graphene/graphene oxide – effective adsorbents for anionic and cationic dyes.Display Omitted► Exfoliated graphene and graphene oxide are shown to be very good adsorbents for various charged dye molecules. ► Depending on the charge on the dye, either graphene oxide or reduced graphene oxide can be used for effective adsorption. ► Molecular level interactions between the adsorbents and dyes have been probed using spectroscopic techniques. ► Adsorption isotherms are studied in detail. ► High surface area of graphene – based materials are used for environmental decontamination.In the present study, exfoliated graphene oxide (EGO) and reduced graphene oxide (rGO) have been used for the adsorption of various charged dyes such as methylene blue, methyl violet, rhodamine B, and orange G from aqueous solutions. EGO consists of single layer of graphite decorated with oxygen containing functional groups such as carboxyl, epoxy, ketone, and hydroxyl groups in its basal and edge planes. Consequently, the large negative charge density available in aqueous solutions helps in the effective adsorption of cationic dyes on EGO while the adsorption is negligible for anionic dyes. On the other hand, rGO that has high surface area does not possess as high a negative charge and is found to be very good adsorbent for anionic dyes. The adsorption process is followed using UV–Visible spectroscopy, while the material before and after adsorption has been characterized using physicochemical and spectroscopic techniques. Various isotherms have been used to fit the data, and kinetic parameters were evaluated. Raman and FT-IR spectroscopic data yield information on the interactions of dyes with the adsorbent.

Keywords: Graphene oxide; Reduced graphene oxide; Dyes; Vibrational spectroscopy; Adsorption isotherm

Effects of confinement on the molar enthalpy of argon adsorption in graphitic cylindrical pores: A grand canonical Monte Carlo (GCMC) simulation study by Zhongjun Liu; D.D. Do; D. Nicholson (pp. 278-287).
This figure shows snapshots for the argon adsorption at 77K in multi-walled carbon nanotube at different pressures. It is clearly seen that the mechanism of adsorption under subcritical conditions starts with a layering mechanism (snapshots A–C). This is followed by a capillary condensation step (snapshot D). The RHS shows unfolded top view of each snapshot.Display Omitted► Integral molar enthalpy is a proper variable to describe heat of adsorption under supercritical conditions. ► The strong confinement results in higher heat of adsorption. ► The behaviour of surface excess in a cylinder under supercritical conditions is similar to that on a flat surface. ► Supercritical adsorption is a densification process reflected by the behaviour of layer compressibility.Using a grand canonical Monte Carlo simulation, we study argon adsorption in graphitic cylindrical pores to investigate the differences between the isosteric heat and the integral molar enthalpy under subcritical and supercritical conditions and compare these results against those for a flat graphite surface to investigate the role of confinement on the enthalpy change of adsorption. The isosteric heat curve is finite under subcritical conditions, but for supercritical adsorption, it becomes infinite at the pressure where the excess concentration versus pressure is maximum. This can be circumvented using the integral molar enthalpy, which is a better variable to describe the energy change for supercritical adsorption. Finally, the effects of pore geometry (radius and length) on argon adsorption under subcritical and supercritical conditions are discussed.

Keywords: Argon adsorption; Cylindrical pore; Enthalpy change of adsorption; Confinement; Supercritical adsorption

Phenol adsorption on closed carbon nanotubes by Agnieszka Pacholczyk; Artur P. Terzyk /; Marek Wiśniewski; Piotr A. Gauden; Radosław P. Wesołowski; Sylwester Furmaniak; Aleksandra Szcześ; Emil Chibowski; Bartosz Kruszka (pp. 288-292).
The fit of bimodal Langmuir model to experimental data.Display Omitted► Phenol adsorption on a series of eight closed carbon nanotubes was measured. ► We observe the linear correlation between surface area of tubes calculated from phenol and nitrogen adsorption. ► Phenol can be applied as a probe molecule for comparative analysis of tube surface areas. ► Adsorption process is mainly determined by the value of tube external surface areas and the tubes behave almost independently.We present the results of systematic studies of phenol adsorption on closed commercially available, unmodified carbon nanotubes. Phenol adsorption is determined by the value of tube-specific surface area, the presence of small amount of surface groups influence adsorption only in very small amount. Phenol can be applied as a probe molecule for comparative analysis of tube surface areas. Tube curvature influences adsorption from solution, i.e., we observe increasing adsorption energy (and slower desorption process) with the decrease in tube curvature. This is in full accordance with molecular simulation results.

Keywords: Adsorption; Carbon nanotube; Phenol; Thermal analysis

Computational methods for intramolecular electron transfer in a ferrous–ferric iron complex by Piotr Zarzycki; Sebastien Kerisit; Kevin Rosso (pp. 293-306).
The archetypal bridged ferrous–ferric electron transfer system in aqueous solution used to study the limitations of common theoretical and molecular computational approaches for predicting electron transfer quantities and corresponding symmetric potential energy surface.Display Omitted► New prototype for electron transfer at oxide surfaces. ► Poor basis set error as large as kT. ► Implicit solvent model is as good as SPC/E. ► Negative entropic effect on electron transfer. ► New assessments of isotopic signatures for electron transfer.The limitations of common theoretical and molecular computational approaches for predicting electron transfer quantities were assessed, using an archetypal bridged ferrous–ferric electron transfer system in aqueous solution. The basis set effect on the magnitude of the electronic coupling matrix element computed using the quasi-diabatic method was carefully examined, and it was found that the error related to a poor basis set could exceed the thermal energy at room temperature. A range of approaches to determining the external (solvent) reorganization energy were also investigated. Significant improvements from the Marcus continuum model can be obtained by including dipolar Born–Kirkwood–Onsager correction. In this regard, we also found that Klamt’s Conductor-Like Screening Model (COSMO) yields estimations of the external reorganization energy similar to those obtained with explicit solvent molecular dynamics simulations if the fast-frequency modes are neglected, which makes it an attractive alternative to laborious umbrella sampling simulations. By using the COSMO model, we also confirm that a decrease in curvature of the potential energy surface is a manifestation of the dielectric saturation observed in the first solvation layer. The linearity of solvent response to the charge redistribution was assessed by analyzing the energy gap autocorrelation function as well as the solvent density and dipole moment fluctuations. Molecular dynamics was also used to evaluate the sign and magnitude of the solvent reorganization entropy and to determine its effect on the predicted electron transfer rate. Finally, we present a simple way of estimating the vibration frequency along the reaction coordinate, which also enables prediction of the mass-dependent isotopic signature of electron transfer reactions.

Keywords: Adiabatic electron transfer; External reorganization energy; Umbrella sampling; Electron transfer entropy; Gaussian fluctuations; Solvent linear response; Electronic coupling matrix element

Activated carbon fibers with a high content of surface functional groups by phosphoric acid activation of PPTA by Alberto Castro-Muñiz; Fabián Suárez-García; Amelia Martínez-Alonso; Juan M.D. Tascón (pp. 307-315).
Synthetic ACFs with high porosity development and a large amount of oxygen-, phosphorus- and nitrogen-containing surface groups prepared from PPTA by chemical activation with H3PO4.Display Omitted► Activation of polymeric fibers by chemical activation with phosphoric acid. ► Effect of phosphoric acid in the degradation of the polymer. ► Large amount of surface groups were obtained with the chemical activation. ► Porosity development increases with impregnation ratio.Activated carbon fibers (ACFs) were prepared by chemical activation of poly( p-phenylene terephthalamide (PPTA) with phosphoric acid, with a particular focus on the effects of impregnation ratio and carbonization temperature on both surface chemistry and porous texture. Thermogravimetric studies of the pyrolysis of PPTA impregnated with different amounts of phosphoric acid indicated that this reagent has a strong influence on the thermal degradation of the polymer, lowering the decomposition temperature and increasing the carbon yield. As concerns surface chemistry, TPD and chemical analysis results indicated that the addition of phosphoric acid increases the concentration of oxygenated surface groups, with a maximum at an impregnation ratio of 100wt.%. The resulting materials present uncommon properties, namely a large amount of oxygen- and phosphorus-containing surface groups and a high nitrogen content. Porosity development following H3PO4 activation was very significant, with values close to 1700m2/g and 0.80cm3/g being reached for the BET surface area and total pore volume, respectively. The pore size distributions remained confined to the micropore and narrow mesopore (<10nm) range.

Keywords: Activated carbon fibers; Surface functional groups; PPTA; Phosphoric acid; Adsorption

Effect of chain length of self-assembled monolayers in dip-pen nanolithography using molecular dynamics simulations by Cheng-Da Wu; Te-Hua Fang; Jen-Fin Lin (pp. 316-320).
(a) Snapshots of MD simulation of DPN at a given pull-off distance for various number of methylene in a chain. (b) Variation of adsorbed area and pattern height versus the number of methylene groups.Display Omitted► Shorter molecules have better transport and diffusion abilities. ► The magnitude of adsorbed energy decreases with increasing chain length. ► The magnitudes of adsorbed area and pattern height decrease with increasing chain length.The pattern transfer mechanism of an alkanethiol self-assembled monolayer (SAM) with different chain lengths during the dip-pen nanolithography (DPN) process and pattern characterizations are studied using molecular dynamics (MD) simulations. The mechanisms of molecular transference, alkanethiol meniscus characteristics, surface adsorbed energy, transfer number, and pattern formation are evaluated during the DPN process at room temperature. The simulation results clearly show that the molecular transfer ability in DPN is strongly dependent on the chain length. Shorter molecules have significantly better transport and diffusion abilities between the meniscus and substrate surface, and the transport period can be maintained longer. The magnitude of adsorbed energy increases with chain length, so many more molecules can be transferred to the surface when shorter molecules are used. After deposition, the magnitude of the adsorbed area and pattern height decrease with increasing chain length.

Keywords: Dip-pen nanolithography; SAM; Chain length; Meniscus; Molecular dynamics

Effect of hydrophobicity on the stability of the wetting films of water formed on gold surfaces by L. Pan; S. Jung; R.-H. Yoon (pp. 321-330).
A disjoining pressure isotherm in the wetting film of water formed on a gold surface with θr=81°.Display Omitted► Measurement of negative disjoining pressures in wetting films. ► Analytical expression for disjoining pressure has been derived. ► The long-range hydrophobic force is responsible for accelerated film thinning. ► Effect of slip on wetting film drainage is discussed.We have developed a methodology that can be used to determine disjoining pressures ( Π) in both stable and unstable wetting films from the spatial and temporal profiles of dynamic wetting films. The results show that wetting films drain initially by the capillary pressure created by the changes in curvature at the air/water interface and subsequently by the disjoining pressure created by surface forces. The drainage rate of the film formed on a gold surface with a receding contact angle ( θr) of 17° decreases with film thickness due to a corresponding increase in positive Π, resulting in the formation of a stable film. The wetting film formed on a hydrophobic gold with θr=81° drains much faster due to the presence of negative Π in the film, resulting in film rupture. Analysis of the experimental data using the Frumkin–Derjaguin isotherm suggests that short-range hydrophobic forces are responsible for film rupture and long-range hydrophobic forces accelerate film thinning.

Keywords: Wetting film; Hydrophobic force; Kinetics of film thinning; Disjoining pressure; DLVO theory; Frumkin–Derjaguin isotherm

Solid-state radical grafting reaction of glycidyl methacrylate and poly(4-methyl-1-pentene) in supercritical carbon dioxide: Surface morphology and adhesion by Marcos H. Kunita; Marcos R. Guilherme; Lucio C. Filho; Edvani C. Muniz; Elton Franceschi; Claudio Dariva; Adley F. Rubira (pp. 331-337).
Solid-state radical grafting of glycidyl methacrylate onto poly(4-methyl-1-pentene) was performed using supercritical CO2. The grafting and morphology were controlled by time, temperature, and pressure of impregnation.Display Omitted► Solid-state radical grafting of glycidyl methacrylate (GMA) onto poly(4-methyl-1-pentene) (PMP) was performed using supercritical carbon dioxide (scCO2) impregnation technology. ► The grafting degree of the samples may be controlled by time, temperature, and pressure of impregnation. ► Better graft response was obtained for pressure of 130bar, temperature of 70°C and time of 7h. ► Adhesion characteristics of polymer films are dependent on grafting degree of GMA.Solid-state radical grafting of glycidyl methacrylate (GMA) onto poly(4-methyl-1-pentene) (PMP) was performed using supercritical carbon dioxide (scCO2) impregnation technology. The polymer films were firstly impregnated in the scCO2 phase with the GMA using benzoyl peroxide as thermal initiator. The grafting degree and surface morphology of the samples may be controlled by the following factors: time, temperature, and pressure of impregnation. A 23 factorial design to evaluate the main and interaction effects of such factors on the grafting of the PMP by GMA (grafting response) was elaborated from FTIR data. The superior and inferior limits of the levels were defined on basis of a P- x- y diagram for binary system CO2+GMA that provided the location of the transition curves of such a system. Better grafting response was obtained for pressure of 130bar, temperature of 70°C and time of 7h. The PMP- g-GMA films exhibited a thermal profile similar to that of the unmodified polymer. Adhesion characteristics of polymer films are dependent on grafting degree of GMA.

Keywords: Adhesion; Surface morphology; Graft polymers; Solid-state radical polymerization; Supercritical carbon dioxide impregnation

Effect of gamma irradiation on gas-ionic liquid and water-ionic liquid interfacial stability by Susan E. Howett; Jiju M. Joseph; James J. Noël; J. Clara Wren (pp. 338-350).
Gamma-irradiation does not induce significant chemical decomposition of IL molecules, but accelerates the micelle formation at the IL-water interface. The small organic molecules produces from the radiolytic decomposition of the IL act as loci for micelle formation, increasing the rate of emulsification and mixing of the IL and water phases.Display Omitted► The effect of gamma-irradiation of IL either in contact with water or with gas was studied by conductivity measurements and Raman spectroscopy. ► In the IL-water biphasic systems, γ-irradiation does not significantly induce chemical decomposition of the IL molecules into smaller products. ► Radiation increases the IL cation and anion interfacial transfer rates and accelerates micelle formation. ► This work is the first to observe radiation-induced IL-water phase mixing. ► A mechanism is proposed, showing that γ-radiation affects the potential gradient at the interface, increasing interfacial charge transfer.The effect of γ-radiation on gas-ionic liquid (IL) and water-IL interfacial stability was investigated. Three phosphonium-based ILs, which vary considerably in their viscosity, conductivity and miscibility with water, were examined. The gas phase above the IL samples (headspace gas) was analyzed using gas chromatography with a mass spectrometer detector while the changes in the IL and aqueous phases were followed by conductivity measurements and Raman spectroscopy. For the gas-IL systems, the headspace samples showed trace amounts of the radiolytic decomposition products of the ILs that were small and volatile enough to become airborne. The type of cover gas, air or Ar, had no effect on the gas speciation. Negligible changes in the conductivity and the Raman spectra of the IL phase due to irradiation indicate that γ-irradiation induces negligible chemical changes in the IL phase when it is in contact with a gas phase. For the water-IL systems, the initially immiscible layers slowly developed an interfacial emulsion layer, even in the absence of radiation. This layer started at the water-IL interface and then grew downwards, eventually converting the entire IL phase to an emulsion. Gamma-irradiation accelerated the conversion of the IL phase to an emulsion. The development of the emulsion layer was accompanied by changes in the conductivity and the Raman spectra of both the IL and water phases. Based on these results, a mechanism involving the formation of micelles at, or near, the water-IL interface has been proposed to explain the development of an emulsion layer. We also suggest that radiolytic decomposition of ILs produces surfactants that can accumulate at the interface and, even at low concentrations, accelerate the emulsification process.

Keywords: Ionic liquid; Gamma-radiolysis; Interfacial stability; Phase mixing; Micelles

How to obtain a well-spread monolayer of lysozyme at the air/water interfaces by M. Miñones Conde; O. Conde; J.M. Trillo; J. Miñones Jr. (pp. 351-360).
Study to define the conditions required to obtain a complete spreading of the lysozyme monolayer at the A/W interface using Trurnit’s method and others.Display Omitted► The working conditions for a full spreading of lysozyme monolayer were studied. ► Trurnit’s spreading method, ionic strength substrate, spread number of molecules and waiting time for the recorded of the monolayer were analyzed. ► The limiting area corresponding to a complete spreading of unfolding lysozyme monolayer was 1m2/mg.The purpose of this study is to define the conditions required to obtain a complete spreading of the lysozyme monolayer at the A/W interface. To this end, using Trurnit’s method, the influence of the ionic strength of the substrate, the elapsed time between the spreading of the monolayer and the beginning of its compression, and the number of lysozyme molecules spread at the interface was studied. The results obtained show that the lysozyme spreading is conditioned by the unfolding of amino acid chains which form part of its structure, so that such unfolding is hindered, either because of an excessive accumulation of lysozyme molecules on the substrate surface or because the waiting time necessary to get this unfolding is not long enough, regardless of the number of spread molecules. The complete unfolding of lysozyme, which involves the loss of tertiary and secondary structures, has been obtained in this work under certain conditions: (1) using a substrate with a high saline concentration (NaCl 3–3.5M) and at a pH value close to the isoelectric point of lysozyme (pI=11) in order to reduce the solubility and the electrical potential of the protein, (2) increasing the elapsed time between the spreading of the protein and the beginning of its compression to 3h in order to get a complete unfolding of lysozyme, which is a very slow process, (3) using an initial spreading area of 2.1m2/mg or larger (equivalent to a protein surface concentration of less than 2×1012molec/cm2) to reduce the accumulation of protein molecules at the surface, thus facilitating their unfolding, and (4) using Trurnit’s spreading method, although for the spreading of this protein was found to be insufficiently significant.

Keywords: Lysozyme; Monolayers; BAM

Coating typologies and constrained swelling of hyaluronic acid gels within scaffold pores by M. Arnal-Pastor; A. Vallés-Lluch; M. Keicher; M. Monleón Pradas (pp. 361-369).
Types of HA coating in the scaffolds’ pores obtained by changing the concentration of the solution and the number of cycles, range from sparse aggregates to complete filling of the pore lumen.Display Omitted► A set of elastomeric scaffolds was prepared and coated with hyaluronic acid. ► The gel is deposited on the pores as disconnected aggregates or a continuous layer. ► The swelling capacity depends on the layer typology and on the scaffold constraint. ► The theory of swelling was adapted to account for the effect of constraint build-up.A set of elastomeric scaffolds with a well defined porous structure was prepared with a template leaching procedure and coated with hyaluronic acid solutions. Depending on the coating process parameters the hyaluronic acid deposited on the pores had configurations ranging from thin disconnected aggregates to a thick continuous layer on the pore surface. The development of the coating layer was studied by scanning electron microscopy and the materials were subjected to dynamical and equilibrium swelling experiments in a water vapor ambient of fixed activity. The porosity change due to coating and to swelling of the coating layer were determined. The hyaluronic acid coating the pores has a different swelling capacity depending on the type of layer formed, as a consequence of the scaffold constraint and of the layer typology. These factors were investigated analytically by modifying the standard theory of gel swelling. An experimental quantity is introduced which reflects the constrainment build-up on gel swelling.

Keywords: Scaffold; Hyaluronic acid/hyaluronan; Swelling

An investigation of the stable orientations of orthorhombic particles in a thin film and their effect on its critical failure pressure by G. Morris; S.J. Neethling; J.J. Cilliers (pp. 370-380).
Simulations of orthorhombic particles of different aspect ratio attached to a thin film are used to identify their energetically stable orientations, which affect the film stability.Display Omitted► Shape and contact angle affect a particle’s stable orientations. ► Orientation affects film stability. ►Four types of orientation: horizontal, vertical, rotated and diagonal. ► Wider, flatter particles require higher failure pressures.The effects of shape and contact angle on the behaviour of orthorhombic particles at an interface and in thin films were investigated using Surface Evolver. It is shown that the energetically stable orientations of the particle change with its aspect ratio. Long, wide, flat particles with low contact angles are more stable in flat orientations, i.e. with two faces parallel to the flat film surface. More cubic particles with higher contact angles are more stable in twisted orientations, where the opposite sides of the film can be drawn together at the sharp edges of the particle.The combination of contact angle and orientation has been found to have a large effect on the capillary pressure required to rupture the film. A film containing a particle in a flat orientation will rupture at a capillary pressure up to three times greater than one containing an identical particle in a twisted orientation. Wider, flatter particles with low contact angles stabilise thin liquid films to a greater extent than cubic particles with high contact angles.

Keywords: Orthorhombic particles; Orientations; Thin films; Energetic stability; Film failure

Ambient pressure effects on the electrokinetic potential of Zeonor–water interfaces by Vishal Tandon; Brian J. Kirby (pp. 381-387).
Display Omitted►The electrokinetic potential of a Zeonor–water interface is a function of ambient pressure. ► Reduced air pressure decreases the equilibration time of the electrokinetic potential. ► Hysteresis is observed of the electrokinetic potential with dissolved gas content.Using phase-sensitive streaming potential experiments in a vacuum chamber, we demonstrate that lowering the ambient pressure of the air surrounding a hydrophobic, Zeonor microfluidic substrate results in a decrease in the time scale required for equilibration of the electrokinetic potential. At ambient air pressures below 0.74atm, the electrokinetic potential changes from ∼−84mV to ∼−11mV in 5h, while the same decrease occurs in a period of over 200h when the system is at 1atm. Returning a sub-atmospheric system (where the electrokinetic potential had equilibrated to −11mV) to atmospheric pressure did not result in any additional change in the electrokinetic potential. This can be described as a type of hysteresis of the electrokinetic potential with dissolved gas concentration. No time or pressure dependence was observed for the electrokinetic potential of hydrophilic (silica) substrates.

Keywords: Hydrophobic; Electrokinetic potential; Zeta potential; Microfluidic; Nanobubble; Hysteresis; Electroosmosis; Electrophoresis; Electroosmotic mobility; Electrophoretic mobility; Cyclic olefin copolymer

One-step controllable fabrication of superhydrophobic surfaces with special composite structure on zinc substrates by Tao Ning; Wenguo Xu; Shixiang Lu (pp. 388-396).
The structure model and SEM image of the prepared superhydrophobic surface with the highest CA value, which is composed of novel and interesting composite structure..Display Omitted► We use one-step method to fabricate superhydrophobic surfaces. ► Novel composite structure is only responsible for the superhydrophobicity. ► We fabricate superhydrophobic pure platinum surfaces initiatively. ► Morphologies and hydrophobic properties are controllable.Stable superhydrophobic platinum surfaces have been effectively fabricated on the zinc substrates through one-step replacement deposition process without further modification or any other post-treatment procedures. The fabrication process was controllable, which could be testified by various morphologies and hydrophobic properties of different prepared samples. By conducting SEM and water CA analysis, the effects of reaction conditions on the surface morphology and hydrophobicity of the resulting surfaces were carefully studied. The results show that the optimum condition of superhydrophobic surface fabrication depends largely on the positioning of zinc plate and the concentrations of reactants. When the zinc plate was placed vertically and the concentration of PtCl4 solution was 5mmol/L, the zinc substrate would be covered by a novel and interesting composite structure. The structure was composed by microscale hexagonal cavities, densely packed nanoparticles layer and top micro- and nanoscale flower-like structures, which exhibit great surface roughness and porosity contributing to the superhydrophobicity. The maximal CA value of about 171° was obtained under the same reaction condition. The XRD, XPS and EDX results indicate that crystallite pure platinum nanoparticles were aggregated on the zinc substrates in accordance with a free deposition way.

Keywords: Superhydrophobic surfaces; Platinum; Composite structure; Wettability

Nanoscale repulsive forces between mica and silica surfaces in aqueous solutions by Sergio M. Acuña; Pedro G. Toledo (pp. 397-399).
Nanoscale repulsive forces between mica and silica surfaces in aqueous solutions obey a universal law in the short range, less than ∼1nm or about 3–4 water molecules.Display Omitted► Force curves for mica-silica are measured with an AFM. ► The force has universal character in the short range, for different solutions. ► The force is the same as for glass-silica. ► Force curves show oscillations with period ∼0.25 nm, the size of a water molecule. ► Force between mineral surfaces in water arises from a surface-induced water effect.Nanoscale repulsive forces between mineral surfaces in aqueous solutions were measured for the asymmetric mica–silica system. The force measured with an atomic force microscope (AFM) has universal character in the short range, less than ∼1nm or about 3–4 water molecules, independent of solution conditions, that is, electrolyte ion (Na, Ca, Al), concentration (10−6–10−2M), and pH (3.9–8.2). Notably, the force is essentially the same as for the glass–silica system. Single force curves for a mica–silica system in a 10−4M aqueous NaCl solution at pH∼5.1 show oscillations with a period of about 0.25nm, roughly the diameter of a water molecule, a consequence of a layer-by-layer dehydration of the surfaces when pushed together. This result provides additional support to the idea that nanoscale repulsive forces between mineral surfaces in aqueous solutions arise from a surface-induced water effect; the water between two mineral plates that are pushed together becomes structured and increasingly anchored to the surface of the plates by the creation of a hydrogen-bonding network that prevents dehydration of the surfaces.

Keywords: Nanoscale forces; Repulsive forces; Mica; Silica; AFM; Water structure

Fabrication of block copolymer brushes on hollow sphere surface via reverse iodine transfer polymerization by Li-Ping Wang; Li-Hua Dong; Jing-Cheng Hao; Xin-Hu Lv; Wen-Zhi Li; Yu-Chao Li; Jin-Ming Zhen; Yu-Cheng Hao; Fei Ma (pp. 400-406).
In this study, the rare earth optical functional block copolymer brushes grafted from silicon hollow sphere surface via reverse iodine transfer polymerization (RITP) were investigated.Display Omitted► PMMA has grafted from hollow sphere surface via RITP. ► The RITP was a controlled process with a “living” characteristic. ► PMMA grafted from hollow sphere surface has the ability to extend chains. ► HS-g-PMMA-b-Tb complex hybrid materials exhibited strong fluorescence properties.The block copolymer brushes grafted from hollow sphere surface via reverse iodine transfer polymerization (RITP) were investigated in this work. A sufficient amount of azo initiator was introduced onto hollow sphere surface firstly. Then the monomer methyl methacrylate (MMA) was polymerized via surface-initiated reverse iodine transfer polymerization (RITP) using azo group modified hollow sphere as initiator. The microstructure of the samples was characterized by FT-IR,1H NMR, respectively. Results indicated that the poly(methyl methacrylate) (PMMA) with end functionality of alkyl iodine group had grafted from hollow sphere surface. TEM observations showed that the average diameter of hollow core was central at 1.3–1.4μm and the average wall thickness increased from 103nm to 138nm and 172nm after grafting polymerization of MMA and Tb complex, respectively. The closely linear plots of molecular weight (M n) versus conversion, linear kinetic plots for the free polymer formed in solution and the ability to extend the chains by sequential addition of monomer indicated that the RITP was a controlled process with a “living” characteristic.

Keywords: Polymer brushes; Hollow sphere; RITP; “Living” characteristic

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