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Journal of Colloid And Interface Science (v.322, #1)

Editorial Board (pp. ofc).

One step preparation of superhydrophobic polymeric surface with polystyrene under ambient atmosphere by Shuaixia Tan; Qiongdan Xie; Xiaoying Lu; Ning Zhao; Xiaoli Zhang; Jian Xu (pp. 1-5).
Brassica oleracea-like polymer surface is facilely fabricated by one-step casting process using amorphous polystyrene (PS) under ambient atmosphere. The obtained coatings show excellent superhydrophobicity and only possess unitary micro-scale structure, similar to the natural brassica leaf. In addition, a simple topography analysis also roughly verifies superhydrophobic structure of branched and intermingled sticks and bumps. This process provides a fairly easy procedure for preparing superhydrophobic surface from common plastics. Moreover, it demonstrates that the micro/nano-binary structure is not necessary for superhydrophobicity, while unitary micro-scale structure for a polymer surface can exhibit outstanding water repellency as natural lotus. Brassica oleracea-like polymer surface is facilely fabricated by one-step casting process using amorphous polystyrene (PS) under ambient atmosphere. Moreover, a simple topography analysis verifies roughly superhydrophobic microstructure.

Keywords: Bionics; Polymer; Superhydrophobic; Phase separation; Contact angle

Adsorption and surface complexation of trimesic acid at the α-alumina–electrolyte interface by Jayanta M. Borah; Sekh Mahiuddin (pp. 6-12).
Adsorption kinetics, adsorption isotherms and surface complexation of trimesic acid onto α-alumina surfaces were investigated. Adsorption kinetics of trimesic acid with an initial concentration of 0.5 mM onto α-alumina surfaces were carried out in batch method in presence of 0.05 mM NaCl(aq) at pH 6 and 298.15, 303.15 and 313.15 K. Adsorption isotherms were carried out at 298.15 K, pH 5–9, and 0.05 mM NaCl(aq) by varying trimesic acid concentration from 0.01 to 0.6 mM. Three kinetics equations such as pseudo-first-order, pseudo-second-order and Ho equations were used to estimate the kinetics parameters of the adsorption of trimesic acid on the α-alumina surfaces. Ho equation fits the experimental kinetics data significantly better and the estimated equilibrium concentration is in excellent agreement with the experimental value. The adsorption data were fitted to Freundlich and Langmuir adsorption model and the later best fits the adsorption isotherms. Comparison of adsorption density of trimesic acid with that of benzoic and phthalic acids follows the sequence: benzoic acidα-alumina is spontaneous and facile. DRIFT spectroscopic studies reveal that trimesate forms outer-sphere complexes with the surface hydroxyl groups that are generated onto α-alumina surfaces in the pH range of the study.Adsorption density depends on the number and the adjacent carboxylic groups in the benzene ring. The shifting ofνs(COO) andνas(COO) indicates that trimesate forms outer-sphere complexes with the surface hydroxyl groups that are produced onto α-alumina surface at all pH range of the study.

Keywords: Adsorption; α; -Alumina; Kinetics; DRIFT; Trimesic acid; Surface complexation

Factors affecting the sorption of trivalent chromium by zeolite synthesized from coal fly ash by Y.M. Yanming Sui; D.Y. Deyi Wu; D.L. Dalei Zhang; X.Y. Xiangyong Zheng; Z.B. Zhanbo Hu; H.N. Hainan Kong (pp. 13-21).
This research was initiated to determine the effects of different constituents and properties of zeolite synthesized from fly ash (ZFA) on Cr(III) sorption. The uptake of Cr(III) by ZFA was influenced greatly by pH, increasing with the increase in pH. The pH was controlled mainly by calcium-related components (especially CaCO3 and free CaO) and zeolite components in ZFAs. Sorption maximum of Cr(III) (Qm), determined by a repeated batch equilibration method, ranged from 22.29 to 99.91 mg/g for the 14 ZFAs. TheQm value correlated significantly with Ca-related components. The correlation coefficients were 0.9467, 0.5469, 0.7521, and 0.9195 for total Ca, CaCO3, CaSO4, and f.CaO, respectively. TheQm value was also closely related to cation-exchange capacity (r=0.6872) and specific surface area (r=0.7249). Correlation coefficients ofQm with dissociated Fe2O3 and Al2O3 were much higher than those of total Fe and total Al contents, respectively. It was suggested that, in ZFAs, zeolite and iron oxide acted as ion exchanger and adsorbent for Cr(III), respectively, while Ca components elevated the pH of the reaction system and consequently promoted ion exchange and adsorption and caused the surface precipitation of chromium hydroxide.Both the zeolite component and the nonzeolite component in zeolites synthesized from fly ashes contributed to sorption of Cr(III). The figure shows that the calcium component could increase pH and thus enhance sorption.

Keywords: Zeolite; Fly ash; Trivalent chromium; Sorption; Mechanism; Correlation coefficient; Composition

Sorption equilibria of CO2/CH4 mixture on activated carbon in presence of water by Yan Sun; Quanmin Xue; Yaping Zhou; Li Zhou (pp. 22-26).
The sorption isotherms of CO2 + CH4 mixtures on an activated carbon were collected in the presence of water at a temperature suitable for hydrate formation. The equilibrium composition of both phases was determined. The initial concentration of CO2 in mixtures was set at 33, 38 and 42%, and the total pressure was up to 10 MPa. CO2 hydrates were firstly formed following the increase of total pressure, and CO2 dominates the sorbed phase composition. CO2 concentration in the sorbed phase begins to decrease when the partial pressure of methane allows for the formation of methane hydrates. Competition for hydrate cavities was observed between CO2 and CH4 as reflected in the isotherm shape and phase composition at equilibrium. The formation pressure of hydrates is lower for mixtures than for pure gases, and the highest sorption capacity of each gas decreased in the mixture sorption either.Sorption isotherms of CH4 + CO2 mixture on wet activated carbon.

Keywords: Sorption; CO; 2; /CH; 4; mixture; Hydrate; Activated carbon; Water

Thermodynamics of naphthalene sorption to organoclays: Role of surfactant packing density by Runliang Zhu; Lizhong Zhu (pp. 27-32).
Temperature dependence of naphthalene sorption to four organoclays with different surfactant (CTMA+) packing densities was examined. The results showed that bothΔHo andΔSo increase generally with CTMA+ packing density. For organoclays with a low CTMA+ packing density, the sorption process is driven by both the enthalpy term(ΔHo) and the entropy term(−TΔSo), with values ranging from −4.7 to−7.5kJmol−1 and −15.9 to−20.8kJmol−1, respectively. As the CTMA+ packing density increases, the sorption process is driven by the entropy term (from −29.2 to−65.0kJmol−1) while it is opposed by the enthalpy term (from 7.9 to40.5kJmol−1). These results indicate that the enthalpy demand for cavity formation within the surfactant aggregates and the mixing entropy of solute with surfactant aggregates both increase with the surfactant packing density. This means that the surfactant aggregates will form various organic phases as their packing density varies. Controlling the surfactant aggregates within an intermediate packing density range can improve the sorption capacities of the organoclays.A schematic representation for naphthalene molecules partitioning into loosely packed (a) and densely packed (b) surfactant alkyl chain phases.

Keywords: Organoclays; Sorption; Thermodynamics; Surfactant

Influence of organic matter removal on competitive and noncompetitive adsorption of copper and zinc in acid soils by C. Pérez-Novo; M. Pateiro-Moure; F. Osorio; J.C. Nóvoa-Muñoz; E. López-Periago; M. Arias-Estévez (pp. 33-40).
We studied competitive and noncompetitive adsorption of copper and zinc in four acid soils, and compared the behavior of the two metals in untreated samples and samples treated with hydrogen peroxide to remove organic matter in the soil. Copper exhibited stronger competitive adsorption than zinc in the untreated samples. However, removal of organic matter reduced copper adsorption to a greater extent than zinc adsorption, the two metals exhibiting a more similar adsorption pattern than the untreated samples. The presence of copper dramatically reduced zinc competitive adsorption in untreated samples; on the other hand, that of zinc only resulted in slightly reduced competitive adsorption of copper. The hydrogen peroxide treatment decreased competitive adsorption in both metals; however, copper continued to be more efficient than zinc in competing for binding sites on adsorbing surfaces. Desorption of Cu occurred much less readily than desorption of Zn and hysteresis is apparent especially for Cu.(A) Example of noncompetitive adsorption in control samples (1530 μM); (B) noncompetitive adsorption in samples treated with H2O2; (C) competitive adsorption in control samples; (D) competitive adsorption in samples treated with H2O2.

Keywords: Copper; Zinc; Noncompetitive adsorption; Competitive adsorption; Organic matter; Desorption

A thermoreversible double gel: Characterization of a methylcellulose and κ-carrageenan mixed system in water by SAXS, DSC and rheology by Matija Tomšič; Florian Prossnigg; Otto Glatter (pp. 41-50).
Sol–gel and gel–sol thermal transition of methylcellulose/water, κ-carrageenan/water and methylcellulose/ κ-carrageenan/water mixtures was investigated utilizing small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC) and oscillatory rheological experiments in temperature regime from 20 to 80 °C. Methylcellulose (E461) and κ-carrageenan (E407) are well-known additives used for gelation in various nutrition and other products. The formulation and characterization of a mixed thermoreversible methylcellulose/ κ-carrageenan/water gel with very interesting double thermal transition gel–sol–gel upon heating was possible. This specific thermal behavior provides a liquid state of the system between the low-temperature and high-temperature gel-state and at the same time allows for the easy temperature tuning of the system's state. As such this system is suggested to be further tested as potential carrier for various functional colloidal systems.Gel–sol–gel transitions of thermo-reversible aqueous κ-carrageenan and methylcellulose solutions and mixtures thereof were characterized utilizing SAXS, DSC and rheology. Example: 2 wt% of 1:1 polymer mixture in water.

Keywords: Thermogelation; Sol–gel transition; Gel–sol transition; Mixed gel; Methylcellulose; κ; -Carrageenan; Thermoreversible gel

Film characterization of poly(styrene-butylacrylate-acrylic acid)–silica nanocomposite by Aiping Zhu; Aiyun Cai; Ziyi Yu; Weidong Zhou (pp. 51-58).
To improve the present unsatisfactory UV-shielding and water-resistance properties of many emulsion-type latexes, in this study, poly(styrene-butylacrylate-acrylic acid) (PSBA)-grafted–silica (PSBA-g-silica) hybrid nanoparticles were firstly prepared by suspension–dispersion–polymerization. The resulting hybrid nanoparticles were then used to add into PSBA latex to fabricate PSBA nanocomposites. The influence of PSBA-g-silica hybrid nanoparticles on the interfacial adhesion, film morphology, thermodynamics properties, UV-shielding, water-resistance and mechanical performance of PSBA films were investigated systematically. Our results revealed that filling 1.5 wt% PSBA-g-silica hybrid nanoparticles resulted in significant improvement in interfacial adhesion properties, UV-shielding, water-resistance and mechanical properties. Fabricating the silica-based latex nanocomposite is an effective approach to develop the new emulsion-type paints and adhesives.The SEM photography of section of PSBA nanocomposite filled with 1.5 wt% PSBA-g-silica hybrid nanoparticles, achieving good adhesive interface.

Keywords: PSBA latex; Nanocomposite; Water-resistance; UV-resistance; Interfacial properties

Architecture of brush-on-brush copolymers by photoinduced ATRP approach by Koji Ishizu; Takuya Murakami; Satoshi Takano (pp. 59-64).
We established a preparation method of brush-on-brush copolymers by grafting from photoinduced ATRP of multifunctional polystyrene havingN,N-diethyldithiocarbamate (DC) pendant groups with stearyl methacrylate (STM). We studied the solution properties of brush-on-brush copolymers from the view point of crowding effect of PSTM brush side chains. It was speculated from angular dependence on dynamic light scattering (DLS) that the brush-on-brush copolymer (BB1:PSTM brushes were grafted at regular intervals of 1/4 styrene units on the backbone) with large aspect ratio took a geometrical anisotropic conformation such as a cylinder due to crowding of brush side chains. In fact, transmission electron microscopy (TEM) photograph of such brush-on-brush showed a rigid rod-like morphology.The brush-on-brush copolymers (BB) were prepared by grafting from photoinduced ATRP of multifunctional polystyrene havingN,N-diethyldithiocarbamate (DC) pendant groups with stearyl methacrylate (STM). It was found from angular dependence on dynamic light scattering (DLS) that the BB with large aspect ratio took a geometrical anisotropic conformation due to crowding of brush side chains. TEM photograph of BB also showed a rigid rod-like morphology.

Keywords: Photoinduced ATRP; Graft polymerization; Rod polymer

Synergistic effects in flows of mixtures of wormlike micelles and hydroxyethyl celluloses with or without hydrophobic modifications by M.R. Rojas; A.J. Müller; A.E. Sáez (pp. 65-72).
This work presents experimental results on simple shear and porous media flow of aqueous solutions of two hydroxyethyl celluloses (HEC) and two hydrophobically modified hydroxyethyl celluloses (HMHEC) with different molecular weights. Mixtures of these polymers with a cationic surfactant, cetyltrimethylammonium p-toluenesulfonate (CTAT) were also studied. Emphasis was given to the range of surfactant concentrations in which wormlike micelles are formed. The presence of hydrophobic groups, the effect of the molecular weight of the polymers, the surfactant and polymer concentrations, and the effect of the flow field type (simple shear versus porous media flow) were the most important variables studied. The results show that the shear viscosity of HEC/CTAT solutions is higher than the viscosities of surfactant and polymer solutions at the same concentrations, but surface tension measurements indicate that no complex formation occurs between CTAT and HEC. On the other hand, a complex driven by hydrophobic interactions was detected by surface tension measurements between CTAT and HMHEC. In this case, the viscosity of the mixture increases significantly more (up to four orders of magnitude at high CTAT concentrations) in comparison with HEC/CTAT aqueous solutions. Increments in the molecular weight of the polymers increase the interaction with CTAT and the shear viscosity of the solution, but make phase separation more feasible. In porous media flow, the polymer/CTAT mixtures exhibited higher apparent viscosities than in simple shear flows. This result suggests that the extensional component of the flow field in porous media flows leads to a stronger interaction between the polymer and the wormlike micelles, probably as a consequence of change of conformation and growth of the micelles.Zero shear rate viscosity as a function of surfactant concentration for aqueous solutions of HMHEC1/CTAT, HMHEC2/CTAT, and CTAT in water. For HMHEC2, a region of phase separation was observed at CTAT concentrations below 4 mM. The CRC (1.9 mM) and wormlike micelle overlap concentrations (ϕ∗=11 mM) are literature values.

Keywords: CTAT; HEC; HMHEC; Polymer–surfactant; Wormlike micelles; Hydrophobes

Study of the interaction of β-cyclodextrin with phospholipid monolayers by surface pressure measurements and fluorescence microscopy by Christine Grauby-Heywang; Jean-Marie Turlet (pp. 73-78).
The interaction of β-cyclodextrin ( β-CD) with different lipids has been studied, using Langmuir monolayers kept at constant surface pressure or constant spreading surface. Results show that β-CD, injected beneath the monolayer, is able to desorb unsaturated palmitoyloleoylphosphatidylcholine (POPC) and sphingomyelin (SM) under specific experimental conditions. In this last case, SM monolayers, labeled with the fluorescent NBD-PC probe, were also observed by fluorescence microscopy, before and after β-CD injection. Images show that SM monolayers are more homogeneous after β-CD injection, because of the lipid desorption. At last, it seems that lipid desorption occurs only in a restricted surface pressure range, depending on the lipid.

Keywords: β; -Cyclodextrin; Phospholipid; Monolayer; Desorption; Surface pressure measurements; Fluorescence microscopy

Coupling between protein-laden films and a shearing bulk flow by A.N. Azadani; J.M. Lopez; A.H. Hirsa (pp. 79-86).
Two-dimensional protein crystallization on lipid monolayers at a quiescent air/water interface is now a well-established process, but it only operates under a very restricted set of conditions and on a very slow time scale. We have recently been able to significantly extend the conditions under which the proteins will crystallize as well as speed up the process by subjecting the interface to a shearing flow. Here, we investigate the two-way coupling between a protein-laden film and the bulk flow that provides the interfacial shear. This flow in a stationary open cylinder is driven by the constant rotation of the floor. Using the Boussinesq–Scriven surface model for a Newtonian interface coupled to the Navier–Stokes equations for the bulk flow, we find that the surface shear viscosity of protein-laden films under most conditions is small or negligible. This is the case for films subjected to constant shearing flow, regardless of the duration of the flow. However, when the film is intermittently sheared, significant surface shear viscosity is evident. In these cases, the surface shear viscosity is not uniform across the film.Two-way coupling was investigated between a protein-laden film and a bulk flow that enhances crystallization. Continuously sheared films exhibit small or negligible surface shear viscosity, whereas intermittently sheared films are viscous.

Keywords: Surface shear viscosity; Two-dimensional protein crystallization

Preparation of PLLA/PLGA microparticles using solution enhanced dispersion by supercritical fluids (SEDS) by Yunqing Kang; Guangfu Yin; Ping Ouyang; Zhongbing Huang; Yadong Yao; Xiaoming Liao; Aizheng Chen; Ximing Pu (pp. 87-94).
In this work, poly(l-lactic acid)/poly(lactide- co-glycolide) (PLLA/PLGA) microparticles were prepared using the technique of solution-enhanced dispersion by supercritical fluids (SEDS). For comparison, separate PLLA and PLGA microparticles were also produced by the same SEDS process. The produced microparticles were characterized by scanning electron microscopy, laser particle size analyzer, X-ray diffraction, differential scanning calorimetry, Fourier transform infrared spectroscopy, and gas chromatography. Results indicate that PLLA/PLGA microparticles possess sphere-like shapes with smooth surfaces. The mean particle size of PLLA/PLGA microparticles ranges from 1.76 to 2.15 μm, depending on the feeding ratio of PLLA to PLGA used in the SEDS process. The crystallinity of PLLA/PLGA microparticles decreases after the SEDS processing, so that the produced microparticles are in an amorphous state. Pure PLGA was hard to precipitate in small, fine microparticle form without the presence of PLLA. A model drug, paclitaxel, was encapsulated into PLLA/PLGA microparticles by the same SEDS process, and the in vitro release rate of paclitaxel from these PLLA/PLGA composites could be modulated by variation of the mixing ratio PLLA:PLGA. The prepared microparticles have negligible residual organic solvent. Drug-loaded PLLA/PLGA microparticles produced by SEDS have potential as an advanced colloidal suspension for pharmaceutical applications.PLLA and PLLA/PLGA microparticles with potential uses as drug carriers were prepared using solution-enhanced dispersion by supercritical fluids (SEDS).

Keywords: Supercritical CO; 2; Poly(; l; -lactic acid) (PLLA); Poly(lactide-; co; -glycolide) (PLGA); Microparticles; Drug carrier

Oxidative refolding of reduced, denatured lysozyme in AOT reverse micelles by Jun-Bao Fan; Jie Chen; Yi Liang (pp. 95-103).
The refolding kinetics of the reduced, denatured hen egg white lysozyme in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)–isooctane–water reverse micelles at different water-to-surfactant molar ratios has been investigated by fluorescence spectroscopy and UV spectroscopy. The oxidative refolding of the confined lysozyme is biphasic in AOT reverse micelles. When the water-to-surfactant molar ratio (ω0) is 12.6, the relative activity of encapsulated lysozyme after refolding for 24 h in AOT reverse micelles increases 46% compared with that in bulk water. Furthermore, aggregation of lysozyme at a higher concentration (0.2 mM) in AOT reverse micelles atω0 of 6.3 or 12.6 is not observed; in contrast, the oxidative refolding of lysozyme in bulk water must be at a lower protein concentration (5 μM) in order to avoid a serious aggregation of the protein. For comparison, we have also investigated the effect of AOT on lysozyme activity and found that the residual activity of lysozyme decreases with increasing the concentration of AOT from 1 to 5 mM. When AOT concentration is larger than 2 mM, lysozyme is almost completely inactivated by AOT and most of lysozyme activity is lost. Together, our data demonstrate that AOT reverse micelles with suitable water-to-surfactant molar ratios are favorable to the oxidative refolding of reduced, denatured lysozyme at a higher concentration, compared with bulk water.AOT reverse micelles with suitable water-to-surfactant molar ratios are favorable to the oxidative refolding of reduced, denatured hen egg white lysozyme at a higher concentration, compared with bulk water.

Keywords: Lysozyme; Protein refolding; Reverse micelles; Protein aggregation; Fluorescence spectroscopyAbbreviations; AOT; sodium bis(2-ethylhexyl)sulfosuccinate; CD; circular dichroism; GSH/GSSG; reduced and oxidized glutathione; NAG; N; -acetylglucosamine; NAM; N; -acetylmuramic acid; ω; 0; water-to-surfactant molar ratio; RDL; reduced, denatured lysozyme; RNase A; ribonuclease A

Nisin antimicrobial activity and structural characteristics at hydrophobic surfaces coated with the PEO–PPO–PEO triblock surfactant Pluronic® F108 by Yuan-Ching Tai; Joseph McGuire; Jennifer A. Neff (pp. 104-111).
The antimicrobial peptide nisin has been observed to preferentially locate at surfaces coated with the poly[ethylene oxide]–poly[propylene oxide]–poly[ethylene oxide] (PEO–PPO–PEO) surfactant Pluronic® F108, to an extent similar to its adsorption at uncoated, hydrophobic surfaces. In order to evaluate nisin function following its adsorption to surfaces presenting pendant PEO chains, the antimicrobial activity of nisin-loaded, F108-coated polystyrene microspheres and F108-coated polyurethane catheter segments was evaluated against the Gram-positive indicator strain, Pediococcus pentosaceus. The retained biological activity of these nisin-loaded layers was evaluated after incubation in the presence and absence of blood proteins, for contact periods up to one week. While an increase in serum protein concentration reduced the retained activity on both bare hydrophobic and F108-coated materials, F108-coated surfaces retained more antimicrobial activity than the uncoated surfaces. Circular dichroism spectroscopy experiments conducted with nisin in the presence of F108-coated and uncoated, silanized silica nanoparticles suggested that nisin experienced conformational rearrangement at a greater rate and to a greater extent on bare hydrophobic surfaces relative to F108-coated surfaces. These results support the notion that immobilized, pendant PEO chains confer some degree of conformational stability to nisin while also inhibiting its exchange by blood proteins.With this paper we begin to describe some of the structural and functional characteristics of the lantibiotic nisin at surfaces coated with pendant, PEO chains. The schematic illustrates nisin “entrapped” within a PEO–PPO–PEO triblock layer.

Keywords: PEO–PPO–PEO triblock surfactant; Pluronic; ®; F108; Lantibiotics; Nisin; Antimicrobial activity; Circular dichroism

Nisin adsorption to hydrophobic surfaces coated with the PEO–PPO–PEO triblock surfactant Pluronic® F108 by Yuan-Ching Tai; Pranav Joshi; Joseph McGuire; Jennifer A. Neff (pp. 112-118).
The adsorption and elution of the antimicrobial peptide nisin at hydrophobic, silanized silica surfaces coated with the poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) surfactant Pluronic® F108 were measured in situ, with ellipsometry. While such layers are known to inhibit protein adsorption, nisin was observed to adsorb in multilayer quantities, to an extent similar to its adsorption at uncoated, hydrophobic surfaces. The rates of nisin adsorption and elution were generally slower at F108-coated surfaces. And, the sequential adsorption of nisin, including two adsorption–elution cycles at each surface, showed greater differences in adsorption rates between the first and second adsorption cycles, when evaluated at identical mass density, for uncoated relative to F108-coated surfaces. These results indicate that nisin adsorption occurs via “entrapment” within the PEO brush layer at F108-coated surfaces, in this way slowing adsorption and spontaneous elution, and inhibiting post-adsorptive molecular rearrangements by reducing the lateral mobility of nisin. While F108-coated layers rejected adsorption of serum albumin, sequential adsorption experiments carried out with nisin and albumin showed a low level of albumin adsorption when nisin was present at the interface.This paper describes adsorption and elution behavior of the lantibiotic nisin at surfaces coated with pendant, PEO chains. The schematic illustrates nisin “entrapment” in a PEO–PPO–PEO triblock layer.

Keywords: Nisin adsorption kinetics; In situ; ellipsometry; Pluronic; ®; F108; PEO–PPO–PEO triblock surfactants

Mechanism for stabilization of the molten globule state of papain by sodium n-alkyl sulfates: Spectroscopic and calorimetric approaches by J. Chamani; M. Heshmati (pp. 119-127).
Papain exists in a molten globule (MG) state at pH 2 and in this state protein tends to aggregate in the presence of lower concentrations of guanidine hydrochloride (GuHCl). Such aggregation is prevented if low concentrations of sodium n-alkyl sulfates are also present in the buffer; in addition, stabilization of the protein is also induced. The guanidine hydrochloride and temperature-induced unfolding of papain, in the presence of n-alkyl sulfates, indicate stabilization of the protein as seen from the higher transition midpoints when monitored by fluorescence, circular dichroism, and differential scanning calorimetry. However, a similar phenomenon is not seen under neutral conditions in the presence of n-alkyl sulfate concentrations. The effect of n-alkyl sulfates on the structure of the MG state of papain was utilized to investigate the contribution of hydrophobic interaction to the stability of the MG state. TheTd values of the MG states of papain in the presence of n-alkyl sulfates at different concentrations showed substantial variation. The enhancement ofTd values at the stability criterion of MG states corresponded with increasing chain length of the cited n-alkyl sulfates. The present results suggest that the hydrophobic interactions play important roles in stabilizing and preventing the aggregation of the MG state of papain.Thermal unfolding of papain at pH 2 in the presence of 1.5 mM SOS (○); 0.8 mM SDeS (●); 0.18 mM SDS (◊); 0.07 mM STS (♦).

Keywords: Papain; Molten globule state; Aggregation; Sodium; n; -alkyl sulfates; Stabilization; Hydrophobic interactions

Temperature tunability of size in CdS nanoparticles and size dependent photocatalytic degradation of nitroaromatics by A. Datta; A. Priyam; S.N. Bhattacharyya; K.K. Mukherjea; A. Saha (pp. 128-135).
Size tunability of thiophenol capped CdS nanoparticles (NPs) has been achieved by controlling the temperatures in situ. Synthesis at 5 °C produced stable particles of smallest size having narrow size distribution and high photoluminescence quantum yield. The photoluminescence of thiophenol capped CdS NPs was quenched by the nitroaromatic compounds. The Stern–Volmer constant of dinitrobenzene was about 15-fold higher than nitrobenzene, which indicates that introduction of nitro groups in the benzene ring increases the quenching efficiency. Further, the as-prepared CdS NPs were found to display size dependent photocatalytic activity towards degradation of nitroaromatics. The catalytic efficiency of CdS quantum particles was quintupled with decrease in particle size from 5.8 to 3.8 nm. An empirical equation has been derived to correlate the catalytic efficiency of the nanoparticles with the twin factors operating in the quantum confinement regime: (i) change in surface to volume ratio and (ii) shift in conduction band edge.Empirical equation correlating catalytic efficiency of the quantum confined nanoparticles with the twin factors: (1) surface to volume ratio and (2) shift in conduction band edge.

Keywords: Nanoparticles; Photoluminescence; Nitroaromatics; Quantum yield; Photocatalysis; Quantum size effects

Preparation and optical properties of worm-like gold nanorods by Haowen Huang; Chaocai He; Yunlong Zeng; Xiaodong Xia; Xianyong Yu; Pinggui Yi; Zhong Chen (pp. 136-142).
A type of worm-like nanorods was successfully synthesized through conventional gold nanorods reacting with Na2S2O3 or Na2S. The generated worm-like gold nanorods comprise shrunk nanorod cores and enwrapped shells. Therefore, a gold–gold sulfide core–shell structure is formed in the process, distinguishing from their original counterparts. The formation of the gold chalcogenide layers was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. Experimental results showed that the thickness of the gold chalcogenide layers is controllable. Since the increase of shell thickness and decrease of gold nanorod core take place simultaneously, it allows one to tune the plasmon resonance of nanorods. Proper adjustment of reaction time, temperature, additives and other experimental conditions will produce worm-like gold nanorods demonstrating desired longitudinal plasmon wavelength (LPW) with narrow size distributions, only limited by properties of starting original gold nanorods. The approach presented herein is capable of selectively changing LPW of the gold nanorods. Additionally, the formed worm-like nanorods possess higher sensitive property in localized surface plasmon resonance than the original nanorods. Their special properties were characterized by spectroscopic methods such as Vis–NIR, fluorescence and resonance light scattering. These features imply that the gold nanorods have potential applications in biomolecular recognition study and biosensor fabrications.Worm-like gold nanorods (b) can be produced from the as-synthesized nanorods (a) reacting with Na2S2O3. An approach capable of continuously increasing longitudinal plasmon wavelength of new gold nanorods is developed.

Keywords: Aspect ratio; Worm-like gold nanorods; Localized surface plasmon resonance; Longitudinal plasmon wavelength

A fluorescent magnetic nanoalloy—Lanthanon-doped FePt:RE by Ming Wen; Wengang Zhao; Tao Zhang; Y.Z. YuanZheng Zhu; Y.F. YaFen Wang; Qingsheng Wu (pp. 143-151).
Employing dibenzo-24-crown-8-ether (DB24C8) as a phase-transfer catalyst, monodispersed fluorescent lanthanon-doped magnetic FePt:RE (RE=Eu, Dy, and Ce) nanoparticles about 3 nm in size were synthesized through the reduction of H2PtCl6⋅6H2O, Fe2(C2O4)3⋅5H2O, and RE(NO3)3 (RE=Eu, Dy, and Ce) by propylene glycol using oleic acid as the stabilizer in the solvent-thermal system. The conversion of the as-synthesized chemically disordered fcc FePt:RE nanoparticles to a chemically ordered L10 structure occurred after annealing treatment at 873 K, and was simultaneously accompanied by a coercivity increase. It is interesting that the amorphous formation trend is strengthened in an europium-doped FePt:Eu alloy accompanied by enhancement of the coercive force. Its thermal stability indicated that the addition of europium can inhibit the phase transformation. Moreover, the optical measurement results proved that FePt:Dy alloy nanoparticles have fluorescent properties.The new fluorescent lanthanon-doped magnetic FePt:RE nanoparticles with sizes of 3 nm were synthesized in a solvent-thermal system. Eu, Dy, and Ce doped in FePt led to the fluorescence properties.

Keywords: FePt:RE nanoparticles; Monodispersed; Phase-transfer catalysis; Fluorescence; Magnetic

Seedless synthesis of octahedral gold nanoparticles in condensed surfactant phase by Cuong Cao; Sungho Park; Sang Jun Sim (pp. 152-157).
We report a seedless synthetic method of gold octahedral nanoparticles in an aqueous phase. Eight facets with {111} crystalline structures of octahedral nanoparticles could be formed in an aqueous medium when the gold salt was reduced by ascorbic acid at room temperature in the presence of cetyltrimethylammonium bromide as a shape-inducing agent, and hydrogen peroxide as a reaction promoter. The growth kinetics and surface crystalline structures were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy.Au octahedra could be perfectly formed in an aqueous solution when the CTAB-templated Au ions were reduced by AA in the presence of H2O2 as a reaction promoter.

Keywords: Template-directed synthesis; Non-seeding process; H; 2; O; 2; -dependent growth; Octahedra; Gold nanoparticles

Aluminum hydroxide microstructural units in gelled media aged, or nonaged, with alcohol and water by Dario T. Beruto; Rodolfo Botter; Attilio Converti (pp. 158-167).
Aluminum hydroxide gelled media dispersed and then aged in alcohol (ES) or in water (WS) were prepared with a solid phase concentration equal to 0.45% v/v. The media were characterized through rheological measurements and detailed analysis. Xerogels were obtained through a designed drying process at 8 °C under vacuum for 24 h, followed by a heating treatment at 105 °C and a pressure of 10−3 Pa for 2 h. The xerogel microstructure was carefully investigated using N2 adsorption–desorption methods at 78 K. Rheology data on ES and WS colloidal dispersions were compared with data computed from adsorption isotherms of corresponding xerogels, in order to infer information about particles organization in the dispersions. On this ground, a model for microstructural units dispersed in the liquid phase has been derived. The beneficial action of alcohol in giving xerogel powders with higher specific surface area and higher porosity has been explained on the basis that alcohol produces changes in the corresponding dispersed microstructural units. The effect of the aging time in alcohol and in water was evaluated, and the evolution of all microstructural parameters was described.The sizes of liquid dispersed crystallites and clusters of Al(OH)3 have been derived from the corresponding xerogel microstructure. The observed effects of alcohol, which is shown to increase surface area and porosity of the xerogels, have been explained.

Keywords: Aluminum hydroxide; Gel media; Xerogel; Drying; Rheology; Microstructural units

The terminal rise velocity of 10–100 μm diameter bubbles in water by Luke Parkinson; Rossen Sedev; Daniel Fornasiero; John Ralston (pp. 168-172).
Single bubbles of very pure N2, He, air and CO2 were formed in a quiescent environment in ultra-clean water, with diameters ranging from 10 to 100 μm. Their terminal rise velocities were measured by high-speed video microscopy. For N2, He and air, excellent agreement with the Hadamard–Rybczynski (H–R) equation was observed, indicating that slip was occurring at the liquid–vapor interface. For CO2 bubbles with diameters less than 60 μm, the terminal rise velocities exceeded those predicted by the H–R equation. This effect was ascribed to the enhanced solubility of CO2 compared with the other gases examined. The presence of a diffusion boundary layer may be responsible for the increased terminal velocity of very small CO2 bubbles.The rise velocity of air, N2, He, and CO2 bubbles in pure water are compared with Stokes' law (—) and Hadamard–Rybczynski (- - -) predictions. A mobile bubble surface is implied.

Keywords: Bubble rise; Slip; Gas diffusion; Terminal velocity

One-step synthesis and functionalization of hydroxyl-decorated magnetite nanoparticles by Sara Mondini; Simone Cenedese; Giorgio Marinoni; Giorgio Molteni; Nadia Santo; Claudia L. Bianchi; Alessandro Ponti (pp. 173-179).
Magnetite nanoparticles covered by a layer of ω-hydroxycarboxylic acid were synthesized in one step by high-temperature decomposition of iron(III) ω-hydroxycarboxylates in tri- and tetra-ethylene glycol. The nanoparticles were characterized by TEM, XRD, IR, XPS and NMR techniques in order to show that they comprise a crystalline magnetite core and actually bear on the outer surface terminal hydroxy groups. The latter ones are convenient “handles” for further functionalization as opposed to the chemically-inert aliphatic chains which cover conventionally synthesized nanoparticles. This was shown by several examples in which the hydroxy groups on the nanoparticle surface were easily transformed in other functional groups or reacted with other molecules. For instance, the hydroxyl-decorated nanoparticles were made water soluble by esterification with a PEGylated acetic acid. The reactive behavior of the surfactant monolayer was monitored by degrading the nanoparticles with aqueous acid and isolating the surfactant for NMR characterization. In general, the reactivity of the terminal hydroxyl groups on the nanoparticle surface parallels that observed in the free surfactants. The reported hydroxyl-decorated magnetite nanoparticles can be thus considered as pro-functional nanoparticles, i.e., a convenient starting material to functionalized magnetic nanoparticles.Conventional nanoparticles have a sluggish complexion since they interact with the environment by unflappable aliphatic chains. We managed to synthesize spirited magnetic nanoparticles which display alcoholic groups at the outer surface. These hydroxyl-decorated magnetite nanoparticles are a convenient starting material for further functionalization thanks to the synthetic flexibility of the hydroxyl group.

Keywords: Magnetic nanoparticles; ω; -Hydroxycarboxylic acid; Iron hydroxycarboxylate; Iron oxide; Pro-functional nanoparticles

Sedimentation of concentrated monodisperse colloidal suspensions: Role of collective particle interaction forces by Jan S. Vesaratchanon; Alex Nikolov; Darsh T. Wasan (pp. 180-189).
The sedimentation velocities and concentration profiles of low-charge, monodisperse hydroxylate latex particle suspensions were investigated experimentally as a function of the particle concentration to study the effects of the collective particle interactions on suspension stability. We used the Kossel diffraction technique to measure the particle concentration profile and sedimentation rate. We conducted the sedimentation experiments using three different particle sizes. Collective hydrodynamic interactions dominate the particle–particle interactions at particle concentrations up to 6.5 vol%. However, at higher particle concentrations, additional collective particle–particle interactions resulting from the self-depletion attraction cause particle aggregation inside the suspension. The collective particle–particle interaction forces play a much more important role when relatively small particles (500 nm in diameter or less) are used. We developed a theoretical model based on the statistical particle dynamics simulation method to examine the role of the collective particle interactions in concentrated suspensions in the colloidal microstructure formation and sedimentation rates. The theoretical results agree with the experimentally-measured values of the settling velocities and concentration profiles.The sedimentation velocities and concentration profiles of low-charge, monodisperse hydroxylate latex particle suspensions were investigated experimentally as a function of the particle concentration to study the effects of the collective particle interactions on suspension stability.

Keywords: Collective interactions; Sedimentation; Depletion; Colloidal particles; Hard sphere

Laponite-supported titania photocatalysts by Lisa M. Daniel; Ray L. Frost; Huai Yong Zhu (pp. 190-195).
This study builds on previous results published on the synthesis and characterization of laponite-supported titania photocatalysts. Titania nanocrystals are prepared prior to addition to the clay dispersion, by a sol–gel synthesis incorporating a microwave hydrothermal step. In addition to previously examinations with XRD, TEM, and FT-IR, the samples are further characterized with SEM,29Si NMR, and BET N2 sorption to gain additional insight into the effect of TiO2 concentration and surface area on the photoactivity of the samples.Titania nanocrystals prepared prior to addition to the laponite clay dispersion, by a sol–gel synthesis incorporating a microwave hydrothermal step were characterized with SEM,29Si NMR, and BET N2 sorption to gain additional insight into the effect of TiO2 concentration and surface area on the photoactivity of the samples.

Keywords: Titania; Photocatalyst; Laponite; Colloid; Surfactant; Hydrothermal treatment

Palladium supported on structured and nonstructured carbon: A consideration of Pd particle size and the nature of reactive hydrogen by Claudia Amorim; Mark A. Keane (pp. 196-208).
This study sets out a comprehensive characterization of bulk Pd and Pd (ca. 8% w/w) supported on activated carbon (AC), graphite and graphitic nanofibers (GNF). Catalyst activation has been examined by temperature programmed reduction (TPR) analysis and the activated catalysts analyzed in terms of BET area, TEM, H2 chemisorption/TPD, and XRD measurements. While H2 chemisorption and TEM delivered the same sequence of increasing (surface area weighted) average Pd particle sizes, a significant difference (by up to a factor of 3) in the values obtained from both techniques has been recorded and is attributed to an unwarranted (but widely adopted) assumption of an exclusive H2/Pd adsorptionstoichiometry=1/2. It is demonstrated that TEM analysis provides a valid mean particle size once it is established that the associated standard deviation is small and insensitive to additional particle counting. XRD line broadening yielded an essentially equivalent Pd size (20–25 nm) for each supported catalyst. The nature of the hydrogen associated with the supported catalysts has been probed and is shown to comprise of chemisorbed (on Pd), spillover (on the carbon support), and hydride (associated with Pd) species. Physical mixtures of bulk Pd + support (AC, graphite, and GNF) were also considered in order to assess hydrogen spillover by H2 TPD analysis. Generation of spillover hydrogen at room temperature is established where temperatures in excess of 740 K are required for effective desorption from the supported Pd catalysts, i.e., 280 K higher than that required for the desorption of chemisorbed hydrogen. Pd hydride formation (at room temperature) is shown to be reversible with decomposition occurring at ca. 380 K. Taking the hydrodechlorination of chlorobenzene as a test reaction, the capability of Pd hydride to promote a hydrogen scission of C–Cl in the absence of an external supply of H2 is demonstrated with a consequent consumption of the hydride. This catalytic response was entirely recoverable once the Pd hydride was replenished during a subsequent reactivation step.Pd particle size distribution on activated carbon, graphite and graphitic nanofibers (see figure) and the nature of the hydrogen (chemisorbed, spillover, and Pd hydride) associated with these samples have been established; the capability of supported Pd hydride to promote C–Cl bond hydrogen scission in the absence of an external supply of H2 is demonstrated.

Keywords: Supported Pd; Bulk Pd; Palladium hydride; Spillover hydrogen; Activated carbon; Graphite; Carbon nanofibers; Hydrodechlorination

Nanoporosities and catalytic activities of Pd-tailored single wall carbon nanohorns by Tsutomu Itoh; Koki Urita; Elena Bekyarova; Miki Arai; Masako Yudasaka; Sumio Iijima; Tomonori Ohba; Katsumi Kaneko; Hirofumi Kanoh (pp. 209-214).
The nanoporosities and catalytic activities of Pd nanoparticles dispersed on single wall carbon nanohorns (Pd-SWCNHs) and oxidized single wall carbon nanohorns (Pd-ox-SWCNHs) were examined. A transmission electron microscopy (TEM) observation indicated that Pd nanoparticles of 2–3 nm size were highly dispersed on both the SWCNHs. X-ray photoelectron spectra and N2 adsorption isotherms at 77 K illustrated the differences in the deposition process mechanisms of the Pd-SWCNHs and Pd-ox-SWCNHs; the deposition process depended on the surface functional groups. The supercritical H2 adsorption isotherms at 77 K suggested the relationships between the interaction of Pd-SWCNHs and Pd-ox-SWCNHs with H2 and the catalytic activities for a water formation reaction in a gas phase at 273 or 298 K. The catalytic activity measurement and TEM observation of the catalysts after the reactions demonstrated that the Pd-SWCNHs and Pd-ox-SWCNHs are promising catalysts.The dispersed states, surface properties, nanoporosities, and catalytic activities of Pd-nanoparticle-tailored single wall carbon nanohorns (Pd-SWCNHs) and oxidized single wall carbon nanohorns (Pd-ox-SWCNHs) were examined.

Keywords: Single wall carbon nanohorn; Palladium; Adsorption; Heterogeneous catalysis; Gas-phase reactions; Hydrogen

Effect of magnesium/calcium ratios in solutions treated by electrodialysis: Morphological characterization and identification of anion-exchange membrane fouling by Christophe Casademont; Gérald Pourcelly; Laurent Bazinet (pp. 215-223).
The present study aimed the characterization of the fouling formed on anion-exchange membrane during electrodialysis treatment of model salt solutions at different Mg/Ca ratio (0, 1/20, 1/10, 1/5 and 2/5). The membrane fouling was characterized by membrane parameters (membrane thickness and electrical conductivity) and identified by membrane surface analysis (elemental analysis and X-ray diffraction). The mineral deposit was identified as Ca(OH)2 when no magnesium was present in the model salt. As soon as magnesium was present in the model salt solution for neutral pH(concentrate) conditions a mix between CaCO3 and Ca(OH)2 was formed. This study is the first one to report the influence of magnesium in solution on the formation of CaCO3 fouling at the interface of anion-exchange membrane during electrodialysis.The aim of this study was to determine the influence of magnesium on anion-exchange membrane (AEM) fouling during electrodialysis of solutions at different Mg/Ca ratios. It appeared that the formation of calcite on AEM was linked to the presence of Mg.

Keywords: Electrodialysis; Anion-exchange membrane; Fouling; Calcium; Magnesium

Optimization of instantaneous solvent exchange/surface modification process for ambient synthesis of monolithic silica aerogels by Sung-Woo Hwang; Tae-Youn Kim; Sang-Hoon Hyun (pp. 224-230).
The instantaneous solvent exchange/surface modification (ISE/SM) process for the ambient synthesis of crack-free silica aerogel monoliths with a high production yield was optimized. Monolithic forms of silica wet gels were obtained from aqueous colloidal silica sols prepared via the ion exchange of sodium silicate solutions. Crack-free silica aerogel monoliths were synthesized via an ISE/SM process using isopropyl alcohol/trimethylchlorosilane as a modification agent and n-hexane as a main solvent, followed by ambient drying. The optimum process conditions of the ISE/SM process were investigated by clarifying the reaction mechanism and phenomena. Most effective ranges of process variables on the ISE/SM stage were determined as 0.2500–0.3567 of TMCS/H2O (pore water) in molar ratio and 15–30 of n-hexane/TMCS in volumetric ratio, with a reaction temperature below 283 K. Crack-free silica aerogel monoliths synthesized via these conditions had a well-developed mesoporous structure and excellent properties (bulk density of 0.12–0.14 g/cm3, specific surface area of 724 m2/g), and a high yield (nearly 80%).The effective synthetic conditions for crack-free silica aerogel monoliths via the ISE/SM process and ambient drying were successfully optimized.

Keywords: Sol–gel process; Silica colloid; Silica aerogel; Solvent exchange; Surface modification; Ambient drying; Monolith

Incorporation of disodium alkyl polyoxyethylene ether sulfosuccinate inside styrene droplets: Mechanism and its application for preparation of multihollow polymer spheres by Linyong Song; Yuanhua Cong; Mozhen Wang; Xuewu Ge; Zhicheng Zhang (pp. 231-236).
Emulsion polymerization of styrene was carried out using two kinds of alkyl polyoxyethylene ether sulfosuccinates as surfactant: disodium cetyl polyoxyethylene (25) ether sulfosuccinate (CPS) and octyl-phenol polyoxyethylene (10) ether sulfosuccinate (OPS). In experiments, the incorporation of CPS or OPS inside styrene droplets and polystyrene particles was clearly observed. Based on this phenomenon, multihollow polymer spheres are prepared in a one-step reaction and this strongly supports the proposed incorporation mechanism. CPS is more effective than OPS during the preparation of multiporous spheres. This difference between the two surfactants mainly contributes to the difference of the length of the EO (polyoxyethylene) group, which can determine the affinity among surfactant, styrene, and water molecules.By the incorporation of disodium cetyl polyoxyethylene (25) ether sulfosuccinate inside styrene droplets, multihollow polymer spheres were prepared in a one-step reaction and this strongly supports the proposed incorporation mechanism.

Keywords: Incorporation; Polyoxyethylene; γ; -Ray radiation; Multihollow sphere; Emulsion polymerization

Decarbonation of MgAl-LDHs (layered double hydroxides) using acetate–buffer/NaCl mixed solution by Nobuo Iyi; Takayoshi Sasaki (pp. 237-245).
By using acetate–buffer (sodium acetate and acetic acid)/NaCl mixed solutions, the deintercalation of carbonate ions (CO2−3) was conducted on MgAl-LDHs at different Mg/Al ratios—LDH2 (LDH with Mg/Al≈2) and LDH3 (LDH with Mg/Al≈3). When only an acetate–buffer solution was used, decarbonation did not take place even if the buffer solution was made acidic enough to dissolve LDH itself; however, the addition of NaCl to the buffer solution caused deintercalation of the carbonate ions from the MgAl-LDHs and the reaction was conducted without any morphological and weight change at 25 °C. Under the optimum conditions, full decarbonation was attained for the two MgAl-LDHs in minutes, and the obtained LDHs contained Cl in the interlayer space without incorporation of any acetate anions due to their extremely low anion selectivity of acetate ion. The allowable range for the concentration of the decarbonation solution is wide, and the change in pH due to the decarbonation reaction is slight because of the buffering effect. The decarbonation was affected by the Mg/Al ratio of the LDH; i.e., the present LDH2 was slightly more difficult to decarbonate than LDH3, probably due to the higher layer-charge density of LDH2.

Keywords: LDH; Layered double hydroxide; Hydrotalcite; Anionic clay; Decarbonation; Carbon dioxide; Buffer; Acetate

Self-pinning protein-laden drops by Viatcheslav V. Berejnov (pp. 246-251).
Proteins dissolved in a drop induce and enhance the pinning of the drop contact line. This effect dramatically increases the volume of drops that are vertically pinned on a flat siliconized substrate. It was found that this drop pinning behavior exhibits two regimes: for low protein content in a drop the pinning increases as the contact angle hysteresis increases, and for high protein content the pinning decreases as the surface tension of the protein solution decreases.Proteins dissolved in a drop induce the pinning of a drop contact line. This effect dramatically increases the volumes of vertically pinned drops.

Keywords: Drop; Contact line pinning; Proteins; Lysozyme

Theory and experiment for soap-film bridge in an electric field by Derek E. Moulton; John A. Pelesko (pp. 252-262).
Surface tension and electrostatic forces dominate the behavior of many micro and nano scale systems. Understanding interactions between these forces may therefore be of great utility in a number of engineering systems. We investigate one such interaction by subjecting an elastic membrane suspended between two parallel rings to an axially symmetric electric field. A model is formulated and analyzed and the effect of the field is characterized. Experimentally, the system is investigated using a soap-film bridge and a high voltage power source. Experimental observations verify the validity of the theory, in predicting both membrane profile as well as critical device length at which stability is lost.A soap-film membrane is suspended between two rings with a conducting rod placed on the radial axis. An applied potential difference induces competition between surface tension and electrostatic forces.

Keywords: Minimal surface; Mean curvature; Capillary surface; Electrostatics; MEMS; Microelectromechanical systems; Self-assembly

Interfacial properties of Pluronics and the interactions between Pluronics and cholesterol/DPPC mixed monolayers by Lin-Chau Chang; Yao-Yu Chang; Churn-Shiouh Gau (pp. 263-273).
Pluronics are triblock copolymers of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) with wide range of hydrophilic–lipophilic balance. In order to investigate the relationship between the chemical structures of Pluronics and the interfacial properties at the air–water interface by monolayer techniques, Pluronics L61, P65, F68, P84, P123, L35, and P105 were selected. Since cholesterol influenced substantially the molecular packing stage and the characteristics of cell membranes, the interactions between Pluronics and model cell membranes in the absence and presence of cholesterol were compared. The results ofπ–A isotherms and surface elasticities of Pluronic monolayers indicated that the first and second transition like stage were mainly affected by the numbers of EO and PO monomers, respectively. Pluronics with higher hydrophobicities demonstrated larger surface activities and penetration abilities to dipalmitoylphosphatidylcholine (DPPC) monolayers, which might be due to hydrophobic interactions and van der Waals forces. In the presence of cholesterol, hydrogen bonding effects was supposed to exist between the 3 β-hydroxy group of cholesterol and ether oxygen of PEO chains, which led Pluronic F68, with the longest PEO chain herein, to exhibit significantly higher penetration ability. Our findings proposed a theoretical basis for selection of optimized drug carriers and the starting point for further investigations.

Keywords: Pluronics; Cholesterol; Monolayer technique; Cell membrane; Hydrophobicity

Interaction of anionic dyes and cationic surfactants with ionic liquid character by A. Safavi; H. Abdollahi; N. Maleki; S. Zeinali (pp. 274-280).
The interactions of an imidazolium based ionic liquid (IL), namely 1-dodecyl-3-methylimidazolium chloride [C12mim][Cl] with two sulfonated anionic dyes, azocarmine G and methyl orange, are studied spectrophotometrically in both acidic and basic media. ILs (with some surface active character) can interact with the above dyes and cause considerable shifts in their spectra. These interactions are then compared with some surfactant–dye interactions. Evolving factor analysis (EFA) and multivariate curve resolution-alternating least squares (MCR-ALS) are used for complete resolution of the measured spectrophotometric data. The concentration and spectral profiles of all species were calculated without any assumption of the chemical models. The spectral variation of dye solutions as a function of IL concentrations below and above the critical aggregation concentration (CAC) is analyzed using MCR-ALS as a soft-modeling technique. The ion pair formation constants between ILs and dyes were calculated using the obtained concentration profiles.Addition of an ionic liquid-like surfactant ([C12mim][Cl]) to methyl orange (pH 7) shows formation of dye–IL complexes at submicellar concentrations and dye–aggregate complexes at and above the critical aggregation concentration.

Keywords: Ionic liquids–dye interaction; Surfactant; Multivariate curve resolution

Side-chain-controlled H- and J-aggregation of amphiphilic porphyrins in CTAB micelles by Lin Guo (pp. 281-286).
The aggregation behavior of a series of amphiphilic 4-hydroxyphenyl porphyrins with one (P1), two (P2) and three (P3) hexadecyl side chains in cetyltrimethylammonium bromide (CTAB) micelles has been studied by means of UV–vis and fluorescence spectra. It was found that the number of hexadecyl side chains not only controls the H- and J-aggregation of the porphyrins in CTAB micelles, but also influences the aggregation concentration and tendency. With increasing porphyrin concentration,P1 andP2 form H-aggregates in CTAB micelles, whileP3 forms J-aggregates. Porphyrins with more hexadecyl side chains tend to form aggregates more easily and at lower concentrations in CTAB micellar solutions.With increasing porphyrin concentration,P1 andP2 form H-aggregates in CTAB micelles, whileP3 forms J-aggregates.

Keywords: Porphyrin; Amphiphilic; CTAB; Micelle; Aggregation

Nonideal mixing of alkylammonium chloride and decyldimethylphosphine oxide surfactants in adsorbed films and micelles by Hidemi Iyota; Koji Abe; Norihiro Ikeda; Kinsi Motomura; Makoto Aratono (pp. 287-293).
Miscibility and interaction of decyldimethylphosphine oxide (DePO) with ammonium chloride (AC), hexylammonium chloride (HAC), and dodecylammonium chloride (DAC) in adsorbed films and micelles were studied by surface tension measurements. Phase diagrams were drawn for the mixed adsorption, mixed micelle formation, and equilibrium between adsorbed films and micelles. Nonideal mixing of DAC and DePO was characterized by a negative excess Gibbs free energy and positive excess area of adsorption and negative excess Gibbs free energy of micelle formation. It is concluded that the interaction between DAC and DePO in adsorbed films and micelles is larger than those between the same surfactants alone due to two factors: ion–dipole interactions between the head groups of DAC and DePO and alkyl-chain/alkyl-chain interactions.The interaction between dodecylammonium chloride (DAC) and decyldimethylphosphine oxide (DePO) in adsorbed films and micelles is enhanced compared to the pure surfactants, due to ion–dipole interaction between DAC and DePO head groups.

Keywords: Nonideal mixing; Mixture of ionic and nonionic surfactants; Adsorbed film and micelle; Activity coefficient; Phase diagram and excess function; Surface tension

The partitioning of emulsifiers in o/w emulsions: A comparative study of SANS, ultrafiltration and dialysis by Kathleen Oehlke; Vasil M. Garamus; Anja Heins; Heiko Stöckmann; Karin Schwarz (pp. 294-303).
The partitioning of SDS and CTAB in o/w emulsions was investigated by ultrafiltration (UF), dialysis and small-angle neutron scattering (SANS). It was possible to measure the monomeric and the micellar concentrations of the emulsifiers in the filtrate and permeate in the UF and dialysis experiments, respectively. In addition, the interfacial concentration was calculated as the difference to the initial concentration. SANS experiments provided data, from which the micellar concentrations were obtained, followed by the calculation of the interfacial concentrations. The three methods were compared on the basis of the area, which is occupied by each emulsifier molecule at the interface. Good agreement was shown for both emulsifiers studied. Micellation started at total emulsifier concentrations of approx. 10 mM in emulsions containing either CTAB or SDS. At saturation (>10 mM SDS in a 10% o/w emulsion), the area per SDS headgroup at the interface was between 48 and 64 Å2, depending on the method. In emulsions with CTAB, saturation of the interface was not achieved. The minimum headgroup area was determined by UF to be 33 Å2 at a concentration of 30 mM CTAB in a 10% o/w emulsion.Partitioning of SDS in a 10% o/w emulsion determined by ultrafiltration.

Keywords: Emulsion; SANS; Ultrafiltration; Dialysis; Partitioning; Micelles

Physico-chemical investigation of asymmetrical peptidolipidyl-cyclodextrins by Angelina Angelova; Christophe Fajolles; Céline Hocquelet; Florence Djedaïni-Pilard; Sylviane Lesieur; Véronique Bonnet; Bruno Perly; Geneviève Lebas; Laurent Mauclaire (pp. 304-314).
A new class of amphiphilic peptidolipidyl-cyclodextrins is reported. The derivatives are chiral due to the presence of an L-leucine in the spacer arm that links a saccharide moiety and a grafted, saturated hydrocarbon chain. Self-assembly properties of the peptidolipidyl-cyclodextrins are characterized by quasi-elastic light scattering, turbidity and UV–visible absorption measurements. NMR experiments give insight into the intermolecular dipolar interactions as a function of temperature and concentration. N-dodecyl-Nα-(6I-amidosuccinyl-61-deoxy-cyclomaltoheptaose)- L-leucine (1) is poorly soluble in aqueous media. N-dodecyl-Nα-(6I-amidosuccinyl-6I-deoxy-2I,3I-di- O-methyl-hexakis-(2II-VII,3II-VII,6II-VII-tri- O-methyl)-cyclomaltoheptaose)- L-leucine (2) is found to be more soluble and self-assembles into stable supramolecular colloidal aggregates with nanometric dimensions above a critical aggregation concentration (CAC). It has a propensity for solubilization of hydrophobic species revealing a micellar-like behavior, which is compared to that of the non-ionic detergent octyl glucoside. On the contrary, compound1 precipitates in a crystalline phase beyond its water solubility limit, and it does not display any solubilizing capacity. The observed behavior corroborates at the molecular level with the NMR results.Physico-chemical characterization of the intermolecular interactions and aggregation behavior in aqueous phase resulting from the chemical structure of the compounds (1 and2) and the propensity of their aggregates to solubilize hydrophobic molecules.

Keywords: Amphiphile; β; -Cyclodextrin; Micelle; Aggregate; Lyotropic behavior

Diffusion of latex and DNA chains in 2D confined media by Jérôme Mathé; Jean-Marc Di Meglio; Bernard Tinland (pp. 315-320).
We report a study on the dynamics of latex polystyrene beads and of DNA molecules confined in two dimensions, using fluorescence video-microscopy. We particularly focus on the character of the confined objects (hard or soft) and on the nature of the confinement: liquid (in a soap film) or solid (between two glass plates). For weak confinements, whatever the nature of confinement, we observe that DNA molecules and latex beads behave very similarly: the tighter the confinement, the slower the diffusion with a good agreement with theory. For strong confinements between solid walls (thickness of confinement smaller than the bulk radius of gyration), DNA coils are not immobilized and still diffuse. We show in this case that the conformation of DNA chains is in good agreement with the predictions of De Gennes and Brochard (radius∼e−1/4, with e the confinement gap); on the other hand, we cannot really check the theoretical predictions for the diffusion coefficient. Interestingly, strong confinement of latex beads in a soap film leads to a anomalous slow diffusion, certainly associated with an additional viscous drag generated by the interfaces.

Keywords: Brownian diffusion; Steric confinement; Bidimensional; DNA; Colloids

Fabrication of silica nanotubes using silica coated multi-walled carbon nanotubes as the template by Myunghun Kim; Jinho Hong; Jeongwoo Lee; Chang Kook Hong; Sang Eun Shim (pp. 321-326).
Silica nanotubes were synthesized using the multi-walled carbon nanotubes (MWCNTs) as the template material. First, we prepared silica coated MWCNT composites by surface oxidation of MWCNTs using KMnO4 in the presence of a phase transfer catalyst and followed by grafting of 2-aminoethyl 3-aminopropyl trimethoxy silane, AEAPS. The amine groups in grafted AEAPS on MWCNTs could activate the silica shell formation by acid–base interaction. The synthesized silica was formed a uniform layer on MWCNTs with a controllable thickness and possessed sturdy 3-dimensional stability. After calcinations at 800 °C, the inner MWCNTs of the composite were completely decomposed and the outer silica shell layer maintained without distortion of its original shape. Finally, we could obtain the silica nanotubes having 13.0 nm of average layer thickness.Synthesized silica nanotubes by three step reactions: oxidation of MWCNTs, grafting with a silane coupling agent, and silica coating by TEOS.

Keywords: Carbon nanotube; Silica; Surface modification; Nanotube; Encapsulation

Morphology-controlled fabrication of polygonal ZnO nanobowls templated from spherical polymeric nanowell arrays by Y.F. Yanfang Wang; J.H. Junhu Zhang; X.L. Xiaolu Chen; Xiao Li; Z.Q. Zhiqiang Sun; Kai Zhang; D.Y. Dayang Wang; Bai Yang (pp. 327-332).
We report a facile and effective strategy for synthesizing morphology-controlled patterned ZnO nanostructures. Polymeric nanowell arrays were employed as scaffold templates, followed by solution dipping and calcination process, polygonal ZnO nanobowl structures were fabricated on silicon substrate. The ordered polymeric nanowell arrays not only provided confined areas for depositing desired materials, but also induced shape transition of ZnO nanobowls from circular to polygonal. The morphology of the patterned ZnO nanostructures can be easily controlled by tuning parameters of polymeric nanowell arrays and other treatment conditions. The patterned structures were characterized by field emission scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA).A template-assisted synthesis strategy for fabrication of polygonal ZnO nanobowl structures was reported. Morphology-controlled ZnO structures can be obtained by tuning the parameters of the template and treatment conditions.

Keywords: Polygonal; ZnO; Nanobowls; Template; Polymeric nanowell

Glucosamine-carrying temperature- and pH-sensitive microgels: Preparation, characterization, and in vitro drug release studies by Dayong Teng; Jingli Hou; Xinge Zhang; Xin Wang; Zhen Wang; Chaoxing Li (pp. 333-341).
Glucosamine-carrying temperature- and pH-sensitive microgels with an average diameter of about 100 nm were successfully prepared by free radical precipitation polymerization. The thermo- and pH-responsive properties of the microgels were designed by the incorporation of N-isopropylacrylamide (NIPAM) and acrylic acid (AAc) to copolymerize with acrylamido-2-deoxyglucose (AADG). The stimuli sensitivity of the microgels was studied by the measurement of their sizes and volume phase transition temperature (VPTT) under different surrounding conditions. The results showed that the microgels were responsive to temperature, pH, and ionic strength, and could have a desired VPTT by modifying AADG and AAc contents. The effect of temperature and pH on insulin release from the microgels was also investigated. The release of drug at the tumor-surrounding environment is faster than that under normal physiological conditions. A preliminary in vitro cell study showed that the glucosamine-carrying microgels are more biocompatible to mouse fibroblast cells, compared to the microgels without glucosamine. These glucosamine-carrying dual-sensitive microgels may be promising carriers for targeted drug delivery to tumors.A preliminary in vitro cell study showed that the glucosamine-carrying microgels are nontoxic and more biocompatible to mouse fibroblast cells, compared to the microgels without glucosamine.

Keywords: Glucosamine; Target delivery vehicles; Microgels; Stimuli-sensitive polymers

Surface tension of binary mixtures of imidazolium and ammonium based ionic liquids with alcohols, or water: Cation, anion effect by Urszula Domańska; Aneta Pobudkowska; Marek Rogalski (pp. 342-350).
The surface tensions were measured at atmospheric pressure, with use of a ring tensiometer, of a series of alcoholic solutions of closely related ionic liquids: 1-methyl-3-methylimidazolium methylsulfate, [MMIM][CH3SO4] in alcohol (methanol, or ethanol, or 1-butanol at 298.15 K), 1-butyl-3-methylimidazolium methylsulfate, [BMIM][CH3SO4] in alcohol (methanol, or ethanol, or 1-butanol at 298.15 K), 1-butyl-3-methylimidazolium octylsulfate, [BMIM][OcSO4] in alcohol (methanol, or 1-butanol at 298.15 K) and of 1-hexyloxymethyl-3-methylimidazolium tetrafluoroborate, [C6H13OCH2MIM][BF4], 1,3-dihexyloxymethylimidazolium tetrafluoroborate, [(C6H13OCH2)2IM][BF4] in alcohol (methanol, or 1-butanol, or 1-hexanol at 308.15 and 318.5 K) and hexyl(2-hydroxyethyl)dimethylammonium bromide, C6Br in 1-octanol at 298.15 K. The set of ammonium ionic liquids of different cations and anions (C2Br, C2BF4, C2PF6, C2N(CN)2, C3Br, C4Br and C6Br) was chosen to show the influence of small amount of the ammonium ionic liquid on the surface tension of water at 298.15 K. The influence of the cation, or anion alkyl chain length on the properties under study (densities and surface tension) was tested.

Keywords: Experimental surface tension measurements; Imidazolium, or ammonium based ionic liquids + alcohol (methanol, or 1-butanol, or 1-hexanol, or 1-octanol) mixtures; Molecular interactions; Surface tension of ammonium ionic liquids water solutions

Interaction forces between waterborne bacteria and activated carbon particles by Henk J. Busscher; Rene J.B. Dijkstra; Don E. Langworthy; Dimitris I. Collias; David W. Bjorkquist; Michael D. Mitchell; Henny C. Van der Mei (pp. 351-357).
Activated carbons remove waterborne bacteria from potable water systems through attractive Lifshitz–van der Waals forces despite electrostatic repulsion between negatively charged cells and carbon surfaces. In this paper we quantify the interaction forces between bacteria with negatively and positively charged, mesoporous wood-based carbons, as well as with a microporous coconut carbon. To this end, we glued carbon particles to the cantilever of an atomic force microscope and measured the interaction forces upon approach and retraction of thus made tips. Waterborne Raoultella terrigena and Escherichia coli adhered weakly (1–2 nN) to different activated carbon particles, and the main difference between the activated carbons was the percentage of curves with attractive sites revealed upon traversing of a carbon particle through the bacterial EPS layer. The percentage of curves showing adhesion forces upon retraction varied between 21% and 69%, and was highest for R. terrigena with positively charged carbon (66%) and a coconut carbon (69%). Macroscopic bacterial removal by the mesoporous carbon particles increased with increasing percentages of attractive sites revealed upon traversing a carbon particle through the outer bacterial surface layer.By attaching an activated carbon particle to a cantilever, AFM enables direct measurements of the interaction forces between activated carbon particles and immobilized, waterborne bacteria.

Keywords: AFM; Activated carbon; Bacterial adhesion; Water filtration; Interaction force; Raoutella terrigena; Escherichiae coli; EPS

Synthesis of Pt/Ru bimetallic nanoparticles in high-temperature and high-pressure fluids by Masaki Ueji; Masafumi Harada; Yoshifumi Kimura (pp. 358-363).
A high-temperature and high-pressure flow-reactor system was applied to the synthesis of monometallic ruthenium (Ru) nanoparticles and platinum/ruthenium (Pt/Ru) bimetallic nanoparticles using the thermal reduction of ruthenium ion (Ru(III)) and the mixture of platinum (Pt(IV)) and ruthenium ions in water and ethanol mixture in the presence of poly( N-vinyl-2-pyrrolidone). Monometallic Ru nanoparticles with an average diameter of ca. 2 nm were synthesized above 200 °C at 30 MPa. The monometallic Ru nanoparticles tended to make large aggregates in colloidal dispersions. By the reduction of the mixture solution of Pt(IV) and Ru(III) in water and ethanol above 200 °C at 30 MPa, Pt/Ru bimetallic nanoparticles with an average diameter of ca. 2.5 nm were synthesized with relatively small size distribution. The EXAFS spectra for the Pt/Ru bimetallic particles indicated that the particle possesses metallic bonds between Pt and Ru atoms in contrast to the case of the nanoparticles produced by thermal reduction under ambient pressure at 100 °C [M. Harada, N. Toshima, K. Yoshida, S. Isoda, J. Colloid Interface Sci. 283 (2005) 64], and that the Pt/Ru bimetallic particle has a Pt-core/Ru-shell structure.A TEM image of Pt/Ru(1/1) bimetallic nanoparticles produced by the reduction of both Pt(IV) and Ru(III) salts in water and ethanol 1/1 mixture with PVP at 30 MPa and 300 °C, and the Fourier transforms of EXAFS oscillation of Pt-LIII edge and Ru-K edge for this bimetallic nanoparticle.

Keywords: Platinum/ruthenium bimetallic nanoparticles; High-temperature and high-pressure synthesis; EXAFS

No Title by Arthur Hubbard (pp. 364-364).
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