Journal of Colloid And Interface Science (v.310, #1)

The adsorption characteristics of acid activated sepiolite (AAS) for the removal of chlorophyll-a (C55H72MgN4O5) from rapeseed oil was studied as a function of different sepiolite dosages and bleaching temperatures. A correlation has been shown between the adsorption capacity and a combination of AAS amount, bleaching temperature and oxidative reactions of chlorophyll-a. The adsorption equilibrium was found to follow the Langmuir isotherm model with a maximum adsorption capacity of 0.36 mg/g on AAS and K L value ranging from 6.11 to 19.51 kg/mg at 80 and 100 °C. It was found that AAS is an effective sorbent for the removal of chlorophyll-a molecule which is believed to adsorb as a protonated species onto Si―OH groups at the edge in the tetrahedral sheet of sepiolite. These findings reveal that chlorophyll-a molecules not only adsorb onto the external surface of AAS but replace the released Mg2+ ions in the octahedral sheet; they, depending on the pore size of AAS, are also incorporated in the channels and tunnels of sepiolite. A structural model is proposed to account for the orientation of chlorophyll-a in the sepiolite matrix.Adsorption of chlorophyll-a to AAS.
Keywords: Adsorption; Bleaching; Chlorophyll-a; Sepiolite;

Interaction of silicic acid with goethite by Tjisse Hiemstra; Mark O. Barnett; Willem H. van Riemsdijk (8-17).
The adsorption of Si on goethite (α-FeOOH) has been studied in batch experiments that cover the natural range of Si concentrations as found in the environment. The results have been interpreted and quantified with the charge distribution (CD) and multi-site surface complexation (MUSIC) model in combination with an extended Stern (ES) layer model option. This new double layer approach (ES) accounts for ordering of interfacial water molecules leading to stepwise changes in the location of electrolyte ions near the surface [T. Hiemstra, W.H. Van Riemsdijk, J. Colloid Interface Sci. 301 (2006) 1]. The Si adsorption on goethite peaks at a pH of ∼9 and decreases at lower and higher pH values. Thermodynamically, the pH-dependency of silicic acid adsorption is related to the value of the proton co-adsorption and can also be linked to the Si charge distribution in the interface as is discussed. Based on published EXAFS data, the adsorption of Si on goethite was modeled as the formation of a bidentate surface complex. The ionic charge distribution (CD) of this complex can be calculated from the geometry of this surface complex, optimized with molecular orbital/density functional theory (MO/DFT), and combined with a correction for water dipole orientation. The resulting CD value has been applied successfully in the description of the adsorption data. The use of a theoretical CD value has the practical advantage of a reduction of the number of adjustable parameters with a factor 2. To describe the adsorption at a high Si loading, formation of a Si polymer, e.g. a tetramer, is proposed. Such a species is only contributing to the overall adsorption at solution concentrations above about 10−4 M, where super saturation with respect to quartz exists. The adsorbed silica polymer hydrolyzes at high pH. The reactive ligand of the polymer is quite acid ( log K ≈ 6.5 – 7.1 ), which is typically for the SiO−1 surface groups of polymerized Si, like amorphous SiO2(s), and the SiO−1 ligand of the aqueous dimer Si2O(OH)5O−1(aq). The applied model correctly predicts the change of particles charge and the shift in IEP due to proton release upon Si adsorption.The geometry of the surface structure of adsorbed silicic acid is related to the interfacial charge distribution coefficients which determine the pH and concentration dependency of the adsorption.
Keywords: Co-adsorption; Hematite; Goethite; Gibbsite; CD model; MUSIC model; Singly coordinated; Surface group; Ligand; Surface complex structure; EXAFS; Arsenite;

Calcium hydroxyapatite (CaHAP) and barium hydroxyapatite (BaHAP) have been prepared by a wet method from aqueous solutions with cation/P molar ratio of 1.67. The prepared particles were characterized using XRD, IR, TG–DTA and BET-N2 adsorption measurements. The potential of the synthesized hydroxyapatites to remove Zn(II) from aqueous solutions was investigated in batch reactor under different experimental conditions. Both hydroxyapatites remove Zn(II) from aqueous solutions with an efficiency higher than 98% at initial pH around 6–8. The data reveal that the initial uptake was rapid and equilibrium was established in 20 and 60 min for CaHAP and BaHAP. The sorption process follows the pseudo-first-order kinetic with a rate constant ( k ads ) equals to 1.06 × 10 −2 and 1.91 × 10 −2   min −1 for CaHAP and BaHAP, respectively. Zn(II) removal was quantitatively evaluated using Langmuir isotherm model and the monolayer sorption capacity ( Q max ) shows the values 102.04 and 36.62 mg g−1 for CaHAP and BaHAP clarifying the high affinity of these novel sorbents for Zn(II) ions. Kinetically, the prepared apatites are feasible sorbents retain Zn(II) ions through a favorable and spontaneous sorption process. The possibility of metal recovery and regeneration of hydroxyapatites were investigated using several eluting agents include hydrochloric acids, double distilled water, calcium chloride, barium hydroxide, and copper chloride. Different desorption levels were obtained with the different adsorbents and the maximum recovery yield was achieved with copper chloride.Effect of contact time on sorption of Zn(II) ions onto synthesized hydroxyapatites (pH ∼ 6, temperature = 30 °C and adsorbent weight = 10 g L−1).
Keywords: Hydroxyapatite; Characterization; Sorption; Desorption;

In the Maugis–Dugdale model of the adhesive contact of elastic spheres, the step cohesive stress σ 0 is arbitrarily chosen to be the theoretical stress σ th to match that of the Lennard-Jones potential. An alternative and more reasonable model is proposed in this paper. The Maugis model is first extended to that of arbitrary axisymmetric elastic objects with an arbitrary surface adhesive interaction and then applied to the case of a power-law shape function and a step cohesive stress. A continuous transition is found in the extended Maugis–Dugdale model for an arbitrary shape index n. A three-dimensional Johnson–Greenwood adhesion map is constructed. A relation of the identical pull-off force at the rigid limit is required for the approximate and exact models. With this requirement, the stress σ 0 is found to be k ( n ) Δ γ / z 0 , where k ( n ) is a coefficient, Δγ the work of adhesion, and z 0 the equilibrium separation. Hence we have σ 0 ≐ 0.588 Δ γ / z 0 , especially for n = 2 . The prediction of the pull-off forces using this new value shows surprisingly better agreement with the Muller–Yushchenko–Derjaguin transition than that using σ th ≐ 1.026 Δ γ / z 0 , and this is true for other values of shape index n.A 3D adhesion map is constructed. A relation with the identical pull-off force at the rigid limit is supplemented to make the approximate adhesive contact model match the exact one.
Keywords: Contact; Adhesion; Elastic; Power-law surface profile; Dugdale approximation; Pull-off force; Adhesion map; Lennard-Jones potential;

Polymeric supports are presented as an alternative to granular activated carbon (GAC) for organic contaminant removal from groundwater using permeable reactive barriers (PRB). The search for suitable polymeric sorbents for hydrocarbon extraction from aqueous streams has prompted the synthesis of new resins incorporating new functionalities or modifying the polymer network properties that solve many of the existing problems. Between them, the new type of polymeric sorbents Macronet Hypersol containing a styrene–divinylbenzene macroporous hyperreticulated network has been evaluated. Because of their potential sorptive properties, tests were conducted to determine the feasibility of using them as a low-cost reactive material for groundwater applications. The present work describes the sorption of six polycyclic hydrocarbons (PAHs) from aqueous solution onto both Macronet polymeric sorbent MN200 and granular activated carbon. Batch experiments were performed to determine loading rates of a family of PAHs (naphthalene, fluorene, anthracene, acenaphthene, pyrene, and fluoranthene), from a simple two-rings PAH (naphthalene) up to a four-ring PAH (pyrene). The behavior of a non-functionalized Macronet support (MN200) was compared with the behavior of a recognized material, granular activated carbon (GAC). Analyses of the respective rate data with three theoretical models (pseudo-first- and pseudo-second-order reaction models and the Elovich model) were used to describe the PAH sorption kinetics. Sorption rate constants were determined by graphical analysis of the proposed models. The study showed that sorption systems followed a pseudo-first-order reaction model, although the pseudo-second-order reaction model provides an acceptable description of the sorption process. Graphical analysis showed that the sorption process with activated carbon is a more complex process than the one observed for hyper-cross-linked polymers (MN200). A simulation of the barrier thickness needed to treat a PAH-polluted plume showed that 0.1–1 m of sorption media is enough even for high water fluxes such as 0.1–2 m3/m2/day for both sorbents.Sorption loading rates of PAHs (naphthalene, fluorene, anthracene, acenaphthene, pyrene fluoranthene, pyrene, and naphthalene) with a nonfunctionalized Macronet support (MN200).
Keywords: PAHs (naphthalene, fluorene, anthracene, acenaphthene, pyrene, and fluoranthene); Macronet hyper-cross-linked polymers (MN200); Granular activated carbon; Sorption; Kinetics;

The quantitative description of cooperativity effects at binding of low-molecular reagents with active reactive centers of hybrid materials requires the elaboration of convenient and reliable meaningful models and calculation procedures. The model of fixed polydentate centers was analyzed as a prospective tool for simulation of adsorption equilibria. The model was shown to be flexible and adaptive. At the theoretic foundations, it is equivalent or more general as compared with another approaches. The procedure for constructing the models fitting the experimental data within their errors and the corresponding calculation tools were discussed. The special attention was paid to the problem of simultaneous determination of sorption capacities and equilibrium constants. To overcome this difficulty the strategy involving the fuzzy sets theory was proposed. The elaborated methods were used to characterize a new material, 3-n-propylpyridinium silsesquioxane chloride ion exchanger. Adsorption of Fe(III), Cu(II), Zn(II), Cd(II), and Hg(II) chlorides by the material from ethanol solutions was studied at 298 K. The material was found to possess a high affinity to metal chlorides. The sorption capacities of the material and the constants of adsorption equilibria were determined. The material demonstrates the following order of affinity: FeCl3 > CuCl2, HgCl2 > CdCl2 > ZnCl2. On the base of simulation, the negative cooperativity in the case of the CuCl2 adsorption was concluded, while adsorption of other chlorides is accompanied by the positive cooperativity.Experimental (points) and simulated (lines) isotherms for CdCl2 adsorption. Fixed tetradentate centers (solid line) and fixed bidentate centers (dotted line).
Keywords: Adsorption equilibria; Adsorption isotherms; Nonideal adsorption; Cooperativity effects; Simulation; Fuzzy sets; 3-n-Propyl(4-methylpyridinium) silsesquioxane chloride; Metal chlorides; Adsorption; Ethanol solution;

Sorption of arsenic, cadmium, and lead by chars produced from fast pyrolysis of wood and bark during bio-oil production by Dinesh Mohan; Charles U. Pittman; Mark Bricka; Fran Smith; Ben Yancey; Javeed Mohammad; Philip H. Steele; Maria F. Alexandre-Franco; Vicente Gómez-Serrano; Henry Gong (57-73).
Bio-char by-products from fast wood/bark pyrolyses, were investigated as adsorbents for the removal of the toxic metals (As3+, Cd2+, Pb2+) from water. Oak bark, pine bark, oak wood, and pine wood chars were obtained from fast pyrolysis at 400 and 450 °C in an auger-fed reactor and characterized. A commercial activated carbon was also investigated for comparison. Chars were sieved (>600, 600–250, 250–177, 177–149, and <149 μm) and the particle size fraction from 600 to 250 μm was used without further modification for all studies unless otherwise stated. Sorption studies were performed at different temperatures, pHs, and solid to liquid ratios in the batch mode. Maximum adsorption occurred over a pH range 3–4 for arsenic and 4–5 for lead and cadmium. Kinetic studies yielded an optimum equilibrium time of 24 h with an adsorbent dose of 10 g/L and concentration ∼100 mg/L for lead and cadmium. Sorption isotherms studies were conducted in broad concentration ranges (1–1000 ppb for arsenic, 1 × 10 −5 – 5 × 10 −3  M for lead and cadmium). Oak bark out-performed the other chars and nearly mimicked Calgon F-400 adsorption for lead and cadmium. In an aqueous lead solution with initial concentration of 4.8 × 10 −4  M , both oak bark and Calgon F-400 (10 g/L) removed nearly 100% of the heavy metal. Oak bark (10 g/L) also removed about 70% of arsenic and 50% of cadmium from aqueous solutions. Varying temperatures (e.g., 5, 25, and 40 °C) were used to determine the effect of temperatures. The equilibrium data were modeled with the help of Langmuir and Freundlich equations. Overall, the data are well fitted with both the models, with a slight advantage for Langmuir model. The oak bark char's ability to remove Pb(II) and Cd(II) is remarkable when considered in terms of the amount of metal adsorbed per unit surface area (0.5157 mg/m2 for Pb(II) and 0.213 mg/m2 for Cd(II) versus that of commercial activated carbon.Byproduct chars from bio-oil production might be used as plentiful inexpensive adsorbents for water treatment at a value above their pure fuel value. The oak bark char's ability to remove Pb(II) and Cd(II) is remarkable when considered in terms of the amount of metal adsorbed per unit surface area [0.516 mg/m2 for Pb(II) and 0.213 mg/m2 for Cd(II)] versus that of commercial activated carbon [0.031 mg/m2 for Pb(II) and 0.008 mg/m2 for Cd(II)].
Keywords: Bio-oil char; Activated carbon; Arsenic; Cadmium; Lead; Adsorption; Metals removal; Bio-oils; Bio chars; Adsorption; Water treatment;

The salivary mucin MUC5B and lactoperoxidase can be used for layer-by-layer film formation by Liselott Lindh; Ida E. Svendsen; Olof Svensson; Marité Cárdenas; Thomas Arnebrant (74-82).
In situ ellipsometry was used to study layer-by-layer film formation on hydrophilic and hydrophobized silica surfaces by alternating sequential adsorption of human mucin MUC5B and cationic proteins lysozyme, lactoferrin, lactoperoxidase or histatin 5, respectively. The stability of the multilayers was investigated by addition of sodium dodecyl sulfate solution (SDS). Atomic force microscopy was employed to investigate morphological structures on the surfaces during the layer-by-layer film build-up. It was clearly shown that, on both hydrophilic and hydrophobized silica, only MUC5B and lactoperoxidase showed the ability for multilayer formation, resulting in an approximately linear increase in adsorbed amount and film thickness with each deposition cycle. The net increase in amounts per cycle was larger on the hydrophilic silica. Further, MUC5B needs to be adsorbed first on the hydrophilic substrates to obtain this fast build-up behavior. Generally, addition of SDS solution showed that a large fraction of the adsorbed film could be desorbed. However, films on the hydrophobized silica were more resistant to surfactant elution. In conclusion, MUC5B–cationic protein multilayers can be formed on hydrophilic and hydrophobized silica, depending on the choice of the cationic protein as well as in which order the build-up is started on hydrophilic silica. Additionally, SDS disrupts the layer-by-layer film formed by MUC5B and lactoperoxidase.Mucin (MUC5B) and lactoperoxidase were used to build layer-by-layer structures on silica by alternating adsorption from ambient solutions. The figure shows adsorbed amount (mg/m2) from ellipsometric measurements versus time (min).
Keywords: Multilayer; Ellipsometry; AFM; Adsorption; Glycoprotein; Saliva; Surfaces; Surfactant; Mucoadhesion; Bioadhesion; Lysozyme; Amylase; Lactoferrin; Histatin 5;

Aqueous dye adsorption on ordered mesoporous carbons by Xun Yuan; Shu-Ping Zhuo; Wei Xing; Hong-You Cui; Xiao-Dong Dai; Xin-Mei Liu; Zi-Feng Yan (83-89).
Ordered mesoporous carbons (OMCs) with varying pore size, and microporous carbon, CFY, were synthesized using ordered mesoporous silica SBA-15 and NaY zeolite as hard templates, respectively. N2 adsorption tests show that the synthesized OMCs possess abundant mesopores and centralized mesopore distribution. Methylene blue (MB) and neutral red (NR) were used as probe molecules to investigate their adsorption behaviors on OMCs and CFY. As evidenced by adsorption tests, the volume of mesopores of which the pore size is larger than 3.5 nm is a crucial factor for the adsorption capacity and adsorption rate of MB on OMCs. However, the most probable pore diameter of OMCs was found to be vital to the adsorption capacity and adsorption rate of NR. Theoretical studies show that the adsorption kinetics of MB and NR on OMCs can be well depicted by using pseudo-second-order kinetic model.
Keywords: Ordered mesoporous carbon; N2 adsorption; Adsorption isotherm; Adsorption kinetics;

The corrosion inhibition of mild steel in sulfuric acid by methionine (MTI) was investigated using electrochemical techniques. The effect of KI additives on corrosion inhibition efficiency was also studied. The results reveal that MTI inhibited the corrosion reaction by adsorption onto the metal/solution interface. Inhibition efficiency increased with MTI concentration and synergistically increased in the presence of KI, with an optimum [KI]/[MTI] ratio of 5/5, due to stabilization of adsorbed MTI cations as revealed by AFM surface morphological images. Potentiodynamic polarization data suggest that the compound functioned via a mixed-inhibition mechanism. This observation was further corroborated by the fit of the experimental adsorption data to the Temkin and Langmuir isotherms. The inhibition mechanism has been discussed vis-à-vis the presence of both nitrogen and sulfur atoms in the MTI molecule.The corrosion inhibition and adsorption behavior of methionine on mild steel in sulfuric acid has been evaluated. The compound inhibits steel corrosion by a mixed physical and chemical adsorption mechanism via its ―NH2 and S―CH3 groups, respectively.
Keywords: Mild steel; Corrosion inhibition; Adsorption; Amino acid; Iodide ion; Synergism;

Highly effective removal of heavy metals by polymer-based zirconium phosphate: A case study of lead ion by B.C. Pan; Q.R. Zhang; W.M. Zhang; B.J. Pan; W. Du; L. Lv; Q.J. Zhang; Z.W. Xu; Q.X. Zhang (99-105).
Zirconium phosphate (ZrP) has recently been demonstrated as an excellent sorbent for heavy metals due to its high selectivity, high thermal stability, and absolute insolubility in water. However, it cannot be readily adopted in fixed beds or any other flowthrough system due to the excessive pressure drop and poor mechanical strength resulting from its fine submicrometer particle sizes. In the present study a hybrid sorbent, i.e., polymer-supported ZrP, was prepared by dispersing ZrP within a strongly acidic cation exchanger D-001 and used for enhanced lead removal from contaminated waters. D-001 was selected as a host material for sorbent preparation mainly because of the Donnan membrane effect resulting from the nondiffusible negatively charged sulfonic acid group on the exchanger surface, which would enhance permeation of the targeted metal ions. The hybrid sorbent (hereafter denoted ZrP-001) was characterized using a nitrogen adsorption technique, scanning electron microscope (SEM), and X-ray diffraction (XRD). Lead sorption onto ZrP-001 was found to be pH dependent due to the ion-exchange mechanism, and its sorption kinetics onto ZrP-001 followed the pseudo-first-order model. Compared to D-001, ZrP-001 exhibited more favorable lead sorption particularly in terms of high selectivity, as indicated by its substantially larger distribution coefficients when other competing cations Na+, Ca2+, and Mg2+ coexisted at a high level in solution. Fixed-bed column runs showed that lead sorption on ZrP-001 resulted in a conspicuous decrease of this toxic metal from 40 mg/L to below 0.05 mg/L. By comparison with D-001 and ZrP-CP (ZrP dispersion within a neutrally charged polymer CP), enhanced removal efficiency of ZrP-001 resulted from the Donnan membrane effect of the host material D-001. Moreover, its feasible regeneration by diluted acid solution and negligible ZrP loss during operation also helps ZrP-001 to be a potential candidate for lead removal from water. Thus, all the results suggested that ZrP-001 offers excellent potential for lead removal from contaminated water.A new hybrid sorbent ZrP-D001 based on the Donnan membrane effect was prepared for enhanced lead removal from contaminated water.
Keywords: Zirconium phosphate; Hybrid sorbent; Donnan membrane effect; Heavy metal; Removal; Lead;

Effect of disperse dye structure on dye sorption onto PLA fiber by David Karst; Digvijay Nama; Yiqi Yang (106-111).
The effect of the structure of various disperse dyes on their percentage sorption onto polylactide (PLA) is explained using molecular modeling. The interaction energies between the dyes and PLA have been calculated, and a linear equation has been developed to predict the percentage sorption on PLA based on the dye–PLA interaction energy. The predicted percentage sorption for a dye is shown to agree with its experimentally obtained percentage sorption on commercial PLA fabric and on PLA fiber extruded in our laboratory. Within the dyes, the functional groups that form the strongest interactions with PLA are ―N(C2H4OCOCH3)2, ―(CO)2NC3H6OCH3, ―SO2NHC6H5, ―NO2, ―CN(NH)C6H4, and ―CH(CO)2C6H4, and the groups that form the weakest interactions with PLA are ―Br and ―Cl.The interaction energies between various dyes and PLA have been calculated. A linear equation has been developed to predict the percentage dye sorption based on the dye–PLA interaction energy.
Keywords: Adsorption; Disperse dyes; Functional groups; Intermolecular interactions; Molecular modeling; Poly(lactic acid); Polylactide; PLA;

Core-polystyrene/shell-silica nanocomposite particles are synthesized by simple soap-free emulsion polymerization employing positively charged silica sol. The polymerization is initiated with conventional anionic KPS. It is found that the silica sol should be added after the initiation and nucleation of the soap-free emulsion polymerization in order to obtain colloidally stable composite particles. The excess amount of silica promotes the formation of secondary particles, giving a broader particle size distribution. Above 10 wt% silica relative to styrene, the dispersion stability of the composite particles in water is significantly improved, showing a reduced sedimentation rate. The silica particles of average diameter 25 nm form almost a monolayer shell of approximately 30 nm thickness on the polystyrene particles. The incorporation of silica particles also gives rise to the enhancement of thermal stability when the silica concentration exceeds 10 wt% due to the strong interaction between silica and polystyrene molecules.Core-polystyrene/shell-silica nanocomposite particles are synthesized by simple soap-free emulsion polymerization employing positively charged silica sol and anionic initiator KPA. The silica particles form almost a monolayer shell of thickness approximately 30 nm on the polystyrene particles.
Keywords: Polystyrene; Silica; Nanocomposite; Soap-free emulsion polymerization; Core–shell;

Inorganic colloidal particles were usually used to stabilize the emulsions of small molecular compounds. In this paper, the stable aqueous emulsions of organosilicone resin were prepared by emulsification technique using colloidal nanosilica particles combined with very small amount of emulsifiers. The effects of the silica size and concentration on the rheological behavior of the emulsion were investigated by steady-state and transient rheological measurements and dynamic modulus measurement. It was found that all emulsions containing colloidal silica particles exhibited shear-thinning behavior. The smaller the colloidal silica size was or the more the silica content was, the greater the storage modulus was at low strain amplitude, indicating a stronger interparticle interaction and a solidlike viscoelastic behavior of the emulsion. This rheological behavior can be explained by the formation of the reversible particulate network in the emulsion.The stable aqueous emulsion of organosilicone resin were prepared by post-emulsification technique using colloidal nanosilica particles combined with very small amount of emulsifiers. The effects of the silica size and concentration on the rheological behavior of the emulsion were investigated.
Keywords: Organosilicone resin; Aqueous emulsion; Colloidal silica; Rheological behavior;

Mathematical model for the prediction of the overall profile of in vitro solute release from polymer networks by Adriano V. Reis; Marcos R. Guilherme; Adley F. Rubira; Edvani C. Muniz (128-135).
The loading of solutes onto and their release from hydrogel-based devices can be better understood when they are treated as a partition phenomenon. Partition activity (α) is a parameter that determines the existence of partition phenomena. It expresses the physical chemical affinities of the solute between the solvent and hydrogel phases. When α = 0 , there is no release of the solute from the hydrogel; however, if α > 0 , there is partitioning of the solute between the solvent and the hydrogel phases, and release of the solute from the hydrogel can be observed. The mathematic model proposed here predicts the overall release profile of vitamin B12, methylene blue (MB), and acid orange 7 (AO) from semi-interpenetrating network (semi-IPN) hydrogels composed of PNIPAAm and PAAm. Experimental release tests demonstrated that alterations on variables of the system change both the released fraction and the release rate of such solutes, confirmed by the changes on values of α (an equilibrium parameter) and k R (an kinetic parameter). The modeling of solute release describes the α effects on release of the solute from polymer networks. The solute release mechanism is viewed here as a diffusional transport process and as a partition phenomenon. The partitioning of the solutes occurs between the solvent phase and the hydrogel phase, and the possible physical chemical affinities of the solute between hydrogel and solvent are considered.The proposed mathematical model predicts the overall release profile of vitamin B12, methylene blue, and acid orange 7 from semi-interpenetrating network (semi-IPN) hydrogels composed of PNIPAAm and PAAm.
Keywords: Drug delivery; Hydrogels; Partition; Diffusion; Mathematical model;

The synthesis, characterization and the self-assembly process of a novel biodegradable block copolymer containing a poly(ε-caprolactone), PCL, central block and three poly(N-vinyl-2-pyrrolidone), PVP, arms are reported. Three samples with different amounts of PVP were investigated. The copolymers were characterized by FTIR spectroscopy, 1H NMR and viscosity measurements. The composition and the molecular weights of the block copolymers were established using size exclusion chromatography SEC and 1H NMR. Micelle formation by these copolymers was monitored by using the vibrational fine structure of pyrene monomer fluorescence and the critical aggregation concentrations, cac, of the copolymers in aqueous solution were determined using sigmoid Boltzmann-type fitting of the fluorescence data. Dynamic light scattering measurements showed a bimodal size distribution for the copolymers in solution, indicating that the micellization is an intermolecular process. Partitioning coefficients of pyrene between copolymer micelles and water were also determined and increase in magnitude with increasing ε-caprolactone content of the copolymer.The self-assembling of several new biodegradable and amphiphilic three-arm block copolymers in aqueous solution was demonstrated. These copolymers are macromolecules potentially applicable in pharmaceutical industry, specifically in the field of drug delivery.

Fluorescent organosilica micro- and nanoparticles with controllable size by Robert Vogel; Peter P.T. Surawski; Bradley N. Littleton; Chris R. Miller; Gwendolyn A. Lawrie; Bronwyn J. Battersby; Matt Trau (144-150).
This paper reports on the synthesis of uniformly dye-doped organosilica particles with narrow size distribution. The particle size can be controlled from tenths of nanometers up to several micrometers, whilst still maintaining monodispersity. Microparticles were observed to swell in various solvents up to ∼2.5 times their original volume, suggesting the presence of a gel-like internal structure. As shown by confocal microscopy, this morphological control of particle swelling has important implications for the encoding of the nano/micro particles with organic dyes, such as rhodamine B isothiocyanate. Swelling allows the dye to penetrate the organosilica matrix and produce uniformly dye-doped nano- and microparticles. Finally, we suggest a coagulation model for the particle formation which significantly differs from conventional Stöber synthesis.Dye-doped, functionalised organosilica micro- and nanoparticles with narrow size distribution were fabricated. The particle size can be controlled from tenths of nanometers up to several micrometers. A coagulation model for the particle formation has been suggested.
Keywords: Colloids; Ormosil; Organosilica; Nanoparticles; Microspheres; Dyes; Biomolecules;

In the temperature–composition phase diagram of the nonionic surfactant n-octyl-hydroxypenta(oxyethylene), C8E5, there are three principal curves; the one for the critical micelle concentration (cmc), the one delineating the existence of the hexagonal phase, and then the lower consolute boundary (lcb). In this work it is clarified how the presence of the alkali halides NaF, LiCl, NaCl, NaBr and NaI in the aqueous solutions, up to high molalities, change the lcb temperature-position and shape. The lcbs are obtained from measurements of cloud-point temperatures. Rather marked anion-controlled shifts are observed in the boundary temperature-position, and the order of the anions is in accordance with the prediction of the Hofmeister series. Also the shape of the boundary is affected in an anion-specific way, so that the largest changes are found with the strongest salting-out agent. The separation point varies in distinctly non-linear manners with the molality of the studied alkali halides. An approach is presented that can reproduce the effects of the alkali halides on the cloud-point temperature of C8E5 and a poly(ethylene oxide) polymer, at low amounts of the macroentities. In this approach use is made of the known behaviour of the electrolytes at the air/water surface and the virial expansion, to account for the initial salting-out/-in effect and the variation of the effect with electrolyte molality.Calculated cloud-point temperature trends (solid curves) as a function of electrolyte molality for C8E5, shown together with the corresponding experimental points. Closed circles represent data from an earlier study.
Keywords: Surfactant; Polymer; Oxyethylene; Consolute boundary; Electrolyte; Ion; Hofmeister series; Surface;

Ligand-dependent particle size control of PbSe quantum dots by In Chan Baek; Sang Il Seok; Nimai Chand Pramanik; Sunirmal Jana; Mi Ae Lim; Boek Yeop Ahn; Chang Jin Lee; Yong Jae Jeong (163-166).
Colloidal solutions of monodisperse PbSe quantum dots (QDs) were synthesized by a hot solution chemical method from a reaction mixture of lead oleate and TOPSe (TOP: tri-n-octylphosphine). The synthesis was carried out at a fixed temperature (170 °C) and time, while the particle sizes of the PbSe QDs were controlled by using two different kinds of organic ligands with varied chain length. It was seen that the tuning of PbSe QDs are possible by using the proper molar ratio of the co-ligands, such as acetic acid or hexanoic acid, at a fixed reaction temperature and time, verified by TEM and XRD as well as NIR absorption analysis. The effects of different organic acids were studied and the role of additional organic acids might be due to the extent of ligand exchange efficiency between the Pb oleate and acetic/hexanoic acid in the initial stage, which is caused by the steric hindrance effects of the acids.
Keywords: Particle size control; PbSe quantum dots; Ligand exchange;

Synthesis of small-sized rhenium sulfide colloidal nanoparticles by Weixia Tu; Benoît Denizot (167-170).
Rhenium sulfide colloidal nanoparticles with average size 5.5 nm were synthesized. Characterizations by ultraviolet–visible spectrophotometry, transmission electron microscopy, energy dispersive X-ray spectrum, and X-ray powder diffraction verified the formation of ReS2 rhenium sulfide colloidal nanoparticles. The colloidal nanoparticles had good stability and they could be stored stably for 1 week in water. Surface modification by organic molecules improved the stability of the rhenium sulfide nanoparticles. The small-sized rhenium sulfide nanoparticles may be useful for their promising applications in tracing diagnosis and therapy of tumor diseases.Radioactive rhenium has potential applications in the diagnosis and therapy of tumor disease. Rhenium sulfide colloidal nanoparticles with average diameter 5.5 nm were synthesized in glycol solvent by using a stable isotope of rhenium at room temperature.
Keywords: Rhenium sulfide; Colloidal nanoparticles; Ethylene glycol; Radiotherapy;

Monodispersed and well-aligned samples of TiO2 nanosquares were synthesized in large quantities in the presence of tetramethylammonium hydroxide (TMAOH) for the first time. These nanosquares were single crystals characterized by slightly truncated shape bounded by {101} facets. XRD, AFM, FT-IR, Raman scattering, TEM and HRTEM were employed to characterize the as-prepared samples. The possible microreaction mechanism was discussed. As a result, TMAOH accelerates the formation of crystalline anatase and plays a structural template role to modify the particle shape to nanosquare. Moreover, TMAOH reacted with hydrolysates and formed layered structural complex compound.The sol hydrothermally treated at 160 °C for 4 h was investigated by TEM. The anatase nanoparticles with side-length of 10 − 13  nm are nanosquare-shaped, monodispersed, and aligned in large scales.
Keywords: Anatase; Aligned nanosquare; Nanorod; TMAOH; Hydrothermal treatment;

C-undodecylcalix[4]-resorcinarene (C11-resorcinarene)-capped anatase TiO2 nanoparticles have been synthesized and could be isolated and redispersed in different nonaqueous solvents. The adsorption of C11-resorcinarene onto the surface of TiO2 nanoparticles led the shifting of the onset wavelength of the optical absorption in the visible range along with a broad band centered at 422 nm corresponding to ligand-to-metal charge transfer transition within the surface titanium(IV)–C11-resorcinarene complex. The interaction of TiO2 nanoparticle with C11-resorcinarenes was investigated by photoluminescence (PL). Proton nuclear magnetic resonance (1H NMR) spectroscopy study revealed that the C11-resorcenarene molecules adsorbed chemically onto the surfaces of TiO2 nanoparticles. The average particle diameter of bare anatase TiO2 and C11-resorcinarene-capped TiO2 was determined using transmission electron microscopy (TEM) and was found to be equal to ca. 5 nm.Surface modification of anatase TiO2 nanoparticles has been made by the macrocyclic ligand C11-resorcinarene. Modified TiO2 nanoparticles show the onset wavelength of the optical absorption in the visible range, at 663 nm.
Keywords: Anatase TiO2 nanoparticles; Resorcinarene; Organo-capped; Photoluminescence;

Fourier transform infrared (FTIR) spectra are presented of CO gas-treated protected gold colloids prepared from hydrazinium hydrate reduction of an Au(III) precursor which reproducibly feature a weak, shortlived peak at ca. 2169 cm−1. When the gold colloid was treated with 99% isotopically enriched 13CO gas, the IR peak shifted to a frequency of 2114 cm−1 which indicated that it represented a simple gold monocarbonyl species. The value of 2169 cm−1 for the CO stretching frequency suggests the peak represents CO physisorbed on oxidised gold atoms on the colloid surface. The peak is not observed when the concentration of the colloidally dispersed gold is reduced either by use of lower starting salt concentrations or by aggregation. It is also not observed when solutions of the protecting agent or reducing agent or the dispersion medium (water) or even the starting Au(III) salts are CO-treated individually. This confirms that the spectral feature is uniquely associated with colloidally dispersed gold. In general, the work has shown that the surfaces of Au colloids in situ have partially oxidised Au character which is of interest in systems where supported nanoparticulate gold derived from colloid preparations are considered for low temperature oxidation catalysts for CO.This paper reports a study in which CO physisorbed onto colloidal gold particles in situ has been detected using transmission FTIR spectroscopy.
Keywords: Gold; Colloids; Catalysts; FTIR; CO; TEM; XPS; Physisorption;

A simple method has been developed to synthesize Cu/Pd nanoparticles in aqueous solution in ambient condition with the addition of complexing agent, trisodium citrate. UV–vis spectra confirmed the complexing behavior of trisodium citrate and metal ions. The particles synthesized with trisodium citrate were well dispersed with particle size ranging between 3–4 nm while the particles without trisodium citrate were larger and aggregated, as demonstrated by transmission electron microscopy (TEM). X-ray diffraction patterns (XRD) indicated the formation of bimetallic nanoparticles without impurities in the complexing agent-supplemented system. In contrast, large amounts of PdO and Cu(OH)2 were precipitated along with the formation of particles in the complexing agent-free system. X-ray photoelectron spectroscopy (XPS) revealed small amounts of oxidized Pd on the surface of particles and the existence of zerovalent Cu and oxidized Cu in particles with trisodium citrate. With a simpler process for electroless copper deposition, the Cu/Pd nanoparticle activator with less Pd metal used exhibited comparable catalytic activity to conventional Pd/Sn colloidal activator. In summary, application of Cu/Pd nanoparticles synthesized with the complexing agent as an activator suggested a novel, simpler and inexpensive process in PCB industry.The Cu/Pd nanoparticles synthesized with complexing agent can be applied as an activator for electroless copper deposition in PCB industry.
Keywords: PVP; Cu/Pd nanoparticles; Electroless deposition; Catalyst; Activator;

Gly311 residue triggers the enantioselectivity of Staphylococcus xylosus lipase: A monolayer study by Habib Mosbah; Adel Sayari; Robert Verger; Youssef Gargouri (196-204).
Using emulsified triacylglycerols, we have shown recently [Mosbah et al., 2007, submitted for publication] that amino acid residue G311 of Staphylococcus xylosus lipase (SXL) is critically involved in substrate selectivity, pH and temperature dependency. Using the monomolecular film technique, we show in the present study that the four single mutants of this residue (G311L, G311W, G311D, and G311K), interact efficiently with egg-phosphatidyl choline (egg-PC) monomolecular films, comparably to the wild-type (G311). A critical surface pressure ( π c ) of about 25 mN/m was obtained with the SXL wild-type (SXL-WT) and its mutants. These results support our conclusion that the G311 residue is not involved in the interfacial adsorption step of SXL. A kinetic study on the surface pressure dependency, stereoselectivity, and regioselectivity of SXL-WT and its G311 mutants was also performed using optically pure enantiomers of diacylglycerols (1,2-sn-dicaprin and 2,3-sn-dicaprin) and a prochiral isomer (1,3-sn-dicaprin) spread as monomolecular films at the air–water interface. Our results indicated that the mutation of one single residue at position 311 affects critically the catalytic activity, the stereo- and the regioselectivity of SXL. As previously observed with emulsified substrates [Mosbah et al., 2007, submitted for publication] we observed that an increase in the size of the 311 amino acid side chain residue was accompanied by a decrease of lipase activity measured on dicaprin monolayer. We also noticed that the substitution of G311 by a basic or acidic residue (G311K and G311D), induces a significant shift of the pH optimum from 8 to 9.5 or from 8 to 6.5, respectively.A single-point mutation affects critically the regio- and the stereoselectivity of Staphylococcus xylosus lipase. The specific regio- or stereoselectivity can be said to be a fingerprint of lipases.
Keywords: Staphylococcus xylosus lipase; Mutants; Monomolecular films; Critical surface pressure; Stereoselectivity; Regioselectivity;

Bimodal pore size distributions for carbons: Experimental results and computational studies by Piotr A. Gauden; Artur P. Terzyk; Mietek Jaroniec; Piotr Kowalczyk (205-216).
It is well known that the bimodal shape of the pore size distribution (PSD) curves is typical for various carbonaceous materials (of different origin and/or treated thermally or chemically). A systematic investigation of this effect has been discussed using the Nguyen and Do method with proposed recently the ASA algorithm. A series of numerically generated adsorption isotherms (N2, T = 77   K ) and experimental data were analyzed. We investigated various possible situations related to the shape of the PSD curves, i.e., the intensity of the both peaks, their mutual location and the vanishing of one of them. Moreover, the problem in the similarity of the local adsorption isotherms from the range of pore widths corresponding to the gap between peaks is discussed. The analysis of obtained results (as well as published by others) shows that the bimodal shape of the pore size distributions is a characteristic feature for many adsorbents possessing even a small amount of micropores. It is shown that this feature results from the similarity of the local adsorption isotherm in the range of the pore widths for which the gap between peaks (related to the primary and secondary micropore filling mechanism) exists.Experimental nitrogen adsorption isotherms at 77 K (left figure) measured on the synthetic carbons and the corresponding differential PSDs (medium figure). Schematic representation of the theoretical calculation strategy (right figure).
Keywords: Activated carbon; Adsorption; Microporosity; Pore size distribution;

This study compares the stability of various polymeric thin films supported on SiO x /Si substrate. Dewetting behaviors of polystyrenes (PS), polychloromethylstyrenes, and random poly(styrene-co-chloromethylstyrene)s are investigated by utilizing atomic force microscopy. A systematic addition of the chloromethylstyrene (ClMS) unit into PS chain causes the increase of segment polarity, affecting interfacial and interchain interactions in thin films. It is found that stability of the polymeric films depends on two major parameters, ratio of the ClMS unit and film thickness. For ∼5 nm thick film, the addition of only 5 mol% ClMS unit causes a drastic increase of its stability, attributed to the enhanced interfacial interactions between ClMS group and SiO x layer. Further increasing the ClMS mole ratio to 20, 45, and 100% is accompanied by a systematic increase of the film stability. Thicker films (thicknesses ∼22 and ∼45 nm) of the copolymer with 5 mol% ClMS unit exhibit rather different behavior. They are found to be less stable compared to the PS films. However, the films of copolymers with ClMS unit of 20, 45, and 100% are still much more stable than the PS films. These dewetting behaviors of the copolymers are correlated to the interfacial interactions, interchain interactions and segmental segregation in thin films.The presence of chloromethyl group in polystyrene enhances interfacial interactions with SiO x /Si substrate. Upon annealing, the polystyrene film (left) dewets the surface while film of the copolymer (right) is stable.
Keywords: Dewetting suppression; Interfacial effects; Interchain interactions; Surface anchoring; Nanodewetting; AFM;

The phase diagrams of the pseudo-quaternary systems poly(oxyethylene) (10) stearyl ether (Brij-76)/1-butanol/isooctane/water (with equal amounts of oil and water in the presence of two nonaqueous polar solvents (NPS), ethylene glycol (EG), and tetraethylene glycol (TEG)), have been constructed at 30 °C. Regular fish-tail diagrams were obtained up to ψ (weight fraction of EG or TEG in the mixture of polar solvents) equal to 0.5, confirming the establishment of hydrophile–lipophile balance (HLB) of the systems. The maximum solubilization capacity passed through a minimum at ψ = 0.2 . No HLB was obtained at higher ψ. The usual fish-tail diagrams were also obtained in temperature-induced phase mapping at fixed W 1 (weight fraction of 1-butanol in total amphiphile). Solubilization capacity and HLB temperature ( T HLB ) decreased with increasing ψ at a fixed W 1 , the effect being more pronounced for TEG than EG. A correlation between HLB temperature ( T HLB ) and HLB number ( N HLB ) of mixed amphiphiles (Brij-76 + Bu) in pseudo-quaternary systems (in the presence of water and partial substitution of water with both NPS) has been established. The novelty of the work with respect to possible applications has been discussed.Phase behavior of the mixture of poly(oxyethylene) (10) stearyl ether (Brij-76)/1-butanol/isooctane has been investigated in the presence of the mixed solvents (water + ethylene glycol) and (water + tetraethylene glycol).
Keywords: Phase behavior; Brij-76; Nonaqueous microemulsion; Ethylene glycol; Tetraethylene glycol; HLB temperature;

Adsorption and micelle formation of alkylammonium chloride–alkyltrimethylammonium chloride mixtures by Y. Hayami; A. Wataya; T. Takiue; N. Ikeda; H. Matsubara; M. Aratono (240-245).
The surface tension of the aqueous solutions of binary cationic surfactant mixtures of (1) dodecylammnonium chloride (DAC)–tetradecyltrimethylammonium chloride (TTAC), (2) decylammonium chloride (DeAC)–dodecyltrimethylammonium chloride (DTAC), and (3) DAC–DTAC was measured as a function of the total molality and composition of surfactants at 298.15 K. The compositions of surfactants in the adsorbed film and micelle were evaluated and the phase diagram of adsorption and that of micelle formation were constructed. Furthermore the excess Gibbs energies of adsorption and micelle formation were calculated to estimate the deviation from the corresponding ideal mixing. It was found that the surface and micelle are enriched in trimethylammonium salts in (1) and (2), while in ammonium salt in (3) compared to the bulk solution. On the other hand, the micelle is enriched in trimethylammonium salts compared to the surface at the critical micelle concentration (CMC) in all the systems. The miscibility of the surfactants was clarified from the standpoints of the structure of the head group and of the matching between the size of polar head group of surfactants and the difference in hydrocarbon chain length.A staggered structure of adsorbed film and the matching between the size of head group and the difference of chain length are essential miscibility factors for mixtures containing a trimethylammonium surfactant.
Keywords: Binary surfactant mixture; Miscibility at surface and micelle; Ideal mixing; Excess Gibbs energy; Staggered structure;

Effect of interfacial rheology on model emulsion coalescence by H.W. Yarranton; D.M. Sztukowski; P. Urrutia (246-252).
Interfacial elasticity and “dynamic” surface pressure isotherms were measured for interfaces between a dispersed water phase and a continuous phase of asphaltenes, toluene, and heptane. The interfacial modulus is a function of asphaltene concentration and in all cases reached a maximum at an asphaltene concentration of approximately 1 kg/m3. The modulus increased significantly as the interface aged and slightly as the heptane content increased to a practical limit of 50 vol%. The modulus was approximately the same at 23 and 60 °C. The modulus correlated with the inverse of the initial compressibility determined from surface pressure isotherms. The surface pressure isotherms also indicated that a phase transition occurred as the interface was compressed leading to the formation of low compressibility films. Crumpling was observed upon further compression. The phase transition shifted to a higher film ratio with an increase in heptane content and interface age. Asphaltene concentration and temperature (23 and 60 °C) has little effect on the surface pressure isotherms. The surface pressure and elasticity measurements are consistent with the gradual formation of a cross-linked asphaltene network on the interface.Asphaltenes adsorb irreversibly on a water–hydrocarbon interface over time. The films undergo a transition from a high compressibility phase to a low compressibility phase upon contraction of the interface.
Keywords: Asphaltenes; Emulsions; Interfacial rheology; Elasticity; Interfacial films; Emulsion stability;

Effect of interfacial rheology on model emulsion coalescence by H.W. Yarranton; P. Urrutia; D.M. Sztukowski (253-259).
In Part I, surface pressure isotherms were measured for model interfaces between a dispersed water phase and a continuous phase of asphaltenes, toluene, and heptane. Here, the coalescence rate of model emulsions prepared from the same components is determined from measured drop size distributions at 23 °C. A correlation is found between the initial coalescence rate and the interfacial compressibility. It is shown that the change in coalescence rate as the emulsion ages and coalesces can be predicted from surface pressure isotherm data also obtained at 23 °C. The stability of the emulsions was further assessed in terms of free water resolved after a treatment of heating at 60 °C and centrifugation. The emulsions were aged up to 24 h prior to treatment. The free water resolution appears to correlate to the “capacity for coalescence” of the interfacial film; that is, to the product of the initial film compressibility and (1-CR), where CR is the film ratio at which the film crumples.Predicted change in interfacial compressibility (a) and mean droplet diameter (b) of a coalescing emulsion prepared from water and asphaltenes in a solution of heptane and toluene.
Keywords: Asphaltenes; Emulsions; Interfacial rheology; Interfacial films; Emulsion stability;

Synthesis of bilayer oleic acid-coated Fe3O4 nanoparticles and their application in pH-responsive Pickering emulsions by Qiang Lan; Chao Liu; Fei Yang; Shangying Liu; Jian Xu; Dejun Sun (260-269).
Fe3O4 nanoparticles coated with oleic acid bilayer (a diameter about 12 nm) were synthesized. The structure and composition of the particles were analyzed by TEM, FTIR and TGA. The TGA experiments of the bilayer-coated particles show a distinct two-stage mass loss. Partition experiments show that the modified Fe3O4 nanoparticles are affected by aqueous dispersion pH and ion strength. Accordingly, the Pickering emulsions stabilized by modified Fe3O4 particles are also sensitive to pH and ion strength. The phase inversion of the emulsions occurs when 1.00 < pH < 12.05 , and no phase inversion occurs after complete desorption of the second layer surfactants when pH > 13.50 . The phase inversion of emulsions also can be adjusted by the ion strength. In interfacial adsorption experiments, the hydrophobic Fe3O4 nanoparticles form particle clusters, while the hydrophilic particles form uniform multilayers.The stability of Pickering emulsions stabilized by 1.0 wt% modified Fe3O4 nanoparticles. The emulsion types change from W/O to O/W, then to W/O with increasing pH.
Keywords: Fe3O4 nanoparticles; Pickering emulsions; Phase inversion; Stability;

Propagation of ultrasound through a porous body generates an electric signal, similarly to the well-known electroacoustic effect in dispersions of mobile particles. This obscure version of electroacoustics has been known since 1948, when M. Williams published his paper on electrokinetic transducers [M. Williams, Rev. Sci. Instrum. 19 (10) (1948) 640–646]. We observe this effect in a 1 wt% aqueous dispersion of carbon nanotubes. Magnitude and phase of the electroacoustic signal, as well as conductivity, are sensitive to sonication and mixing. Sonication with no mixing leads to phase rotation by up to 180° comparing to the traditional colloid vibration current (CVI) in sols. This is explained by the fact that sonication terminates motion of the carbon nanotubes by building up a continuous network gel. Propagation of ultrasound through the immobile carbon nanotube network generates a streaming vibration current (SVI), but not a CVI, which requires free motion of the particles relative to the liquid. Theoretical analysis indicates that the SVI has 180° difference in phase from the CVI. The magnitude of the SVI after sonication with no mixing depends on the shifts of the measuring probe position. Apparently this occurs due to inhomogeneity of the carbon nanotube gel, which might have clusters with higher density and gaps with no solids at all. This effect can be used for testing homogeneity of the carbon nanotube gel. Sonication with continuous mixing also affects the electroacoustic signal and conductivity. However, the electroacoustic phase does not reach 360°, which corresponds to the SVI in gel. The measured signal is the vector sum of the CVI and SVI under these conditions. It is possible to use data on the electroacoustic phase to monitoring the number of carbon nanotube segments that retain independent motion.Propagation of ultrasound through a porous body generates an electric signal. This obscure version of electroacoustics has been known since 1948. We observe this streaming vibration current in a 1 wt% aqueous dispersion of carbon nanotubes.
Keywords: Streaming current; Colloid vibration current; Sol–gel transition; Carbon nanotubes;

The effect of the presence of a charged boundary on the electrophoretic behavior of a particle is investigated by considering a sphere at an arbitrary position in a spherical cavity under conditions of low surface potential and weak applied electric field. Previous analyses are modified by using a more realistic electrostatic force formula and several interesting results, which are not reported in the literature, are observed. We show that the qualitative behavior of a particle depends largely on its position, its size relative to that of a cavity, and the thickness of the electric double layer. In general, the presence of a cavity has the effect of increasing the conventional hydrodynamic drag on a particle through a nonslip condition on the former. Also, a decrease in the thickness of the double layer surrounding a sphere has the effect of increasing the electrostatic force acting on its surface so that its mobility increases. However, this may not be the case when an uncharged particle in placed in a positively charged cavity, where the electroosmotic flow plays a role; for example, the mobility can exhibit a local maximum and the direction of electrophoresis can change.Electrophoresis of a sphere at an arbitrary position in a spherical cavity.
Keywords: Electrophoresis; Effect of charged boundary; Sphere in spherical cavity;

Structural and optical properties of KTa0.77Nb0.23O3 nanoplates synthesized by hydrothermal method by Yongming Hu; Haoshuang Gu; Zhenglong Hu; Hao Wang (292-296).
Two-dimensional KTa0.77Nb0.23O3 (KTN) nanoplates with edge sizes of about 100 nm and thickness of about 10 nm have been fabricated by hydrothermal method at 200 °C using Ta2O5, Nb2O5, and KOH served as the precursors. Detailed structural studies indicate that the synthesized products are made up of large quantity single crystalline nanoplates with quadrilateral shape, which have a cubic perovskite structure without any other impurity phase and (011) growth direction. The stacking faults may be the key in the formation and growth of the (011) plate. Room temperature photoluminescence spectra excited at different wavelengths exhibit a strong emission band centered at 470 nm (2.63 eV) as well as two weak emission peaking at 423 nm (3.06 eV) and 505 nm (2.46 eV), respectively. The electron–hole recombination of localized excitons should responsible for the light emissions at 423 and 470 nm. Room temperature Raman spectrum of KTN nanoplates reveal that the frequencies of vibration mode are lower slightly than that of KTN bulk materials, and the scattering profile is to be more diffused and enlarged, which may be induced by the crystal structure defects, such as stacking faults.The TEM image of KTN nanoplates with edges size of about 100 nm, and the corresponding HRTEM image with [011] zone axis at the edge region of KTN nanoplates.

Hematite spindles with optical functionalities: Growth of gold nanoshells and assembly of gold nanorods by Miguel Spuch-Calvar; Jorge Pérez-Juste; Luis M. Liz-Marzán (297-301).
The layer-by-layer (LBL) assembly method, combined with the seeded growth technique, have been used to deposit gold shells on the surface of hematite (α-Fe2O3) spindles. While the LBL method yields dense coatings of preformed Au nanoparticles, when AuCl 4 ions are further reduced by a mild reducing agent, thicker, rough nanostructured shells can be grown. The deposition process was monitored by TEM and UV–visible spectroscopy, demonstrating a gradual change in the optical features of the colloids as the surface is more densely covered. The particles so-prepared can find useful applications in cancer therapy and as SERS substrates. Additionally, we show that Au nanorods can be assembled on hematite spindles, providing a flexible way to tune the optical properties of the resulting composite colloids.The optical properties of colloidal hematite spindles can be easily tailored through the growth of Au continuous shells or the deposition of Au nanorods.
Keywords: Hematite spindles; Gold nanoshells; Gold nanorods; Layer-by-layer assembly;

The morphological variation of wurtzite-type zinc oxide (ZnO) grown on a substrate in basic aqueous solutions was investigated using a wide variety of organic molecules with carboxy and sulfonic groups. The effect of the organic molecules on the nanometric morphology was classified into several categories. Hexagonal plates exhibiting the (001) planes were obtained by a planarizing effect with the addition of citric, tartaric, and maleic acids, although acetic, salicylic, fumaric, and succinic acids exhibited no effects on the morphology. The production of nanograins was observed by a miniaturizing effect with the addition of a polymeric molecule with carboxy groups and an anionic surfactant with a sulfonic group. Mosaic structures composed of granular crystals and bundles consisting of fibrils elongated in a direction toward the c-axis were produced by the addition of bulky dye molecules having benzene rings and carboxy or sulfonic groups. The influence of the organic molecules was related to the number of the functional groups and the stereochemical structure. The findings of this study suggest that the adsorbability of the organic molecules depending on the chemical structure to the specific crystal faces is essential for the variation of the nanometric morphology.The morphological variation of wurtzite-type zinc oxide grown on a substrate in basic aqueous solutions was investigated using a wide variety of organic molecules with carboxy and sulfonic groups.
Keywords: Crystal growth; Morphological control; Adsorption; Zinc oxide;

The role of polymer compatibility in the adhesion between surfaces saturated with modified dextrans by Malin Eriksson; Shannon M. Notley; Robert Pelton; Lars Wågberg (312-320).
Wet and dry adhesion between dextran-coated surfaces were measured aiming to understand the influence of polymer compatibility. The wet adhesion measurements were performed using the atomic force microscope (AFM) colloidal probe technique whereas the dry adhesion measurements were performed using the micro adhesion measurement apparatus (MAMA). Two types of dextrans were used, one cationically modified dextran (DEX) and one that was both cationically and hydrophobically modified (HDEX), leading to three different combinations of polymer-coated surfaces; (1) DEX:DEX, (2) HDEX:DEX, and (3) HDEX:HDEX. DEX increased dry adhesion more than HDEX did, which likely is due to differences in the ability to form specific interactions, especially hydrogen bonding. HDEX gave strong wet adhesion, probably due to its poorer solvency, while DEX contributed to reducing the wet adhesion due to its hydrophilicity. All combinations showed a steric repulsion on approach in aqueous media. Furthermore, when HDEX was adsorbed on either or both surfaces a long range attractive force between the surfaces was detected outside this steric regime.The importance of polymer compatibility was studied in adhesion measurements using dextran (DEX) and hydrophobically modified dextran (HDEX). It was anticipated that the incompatible pair (HDEX:DEX) would give the weakest adhesion.
Keywords: Adhesion; Interaction forces; Polymer; Adsorption; Incompatible; Asymmetric; Cationic dextran; Hydrophobic; Hydrophilic; AFM; Colloidal probe technique; JKR;

Surface charge of human hair has a significant effect on manageability, feel, and appearance. For this reason, controlling charge buildup to improve these factors is an important issue in the commercial hair care industry. Physical wear has been shown to cause surface potential change in conductors and semiconductors, and it is of interest whether or not physical wear alone can cause a surface potential change on hair and other insulating materials. It is known that interaction of hair with dissimilar materials, such as plastic combs, hands, and latex balloons, creates a charge on hair, and determining the mechanisms of this phenomenon is the purpose of this study. In this study the surface potential of human hair is measured using the Kelvin probe method with an atomic force microscope (AFM). A variety of samples are worn with a diamond tip to study the effect of physical wear on surface potential. Hair samples are rubbed with latex to study the effect of triboelectric charging on the microscale. The potential on the sample surface is then measured with a conductive tip. Caucasian virgin (undamaged), chemically damaged, and mechanically damaged hair samples are studied to determine the effect of damaging treatments on surface charge properties. Samples treated with PDMS silicone conditioner as well as those treated with an amino silicone conditioner are also studied to determine the effect of conditioner treatment. Mechanisms for the given results are discussed and recommendations given.Surface charge of human hair has a significant effect on manageability, feel, and appearance. The surface potential of human hair is measured using the Kelvin probe method with an AFM.
Keywords: Kelvin probe microscopy; Human hair; Conditioner; Surface potential;

The interfacial composition and the structure of the water/C12– EO x –C12⋅2Br/n-hexanol/n-heptane microemulsion have been investigated by the dilution method. The results showed that C12– EO x –C12⋅2Br formed a stable water/oil microemulsion with the assistance of n-hexanol. Owing to the relatively large size of the head group, more n-hexanol molecules are populated on the droplet surface than in the C12–2–C12⋅2Br system. The radius of the water pool of the C12–EO3–C12⋅2Br system is not as sensitive to W 0 as in the C12–2–C12⋅2Br system. Another feature of the present system is that its droplet size is considerably smaller than that of the C12–2–C12⋅2Br system, and also those of the CPC and CTAB systems at relative high water content. This provides a potential application for the synthesis of nanoparticles with small size.C12– EO x –C12⋅2Br forms a stable w/o microemulsion with the assistance of n-hexanol. Owing to the relatively long spacer chain as well as the features of the oxyethylene groups in the spacer, more n-hexanol molecules are required to populate on the droplet surface.
Keywords: C12– EO x –C12⋅2Br homologs; n-Hexanol; Dilution method; Interfacial composition of the w/o microemulsion; Structural parameters;

Langmuir and Langmuir–Blodgett monolayers of N-(4-octadecyloxy-2-hydroxybenzylidene) derivatives of glycine, tyrosine, and phenylalanine were studied using π – A isotherms and photoelastic modulated FTIR (PEM-FTIR). Based on compression modulus and interaction parameters, mixed monolayers of these compounds with stearylamine (SAM) showed well-organized monolayers compared to mixed systems with stearic acid (SA) and stearyl alcohol (SAL). The pure amphiphiles exhibited fairly well-ordered packing in the films, and in the mixtures, the ordering increased and showed a triclinic packing arrangement. For the phenylalanine amphiphile the packing showed slight disorder compared to the other two compounds. Surface properties of the LB films of these compounds on solid substrates were analyzed using static and dynamic contact angles of a series of liquids. The surface tension of coated substrates reflected clearly the highly acidic character. Fluidlike monolayers having a molecularly rough surface indicated high wettability for n-alkanes. In contrast, the monolayer containing well-ordered, well-packed alkyl chains indicated low wettability and small hysteresis. πA isotherms and photoelastic modulated FTIR (PEM-FTIR) were used to characterize Langmuir and Langmuir–Blodgett films of N-(4-octadecyloxy-2-hydroxybenzylidene) derivatives of glycine, tyrosine and phenylalanine and their mixed films with stearic acid, stearyl alcohol and stearylamine. The mixed films exhibited increase in order compared to the pure amphiphiles and packed in a triclinic packing arrangement.
Keywords: Lipoamino acids; LB films; Wettability; Mixed monolayers;