Journal of Colloid And Interface Science (v.314, #1)

Individual wood fibres were partly treated with polyelectrolyte multilayers (PEMs) consisting of two different polymer combinations, poly allylamine (PAH)/poly acrylic acid (PAA) and polyethylene oxide (PEO)/PAA in order to study the influence of these polymers on fibre wettability. Single fibres were partly treated and analysed using a so-called dynamic contact analyser (DCA) where the fibres are wet under controlled conditions. When PAH/PAA was used, a stronger influence on fibre wettability was detected when PAH was adsorbed in the outermost layer of the multilayer than when PAA was adsorbed in the outermost layer. The wettability of fibres treated with PAH/PAA PEMs was also influenced by the pH of the adsorption. With the PEO/PAA system, however, the type of polymer adsorbed in the outermost layer caused no detectable difference. Tests of sheets prepared from fibres treated with PEO/PAA showed an increase of about 90% in the tensile index when 9 layers were adsorbed. These and other recently published results from similar experiments using PAH/PAA [S.M. Notley, M. Eriksson, L. Wågberg, J. Colloid Interface Sci. 292 (2005) 29] are compared to the results for the PEM-treated individual fibres. The results indicate that fibres with low wettability contribute to greater paper strength. AFM-force measurements, with the aid of a colloidal probe technique, have also been performed using PAH/PAA, showing that there is also a close correlation between lower wettability of the surfaces and a higher pull-off force between the PEM treated surfaces, i.e. the flat surface and the colloidal probe. This is valid for the two pH strategies that are used for the formation for the PAH/PAA PEMs, which are studied using AFM-force measurements.Single fibres were partly PEM treated and analysed using a so-called dynamic contact analyser (DCA). AFM-force measurements indicate lower a higher pull-off force between the low wettability PEM treated surfaces.
Keywords: Polyelectrolyte; Multilayer; Adsorption; Reflectance; Contact angle; Dynamics; Paper; Mechanical properties; Individual; Wood fibre;

Ni(II) complexation to amorphous hydrous ferric oxide: An X-ray absorption spectroscopy study by Ying Xu; Lisa Axe; Thipnakarin Boonfueng; Trevor A. Tyson; Paras Trivedi; Kaumudi Pandya (10-17).
Ni(II) sorption onto iron oxides and in particular hydrous ferric oxide (HFO) is among the important processes impacting its distribution, mobility, and bioavailability in environment. To develop mechanistic models for Ni, extended X-ray absorption fine structure (EXAFS) analysis has been conducted on Ni(II) sorbed to HFO. Coprecipitation revealed the formation of the metastable α-Ni(OH)2 at a Ni(II) loading of 3.5 × 10 −3   mol g −1 . On the other hand, Ni(II) formed inner-sphere mononuclear bidentate complexes along edges of FeO6 octahedra when sorbed to HFO surfaces with Ni–O distances of 2.05–2.07 Å and Ni–Fe distances of 3.07–3.11 Å. This surface complex was observed by EXAFS study over 2.8 × 10 −3 to 10−1 ionic strength, pH from 6 to 7, a Ni(II) loading of 8 × 10 −4 to 8.1 × 10 −3   mol g −1 HFO, and reaction times from 4 hours to 8 months. The short- and long-range structure analyses suggest that the presence of Ni(II) inhibited transformation of the amorphous iron oxide into a more crystalline form. However, Ni2+ was not observed to substitute for Fe3+ in the oxide structure. This study systematically addresses Ni(II) adsorption mechanisms to amorphous iron oxide. The experimentally defined surface complexes can be used to constrain surface complexation modeling for improved prediction of metal distribution at the iron oxide/aqueous interface.Ni K-edge χ ( k ) × k 3 spectra of Ni–HFO sorption complexes as a function of pH, IS, adsorbate loading, and reaction time studied at room temperature.
Keywords: Nickel; Adsorption; Hydrous ferric oxide; Amorphous oxide; EXAFS;

Adsorption of polyaromatic hydrocarbons on single wall carbon nanotubes of different functionalities and diameters by Suzana Gotovac; Cheol-Min Yang; Yoshiyuki Hattori; Kunimitsu Takahashi; Hirofumi Kanoh; Katsumi Kaneko (18-24).
Adsorption from toluene solution of phenanthrene and tetracene on single wall carbon nanotubes (SWCNT) is measured. Comparison of adsorbents such as laser ablation and HipCO samples reveals multiple factors influencing the adsorption mechanism. Acid functionalized carbon nanotubes have shown markedly increased adsorbability for the polyaromatic molecules. The linear tetracene molecule's adsorption is more promoted on nanotubes with increasing diameter, but also additionally with presence of the carboxylic groups. The adsorption mechanisms on carboxylic sites and on the bold, non-functionalized large-diameter nanotubes are suggested and supported by detailed characterization of the SWCNTs applied.
Keywords: Single wall carbon nanotubes; Polyaromatic hydrocarbons (PAH); Nanotubes functionalization; Adsorption from solution;

A natural zeolite was employed as adsorbent for removal of malachite green and Pb2+ ions from aqueous solution. A batch system was applied to study the adsorption behaviour of the dye and heavy metal in single and binary systems on the natural zeolite. Kinetic studies indicate that malachite green and Pb2+ adsorption on the natural zeolite in a single component system follows the first-order kinetics and the adsorption is diffusion process with single-stage for Pb2+ and two-stage for malachite green. For the single system, malachite green adsorption isotherm follows the Langmuir model while Pb adsorption follows the Freundlich isotherm. The adsorption capacities of malachite green and Pb at 30 °C, pH 6 are 5 × 10 −5 and 10 × 10 −5 mol / g , respectively. In the binary system, malachite green and Pb2+ exhibit competitive adsorption on the natural zeolite. The adsorption is reduced to 90 and 80% of single component of Pb2+ and malachite green, respectively. However, the total adsorption is higher. In the binary system, Pb2+ exhibits relative higher affinity and selectivity to be adsorbed on zeolite. The dynamic adsorption of malachite green and Pb2+ still follows the first-order kinetics.Adsorption of malachite green and Pb2+ on a natural zeolite in single and binary systems was investigated. The natural zeolite is effective in removal of malachite green and Pb2+ but malachite green and Pb2+ exhibit competitive adsorption in binary systems.
Keywords: Natural zeolite; Dye; Heavy metal; Competitive adsorption; Kinetics;

Mesoporous activated carbon samples were prepared from electrospun PAN-based carbon fibers using physical activation with silica. Textural characterization was performed using nitrogen adsorption at 77 K. The BET specific surface area and pore size distribution of silica activated carbon materials were investigated. According to the increment of silica, BET specific surface area was increased about thirty times and it was found that silica activated carbon materials were highly mesoporous by studying pore surface distribution and pore volume distribution. Surface morphology of silica activated carbon materials were observed by SEM images. The spherical typed carbon materials were investigated. The diameter of spherical typed carbon materials was increased in proportional of the increment of silica.Isotherms of electrospun activated carbon materials.
Keywords: PAN; Silica; Electrospinning; Physical activation; Activated carbon; Pore; EDLC;

n-Propylpyridinium chloride-modified poly(dimethylsiloxane) elastomeric networks: Preparation, characterization, and study of metal chloride adsorption from ethanol solutions by Fábio L. Pissetti; Herica A. Magosso; Inez V.P. Yoshida; Yoshitaka Gushikem; Sergiy O. Myernyi; Yuriy V. Kholin (38-45).
An n-propylpyridinium chloride-modified PDMS elastomeric network, PDMS/Py+Cl, was prepared from linear PDMS chains containing Si(CH3)2 ―OH end-groups cross-linked by 3-chloropropyltrimethoxysilane and posterior reaction with pyridine. PDMS/Py+Cl material was structurally characterized by infrared spectroscopy (IR) and solid state 13C and 29Si NMR. Thermogravimetric analysis of the product showed good thermal stability, with the initial temperature of weight loss at 450 K. The ion-exchange capacity of the PDMS/Py+Cl was 0.65 mmol g−1. Metal halides, MCl z [M = Fe3+, Cu2+, and Co2+], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes MCl z + n n − . The nature of the anionic complex structure was proposed by UV–vis diffuse reflectance spectra. The species adsorbed were FeCl 4, CuCl2− 4, and CoCl2− 4. The specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. The trend in affinities of PDMS/Py+Cl for the metal halides were found to be FeCl3  > CuCl2  ∼ CoCl2.An n-propylpyridinium chloride-modified PDMS elastomeric network was prepared by reacting 3-chloropropyltrimethoxysilane and poly(dimethylsiloxane), followed by addition of pyridine.
Keywords: Poly(dimethylsiloxane); n-Propylpyridinium chloride; Elastomeric network; Metal adsorption; Stability constants;

This paper reports that a new SERS-active silver film on the surfaces of a series of electric material has been prepared by an electrochemical technique in an aqueous solution of AgNO3. With scanning electron microscopy, the morphology of the silver film is a treelike structure. By SERS measurements, the film of silver dendrites is shown to be an excellent substrate, demonstrating significant enhancement effect, spatial uniformity and good stability. As the fabrication process of this substrate is very simple and inexpensive, it is proposed that this method may be used in large-scale preparation of substrates that have been widely applied in Raman analysis.
Keywords: Surface-enhanced Raman scattering (SERS); Silver dendrites; SEM; XRD;

This work presents atomic force microscopy (AFM) measurements of adhesion forces between polyamides, polystyrene and AFM tips coated with the same materials. The polymers employed were polyamide 6 (PA6), PA66, PA12 and polystyrene (PS). All adhesion forces between the various unmodified or modified AFM tips and the polymer surfaces were in the range −1.5 to − 8  nN . The weakest force was observed for an unmodified AFM tip with a PS surface and the strongest was between a PS-coated tip and PS surface. The results point to both the benefits and drawbacks of coated-tip AFM force–distance measurements. Adhesion forces between the two most dissimilar (PA6–PS and PA66–PS) materials were significantly asymmetric, e.g., the forces were different depending on the relative placement of each polymer on the AFM tip or substrate. Materials with similar chemistry and intermolecular interactions yielded forces in close agreement regardless of placement on tip or substrate. Using experimental forces, we calculated the contact radii via four models: Derjaguin, Muller, and Toporov; Johnson, Kendall, and Roberts; parametric tip–force–distance relation; and a square pyramid–flat surface (SPFS) model developed herein. The SPFS model gave the most reasonable contact tip radius estimate. Hamaker constants calculated from the SPFS model using this radius agreed in both magnitude and trends with experiment and Lifshitz theory.This work presents AFM measurements of adhesion forces between polyamides, polystyrene and AFM tips coated with the same materials. The results point to both the benefits and drawbacks of coated-tip AFM force–distance measurements. Experimental data are used to compare four models for calculating Hamaker constants.
Keywords: Adhesion; AFM; Polyamide; Nylon; Van der Waals; Intermolecular force;

Interfacial properties as predictors of radioresistance in cervical cancer by Preetha Anand; Nagraj Huilgol; Rinti Banerjee (63-70).
The prediction of radioresistance of tumours, early in the course of radiotherapy, may help clinicians in deciding the optimal treatment strategy for each case. This study was carried out to investigate an in vitro technique to predict radiosensitivity, after a single radiation dose of 2 Gy in cervical cancer. Langmuir films of tissue homogenates of biopsy samples from 20 cervical cancer patients treated with radiotherapy alone and 15 normal controls were evaluated. The tensiometric profiles before and after giving 2 Gy of radiation, were compared with that of controls and were correlated with the clinical radioresponsiveness evaluated on completion of the radiotherapy course of 70–78 Gy over a period of 50–55 days. The tensiometric profiles measured after a single dose of radiation can be used to fingerprint the clinical radioresponsiveness of the cervical cancer tissues. The hysteresis of the monolayers of completely radioresponsive post-radiotherapy tissue homogenates was 5.8 times greater than that of partially radioresponsive post-radiotherapy tissue homogenates and was statistically significant using Mann–Whitney test ( p < 0.05 ). From our results, the following tensiometric criteria for prediction of radioresistance emerge. After first dose of radiation, if the minimum surface tension of tissue homogenate is greater than 50 mN/m and hysteresis area is less than 20 μJ those tissues will be in the partially radioresponsive and for completely radioresponsive tissue homogenates, the minimum surface tension will be less than 47 mN/m and the hysteresis area will be greater than 33 μJ. The cholesterol and phospholipid content of radioresponsive cervical cancerous tissues after radiotherapy was found to be 1.2 and 2.2 times lower than that of the untreated tissues and due to lower lipid content organic phase surface activity of radioresponsive cancerous tissues after radiotherapy was less than that of the untreated tissue organic phase. The radiation induced tensiometric profile changes of radioresponsive cervical cancerous tissues can be correlated to the radiation induced lipid profile changes. This technique, due to its simplicity and high precision, can serve as a predictive tool for radioresponsiveness and is easily translatable to the clinical setting. Randomized large sample trials are necessary to validate this technique further and help in the translation from bench to clinics.Surface pressure–area isotherms of tissue homogenate monolayers predict the radioresponsiveness of cervical cancer tissues.
Keywords: Tissue monolayer; Surface pressure–area isotherm; Hysteresis; Cervical cancer; Minimum surface tension; Radioresponsiveness;

Microcontact printing of Concanavalin A and its effect on mammalian cell morphology by Tamal Das; Sanjaya K. Mallick; Debashish Paul; Sujit K. Bhutia; Tarun K. Bhattacharyya; Tapas K. Maiti (71-79).
In this study a major lectin called Concanavalin A (ConA) has been micropatterned on a glass substrate by microcontact printing and the patterns have been characterized with fluorescent and atomic force microscope for their uniformity. Interaction of the patterns with mammalian cells has been investigated by culturing L929 mouse fibroblast cells on the ConA printed glass surface. Cell culture results obtained from the microcontact printed patterns have also been compared and benchmarked with another patterning technique named micromolding in capillaries (MIMIC). It has been revealed that in spite of molecular level heterogeneity and agglomeration of protein molecules in microcontact printed form, they can still interact with cell surface glycoproteins, impede the mobility of membrane receptor which results in altered morphology of the fibroblast cells.A major lectin, Concanavalin A, in microcontact printed form on a glass substrate, has been shown to alter the morphology of mouse fibroblast cells.
Keywords: Microcontact printing; Micromolding in capillaries; Concanavalin A; Lectins; Cell morphology;

Covalently linked DNA/protein multilayered film for controlled DNA release by Zhisong Lu; Chang Ming Li; Qin Zhou; Qiao-Liang Bao; Xiaoqiang Cui (80-88).
A stable, biocompatible single strand DNA (ssDNA)/bovine serum albumin (BSA) multilayered film for control release of DNA was fabricated on PEI-coated quartz slides, gold-evaporated plates and silicon wafers, respectively through a formaldehyde-induced, covalently linked layer-by-layer (LBL) assembly technique. The constructed film structure was well characterized by using UV–vis spectrometry, surface plasmon resonance (SPR) and atomic force microscopy (AFM). The results showed that the DNA incorporated LBL film was fabricated successfully and the amount of ssDNA and BSA in the film could be tailored simply by controlling the number of the bilayers. The control release of DNA from the film was also monitored in this study. UV–vis spectrometry, SPR and AFM measurements indicated that the release of ssDNA and amino acid was adjustable by changing the proteinase K incubation time. This biocompatible covalently assembled film demonstrates an innovative approach to engineer a DNA/protein based nanostructure for controlled DNA release, which could provide stability, controllability and flexibility superior to that of LBL film assembled by electrostatic attraction. Since the film in this work can be assembled on different substrates, it is very feasible to fabricate nanoparticle-based gene therapy systems with this new approach and to have great potential in biomedical applications.
Keywords: Covalent bonding; Layer-by-layer; Control release; DNA; Gene therapy;

Reduction of an azo dye Acid Black 24 solution using synthesized nanoscale zerovalent iron particles by Hung-Yee Shu; Ming-Chin Chang; Hsing-Hung Yu; Wang-Hung Chen (89-97).
The strong color and high total organic carbon (TOC) of laboratory-synthesized azo dye, C.I. Acid Black 24 (AB24), solution was substantially reduced with particles of chemically synthesized nanoscale zerovalent iron (NZVI) under varied conditions of experimental variables such as NZVI dosage, initial dye concentration, and pH. From the results, the synthesized NZVI particles can effectively remove color and TOC of AB24 dye solution under certain conditions. The best removal efficiencies for color and TOC were obtained as 98.9 and 53.8%, respectively, with an initial dye concentration of 100 mg L−1 and an NZVI dosage of 0.3348 g L−1. Additionally, the removal rates followed an empirical rate equation with respect to the initial dye concentration as well as the NZVI dosage. The NZVI dosage addition exponentially increments the removal efficiency, with observed empirical reaction rate constants (k) of 0.046–0.603 min−1 for added NZVI of 0.0335–0.3348 g L−1. Moreover, the largest unit removal capacity was 609.4 mg of AB24 uptake for each gram of NZVI (i.e., 609.4 mg AB24/g NZVI). Ultimately, the ideal operation conditions were 0.1674–0.3348 g L−1 of NZVI dosage, 15–30 min of reaction time, and pH 4–9 for 25–100 mg L−1 of initial dye concentration.The synthesized zerovalent iron nanoparticles (NZVI) were utilized to reductive decolorize an azo dye Acid Black 24 solution in 100 mg L−1 concentration with fairly good removal efficiencies under various NZVI dosages.
Keywords: Decolorization; Azo dye; Synthesized; Nanoscale; Zerovalent iron; NZVI;

We report an experimental method to characterize the dynamics of colloidal rods by measuring their rotation and translation in three dimensions with confocal microscopy. The method relies on solvent viscosification to retard dynamics to time scales that are compatible with 3D confocal optical microscopy. Because the method yields a full three-dimensional characterization of rod displacement and orientation, it is applicable to situations in which complex, anisotropic dynamics emerge. Examples include behavior in liquid crystal phases with both orientational and positional order, suspensions subjected to applied fields such as shear flow or sedimentation, and the emerging area of anisotropic particle dynamics. We demonstrate the performance of the method by quantifying the Brownian motion of fluorescent poly(methyl methacrylate) rods (aspect ratio, L / D = 3.1 and 7.0) grafted with poly(dimethylsiloxane) stabilizer. The rods are dispersed at dilute concentration in a solvent mixture of viscosity 2.0 Pa s. Rod translational and rotational diffusivities are extracted from the measured translational mean square displacement of the centroid positions and of the rod unit vector u ( t ) , respectively. Rod orientational dynamics are characterized relative to both their azimuthal and polar angles. Probability distributions for the translation and rotation in the frame of rod are computed from the measurements. Experimental values obtained agree well with theory available for the dynamics of isolated rods.We quantify the translational and rotational diffusion of prolate spheroid colloidal rods by 3D direct visualization of displacement and orientation by confocal microscopy.
Keywords: Colloidal rods; Rotational diffusivity; Translational diffusivities; Brownian motion; Probability distribution function; Confocal microscopy;

Adsorption of humic acids onto goethite: Effects of molar mass, pH and ionic strength by Liping Weng; Willem H. Van Riemsdijk; Tjisse Hiemstra (107-118).
In this paper, the LCD (ligand charge distribution) model is applied to describe the adsorption of (Tongbersven) humic acid (HA) to goethite. The model considers both electrostatic interactions and chemical binding between HA and goethite. The large size of HA particles limits their close access to the surface. Part of the adsorbed HA particles is located in the compact part at the goethite surface (Stern layers) and the rest in the less structured diffuse double layer (DDL). The model can describe the effects of pH, ionic strength, and loading on the adsorption. Compared to fulvic acid (FA), adsorption of HA is stronger and more pH- and ionic-strength-dependent. The larger number of reactive groups on each HA particle than on a FA particle results in the stronger HA adsorption observed. The stronger pH dependency in HA adsorption is related to the larger number of protons that are coadsorbed with HA due to the higher charge carried by a HA particle than by a FA particle. The positive ionic-strength dependency of HA adsorption can be explained by the conformational change of HA particles with ionic strength. At a higher ionic strength, the decrease of the particle size favors closer contact between the particles and the surface, leading to stronger competition with electrolyte ions for surface charge neutralization and therefore leading to more HA adsorption.Using the LCD model, the effects of molar mass, pH, and ionic strength on the adsorption of humic substances onto mineral surfaces can be better understood.
Keywords: LCD; CD-MUSIC; NICA; ADAPT; Humic acid adsorption; Humic; Fulvic; Iron (hydr)oxides; Variable-charge particles;

Surface structure and properties of mixed fumed oxides by V.M. Gun'ko; J.P. Blitz; K. Gude; V.I. Zarko; E.V. Goncharuk; Y.M. Nychiporuk; R. Leboda; J. Skubiszewska-Zięba; V.D. Osovskii; Y.G. Ptushinskii; O.A. Mishchuk; S.V. Pakhovchishin; P.P. Gorbik (119-130).
A variety of fumed oxides such as silica, alumina, titania, silica/alumina (SA), silica/titania (ST), and alumina/silica/titania (AST) were characterized. These oxides have different specific surface areas and different primary particle composition in the bulk and at the surface. These materials were studied by FTIR, NMR, Auger electron spectroscopy, one-pass temperature-programmed desorption with mass spectrometry control (OP TPDMS), microcalorimetry, and nitrogen adsorption. Nonlinear changes in the surface content of alumina in SA and AST and titania in ST and AST samples with increasing oxide content along with simultaneous changes in their specific surface area cause complex dependencies of the heat of immersion in water and desorption of water on heating on the structural parameters. Simultaneous analysis of changes in the surface phase composition, in the concentration of hydroxyls, and in the structural characteristics reveals that at a low content of the second phase the structural characteristics (e.g., S BET ) are predominant; however, at a large content of these oxides the phase composition plays a more important role.Analysis of the surface phase composition, concentration of hydroxyls, and changes in the structural characteristics of mixed nanooxides reveals that at a low content of titania or alumina the structural characteristics are predominant; however, at a large content of these oxides the phase composition plays a more important role.
Keywords: Fumed silica; Fumed alumina; Fumed titania; Fumed mixed oxides; Surface composition; Structural characteristics; Heat of immersion; CP/MAS 29Si NMR spectra; MAS 27Al NMR spectra; FTIR;

When a solid substrate with negative surface charges was placed in an aqueous didodecyldimethylammonium bromide (DDAB) vesicle dispersion, the cationic surfactant DDAB with two hydrocarbon chains could be assembled into the biomembrane-like tail-to-tail double-layer structure on the solid surface with the positively charged head groups toward outside, making the surface charge reverse from negative to positive. After the solid substrate with DDAB was immersed in a hemoglobin (Hb) solution at pH 9.0, the negatively charged Hb was adsorbed on the surface of DDAB layer by electrostatic attraction, forming a DDAB/Hb film. By repeating this adsorption cycle, the {DDAB/Hb} n layer-by-layer films were assembled on solid surfaces, which was confirmed by UV–vis spectroscopy, quartz crystal microbalance (QCM), and cyclic voltammetry (CV). The stable {DDAB/Hb} n films assembled on pyrolytic graphite (PG) electrodes showed two pairs of nearly reversible redox peaks at about −0.22 and − 1.14   V vs SCE in pH 7.0 buffers, characteristic of the Hb heme Fe(III)/Fe(II) and Fe(II)/Fe(I) redox couples, respectively. The direct electrochemistry of Hb in the films could be used to electrocatalyze reduction of various substrates. UV–vis and IR spectroscopic results and comparison experiments with {DDAB/hemin} n films indicate that Hb in the {DDAB/Hb} n films essentially retains its native structure. Atomic force microscopy (AFM) was used to characterize the morphology of the films with different outermost layers.
Keywords: Hemoglobin; Didodecyldimethylammonium bromide; Layer-by-layer assembly; Direct electrochemistry; Electrocatalysis;

Polymerization of lauryl methacrylate “to” and “from” the surface of montmorillonite platelets was studied under a range of different reaction conditions. The polymerization was performed in order to achieve better organic coverage of the platelets, thus facilitating their exfoliation in the polymer matrices. For polymerization “to” the surface, a methacrylic functionality was first generated on the clay surface which was subsequently polymerized with the external lauryl methacrylate monomer. Substantial amounts of the polymer could be attached to the surface when lower polymerization temperatures and longer reaction times were used. Bulk polymerization was more effective in increasing the amount of polymer mass on the surface. In order to achieve polymerization “from” the surface, a bicationic initiator was first ionically bound on the surface followed by polymerization with lauryl methacrylate. Under the nonliving conditions, however, no significant amount of polymer could be grown from the surface. Nitroxide-mediated living polymerization was successful in eliminating suspected termination reactions leading to substantial gains in the organic mass bound to clay surfaces. Care was taken to avoid the presence of excess of unbound ammonium ions which can interfere in the grafting of polymer chains on the surface. X-ray diffraction and transmission electron microscopy in conjunction with thermogravimetric analysis confirmed the grafting of the polymer chains on the surface.
Keywords: Free radical polymerization; Montmorillonite; Grafting; Cation exchange; Exfoliation; Nitroxide;

Differential electrochemical mass spectrometry (DEMS) was used to investigate the electrocatalytic hydrogenation and oxidation of benzene and p-dihydroxybenzene (hydroquinone, H2Q) chemisorbed on ultrathin Pd films electrodeposited at Au(332) and Au(111) surfaces. At low sub-monolayer coverages on Au(332), the Pd ad-atoms preferentially adsorb on the step sites. At higher (but still sub-monolayer) coverages, Pd also occupies terrace sites; on Au(111), only terrace sites are available. The electrochemical reactivities of the subject compounds at the Pd-decorated steps and terraces were then compared. No hydrogenation products were detected by DEMS for either benzene or H2Q, but a considerable degree of electrodesorption of (intact) benzene occurred near the hydrogen-evolution region (HER). Anodic oxidation of both compounds yielded only CO2 as the volatile (DEMS-detectable) product, although it took up to three anodic cycles to attain exhaustive (complete) oxidation. The anodic oxidation of benzene was also accompanied by potential-induced desorption of (unreacted) benzene particularly in the case of the stepped surface. Electrodesorption at the HER was more facile at the terrace sites than from the step sites; the opposite was true for electrodesorption at the more positive potential. Contrary to hydrogen, which does not adsorb at such monoatomic rows, both aromatic species adsorb when the nominal Pd coverage just corresponds to step decoration.Anodic oxidation of chemisorbed hydroquinone yielded CO2 as the only DEMS-detectable product. No hydrogenation products for benzoquinone could be identified by DEMS. For benzene, a considerable fraction of starting material was electrodesorbed near the hydrogen-evolution region.
Keywords: Electrocatalytic hydrogenation of aromatic compounds; Anodic oxidation of aromatic compounds; Ultrathin palladium films; Pd-modified Au(hkl) surfaces; Differential electrochemical mass spectrometry;

Grafting of poly(methyl vinyl ketone) onto aluminum surface by Fabienne Barroso-Bujans; José L.G. Fierro; Michael Veith (160-166).
Polymers were grafted on aluminum surfaces in order to modify the chemical and physical properties of the interface. The properly cleaned and activated surface of the aluminum substrate was first “silanized” either with 3-(trimethoxysilyl)propylamine or allyltrimethoxysilane. The grafting was carried out following two methods: (i) by the reaction of preformed poly(methyl vinyl ketone) with the aminosilane-modified surface; and (ii) by polymerization of methyl vinyl ketone with the vinylsilane-modified surface. The modified aluminum surfaces were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The new surfaces were examined by contact-angle measurements, and determinations of the Lewis basicity.Grafting of poly(methyl vinyl ketone) on amino- and vinyl-modified aluminum surfaces was performed.
Keywords: Poly(methyl vinyl ketone); Grafting on aluminum; X-ray photoelectron spectroscopy; Contact angle;

Enhanced desorption of hexachlorobenzene from kaolin by single and mixed surfactants by Songhu Yuan; Zhu Shu; Jinzhong Wan; Xiaohua Lu (167-175).
This study investigated the enhanced desorption of hexachlorobenzene (HCB) from spiked kaolin by single and mixed surfactants. The sorption of surfactants on kaolin followed myristyl pyridinium bromide (MPB) > Tween 80 > sodium dodecyl benzene sulfonic (SDBS). The desorption of HCB by single surfactant increased linearly with the increase of the aqueous micelle concentrations. The potential to enhance HCB desorption was Tween 80 > SDBS > MPB. When the dual mixed surfactants of SDBS–Tween 80 (MPB–Tween 80) were present, the desorption of HCB was larger than that by single SDBS (MPB) and less than that by single Tween 80. The total adsorbed surfactants were kept almost constant in SDBS–Tween 80 but decreased with the increased fraction of Tween 80 above 0.5 in MPB–Tween 80. The presence of little MPB in Tween 80 highly reduced the sorption loss of Tween 80 but slightly decreased the desorption of HCB. Whereas in SDBS–MPB, the presence of little MPB in SDBS remarkably decreased the desorption of HCB and enhanced the loss of SDBS, while the addition of little SDBS in MPB significantly enhanced the desorption and reduced the loss of MPB.Cationic–nonionic mixed surfactants can reduce the surfactants sorption loss with the simultaneous enhancement on the desorption of hexachlorobenzene from soils.
Keywords: Desorption; Hexachlorobenzene; Mixed surfactants; Surfactant distribution; Soil remediation;

Synthesis and characterization of mesoporous silica from selectively acid-treated saponite as the precursors by Kiyoshi Okada; Hisako Yoshizaki; Yoshikazu Kameshima; Akira Nakajima; Chengala D. Madhusoodana (176-183).
Mesoporous silicas were synthesized by hydrothermal treatment of selectively acid-treated saponite (an ideal structural formula: Na1/3Mg3(Si11/3Al1/3)O10(OH)2), having a 2:1 type layered structure as the silica source and its porous properties were examined and compared with that from kaolinite (an ideal structural formula: Al2Si2O5(OH)4), having a 1:1 type layered structure. Synthetic saponite was selectively leached in H2SO4 solutions with various concentrations (0.05–1 M) at 70 °C for 0.5 h. The resulting products (precursors) were mixed with cetyltrimethylammonium bromide (CTABr), NaOH and H2O, hydrothermally treated at 110 °C and removed the CTABr by calcining at 560 °C. A hexagonal mesoporous phase was obtained with higher Si/(Al(+Mg)) ratios of the resulting precursors. The XRD patterns of these products show the peaks assigned by a hexagonal lattice with a 0 = 4.0 – 4.6   nm and the crystallinity becomes higher with higher Si/(Al(+Mg)) ratios of the precursors. The specific surface area ( S BET ) values of the present mesoporous silicas range from 800 to 1100 m2/g at CTABr/precursor = 0.1 and although they are not as high as those from precursors prepared from calcining and acid-treatment of kaolinite (1420 m2/g), they are increased to 1400–1500 m2/g by increasing the ratio CTABr/precursor ⩾0.2. The reason for the difference in the optimum preparation conditions between saponite and kaolinite may be attributed to the difference in the linkage of the SiO4 tetrahedra in these precursors (i.e. layered or framework structures), which result in great differences in the selective leaching rates and structures of the resulting silica-rich products.Mesoporous silicas prepared from selectively acid-treated saponite, Na1/3Mg3(Si11/3Al1/3)O10(OH)2 used as a silica source show high specific surface area up to about 1500 m2/g.
Keywords: Mesoporous silica; Saponite; Acid-treatment; Cethyltrimethylammonium bromide;

The interface shape separating a gas layer within a superhydrophobic surface consisting of a square lattice of posts from a pressurized liquid above the surface is computed numerically. The interface shape is described by a constant mean curvature surface that satisfies the Young–Laplace equation with the three-phase gas–liquid–solid contact line assumed pinned at the post outer edge. The numerical method predicts the existence of constant mean curvature solutions from the planar, zero curvature solution up to a maximum curvature that is dependent on the post shape, size and pitch. An overall force balance between surface tension and pressure forces acting on the interface yields predictions for the maximum curvature that agree with the numerical simulations to within one percent for convex shapes such as circular and square posts, but significantly over predicts the maximum curvature for non-convex shapes such as a circular post with a sinusoidal surface perturbation. Changing the post shape to increase the contact line length, while maintaining constant post area, results in increases of 2 to 12% in the maximum computable curvature for contact line length increases of 11 to 77%. Comparisons are made to several experimental studies for interface shape and pressure stability.Calculated interface shape between four adjacent posts in a square lattice of cylindrical posts.
Keywords: Superhydrophobic surface; Pressure stability; Interfacial shape; Constant mean curvature surface; Lagrangian evolution equation; Static contact line; Overall force balance;

This paper shows how 2 coupled Young–Laplace equations can be solved to predict the shapes of two coupled menisci formed in a capillary system. Experiments are performed, which demonstrate that the equilibrium volume of liquid retained in a vertical capillary, can be variable, even when all the properties of the system are invariant. This variability in liquid retention also leads to different equilibrium shapes of the top and bottom menisci. A coupled form of the Young–Laplace equation is solved to predict the two coupled menisci shapes. The curvature of the top meniscus is fitted to the experimentally recorded meniscus shape. The coupled Young–Laplace equation solution is used to predict the shape of the bottom meniscus. The shape of the bottom meniscus thus obtained, is shown to match the experimentally recorded bottom meniscus shape reasonably well. This observed coupling of the menisci has a significant impact on some porosimetric techniques which are based on liquid extrusion and explains why the volume of liquid that can be retained in a capillary can vary, under invariant conditions. Retention of liquids in capillaries is of interest in several applications like fabric wash.This paper shows how 2 coupled Young–Laplace equations can be solved to predict the shapes of two coupled menisci formed in a capillary system. The curvature of the top meniscus is fitted to the experimentally recorded meniscus shape. The coupled Young–Laplace equation solution is used to predict the shape of the bottom meniscus. The shape of the bottom meniscus thus obtained, is shown to match the experimentally recorded bottom meniscus shape reasonably well.
Keywords: Liquid retention; Capillary retention; Capillary rise; Capillary meniscus; Meniscus shapes; Young–Laplace equation;

Liquid transport in a multi-layer froth by Peter M. Ireland; Graeme J. Jameson (207-213).
When a gas is sparged into an aqueous solution of surfactant in a column, a froth layer is formed above the layer of liquid. If water is injected into the rising column of froth at a particular position, two distinct layers are formed in the froth: a wet layer below the injection plane, and a dry layer above it. In this study, a phase coexistence analysis was performed on the three-layer system. Predictions from the governing drift-flux equation were compared, using two different representations of the drainage terms, which had one and two adjustable parameters, respectively. The analysis was used to predict liquid fractions and superficial liquid velocities for the wet and dry froth zones. These were compared to experimental measurements performed with a laboratory froth column. Both versions of the analysis were in good agreement with experiment. That with the single-parameter drainage term (derived from the Richardson–Zaki equation) was marginally superior. Theoretical predictions of the liquid fraction and overflow rate from the dry froth layer are supported by the data. Considerable convective motions were observed in the wet froth layer, driven by differences in density between the entering wash liquid and the surrounding froth.When water is injected into a froth, the liquid fraction ε L below the injection site increases with wash water superficial velocity J L W , while that above remains constant. ε L and drainage superficial velocity J L d were consistent with theoretical predictions for various superficial gas velocities J g .
Keywords: Froths; Foams; Froth flotation; Wash water; Foam drainage;

Mixtures of Zn(II) and 8-hydroxyquinoline (8QOH) in a 1:2 proportion, in aqueous solutions, result in fast complexation, followed by precipitation. Addition of 0.05 M sodium dodecyl sulfate (SDS), N-dodecyl- N , N -dimethylammonio-1-propanesulfonate (SB3-12), N-hexadecyl- N , N -dimethylammonio-1-propanesulfonate (SB3-16) or Triton X-100 results in considerable retardation of precipitation. In the presence of SDS, SB3-12, SB3-16 and Triton X-100 the 8QOH chelates are only kinetically stable in solution and after 24 h, the precipitation is almost quantitative. Conversely, upon addition of the cationic surfactant hexadecyltrimethylammonium bromide (CTABr), the absorbance of the complex remains constant even after at least six months. The interaction of the ligand 8QOH (and of the (8QO)2Zn(II) complex) with the cationic surfactant was studied by ultraviolet and NMR spectroscopy and 8QOH has a p K a = 9.05 in the presence of the cationic surfactant and the ligand intercalates in the micelle, being preferentially located near the headgroup of the micelle. Although the solubilization site of the (8QO)2Zn(II) complex is similar to that of 8QOH, the interaction of the aromatic moiety with the CTA+ headgroup is much stronger, due to the increased electron density in the aromatic ring of the ligand. As a consequence of this interaction, sphere to rod transition and an increase in microscopic and macroscopic viscosity are observed.
Keywords: Micelles; Fluorescence; 8-Hydroxyquinoline; NMR; Viscosity;

Short haired wormlike micelles in mixed nonionic fluorocarbon surfactants by Suraj Chandra Sharma; Carlos Rodríguez-Abreu; Lok Kumar Shrestha; Kenji Aramaki (223-229).
We have studied the rheological behavior of viscoelastic wormlike micellar solution in a mixed system of nonionic fluorinated surfactants, perfluoroalkyl sulfonamide ethoxylate, C8F17SO2N(C3H7)(CH2CH2O) n H abbreviated as C8F17EO n ( n = 10 and 20). Above critical micelle concentration, the surfactant, C8F17EO20 forms small spherical micelles in water and the viscosity of the solution remains constant regardless of the shear rate, i.e., the solutions exhibit Newtonian behavior. However, upon successive addition of the C8F17EO10 the viscosity of the solution increases and at certain C8F17EO10 concentration, shear-thinning behavior is observed indicating the formation wormlike micelles. Contrary to what is expected, there is a viscosity increase with the addition of the hydrophilic C8F17EO20 to C8F17EO10 aqueous solutions at certain temperature and concentration, which could be attributed to an increase in rigidity of the surfactant layer and to the shifting of micellar branching to higher temperatures. The oscillatory-shear rheological behavior of the viscoelastic solution can be described by Maxwell model at low frequency. Small-angle X-ray scattering (SAXS) measurements confirmed the formation of small spherical micellar aggregates in the dilute aqueous C8F17EO20 solution. The SAXS data shows the one-dimensional growth on the micellar size with increase in the C8F17EO10 concentration. Thus, the present SAXS data supports the rheological data.
Keywords: Fluorocarbon surfactants; Oligomers; Wormlike micelles; Rheological behavior; Small-angle X-ray scattering;

Oil-in-water nanoemulsions for pesticide formulations by Lijuan Wang; Xuefeng Li; Gaoyong Zhang; Jinfeng Dong; Julian Eastoe (230-235).
A two-step process for formation of nanoemulsions in the system water/poly(oxyethylene) nonionic surfactant/methyl decanoate at 25 °C is described. First, all the components were mixed at a certain composition to prepare a microemulsion concentrate, which was rapidly subjected into a large dilution into water to generate an emulsion. Bluish transparent oil-in-water (O/W) nanoemulsions were formed only when the concentrate was located in the bicontinuous microemulsion (BC) or oil-in-water microemulsion (Wm) region. The existence of an optimum oil-to-surfactant ratio ( R os ) in the BC or Wm region indicates that both the phase behavior and the composition of the concentrate are important factors in nanoemulsion formation. To demonstrate potential applications of these systems, they were employed to formulate a water-insoluble pesticide, β-cypermethrin (β-CP). The nanoemulsion was compared with a commercial β-CP microemulsion in terms of the stability of sprayed formulations.A two-step process for formation of nanoemulsions in the system water/poly(oxyethylene) nonionic surfactant/methyl decanoate at 25 °C is described. The droplet sizes of the resulting nanoemulsions were strongly affected by the final water concentration after dilution of the initial concentrate. Bluish transparent oil-in-water (O/W) nanoemulsions were formed only when the concentrate was located in the bicontinuous microemulsion (BC) or oil-in-water microemulsion (Wm) region.
Keywords: Nanoemulsion; Equilibrium phase behavior; Pesticide formulation;

Electrical conductivity was measured for aqueous solutions of long-chain imidazolium ionic liquids (IL), 1-alkyl-3-methylimidazolium bromides with C12–C16 alkyl chains. The break points appeared in specific conductivity (κ) vs concentration (c) plot indicates that the molecular aggregates, i.e., micelles, are formed in aqueous solutions of these IL species. The critical micelle concentration (cmc) determined from the κ vs c plot is somewhat lower than those for typical cationic surfactants, alkyltrimethylammonium bromides with the same hydrocarbon chain length. The electrical conductivity data were analyzed according to the mixed electrolyte model of micellar solution, and the aggregation number, n, and the degree of counter ion binding, β, were estimated. The n values of the present ILs are somewhat smaller than those reported for alkyltrimethylammonium bromides, which may be attributed to bulkiness of the cationic head group of the IL species. The thermodynamic parameters for micelle formation of the present ILs were estimated using the values of cmc and β as a function of temperature. The contribution of entropy term to the micelle formation is superior to that of enthalpy term below about 30 °C, and it becomes opposite at higher temperature. This coincides with the picture drawn for the micelle formation of conventional ionic surfactants.▪
Keywords: Long-chain imidazolium ionic liquids; Electrical conductivity; Micelle formation; Critical micelle concentration (cmc); Mixed electrolyte model; Thermodynamic parameters of micelle formation;

Interaction between pentaethylene glycol n-octyl ether and poly(acrylic acid): Effect of the polymer molecular weight by Gerardino D'Errico; Donato Ciccarelli; Ornella Ortona; Luigi Paduano; Roberto Sartorio (242-250).
The effect of the polymer molecular weight on the interaction between pentaethylene glycol n-octyl ether (C8E5) and poly(acrylic acid) (PAA) has been investigated by a combined experimental strategy including tensiometry, potentiometry, calorimetry, fluorescence quenching and intradiffusion (pulsed gradient spin echo-NMR) measurements. PAA samples with an average molecular weight varying in a wide range ( M ¯ w = 2000 , 100,000, 250,000, and 450,000) have been considered. The measurements have been performed at constant polymer concentration (0.1% w/w) with varying surfactant molality. In all the considered systems, at low surfactant concentration, adsorption of surfactant monomers onto the polymer chain has been detected. At a C8E5 molality ( T 1 ) independent of the PAA M ¯ w , surfactant molecules start to aggregate, forming clusters to which the polymer co-participates. Above this concentration, the behavior of the system depends on M ¯ w . In fact, if polymer samples with high molecular weight ( M ¯ w ⩾ 100 , 000 ) are employed, all the added surfactant aggregates onto the polymer leading to the polymer saturation and, subsequently, to free micelles formation. Both saturation and free micellization occur at surfactant concentrations which are independent of the polymer molecular weight. C8E5 aqueous mixtures containing PAA with low molecular weight ( M ¯ w = 2000 ) behaves differently, in that, above T 1 , only a fraction ( ∼ 20 % ) of the added surfactant molecules interact with the polymer, forming aggregates to which more than one PAA chain participate. In this case, C8E5 free micellization occurs before polymer saturation. The experimental evidences have been interpreted in terms of the subtle balance between the various molecular interactions driving the surfactant–polymer aggregation.Nonionic ethoxylated surfactants and poly(acrylic acid) interact forming aggregates whose microstructure critically depends on the polymer molecular weight.
Keywords: Ethoxylated surfactants; Surfactant–polymer interaction; Tensiometry; Fluorescence quenching; Intradiffusion;

This work deals with the experimental observation of the shape oscillations followed by a viscous liquid drop immersed in another viscous fluid matrix when retracting from a deformed state into the spherical shape under the action of interfacial forces. The droplet is firstly deformed into an ellipsoidal shape by a shear flow and later allowed to recover the equilibrium shape after cessation of the flow. It is observed that such an oscillatory process occurs for a wide range of viscosity ratios and it may be described by a dampened oscillation. Viscous components dominate the drop retraction, just allowing few oscillations. The dampening factor, frequency and amplitude of the oscillations are affected by the drop viscosity. Frequencies and amplitudes are also influenced by the initial drop deformation.Dampening oscillation followed by a sheared liquid drop when retracting from a deformed shape.
Keywords: Droplet; Shape oscillation; Interfacial tension; Viscosity;

The boundary effect on electrophoresis is investigated by considering a spherical particle at an arbitrary position in a spherical cavity. Our previous analysis is extended to the case where the effect of double-layer polarization can be significant. Also, the effect of a charged boundary, which yields an electroosmotic flow and a pressure gradient, thereby making the problem under consideration more complicated, is investigated. The influences of the level of the surface potential, the thickness of double layer, the relative size of a sphere, and its position in a cavity on the electrophoretic behavior of the sphere are discussed. Some results that are of practical significance are observed. For example, if a positively charged sphere is placed in an uncharged cavity, its mobility may have a local minimum as the thickness of the double layer varies. If an uncharged sphere is placed in a positively charged cavity, the mobility may have a local minimum as the position of the sphere varies. Also, if the size of a sphere is fixed, its mobility may have a local minimum as the size of a cavity varies. These provide useful information for the design of an electrophoresis apparatus.Typical flow field for a positively charged sphere at the center of an uncharged spherical cavity.
Keywords: Electrophoresis; Boundary effect; Electroosmotic flow; Sphere in spherical cavity; Double-layer polarization;

Electroosmosis in homogeneously charged micro- and nanoscale random porous media has been numerically investigated using mesoscopic simulation methods which involve a random generation-growth method for reproducing three-dimensional random microstructures of porous media and a high-efficiency lattice Poisson–Boltzmann algorithm for solving the strongly nonlinear governing equations of electroosmosis in three-dimensional porous media. The numerical modeling and predictions of EOF in micro- and nanoscale random porous media indicate that the electroosmotic permeability increases monotonically with the porosity of porous media and the increasing rate rises with the porosity as well; the electroosmotic permeability increases with the average solid particle size for a given porosity and with the bulk ionic concentration also; the proportionally linear relationship between the electroosmotic permeability and the zeta potential on solid surfaces breaks down for high zeta potentials. The present predictions agree well with the available experimental data while some results deviate from the predictions based on the macroscopic theories.We perform full numerical modeling and analysis of electroosmosis in homogeneously charged nanoscale random porous media. The presented predictions agree well with the available experimental data while some results deviate from the predictions based on the macroscopic theories.
Keywords: Random porous media; Electroosmosis; Lattice Poisson–Boltzmann method; Mesoscopic simulation;

Synthesis of Fe3O4 nanoparticles with various sizes and magnetic properties by controlled hydrolysis by Hironori Iida; Kosuke Takayanagi; Takuya Nakanishi; Tetsuya Osaka (274-280).
Nanoparticles of Fe3O4 were synthesized by hydrolysis in an aqueous solution containing ferrous and ferric salts at various ratios with 1,6-hexanediamine as a base. It was found that the ferrous to ferric ratio influences the reaction mechanism for the formation of Fe3O4. When the ratio of ferrous to ferric ions was increased, the formation of large hydroxide particles as a precursor of Fe3O4 was promoted, which resulted in an increase in the size of Fe3O4 nanoparticles. As a result, the mean diameter of Fe3O4 nanoparticles increased from ∼9 to ∼37 nm as the molar percentage of ferrous ions with respect to the total iron ions was increased from 33 to 100%. Furthermore, it was demonstrated that magnetic properties of Fe3O4 nanoparticles can be controlled by adjusting the molar ratio of ferrous to ferric ions as well as the particle diameter.Fe3O4 nanoparticles with various sizes and magnetic properties were synthesized by controlling the ratio of ferrous and ferric ions in the hydrolysis reaction.
Keywords: Fe3O4 nanoparticle; Hydrolysis; Ferrous and ferric ions; Particle diameter; Magnetic property;

Fullerol cluster formation in aqueous solutions: Implications for environmental release by Jonathan A. Brant; Jérôme Labille; Christine Ogilvie Robichaud; Mark Wiesner (281-288).
Here we report on the characteristics of fullerol in aqueous systems and examine those conditions that affect the physical state of fullerol in water. When dispersed in water fullerol forms polydisperse suspensions characterized by both small ( ∼ 100  nm ) and large associations ( > 500  nm ). These clusters are charged with a point of zero net proton charge (PZNPC) of approximately pH 3. Though the size of fullerol clusters may be manipulated through changes in solution chemistry, principally pH, cluster formation cannot be entirely prevented through these means alone. The fullerol cluster structure is amorphous as revealed by X-ray diffraction analysis, which is in contrast to clusters of C60 formed through dissolution in toluene and then introduced into water through sonication (SONnC60). The SONnC60 clusters are crystalline with a structure similar to that of unreacted C60 crystals.
Keywords: Fullerol; C60; Nanoparticle; Fullerenes; Cluster formation;

Self-assembly and supramolecular transition of poly(amidoamine) dendrons focally modified with aromatic chromophores by Bing-Bing Wang; Wu-Song Li; Xin-Ru Jia; Min Gao; Yan Ji; Xin Zhang; Zi-Chen Li; Lei Jiang; Yen Wei (289-296).
Three novel series of amphiphiles based on poly(amidoamine) dendrons (from G1 to G3) and having different aromatic chromophores (Cz I, Cz II, and Py) at the focal point were synthesized and studied for their self-assembly behavior in aqueous solution by using electronic microscopies (i.e., SEM and TEM), UV–vis, fluorescence, IR, and 1H NMR spectroscopy. It was found that the generation of dendrons affected significantly the self-assembly of these amphiphiles in aqueous solution and the morphological structures of the resulting assemblies depended greatly on the architecture of the focal chromophores. As a result, the first generation of dendrons assembled readily into vesicles at low concentrations. These vesicular structures subsequently fused to form a stable tubular structure. Similar tubular structures could also be directly obtained through self-assembly of these amphiphilic dendrons at high concentrations. X-ray investigations showed that the resulting tubules possessed a lamellar structure. A head-to-head packing model of amphiphilic dendrons in the assemblies was proposed.G1–G3 poly(aminoamine) dendrons with focal aromatic chromophores showed versatile self-assembly behavior and supramolecular transition depending on the structure of chromophores and the concentration of dendrons in the aqueous solution.
Keywords: Dendrimers; Dendrons; Self-assembly; Morphological transition; Supramolecular chemistry;

Synthesis of one-dimensional silver oxide nanoparticle arrays and silver nanorods templated by Langmuir monolayers by Hong-Guo Liu; Fei Xiao; Chang-Wei Wang; Qingbin Xue; Xiao Chen; Yong-Ill Lee; Jingcheng Hao; Jianzhuang Jiang (297-303).
One-dimensional (1D) silver oxide nanoparticle arrays were synthesized by illuminating the composite Langmuir–Blodgett monolayers of porphyrin derivatives/Ag+ and n-hexadecyl dihydrogen phosphate (n-HDP)/Ag+ deposited on carbon-coated copper grids with daylight and then exposing them to air. Transmission electron microscopy (TEM) observation shows that the nanoparticle size is around 3 nm, with the separation of about 2–3 nm. High-resolution TEM (HRTEM) investigation indicates that the particles are made up of Ag2O. Ag nanorods with the width of 15–35 nm and the length of several hundreds of nanometers were synthesized by irradiating the composite Langmuir monolayers of porphyrin derivatives/Ag+ and n-HDP/Ag+ by UV-light directly at the air/water interface at room temperature. HRTEM image and selected-area electron diffraction (SAED) pattern indicate that the nanorods are single crystals with the (110) face of the face-centered cubic (fcc) silver parallel to the air/water interface. The formation of the 1D arrays and the nanorods should be attributed to the templating effect of the linear supramolecules formed by porphyrin derivative or n-HDP molecules in Langmuir monolayers through non-covalent interactions.One-dimensional ordered arrays of silver oxide nanoparticles formed in composite porphyrin derivative/Ag+ Langmuir–Blodgett monolayers.
Keywords: Ag nanorod; 1D array; Ag2O nanoparticle; Langmuir monolayer; Air–water interface;

Growth of Au/Ag nanowires in thin surfactant solution films: An electron microscopy study by Olga Krichevski; Yael Levi-Kalisman; Daniel Szwarcman; Yossi Lereah; Gil Markovich (304-309).
The surfactant templated gold–silver nanowire growth process in a thin solution film was probed by cryo-transmission electron microscopy (cryo-TEM). The increasing surfactant concentration upon film drying appears to induce phase transformations in the film and form a liquid crystalline template for the nanowires growth. High-resolution transmission electron microscopy (HRTEM) and electron holography revealed that the nanowires were polycrystalline with some preferred crystallite orientations and had a roughly cylindrical cross-section. Further improvement of the technique may lead to highly ordered metal nanowire arrays within the surfactant matrix similar to the closely related mesoporous materials.Cryo-transmission electron microscopy and other microscopy techniques were used to study the formation of gold–silver nanowires in a surfactant template during the drying of thin surfactant solution films.
Keywords: Nanowires; Gold nanorods; Liquid crystal phases; Cryo-TEM; Mesoporous materials; Surfactant mesophases;

Titania nanoparticles synthesis in mesoporous molecular sieve MCM-41 by N.B. Lihitkar; Majid Kazemian Abyaneh; V. Samuel; R. Pasricha; S.W. Gosavi; S.K. Kulkarni (310-316).
Nanocrystalline titanium oxide (TiO2) is one of the most useful oxide material, because of its widespread applications in photocatalysis, solar energy conversion, sensors and optoelectronics. The control of particle size and monodispersity of TiO2 nanoparticles is a challenging task. The use of MCM-41, an inorganic template of uniform pore size (2–10 nm), can overcome this difficulty and produce stable nanoparticles of uniform size and shape. Here, we demonstrate the synthesis of titania nanoparticles inside the pores of silica based MCM-41 forming a TiO2/Si-MCM composite. Composites are formed in the alcoholic medium by incipient wetness impregnation method. Titania particles of average 3 nm size are obtained. Effect of silica and titania precursors on the quality of nanoparticles has been investigated. The characterization of titania–MCM-41 composites has been carried out using a variety of techniques like UV–vis absorption spectroscopy, X-ray diffraction, FT-IR spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and photoluminescence spectroscopy. It has been found that the titania particles are co-ordinated with Si-MCM by Si―O―Ti covalent bond.The nanoparticles of titania (TiO2) are synthesized in the mesoporous silica template MCM-41 by Incipient Wetness Impregnation method. The particles are of approximately 3 nm size which are linked with silica wall by Si―O―Ti bond.
Keywords: Mesoporous material; Template; Incipient wetness impregnation; Titania;

Adsorption of Me–HEDP complexes onto γ-Al2O3 by Lidia Hein; María C. Zenobi; Elsa Rueda (317-323).
This work studies the adsorption of Me–1-hydroxiethane-(1,1-diphosphonic acid) (HEDP) complex onto alumina in the pH range from 5.0 to 9.5. The extent of HEDP adsorption is not significatively affected by the presence of Me(II), while, HEDP has an interesting effect on Me(II) adsorption. At high surface covering, Cu(II) adsorption is enhanced at low pH reaching a maximum of 57% at pH nearly 6, however, at pH > 6 a decrease about 20% in the amount of Cu(II) adsorbed takes place by the presence of HEDP. The model predicts a ternary surface complex (AlLCu) to justify the increase of Cu(II) adsorbed at lower pH. At the lower pH and at high Zn(II) concentration the presence of equimolar concentration of HEDP also causes a discernible increase in the amount of Zn(II) adsorbed. At pH 5, the percentage of Zn(II) complexed with HEDP increased from negligible to 40% as the HEDP concentration increased. However, in this case the HEDP does not have a suppressor effect on the Zn(II) adsorption at the higher pH. Again, the presence of anionic-type complexation is here postulated to reach a good fit with the experimental results. The effect of HEDP over Zn(II) adsorption becomes less pronounced with the excess of surface sites. Cd(II)–HEDP solution complexes are weaker than those corresponding to Cu(II) and Zn(II), so competitive effects between surface and solution are much less significant in comparison to Cu(II)–HEDP and Zn(II)–HEDP alumina systems. So, the effect of HEDP on the Cd adsorption at low concentration and low pH is more stressed than in the case of Cu(II) and Zn(II). Overall, results indicate that the presence of HEDP in the aquatic systems could have a significant impact on the mobility and distribution of Cu(II), Zn(II) and Cd(II) in the environment.Adsorption of Cu(II) and Zn(II) onto alumina as a function of pH in the presence of HEDP. Aged alumina 1 g/L, I = 0.1  M NaNO3. Total concentration Cu(II)–HEDP 5 × 10 −4  M (a) and Zn(II)–HEDP 5 × 10 −4  M (b).
Keywords: Alumina; Me(II)–phosphonate adsorption; Surface complexes;

A note on spin-coating with small evaporation by V. Cregan; S.B.G. O'Brien (324-328).
We examine a simple model of spin-coating with “small” evaporation effects and using a formal asymptotic approach we improve on previous approximate models.We examine a simple model of spin-coating with “small” evaporation effects and using a formal asymptotic approach we improve on previous approximate models.
Keywords: Spin-coating; Evaporation;

Moving blue band caused by cooperation of diffusion and phase separation by Chiori Sato; Naoki Esumi; Takahiko Ban; Akihisa Shioi (329-333).
Diffusions of Cu2+ and Fe3+ in gelatin generate a moving blue band. It is formed by a diffusion of Cu2+ and a phase separation of gelatin with diffusing Fe3+. The diffusing Fe3+ forms Fe(OH)3 colloids and gathers gelatin molecules from the surroundings. The diffusion of gelatin molecules generates the concentration gradient, resulting in a gel/sol transition in the dilute phase. In the region where the concentration of Fe3+ is high enough, the gel remains hard, while a sol phase appears under the hard gel. The absorption spectrum of Cu2+ depends on the concentration ratio of Cu2+ to gelatin. As a consequence, we can see a blue band in the restricted region between the diffusing front of Cu2+ and the phase separation front. The movement of the blue band is caused by a coupling of a simple diffusion and the phase separation.Diffusions of Cu2+ and Fe3+ in gelatin generate a moving blue band. A sol/gel transition caused by Fe3+ plays a key role in the traveling band.
Keywords: Traveling band; Diffusion; Phase separation; Sol–gel transition; Gelatin;

In a work published in this journal by J.P.S. Cabral and A.R.W. Smith [J. Colloid Interface Sci. 149 (1992) 27], it is reported that the 1-dodecylguanidinium acetate (dodine) exhibits first CMC at 20–30 μM and second CMC at 110–120 μM in aqueous solution at 22.5 °C. Such low CMCs are unusual for ionic surfactants with dodecyl chain, and is quite interesting if this is the case. Thus, we investigated the micelle formation of dodine by electrical conductivity measurements. The specific conductivity, κ, vs concentration plot showed no evidence for micelle formation up to a few hundreds μM at 25 °C. The Krafft temperature of dodine was found to be approx. 52 °C. When conductivity measurements were made at 54 °C, a clear break point was observed in the κ vs concentration plot at 9.5 mM, which must correspond to the CMC of dodine. This CMC value is quite normal for cationic surfactant with dodecyl chain.Anomalously low CMC of 1-dodecylguanidinium acetate (dodine) previously reported by Cabral and Smith [J. Colloid Interface Sci. 149 (1992) 27] was corrected.
Keywords: 1-Dodecylguanidinium acetate (dodine); Critical micelle concentration (CMC); Electrical conductivity;

A facile solution-phase synthesis of high quality water-soluble anatase TiO2 nanocrystals by Ping Wang; Dejun Wang; Haiyan Li; Tengfeng Xie; Hongzhe Wang; Zuliang Du (337-340).
Water-soluble anatase TiO2 nanocrystals (NCs) were synthesized by a simple sol–gel method. The reaction time is greatly reduced even under mild conditions. High-resolution transition electron microscopy (HRTEM), X-ray diffraction (XRD) and UV–vis were used to characterize the synthesized NCs and proved that the NCs are anatase phase and about 2 nm with near spherical shape. Surface photovoltage spectroscopy (SPS) experiments show that the synthesized anatase NCs have good photovoltaic properties compared with that of poly(vinyl pyrrolidone) (PVP) coated NCs synthesized by the similar method.A simple novel method was developed to synthesize water-soluble anatase TiO2 nanocrystals. Surface photovoltage spectroscopy experiments show that the synthesized nanocrystals have good photovoltaic properties compared with that of strongly bonded surfactant coated NCs synthesized under the similar conditions.
Keywords: Anatase; TiO2 nanocrystals; Photovoltaic;

Raspberry-like silica nanospheres were prepared by electrostatic self-assembly of polyelectrolytes and monodisperse silica nanoparticles of two different sizes, and their coatings were fabricated via layer-by-layer assembly with polyelectrolytes and following calcination. The morphology of the raspberry-like silica nanospheres and their coatings were observed by scanning and transmission electron microscopies. The surface properties of these coatings were investigated by measuring their water contact angles, and the results showed that such hierarchically structured coatings had unique superhydrophilic and antifogging properties. Finally, the formation mechanism and the property–structure relationship were discussed in details.Raspberry-like silica nanospheres and their coatings were prepared via a facile layer-by-layer dip-coating approach, and the obtained hierarchically structured coatings demonstrated unique superhydrophilic and antifogging properties.
Keywords: Superhydrophilic; Antifogging; Raspberry-like silica nanospheres; Polyelectrolytes; Self-assembly;

by Arthur Hubbard (346).