Journal of Colloid And Interface Science (v.335, #1)

This paper presents a concise review of the solution-phase synthesis of hollow micro- and nanostructures by using suitable templates such as hard templates, soft templates and reactive templates. Non-spherical hollow structures such as single-walled (a) and double-walled (b) Ag rhombododecahedral cages can be fabricated through the microscale Kirkendall Effect via reactive templates.The solution-phase synthesis of hollow micro- and nanostructures by using suitable templates such as hard templates, soft templates and reactive templates has attracted considerable attention in recent years. This paper is focused on the template synthesis of inorganic hollow structures with tailored size, morphology, and architecture, with emphasis on the templating strategies recently developed in our lab for the facile solution-phase synthesis of novel inorganic hollow structures. The formation mechanisms of the hollow structures via different kinds of templates are discussed in depth to show the general concepts for the preparation processes. The properties and applications of hollow structures are briefly described, demonstrating the promising and broad application fields of hollow materials.
Keywords: Hollow structures; Templates; Solution-phase synthesis; Nanomaterials; Formation mechanism;

Spectroscopic study of Zn2+ and Co2+ binding to extracellular polymeric substances (EPS) from aerobic granules by Xue-Fei Sun; Shu-Guang Wang; Xiao-Min Zhang; J. Paul Chen; Xiao-Ming Li; Bao-Yu Gao; Yue Ma (11-17).
XPS patterns of Co2p after the two metal ions interacting with EPS: Co(II)-loaded (a) LB-EPS and (b) TB-EPS, and Co(II)/Zn(II)-loaded (c) LB-EPS and (d) TB-EPS.The interacting mechanisms of metallic cations (Zn2+ and Co2+) to active chemical groups on the extracellular polymeric substances (EPS) of the aerobic granules, including loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS), were examined by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. For Zn2+ and Co2+, LB-EPS showed stronger binding properties than TB-EPS and the process of them was described well by the Langmuir isotherm. Compared to the single-metal system, binary-metal addition induced competitive binding between the Zn2+ and Co2+ with reduction of the maximal binding capacity for both EPS. The main chemical groups involved in the interactions between contaminants were apparently alcohol, carboxyl and amino. These groups were part of the EPS structural polymers, namely, polysaccharides, proteins, and hydrocarbon-like products. When biosorption and flocculation occurred at the same time, the LB-EPS were used not only as chelate sorbents but also as flocculants to further enhance their sorption capacity.
Keywords: Extracellular polymeric substances (EPS); Aerobic granules; Bind; XPS analysis; Metal ions;

Effect of aluminum on the deposition of silica scales in cooling water systems by Ikuko Nishida; Yuuki Shimada; Tomoyuki Saito; Yoshihiro Okaue; Takushi Yokoyama (18-23).
Adsorption of aluminum hydroxide particles smaller than 0.2 μm on the surface of the solid accelerates the formation of silica scalesThe mechanism of formation of silica scales from cooling water was studied by chemical analyses of the cooling water and silica scales, characterization of the aluminum in the silica scales by 27Al magic angle spinning NMR, the relationship between size distribution of particles in the cooling water and their Al/Si atomic ratios and zeta potentials, and the adsorption properties of the particles on the surface of silica gel powder as a mimic of silica scale. From our results, we determined that aluminum is concentrated from the cooling water into silica scales during their formation, 6-coordinate aluminum is preferentially adsorbed on the surface of the solid, and various particles with differing sizes, surface charges, and Al/Si atomic ratios are formed in the cooling water after addition of polyaluminum chloride. The formation mechanism for silica scales in the cooling water system is proposed based on the electrostatic interaction. The formation of aluminum hydroxide particles smaller than 0.2 μm with positive charges, consisting of 6-coordinate aluminum, and their subsequent adsorption on the surface of the solid are the most important factors contributing to the formation of silica scales.
Keywords: Silica scales; Aluminum; Zeta potential; NMR; Cooling water systems;

Adsorption of carmoisine A from wastewater using waste materials—Bottom ash and deoiled soya by Vinod K. Gupta; Alok Mittal; Arti Malviya; Jyoti Mittal (24-33).
Effect of amount of adsorbent on uptake of carmoisine A over bottom ash and deoiled soya at different temperatures.The present study deals with the application of bottom ash, a power plant waste, and deoiled soya, an agricultural waste, for the adsorptive removal of carmoisine A dye from its aqueous solutions. This paper incorporates a comparative study of the adsorption characteristics of the dye on these effective adsorbents along with effects of time, temperature, concentration, and pH. Analytical techniques have been employed to find pore properties and characteristics of adsorbent materials. Batch adsorption studies, kinetic studies, and column operations have also been performed to understand the dye extraction ability of the adsorbents. The adsorption behavior of the dye has been studied using Freundlich, Langmuir, Tempkin, and Dubinin–Radushkevich adsorption isotherm models. The monolayer adsorption capacity determined from the Langmuir adsorption equation has been found as 1.78 × 10−5 and 5.62 × 10−5  mol g−1 at 323 K for bottom ash and deoiled soya, respectively. Kinetic measurements suggest the involvement of pseudo-second-order kinetics in both adsorptions and each case is controlled by a particle diffusion process. Column experiments demonstrated that both adsorbents could be practically utilized in elimination of hazardous dye from effluent and dye material can be recovered by eluting NaOH through the exhausted columns.
Keywords: Carmoisine A; Bottom ash; Deoiled soya; Isotherms; Kinetics;

Conducting and superparamagnetic monodispersed Fe3O4–poly(3, 4-ethylenedioxythiophene) core–shell composite nanoparticles with the size about 15 nm, were synthesized via an in situ chemical oxidative polymerization in the micellar solution of lignosulfonic acid (LSA).Core–shell nanocomposites composed of iron oxide (Fe3O4) nanoparticles and conjugated polymer, poly(3, 4-ethylenedioxythiophene) (PEDOT), were successfully synthesized from a simple and inexpensive in situ chemical oxidative polymerization of EDOT with Fe3O4 nanoparticles in the micellar solution of lignosulfonic acid (LSA) which serves as both a surfactant and a dopant. These nanocomposites (Fe3O4–PEDOT) were subsequently characterized for morphological, crystalline, structural, electrical and magnetic properties by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), four-probe meter and superconductor quantum interference device (SQUID), respectively. Results show that the nanocomposites have a spherical core–shell shape, are ∼10 nm in size and are superparamagnetic with good magnetic saturation and good electrical conductivities. Existence of Fe3O4 in the nanocomposites was confirmed by using Energy dispersive X-ray photoelectron spectroscopy (EDAX) and X-ray photoelectron microscopy (XPS). We also investigated a possible formation mechanism of the core–shell nanocomposites, and the effect of Fe3O4 nanoparticles on the electro-magnetic properties of the nanocomposites. Such novel conducting and superparamagnetic composite nanomaterials can be applied to sensors, magnetic data storage, electro-magnetic resonance wave absorption, etc.
Keywords: Nanocomposites; Poly(3, 4-Pethylenedioxythiophene); Electrical conductivity; Magnetic property;

Co x Pt1−x alloy nanoparticles is prepared with different compositions of Co and Pt using TX-100 micelles as reactor and investigation predict particles provide ordered structure with high coercivity in equiatomic composition.Among many ferromagnetic materials, CoPt alloy nanoparticles with high coercivity and small grain size are one of the potential candidates having its application in high-density storage media manufacturing. CoPt alloy nanoparticles of different compositions have been prepared in TX-100 micellar medium and capped with sodium oleate to prevent the agglomeration during annealing at high temperature. Their structural and magnetic properties were investigated before and after heat treatment. The particles with ∼50:50 compositions of Co and Pt gives L10 phase after annealing at 900 °C for 1 h and show a high coercivity (∼4.4 kOe at room temperature) and remanence due to its highly anisotropic L10 structure.
Keywords: Magnetic nanoparticles; CoPt; Micelles; FCC and L10 phase;

k-Value-based ferron assay and its application by Changqing Ye; Dongsheng Wang; Xiaohong Wu; Jiuhui Qu (44-49).
In matured PACl solutions with various b values, three types of distinct rate constants by nonlinear regression fitting can be observed descending by order of magnitude. That different kinetics can be ascribed to three types of species.Al13 is notable for its promising application in many fields. It has been believed that Al13 could be assayed in term of Al b derived from traditional ferron assay. But the inherent relation between Al13 and Al b is not clear. Here, the new k-value-based ferron assay using nonlinear least squares analysis is suggested to resolve the ambiguity. The experimental results reveal that the moderate kinetics (k value) around 0.001 s−1 can be ascribed to Al13. In the short-term aging of freshly neutralized aluminum solutions with OH/Al molar ratio of 2.2, the rapid progress of Al13-like transformation into Al13 can be traced by this method, whereas it may be masked by traditional ferron assay because the metastable intermediates also contribute absorbance to Al b fraction. Al b can only be regarded as Al13 when Al13 forms completely and becomes the stable specie in the matured solution.
Keywords: k Value; Ferron assay; Al13; Al b ; Speciation; Short-term aging;

Uniform nanosize platelets of nickel were prepared by induced reduction with gelatin of preformed nickel hydroxide particles of the same morphology.Uniform stable nanosize nickel platelets were prepared by first coating Ni(OH)2 particles of the same shape with gelatin and then heating them at moderate temperatures in nitrogen without addition of any reducing agents. The resulting platelets consist of a mixture of Ni and NiO. Depending on the amount of gelatin coating and temperature, up to 73% of solids were converted to the metal. Subsequent heating of such powders at 190 °C in a stream of 5% H2 in N2 produced only Ni platelets with a modal length of ∼60 nm and several nm thick.
Keywords: Coated particles; Gelatin coatings; Nanosize nickel; Metal platelets; Nickel platelets; Platelets nanosize;

The size distribution of montmorillonite colloidal particles reaches pseudo-equilibrium over time. Similar pseudo-equilibrium profiles are reached by generation and sedimentation experiments.Colloid generation and sedimentation experiments were carried out on Na- and Ca-montmorillonite in order to verify whether pseudo-equilibrium concentrations are reached at the same level in both types of experiments. The size and concentration of colloidal Na- and Ca-montmorillonite particles were monitored as a function of time and distance from the colloid bed in different ionic strength solutions. A stable pseudo-equilibrium concentration was reached after time in generation and sedimentation experiments. The colloid concentration decreased sharply at distances near to the colloid source. Na-montmorillonite concentration at pseudo-equilibrium (roughly quantified at distances ⩾7 cm from the colloid source) was 5.2 ± 0.5, 0.5 ± 0.1, and 0.2 ± 0.1 mg L−1 in 0.001, 0.01, and 0.1 M NaCl solution, respectively, while the Ca-montmorillonite concentration was 0.4 ± 0.2 mg L−1 in 0.001 M NaCl.
Keywords: Generation; Sedimentation; Na-montmorillonite; Ca-montmorillonite; Colloids; Size distribution;

Preparation and stabilization of monodisperse colloidal gold by reduction with aminodextran by Benjamin J. Morrow; Egon Matijević; Dan V. Goia (62-69).
Stable concentrated dispersions of monodisperse gold nanoparticles were synthesized by using diethylaminoethyl-dextran as reductant and stabilizer.Stable concentrated aqueous dispersions of monodisperse gold nanoparticles were prepared using diethylaminoethyl-dextran as reductant and stabilizer. The effectiveness of dextran as reducing agent was strongly affected by the pH. In alkaline solutions, the Au(III) species were rapidly and completely reduced, yielding stable dispersions of spherical uniform gold nanoparticles. Their modal diameter could be adjusted from 18 to 40 nm by varying the pH, temperature, and the Au3+/dextran ratio. In contrast, under acidic conditions (pH ∼ 4.0) the reduction was very slow, favoring the formation of large gold crystals of other shapes. A general mechanism explaining the reducing and stabilizing actions of polysaccharides in general, and of diethylaminoethyl-dextran in particular, is proposed.
Keywords: Gold sol; Aminodextran; Monodisperse gold;

Mesostructures obtained in the systems with nonionic surfactant and water-soluble silica precursor at neutral condition.We report on the fabrication of hybrid organic–inorganic mesostructured materials from aqueous solutions of a series of poly(oxyethylene) cholesteryl ethers (ChEO n , where n is the number of oxyethylene units) with a water-soluble silica precursor, tetra(2-hydroxyethyl) orthosilicate (THEOS) at a neutral pH condition. ChEO10 and ChEO15 form rectangular and 2D-hexagonal mesostructures, respectively, as detected by Small-Angle X-ray Scattering (SAXS) measurements. On the other hand, disordered structures (showing nevertheless a correlation length) are observed with longer hydrophilic chain surfactants, such as ChEO20, ChEO24 and ChEO30. Highly ordered mesostructures cannot be obtained at neutral pH when THEOS is substituted with a conventional silica precursor, tetraethyl orthosilicate (TEOS). The structural evolution from initial disordered micellar solutions is dependent on both surfactant and THEOS concentrations. It is also found that the silica mesostructures obtained from ChEO10 and ChEO15 templates are the same as those of the liquid crystalline phases formed in aqueous mixtures of the corresponding surfactant.
Keywords: Hybrid organic–inorganic mesostructured material; Mesoporous silica; Nonionic surfactant; Small-Angle X-ray Scattering; Transmission electron microscopy; Rectangular mesostructure; 2D-hexagonal mesostructure; Water-soluble silica precursor; Surfactant phase behavior;

Intercalation of both CTMAB and Al13 into montmorillonite by Runliang Zhu; Tong Wang; Fei Ge; Wangxiang Chen; Zhimin You (77-83).
The speculative and schematic drawing of the structural models of IOCs. It shows that the interlayer spaces of IOCs comprise Al13-dominated zone and CTMAB-dominated zone.Clays intercalated with both organic cations and hydroxy-metal cations, also known as inorganic–organic clays (IOCs), have drawn great interests in the recent years because they possess the properties of both organoclays and pillared layered clays (PILCs). In this work, cetyltrimethyl ammonium bromide (CTMAB) and hydroxy-aluminum ([Al13O4(OH)24(H2O)12]7+ or Al13) were selected as the representatives of organic cations and hydroxy-metal cations, and three different methods were employed for the intercalation of montmorillonite at various CTMAB/Al13 ratios. This work aims to provide some novel information for clarifying the structural characteristics of IOCs. The experimental results showed that the structures of the resulting IOCs strongly depended on the intercalation methods and CTMAB/Al13 ratio. Both the intercalation agents could be intercalated into montmorillonite if they were used simultaneously for the intercalation, or if Al13 was intercalated after CTMAB, and the resulting IOCs were shown to have large basal spacing and small surface areas. However, if Al13 was intercalated first, the loading amounts of CTMAB would decrease significantly when the used Al13 amounts were relatively large (⩾4 mmol Al/g montmorillonite). This could be attributed to the “lock” effect of montmorillonite’s layers by the pre-intercalated Al13, and the basal spacing values of the resulting IOCs were shown to be equal to those of the PILCs.
Keywords: Inorganic–organic clays; Montmorillonite; Hydroxy-aluminum; Cationic surfactant; Intercalation;

Lattice Boltzmann method for dynamic wetting problems by Elham Attar; Carolin Körner (84-93).
In present work the supplementary force, which is treated as a capillary force, is defined to simulate the equilibrium and dynamic wetting behavior of liquids.Wetting is an important phenomenon in many engineering applications. In this study, a new algorithm is presented to simulate 2D dynamic wetting phenomena using the single phase lattice Boltzmann method (LBM). Basis of our method is an additional force at triple points where fluid, gas and wall intersect. This supplementary force, which is treated as a capillary force, is able to simulate the equilibrium and dynamic wetting behavior of liquids. Based on this method, droplet spreading or recoiling on a solid surface and the capillary rise with various wetting properties can be simulated successfully. The results of the simulation are compared with analytical solutions and experiments. Good agreement is achieved for dynamic as well as equilibrium situations.
Keywords: Simulation; Lattice Boltzmann method; Wetting;

Effects of temperature on water-in-oil emulsions stabilised solely by wax microparticles.The possibility of stabilising oil–water mixtures using wax particles alone is reported. As judged from contact angle measurements, wax particles are hydrophobic and act as effective emulsifiers of water-in-squalane emulsions. Specific differences exist depending on the chemical composition of the particles. The effect of temperature on emulsion stability has been explored in detail. If particles are pre-adsorbed to water drop interfaces by emulsification at room temperature, subsequent increase of temperature leads to a progressive increase in sedimentation and coalescence as particles melt and desorb from interfaces. The temperature range over which this occurs is similar to that of the melting range of the particles alone. If however the particles are melted prior to emulsification, surface-active long chain ester or acid molecules adsorb to freshly created interfaces giving rise to excellent stability to coalescence at high temperatures. Rapid cooling of these latter emulsions enhances their long-term stability as solidification of the molten wax leads to a thickening of the continuous oil phase.
Keywords: Wax; Emulsions; Melting; Hydrophobic;

Spontaneous vesicle formation with an ionic liquid amphiphile by Kulbir Singh; D. Gerrard Marangoni; Jason G. Quinn; Robert D. Singer (105-111).
TEM image of fused vesicles prepared from an ionic liquid amphiphile (hexylpyridinium tetrafluoroborate) and an anionic surfactant (sodium dodecylsulfate).A simple and effective method for the formation of stable multilamellar vesicles is reported as a potential application of ionic liquid materials (IL’s) and as replacements for conventional surfactants used in such applications. The methodology is based on the various approaches for the formation of vesicles from oppositely charged surfactants. Photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM) have been used to estimate the size of the aggregates; the TEM studies have also revealed morphological differences in the self-assembled systems with changing ionic liquid material. Size measurements from PCS indicate consistent growth of the ionic-liquid containing vesicles with increasing concentration of added anionic surfactant. 2D NOESY NMR spectroscopy have been used to examine the manner in which IL amphiphile self-assembles with the second surfactant in solution. A comparison has been made between the aggregates formed from hexylpyridinium tetrafluoroborate ( [ HexPy ] [ BF 4 - ] ) /sodium dodecylsulfate (SDS) and hexylpyridinium bromide ([HexPy][Br])/sodium dodecylsulfate (SDS).
Keywords: Catanionic systems; Ionic liquids; Vesicles; PCS; NOESY;

Lattice Boltzmann simulations of droplet formation during microchannel emulsification by Eduard van der Zwan; Ruud van der Sman; Karin Schroën; Remko Boom (112-122).
Droplet formation during microchannel emulsification as described by lattice Boltzmann simulation, leads to new insights in process parameters and local flow conditions.In this study, we compared microchannel droplet formation in a microfluidics device with a two phase lattice Boltzmann simulation. The droplet formation was found to be qualitatively described, with a slightly smaller droplet in the simulation. This was due to the finite thickness of the interface in the simulations. Dependence on dispersed flow rate could be very nicely predicted by the model, while a better insight was obtained on the internal pressures and flow velocities during droplet formation. These were found to be well described by simple relations; (1) the pressure inside the dispersed phase was predicted very well by the Laplace pressure while (2) the flow rate through the neck could be estimated by the flow through an orifice. These insights simplify the development of design rules for new microchannel devices.
Keywords: Lattice Boltzmann; Simulation; Emulsification; Emulsion; Microtechnology;

Thermal control of electroosmotic flow in a microchannel through temperature-dependent properties by Ho Sang Kwak; Hyoungsoo Kim; Jae Min Hyun; Tae-Ho Song (123-129).
Various flow patterns responding to spatial temperature variations represented by color.A numerical investigation is conducted on the electroosmotic flow and associated heat transfer in a two-dimensional microchannel. The objective of this study is to explore a new conceptual idea that is control of an electroosmotic flow by using a thermal field effect through the temperature-dependent physical properties. Two exemplary problems are examined: a flow in a microchannel with a constant vertical temperature difference between two horizontal walls and a flow in a microchannel with the wall temperatures varying horizontally in a sinusoidal manner. The results of numerical computations showed that a proper control of thermal field may be a viable means to manipulate various non-plug-like flow patterns. A constant vertical temperature difference across the channel produces a shear flow. The horizontally-varying thermal condition results in spatial variation of physical properties to generate fluctuating flow patterns. The temperature variation at the wall with alternating vertical temperature gradient induces a wavy flow.
Keywords: Electroosmotic flow; Microchannel; Thermal field effects; Temperature-dependent physical properties; Thermally-driven electroosmotic Couette flow;

Electrophoresis of a soft particle normal to a plane by Wen-Li Cheng; Yan-Ying He; Eric Lee (130-139).
The electrophoresis of a soft particle normal to a planar boundary is solved by a pseudo-spectral method with the combination of spherical and bipolar coordinates.Electrophoresis of a spherical composite particle normal to a plane is investigated theoretically. The composite particle under consideration, or the “soft” particle, consists of an inner hard core coated with a concentric porous layer containing uniformly distributed fixed charges. A pseudo-spectral method based on a Chebyshev polynomial is adopted to solve the resulting electrokinetic equations. The effects of general parameters of electrokinetic interest are examined, such as the double layer thickness, the density of the fixed charges carried in the porous layer, the retarding friction coefficient of the porous layer, and so forth. In particular, the effect of the presence of the planar boundary is examined in detail, including the clearly visible deformation of the double layer due to the presence of the boundary and its electrokinetic implications. Local maximum of charge distribution within the porous layer near the north pole is observed when the double layer is thick. Moreover, the impact of the electroosmotic flow within the porous layer is explored. The appearance of a vortex flow due to electroosmosis within the porous layer is shown, which explains directly the retarding effect of mobility when the double layer becomes thinner, as the orientation of this vortex is opposite to the particle motion. Comparisons with various limiting cases available in the literature show excellent agreement, indicating the accuracy and reliability of the results presented in this study.
Keywords: Electrophoresis; Soft particle; Planar boundary; Brinkman model; Electric double layer;

Biosensing by optical waveguide spectroscopy based on localized surface plasmon resonance of gold nanoparticles used as a probe or as a label by Mayuki Kajiura; Takuya Nakanishi; Hironori Iida; Harumi Takada; Tetsuya Osaka (140-145).
Localized surface plasmon resonance of gold nanoparticles was used for the detection of streptavidin in two different modes using gold nanoparticles (a) as a probe and (b) as a label.The application of localized surface plasmon resonance (LSPR) of gold nanoparticles for the detection of biotin–streptavidin binding, as a typical biological reaction, was investigated by using optical waveguide spectroscopy, and two different modes for the use of gold nanoparticles, one as a probe and the other as a label were compared with each other. The combination with optical waveguide spectroscopy was found to bring about a high sensitivity for the biomolecular detection system using LSPR of gold nanoparticles in both modes. In particular, the mode using gold nanoparticles as a label was demonstrated to be of advantage to devising proper procedures for using nanoparticles and evaluating actual response relevant to the phenomenon concerned, and thus to sensitive detection.
Keywords: Gold nanoparticle; Optical waveguide spectroscopy; Localized surface plasmon resonance; Biotin–streptavidin reaction;

One-pot method for build-up nanoporous super oil-repellent films by Thierry Darmanin; Frédéric Guittard (146-149).
Superoleophobic properties can be obtained in a one-pot method, i.e. without post-treatment, from a well-designed bottom-up approach by electrodeposition of highly fluorinated poly(3,4-ethylenedioxypyrrole) as conductive polymers.The aim of this work was to demonstrate the possibility of obtaining super-surfaces, i.e. superoleophobic and as a consequence superhydrophobic properties, from electrodeposited conductive polymer. From original structure containing a fluorinated chain grafted to 3,4-ethylenedioxypyrrole (EDOP) core, we report the characterization of the electrochemical properties of polymer films as well as the morphology (SEM) and wettability against probe liquids (water, diiodomethane, hexadecane). The exceptional oil-repellent properties, quickly obtained and in one step, are in correlation with the nanoporous structures of the films which is of great interest in the development of lyophobic materials based on the fluorophobic effect.
Keywords: Superoleophobic; Superhydrophobic; Repellent; Electrochemical polymerization; Fluorinated; EDOP; Porosity; Wettability;

by Arthur Hubbard (150).