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Journal of Colloid And Interface Science (v.354, #2)

Cover 1 (pp. ofc).

Rare earth β-NaGdF4 fluorides with multiform morphologies: Hydrothermal synthesis and luminescent properties by Yuan Wu; Chunxia Li; Dongmei Yang; Jun Lin (pp. 429-436).
Rare earth fluorides β-NaGdF4 nano/microstructures with multiform shapes and sizes as well as fruitful emission properties were synthesized by a simple hydrothermal process.Display Omitted► A facile and effective hydrothermal method was developed to prepare gadolinium fluorides (β-NaGdF4 and GdF3) with multiform morphologies and sizes by tuning the pH value and F sources. ► Simplicity, low-costs, ease of scale-up, the diverse morphologies and relative greenness (aqueous solution) constitute the key traits of this method. ► Multicolor down-conversion and up-conversion emissions can be obtained in β-NaGdF4 host lattice by simply changing the kinds and concentrations of the doping rare earth ions.In this paper, the synthesis of rare earth fluoride β-NaGdF4 with multiform morphologies via a facile hydrothermal method has been fulfilled. The phases and shapes of the products can be tuned by changing the experimental parameters, including F source and pH value of mother liquor. The morphologies for the products range from submicrorods, submicrospheres, dumbbell-like nanorods, cobblestone-like particles to aggregates constructed from nanoparticles. The results indicate that F source and pH value play a critical role in determining the morphologies of the final products. Additionally, we investigate the photoluminescence (PL) properties of Ce3+/Ln3+ (LnEu, Tb and Dy) codoped down-conversion (DC) and Yb3+/Er3+ (Tm3+, Ho3+) codoped up-conversion (UC) in β-NaGdF4 host lattices. In the process of DC photoluminescence, energy transfer has occurred. This energy transfer occurs through the energy migration process like S→Gd3+→(Gd3+) n→A (S represents the sensitizer and A represents the activator) and the Gd3+ plays an intermediate role in the process.

Keywords: Rare earth fluoride; Hydrothermal synthesis; Morphologies; Photoluminescence

Electrochemical, microscopic and spectroscopic characterization of benzene diamine functionalized single walled carbon nanotube-cobalt (II) tetracarboxy-phthalocyanine conjugates by Tawanda Mugadza; Tebello Nyokong (pp. 437-447).
1,4-Benzene diamine (BDA) functionalized single walled carbon nanotubes are linked to cobalt (II) tetracarboxyl-phthalocyanine and employed in the electrochemical detection of diuron.Display Omitted► 1,4-Benzene diamine (BDA) functionalized single walled carbon nanotubes has been chemically linked to cobalt (II) tetracarboxy-phthalocyanine. ► Transmission electron microscope (TEM) images shows attachment of the phthalocyanine to single walled carbon nanotube. ► The resulting conjugate is catalytic towards the electrochemical characterization of diuron. ► The conjugate shows efficient electron transfer mediation relative to the phthalocyanine or single walled carbon nanotubes alone.In this paper we report on the synthesis and characterization of 1,4-benzene diamine (BDA) functionalized single walled carbon nanotubes linked to cobalt (II) tetracarboxy-phthalocyanine. The characterization of the conjugate was through UV–vis, FTIR and X-ray diffraction (XRD) spectroscopies and by transmission electron microscope (TEM) and electrochemical methods. The conjugate is used for the electrochemical characterization of diuron. The catalytic rate constant for diuron was 4.4×103M−1s−1 and the apparent electron transfer rate constant was 18.5×10−6cms−1. The linear dynamic range was 1.0×10−5–2.0×10−4M, with a sensitivity of ∼0.42Amol−1Lcm−2 and a limit of detection of 0.18μM using the 3δ notation.

Keywords: Single walled carbon nanotubes; 1,4-Benzene diamine; Cobalt (II) tetracarboxy-phthalocyanine; Diuron; Cyclic voltammetry; Chronoamperometry; Rotating disk electrode voltammetry; Electrochemical impedance spectroscopy

Dielectrophoretic assembly of grain-boundary-free 2D colloidal single crystals by Sejong Kim; Ramazan Asmatulu; Harris L. Marcus; Fotios Papadimitrakopoulos (pp. 448-454).
The present study deals with a dielectrophoresis (DEP) force-assisted assembly of 2D colloidal photonic crystal (PC) fabrication in a microfluidic device. In this process, negative DEP force with high-frequency electric field was used to form a colloidal crystal domain at the center of an hexapolar shape electrode without any boundary. A simple method was utilized to immobilize the single-crystal domain on the glass substrate without losing its crystallinity. This study may open up new possibilities to fabricate the simple, rapid, and high efficient colloidal PCs for various applications. Colloidal crystal growth process of 10μm microsphere (left) and its crystallinity profile (right) by DEP compression/relaxation cycles.Display Omitted► The grain-boundary-free 2D colloidal single crystalline monolayer domains with colloidal microspheres were fabricated using dielectrophoretic forces associated with hexapolar electrodes in a microfluidics. ► By appropriate manipulation of DEP/relaxation cycle, crystal growth of colloidal microspheres was facilitated to follow formation of a grain-boundary-free, single crystalline, monolayer domain of ca. 200μm in size. ► This result may open up new possibilities on colloidal photonic crystals and their manipulation in the near future.Dielectrophoresis (DEP) force-assisted assembly of a colloidal single photonic-crystal monolayer in a microfluidic chamber was demonstrated. Negative DEP force with a high-frequency AC electric field induced the compression of colloidal microspheres to form a colloidal crystal domain at the center of a hexapolar-shaped electrode. While typical assembly by monotonic DEP force forms multicrystalline domains containing crystal defects, repetitions of the DEP/relaxation cycle significantly facilitated crystal growth of 10μm monodispersed polystyrene microspheres, allowing a grain-boundary-free single-crystal monolayer domain of ca. 200μm in size. Microsphere size as well as size distribution affected the formation of the single-crystal domain. A simple method was used to immobilize the single-crystal domain on the glass substrate without losing its crystallinity.

Keywords: Colloidal photonic crystal; Dielectrophoretic assembly; Immobilization; Polyacrylamide; AC electrokinetics

Highly luminescent SiO2 beads with multiple QDs: Preparation conditions and size distributions by Ping Yang; Masanori Ando; Norio Murase (pp. 455-460).
Highly luminescent SiO2 beads with incorporated QDs were obtained, exhibiting a broad size distribution.Display Omitted► Multiple QDs were encapsulated in SiO2 beads by a reverse micelle route. ► The QDs retained their initial photoluminescence efficiency in the SiO2 beads. ► The beads displayed a broad size distribution because of a silica sol in water phase. ► Filtering was used to select different bead sizes from the broad distribution.Multiple CdTe quantum dots (QDs) were incorporated in SiO2 beads using a reverse micelle route (i.e., a water-in-oil emulsion) and a precursor solution of SiO2-coated CdTe QDs as the water phase. The QDs in the beads retained their initial photoluminescence efficiency (56%) because they had a thin SiO2 shell that prevented removal of the ligands from their surface during incorporation. Because of the SiO2 sol in the precursor solution, the size of the water pools in water-in-oil emulsion increased to 700±320nm compared to 25±5nm when an aqueous CdTe QD solution was used. The size of the beads prepared in the water pools depended strongly on the preparation parameters (water phase injection speed, tetraethyl orthosilicate concentration, reaction time). The beads were easily separated into three size ranges (60±23, 160±40, and 650±200nm) by filtering for further application.

Keywords: Quantum dots; Silica; Photoluminescence; Reverse micelle synthesis

Preparation of semiconductor-enriched single-walled carbon nanotube dispersion using a neutral pH water soluble chitosan derivative by Choolakadavil Khalid Najeeb; Jingbo Chang; Jae-Hyeok Lee; Minsu Lee; Jae-Ho Kim (pp. 461-466).
Debundling and stabilization of semiconductor-enriched SWNT suspension was acquired using a neutral pH water soluble chitosan derivative, N-acetylated chitosan. The N-groups of the polymer selectively adsorb on semiconducting nanotubes..Display Omitted► Individual suspension of SWNTs using a neutral pH water soluble chitosan derivative. ► N-groups of polymer selectively attach on semiconducting SWNTs with a weak charge transfer. ► SWNTs wrapped with biocompatible polymer are attractive for biomedical applications.Debundling and selective dispersion of semiconducting single-walled carbon nanotubes (SWNTs) has been demonstrated using a neutral pH water soluble chitosan derivative, N-acetylated chitosan (NACHI), which is synthesized by controlled N-acetylation of chitosan using acetic anhydride. The SWNT–NACHI supernatant solution demonstrated semiconductor-enriched property owing to the preferential adsorption of N-groups of the NACHI on semiconducting nanotubes with a fairly weak charge transfer. The dispersion of nearly individualized SWNTs achieved by surface modification of nanotubes with a biocompatible polymer can be utilized for electronic and biomedical applications such as field effect transistor, biosensor, cell culture medium and SWNT-biomacromolecule hybrid materials.

Keywords: Single-walled carbon nanotubes; Debundling; Semiconducting nanotubes; Individual dispersion; Chitosan derivative; Biocompatible

Stabilization mechanism of oil-in-water emulsions by β-lactoglobulin and gum arabic by Eléonore Bouyer; Ghozlene Mekhloufi; Isabelle Le Potier; Typhaine du Fou de Kerdaniel; Jean-Louis Grossiord; Véronique Rosilio; Florence Agnely (pp. 467-477).
Schematic depiction of the stabilization mechanism of oil-in-water emulsion with gum arabic through electrostatic interactions with previously adsorbed β-lactoglobulin.Display Omitted► β-lg and GA form a complex with a very strong affinity at pH 4.2. ► β-lg and GA displays interfacial adsorption and elastic behaviour. ► Both biopolymers enabled the formulation of emulsions. ► In mixed systems, GA electrostatically interacts with the initially adsorbed β-lg.Natural biopolymer stabilized oil-in-water emulsions were formulated using β-lactoglobulin (β-lg), gum arabic (GA), and β-lg:GA solutions as an alternative to synthetic surfactants. Emulsions using these biopolymers and their complexes were formulated varying the biopolymer total concentration, the protein-to-polysaccharide ratio, and the emulsification protocol.This work showed that whereas β-lg enabled the formulation of emulsions at concentration as low as 0.5 (w/w)%, GA allowed to obtain emulsions at concentrations equal to or higher than 2.5 (w/w)%. In order to improve emulsion stability, β-lg and GA were complexed through strong attractive electrostatic interactions. GA solution had to be added to previously prepared β-lg emulsions in order to obtain stable emulsions. Interfacial tension and interfacial rheological measurements allowed a better understanding of the possible stabilizing mechanism. β-lg and GA both induced a very effective decrease in interfacial tension and showed interfacial elastic behaviour. In the mixed system, β-lg adsorbed at the interface and GA electrostatically bound to it, leading to the formation of a bi-layer stabilized emulsion. However, emulsion stability was not improved compared to β-lg stabilized emulsion, probably due to depletion or bridging flocculation.

Keywords: Abbreviations; β-lg; β-lactoglobulin; GA; gum arabic; AG; arabinogalactan; GP; glycoprotein; AGP; arabinogalactan-protein; PEO; poly(ethylene oxide); ACE; affinity capillary electrophoresis; DSA; drop shape analysis; WPM; Wilhelmy plate methodβ-Lactoglobulin; Capillary electrophoresis; Emulsion; Gum arabic; Interfacial tension; Interfacial dilational rheology; Multilayer stabilization; Protein:polysaccharide complexes

Diffusion through colloidosome shells by Rachel T. Rosenberg; Nily R. Dan (pp. 478-482).
Transport of diffusants through colloidal shells is dominated by the packing density of the particles in the shell.Display Omitted► Diffusion, namely, transport of diffusants, through a colloidal shell depends on the shell thickness, colloidal particle size and packing density. ► In colloidal monolayers the rate of diffusant transport is independent of the size of the colloidal particles composing the shell. ► In colloidal multi-layers the rate of diffusant transport decreases with decreasing size of the colloidal particles composing the shell.Colloidosomes are aqueous cores surrounded by a shell composed of packed colloidal particles. Recent studies suggest that these colloidal shells reduce, or even inhibit, the transport of molecular species (diffusants). However, the effect of the colloidal shell on transport is unclear: In some cases, the reduction in transport of diffusants through the shell was found to be independent of the size of the colloidal particles composing the shell. Other studies find, however, that shells composed of small colloidal particles of order 100nm or less hindered transport of diffusants more than those composed of micro-scale colloidal particles. In this paper we present a simple diffusion model that accounts for three processes that reduce diffusant transport through the shell: (i) a reduction in the penetrable volume available for transport, which also increases the tortuousity of the diffusional path, (ii) narrow pore size which may hinder transport for larger diffusants through size exclusion, and (iii) a reduction in interfacial area due to ‘blocking’ of the surface by the adsorbed particles. We find that the colloidal particle size does not affect the reduction in transport through the colloidal shell when the shell is a monolayer. However, in closely packed, thick layers where the thickness of the multi-layer shell is fixed, the rate of transport decreases significantly with colloidal particle dimensions. These results are in excellent agreement with previously published experimental results.

Keywords: Colloidosomes; Diffusion

Adsorption of chiral aromatic amino acids onto carboxymethyl-β-cyclodextrin bonded Fe3O4/SiO2 core–shell nanoparticles by Sudipa Ghosh; A.Z.M. Badruddoza; M.S. Uddin; K. Hidajat (pp. 483-492).
Surface of magnetic silica nanoparticles is modified by grafting with carboxymethyl-β-cyclodextrin (CM-β-CD) via carbodiimide activation. .Display Omitted► Surface of magnetic silica particles is grafted with carboxymethyl-β-cyclodextrin. ► Adsorption capacities are in the order of Tryptophan>Phenylalanine>Tyrosine. ► Adsorbent offers good discrimination towards adsorption ofl andd enantiomers.Surface of magnetic silica nanoparticles is modified by grafting with carboxymethyl-β-cyclodextrin (CM-β-CD) via carbodiimide activation. The functionalized magnetic core–shell nanoparticles (MNPs) are characterized by Transmission Electron Microscopy (TEM), Fourier Transform Infra Red (FTIR) spectroscopy, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Vibrating Sample Magnetometer (VSM). These nano-sized particles are scrutinized for adsorption of certain chiral aromatic amino acid enantiomers namely,d- andl-tryptophan (Trp),d- andl-phenylalanine (Phe) andd- andl-tyrosine (Tyr) from phosphate buffer solutions. Adsorption capacities of the coated magnetic nanoparticles toward amino acid enantiomers are in the order:l-Trp>l-Phe>l-Tyr and under the same condition, adsorption capacities are higher forl-enantiomers than the correspondingd-enantiomers. All the equilibrium adsorption isotherms are fitted well to Freundlich model. FTIR studies depict significant changes after adsorption of amino acids onto nanoparticles. The stretching vibration frequencies of NH bonds of the amino acid molecules are changed with complex formation through host–guest interaction. The structure and hydrophobicity of amino acid molecules emphasize the interactions between amino acid molecules and the nano-adsorbents bearing cyclodextrin, thus play important roles in the difference of their adsorption behaviors.

Keywords: Magnetic nanoparticles; Surface functionalization; Carboxymethyl-β-cyclodextrin; Amino acids; Chiral; Adsorption

Stable aqueous dispersions of graphene prepared with hexamethylenetetramine as a reductant by Xiaoping Shen; Lei Jiang; Zhenyuan Ji; Jili Wu; Hu Zhou; Guoxing Zhu (pp. 493-497).
Highly stable graphene aqueous dispersions were synthesized by chemical reduction of graphene oxide with an environmentally friendly reagent of hexamethylenetetramine (HMTA) without the assistance of polymeric or surfactant stabilizers.Display Omitted► Stable graphene aqueous dispersion was achieved with hexamethylenetetramine as a reducer. ► Neither organic stabilizer nor pH control was needed in the reduction process. ► A plausible mechanism is proposed. ► This green method can facilitate the creation and use of new graphene-based materials.Highly stable graphene aqueous dispersions were achieved by chemical reduction of graphene oxide with an environmentally friendly reagent of hexamethylenetetramine (HMTA). By this method, chemical reduction as well as dispersion of graphene can be carried out in one step without the need of organic stabilizers or pH control. The as-synthesized products were characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy, scanning and transmission electron microscopy, and thermogravimetry and differential scanning calorimetry. It is revealed that the bulk of the oxygen-containing functional groups were removed from graphene oxide via HMTA reduction, and stable aqueous colloidal dispersions of graphene have a concentration up to ca. 0.65mg/mL. Moreover, it is found that the freshly precipitated graphene nanosheets can be re-dispersed in water with simple ultrasonic treatment. A mechanism for the formation of stable graphene colloidal dispersions is proposed. This simple and green approach should find practical applications in the preparation of graphene-based nanocomposites with a facile and low-cost solution processing technique.

Keywords: Graphene; Graphene oxide; Hexamethylenetetramine; Synthesis

Colloidal stability of oleic- and ricinoleic-acid-coated magnetic nanoparticles in organic solvents by Sašo Gyergyek; Darko Makovec; Miha Drofenik (pp. 498-505).
Overall energy of interaction between two oleic- and ricinoleic-acid-coated nanoparticles in different organic solvents. The additional repulsion between the ricinoleic-acid-coated nanoparticles exist, because of the polar interactions, in contrast to the oleic-acid-coated nanoparticles.Display Omitted► Colloidal stability of suspensions is correlated to dielectric constant of solvent. ► OA-nanoparticles cannot be dispersed in solvents that have ε > 5. ► RA-nanoparticles can be dispersed in solvents that have ε > 5. ► RA-nanoparticles are electron-acceptors; OA- nanoparticles are electron-donors. ► Solvation forces improved colloidal stability of RA-nanoparticles.The colloidal stability of oleic- and ricinoleic-acid-coated nanoparticles in organic solvents with dielectric constants εr ranging from 2.0 to 9.8 was studied. Although the acids are structurally similar, there is anOH group in the ricinoleic acid’s tail, a marked improvement in the colloidal stability of the ricinoleic-acid-coated magnetic nanoparticles in moderately polar organic solvents and monomer methyl methacrylate was observed as a result. The bonding of both acids provokes a significant change in the surface properties of the iron-oxide nanoparticles. A clear shift from a strong electron-donor to a weak electron-donor was confirmed with the bonding of the oleic acid. The effect of ricinoleic acid bonding is even more dramatic: a clear shift toward a weak electron-acceptor is evident. A detailed analysis of the total energy of interaction, including the vOCG theory, between two particles was used to describe the different behaviors of the coated nanoparticles. In the case of the oleic acid nanoparticles in an apolar medium, such as decane, a small net attraction of ∼0.84 kB T, which is insufficient to cause nanoparticles agglomeration, exists. In polar media the net attraction is larger than 1.5 kB T, resulting in precipitation of the oleic-acid-coated nanoparticles. The same findings apply to the ricinoleic-acid-coated nanoparticles, but only when dispersed in the apolar medium. In the polar medium an additional repulsion due to polar solvation forces exists, resulting in a decrease of the net attraction to as low as ∼0.14 kB T.

Keywords: Magnetic nanoparticles; Colloidal suspensions; Acid-base theory; Contact angle; Surface free energy

Synthesis of core–shell polystyrene nanoparticles by surfactant free emulsion polymerization using macro-RAFT agent by Niranjan Yeole; Dilip Hundiwale; Tushar Jana (pp. 506-510).
The harsh sulfonation approach for forming core (polystyrene)-shell (polystyrene sulfonate) nanoparticles has been replaced with a novel surfactant free emulsion polymerization using macro-RAFT agent.Display Omitted► Synthesis of core (polystyrene)-shell (polystyrene sulfonate) nanoparticles. ► Surfactant free emulsion polymerization using macro-RAFT agent. ► Harsh sulfonation method has been replaced.Novel approach for the synthesis of core–shell polystyrene nanoparticles by living hydrophilic polymer consisting of thiocarbonyl thio end group is reported. The surfactant free emulsion polymerization of styrene in the presence of macro-RAFT (reversible addition fragmentation chain transfer) agent is carried out to synthesize stable latex particles with smaller particle size. A macro-RAFT agent is prepared by homopolymerization of sodium styrene sulfonate (NaSS) in aqueous phase by using dithioester as chain transfer agent. This synthesized polystyrene sulfonate–sodium (PSS–Na) based macro-RAFT agent, which is essentially water soluble macromolecular chain transfer agent used for the surfactant-free batch emulsion polymerization of styrene. Transmission electron microscopy (TEM) study of the synthesized colloids shows the narrow particle size distribution with core–shell morphology.

Keywords: Core–shell particles; Surfactant free emulsion polymerization; Macro-RAFT agent; RAFT polymerization; Polystyrene

Structural and spectroscopic investigation of ZnS nanoparticles grown in quaternary reverse micelles by Haresh G. Manyar; Patrizia Iliade; Luca Bertinetti; Salvatore Coluccia; Gloria Berlier (pp. 511-516).
Crystalline ZnS nanoparticles were grown within the aqueous core of reverse micelles stabilized by the presence of alcohol molecules at the water/oil interface.Display Omitted► Synthesis of ZnS nanoparticles in quaternary reverse micelles. ► Influence of synthesis parameters on the particle size, stability and polydispersity. ► Particle size estimation from UV–Vis spectroscopy and HRTEM.ZnS nanoparticles were synthesized in four component “water in oil” microemulsions formed by a cationic surfactant (cetyltrimethylammonium bromide, CTAB), a cosurfactant (pentanol or butanol), n-hexane and water. The effect of various parameters (nature of cosurfactant, water/surfactant W0, and alcohol/surfactant P0) on the formation and stability of ZnS nanoparticles was investigated thoroughly. UV–Vis spectroscopy was employed to directly follow the formation of ZnS systems in the microemulsions. Thus, particle size was estimated from the position of the first excitonic transition by employing an approximate finite-depth equation and an empirical correlation, giving average diameters in the ranges 2.3–2.5 and 3.0–3.5nm, respectively. Stable ZnS nanoparticles were obtained by employing low water and high cosurfactant amounts. This suggests that at high concentration the cosurfactant molecules act as capping agents on the surface of the inverse micelles, while low water amounts are needful to obtain water droplets with a radius close to that of the interfacial film spontaneous curvature. HRTEM analysis showed that the samples are formed by a few crystalline ZnS nanoparticles of spherical shape, embedded in and amorphous organic matrix, with a coherent scattering domain between 2 and 4nm.

Keywords: w/o Microemulsion; Reverse micelles; Cosurfactant; Zinc sulfide; UV–Vis spectroscopy; HRTEM

A comprehensive study of the spontaneous formation of nanoassemblies in water by a “lock-and-key” interaction between two associative polymers by Mohammad Othman; Kawthar Bouchemal; Patrick Couvreur; Didier Desmaële; Estelle Morvan; Thierry Pouget; Ruxandra Gref (pp. 517-527).
Schematic representation of spherically-shaped nanoassemblies resulting from the association of two water soluble polymers: i) alkylated dextran (in molecular or in micellar form) and ii) cyclodextrin polymer.Display Omitted► Nanoassemblies (NAs) with well-defined diameters were spontaneously formed in water according to an entropy-driven process after mixing a two associative water soluble polymers (cyclodextrin polymer and dextran grafted with alkyl side chains) ► The hydrophobic interaction between C12 and the hydrophobic cavities of CDs was the main driving force for NAs’ formation, with a minor contribution arising from van der Waals’ interactions. ► The strong lock and key interactions between the two polymers are restricted neither by the dextran substitution yield, nor by its micellization in water.Nanoassemblies (NAs) with sizes ranging from 60 to 160nm were spontaneously formed in water after mixing a host polymer (polymerized cyclodextrin (pβ-CD)) and a guest polymer (dextran grafted with lauroyl side chains (MD)). The combination of microscopy, dynamic light scattering (DLS), nuclear magnetic resonance (1H NMR), isothermal titration calorimetry (ITC) and molecular modelling was used to investigate the parameters which govern the association between MD and pβ-CD. Remarkably, when pβ-CD was progressively added to a solution of MD, NAs with a well-defined diameter were spontaneously formed and their diameter was constant whatever the composition of the system. According to NMR data, almost all the alkyl chains of MD were included into CDs’ cavities of the polymer when the molar ratio lauroyl chain (C12)/CD was ⩾1. The hydrophobic interaction between C12 and the hydrophobic cavities of CDs appears as the main driving force for NAs’ formation, with a minor contribution arising from van der Waals’ interactions. The inclusion of C12 into β-CD cavities is almost a completely enthalpy-driven process, whereas the MD-C12/pβ-CD interaction was found to be an entropy-driven process. Major conclusions which can be drawn from these studies are that the interactions between the two polymers are restricted neither by the MD substitution yield, nor by the micellization of MD. The simultaneous effects of several CD linked together in pβ-CD and of many alkyl chains grafted on dextran were necessary to generate these stable NAs.

Keywords: Abbreviations; CAC; critical association concentration; CDs; cyclodextrins; Δ; G; Gibbs free energy; Δ; H; enthalpy changes; Δ; S; entropy changes; DLS; dynamic light scattering; FFEM; freeze fracture electron microscopy after; ITC; isothermal titration microcalorimetry; K; the constants of association; MD; modified dextran with lauroyl side chains; mM; millimole; NMR; nuclear magnetic resonance; N; stoichiometry of the interactions; NAs; nanoassemblies; Pβ-CD; polymer of beta cyclodextrin; PDI; polydispersity index; SD; standard deviation; SDS; sodium dodecyl sulphateHydrophobized dextran; Poly beta cyclodextrin; Isothermal titration microcalorimetry; NMR; Associative polymer; Nanoassemblies

Novel cationic 6-lauroxyhexyl lysinate modified poly(lactic acid)–poly(ethylene glycol) nanoparticles enhance gene transfection by Chunxi Liu; Zhijin Chen; Wangyang Yu; Na Zhang (pp. 528-535).
LHLN was fabricated onto PLA–PEG nanoparticles as a charge modifier to obtain LHLN–PLA–PEG NPs which could condense pDNA thoroughly and showed higher transfection efficiency and lower cytotoxicity than Lipofectamine.Display Omitted► A novel cationic surfactant, LHLN was synthesized. ► LHLN was successfully fabricated onto PLA–PEG nanoparticles. ► LHLN modified PLA–PEG nanoparticles could condense DNA thoroughly into NPs/DNA complexes. ► Results of cell toxicity and transfection efficiency are extremely promising. ► LHLN–PLA–PEG NPs hold the potential to be one of the most promising candidates of non-viral nanodevice.The leading principle of non-viral delivery systems for gene therapy is to mediate high levels of gene expression with low cytotoxicity. Nowadays, biodegradable nanoparticles formulated with poly(lactic acid)–poly(ethylene glycol) (PLA–PEG) were wildly developed. However, the relative lower gene transfection efficiency and higher cytotoxicity still remained critical problems. To address these limitations, PLA–PEG nanoparticles have been composited with other components in their formulation. Here, a novel cationic lipid, 6-lauroxyhexyl lysinate (LHLN), was fabricated onto PLA–PEG nanoparticles as a charge modifier to improve the transfection efficiency and cytotoxicity. The obtained cationic LHLN modified PLA–PEG nanoparticles (LHLN–PLA–PEG NPs) could condense pDNA thoroughly via electrostatic force, leading to the formation of the LHLN–PLA–PEG NPs/pDNA complexes (NPs/DNA complexes). The nanoparticles obtained have been characterized in relation to their physicochemical and biological properties, and the results are extremely promising in terms of low cell toxicity and high transfection efficiency. These results indicated that the novel cationic LHLN modified PLA–PEG nanoparticles could enhance gene transfection in vitro and hold the potential to be a promising non-viral nanodevice.

Keywords: Cationic nanoparticles; Poly(lactic acid)–poly(ethylene glycol); 6-Lauroxyhexyl lysinate; Non-viral gene vector

Bi-functional gold-coated magnetite composites with improved biocompatibility by Maria Arsianti; May Lim; Shi Nee Lou; Ian Y. Goon; Christopher P. Marquis; Rose Amal (pp. 536-545).
TEM micrographs of ultra-thin section of BHK21 cells at 48h post-magnetofection with gold coated and bare MNP vectors. The figures show the nuclear membrane bulging inwards for vectors uptake and final localization of vectors in the cell nucleus for gene expression.Display Omitted► Efficacy of gold-modified magnetic gene delivery vector in cellular therapy research. ► Magnetically-driven gene delivery vehicle and as an intracellular imaging agent.► Bare and gold-coated magnetite vectors under TEM showed localization in cell nucleus for gene expression and elucidated nuclear uptake mechanism.The effect of gold attachment on the physical characteristics, cellular uptake, gene expression efficiency, and biocompatibility of magnetic iron oxide (MNP) vector was investigated in vitro in BHK21 cells. The surface modification of magnetite with gold was shown to alter the morphology and surface charge of the vector. Nonetheless, despite the differences in the surface charge with and without gold attachment, the surface charge of all vectors were positive when conjugated with PEI/DNA complex, and switched from positive to negative when suspended in cell media containing serum, indicating the adsorption of serum components onto the composite. The cellular uptake of all MNP vectors under the influence of a magnetic field increased when the composite loadings increased, and was higher for the MNP vector that was modified with gold. Both bare magnetite and gold-coated magnetite vectors gave similar optimal gene expression efficiency, however, the gold-coated magnetite vector required a 25-fold higher overall loading to achieve a comparable efficiency as the attachment of gold increased the particle size, thus reducing the surface area for PEI/DNA complex conjugation. The MNP vector without gold showed optimal gene expression efficiency at a specific magnetite loading, however further increases beyond the optimum loading decreased the efficiency of gene expression. The drop in efficiency at high magnetite loadings was attributed to the significant reduction in cellular viability, indicating the bare magnetite became toxic at high intracellular levels. The gene expression efficiency of the gold-modified vector, on the other hand, did not diminish with increasing magnetite loadings. Intracellular examination of both bare magnetite and gold-coated magnetite vectors at 48h post-magnetofection using transmission electron microscopy provided evidence of the localization of both vectors in the cell nucleus for gene expression and elucidated the nuclear uptake mechanism of both vectors. The results of this work demonstrate the efficacy of gold-modified vectors to be used in cellular therapy research that can function both as a magnetically-driven gene delivery vehicle and an intracellular imaging agent with negligible impact on cell viability.

Keywords: Gold; Cell viability; Gene vector; Imaging; Magnetite

Influence of individual ionic components on the agglomeration kinetics of silver nanoparticles by J.S. Gebauer; L. Treuel (pp. 546-554).
Size distributions of silver NPs are determined (left) and the influence of individual ionic components on the agglomeration behavior (middle) and the H-bonding structure of water (right) studied.Display Omitted► Individual ionic contribution to the destabilization of colloidal silver nanoparticles. ► Determination of elemental charges on colloidal NPs. ► Concentration-dependent determination of ion-induced agglomeration rates. ► Ionic influence on the water near structure.The precise characteristic of the agglomeration behavior of colloidal suspensions is of paramount interest to many current studies in nanoscience. This work seeks to elucidate the influence that differently charged salts have on the agglomeration state of a Lee–Meisel-type silver colloid. Moreover, we investigate the influence of the chemical nature of individual ions on their potential to induce agglomeration. Raman spectroscopy and surface-enhanced Raman spectroscopy are used to give insights into mechanistic aspects of the agglomeration process and to assess the differences in the influence of different salts on the agglomeration behavior. Finally, we demonstrate the potential of the measurement procedure used in this work to determine the elementary charge on colloidal NPs.

Keywords: Silver nanoparticles; Agglomeration kinetics; Brownian motion; Raman spectroscopy

Synthesis and physical properties of new surfactants based on ionic liquids: Improvement of thermal stability and mechanical behaviour of high density polyethylene nanocomposites by Sébastien Livi; Jannick Duchet-Rumeau; Thi Nhàn Pham; Jean-François Gérard (pp. 555-562).
TEM micrographs of (a) PE/MMT-P I, (b) PE/MMT-P Br, (c) PE/MMT-PPF6-.Display Omitted► Synthesis of new surfactants for the olefinic matrices. ► Preparation of thermostable ionic liquid (IL) modified montmorillonites. ► Improvement of thermal and mechanical properties of nanocomposites.Ionic liquids based on alkyltriphenyl phosphonium and dialkyl imidazolium cations with long alkyl chains have been synthesized and used as new surfactants for cationic exchange of layered silicates. The influence of the alkyl chain length and the chemical nature of the conteranion or of the cation on the thermal stability of these new intercalating agents and on imidazolium- (MMT-I) or phosphonium- (MMT-P) modified montmorillonites have been analyzed by thermogravimetric analysis (TGA). Thermoplastic nanocomposites based on these modified montmorillonites with a very low amount of nanofillers (1wt.%) have been processed by melt mixing using a twin screw extruder. The distribution of the clay layers in a high density polyethylene (HDPE) matrix was characterized and finally the mechanical and thermal properties of the corresponding nanocomposites were determined.

Keywords: Ionic liquids; Organoclay; Cationic exchange; Polyethylene; Nanocomposites

Growth kinetics of sulfur nanoparticles in aqueous surfactant solutions by Rajib Ghosh Chaudhuri; Santanu Paria (pp. 563-569).
Coarsening rate constant ( kc) of sulfur nanoparticle formation decreases nonlinearly with the increasing surfactant (SDBS) concentration.Display Omitted► Coarsening rate constant (k c) increases linearly with the reactant concentration. ► The value ofk c is low in organic acid media compare to inorganic acid. ►k c decreases nonlinearly till CMC of the surfactant and remains constant above CMC.Sulfur is an important element has many practical applications when present as nanoparticles. Despite the practicable applications, limited studies are available in the literature related to synthesis of sulfur nanoparticles. Growth kinetics of colloidal sulfur particles synthesized from aqueous solutions using different surfactants have been studied here. The effects of different parameters such as reactant concentration, temperature, sonication, types of acids, types of surfactants, and even surfactant concentration are studied on the growth kinetics. Since the reaction rate is fast, particle growth depends on the parameters which affect diffusion of sulfur molecules. There is a linear relationship found among the reactant concentration and the particle coarsening rate constant. The growth kinetics was studied in the presence of different surfactants such as nonionic (poly(oxyethylene) p-tert-octylphenyl ether, TX-100), anionic (sodium dodecylbenzene sulfonate, SDBS), cationic (cetyltrimethyammonium bromide, CTAB) and results show the coarsening constant changes according to the following order: water>TX-100>SDBS>CTAB. The particle growth rate also depends on the surfactant concentration, coarsening rate constant decreases with the increase in surfactant concentration and become constant close to the critical micellar concentration (CMC). The coarsening rate constant also highly depends on the types of acid used as catalyst.

Keywords: Growth kinetics; Nucleation; Coarsening constant; Diffusion coefficient

Nucleating effect of calcium stearate coated CaCO3 nanoparticles on polypropylene by Yong Lin; Haibin Chen; Chi-Ming Chan; Jingshen Wu (pp. 570-576).
Monolayer-coating surface is more effective to induce crystallization of polypropylene.Display Omitted► Monolayer-coated calcium carbonate nanoparticles have the strongest nucleating effect on polypropylene (PP). ► A monolayer stearate coating remains as a rigid layer at high temperatures, serving as nucleation sites for PP. ► Good dispersion of monolayer-coated nanoparticles provides the maximum number of nucleation sites. ► Sub-monolayer coatings, which are soft layers at higher temperatures, do not provide effective nucleation sites.The ability of stearate coated calcium carbonate nanoparticles to promote the nucleation of polypropylene (PP) was investigated systematically. The effects of surfactant coverage and CaCO3 particle concentration were explored using differential scanning calorimetry as well as optical and atomic microscopies. The results indicate that at the crystallization temperature of PP, a monolayer stearate coating remains as a rigid layer and provides a noticeable nucleating effect. Insufficient or excess coating diminishes the nucleating effect, the former because of the formation of agglomerates, and the latter by forming a soft layer at the PP/CaCO3 interface at high temperatures, leading to the weak nucleating ability. Monolayer-coated nanoparticles had the strongest nucleating effect. The crystallization temperature and crystallization rate increased with the concentration of the monolayer-coated nanoparticles up to 40wt.%.

Keywords: Polypropylene; CaCO; 3; Nanocomposites; Nanoparticles; Crystallization; Coating coverage

Ultrafast growth of dendritic gold nanostructures and their applications in methanol electro-oxidation and surface-enhanced Raman scattering by Xinyi Han; Dawei Wang; Jianshe Huang; Dong Liu; Tianyan You (pp. 577-584).
Dendritic gold nanostructures with hyperbranched architecture, sea-urchinlike and flowerlike gold nanostructures were presented at room temperature. The dendritic gold nanostructures exhibited both a good electrocatalytic activity toward the oxidation of methanol and a good SERS activity.Display Omitted► Dendritic, sea-urchinlike and flowerlike gold nanostructures. ► Room temperature. ► Good electro-oxidation of methanol and SERS activity.A simple and rapid solution-phase synthesis of dendritic gold nanostructures with hyperbranched architecture is demonstrated in this report. Further investigations revealed that the morphology of the synthesized sample depended on proper parameters such as reagent concentration, reaction temperature, reagent addition sequence and stir. Moreover, the dendritic gold nanostructures exhibited a good electrocatalytic activity toward methanol electro-oxidation. When compared with sea-urchinlike and flowerlike gold nanostructures which were prepared by varying the parameters of experiment, dendritic gold nanostructures showed the highest surface-enhanced Raman scattering (SERS) sensitivity using 4-aminothiophenol (4-ATP) as probe molecules. The dendritic gold nanostructures may find potential applications in catalysis, SERS and biosensor.

Keywords: Dendritic gold nanostructure; Methanol; Electro-oxidation; SERS

Responsive polymer/gold nanoparticle composite thin films fabricated by solvent-induced self-assembly and spin-coating by Dongxiang Li; Ji Yong Lee; Dong Ha Kim (pp. 585-591).
Responsive composite gold nanofilms were fabricated by cooperative self-assembly of poly(4-vinylpyridine) grafted gold nanoparticles (Au NPs) and poly(4-vinylpyridine)- b-polystyrene block copolymers.Display Omitted► Cooperative self-assembly of responsive Au NPs and block copolymers was demonstrated. ► Composite Au thin films consisting of PVP-hybridized Au NPs and PS- b-PVP micelles were generated. ► Thin Au films have responsive surface plasmon resonance and morphology changes to vapor molecules.Self-assembled poly(4-vinylpyridine)-grafted gold (Au) nanoparticles (NPs) and polystyrene- b-poly(4-vinylpyridine) block copolymers were fabricated by the introduction of a selective solvent to a common solution. The assembled mixtures were spin-coated onto solid substrates to fabricate composite gold/polymer thin films composed of copolymer-hybridized Au NPs and independent copolymer micelles. The obtained composite Au thin films had variable localized surface plasmon resonance (LSPR) bands and microscopic morphologies upon vapor annealing with selective solvents because the adsorption and dissolving of solvent molecules into the films could rearrange the copolymer block. The hybrid nanostructured Au thin films may have potential in vapor sensing and organic assays.

Keywords: Gold thin films; Block copolymer; Self-assembly

Ultra small Gd2O3 nanoparticles: Absorption and emission properties by A.T.M. Anishur Rahman; Krasimir Vasilev; Peter Majewski (pp. 592-596).
We synthesize ultra small (1–3 nm) Gd2O3 nanoparticles by a facile method which requires lower temperature and shorter synthesis time. These nanoparticles induce phosphorescence from ethylene glycol and citric acid.Display Omitted► A new, facile method for synthesis of ultra small (1–3nm) Gd2O3 nanoparticles. ► The amount of citric acid strongly affects the size of the nanoparticles. ► The Gd2O3 nanoparticles show four characteristic absorption peaks in the UV regions. ► The Gd2O3 nanoparticles induce phosphorescence from ethylene glycol and citric acid.In this paper, we report a facile method for synthesis of ultra small (1–3nm) gadolinium oxide (Gd2O3) nanoparticles using citric acid (CA) as a capping agent. The dependence of nanoparticle (NP) size on the ratio between CA and gadolinium (Gd) is investigated. Absorption properties of the ultra small Gd2O3 NPs in UV region have four characteristic peaks at 312nm, 274nm, 253nm and 228nm. Finally, we show that the Gd2O3 nanoparticles synthesized by this method induce triplet emission (phosphorescence) from CA and EG in the NIR region.

Keywords: Gadolinium oxide nanoparticles; Heavy atom impact; Phosphorescence; MRI; Optical imaging; Multimodal imaging

Shape-selective formation and characterization of catalytically active iridium nanoparticles by Subrata Kundu; Hong Liang (pp. 597-606).
Iridium (Ir) nanoparticles (NPs) of variable shapes have been synthesized for the first time via reduction of Ir(III) ions in CTAB micellar media containing alkaline 2,7-DHN under 4 hour of UV-irradiation. The one-step process exclusively generates different shapes, such as nano-spheres, nano-chains, nano-flakes, and nano-needles. The synthesized Ir NPs are stable for more than a month in ambient conditions. The particles’ morphology can be tuned by simply changing the surfactant-to-metal ion molar ratios and altering other reaction parameters. The mechanisms of the Ir particle formation and effects of different reaction parameters are studied in detail. The Ir nano-needles serve as a good catalyst for the reduction of organic dye molecules in the presence of NaBH4. The catalysis rate was compared by considering the electron transfer process during reduction. The present method would lead to a quick process for the synthesis of other mono-metallic, composite, and semiconductor particles with variable shapes. The Ir NPs will find promising applications in different types of organic and inorganic catalysis reactions, nanoelectronics, and biomedical applications.Display Omitted► Shape control synthesis of nanostructured materials shows potential applications in nanoelectronic and optoelectronic devices; catalysis; and structural composites. ► Ir NPs are of particular interest because they used as excellent catalyst in many catalysis reactions. ► A one-step in-situ approach for synthesis of Ir NPs with variable shapes under 4 hour of UV-irradiation. ► The synthesized Ir NPs serve as a good catalyst for the reduction of organic dye molecules in the presence of NaBH4.Iridium (Ir) nanoparticles (NPs) of variable shapes have been synthesized via the reduction of Ir(III) ions in CTAB micellar media containing alkaline 2,7-DHN under 4h of UV-irradiation. The one-step process generates different shapes, such as nano-spheres, nano-chains, nano-flakes, and nano-needles. The synthesized Ir NPs are stable for more than a month in ambient conditions. The particles’ morphology can be tuned by simply changing the surfactant-to-metal ion molar ratios and altering other reaction parameters. The mechanisms of the Ir particle formation and effects of different reaction parameters were studied in detail. The Ir nano-needles serve as a good catalyst for the reduction of organic dye molecules in presence of NaBH4. The catalysis rate was compared by considering the electron transfer process during the reduction of the dye molecules. The present method would lead to a quick process for the synthesis of other mono-metallic, composite, and semiconductor particles with variable shapes. The Ir NPs will find promising applications in different types of organic and inorganic catalysis reactions, nanoelectronics, and biomedical applications.

Keywords: Ir nanoparticles (NPs); CTAB; UV-photoirradiation; Nano-needles; Catalysis

Facile synthesis and catalytic activity of MoS2/TiO2 by a photodeposition-based technique and its oxidized derivative MoO3/TiO2 with a unique photochromism by Shigeki Kanda; Tomoki Akita; Musashi Fujishima; Hiroaki Tada (pp. 607-610).
The MoS2/TiO2 and MoO3/TiO2 heterojunctions prepared by the photodeposition-based technique show a high photocatalytic activity for H2 generation and a unique photochromic property, respectively.Display Omitted► UV-light irradiation to TiO2 in an (NH4)2MoS4 aqueous ethanol solution yields MoS2 nanoparticles on TiO2 (MoS2/TiO2). ► The MoS2 nanoparticles are transformed into molecular MoO x species by air oxidation. ► The MoS2/TiO2 system exhibits a high photocatalytic activity for H2 generation. ► The m-MoO3/TiO2 system shows unique photochromism.UV-light irradiation to TiO2 in an aqueous ethanol solution of (NH4)2MoS4 under deaerated conditions has yielded molybdenum(IV) sulfide nanoparticles on a TiO2 surface (MoS2/TiO2) to be transformed into molybdenum(VI) oxide species highly dispersed at a molecular level by a subsequent heating at 773K in air (m-MoO3/TiO2). In HCOOH aqueous solutions, the MoS2/TiO2 system exhibits a high level of photocatalytic activity for H2 generation, while the m-MoO3/TiO2 system shows unique photochromism.

Keywords: Single precursor photodeposition; Photocatalysis; Photochromism; Metal oxide; Metal chalcogenide

Colloidal systems of silver nanoparticles and high-regioregular cationic polythiophene with ionic-liquid-like pendant groups: Optical properties and SERS by Samrana Kazim; Jiří Pfleger; Marek Procházka; Dmitrij Bondarev; Jiří Vohlídal (pp. 611-619).
New water-soluble regioregular cationic polythiophene was prepared and used for aggregation of silver nanoparticles into assemblies with localized surface plasmon effects.Display Omitted► Aggregation of plasmonic silver nanoparticles by adsorption of cationic polythiophene due to electrostatic interactions. ► The aggregation is controlled to provide “hot spots” with strong electromagnetic field enhancement. ► Presence of “hot spots” was evidenced by SERS measurements. ► Nanoparticles quench fluorescence efficiently only at low polymer concentrations.We report tuning of structure dependent optical properties of colloidal systems of borate-stabilized silver nanoparticles (Ag NPs) and polythiophene-based cationic polyelectrolyte with ionic-liquid like side groups: poly{3-[6-(1-methylimidazolium-3-yl)hexyl]thiophene-2,5-diyl bromide} (PMHT-Br) towards obtaining local electromagnetic field enhancement effects. Surface-enhanced Raman scattering (SERS) studies showed that the strong electromagnetic field enhancement is related to the formation of aggregates of Ag NPs achieved at the components ratio providing the charge balance between Ag NPs and cationic polythiophene, at which Ag NPs are nearly single-polymer-layer coated, their zeta potential is close to zero and they easily form aggregates in which the mean inter-particle distance enables the occurrence of desired plasmonic effects. Fluorescence quenching is efficient only in the systems with low concentrations of PMHT-Br, in which almost all polymer chains directly interact with the Ag NPs surface.

Keywords: Ionic conjugated polymer; Polythiophene polyelectrolyte; Plasmonic nanoparticle; Fluorescence quenching; SERS

Precipitation of dispersed silver particles using acetone as reducing agent by Ionel Halaciuga; Sylas LaPlante; Dan V. Goia (pp. 620-623).
Dispersed silver particles were obtained by reducing silver oxide with acetone. The generation of the electrons needed for the reduction is facilitated catalytically by Ag2O under highly alkaline conditions.Display Omitted► Novel environmentally friendly route for obtaining dispersed Ag particles. ► Acetone reduces rapidly and completely silver oxide in alkaline aqueous solutions. ► Ag2O catalyzes the abstraction of the α-hydrogen in the acetone’s methyl groups and the release of electrons needed for the reduction.A novel environmentally friendly solution-based method for preparing dispersed silver particles is described. The simple and convenient approach consists in heating silver oxide particles dispersed in a highly alkaline water/acetone mixture. The data presented clearly show that acetone reduces completely and rapidly Ag2O particles to metallic silver at 60°C. A mechanism explaining the provenance of the electrons responsible for the reduction of silver is proposed.

Keywords: Silver; Acetone; Metallic particles; Electronic material

Separating nanoparticles from microemulsions by Muhammad Faizan Nazar; Olesya Myakonkaya; Syed Sakhawat Shah; Julian Eastoe (pp. 624-629).
Nanoparticles synthesised in water-in-oil microemulsions can be easily separated from the reaction medium by steep dilution with water.Display Omitted► A low-energy, isothermal, easy to apply and cost-effective purification route for processing inorganic nanoparticles from microemulsions is described. ► A water-induced separation can be used to recover nanoparticles from the reaction medium “at the flick of a switch”. ► This water dilution method appears to be quite general.Water-in-oil microemulsions (w/o μEs) stabilized by the cationic surfactant cetyltrimethylammonium chloride (CTACl) have been used as reaction media to generate Au nanoparticles (Au-NPs). In addition the pure μEs have been used as media to disperse Au and Pd-NPs, which have been pre-synthesised in aqueous phases and stabilized by sodium 2-mercaptoethanesulfonate (MES) ligands, and also commercially available SiO2-NPs. A general method for recovery and separation of the nanoparticles from these mixed NP-μE systems has been demonstrated by tuning phase behavior of the background microemulsions. Addition of appropriate aliquots of water drives a clean liquid–liquid phase transition, resulting in two macroscopic layers, the NPs preferentially partition into an upper oil-rich phase and are separated from excess surfactant which resides in a lower aqueous portion. UV–vis and1H NMR spectroscopy have been used to follow these separation processes and quantify the recovery and recycle efficiencies for the different NPs. For example, ∼90% of the microemulsion-prepared Au-NPs can be recovered; with even greater separation efficiencies attainable for pre-synthesised MES-stabilized Au-MES-NPs (∼98%) and Pd-MES-NPs (92%). For the silica NP-μE dispersions gravimetry indicates ∼84% recovery of the NPs. TEM images of all systems showed that NP shapes and size distributions were generally preserved after these phase transfer processes. This low-energy and cost-effective purification route appears to be a quite general approach for processing different inorganic NPs, having advantages of being isothermal, using only commercially available inexpensive components and requiring no additional organic solvents.

Keywords: Microemulsions; Nanoparticles; Nanoparticle separation

BiOBr hierarchical microspheres: Microwave-assisted solvothermal synthesis, strong adsorption and excellent photocatalytic properties by Lei Zhang; Xiao-Feng Cao; Xue-Tai Chen; Zi-Ling Xue (pp. 630-636).
Two kinds of BiOBr hierarchical microspheres were successfully prepared via a facile microwave-assisted solvothermal route. These two samples exhibited strong adsorption abilities and excellent photocatalytic activities.Display Omitted► Two kinds of BiOBr nanosheets-assembled microspheres were successfully prepared via a facile, rapid and reliable microwave-assisted solvothermal route, employing Bi(NO3)3·5H2O and cetyltrimethylammonium bromide as starting reagents in the absence or presence of oleic acid. ► The formation of these building blocks of microspheres could be ascribed to the self-assembly of nanoparticles according to mesocrystal growth mode. ► Both samples exhibited not only strong adsorption abilities, but also excellent photocatalytic activities for methyl orange, rhodamine B and phenol. These BiOBr hierarchical microspheres are very promising adsorbents and photocatalysts for the treatment of organic pollutants.Two kinds of BiOBr nanosheets-assembled microspheres were successfully prepared via a facile, rapid and reliable microwave-assisted solvothermal route, employing Bi(NO3)3·5H2O and cetyltrimethylammonium bromide (CTAB) as starting reagents in the absence or presence of oleic acid. The phase and morphology of the products were characterized by powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). Experiments indicated that the formation of these building blocks of microspheres could be ascribed to the self-assembly of nanoparticles according to mesocrystal growth mode. Interestingly, both samples exhibited not only strong adsorption abilities, but also excellent photocatalytic activities for methyl orange (MO), rhodamine B (RhB) and phenol. The resulting BiOBr hierarchical microspheres are very promising adsorbents and photocatalysts for the treatment of organic pollutants.

Keywords: Microstructure; Mesocrystal; Photocatalytic

Chitosan colloidal suspension composed of mechanically disassembled nanofibers by Dagang Liu; Peter R. Chang; Mindong Chen; Qinglin Wu (pp. 637-643).
Chitosan nanofibers, defibrillated by wet mechanical treatment, presented the diameter of about 50nm. These nanofibers were aligned layer by layer to assemble into nematic liquid crystals phase in the colloidal suspension. After being freeze-dried, porous and layered sponge formed from the liquid crystal suspension.Display Omitted► Chitosan nanofibers are prepared by wet-grinding and high-pressure homogenizer. ► Disassembled microfibrils have diameter of about 50nm. ► Nematic liquid crystal phase exhibits in nanofibrous suspension. ► Chitosan sponge has a porous, layered structure.Joint treatments of wet-grinding and high-pressure homogenization effectively disassembled chitosan particles into nanofibers by breaking the bond interactions between the chitosan crystalline fibrils using only strong mechanical force. We demonstrated the size reduction of chitosan fibers and characterized the properties and structure of the obtained nanofibrils. Results showed that the obtained nanofibers had a diameter of about 50nm, which comprised small bundles of nanofibrils with a diameter of 1–5nm. The zeta potential, viscosity, and stability of the nanofibrous suspension were studied and found to be dependent on the pH value of the aqueous media. Optical properties of the suspension were also characterized. After an isotropic-nematic phase transition, the chitosan nanofibrous colloids exhibited a nematic liquid crystal structure due to the layer-by-layer stacking of self-aligned nanofibers. The freeze-dried liquid crystalline colloids were shaped like a sponge with a wide-range of pore sizes and large surface areas, which could serve as an ideal tissue scaffold.

Keywords: Chitosan; Nanofiber; Porous sponge; Liquid crystal

Temperature induced phase separation of luminescent silica nanoparticles in Triton X-100 solutions by Asiya R. Mustafina; Julia G. Elistratova; Olga D. Bochkova; Vladimir A. Burilov; Svetlana V. Fedorenko; Alexander I. Konovalov; Svetlana Ye. Soloveva (pp. 644-649).
The aqueous dispersion of Tb(III) doped silica nanoparticles modified by Triton X-100 exemplifies smart colloidal system, which undergo reversible temperature induced phase separation on luminescent and non-luminescent phases.Display Omitted► Silica nanoparticles exhibit thermoresponsive phase behavior in aqueous TX100 solutions. ► The aggregation of TX100 at a silica surface is the reason of such behavior. ► The phase behavior of nanoparticles is modified by the effect of additives.The aggregation and cloud point behavior of Tb(III)-doped silica nanoparticles has been studied in Triton X-100 (TX-100) solutions at various concentration conditions by fluorimetry, dynamic light scattering, electrophoresis and transmission electron microscopy methods. The temperature responsive behavior of nanoparticles is observed at definite concentration of TX-100, where the aggregation of TX-100 at the silica/water interface is evident from the increased size of the silica nanoparticles. The reversible dehydration of TX-100 aggregates at the silica/water interface should be assumed as the main reason of the temperature induced phase separation of silica nanoparticles. The distribution of nanoparticles between aqueous and surfactant rich phases at the phase separation conditions can be modified by the effect of additives.

Keywords: Non-ionic surfactants; Silica nanoparticles; Cloud point behavior; Luminescence

Wettability of the morphologically and compositionally varied surfaces prepared from blends of well ordered comb-like polymer and polystyrene by Eun-Ho Sohn; Byoung Gak Kim; Jae-Seung Chung; Hyo Kang; Jong-Chan Lee (pp. 650-661).
Morphologically and compositionally varied surfaces were prepared from the blends of a well ordered comb-like polymer and polystyrene and their surface properties were systematically studied.Display Omitted► A very low energy surface (≈22mN/m) was created when the blends (CH3-10SE/PS) contained only 20wt.% of CH3-10SE. ► The blend surfaces showed the better film stability than that of pure CH3-10SE and PS. ► The advancing contact angles of water and n-hexadecane were highly increased from 113.5° and 43.2° for CH3-10SE surface to 133.3° and 67.2° for the surface with holes prepared by removing the PS domains on the blend surface, respectively.Phase-separated surfaces of blends of polystyrene (PS) and well ordered comb-like polymer, poly[(oxy(decylsulfonylmethyl)ethylene)] (CH3-10SE), were prepared by spin casting polymer mixtures. Various surface morphologies, such as holes, islands, connected islands and pillars, were prepared by changing the blend compositions. Due to the influence of the CH3-10SE domain with a well ordered molecular conformation, a very low energy surface (≈22mN/m) was created, which is close to the value of the pure polymer (≈20mN/m), even when the blends contained only 20wt.% of the pure polymer. Furthermore, by selective etching the PS domain in the blend surfaces, the advancing contact angles of water and n-hexadecane were highly increased from 113.5° and 43.2° for the pure CH3-10SE surface to 133.3° and 67.2° for the CH3-10SE structural surfaces with holes prepared using the solvent etching method, respectively. The result of the water advancing contact angles measured on the samples immersed in water over 20days showed that the film stability of CH3-10SE could be improved considerably by even adding small amounts of PS.

Keywords: Comb-like polymer; Polystyrene; Blend; Surface morphology; Wettability; Film stability

Fluorescence of commercial Pluronic F127 samples: Temperature-dependent micellization by Christopher C. Perry; Theodore S. Sabir; Wesley J. Livingston; Jamie R. Milligan; Qiao Chen; Victoria Maskiewicz; Danilo S. Boskovic (pp. 662-669).
BHT antioxidant in Pluronic F127 can be used to probe polymer aggregation.Display Omitted► Antioxidant BHT fluorescence sensitive to Pluronic F127 microenvironment. ► BHT fluorescence increases as it partitions into Pluronic F127 micellar phase. ► BHT fluorescence used to measure critical micelle temperature.We present a novel approach of using the butylated hydroxytoluene (BHT) antioxidant found in commercial Pluronic F127 samples as a marker of polymer aggregation. The BHT marker was compared to the pyrene dye and static light scattering methods as a way to measure the critical micelle concentration (CMC) and critical micelle temperature (CMT). The n→π transitions of BHT are sensitive to the microenvironment as demonstrated by plotting the fractional intensities of its excitation (≈280nm) and emission (≈325nm) peaks. BHT is more sensitive to changes in temperature than concentration. The partition coefficient increases ≈40-fold for pyrene compared to ≈2-fold for BHT when the temperature is increased from 25 to 37°C. CMT values determined using the BHT fluorescence decrease with increasing F127 concentration. Our results show that BHT can be used as a reliable marker of changes in the microenvironment of Pluronic F127.

Keywords: Polymeric micelles; Pluronic F127; Critical micelle concentration; Critical micelle temperature

On the flocculation and re-dissolution of trivalent lanthanide metal ions by sodium dodecyl sulfate in aqueous solutions by Rui F.P. Pereira; María J. Tapia; Artur J.M. Valente; Rachel C. Evans; Hugh D. Burrows; Rui A. Carvalho (pp. 670-676).
The addition of SDS, in its unimer form, to trivalent lanthanide ion solutions leads to a flocculation process followed by re-dissolution, as seen by ICP-AES.Display Omitted► Trivalent lanthanide ions form lamellar flocs with SDS. ► These redissolve in excess surfactant to form mixed aggregates. ► At higher concentrations normal micelles form, but the cmc decreases.The interaction between aqueous solutions of trivalent lanthanide ions (M3+: La(III) and Gd(III) and Tb (III)) at fixed (1mM) concentrations and various concentrations of sodium dodecyl sulfate (SDS), ranging from pre- to post-micellar, has been investigated by ICP-AES (La(III) and Gd(III)), luminescence spectra (Gd(III)) and lifetimes (Tb(III)) and139La NMR spectroscopy. It has been found that at concentration ratios, r=[SDS]/[M3+], around the charge neutralization value (ca. 3), dodecyl sulfate (DS) anion interacts with the metal ions to form insoluble aggregates. The metal ion–DS complexes remain flocculated for r values below 5–6 (Gd(III) and La(III), respectively), while at higher r values, re-dissolution takes place. The flocculated aggregates have been characterized by X-ray powder diffraction, and show a lamellar structure.Job plot method indicates that a complex with a 1:3 (M3+:DS) stoichiometry is formed. From ICP-AES analysis, a model based on a three-step mechanism has been developed and association constants calculated. For all systems the interaction between DS and metal ions follows an associative process with K values ranging between K1=10 and K3=104. These data are discussed on the basis of the physical–chemical characteristics of the metal ions. Re-dissolution with increasing surfactant concentration is attributed to formation of mixed lanthanide/sodium dodecyl sulfate aggregates, with the relative lanthanide fraction in these species decreasing with increasing SDS concentration.

Keywords: Surfactants; Lanthanide; Trivalent metal ion; Association constants; Flocculation; Re-dissolution

Crystalline structures and mesomorphic properties of gemini diammonium surfactants with a pendant hydroxyl group by Zengbin Wei; Xilian Wei; Dezhi Sun; Jiuqiang Liu; Xiaojuan Tang (pp. 677-685).
The hydroxyl group of the spacer enhances the hydrogen bonding interaction between neighboring compounds, and therefore the packing of C12–3(OH)–C12 is arranged to form a herringbone-like mode.Display Omitted► The packing arrangement of C n–3(OH)–C n shows a herringbone-like structure as a result of the presence of a pendant hydroxyl group. ► These compounds of C n–3(OH)–C n have relatively low melting points, as compared to those without a hydroxyl substituted at the spacer. ► The melting point and rheological parameters increase, conforming to the length of alkyl chains.A series of homologous crystals of gemini diammonium surfactants (GDAS) containing one hydroxyl substituted methylene spacer are prepared. The crystal structures of these compounds, namely [C nH2 n+1–N+ (CH3)2–CH2CH(OH)CH2–N+(CH3)2–C nH2 n+1], are determined by single-crystal X-ray diffraction techniques, in order to have a better understanding of the structure relation between the solid and the mesophase. The hydroxyl groups enhance the hydrogen bonding interaction between neighboring compounds, and therefore the packing of GDAS in the solid state is arranged to form a herringbone-like mode. To the best of our knowledge, this is the first GDAS crystal with a herringbone-like structure. Their mesomorphic properties are investigated by differential scanning calorimetry, polarizing optical microscopy, X-ray powder diffraction, and rheological measurement. These compounds have relatively low melting points and form thermotropic mesophases over a broad temperature range, as compared to those without a hydroxyl substituted at the spacer. The rheological behavior of the smectic phases clearly reveals that hydrogen bonds exert a significant effect on the high values of moduli and viscosity. Moreover, the melting point and rheological parameters increase, conforming to the length of alkyl chains.

Keywords: Gemini surfactant; Crystal structure; Thermotropic mesophase; Rheological property

One-step synthesis of Ti-MSU and its catalytic performance on phenol hydroxylation by Shaoan Song; Wei Zhao; Lina Wang; Jinglong Chu; Jinkui Qu; Shaohua Li; Li Wang; Tao Qi (pp. 686-690).
One-step synthesis of Ti-MSU and its catalytic performance of phenol hydroxylation.Display Omitted► One-step synthesis of high-quality Ti-MSU. ► The first detailed study on the role of the addition time of a Ti source. ► Optimum synthesized Ti-SMU sample showed good catalytic performance on phenol hydroxylation.In this study, high-quality Ti-MSU was synthesized by a convenient one-step hydrothermal synthesis procedure. This is the first detailed study on the role of addition time of a Ti source. We found that the addition time of the Ti source can effectively influence the structure and morphology of the product by adjusting the balance of hydrolysis–polymerization and nucleation–aggregation in different self-assembly steps. The optimum synthesized Ti-SMU sample showed a good catalytic performance on the phenol hydroxylation.

Keywords: Ti-MSU; Hydrothermal synthesis; Surfactant; Mesoporous silica; Phenol hydroxylation

Comparison of oleyl and elaidyl isomer surfactant–counterion systems in drag reduction, rheological properties and nanostructure by Yunying Qi; Ellina Kesselman; David J. Hart; Yeshayahu Talmon; Anthony Mateo; Jacques L. Zakin (pp. 691-699).
Schematic view of cis- and trans-forms of surfactant hydrocarbon chains.Display Omitted► Presented the first drag reduction, rheological and nanostructure comparisons of unsaturated (cis/trans) cationic surfactant/counterion systems. ►1H NMR results indicate that the hydrocarbon chain of the cis surfactant is more favorable for micelle growth than the trans surfactant. ► The oleyl surfactant drag reducing system had greater resistance to mechanical shear than the elaidyl surfactant. ► Confirmed that viscoelasticity is not required for a surfactant system to be drag reducing. ► High extensional viscosity is a major factor in the drag reduction mechanism.Compared with quaternary ammonium cationic surfactants with saturated alkyl chains, quaternary ammonium cationic surfactants with one double-bond in their alkyl chains, when mixed with appropriate counterions (in certain molar concentration ratios, ξ), can reach much lower effective drag-reduction temperatures, while maintaining the upper drag-reduction temperature limit of the corresponding saturated drag reducing surfactant solutions. No previous study has compared the effects of cis- vs. trans-unsaturated alkyl hydrocarbon tail configurations (oleyl vs. elaidyl) trimethyl ammonium chloride cationic surfactants at different counterion/surfactant concentration ratios on micellar nanostructures,1H NMR spectra and on rheological and drag-reduction behavior of their solutions. Since neither pure oleyl (cis-) nor elaidyl (trans-) trimethyl ammonium chloride surfactants are commercially available, they were synthesized and their 5mM solutions with NaSal counterion at concentrations of 5mM, 7.5mM and 12.5mM were studied.

Keywords: Drag reduction; Rheology; Nanostructure; NMR; Unsaturated quaternary ammonium cationic surfactant (oleyl vs. elaidyl)

Mixed micelles of amphiphilic drug promethazine hydrochloride and surfactants (conventional and gemini) at 293.15K to 308.15K: Composition, interaction and stability of the aggregates by Kabir-ud-Din; Malik Abdul Rub; Andleeb Z. Naqvi (pp. 700-708).
Effect of temperature on the critical micelle concentration (cmc) of pure drug (PMT) and surfactants (conventional and gemini).Display Omitted► Surfactants are generally used as drug carriers in pharmaceuticals. ► Presence of surfactants may alter the micellization tendency of a drug which may affect the activity of the drug. ► Therefore, it is important to have knowledge of the effect of surfactants on micelle formation of drugs and the related energetics. ► Keeping this in mind, effect of cationic surfactants on the micellization of promethazine hydrochloride is seen.Micellization of an amphiphilic phenothiazine drug promethazine hydrochloride (PMT) in presence of conventional (CTAB and TTAB) as well as gemini (16- s-16 and 14- s-14, s=4–6) cationic surfactants has been studied conductometrically at different temperatures. Critical micelle concentration values (cmc and cmcid) indicate mixed micelle formation among the two components. Micellar mole fractions of surfactants ( X1,X1M andX1id) show greater contribution of surfactants. Interaction parameter, β, suggests attractive interactions in the mixed systems. The thermodynamic parameters suggest dehydration of hydrophobic part of the drug at higher temperatures.

Keywords: Phenothiazine drug; Promethazine hydrochloride (PMT); Critical micelle concentration (cmc); Conductivity; Conventional surfactant; Gemini surfactant

Evaluating alternative electrostatic potential models for polyacrylamide-co-acrylate in aqueous solution by Byung Joon Lee; Mark A. Schlautman (pp. 709-717).
The impermeable sphere and Donnan sphere electrostatic potential models (top) do not provide physically realistic representations for linear polyelectrolyte morphology and metamorphosis in aqueous solution (bottom). The cylindrical electrostatic potential model, however, does.Display Omitted► Linear polyelectrolytes change viscosity and morphology with solution chemistry. ► Spherical electrostatic models do not accurately represent linear polyelectrolytes. ► Size parameters in the spherical electrostatic models are not physically realistic. ► Cylindrical electrostatic models are more representative of linear polyelectrolytes. ► Cylindrical electrostatic models are more robust than spherical models.The capabilities of three simplified analytical equations to accurately model electrostatic interactions during proton binding and release by linear anionic polyelectrolytes in aqueous solution were evaluated. The impermeable sphere (IS), Donnan (DN), and cylindrical (CY) electrostatic models were fit to experimental acid–base titration curves of linear polyacrylamide-co-acrylate having ionizable site densities ranging from ca. 10–35%. The titrations were conducted in 0.003–0.12M NaCl solutions and the sum of squared errors from modeled and experimental data was used as a comparative index of each model’s capability. In addition, the relative size of each polyelectrolyte was estimated from its measured specific viscosity and then compared against the values obtained from the fitting procedure for the size parameter that each model contained. Although the IS and DN electrostatic models could be used to obtain reasonably good fits to each titration curve, the size parameter values obtained by each model were not reflective of the actual polyelectrolyte sizes, indicating that the models had limited physical meaning and that the size parameter was essentially just an additional fitting parameter in each model. In contrast, the CY model was not only more effective in its ability to fit the titration data but also provided a better physical representation of the polyelectrolyte size. Therefore, for polyelectrolytes that remain essentially linear or are only loosely coiled such that counter ions are free to travel throughout the polymer structure, we conclude that the CY model and its morphological representation of a cylindrical polyelectrolyte are more valid and realistic than the IS and DN models and their representation of polyelectrolytes as spheres.

Keywords: Polyelectrolytes; Electrostatic model; Proton binding; Acid–base titration

Nanostructuring of CyPLOS ( Cyclic Phosphate-Linked OligoSaccharides), novel saccharide-based synthetic ion transporters by Gaetano Mangiapia; Cinzia Coppola; Giuseppe Vitiello; Gerardino D’Errico; Lorenzo De Napoli; Aurel Radulescu; Daniela Montesarchio; Luigi Paduano (pp. 718-724).
Jellyfish-shaped ionophores CyPLOS self aggregate in pseudo-physiological conditions forming large nanostructures whose morphology depends on the nature of the grafted tentacles.Display Omitted► In the present study we have characterized the self assembling of amphiphilic ionophores in pseudo-physiological condition. ► Amphiphilic ionophores can lodge in biological membrane to act as ion channels or carrier. ► The amphiphilic ionophores assemble as vesicles with disordered bilayer in pseudophysiological condition. ► Vesicles structure depends on the nature of the tails attached to cyclic oligosaccharides.Ionophores are an important class of synthetic molecules which mimic natural ion channels or carriers. Here we report the aggregation behavior in pseudo-physiological environment of three Cyclic Phosphate-Linked Oligosaccharides (CyPLOS) derivatives, synthetic ion transporters based on cyclic, phosphate-linked disaccharide skeleton differing for the nature of the tails (tetraethylene–TEG glycol and/or n-undecyl chains) attached to the C-2 and C-3 of the constitutive monosaccharides. Their aggregation behavior has been studied by a combined use of dynamic light scattering (DLS), electron paramagnetic resonance spectroscopy (EPR) and Small Angle Neutron Scattering (SANS). DLS measurements were performed to reveal the formation and size distribution of the CyPLOS aggregates. EPR measurements, by using 5-doxyl stearic acid (5-DSA) as spin-probe, showed that the aggregates are mainly due to the formation of double layers and allowed to analyze the local fluidity. Finally, SANS measurements allowed estimating the layer thickness of the double layers. Our results indicate that the three CyPLOS analogs show self-aggregation properties that depend on the different nature of the inserted tails.

Keywords: Ionophores; Nanostructures; Dynamic light scattering (DLS); Electron paramagnetic resonance spectroscopy (EPR); Small Angle Neutron Scattering (SANS)

The effect of the head-group spacer length of 12- s-12 gemini surfactants in the host–guest association with β-cyclodextrin by R.A. Carvalho; H.A. Correia; A.J.M. Valente; O. Söderman; M. Nilsson (pp. 725-732).
The schematic figure represents the differences in the association mechanism of β-CD and geminis with different spacer lengths.Display Omitted►1H NMR study of interactions between gemini surfactants and β-cyclodextrin. Each tail of the dimeric surfactant threads one molecule of cyclodextrin. ► The surfactant–cyclodextrin complexes are very stable (ca. −45kJ/mol). ► The binding of the second cyclodextrin is non-cooperative. ► The spacer with 10 methylene groups can thread the cyclodextrin.NMR spectroscopy has been used to study and characterize the interactions in solution between β-CD and alkyl-α,ω-bis(dodecyldimethyl ammonium bromide) gemini surfactants with the following head-group spacer lengths: 2, 4, 6, 8, and 10. The application of the method of continuous variation gives as a result that 1:1 and 2:1 (β-cyclodextrin-gemini) complexes are formed; the association stoichiometry is dependent on the spacer chain length, varying from 1.5 (for s=2) to 1.8 (for s=10). Assuming a two-step mechanism, the binding constants have been computed. In general, the overall binding constant slightly increases with an increase of the number of methylene groups in the spacer. The1H NMR spectra of the N-(CH3)2 groups in β-cyclodextrin/gemini mixed solutions are split into two peaks for 12-10-12, suggesting that the gemini spacer can thread the β-cyclodextrin so that the latter is positioned between the gemini head-groups. Inspection of the ROESY spectra allowed the establishment of several spatial proximities between the protons from the β-CD and the gemini and for a spacer length of 10, the data indeed indicate that complexes are formed with the CD molecule positioned between the two charged head groups with the spacer passing through the CD molecule.

Keywords: Gemini surfactants; Cyclodextrins; 1; H NMR spectroscopy; Supramolecular structures; Binding constants

Adsorption of DNA to octadecylamine monolayers at the air–water interface by Tânia Lopes-Costa; Francisco Gámez; Santiago Lago; José M. Pedrosa (pp. 733-738).
DNA interaction with octadecylamine monolayers on water is clearly visualized by Brewster Angle Microscopy (BAM). Interesting phase transitions and quantitative BAM reflectivity measurements are also shown in this work.Display Omitted► Octadecylamine (ODA) monolayers on water are a suitable matrix for polynucleotide immobilization. ► The increase of DNA concentration leads to an expansion and a change in the profile of the ODA isotherm. ► New reversible phase transitions appear in the isotherms upon addition of sufficient amount of DNA. ► BAM reflectivity allows the quantification of monolayer compressibility and adsorption kinetics.In this work, surface properties of octadecylamine (ODA) monolayers in the presence of different concentrations of calf thymus DNA in the aqueous subphase covering a range of 2–8μM have been investigated. The increase of DNA concentration is accompanied by a marked increment in the expansion of the corresponding isotherms. In addition, there is a change in the profile of the isotherms ranging from an abrupt liquid–solid transition for the lipid monolayer on pure water to a slow condensation of the monolayer in a liquid state when DNA is added to the subphase, demonstrating the effective adsorption of the polynucleotide to the long chain amine monolayer. Additional phase transitions appear in the isotherms upon addition of sufficient amount of DNA, revealing the existence of specific processes such as folding or squeezing out of the DNA. This system is, however, highly reversible during compression-expansion cycles due to the strong interaction between the two components. These results are also supported by Brewster Angle Microscopy (BAM) images showing significant changes in the morphology of the film. Integral reflectivity of the BAM microscope has been used to study both isotherms themselves and the kinetic process of DNA inclusion into the lipid-like ODA monolayer. This parameter has been proven to be very effective for quantification of the monolayer processes showing high consistency with the compressibility and kinetics results.

Keywords: Polynucleotide-amine mixed films; Brewster Angle Microscopy; Langmuir trough; BAM reflectivity

Quantification of unadsorbed protein and surfactant emulsifiers in oil-in-water emulsions by Claire Berton; Claude Genot; Marie-Hélène Ropers (pp. 739-748).
The unadsorbed emulsifiers, present in the aqueous phase of O/W emulsions are quantified following a methodology adapted to the class of emulsifiers (surfactants or proteins).Display Omitted► The aqueous phases separated from droplets of emulsions by centrifugation and filtration. ► Direct transesterification of surfactant fatty acids in the aqueous phases of emulsions. ► Method validated for Tween 20, Tween 80, Citrem, Span 20 and monolauroyl glycerol. ► Method valid for surfactants mixed with protein. ► UV-spectrophotometry not valid for quantification in oxidative conditions.Unadsorbed emulsifiers affect the physical and chemical behaviour of oil-in-water (O/W) emulsions. A simple methodology to quantify unadsorbed emulsifiers in the aqueous phase of O/W emulsions has been developed. Emulsions were centrifuged and filtered to separate the aqueous phase from the oil droplets and the concentration of unadsorbed emulsifiers in the aqueous phase determined. The quantification of unadsorbed surfactants based on the direct transesterification of their fatty acids was validated for Tween 20, Tween 80, citric acid ester (Citrem), Span 20 and monolauroyl glycerol. To determine unadsorbed proteins, results obtained with Folin–Ciocalteu reagent or UV-spectrophotometry were compared on emulsions stabilized by β-lactoglobulin (BLG), β-casein (BCN) or bovine serum albumin (BSA). The first method gave more accurate results especially during aging of emulsions in oxidative conditions. The whole methodology was applied to emulsions stabilized with single or mixed emulsifiers. This approach enables optimization of emulsion formulations and could be useful to follow changes in the levels of unadsorbed emulsifiers during physical or chemical aging processes.

Keywords: Protein; Surfactant; Unadsorbed emulsifiers; Interface; Oil-in-water emulsion

Copolymers sensitive to temperature and pH in water and in water+oil mixtures: A DSC, ITC and volumetric study by Rosario De Lisi; Gabriele Giammona; Giuseppe Lazzara; Stefana Milioto (pp. 749-757).
Tuning oil incorporation into polymeric micelles by changing temperature and pH.Display Omitted► Temperature and pH responsive Tetronic micelles. ► Controlling the oil solubilization in Tetronic micelles. ► Thermodynamics of micellization of Tetronic in water. ► Thermodynamics of oil solubilization in Tetronic micelles.Block copolymer micelles are receiving an increasing interest because of the variety of structures and the possibilities to tune them by changing external and internal parameters achieving the desired properties for a specific purpose. We have investigated the acid/base behavior, self-assembling and solubilization ability towards polar oils of star-like copolymers named Tetronics. They are composed of branched four-arms each one consisting of two blocks made of EO and PO units linked to the diethylenediamine group, which confers pH response ability. The copolymers T1107 and T90R4 were studied with a sequential and reverse architecture. The thermodynamics of the acid/base equilibrium was studied by ITC. The aggregation of T1107 in water was analyzed as functions of pH, composition and temperature. The enhanced oil solubilization in the aqueous T1107 aggregates was widely investigated highlighting the role of the oil structure, composition, temperature and pH. As a general result, the oil induces the copolymer aggregation and the solubilization power of micelles is tunable by changing the pH. Efforts have been devoted to model the calorimetric data in order to achieve the thermodynamic properties of the involved process. Finally, we showed that the Tetronic micelles are more promising than the conventional surfactants micelles because of the larger solubilization power and flexibility of the macromolecular system.

Keywords: Tetronic; Polar oils; Solubilization; ITC; DSC; Apparent molar volume

Fabrication of robust micro-patterned polymeric films via static breath-figure process and vulcanization by Lei Li; Yawen Zhong; Jianliang Gong; Jian Li; Jin Huang; Zhi Ma (pp. 758-764).
Stable and flexible honeycomb structured SIS film after 24h vulcanization.Display Omitted► Preparation of micro-patterned polymeric films via static breath figure process with triblock copolymers, polystyrene- b-polyisoprene- b-polystyrene (SIS) and hydroxyl-containing polystyrene- b-polybutadiene- b-polystyrene (SBS-OH). ► Sequent vulcanization to improve chemical and thermal stability of the micro-structured polymeric films. ► Replication of fixed microporous structures to fabricate textured positive PDMS stamps.Here, we present the preparation of thermally stable and solvent resistant micro-patterned polymeric films via static breath-figure process and sequent vulcanization, with a commercially available triblock polymer, polystyrene- b-polyisoprene- b-polystyrene (SIS). The vulcanized honeycomb structured SIS films became self-supported and resistant to a wide range of organic solvents and thermally stable up to 350°C for 2h, an increase of more than 300K as compared to the uncross-linked films. This superior robustness could be attributed to the high degree of polyisoprene cross-linking. The versatility of the methodology was demonstrated by applying to another commercially available triblock polymer, polystyrene- b-polybutadiene- b-polystyrene (SBS). Particularly, hydroxy groups were introduced into SBS by hydroboration. The functionalized two-dimensional micro-patterns feasible for site-directed grafting were created by the hydroxyl-containing polymers. In addition, the fixed microporous structures could be replicated to fabricate textured positive PDMS stamps. This simple technique offers new prospects in the field of micro-patterns, soft lithography and templates.

Keywords: Polymer films; Breath figure; Cross-linking

Ettringite surface chemistry: Interplay of electrostatic and ion specificity by Marta Medala; Christophe Labbez; Isabelle Pochard; André Nonat (pp. 765-770).
A good fit is obtained adding a specific potential to the ettringite–sulfate interaction, which highlights the existence of a specific interaction.Display Omitted► Consistent picture of the ettringite–water interface over pH and bulk conditions. ► Charge reversal of ettringite immersed in sulfate salt solutions. ► Electrostatics, through ion–ion correlations, must be considered. ► Sulfate short-range adsorption potential must be considered too.This paper presents a detailed experimental study combined with Monte Carlo (MC) simulations within the primitive model of the physical chemistry at the ettringite–water interface over a wide range of pH and bulk conditions for which ettringite exists thanks to its solubility in aqueous solutions. Ettringite, which is an important phase in hydrated cement-based systems, bears a permanent and positive structural charge. In contrast with previous studies, electrokinetic measurements together with the careful chemical analysis of the equilibrium solutions of the dispersions have brought strong support to designate sulfate as being the ion determining the potential. Simulations showed that electrostatics, through ion–ion correlations, are not strong enough to explain the charge reversal of ettringite immersed in sulfate salt solutions. However, an excellent agreement between simulated and experimental data was obtained including a short-range nonelectrostatic adsorption potential for the sulfate ion. This result strongly suggests the existence of a chemical specificity of sulfate ions for an ettringite surface.

Keywords: Ettringite; Electrophoresis; Monte Carlo simulations; Sulfate; Adsorption potential

Synthesis of thermosensitive polymer/mesoporous silica composite and its temperature dependence of anion exchange property by Kenji Murakami; Xue Yu; Shinichi Watanabe; Takahiro Kato; Yukihiko Inoue; Katsuyasu Sugawara (pp. 771-776).
The adsorption–desorption behavior in the mesoporous silica coated with PNIPAM depended on the temperature of aqueous solution.Display Omitted► PNIPAM was immobilized on the outer surface of mesoporous silica. ► Amount of anion exchange depended on the temperature of aqueous solution. ► Adsorption and desorption was repeated with changing pH of the solution at 25°C. ► Molecule was not adsorbed and desorbed independent of pH of the solution at 40°C.An anion exchanger consisting of amino-functionalized MCM-41 type mesoporous silica coated with temperature-responsive polymer, poly( N-isopropylacrylamide) (PNIPAM), was synthesized in this study. The structure of this composite was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and elemental analysis. The XRD pattern showed that the synthesized composite had the ordered hexagonal structure and the interplanar spacing, d100, was around 40Å. The amount of surface-grafted thermosensitive polymer was estimated to be about 0.8wt.% by elemental analysis. The adsorption–desorption behavior of methyl orange in this synthesized material depended on the temperature of aqueous solution: at 25°C, the reversible adsorption–desorption of methyl orange was repeated with changing pH of the solution; at 40°C, the methyl orange was not adsorbed and desorbed independent of pH of the solution.

Keywords: Mesoporous silica; Temperature-responsive adsorbent; Anion exchange; Poly(; N; -isopropylacrylamide)

Influence of Ce addition on the catalytic behavior of alumina-supported Cu–Co catalysts in NO reduction with CO by I. Spassova; N. Velichkova; D. Nihtianova; M. Khristova (pp. 777-784).
The ceria-promoted alumina-supported copper and cobalt catalysts with metal loadings up to 4% total metal are effective in the reduction of NO with CO. The addition of cerium in the binary systems affects the activity at temperatures over 130°C, whereas the activity of the ternary-supported catalysts is enhanced even at room temperature.Display Omitted► Ce-promoted Cu and Co catalysts are active in NO reduction with CO up to 300°C. ► Ce affects on binary catalysts activity over 130°C. ► Ce affects on ternary catalysts activity at room temperature. ► Ce influences on the dispersion of the copper and cobalt active phases. ► Ce promotes the formation of catalytic active sites for NO reduction with CO.The effect of Ce addition to alumina-supported copper, cobalt, and copper–cobalt oxides with low loadings on the catalysts efficiency in NO reduction with CO was studied. The attention was focused on varying the impregnation procedure in the ternary-supported catalysts in order to determine the best catalyst as well as the reasons for the enhanced catalytic activity. Ternary Co–Cu–Ce and binary Co–Ce, Cu–Ce, and Cu–Co-supported alumina were prepared and characterized by ICP, XRD, TEM, adsorption studies, XPS, H2-TPR, and catalytic investigations. The high activity of the ternary and the binary catalysts was determined by the favorable influence of the added cerium on the dispersion of the copper and cobalt active phases. The presence of ceria contributes to the formation of appropriate active phases, resulting in catalytic sites on the surface of the samples that promote the reduction of NO with CO.

Keywords: NO reduction with CO; Ceria; Copper–cobalt catalysts; Alumina-supported catalysts

A zirconium based nanoparticle for significantly enhanced adsorption of arsenate: Synthesis, characterization and performance by Yue Ma; Yu-Ming Zheng; J. Paul Chen (pp. 785-792).
An enhanced nanoparticle sorbent for effective adsorption of arsenate from aqueous solution was successfully developed, which had a maximum adsorption capacity of 256.4mg-As/g at the optimal pH.Display Omitted► A zirconium based nanoparticle sorbent, Zr2(OH)6SO4·3H2O, was successfully developed. ► Based on Langmuir isotherm, the maximum adsorption capacity was 243mg-As/g-sorbent at pH 3. ► Fluoride or nitrate dose not significantly influence the adsorption of As(V) on the sorbent. ► Humic acid, phosphate and silicate severely hinders the adsorption of As(V) onto the sorbent. ► Hydroxyl and sulfur-containing functional groups play important roles in the adsorption.In this study, a zirconium nanoparticle sorbent for significantly enhanced adsorption of arsenate (As(V)) was successfully synthesized. The characterization of the zirconium nanoparticle sorbent and its adsorption behavior for arsenate were investigated. The HRTEM micrographs showed that the sorbent was nanoscale with particle sizes ranging from 60 to 90nm. The thermal gravimetric and elemental analyses indicated that the sorbent had a molecular formula of Zr2(OH)6SO4·3H2O. The X-ray diffraction study revealed that the sorbent was amorphous. The potentiometric titration study demonstrated the surface charge density of the sorbent decreased with an increase in solution pH, and the pH of zero point charge of the sorbent was around 2.85. The kinetics study showed that most of the uptake took place in the first 6h, and the adsorption equilibrium was obtained within 12h. The optimal pH for As(V) adsorption was between 2.5 and 3.5. The Langmuir equation well described the adsorption isotherm; the maximum adsorption capacity of 256.4mg As/g was found at the optimal pH, better than most of sorbents available in the market. The presence of fluoride or nitrate did not obviously affect the adsorption of As(V) onto the sorbent; however, the existence of humic acid, phosphate or silicate in aqueous solution significantly reduced the uptake of As(V). The humic acid did not cause the reduction of the As(V). The FTIR and XPS spectroscopic analyses revealed that surface hydroxyl and sulfur-containing groups played important roles in the adsorption.

Keywords: Adsorption; Arsenate; Nanoparticle; Zirconium

Synthesis and anion-exchange reactions of a new anionic clay, α-magnesium hydroxide by C. Nethravathi; Jacqueline T. Rajamathi; Preeta George; Michael Rajamathi (pp. 793-797).
α-Magnesium hydroxide, which is structurally similar to LDHs, could be obtained through acetate hyrolysis in an organic solvent.Display Omitted► α-Hydroxides, which are structurally similar to LDHs, are known only in the case of Ni2+ and Co2+. ► For the first time α-hydroxide of Mg2+ is reported in this work. ► Though it is unstable in water we could demonstrate its anionic clay-like behavior through anion-exchange reactions in alcoholic solutions.A new anionic clay, α-magnesium hydroxide, was synthesized by hydrolysis of magnesium acetate in propylene glycol. The structure of this α-hydroxide is similar to that of hydrotalcites. It consists of positively charged magnesium hydroxide layers arising out of partial protonation of the hydroxyl groups of the [Mg(OH)2] layers and loosely held anions in the interlayer region. As expected it ages readily in water to give β-magnesium hydroxide, brucite. While anion-exchange reactions of α-magnesium hydroxide could not be carried out in aqueous medium a number of anion-exchange reactions could be carried out successfully in ethanol medium.

Keywords: α-Magnesium hydroxide; Hydrolysis; Anion exchange; Anionic clay

Fe–Al layered double hydroxides in bromate reduction: Synthesis and reactivity by Ramesh Chitrakar; Yoji Makita; Akinari Sonoda; Takahiro Hirotsu (pp. 798-803).
BrO3- (100μmol/dm3) was completely removed on Fe–Al LDH via reduction process releasing Br, and LDH structure was collapsed due to oxidation of Fe2+ to Fe3+ releasing interlayer Cl.Display Omitted► Rare use of Fe–Al LDH as reported first time for bromate removal. ► Initial bromate concentration of 100 μmol/dm3 can be decreased to below 0.078μmol/dm3 (10μg-BrO3-/dm3) within 1–2h. ► Presence of chloride, nitrate, sulfate, phosphate and carbonate did not affect bromate removal. ► Reduction of bromate to bromide in solution and oxidation of Fe2+ to Fe3+ in solid were occurring simultaneously, with collapse of LDH structure.This study presents a rare use of layered double hydroxides of Fe(II) and Al(III) (Fe–Al LDH), as reported for the first time for bromate removal from aqueous solutions. The Fe–Al LDH samples were prepared with Fe/Al molar ratios of 1–4 using a co-precipitation method at pH 7, with subsequent hydrothermal treatment at 120°C. The Fe–Al LDH (molar ratio of Fe/Al=1, 2) with a layered structure exhibited nearly complete removal of bromate from initial concentration of 100μmol/dm3 at a wide pH range of 4.0–10.5 over a 2h reaction period; the residual bromate concentration in the solution was lower than the detection limit of 0.07μmol/dm3 (9μg-BrO3-/dm3). During the reaction period, bromide was released into the solution via a reduction process. Reactivity of Fe–Al LDH with a Fe/Al molar ratio of 2 did not decrease the bromate reduction efficiency during 30days.

Keywords: Layered double hydroxides; Removal; Bromate; Reduction

Synthesis of Ru0.58In0.42O ynH2O nanoparticles dispersed onto poly(sodium-4-styrene sulfonate)-functionalized multi-walled carbon nanotubes and their application for electrochemical capacitors by Changzhou Yuan; Linrui Hou; Long Yang; Diankai Li; Jie Tan; Laifa Shen; Fang Zhang; Xiaogang Zhang (pp. 804-809).
Ru–In binary nanoparticles highly dispersed onto the poly(sodium-4-styrene sulfonate)-functionalized multi-walled carbon nanotubes were synthesized by mild hydrothermal method and delivered good electrochemical capacitance at high rates.Display Omitted► Carbon nanotubes were functionalized by poly(sodium-4-styrene sulfonate) with negative charge. ► Ru0.58In0.42Oy·nH2O nanoparticles were dispersed on functionalized carbon nanotubes. ► High dispersion resulted in great utilization of nanosized Ru0.58In0.42Oy·nH2O. ► The nanocomposites delivered larger energy density and higher power density.In this work, poly(sodium-4-styrene sulfonate) (PSS)-functionalized multi-walled carbon nanotubes (FMWCNTs) were first synthesized via a polymer-assisted technique. Then, Ru0.58In0.42O ynH2O nanoparticles (NPs) were mono-dispersed onto the FMWCNTs surfaces under mild hydrothermal condition. Here, PSS with negative charge serves as a bifunctional molecule both for solubilizing and dispersing MWCNTs into aqueous solution and for tethering Ru3+ and In3+ to facilitate the good dispersion of Ru1− xIn xO ynH2O NPs onto their surfaces. The good dispersion of Ru0.58In0.42O ynH2O NPs onto FMWCNTs makes OH ions and electrons easily contact these NPs with abundant electroactive sites, which results in a large specific capacitance (SC) of 319Fg−1 for the naocomposites. Moreover, a symmetric electrochemical capacitor (EC) is constructed by using the nanocomposites as electrodes and delivers large specific energy density of 18.1Whkg−1, desirable power property of 1302Wkg−1, high electrochemical reversibility and good SC retention of 84.7%.

Keywords: Functionalized multi-walled carbon nanotubes; Ru; 0.58; In; 0.42; O; y; ⋅; n; H; 2; O nanoparticles; Poly(sodium-4-styrene sulfonate); Monodispersion; Electrochemical capacitance

Superhydrophobic surfaces using selected zinc oxide microrod growth on ink-jetted patterns by Myo Tay Zar Myint; Rungrot Kitsomboonloha; Sunandan Baruah; Joydeep Dutta (pp. 810-815).
Inspired by the lotus leaf structure, binary topography was created using zinc oxide (ZnO) microrods. These were patterned through ink-jetting of ZnO seeds on a substrate followed by the selective hydrothermal growth of the microrods on the seeded bumps. Microbumps of 150μm diameter separated from each other by 50μm, yielded a water contact angle of 153°.Display Omitted► Mimicking the lotus leaf structure using naturally hydrophilic material. ► Artificial superhydrophobic surfaces decorated with zinc oxide (ZnO) microrods on ink-jetted micropatterned arrays. ► Clean and green technology for large area applications. ► Nature to engineering through appropriate application of science.The synthesis and properties of superhydrophobic surfaces based on binary surface topography made of zinc oxide (ZnO) microrod-decorated micropatterns are reported. ZnO is intrinsically hydrophilic but can be utilized to create hydrophobic surfaces by creating artificial roughness via microstructuring. Micron scale patterns consisting of nanocrystalline ZnO seed particles were applied to glass substrates with a modified ink-jet printer. Microrods were then grown on the patterns by a hydrothermal process without any further chemical modification. Water contact angle (WCA)1Water contact angle (WCA).1 up to 153° was achieved. Different micro array patterned surfaces with varying response of static contact angle or sessile droplet analysis are reported.

Keywords: Superhydrophobic; ZnO microrod; Ink-jet printing; Binary structure; Contact angle

Capillary-pressure driven adhesion of rigid-planar surfaces by Thomas Ward (pp. 816-824).
Top view of a liquid bridge initial sandwiched between a stationary wall and a load generating a force oriented into the page. After an elapsed time the liquid either continues to spread generating adhesion (1) or de-wets (2).Display Omitted► Capillary-pressure driven adhesion of a load is studied using viscous fluids. ► Conditions for adhesion depend on surface tension, contact angle and the magnitude of the external load. ► Adhesion occurs at an unstable critical point. ► De-wetting leads to a fingering instability.A thin film of viscous-Newtonian fluid sandwiched between parallel-plane walls, is examined both experimentally and theoretically for gap spacings initially much smaller than the capillary length to determine the conditions for adhesion. The problem is parameterized by the variables F, which is the ratio of an external load generated by one of the parallel-plane surfaces, to the product of surface tension and a characteristic length scale, and the static contact angle α. An analytical solution for the change in gap height as a function of elapsed time is derived in the limit of small Reynolds and zero capillary numbers. The load is suspended for a long but finite elapsed time as the gap spacing approaches a critical value, and for gap spacing values less than the critical one the load is suspended indefinitely. Experiments are performed with typical elapsed times of O(100–1000s) using fluids with viscosity, O(1000 cSt), but different surface tension and contact angle for gap spacings O(10–100μm) with loads of either 2.7N or 4.9N. There is good agreement between the theory and experiments.

Keywords: Capillary driven adhesion; Capillary pressure; Capillary instability; Fingering instability

Slip-stick wetting and large contact angle hysteresis on wrinkled surfaces by Colton Bukowsky; Jessica M. Torres; Bryan D. Vogt (pp. 825-831).
Advancing drop proceeds by slip-stick across wrinkle ridges. Receding contact angle decreases when below a critical drop size.Display Omitted► Slip-stick wetting observed for advancing drop perpendicular to primary wrinkle axis. ► Distance of slip is 1/2 of the wrinkle wavelength. ► Precipitous decrease in the contact angle for the receding drop with >100° hysteresis observed for largest amplitude wrinkled surface examined.Wetting on a corrugated surface that is formed via wrinkling of a hard skin layer formed by UV oxidation (UVO) of a poly(dimethylsiloxane) (PDMS) slab is studied using advancing and receding water contact angle measurements. The amplitude of the wrinkled pattern can be tuned through the pre-strain of the PDMS prior to surface oxidation. These valleys and peaks in the surface topography lead to anisotropic wetting by water droplets. As the droplet advances, the fluid is free to move along the direction parallel to the wrinkles, but the droplet moving orthogonal to the wrinkles encounters energy barriers due to the topography and slip-stick behavior is observed. As the wrinkle amplitude increases, anisotropy in the sessile droplet increases between parallel and perpendicular directions. For the drops receding perpendicular to the wrinkles formed at high strains, the contact angle tends to decrease steadily towards zero as the drop volume decreases, which can result in apparent hysteresis in the contact angle of over 100°. The wrinkled surfaces can exhibit high sessile and advancing contact angles (>115°), but the receding angle in these cases is generally vanishing as the drop is removed. This effect results in micrometer sized drops remaining in the grooves for these highly wrinkled surfaces, while the flat analogous UVO-treated PDMS shows complete removal of all macroscopic water drops under similar conditions. These wetting characteristics should be considered if these wrinkled surfaces are to be utilized in or as microfluidic devices.

Keywords: Wetting; Wrinkling; Contact angle hysteresis; Micropatterned surfaces; Sinusoidal topography

Sliding variability of droplets on a hydrophobic incline due to surface entrained air bubbles by William Yeong Liang Ling; Tuck Wah Ng; Adrian Neild; Quanshui Zheng (pp. 832-842).
Bubbles on PTFE surface shows enhanced droplet sliding behavior down an incline in which two possible mechanisms are discussed here.Display Omitted► Air bubbles on PTFE surface affect droplet sliding on an incline. ► Two possible mechanisms are advanced to explain behavior. ► The first is due to air bubbles creating added solid-liquid-vapour phase interfaces. ► This mechanism alone cannot fully account for the enhanced sliding behavior. ► The second is due to disruptions of back contact line when droplet elongates.The ability of a liquid droplet to move on an incline has important ramifications in discrete volume fluidic devices. By taking advantage of the spontaneous and copious formation of visible air bubbles within water droplets on a polytetrafluoroethylene (PTFE) surface, we uncovered a direct correlation between their presence and the ability of droplets to slide down an incline. We forward two possible mechanisms to account for this behavior. The first is attributed to the air bubbles creating regions where additional solid–liquid–vapor phase interfaces are present; wherein due to the buoyancy force acting upwards, the orientation of the contact angles of each bubble (which should also be in hysteresis but in the opposite direction of the hysteresis at the droplet rim contact lines) dictate that the net force of the bubbles in the droplet act down an incline. We show here that this mechanism cannot fully account for the bubble enhanced sliding behavior. The second mechanism is based on the occurrence of the droplet front advancing first, causing the droplet to elongate and thus allowing the receding contact line to partially sweep inwards over the bubbles. This causes a series of point-wise disruptions on the contact line that permits the droplet to slide down more readily. The relatively short time of ∼180s during which these micron sized bubbles decrease in size indicates a possibility of this mechanism contributing to a transient means to reduce the retention force of droplets that reside on hydrophobic surfaces.

Keywords: Microfluidics; Sliding; Bubbles; Droplet

Structure and reactivity of the calcite–water interface by Frank Heberling; Thomas P. Trainor; Johannes Lützenkirchen; Peter Eng; Melissa A. Denecke; Dirk Bosbach (pp. 843-857).
A basic stern surface complexation model for calcite is developed to relate measured calcite zetapotentials to the molecular structure of the calcite–water interface observed by in situ surface diffraction measurements.Display Omitted► Two layers of water molecules, 2.35±0.05Å and 3.24±0.06Å above the calcite(104)-face, are identified by X-ray surface diffraction at all solution conditions investigated. ► X-ray surface diffraction indicates that Ca2+ andCO32- do not adsorb as inner-sphere complexes on terrace planes at the calcite(104)-face. ► Negative calcite zetapotential measured between pH 5.5 and 11 in Ca2+ free solutions; Ca2+ andCO32- identified as potential determining ions. ► A new basic stern surface complexation model for calcite is presented, using consistent values for Helmholtz capacitance and Stern layer thickness.The zetapotential of calcite in contact with aqueous solutions of varying composition is determined for pre-equilibrated suspensions by means of electrophoretic measurements and for non-equilibrium solutions by means of streaming potential measurements. Carbonate and calcium are identified as charge determining ions. Studies of the equilibrium solutions show a shift of isoelectric point with changing CO2 partial pressure. Changes in pH have only a weak effect in non-equilibrium solutions. The surface structure of (104)-faces of single crystal calcite in contact to solutions corresponding to those of the zetapotential investigations is determined from surface diffraction measurements. The results reveal no direct indication of calcium or carbonate inner-sphere surface species. The surface ions are found to relax only slightly from their bulk positions; the most significant relaxation is a ∼4° tilt of the surface carbonate ions towards the surface. Two ordered layers of water molecules are identified, the first at 2.35±0.05Å above surface calcium ions and the second layer at 3.24±0.06Å above the surface associated with surface carbonate ions. A Basic-Stern surface complexation model is developed to model observed zetapotentials, while only considering outer-sphere complexes of ions other than protons and hydroxide. The Basic-Stern SCM successfully reproduces the zetapotential data and gives reasonable values for the inner Helmholtz capacitance, which are in line with the Stern layer thickness estimated from surface diffraction results.

Keywords: Calcite; Zetapotential; Surface diffraction; Crystal truncation rod; Surface complexation model

Preparation and characterization of ultrathin dual-layer ionic liquid lubrication film assembled on silica surfaces by Jibin Pu; Liping Wang; Yufei Mo; Qunji Xue (pp. 858-865).
Ultrathin dual-layer ionic liquid lubrication film, which contained both bonded and mobile phases in ionic liquids layer was assembled on silica surface.Display Omitted► Dual-layer ultrathin ionic liquid lubrication film which contained both bonded and mobile phases was formed on a silicon substrate by a two-step self-assembly process. ► Both anchor layer (self-assembled monolayer) and bonded ionic liquid phase acts very important effects in enhancing load-carrying capacity of the ionic liquid ultrathin lubrication film. ► The synergic effect between flowable mobile phase and steady bonded phase plays a significant role in improving tribological properties of the ionic liquid lubrication film.A novel ultrathin dual-layer film, which contained both bonded and mobile phases in ionic liquids (ILs) layer, was fabricated successfully on a silicon substrate modified by a self-assembled monolayer (SAM). The formation and surface properties of the films were analyzed using ellipsometer, water contact angle meter, attenuated total reflectance Fourier transform infrared spectroscopy, multi-functional X-ray photoelectron spectroscopy, and atomic force microscope. Meanwhile, the adhesive and nanotribological behaviors of the films were evaluated by a homemade colloidal probe. A ball-on-plate tribometer was used to evaluate the microtribological performances of the films. Compared with the single-layer ILs film deposited directly on the silicon surface, the as-prepared dual-layer film shows the improved tribological properties, which is attributed to the special chemical structure and outstanding physical properties of the dual-layer film, i.e., the strong adhesion between bonded phase of ILs and silicon substrate via the chemical bonding with SAM, the interlinked hydrogen bonds among the molecules, and two-phase structure composed of steady bonded phase with load-carrying capacity and flowable mobile phase with self-replenishment property.

Keywords: Micro/nanotribology; Adhesion; Ionic liquids; SAMs; AFM

The model of rough wetting for hydrophobic steel meshes that mimic Asparagus setaceus leaf by Zai X. Jiang; Lin Geng; Yu D. Huang; Shi A. Guan; W. Dong; Zi Y. Ma (pp. 866-872).
A model is presented to provide a relationship between macroscopic roughness and contact angle, which is used to develop macroscopic roughness and to create biomimetic superhydrophobic surfaces.Display Omitted► A novel model is proposed for hydrophobic surface with macroscopic roughness. ► An artificial hydrophobic mesh surface was prepared using chemical modification. ► Water contact angles as high as 129.0° were achieved.A comprehensive analytical model is proposed to provide a relationship between the macroscopic roughness and contact angle, which is used to develop macroscopic rough surface and to create biomimetic superhydrophobic surfaces. Using chemical surface modification of steel wires, an artificial hydrophobic surface was prepared. A steel mesh mimicking the Asparagus setaceus leaf was created by lowing the surface energy and enhancing macroscopic surface roughness. Water contact angles as high as 129.0° were achieved on the steel mesh with 200μm×200μm pore size. Bad agreement between the predictions based on the original Cassie–Baxter model and experiments was obtained. The version of the Cassie–Baxter model in current use could not be applied to this problem since the roughness magnitude changes from nano/microscopic to macroscopic. A new model, called macroscopic Cassie–Baxter (MCB) model, is constructed by the introduction of contact area density ( δ) to original Cassie–Baxter model. It is shown that the measured data is in good agreement with the predicted data based on the MCB model. This model not only for solving macroscopic hydrophobic problems of meshes, but also can be used to solve that of other materials with macroscopic roughness.

Keywords: Hydrophobic; Steel mesh; Cassie–Baxter model

Induction heating for surface triggering styrene polymerization on titanium modified with ATRP initiator by Bastien Barthélémy; Sébastien Devillers; Isabelle Minet; Joseph Delhalle; Zineb Mekhalif (pp. 873-879).
Schematic temperature profiles representation for a conventional heating method and an induction heating method for triggering the styrene ATRP polymerization on modified titanium substrates.Display Omitted► 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid has been synthesized. ► 11-(2-bromoisobutyrate)-undecyl-1-phosphonic forms a monolayer on Ti substrate. ► This monolayer plays the role of the initiator for styrene ATRP polymerization. ► Two different heating methods have been used: conventional and induction heating. ► Induction heating led a thicker, denser polystyrene layer than conventional heating.Titanium and its alloys present high interests for technological applications due to their high corrosion resistance, mechanical properties and biocompatibility. In combination with these remarkable characteristics, some Ti applications require specific surface properties that can be imparted with suitable surface functionalizations of the TiO2 oxide layer. The present work aims to study the surface-initiated ATR polymerization of styrene on titanium substrates, using grafted 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid as initiator and to compare the impact of two different heating ways on the efficiency of this polymerization: induction vs. conventional heating. The ability of the initiator to bind titanium substrates and act as an initiator for ATRP of styrene is investigated: both heating conditions led to the polymerization of styrene on modified titanium substrates. However, induction heating appeared to be much more efficient than conventional heating, leading to the formation of a thicker, much denser polystyrene layer than conventional heating after only 1h of polymerization.

Keywords: Induction heating; Surface modification; Titanium; ATRP; 11-(2-Bromoisobutyrate)-undecyl-1-phosphonic acid; Styrene

Supramolecular chirality formation of bisazobenzene-substituted polydiacetylene LB films by Xiujuan Pan; Hao Jiang; Yali Wang; Zhangyuan Lei; Gang Zou; Qijin Zhang; Keyi Wang (pp. 880-886).
In this paper, novel bisazobenzene-substituted polydiacetylene LB films were studied on the effects of bisazobenzene chromophores in the side chains on chirality formation for PDA backbone.Display Omitted► Novel bisazobenzene-substituted diacetylene monomer (NBADA) was synthesized. ► The chirality of NBADA films generated by LB assembly, although NBADA was achiral. ► NBADA monomer could be polymerized into helical backbone upon CPUL irradiation. ► The head group packing strongly affect on chirality formation of PDA backbone. ► The helix of PDA chain depends on the competition of above two effects (3 and 4).In order to investigate the exact effect of stereoregular packing of head group in the side chain on the helical structure formation of polydiacetylene backbone, the larger size of bisazobenzene-substituted diacetylene monomer, 4-(4-nitrophenylazo) azobenzene-10, 12-pentacosadiynoate (BNADA) was synthesized successfully. Owing to overcrowded packing of bisazobenzene chromophores, the BNADA Langmuir–Blodgett (LB) films showed macroscopic supramolecular chirality, although BNADA molecules were achiral. Under circularly polarized UV light (CPUL) irradiation, supramolecular helix of bisazobenzene chromophores always maintained, due to the large size and lower photo-isomerization rate of bisazeobenzene chromophores. While for polydiacetylene backbone, the helical direction of the polymer chain should be decided by the competition of the effect of stereoregular packing of bisazobenzene chromophores and the interaction between the CPUL and the diacetylene dimer.

Keywords: Bisazobenzene chromophores; Polydiacetylene; Circularly polarized UV light (CPUL); Supramolecular chirality

Facile synthesis of silver core – silica shell composite nanoparticles by Olivia Niitsoo; Alexander Couzis (pp. 887-890).
Ag@SiO2 core–shell particle formation and the occurrence of byproducts depend on the alcoholic solvent used as well as available silver surface area.Display Omitted► Monodisperse silver nanoparticles in the range of 40–100nm average size are synthesized using saccharides (glucose or maltose) simultaneously as the reducing agent and electrostatic stabilizer. ► When coating of silver nanoparticles with silica from tetraalkoxysilanes, the alcoholic solvent used determines the products. ► The desired Ag@SiO2 core–shell particles are obtained in 2-propanol as well as in ethanol, where silver particle concentration determines the occurrence of coreless silica byproduct.Combining metal nanoparticles and dielectrics (e.g. silica) to produce composite materials with high dielectric constant is motivated by application in energy storage. Control over dielectric properties and their uniformity throughout the composite material is best accomplished if the composite is comprised of metal core – dielectric shell structured nanoparticles with tunable dimensions. We have synthesized silver nanoparticles in the range of 40–100nm average size using low concentration of saccharide simultaneously as the reducing agent and electrostatic stabilizer. Coating these silver particles with silica from tetraalkoxysilanes has different outcomes depending on the alcoholic solvent and the silver particle concentration. A common issue in solution-based synthesis of core–shell particles is heterogeneous nucleation whereupon two populations are formed: the desired core–shell particles and undesired coreless particles of the shell material. We report the formation of Ag@SiO2 core–shell particles without coreless silica particles as the byproduct in 2-propanol. In ethanol, it depends on the silver surface area available whether homogeneous nucleation of silica on silver is achieved. In methanol and 1-butanol, core–shell particles did not form. This demonstrates the significance of controlling the tetraalkoxysilane hydrolysis rate when growing silica shells on silver nanoparticles.

Keywords: Core–shell; Nanoparticles; Silver; Silica; Sol–gel; Solvent effect

New phosphorus-containing spherical carbon adsorbents as promising materials in drug adsorption and release by Marek Wiśniewski; Agnieszka Pacholczyk; Artur P. Terzyk; Gerhard Rychlicki (pp. 891-894).
SEM picture of SCA sample (insert shows a spherical carbon granule).Display Omitted► Phosphoric acid activation of hydrothermally formed spherules creates high surface area carbons. ► Despite of high surface acidity SCAs adsorb pac in large extent with high reversibility. ► Adsorption reversibility depends linearly on the amount of surface phosphorus.A simple method of preparation of new high surface area spherical carbon adsorbents is presented. The phosphoric acid activation upon hydrothermally formed spherules was employed to produce carbons having controlled high specific surface area (over 2100m2/g), large volumes of pores (1.2cm3/g), and high acidity. Prepared from sucrose materials show high adsorption capacities (i.e. 220mg/gC) toward paracetamol. It is proved that for these materials the contents of surface phosphorus are responsible for the reversibility of drug adsorption/release process.

Keywords: Spherical carbon adsorbents; Drug adsorption; Microporous carbons

Water-in-oil emulsion separation within a milli-fluidic device by Janet T. Tesfai; Renee N. Perry; Erin L. Jablonski (pp. 895-899).
Passive separation of a water-in-oil emulsion occurs spontaneously upon introduction into a milli-fluidic device where co-laminar flow of water and oil is stabilized by a hydrogel defining one length of the channel. Separation is achieved on the millimeter scale with separation efficiencies of ∼90% for aqueous solutions dispersed in a continuous oil phase (scale bar 800μm).Display Omitted► Milli-fluidic scale water-in-oil emulsion separation with ∼90% efficiency. ► Stable co-laminar flow of immiscible liquids over several cm of channel length. ► Hydrogel–water interface facilitates breaking water-in-oil emulsion.A milli-fluidic method capable of continuous passive separation of water-in-oil emulsions with an efficiency of ∼90% is described. Experiments used high oleic sunflower oil or mineral oil as the continuous phase and aqueous solutions of methylene blue, crystal violet, or dextran with methylene blue as the dispersed phase. To achieve continuous passive separation, a device with opposing channel walls of disparate hydrophobicity is used to stabilize cocurrent laminar flow of oil and water. The disparity in hydrophobicity of the channel walls is accomplished by defining one length of the channel with a hydrogel, in this case polyethylene glycol. Emulsion separation is facilitated by introducing the emulsion at the water/hydrogel interface. Advantages of performing separations at the milli-fluidic scale are presented.

Keywords: Emulsion; Separation; Milli-fluidic; Hydrogel

No Title by Arthur Hubbard (pp. 900-900).
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