Journal of Colloid And Interface Science (v.341, #1)
2009 Reviewer List (iii-ix).
Cover 1 (OFC).
Conducting polymer nanostructures and their application in biosensors by Lin Xia; Zhixiang Wei; Meixiang Wan (1-11).
This article reviews hard- and soft-template methods for the synthesis of conducting polymer nanostructures, and their application as transducer materials for high performance biosensors.Nowadays, functionalized conducting polymer nanomaterials have been received great attention in nanoscience and nanotechnology because of their large surface area. This article reviews various methods for synthesis of conducting polymer nanostructures and their applications in sensing materials, focusing on hard-template, soft-template and other methods and the formation mechanism of conducting polymer nanostructures by these methods. Conducting polymer nanostructures, such as nanotubes, nanowires, and nanoparticles, as sensing platforms for various applications are also summarized.
Keywords: Conducting polymers; Nanostructures; Hard-template; Soft-template; Biosensors;
Facile synthesis of CeO2 nanoplates and nanorods by [1 0 0] oriented growth by Hsin-Lung Lin; Cheng-Yu Wu; Ray-Kuang Chiang (12-17).
This study demonstrated a facile method for the fast synthesis of CeO2 nanoplates and nanorods via the thermal decomposition of a mixture of cerium acetate, oleic acid, oleyamine and 1-octadecene under air atmospheres. The way of addition of the activator and the reaction atmosphere are found to the two key factors for the fast morphology-selective syntheses of CeO2 nanoplates and nanorods.This study demonstrated a facile method for the synthesis of CeO2 nanoplates and nanorods via the thermal decomposition of a mixture of cerium acetate, oleic acid, oleyamine and 1-octadecene under controlled atmospheres. Morphologies of the produced cerium oxides were controlled by the adding procedures of activators. Activators added at room temperature and heated with the reaction mixture result in the formation of nanoplates. Injection of activators at high temperature leads to the formation of nanorods. Both the nanoplates and nanorods are achieved via the [1 0 0] oriented assembly of smaller particles. A blue-shifting of the UV absorption threshold edge are observed for the cerium oxide nanoplates and nanorods, contrasting with the bulk commercial powders.
Keywords: Cerium oxide; Thermal decomposition; Preferred orientation; Nanoplates; Nanorods;
Silica-coated iron nanocubes: Preparation, characterization and application in microwave absorption by Xiaomin Ni; Zhong Zheng; Xiang Hu; Xiukun Xiao (18-22).
Silica-coated iron nanocubes exhibited improved magnetic properties, oxidation resistance and microwave absorption performance as compared with the iron cubes without silica coating.Novel cubic nanocapsules consisting of metallic iron core and amorphous silica shell were fabricated through a simple chemical reduction route followed by a Stöber process. Thus-prepared Fe@SiO2 nanocubes were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectrometer (FTIR), thermogravimetry-differential thermal analysis (TG-DTA), vibrating sample magnetometer (VSM) and scalar network analysis (SNA). Comparing with that of pure iron counterparts, silica-coated iron nanocubes exhibited improved magnetic properties, oxidation resistance and microwave absorption performance. A reflection loss (RL) exceeding −12 dB was obtained in the frequency range of 8–14 GHz for an absorber thickness of 2 mm, with an optimal RL of −18.2 dB at 9 GHz. Mechanism of the improved microwave absorption properties of the Fe@SiO2 composite was discussed based on their magnetic properties and electromagnetic theory.
Keywords: Nanocubes; Iron; Silica coating; Microwave absorption; Magnetization;
Preparation of spherical silica particles by Stöber process with high concentration of tetra-ethyl-orthosilicate by Xiao-Dong Wang; Zheng-Xiang Shen; Tian Sang; Xin-Bin Cheng; Ming-Fang Li; Ling-Yan Chen; Zhan-Shan Wang (23-29).
Silica particles in the range of 920–940 nm are obtained for 1.24 M TEOS at 5 °C, which results in 7.45% solid content in the suspension.In this paper, Stöber process with high concentration of tetra-ethyl-orthosilicate (TEOS) up to 1.24 M is used to prepare monodisperse and uniform-size silica particles. The reactions are carried out at [TEOS] = 0.22–1.24 M, low concentrations of ammonia ([NH3] = 0.81[TEOS]), and [H2O] = 6.25[TEOS] in isopropanol. The solids content in the resulting suspension achieves a maximum value of 7.45% at 1.24 M TEOS. Various-sized particles in the range of 30–1000 nm are synthesized. The influences of TEOS, NH3, and H2O on the size and size distribution of the particles are discussed. A modified monomer addition model combined with aggregation model is proposed to analyze the formation mechanism of silica particles.
Keywords: Silica; Solid content; Hydrolysis; Condensation;
TOF-SIMS analysis of structured surfaces biofunctionalized by a one-step coupling of a spacer-linked GRGDS peptide by Andre Petershans; Andrey Lyapin; Stefan Reichlmaier; Sviatlana Kalinina; Doris Wedlich; Hartmut Gliemann (30-37).
TOF-SIMS investigation of microstructured substrates, biofunctionalized by the covalent one-step coupling of a spacer-linked GRGDS peptide for specific cell adhesion.Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) was applied to validate GRGDS peptide patterned surfaces. The structuring of the surfaces included several steps: micro contact printing (μCP), chemical etching and aminofunctionalization followed by chemical coupling of spacer-linked GRGDS peptides via an isothiocyanate anchor. TOF-SIMS analysis of characteristic ions and molecular fragments with a lateral resolution of 100 nm allowed proving the change in chemical properties of the surface with each step during the structuring process. We found that the application of polydimethylsiloxane as stamp material resulted in the contamination of the surface with this polymer. TOF-SIMS investigations, however, also showed that during the preparation process the contaminations were removed and do not influence the bio functionality of the surface patterns. The results of the surface analysis carried out with TOF-SIMS were confirmed by complementary cell adhesion experiments with murine fibroblasts. As a result, specific cell adhesion restricted to GRGDS peptide functionalized areas was obvious by the formation of focal adhesion contacts in the fibroblasts. Thus, TOF-SIMS is the method of choice in chemical characterization of surfaces in structuring and functionalization processes, because it offers the opportunity to follow surface contamination during the preparation process and to assess the influence of the contamination on the applicability of the final substrate.
Keywords: TOF-SIMS; RGD peptide; Micro contact printing; Chemical surface pattern; Cell adhesion; PDMS;
12-Hydroxystearic acid lipid tubes under various experimental conditions by Anne-Laure Fameau; Bérénice Houinsou-Houssou; Bruno Novales; Laurence Navailles; Frédéric Nallet; Jean-Paul Douliez (38-47).
We report the variation of various physico-chemical parameters on the self-assembly of 12-hydroxy-stearic acid in water which is known to form tubes of several tens of micrometers in length with a temperature-tunable diameter.There is a growing interest for constructing supramolecular hollow tubes from amphiphilic molecules. Aqueous solutions of the ethanolamine salt of 12-hydroxystearic acid are known to form tubes of several tens of micrometers in length with a temperature-tunable diameter. However, the phase behavior of this system has not been fully studied. Herein, we report the variation of various physico-chemical parameters on the self-assembling properties of this system. The effects of the ionic strength, ethanol, doping with other lipids, pH, concentration, and the fatty acid/ethanolamine molar ratio R were investigated by both phase-contrast microscopy and DSC. We observed the formation of tubes in a wide range of parameters. For instance, the molar ratio R can be modified from 2/3 to 5/2 without altering the formation of tubes. In some but not all cases, the tube diameter still varied with temperature. These findings show that tubes form under various experimental conditions. This should increase the interest in producing such self-assemblies from low-cost fatty acids.
Keywords: Lipid tubes; Hydroxy fatty acids; Self-assembly;
Nanoparticles of nickel oxide and nickel hydroxide using lyophilisomes of fibrinogen as template by J. Daisy Vimala Rani; S. Kamatchi; A. Dhathathreyan (48-52).
Nanoparticles of nickel oxide and hydroxide from stable microcapsules or lyophilisomes of fibrinogen and nickel chloride have been formed using a simple complexation-reduction process followed by heating. The results show that the NiO particles are well dispersed, with an average particle size of about 28 nm, and the specific surface area is 34 m2/g.Stable lyophilisomes of fibrinogen at pH 7.5 have been prepared by the method of a rapid freezing–heating and annealing sequence. Reduction of the lyophilisomes of the nickel–fibrinogen complex coated on solid substrates and subsequent heating showed formation of nickel hydroxide and finally nickel oxide. Ultraviolet–visible spectroscopy has been used to monitor the thin films of pure fibrinogen microcapsules, as well as the subsequent nucleation and growth of nanoparticles within the supramolecular structure. Transmission electron microscopy showed initially a thread-like structure which disappeared on continued heating, resulting in nanoparticles ranging from 10 to 50 nm. Particle-size distribution of product was analyzed by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED), and Brunauer–Emmett–Teller (BET) N2 adsorption. The results suggest that the NiO particles have a body-centered cubic structure and are well dispersed. The particle-size distribution ranges from 10 to 50 nm with an average particle size about 28 nm, and the specific surface area is 34 m2/g. Magnetic study carried out on the prepared nanoparticles showed a ferromagnetic behavior.
Keywords: Nanoclusters; Nickel oxide; Encapsulation; Fibrinogen; Nickel hydroxide; Template; Lyophilisomes; Circular dichroism spectra; Electron diffraction; BET;
Plasma-induced graft-polymerization of polyethylene glycol acrylate on polypropylene films: Chemical characterization and evaluation of the protein adsorption by Stefano Zanini; Claudia Riccardi; Elisa Grimoldi; Claudia Colombo; Anna Maria Villa; Antonino Natalello; Pietro Gatti-Lafranconi; Marina Lotti; Silvia Maria Doglia (53-58).
Ar plasma treatments were employed to graft-polymerize a polyethylene glycol acrylate onto polypropylene films surfaces and the resulting PEGylated surface shows a decreased protein adsorption.This work deals with the optimization of argon plasma-induced graft-polymerization of polyethylene glycol acrylate (PEGA) on polypropylene (PP) films in order to obtain surfaces with a reduced protein adsorption for possible biomedical applications. To this end, we examined the protein adsorption on the treated and untreated surfaces. The graft-polymerization process consisted of four steps: (a) plasma pre-activation of the PP substrates; (b) immersion in a PEGA solution; (c) argon plasma-induced graft-polymerization; (d) washing and drying of the samples. The efficiency of these processes was evaluated in terms of the amount of grafted polymer, coverage uniformity and substrates wettability. The process was monitored by contact angle measurements, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS) and atomic force microscopy (AFM) analyses. The stability of the obtained thin films was evaluated in water and in Phosphate Buffer Saline (PBS) at 37 °C. The adsorption of fibrinogen and green fluorescent protein (GFP) – taken as model proteins – on the differently prepared surfaces was evaluated through a fluorescence approach using laser scanning confocal microscopy with photon counting detection. After plasma treatments of short duration, the protein adsorption decreases by about 60–70% with respect to that of the untreated film, while long plasma exposure resulted in a higher protein adsorption, due to damaging of the grafted polymer.
Keywords: Cold plasma; Biocompatibility; Graft copolymers; Proteins adsorption;
Reverse micelle-derived Cu-doped Zn1− x Cd x S quantum dots and their core/shell structure by Jong-Uk Kim; Young Kwan Kim; Heesun Yang (59-63).
A 0.45 nm thick ZnS shell was overcoated on Zn0.5Cd0.5S:Cu core QDs, resulting in 9.4% of quantum yield from core/shell QDs.Reverse micelle chemistry-derived Cu-doped Zn1− x Cd x S quantum dots (QDs) with the composition (x) of 0, 0.5, 1 are reported. The Cu emission was found to be dependent on the host composition of QDs. While a dim green/orange emission was observed from ZnS:Cu QDs, a relatively strong red emission could be obtained from CdS:Cu and Zn0.5Cd0.5S:Cu QDs. Luminescent properties of undoped QDs versus Cu-doped ones and quantum yields of alloyed ZnCdS versus CdS QDs are compared and discussed. To enhance Cu-related red emission of CdS:Cu and Zn0.5Cd0.5S:Cu core QDs, core/shell structured QDs with a wider band gap of ZnS shell are also demonstrated.
Keywords: Cu-doped; Zn1− x Cd x S; Quantum dots; Reverse micelle; Core/shell;
Preparation of hybrid hollow capsules formed with Fe3O4 and polyelectrolytes via the layer-by-layer assembly and the aqueous solution process by Masato Nakamura; Kiyofumi Katagiri; Kunihito Koumoto (64-68).
Well-defined magnetic hybrid hollow capsules were successfully prepared through a colloidal templating with layer-by-layer assembly of polyelectrolytes, followed by aqueous solution deposition of Fe3O4 using Pd catalysts.Well-defined magnetic hybrid hollow capsules formed with magnetite (Fe3O4) and polyelectrolyte-multilayer films were successfully prepared through colloidal templating with layer-by-layer assembly of polyelectrolytes, followed by aqueous solution deposition of Fe3O4. Pd catalyst nanoparticles played an important role in the deposition of Fe3O4. Pd nanoparticles favorably adsorbed onto the polyelectrolyte layer with positively charged amino groups. Hollow capsules were obtained by the removal of the melamine–formaldehyde core particles. Although the processes were performed in aqueous solutions at temperatures less than 60 °C, X-ray diffraction patterns revealed that the deposited Fe3O4 was highly crystallized. The hollow capsules were stably dispersed in water; however, the capsules rapidly congregated around a locally applied magnet.
Keywords: Hollow capsules; Layer-by-layer assembly; Colloid templating; Magnetic particles;
Low-molecular-weight gelators based on N α-acetyl-N ε-dodecyl-L-lysine and their amphiphilic gelation properties by Masahiro Suzuki; Tomoko Abe; Kenji Hanabusa (69-74).
Nα -Acetyl-Nε -dodecyl-L-lysine, which can be synthesized with simply synthetic procedure, high reaction yield and low cost, functions as an amphiphilic gelator that forms a supramolecular hydrogel and organogel.A simple amphiphilic low-molecular-weight gelator based on L-lysine, N α-acetyl-N ε-lauroyl-L-lysine (1), its alkali metal salts [Na (2) and K (3)], and two-component gelators [1 and 2 and 1 and 3] were synthesized. Compound 1 had a good hydrogelation ability that formed a pure water gel at 2 g L−1 (0.2 wt.%) and a saline gel at 4 g L−1 (0.4 wt.%). Two-component compounds were able to form hydrogels in aqueous solutions containing alkali metal and alkali earth metal ions in addition to pure water and saline. Although 1 formed organogels in a few organic solvents, two-component compounds also functioned as a good organogelator. The FT-IR study indicated that the driving forces for the formation of supramolecular gels were hydrogen-bonding and hydrophobic interactions. Furthermore, the thermal properties of the hydrogels are discussed.
Keywords: Organogel; L-Lysine; Nanofiber; Supramolecular chemistry;
Bilayers coating on titanium surface: The impact on the hydroxyapatite initiation by Christelle Arnould; Jessica Denayer; Michael Planckaert; Joseph Delhalle; Zineb Mekhalif (75-82).
Scheme of the three main steps followed in this paper: (1). tantalum sol–gel deposition on bare titanium, (2). organophosphonic acids grafting, (3). impact of coatings on hydroxyapatite growth rate.Most of the actual orthopaedic devices, widely made of titanium and its alloys, present different weaknesses like ions release and risks of loosening over a long period. To solve such problems, new developments in surface modification are crucial. This work is an extension of our recent effort on the development and improvement of a multifunctional inorganic/organic bilayers coating. A thin tantalum oxide layer is formed by sol–gel synthesis followed by the modification with organophosphonic acids of the tantalum oxide layer. We focus in particular on the effect of the bilayers coating on corrosion resistance and hydroxyapatite growth rate by immersion in a simulated body fluid solution. It is also highlighted that the structure of the organophosphonic acid is of major importance on the osteoinduction character of the material.
Keywords: Biomaterials; Hydroxyapatite; Tantalum oxide; Titanium; Sol–gel; Phosphonic acids;
Plasmonic photocatalytic system using silver chloride/silver nanostructures under visible light by Moonjung Choi; Kyoung-Hwan Shin; Jyongsik Jang (83-87).
Plasmonic photocatalytic nanostructured system was investigated on silver chloride/silver nanoparticles under visible light. Silver chloride/silver nanoparticles were readily prepared using dispersing agent and light irradiation.Plasmonic photocatalytic nanostructured system was investigated on silver chloride/silver nanoparticles under visible light. Silver chloride/silver nanoparticles were readily prepared using dispersing agent and light irradiation. The d-spacing analysis, high resolution-transmission electron microscopy, X-ray diffraction analysis and diffuse-reflectance spectroscopy demonstrated that silver nanoparticles were introduced on the surface of silver chloride nanoparticles and then silver chloride/silver nanostructured photocatalytic materials were successfully synthesized. The as-synthesized plasmonic photocatalysts exhibited the enhanced photocatalytic performance over nitrogen-doped titania nanomaterials. The improved catalytic activity was originated from the enhanced adsorption for visible light, electron–hole separation, and the formation of chloride atoms in silver chloride/silver nanostructured materials.
Keywords: Photocatalyst; Nanostructure; Visible light; Dye decomposition; Silver halide;
Synthesis and characterization of Poly(N-isopropylacrylamide)/Poly(acrylic acid) semi-IPN nanocomposite microgels by Jinghong Ma; Bing Fan; Borun Liang; Jian Xu (88-93).
The PNIPA/PAAc semi-IPN microgels prepared via surfactant-free emulsion polymerization by using inorganic clay as a crosslinker have small particle size and exhibit good pH- and temperature-sensitivity.A novel pH- and temperature-sensitive nanocomposite microgel based on linear Poly(acrylic acid) (PAAc) and Poly(N-isopropylacrylamide) (PNIPA) crosslinked by inorganic clay was synthesized by a two-step method. First, PNIPA microgel was prepared via surfactant-free emulsion polymerization by using inorganic clay as a crosslinker, and then AAc monomer was polymerized within the PNIPA microgel. The structure and morphology of the microgel were confirmed by FTIR, WXRD and TEM. The results indicated that the exfoliated clay platelets were dispersed homogeneously in the PNIPA microgels and acted as a multifunctional crosslinker, while the linear PAAc polymer chains incorporated in the PNIPA microgel network to form a semi-interpenetrating polymer network (semi-IPN) structure. The hydrodynamic diameters of the semi-IPN microgels ranged from 360 to 400 nm, which was much smaller than that of the conventional microgel prepared by using N,N′-methylenebis(acrylamide) (MBA) as a chemical crosslinker, the later was about 740 nm. The semi-IPN microgels exhibited good pH- and temperature-sensitivity, which could respond independently to both pH and temperature changes.
Keywords: Microgels; Clay; Nanocomposite; pH- and temperature-sensitivity; Semi-interpenetrating polymer networks (semi-IPN);
Alkyl chain length-dependent viscoelastic properties in aqueous wormlike micellar solutions of anionic gemini surfactants with an azobenzene spacer by Binglei Song; Yufang Hu; Yongming Song; Jianxi Zhao (94-100).
The solutions of newly synthesized gemini surfactants with an azobenzene spacer show strong chain length-dependent viscoelasticity at relatively low concentrations without any additives.A homologue of carboxylate gemini surfactants with an azobenzene spacer and different lengths of the alkyl tails, referred to as C m (azo)C m , has been synthesized. All the surfactants formed wormlike micelles at relatively low concentrations without addition of salt. The reason was attributed to the long and rigid characteristic of the azobenzene spacer, which yielded the pseudo volume between the two tails and thus a columnar-like molecular geometry favorable for the formation of wormlike micelles. The results of rheology and FF-TEM measurements showed that the length of the alkyl tails strongly affected the viscoelastic properties of the wormlike micelle solution. With the increase of the alkyl tail length, the solutions evolved from a typically viscous fluid to a strong viscoelastic solution and then to a gel-like state. This was attributed to the different microstates as revealed by scaling law. These solutions behave as polyelectrolyte systems because of their additive-free nature.
Keywords: Anionic gemini surfactants; Azobenzene spacer; Wormlike micelle; Viscoelastic properties; Alkyl chain-length dependence;
Effect of calcium salts and surfactant concentration on the stability of water-in-oil (w/o) emulsions prepared with polyglycerol polyricinoleate by Andrés L. Márquez; Alejandra Medrano; Luis A. Panizzolo; Jorge R. Wagner (101-108).
Effect of PGPR and calcium concentrations on the destabilization percentage (%D) of w/o emulsions. The stability to coalescence and sedimentation increases with increasing PGPR and/or calcium contents.The objective of this work was to obtain water-in-oil (w/o) emulsions with polyglycerol polyricinoleate (PGPR) as emulsifier and to study the effect of the addition of calcium in the dispersed aqueous phase on the stability of these systems. Emulsions were formulated with 0.2, 0.5 and 1.0% w/w PGPR and 10% w/w water containing calcium chloride at varied concentrations or other salts (calcium lactate or carbonate; sodium, magnesium or potassium chloride). The stability of these systems was studied with a vertical scan analyzer during 15 days; coalescence and sedimentation were observed as simultaneous destabilization processes. The increase of PGPR concentration and/or calcium chloride content gave more stable emulsions. The stabilizing effect of calcium salt was attributed to the diminution of the water droplets size, the decrease of the attractive force between water droplets and the increase of the adsorption density of the emulsifier. The viscoelastic parameters of the interfacial film were decreased with increasing calcium and PGPR concentrations. Calcium chloride produced a higher increase of stability than calcium salts with lower dissociation degree. The presence of any assayed salt in the aqueous phase also allowed the stabilization of w/o emulsions with higher water contents.
Keywords: PGPR; W/o emulsions; Calcium; Coalescence; Sedimentation; Interfacial rheology;
The role of charged surfactants in the thermal and structural properties of lyotropic liquid crystalline mesophases of [Zn(H2O)6](NO3)2–C n EO m –H2O by Cemal Albayrak; Aslı M. Soylu; Ömer Dag (109-116).
The liquid crystalline assembly of CTAB–C12EO10 and SDS–C12EO10 with [Zn(H2O)6](NO3)2 salt can accommodate up to 8.0 metal ion per C12EO10 in the hydrophilic domains of this soft matter.The mixtures of [Zn(H2O)6](NO3)2 salt, 10-lauryl ether (C12H25(OCH2CH2)10OH, represented as C12EO10), a charged surfactant (cetyltrimethylammonium bromide, C16H33N(CH3)3Br, represented as CTAB or sodium dodecylsulfate, C12H25OSO3Na, SDS) and water form lyotropic liquid crystalline mesophases (LLCM). This assembly accommodates up to 8.0 Zn(II) ions (corresponds to about 80% w/w salt/(salt + C12EO10)) for each C12EO10 in the presence of a 1.0 CTAB (or 0.5 SDS) and 3.5 H2O in its LC phase. The salt concentration can be increased by increasing charged surfactant concentration of the media. Addition of charged surfactant to the [Zn(H2O)6](NO3)2–C12EO10 mesophase not only increases the salt content, it can also increase the water content of the media. The charged surfactant-C12EO10 (hydrophobic tail groups) and the surfactant (head groups)-salt ion (ion-pair, hydrogen-bonding) interactions stabilize the mesophases at such salt high and water concentrations. The presence of both Br− and NO 3 - ions influences the thermal and structural properties of the [Zn(H2O)6](NO3)2–C12EO10–CTAB(or SDS)–H2O LLCM, which have been investigated using XRD, POM (with a hot stage), FT-IR and Raman techniques.
Keywords: CTAB; SDS; C12EO10; Lyotropic liquid crystals; Transition metal salt; Mesophase;
Structural and thermal study of mesomorphic dodecylammonium carrageenates by M. Vinceković; A. Pustak; Lj. Tušek-Božić; F. Liu; G. Ungar; M. Bujan; I. Šmit; N. Filipović-Vinceković (117-123).
Model of dodecylammonium carrageenate in the layered liquid crystalline state after a short annealing dynamics simulation: carbon (dark gray), hydrogen (light gray), oxygen (red), sulphate (yellow), nitrogen (blue).Structural characteristics and thermal stability of a series of dodecylammonium carrageenates formed by stoichiometric complexation of dodecylammonium chloride and differently charged carrageenans (κ-, ι- and λ-carrageenan, respectively) were investigated. IR spectral analysis confirmed the electrostatic and hydrogen bond interactions between the dodecylammonium and carrageenan species. X-ray diffraction experiments show increased ordering in the complexes compared to that in the parent carrageenans. Dodecylammonium carrageenates have a layer structure, in which a polar sublayer contains layers of carrageenan chains and a nonpolar sublayer consists of conformationally disordered dodecylammonium chains electrostatically attached to the carrageenan backbone. The major factor that determines the dodecylammonium carrageenate structure is cationic surfactant, while the carrageenans moiety plays a major role in determining thermal properties.
Keywords: Dodecylammonium chloride; Carrageenans; Surfactant–polymer complexes;
Langmuir films of flexible polymers transferred to aqueous/liquid crystal interfaces induce uniform azimuthal alignment of the liquid crystal by Michael I. Kinsinger; Maren E. Buck; Maria-Victoria Meli; Nicholas L. Abbott; David M. Lynn (124-135).
We report that Langmuir films of flexible polymers transferred to aqueous/liquid crystal interfaces using Langmuir–Schaefer methods induce uniform azimuthal alignment of the liquid crystal.We reported recently that amphiphilic polymers can be assembled at interfaces created between aqueous phases and thermotropic liquid crystals (LCs) in ways that: (i) couple the organization of the polymer to the order of the LC and (ii) respond to changes in the properties of aqueous phases that can be characterized as changes in the optical appearance of the LC. This investigation sought to characterize the behavior of aqueous–LC interfaces decorated with uniaxially compressed thin films of polymers transferred by Langmuir–Schaefer (LS) transfer. Here, we report physicochemical characterization of interfaces created between aqueous phases and the thermotropic LC 4-cyano-4′-pentylbiphenyl (5CB) decorated with Langmuir films of a novel amphiphilic polymer (polymer 1), synthesized by the addition of hydrophobic and hydrophilic side chains to poly(2-vinyl-4,4′-dimethylazlactone). Initial characterization of this system resulted in the unexpected observation of uniform azimuthal alignment of 5CB after LS transfer of the polymer films to aqueous–5CB interfaces. This paper describes characterization of Langmuir films of polymer 1 hosted at aqueous–5CB interfaces as well as the results of our investigations into the origins of the uniform ordering of the LC observed upon LS transfer. Our results, when combined, support the conclusion that uniform azimuthal alignment of 5CB is the result of long-range ordering of polymer chains in the Langmuir films (in a preferred direction orthogonal to the direction of compression) that is generated during uniaxial compression of the films prior to LS transfer. Although past studies of Langmuir films of polymers at aqueous–air interfaces have demonstrated that in-plane alignment of polymer backbones can be induced by uniaxial compression, these past reports have generally made use of polymers with rigid backbones. One important outcome of this current study is thus the observation of anisotropy and long-range order in Langmuir films of a novel flexible polymer. A second important outcome is the observation that the existence, extent, and dynamics of this order can be identified and characterized optically by transfer of the Langmuir film to a thin film of LC. Additional characterization of Langmuir films of two other flexible polymers [poly(methyl methacrylate) and poly(vinyl stearate)] using this method also resulted in uniform azimuthal alignment of 5CB, suggesting that the generation of long-range order in uniaxially compressed Langmuir films of polymers may also occur more generally over a broader range of polymers with flexible backbones.
Keywords: Langmuir–Schaefer; Polymer; Liquid crystals; Interfaces; Uniform alignment;
Efficiency of blocking of non-specific interaction of different proteins by BSA adsorbed on hydrophobic and hydrophilic surfaces by Y.L. Jeyachandran; J.A. Mielczarski; E. Mielczarski; B. Rai (136-142).
Adsorbed BSA produces low density structures (less than a monolayer), which show significant blocking property of non-specific adsorption of different proteins on solid substrates.The efficiency of a pre-absorbed bovine serum albumin (BSA) layer in blocking the non-specific adsorption of different proteins on hydrophobic and hydrophilic surfaces was evaluated qualitatively and quantitatively using infrared reflection spectroscopy supported by spectral simulations. A BSA layer with a surface coverage of 35% of a close-packed monolayer exhibited a blocking efficiency of 90–100% on a hydrophobic and 68–100% on a hydrophilic surface, with respect to the non-specific adsorption of concanavalin A (Con A), immunoglobulin G (IgG), and staphylococcal protein A (SpA). This BSA layer was produced using a solution concentration of 1 mg/mL and 30 min incubation time. BSA layers that were adsorbed at conditions commonly employed for blocking (a 12 h incubation time and a solution concentration of 10 mg/mL) exhibited a blocking activity that involved competitive adsorption–desorption. This activity resulted from the formation of BSA–phosphate surface complexes, which correlated with the conformation of adsorbed BSA molecules that was favourable for blocking. The importance of optimisation of the adsorbed BSA layer for different surfaces and proteins to achieve efficient blocking was addressed in this study.
Keywords: BSA; Blocking efficiency; Adsorption of proteins; Quantification;
Nonlinear response of the surface electrostatic potential formed at metal oxide/electrolyte interfaces. A Monte Carlo simulation study by Piotr Zarzycki; Kevin M. Rosso (143-152).
Lattice two-dielectric phase representation of the metal oxide/electrolyte interface used to study nonlinearity effects in electrostatic response of the interface to the change in pH.An analysis of surface potential nonlinearity (ψ 0) at metal oxide/electrolyte interfaces is presented. By using grand canonical Monte Carlo simulations of a simple lattice model of an interface, we show that a correlation exists between ionic strength, as well as surface site densities, and the non-Nernstian response of a metal-oxide electrode. We propose two approaches to deal with the ψ 0-nonlinearity: one based on perturbative expansion of the Gibbs free energy and another based on the assumption of the pH dependence of surface potential slope. The theoretical analysis based on our new potential form gives excellent performance in extreme pH regions, where classical formulae for ψ 0 are unjustified. The new formula is general and independent of any underlying assumptions. For this reason, it can be directly applied to experimental surface potential measurements, including those for individual surfaces of single crystals, as we present for data reported by Kallay and Preočanin .
Keywords: Surface potential; Metal oxide; Non-Nernstian behavior; Computer simulation; Single crystal electrode;
Synthesis, characterization of palygorskite supported zero-valent iron and its application for methylene blue adsorption by Ray L. Frost; Yunfei Xi; Hongping He (153-161).
The effect of mixing time on the removal of methylene blue using zero-valent iron on palygorskite substrate.In this work, natural palygorskite impregnated with zero-valent iron (ZVI) was prepared and characterized. The combination of ZVI particles on surface of fibrous palygorskite can help to overcome the disadvantage of ultra-fine powders which may have strong tendency to agglomerate into larger particles, resulting in an adverse effect on both effective surface area and catalyst performance. There is a significant increase of methylene blue (MB) decolourized efficiency on acid treated palygorskite with ZVI grafted, within 5 min, the concentration of MB in the solution was decreased from 94 mg/L to around 20 mg/L and the equilibration was reached at about 30–60 min with only around 10 mg/L MB remained in solution. Changes in the surface and structure of prepared materials were characterized using X-ray diffraction (XRD), infrared (IR) spectroscopy, surface analysing and scanning electron microscopy (SEM) with element analysis and mapping. Comparing with zero-valent iron and palygorskite, the presence of zero-valent iron reactive species on the palygorskite surface strongly increases the decolourization capacity for methylene blue, and it is significant for providing novel modified clay catalyst materials for the removal of organic contaminants from waste water.
Keywords: Zero-valent iron; Sepiolite; Attapulgite; Palygorskite; XRD; SEM; EDX; Infrared spectroscopy; Adsorption–desorption; Methylene blue;
Investigation of copper oxide impregnants prepared from various precursors for respirator carbons by J.W.H. Smith; P. Westreich; A.J. Smith; H. Fortier; L.M. Croll; J.H. Reynolds; J.R. Dahn (162-170).
Scanning electron microscope image of the inner surface of a granule of activated carbon that has been impregnated with copper oxide.Copper oxide impregnated activated carbon was prepared by three methods and studied as a respirator carbon. Using techniques such as dynamic flow testing, X-ray diffraction (XRD), thermal analysis, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), copper oxide impregnants, derived from different sources such as basic copper carbonate (Cu2CO3(OH)2), copper nitrate (Cu(NO3)2) and copper chloride (CuCl2) reacted with sodium hydroxide (NaOH), have been studied. Dynamic flow tests performed using sulfur dioxide (SO2), ammonia (NH3) and hydrogen cyanide (HCN) challenge gases allow the determination of the stoichiometric ratio of reaction (SRR) between challenge gas and impregnant. Thermal gravimetric analysis experiments showed that an inert heating environment was required when thermally decomposing the Cu(NO3)2 impregnant to CuO to avoid damaging the activated carbon substrate. SEM has been used to investigate dispersal and particle size of the impregnant on the activated carbon. XRD permits the identification of crystalline and amorphous phases as well as the grain size of the impregnant. XRD analysis of samples before and after exposure to SO2 has allowed the active impregnant in SO2 adsorption to be identified. The relationship between SRR, impregnant loading and grain size is discussed. Methods to improve impregnant distribution are presented and their impact discussed.
Keywords: Impregnated activated carbon; Impregnant distribution; Impregnant grain size; Nitric acid treatment; Gas adsorption capacity; Relative stoichiometric ratio of reaction;
Forced impregnation of a capillary tube with drop impact by Aline Delbos; Elise Lorenceau; Olivier Pitois (171-177).
A liquid drop impacts onto the single pore of a porous media. Under certain conditions of impact velocity or pore radius, a liquid slug can be trapped durably within the porosity.We experimentally investigate how the impregnation of porous media can be forced using the initial kinetic energy of an impacting drop. We focus on the scale of a single pore – either hydrophilic or hydrophobic – and thus study the impact of a single drop falling on vertical cylindrical capillary tubes. This experimental configuration therefore differs from the impregnation of a porous media because of the finite volume of the drop and its initial kinetic energy. We observe different limit regimes: at low impact velocity, we recover the classical results for impregnation. The liquid does not impregnate the hydrophobic pore while it is totally sucked into the hydrophilic one. At high impact velocities, the drop is broken in two parts: one part spreads at the top of the surface while an isolated slug is trapped within the pore. We determine the critical speeds for these regimes and obtain a full phase-diagram for our observations. We also stress the characteristics of impregnating slugs namely their volume and their motion within the pores.
Keywords: Porous media; Impregnation; Drop impact;
Analytical solution of Poisson–Boltzmann equation for interacting plates of arbitrary potentials and same sign by M. Polat; H. Polat (178-185).
Efficient calculation of electrostatic interactions in colloidal systems is becoming more important with the advent of such probing techniques as atomic force microscopy. Such practice requires solving the nonlinear Poisson–Boltzmann equation (PBE). Unfortunately, explicit analytical solutions are available only for the weakly charged surfaces. Analysis of arbitrarily charged surfaces is possible only through cumbersome numerical computations. A compact analytical solution of the one-dimensional PBE is presented for two plates interacting in symmetrical electrolytes. The plates can have arbitrary surface potentials at infinite separation as long they have the same sign. Such a condition covers a majority of the colloidal systems encountered. The solution leads to a simple relationship which permits determination of surface potentials, surface charge densities, and electrostatic pressures as a function of plate separation H for different charging scenarios. An analytical expression is also presented for the potential profile between the plates for a given separation. Comparison of these potential profiles with those obtained by numerical analysis shows the validity of the proposed solution.
Keywords: Poisson–Boltzmann; Colloidal; Electrostatic interaction; Analytical solution;
New synthesis strategies for effective functionalization of kaolinite and saponite with silylating agents by Lilian R. Avila; Emerson H. de Faria; Katia J. Ciuffi; Eduardo J. Nassar; Paulo S. Calefi; Miguel A. Vicente; Raquel Trujillano (186-193).
Kaolinite, previously intercalated with dimethyl sulfoxide, and saponite, has been successfully functionalized with the alkoxysilanes 3-aminopropyltriethoxysilane (APTS) and 3-mercaptopropyltrimethoxysilane (MPTMS).Functionalization of Brazilian São Simão kaolinite and Spanish Yunclillos saponite with the alkoxysilanes 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane is reported. The resulting hybrids were characterized by X-ray diffraction, thermal analysis, infrared absorption spectroscopy, and scanning electron microscopy, which demonstrated the effectiveness of the interlamellar grafting process. The X-ray diffractograms revealed incorporation of the alkoxide molecules into the interlayer space of the clays. The displacement of the stretching bands of interlayer hydroxyls in the infrared spectra of the modified kaolinites and the increased intensity of the Mg–OH vibrations in the spectra of the modified saponites confirmed the functionalization of the clays. The thermal behavior of the organoclays confirmed the stability of the hybrids, which was dependent on the clay used for preparation of the materials.
Keywords: Kaolinite; Functionalization; 3-Aminopropyltriethoxysilane; 3-Mercaptopropyltrimethoxysilane;
Facile synthesis of Fe3O4 nanoparticles by reduction phase transformation from γ-Fe2O3 nanoparticles in organic solvent by Hoang Tri Hai; Hiroaki Kura; Migaku Takahashi; Tomoyuki Ogawa (194-199).
Monodisperse Fe3O4 nanoparticles were synthesized from the corresponding γ-Fe2O3 nanoparticles in organic solvent by exploiting the phase transformation induced by reduction.A phase transformation induced by the reduction of as-synthesized γ-maghemite (γ-Fe2O3) nanoparticles was performed in solution by exploiting the reservoir of reduction gas (CO) generated from the incomplete combustion reaction of organic substances in the reactor. Results from X-ray diffraction, color indicator, and magnetic analysis using a SQUID strongly support this phase transformation. Based on this route, monodisperse magnetite (Fe3O4) nanoparticles were simply produced in the range from 260 to 300 °C. Almost all aspects of the original γ-Fe2O3 nanoparticles, such as shape, size, and monodispersity, were maintained in the produced Fe3O4 nanoparticles.
Keywords: Magnetite; Maghemite; Nanoparticles; Phase transformation; Reduction;