Journal of Colloid And Interface Science (v.369, #1)
Hybrid polymer/nanoparticle solar cells: Preparation, principles and challenges
by Brian R. Saunders (pp. 1-15).
Display Omitted► Hybrid polymer/nanoparticle solar cell efficiency limited by morphology and ligands. ► These solar cells are colloidal in nature. ► Uncontrolled aggregation major cause of low efficiencies. ► Triggered aggregation and self-assembly may provide improvement. ► Materials for widespread deployment of future solar cells discussed.Hybrid polymer/nanoparticle solar cells have a light harvesting layer composed of semiconducting inorganic nanoparticles and a semiconducting conjugated polymer. They have potential to give high power conversion efficiencies (PCE). However, the PCE values reported for these solar cells are not currently as high as anticipated. This article reviews the main methods currently used for preparing hybrid polymer/nanoparticle solar cells from the colloid perspective. PCE data for the period of 2005–2011 are presented for hybrid polymer/nanoparticle solar cells and compared to those from polymer/fullerene cells. The key reasons for the relatively low PCE values for hybrid polymer/nanoparticle solar cells are uncontrolled aggregation and residual insulating ligands at the nanoparticle surface. Two hybrid polymer/nanoparticle systems studied at Manchester are considered in which the onset of aggregation and its affect on composite film morphology were studied from the colloidal perspective. It is concluded that step-change approaches are required to increase the PCEs of hybrid polymer/nanoparticle solar cells and move them toward the 10% value required for widespread commercialisation. A range of nanoparticles that have potential for application in possible longer term terawatt solar energy production are discussed.
Keywords: Hybrid polymer/nanoparticle solar cells; Power conversion efficiency; PbS; ZnO; Polymer solar cells; Triggered aggregation
Deposition mechanisms of TiO2 nanoparticles in a parallel plate system
by Indranil Chowdhury; Sharon L. Walker (pp. 16-22).
Display Omitted► Development of a real-time visualization method for nanoparticle deposition studies. ► A combination of DLVO and non-DLVO-type forces will control deposition. ► Decreasing flowrate and reduction in drag force leads to greater deposition. ► Theoretical approximations indicate that gravitational forces play a significant role.In this study, a microscope-based technique was utilized to understand the fundamental mechanisms involved in deposition of TiO2 nanoparticles (TNPs). Transport and deposition studies were conducted in a parallel plate (PP) flow chamber with TNP labeled with fluorescein isothiocyanate (FITC) for visualization. Attachment of FITC-labeled TNPs on surfaces is a function of a combination of parameters, including ionic strength (IS), pH and flowrate. Significantly higher deposition rates were observed at pH 5 versus pH 7. This is attributed to the conditions being chemically favorable for deposition at pH 5 as compared to pH 7, as predicted by DLVO theory. Additionally, deposition rates at pH 5 were reduced with IS below 10mM due to the decrease in range of electrostatic attractive forces. Above 10mM, aggregate size increased, resulting in higher deposition rates. At pH 7, no deposition was observed below 10mM and above this concentration, deposition increased with IS. The impact of flowrate was also observed, with decreasing flowrate leading to greater deposition due to the reduction in drag force acting on the aggregate (regardless of pH). Comparisons between experimental and theoretical approximations indicate that non-DLVO type forces also play a significant role. This combination of observations suggest that the deposition of these model nanoparticles on glass surfaces was controlled by a combination of DLVO and non-DLVO-type forces, shear rate, aggregation state, and gravitational force acting on TNPs.
Keywords: Aggregation; Gravity; Deposition; Parallel plate chamber; Titanium dioxide
Controlling the density and site of attachment of gold nanoparticles onto the surface of carbon nanotubes
by Suresh Kumar; Inderpreet Kaur; Keya Dharamvir; Lalit M. Bharadwaj (pp. 23-27).
Display Omitted► Mild acid created functional groups preferably on the ends of carbon nanotubes. ► Strong acid created functional groups on the side walls of carbon nanotubes. ► Concentration of functional groups is directly proportional to oxidation time. ► Gold nanoparticles are bonded to ends and sidewalls of carbon nanotubes.A facile method for controlling the density and site of attachment of gold nanoparticles onto the surface of carbon nanotubes is demonstrated. Nitric acid based oxidation was carried out to create carboxylic groups exclusively at the ends of carbon nanotubes, whereas oxidation using a mixture of nitric and sulfuric acid with varied reaction time was carried out to control the population of carboxylic groups on the side walls of nanotubes. In turn, 4-aminothiophenol modified gold nanoparticles were covalently interfaced to these carboxylated multi-walled carbon nanotubes in the presence of a zero length cross-linker, 1-ethylene-3-(3-dimethylaminopropyl) carbodiimide. Raman spectroscopic results showed increase in height of disorder band with each of these successive steps, indicating the increase in degree of functionalization of the carbon nanotubes. Fourier transformed infrared spectroscopic analysis affirmed the functionalization of nanostructures and the formation of nanohybrid. Transmission electron and field emission scanning electron microscopic analysis ascertained the attachment of gold nanoparticles to the ends and side walls of the multi-walled carbon nanotubes. The new hybrid nanostructures may find applications in electronic, optoelectronic, and sensing devices.
Keywords: Carbon nanotubes; Gold nanoparticles; Nanohybrid
Hydrophilic/hydrophobic features of TiO2 nanoparticles as a function of crystal phase, surface area and coating, in relation to their potential toxicity in peripheral nervous system
by V. Bolis; C. Busco; M. Ciarletta; C. Distasi; J. Erriquez; I. Fenoglio; S. Livraghi; S. Morel (pp. 28-39).
Display Omitted► TiO2-NP hydrated surface hydrophilicity depends on crystal phase and surface coating. ► TiO2-NP surface charge is negative and similar for all polymorphs. ► TiO2-NP neurotoxicity depends on crystal phase (anatase–rutile>anatase≫rutile). ► Inorganic/organic surface coating does not protect against the TiO2-induced apoptosis. ► Optimized dispersion protocol allowed to perform viability DRG cells assays.The hydrophilic/hydrophobic properties of a variety of commercial TiO2 nanoparticles (NP), to be employed as inorganic filters in sunscreen lotions, were investigated both as such (dry powders) and dispersed in aqueous media. Water uptake and the related interaction energy have been determined by means of adsorption microcalorimetry of H2O vapor, whereas dispersion features in aqueous solutions were investigated by dynamic light scattering and electrokinetic measurements (zeta potential). The optimized dispersions in cell culture medium were employed to assess the possible in vitro neuro-toxicological effect on dorsal root ganglion (DRG) cells upon exposure to TiO2-NP, as a function of crystal phase, surface area and coating. All investigated materials, with the only exception of the uncoated rutile, were found to induce apoptosis on DRG cells; the inorganic/organic surface coating was found not to protect against the TiO2-induced apoptosis. The risk profile for DRG cells, which varies for the uncoated samples in the same sequence as the photo-catalytic activity of the different polymorphs: anatase–rutile>anatase≫rutile, was found not to be correlated with the surface hydrophilicity of the uncoated/coated specimens. Aggregates/agglomerates hydrodynamic diameter was comprised in the ∼200–400nm range, compatible with the internalization within DRG cells.
Keywords: TiO; 2; polymorphs; Nanoparticles; Water adsorption; Microcalorimetry; TiO; 2; dispersions; Hydrophilicity; Zeta potential; Hydrodynamic diameter; Viability cells assays; Dorsal root ganglion cells
High yield synthesis of intrinsic, doped and composites of nano-zinc oxide using novel combinatorial method
by Nahar Singh; Rashmi; Tarushee Ahuja; Sukhvir Singh; Renu Pasricha; D. Haranath (pp. 40-45).
Display Omitted► Combinatorial method to produce high yield nanomaterials and their composites has been developed. ► For the first time, a novel method of reduction of nitroarenes at neutral pH has been established. ► Tunability of photoluminescence from 390 to 615nm is useful for many display related applications.A novel synthesis of the production of luminescent zinc oxide (ZnO), either in its intrinsic, metal, non-metal-doped or composite forms with high yield has been developed by parallel iterative techniques, within a combinatorial library prepared by the reduction of nitroarenes. The reduction of nitroarenes by aluminium/zinc dusts in alkaline medium (pH 10±2) forms azoxy compounds, whereas in acidic medium (pH 4.9±0.2) forms phenyl hydroxylamine and zinc/aluminium dust gets oxidised into respective hydroxide. Here, we demonstrate the reduction of nitroarenes at neutral pH (7.0±0.2), which forms intrinsic as well as doped ZnO at 50±5°C using zinc dust alone or mixtures of salts of several transition and non-transition metals in presence of 1:10 ratio of solvent and water. Interestingly, it is observed that the photoluminescence emission could be tuned in a wide range from 390 to 615nm useful for many display related devices.
Keywords: Reduction of nitroarenes; Intrinsic and doped ZnO; Photoluminescence; Combinatorial method; Nanocomposites
Synthesis and self-assembly of amphiphilic gradient copolymer via RAFT emulsifier-free emulsion polymerization
by Yanjun Chen; Wen Luo; Yifeng Wang; Chong Sun; Mei Han; Chaocan Zhang (pp. 46-51).
Display Omitted► Amphiphilic gradient copolymer was obtained by RAFT emulsifier-free emulsion polymerization. ► Cosolvents adding into the system could inhibit the homopolymerization of AA. ► RAFT polymerization kinetics under different reaction conditions were discussed in detail. ► The1H NMR analysis proved the gradient structure of the copolymer. ► The gradient copolymer could form different micelles under different moisture content or pH in selective solvent by TEM.The amphiphilic gradient copolymers of 2,2,2-trifluoroethyl methacrylate (TFEMA) and acrylic acid (AA) have been synthesized by using amphiphilic RAFT agent via emulsifier-free emulsion polymerization with a starved feed method of adding TFEMA. Different cosolvents are added into polymerization system to inhibit AA’s homopolymerization of in aqueous phase. RAFT polymerization kinetics under different reaction conditions are discussed in detail.1H NMR results indicate that the obtained copolymer has a chain structure with AA segments gradually changing to TFEMA segments. The copolymer latexes exhibit good pH stability (pH value from 5 to 14) and Ca2+ stability. The self-assembly behavior of gradient copolymers in selective solvents are observed and studied by transmission electron microscopy. All the copolymers can form spherical micelles, but the homogeneity and size of micelles are different.
Keywords: Amphiphilic gradient copolymer; RAFT emulsifier-free emulsion polymerization; Self-assembly
Synthesis of zinc oxide-encapsulated poly(methyl methacrylate)–chitosan core–shell hybrid particles and their electrochemical property
by Chayannan Petchthanasombat; Tinnakorn Tiensing; Panya Sunintaboon (pp. 52-57).
Display Omitted► PMMA–CS/ZnO hybrid particles were prepared by soap-free emulsion polymerization. ► Effects of polymerization time and amount of ZnO added were investigated. ► Formation of PMMA–CS/ZnO hybrids was confirmed by TGA and TEM. ► The PMMA–CS/ZnO hybrid latexes possessed high positive surface charges (40–51mV). ► Electrochemical property of PMMA–CS/ZnO electrode was traced by cyclic voltammetry.The synthesis of hybrid materials possessing zinc oxide nanoparticles encapsulated in core–shell polymer particles having poly(methyl methacrylate) core and chitosan shell (PMMA–CS/ZnO) was carried out via an emulsifier-free emulsion polymerization. The ZnO nanoparticles modified by 3-(trimethoxysilyl)propyl methacrylate (TPMZnO) were first prepared before being charged to the polymerization system. The effects of polymerization time (from 2h to 6h) and the amount of TPMZnO added (0.018g, 0.020g, and 0.030g) were studied. It was found that the polymerization time of 5h yielded colloidally stable hybrid latex with% MMA conversion up to 90%. Moreover, the increase in the amount of TPMZnO resulted in a decrease in% MMA conversion from 90% to 80%. It was also found from TGA analysis that the amount of TPMZnO added affected the percentage of TPMZnO encapsulation. PMMA–CS/ZnO particles with the size ranging from 173 to 245nm were observed by TEM. In addition, the PMMA–CS/ZnO hybrid latexes possessed high positive charges in the range of 40–51mV. The electrochemical property of the electrodes fabricated from PMMA–CS/ZnO nanoparticles was illustrated by cyclic voltammetry.
Keywords: Abbreviations; PMMA; poly(methyl methacrylate); MMA; methyl methacylate; CS; chitosan; ZnO; zinc oxide; TPM; 3-(trimethoxysilyl)propyl methacrylate; TGA; thermogravimetric analysis; TEM; transmission electron microscopy; eV; electron volt; meV; millielectron volt; UV; ultraviolet; DNA; deoxyribonucleic acid; (Zn(AcO); 2; ·2H; 2; O; zinc acetate dihydrate; TBHP; tert; -butyl hydroperoxide; kDa; kilodalton; EtOH; ethanol; h; hour; UV–VIS; ultraviolet–visible; nm; nanometer; D; diameter; XRD; X-ray diffraction; kV; kilovolt; WE; working electrode; RE; reference electrode; CE; counter electrode; V; volt; mV; millivolt; CVs; cyclic voltammograms; mM; millimolar; E; p; electrode potential; I; p; current potential; FTO; fluorine doped tin oxideChitosan; ZnO nanoparticle; Core–shell; Electrochemical; Hybrid
Synthesis of porphyrinoids with silane anchors and their covalent self-assembling and metallation on solid surface
by Essi Sariola-Leikas; Matti Hietala; Alexey Veselov; Oleg Okhotnikov; Sergei L. Semjonov; Nikolai V. Tkachenko; Helge Lemmetyinen; Alexander Efimov (pp. 58-70).
Display Omitted► Porphyrinoids with silane anchor prepared with high yield by hydrosilylation. ► Reduction side reaction suppressed by proper choice of catalyst. ► Compounds are stable yet reactive, isolated in pure form, have good shelf life. ► Chromophores form SAM on oxide surfaces and optical fibers with ease in one step. ► Method can be applied to virtually any chromophore with hydroxy groups.We have synthesized a set of porphyrin and phthalocyanine compounds with two different silane anchors. Syntheses of the anchor-substituted chromophores have been carried out via hydrosilylation of alkene derivatives, catalyzed by platinum complexes. The reduction side-process was suppressed using specific anchor/catalyst pairs, and the silane-containing compounds were successfully isolated from hydrogenated by-products in pure form with good yields. The target porphyrinoids having stable reactive silane anchors possess the ability to self-assemble on metal oxides and quartz surfaces and optical fibers. Covalent attachment is done in one-step, which makes the bonding process fast and easy. Immobilized chromophores were further converted by on-surface reactions into Zn(II) and Mg(II) metal complexes. The metallation time was found to be as fast as 1min for Zn ion. Bonding densities calculated from the absorbances of the deposited layers give rough estimations for packing of the molecules on various substrates and evidence for monomolecular layers formation.
Keywords: Hydrosilylation; Metallation; Photonic crystal fiber; Phthalocyanine; Porphyrin; Self-assembled monolayer; Silane anchor
Synthesis of mesoporous silicas in alkaline and acidic media using the systems cetyltrimethylammonium tosylate (CTAT)–Pluronic F127 triblock copolymer and CTAT–Pluronic F68 triblock copolymer as templates
by Maximiliano Brigante; Pablo C. Schulz (pp. 71-81).
Display Omitted► Mesoporous silica materials were synthesized in alkaline and acidic media. ► Bicontinous materials are obtained in alkaline synthesis. ► Monolithic materials are obtained in acidic synthesis. ► Silicas synthesized by using cetyltrimethylammonium tosylate as template show bimodal pore distribution. ► Systems having the block copolymer show small and nearly round pores.Mesoporous silica materials were synthesized in alkaline and acidic media, using cetyltrimethylammonium tosylate (CTAT), Pluronic triblock copolymers F127 and F68, and mixtures of CTAT with each copolymer in order to investigate the effects of pH, surfactant concentration, and CTAT/triblock copolymer molar ratios on the morphology and texture of the synthesized materials. The results show that the kind of mesoporous materials and their pore size can be tuned by changing not only the pH but also the proportion of components and the nature of the copolymer. In alkaline synthesis, microscopic bicontinuous materials are obtained, which are composed by nanoscopic plate-like particles having slit-shaped pores. In acidic synthesis, on the contrary, monolithic silicas are obtained. These materials are also composed by nanoscopic plate-like particles having slit-shaped pores, although in some cases, the microscopic structures are formed by fused spherical particles. The inclusion of the triblock copolymer in the template composition causes a transformation from a bimodal to a monomodal pore size distribution, leading to small and nearly round pores which are probably formed by copolymer or copolymer-CTAT mixed micelles. The differences between the systems synthesized by CTAT–Pluronic F127 and CTAT–Pluronic F68 are explained on the basis of the different interactions between each copolymer and CTAT.
Keywords: Mesoporous silica materials; Synthesis; Cetyltrimethylammonium tosylate; Pluronic F127; Pluronic F68; Triblock copolymer–CTAT interactions
Synthesis of pH and temperature sensitive, core–shell nano/microgels, by one pot, soap-free emulsion polymerization
by A. Serrano-Medina; J.M. Cornejo-Bravo; A. Licea-Claveríe (pp. 82-90).
Display Omitted► We synthesize temperature and pH sensitive core–shell nanogels. ► One pot, soap-free emulsion polymerization was used. ► The shell consists of polyethylene glycol chains. ► The core contains N-isopropylacrylamide and 2-methacryloyloxybenzoic acid. ► Labile divinyl crosslinker produces smaller nanogels than dimethacrylate crosslinker.The synthesis and properties of thermal/pH-sensitive core–shell copolymer nano/microgels were investigated. The crosslinked core consisted of N-isopropylacrylamide (NIPAAm) while the shell was stabilized by poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 2-methacryloyloxybenzoic acid (2MBA) using a “one pot” soapless emulsion polymerization method. Monodisperse particles were produced with average hydrodynamic diameters ranging from 40 to 880nm, as determined by dynamic light scattering (DLS) in water at 25°C, depending on the synthetic recipe used. The influence of PEGMA and 2MBA content on size and temperature transition at different pH values was studied. Zeta potential measurements and acid–base titration studies demonstrated almost complete incorporation of acid comonomer (2MBA) into the nano/microgels. Two different crosslinkers, a stable and an acid labile, were compared. The crosslinker used has a major influence on the size and charge density of the nano/microgels produced. Microscopic studies confirmed the core–shell morphology of the nano/microgels.
Keywords: Nanogels; Sensitive polymers; Poly(; N; -isopropylacrylamide); Emulsion polymerization
Deposition of continuous platinum shells on gold nanoparticles by chemical precipitation
by R.K. Roy; J.I. Njagi; B. Farrell; I. Halaciuga; M. Lopez; D.V. Goia (pp. 91-95).
Display Omitted► Continuous thin Pt shells were deposited on Au nanocrystals by chemical precipitation. ► The continuous deposition of Pt was achieved by controlling the kinetics of Pt(IV) reduction. ► The Pt shell exhibits mass specific activities comparable to the bulk metal.Continuous platinum shells consisting of ∼5 atomic layers were deposited onto preformed gold seeds in aqueous medium by reducing hexachloroplatinic acid with ascorbic acid. By controlling the reduction kinetics of Pt(IV) species and the properties of the substrate, it was possible to ensure a slow and controlled deposition of platinum atoms onto the gold cores. Electrochemical evaluations revealed the presence of a compact platinum shell. The mass specific oxygen reduction activity of platinum in the AuPt core–shell nanoparticles was found to be four times higher than that of platinum black and comparable to that of polycrystalline bulk metal.
Keywords: Nanocrystals; Platinum; Epitaxial deposition; Fuel cell
Glycine passivated Fe3O4 nanoparticles for thermal therapy
by K.C. Barick; P.A. Hassan (pp. 96-102).
Display Omitted► Biocompatible, water dispersible glycine passivated Fe3O4 nanoparticles. ► Carboxylate group is the preferable site for chemisorption of glycine with Fe3O4. ► Excellent heating ability under AC magnetic field shows its use in thermal therapy. ► Amine groups on Fe3O4 surface can be explored for conjugation of biomolecules.We demonstrate a single-step facile approach for the synthesis of glycine (amino acid) passivated Fe3O4 magnetic nanoparticles (GMNPs) using soft chemical route. The surface passivation of Fe3O4 nanoparticles with glycine molecules was evident from infrared spectroscopy, thermal and elemental analyses, and light scattering measurements. These nanoparticles show better colloidal stability, good magnetization, excellent self-heating capacity under external AC magnetic field and cytocompatibility with cell lines. Further, the active functional groups (–NH2) present on the surface of Fe3O4 nanoparticles can be accessible for routine conjugation of biomolecules/biolabelling through well-developed bioconjugation chemistry. Specifically, a new colloidal glycine passivated biocompatible Fe3O4 nanoparticles with excellent specific absorption rate (SAR) have been fabricated, which can be used as an effective heating source for hyperthermia treatment of cancer (thermal therapy).
Keywords: Magnetic particles; Amino acid coating; Surface charge; Cytotoxicity; Hyperthermia
Enzymatically synthesized polyaniline film deposition studied by simultaneous open circuit potential and electrochemical quartz crystal microbalance measurements
by Norma Carrillo; Ulises León-Silva; Tatiana Avalos; M.E. Nicho; Sergio Serna; Felipe Castillon; Mario Farias; Rodolfo Cruz-Silva (pp. 103-110).
Display Omitted► Aniline enzymatic polymerization proceeds at remarkably low oxidation potential. ► A new method to monitor oxidoreductase enzymatic reactions is shown (OCP+QCM). ► PANI films were grown by in situ enzymatic polymerization and the mechanism was studied.The chemical and enzymatic deposition of polyaniline (PANI) films by in situ polymerization was studied and the resulting films were characterized. The film formation and polymerization processes were simultaneously monitored by the evolution of the open circuit potential and quartz-crystal microbalance measurements. Different substrates, such as Indium-Tin oxide electrodes and gold-coated quartz-crystal electrodes were used as substrates for PANI deposition. Electroactive PANI films were successfully deposited by in situ enzymatic polymerization at low oxidation potential. The electrogravimetric response of the enzymatically deposited PANI film was studied by cyclic voltammetry in monomer-free acidic medium. The morphology of the films was observed by scanning electron microscopy, revealing a granular structure in enzymatically deposited PANI. The PANI films were also characterized by thermogravimetric analysis, electrochemical impedance spectroscopy, and X-ray photoelectron and Fourier-transformed infrared spectroscopy. The simultaneous use of quartz crystal microbalance and open circuit potential is presented as a very useful technique to monitor enzymatic reactions involving oxidoreductases.
Keywords: Enzymatic polymerization; Open circuit potential; Quartz crystal microbalance; Conducting polymers
Application of supercritical CO2 and ionic liquids for the preparation of fluorinated nanocomposites
by Sébastien Livi; Jannick Duchet-Rumeau; Jean-François Gérard (pp. 111-116).
Display Omitted► Synthesis of new surfactants for polytetrafluoroethylene matrices. ► Combination of two elements of green chemistry: supercritical carbon dioxide and ionic liquids. ► Nanostructuring of ionic liquids in PTFE films. ► Improvement of nanocomposite mechanical properties.This work is focused on the tailoring of dispersions of layered silicates, such as MICA SOMASIF (ME-100) within a fluoride matrix (polytetrafluoroethylene) through two strategies: the physicochemical interactions between filler and matrix and the processing of materials. The interactions in these complex systems are modified by new environmentally friendly thermally stable surfactants. The ionic liquids used are based on alkyltriphenyl phosphonium and perfluorinated alkylpyridinium cations. The influences of the cation–anion combination and functionalization were investigated. The use of the supercritical carbon dioxide (ScCO2) as a solvent is relevant to generate structuring within the material based on ionic liquid phase separation. The tunability of ionic liquids and their combination with the supercritical carbon dioxide enables to design materials with optimized thermal and mechanical properties.
Keywords: Ionic liquid; Supercritical carbon dioxide; Morphology; Mechanical properties
A novel method for the templated synthesis of Ag2S hollow nanospheres in aqueous surfactant media
by Rajib Ghosh Chaudhuri; Santanu Paria (pp. 117-122).
Display Omitted► Ag2S hollow nanoparticles are synthesized using sulfur as a sacrificial core. ► There is a 67% enhancement in quantum yield with the hollow nanoparticles. ► This route can also be used to synthesize other hollow nanoparticles.Ag2S is an important direct semiconductor material that receives considerable research interest because of its low toxicity and high chemical stability. This work reports an easy and novel route for the synthesis of hollow Ag2S particles by a sacrificial core method in surfactant containing aqueous media. Sulfur is used as a sacrificial core in this method and removed by dissolving in carbon disulfide. Core sulfur particles were synthesized in situ by acid catalyzed reaction of sodium thiosulphate in aqueous surfactant media. The particles were characterized by using different instrumental techniques, showing 67% improved light emission capacity in terms of quantum yield compared to solid Ag2S particles. The same route is also suggested to prepare other nanoparticles.
Keywords: Core/shell; Hollow nanoparticles; Ag; 2; S; Quantum yield
Facile controlled synthesis and growth mechanisms of flower-like and tubular MnO2 nanostructures by microwave-assisted hydrothermal method
by Yongliang Li; Jiajun Wang; Yong Zhang; Mohammad Norouzi Banis; Jian Liu; Dongsheng Geng; Ruying Li; Xueliang Sun (pp. 123-128).
Display Omitted► MnO2 nanostructures were synthesized by a microwave-assisted hydrothermal method. ► Crystal phase and morphology can be controlled by adjusting reaction temperature. ► The formation mechanism of MnO2 nanotubes follows an “oriented attachment” process.Birnessite flower-like and α-type tubular MnO2 nanostructures were selectively synthesized through simple decomposition of KMnO4 under hydrochloric acid condition by controlling reaction temperature using a microwave-assisted hydrothermal method. The as-prepared samples were characterized in detail by various techniques including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform-infrared spectroscopy, and Raman scattering spectroscopy. While the growth of flower-like birnessite-MnO2 might follow a widely accepted Ostwald ripening process, we proposed a formation mechanism of the nanotubular α-MnO2 based on our evidence, which was assembly of nanorods through an “oriented attachment” process.
Keywords: Flower-like spheres; Nanotubes; Dissolution–crystallization; Oriented attachment
Morphological determination of face-centered-cubic metallic nanoparticles by X-ray diffraction
by Chi-Feng Lee; Chia-Lun Chang; Jing-Cyuan Yang; Hsiang-Yu Lai; Chun-Hua Chen (pp. 129-133).
Display Omitted► An X-ray diffraction analysis is explored for noble metal fcc nanoparticles. ► Four morphologies, that is, sphere, cube, decahedron, and icosahedron, are identifiable. ► Truncated and perfect strained particle models are created for Debye simulations.X-ray diffraction studies of face-centered-cubic metallic nanoparticles with different morphologies are discussed based on the experimental data and the calculation of the Debye equation with the truncated and perfect strain models. At least four basic morphologies frequently observed in face-centered-cubic metallic nanoparticles, namely sphere, cube, decahedron, and icosahedron, can be clearly distinguished from their characteristic integrated intensity ratios of the first two X-ray diffraction peaks, that is, (200) to (111).
Keywords: X-ray diffraction; Icosahedron; Decahedron; Nanoparticle
Understanding nanoparticle assembly: A simulation approach to SERS-active dimers
by Paul R. Mark; Laura Fabris (pp. 134-143).
Display Omitted► Effect of initial nanoparticle concentration on assembly. ► Nanoparticle assembly based on single and double addition for small systems. ► Surface coverage and nature of the linkers influence assembly. ► Maximized dimer formation can be achieved only considering charge effects. ► For systems modeled, pure formation of dimers is not achievable.We report herein on a model built to analyze and optimize nanoparticle (NP) dimer formation. The rationale for this work stems from our interest in building effective NP dimer-based tagging systems for surface enhanced Raman scattering (SERS)-based detection. This model takes into account the behavior of the NPs in solution and the molecules on their surface, to provide a coherent and physically constrained system. The kinetics of formation of dimers and larger assemblies are investigated on suspensions of varying concentrations through a coarse-grained ad hoc computer simulation based on a Molecular Dynamics-like approach. Several different effects are considered, including the behavior and interaction of surface molecules, the interactions between the latter and the NPs, and between NPs. The surface molecules are treated as rigid structures that can occupy specific binding sites. A Brownian model is used to both integrate the particle trajectory and provide random thermal forces. These systems show a NP concentration-dependent behavior with respect to the formation of dimers versus larger assemblies over the timescale of the simulation. The simulations also indicate that these systems form low-density aggregates as opposed to the close packed formations reported previously. A dependence on the properties and the concentration of the linkers is also demonstrated.
Keywords: Dimer; Assembly; Bottom-up synthesis; Simulation; Force; Kinetics
A general method for the synthesis of monodisperse hollow inorganic–organic hybrid microspheres with interior functionalized poly(methacrylic acid) shells
by Bin Liu; Enwei Yan; Xu Zhang; Xinlin Yang; Feng Bai (pp. 144-153).
Display Omitted► Synthesis of hollow inorganic/PMAA hybrid microspheres via a two-step reaction. ► The hollow structure formed via a capillary force and the competitive H-bond interaction. ► Facile control the spherical shape and the thickness of the shell-layer.Hollow inorganic–organic hybrid microspheres, such as silica, titania, and zirconia, with interior poly(methacrylic acid) (PMAA) functionalized shell were synthesized by a general method containing a two-stage reaction. The hollow inorganic shell-layer with interior polymeric component was formed over the PMAA template during the second-stage controlled hydrolysis of inorganic precursors together with disintegration of PMAA cores and adhering to the interior wall of the silica during the drying process due to the capillary force as well as the competitive hydrogen bond interaction. In this process, PMAA microspheres were prepared by distillation precipitation polymerization of methacrylic acid (MAA) in acetonitrile as the first-stage reaction. The present work elaborately investigated the effects of the reaction conditions, including the amount of the tetraethyl orthosilicate (TEOS) precursors and the amount of ammonium hydroxide catalyst on the morphology and structure of the resultant hollow composite microspheres, which were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectra (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption.
Keywords: Hollow microsphere; Inorganic-polymeric hybrid microsphere; Interior polymer functionalized hollow inorganic microsphere
Structural characterisation of alkyl amine-capped zinc sulphide nanoparticles
by Gabriele Kremser; Thomas Rath; Birgit Kunert; Michael Edler; Gerhard Fritz-Popovski; Roland Resel; Ilse Letofsky-Papst; Werner Grogger; Gregor Trimmel (pp. 154-159).
Display Omitted► Combined X-ray and light scattering study was performed on ZnS nanoparticles. ► Ligands with different steric properties, dodecyl- and oleylamine, are compared. ► Nanoparticles exhibit sizes of 3–5nm. ► Thickness of the ligand shell is about 1.9nm.Nanoparticles capped with amine ligands with different steric properties, dodecylamine and oleylamine, respectively, are investigated in the solid state as well as in solution. A combined X-ray diffraction, small angle X-ray scattering and electron microscopy investigation showed that the nanoparticles exhibit the sphalerite modification of ZnS as crystal phase with a diameter of 3–5nm. A close packing of the monocrystalline nanoparticles in the solid state is observed. However, in the dodecylamine sample, besides spherical particles, a fraction of the nanoparticles is elongated. The nanoparticles are readily resoluble in apolar solvents like hexane. Dynamic light scattering (DLS) and SAXS investigations of the solutions reveal that the nanoparticles are dissolved as singular particles. In the case of oleylamine-capped ZnS, a defined core–shell structure with a ZnS core with a diameter of 4nm and an organic shell with a thickness of approximately 2nm have been found. Dodecylamine-capped nanoparticles slightly tend to form agglomerates with a diameter of approximately 40nm.
Keywords: Zinc sulphide; SAXS; Electron microscopy; Nanoparticles; Ligand shell; Oleylamine
Synthesis, characterization and catalytic behavior of functionalized mesoporous SBA-15 with various organo-silanes
by Alime Çıtak; Beyhan Erdem; Sezer Erdem; Ramis Mustafa Öksüzoğlu (pp. 160-163).
Display Omitted► We synthesize mesoporous silica SBA-15 by one-step method and functionalize. ► The anchoring of functional groups on SBA-15 is proved by XRD, FT-IR, BET and BJH. ► Catalytic activity order is associated with the surface area and pore size distribution.Mesoporous silica SBA-15 has been synthesized and functionalized by one-step synthesis method to widen their various application possibilities. In this study, phenyltrimethoxysilane (PTMS), 3-mercaptopropyltrimethoxysilane (MPTMS) and trimethoxypropylsilane (TMPS) were used as silane precursors for the functionalization, and after treated with HCl solution, their catalytic activities were evaluated in the lactic acid–methanol esterification. The presence of anchoring of functional groups on SBA-15 was proved by XRD, FT-IR, BET surface area and pore size distributions. Good catalytic activity was observed especially for SBA-15–SO3H–MPTMS, and the catalytic activity order was determined as follows: SBA-15–SO3H–MPTMS>SBA-15–TMPS>SBA-15–PTMS, which is directly associated with the surface area, pore size and pore volume. As compared with homogeneous catalyst, SBA-15–SO3H–MPTMS heterogeneous catalyst shows remarkable performance, such as separation, recovery and reusability.
Keywords: SBA-15; Esterification; Functionalization; Mesoporous silica
Preparation of rhenium nanoparticles via pulsed-laser decomposition and catalytic studies
by Yuan Yi Chong; Wai Yong Chow; Wai Yip Fan (pp. 164-169).
Display Omitted► Re nanoparticles are prepared by laser decomposition of NH4ReO4 or Re2(CO)10. ► MPA-capped Re nanoparticles catalyze isomerization of 10-undecen-1-ol at 200°C. ► Graphite-coated Re nanoparticles are prepared via surface graphitization of PPh3.Rhenium (Re) nanoparticles have been synthesized by pulsed-laser decomposition of ammonium perrhenate (NH4ReO4) or dirhenium decacarbonyl (Re2(CO)10) in the presence of 3-mercaptopropionic acid (MPA) as capping agent, in both aqueous and organic media. Preliminary studies showed that the MPA-capped Re nanoparticles are capable of catalyzing the isomerization of 10-undecen-1-ol to internal alkenols via long chain migration of the CC double bond at ca. 200°C. A one-pot synthesis of graphite-coated Re nanoparticles has also been achieved by pulsed-laser decomposition of Re2(CO)10, due to photo-induced catalytic graphitization of the phenyl groups of PPh3 on the surface of rhenium nanoparticles.
Keywords: Rhenium; Nanoparticles; Graphite-coated; Catalysis; Isomerization; C; C migration
Polymer particles with dendrimer@SiO2–Ag hierarchical shell and their application in catalytic column
by Gaofei Dang; Yan Shi; Zhifeng Fu; Wantai Yang (pp. 170-178).
Display Omitted► Polymer particles with dendrimer@SiO2–Ag hierarchical shell were prepared. ► Hierarchical particles packed in the catalytic column for the reduction of 4-NP. ► Under column pressure SiO2 plays a better role in immobilization of Ag than PAMAM. ► Packing catalytic nanoparticles in column improves the efficiency. ► Reduce tedious separation processes in catalytic reaction.Polymer particles with dendrimer@SiO2–Ag hierarchical shell were prepared, and their application in the catalytic column for the reduction of 4-nitrophenol (4-NP) was also investigated. The PS microspheres with the carboxyl group were used as the supports for the immobilization of dendrimer@SiO2–Ag shell. The polyamidoamine (PAMAM) dendrimer was grafted on the surface of PS microsphere through repetitive Michael addition reaction of methyl acrylate (MA) and amidation of the obtained esters with a large excess of ethylenediamine (EDA) successively. The silver nanoparticles formed inside the PAMAM shell. Then, the silver nanoparticles, which were used as center of nucleation, were coated with SiO2 shell through improved Stöber method. Moreover, the more silver nanoparticles were dispersed on the surface of SiO2 shell. The contents of silver element were measured using inductively coupled plasma (ICP-MS). The obtained PS@PAMAM@SiO2–Ag nanoparticles were packed in stainless steel column, which has been used effectively for the catalytic reduction of 4-NP. Under column pressures, the rigid SiO2 shell plays a better role in immobilization of silver nanoparticles than the soft PAMAM shell. This technique for packing catalytic nanoparticles in column improves the efficiency of application with metal catalysts as well as reduces the tedious separation processes in catalytic reaction.
Keywords: Hierarchical nanoparticles; Polyamidoamine dendrimer; Dendrimer-metal; Catalytic column; SiO; 2; –Ag nanocatalyst
Large scale fabrication of highly monodispersed rattle-type TiO2@void@SiO2 spheres via synthesis-cum-organization process
by Liangzhuan Wu; Yuan Yu; Yuan Zhang; Yuzhen Li; Yang Zhang; Jinfang Zhi (pp. 179-183).
Display Omitted► One-pot synthetic strategy for inorganic architected nanostructure was developed. ► One-kilogram yield of the sample can be achieved one time using this synthetic strategy. ► The synthetic method is analogous to organic reaction used in total synthesis.Architected nanostructures with interior space have attracted enormous attention due to both their esthetic beauty and their potential applications. It is a current dream to develop a template-free, one-pot and low-temperature synthetic routes for hetero-architecture in liquid media. In this manuscript, we develop a kind of template-free, low-temperature, and one-pot total synthetic strategy for synthesis of inorganic multi-component hetero-architecture. This synthetic strategy analogous to standard organic reactions used in total synthesis is an important breakthrough in inorganic chemical synthesis. We can achieve 1kilogram (kg) yield of the TiO2@void@SiO2 core–shell sphere one time by using this synthetic strategy, which may lead to practical applications of the sample. By embodying the new reaction and concept into future investigation, a more mature research field in synthetic architecture of nanomaterials can be anticipated.
Keywords: Monodispersed spheres; Synthesis-cum-organization; Emulsion; Titanium
Time-resolved small angle X-ray scattering study of sol–gel precursor solutions of lead zirconate titanate and zirconia
by Tomasz M. Stawski; Rogier Besselink; Sjoerd A. Veldhuis; Hessel L. Castricum; Dave H.A. Blank; Johan E. ten Elshof (pp. 184-192).
Display Omitted► Evolution of nanostructure in PZT and zirconia sols studied by SAXS. ► Similar cylindrical structural motifs observed in PZT and zirconia sols. ► Cylindrical motifs are probably stacked zirconia-based tetramers. ► No scattering contributions from Pb and Ti observed in PZT sols.The evolution of nanostructure in sol–gel derived lead zirconate titanate (PZT) and zirconia precursor sols at different hydrolysis ratios was investigated by small angle X-ray scattering (SAXS). The shape of the clusters in the zirconia sol could be described by the length-polydisperse cylindrical form factor. The zirconia-based clusters were characterized by a cross-sectional radius, r0, of 0.28nm and a practically monodisperse length of ca. 1.85nm. These clusters were probably constructed of zirconia-related tetrameric building blocks. Similar cylindrical structural motifs were observed in PZT precursor sols with [H2O]/[Zr+Ti]=9.26 and 27.6, but the polydispersity in length was much higher. Clear scattering contributions from Ti and Pb centers were not detected, which was interpreted in terms of a homogeneous distribution of unbound lead ions in solution and the relatively low scattering intensity from any Ti-based clusters or oligomers that may have been present in the sols.
Keywords: Lead zirconate titanate; Zirconia; PZT; Sol–gel; SAXS
Interactions between surfactants and silver nanoparticles of varying charge
by J. Hedberg; M. Lundin; T. Lowe; E. Blomberg; S. Wold; I. Odnevall Wallinder (pp. 193-201).
Display Omitted► Silver nanoparticles (Ag NP) of various charge interact with charged and uncharged surfactants. ► Electrostatic interactions of oppositely charged Ag NPs and surfactants produce large changes in surface charge above CMC. ► Cooperative adsorption plays an important role in charge reversal of Ag NPs in the presence of surfactants.The interaction between silver nanoparticles (Ag NPs) of different surface charge and surfactants relevant to the laundry cycle has been investigated to understand changes in speciation, both in and during transport from the washing machine. Ag NPs were synthesized to exhibit either a positive or a negative surface charge in solution conditions relevant for the laundry cycle (pH 10 and pH 7). These particles were characterized in terms of size and surface charge and compared to commercially laser ablated Ag NPs. The surfactants included anionic sodium dodecylbenzenesulfonate (LAS), cationic dodecyltrimethylammoniumchloride (DTAC) and nonionic Berol 266 (Berol). Surfactant–Ag NP interactions were studied by means of dynamic light scattering, Raman spectroscopy, zeta potential, and Quartz Crystal Microbalance. Mixed bilayers of CTAB and LAS were formed through a co-operative adsorption process on positively charged Ag NPs with pre-adsorbed CTAB, resulting in charge reversal from positive to negative zeta potentials. Adsorption of DTAC on negatively charged synthesized Ag NPs and negatively charged commercial Ag NPs resulted in bilayer formation and charge reversal. Weak interactions were observed for nonionic Berol with all Ag NPs via hydrophobic interactions, which resulted in decreased zeta potentials for Berol concentrations above its critical micelle concentration. Differences in particle size were essentially not affected by surfactant adsorption, as the surfactant layer thicknesses did not exceed more than a few nanometers. The surfactant interaction with the Ag NP surface was shown to be reversible, an observation of particular importance for hazard and environmental risk assessments.
Keywords: Silver nanoparticles; Laundry detergents; Surfactants; Surface Enhanced Raman Spectroscopy; Zeta potential; Dynamic light scattering
Pickering emulsions stabilized by cellulose nanocrystals grafted with thermo-responsive polymer brushes
by Justin O. Zoppe; Richard A. Venditti; Orlando J. Rojas (pp. 202-209).
Display Omitted► We produced Pickering emulsions with thermo-responsive cellulose nanocrystals. ► The nanocrystals align at the oil–water interface. ► Obtained O/W emulsions are very stable (+6months’ stability). ► Heating above the LCST of thermo-responsive brushes triggers emulsion breaking. ► Thermal responsiveness can be tuned by changes in ionic strength.Cellulose nanocrystals (CNCs) from ramie fibers are studied as stabilizers of oil-in-water emulsions. The phase behavior of heptane and water systems is studied, and emulsions stabilized by CNCs are analyzed by using drop sizing (light scattering) and optical, scanning, and freeze-fracture electron microscopies. Water-continuous Pickering emulsions are produced with cellulose nanocrystals (0.05–0.5wt%) grafted with thermo-responsive poly(NIPAM) brushes (poly(NIPAM)-g-CNCs). They are observed to be stable during the time of observation of 4months. In contrast, unmodified CNCs are unable to stabilize heptane-in-water emulsions. After emulsification, poly(NIPAM)-g-CNCs are observed to form aligned, layered structures at the oil–water interface. The emulsions stabilized by poly(NIPAM)-g-CNCs break after heating at a temperature above the LCST of poly(NIPAM), which is taken as indication of the temperature responsiveness of the brushes installed on the particles and thus the responsiveness of the Pickering emulsions. This phenomenon is further elucidated via rheological measurements, in which viscosities of the Pickering emulsions increase on approach of the low critical solution temperature of poly(NIPAM). The effect of temperature can be counterbalanced with the addition of salt which is explained by the reduction of electrostatic and steric interactions of poly(NIPAM)-g-CNCs at the oil–water interface.
Keywords: Pickering emulsions; Oil-in-water emulsions; Cellulose nanoparticles; Cellulose nanocrystals; Thermo-responsive emulsions; Poly(N-isopropylacrylamide); LCST; Grafts; Surface-initiated single-electron transfer living radical polymerization
pH dependent stability of aqueous suspensions of graphene with adsorbed weakly ionisable cationic polyelectrolyte
by Angus Griffith; Shannon M. Notley (pp. 210-215).
Display Omitted► Polymer stabilised graphene nanoparticles produced. ► Aqueous graphene suspension is stable over wide range of solution conditions. ► Molecular weight dependency of stabilisation mechanism. ► Electrostatic and electrosteric stabilisation possible.Stable graphene suspensions were prepared through ultrasonic exfoliation followed by surface modification with the cationic polyelectrolyte poly(ethyleneimine) (PEI). The stability of the suspensions was found to be dependent upon the pH of the solution and the molecular weight of the PEI adsorbed. For the graphene sheets with adsorbed PEI with a molecular weigh of 600Da, the particles were stabilised through an increased electrostatic repulsion at low pH inferred from in an increase in the measured zeta potential of the particles. However, the graphene with higher molecular weight PEI (70kDa) was stable over a comparatively larger pH range through a combination of electrostatic repulsion at low pH and steric repulsion at elevated pH. Thus, solution conditions allowing the control of the colloidal sized graphene particles can be easily tuned through judicious management of solution conditions as well as polymer layer properties.
Keywords: Graphene; Sonication; Steric stabilisation; Stability ratio; Polyethylene imine
Investigation of the physicochemical aspects from natural kaolin to Al-MCM-41 mesoporous materials
by Chunfang Du; Huaming Yang (pp. 216-222).
Display Omitted► Mesoporous Al-MCM-41 with surface area of 1041m2/g is synthesized from kaolin. ► Pretreatment for kaolin is essential to the successful production of Al-MCM-41. ► A general mechanism for the formation of Al-MCM-41 from kaolin is proposed.Aluminum-containing hexagonally ordered mesoporous silica Al-MCM-41 was synthesized by hydrothermal treatment of leached products produced by pre-grinding and subsequent acid leaching of natural kaolin, without addition of silica or aluminum regents. The resulting Al-MCM-41 had a high surface area of 1041m2/g, a pore volume of 0.97mL/g, and an average pore diameter of 3.7nm with narrow pore size distribution centered at 2.7nm. During the synthesis process of Al-MCM-41 from natural kaolin, the evolutions of chemical environments for Si and Al atoms should be emphasized. Wide angle X-ray diffraction (WAXRD), high-resolution transmission electron micrographs (HRTEMs), solid-state magic-angle-spinning nuclear magnetic resonance (MAS NMR), Fourier transform infrared spectroscopy (FT-IR) were used to trace the variations of chemical structures. Pretreatment of grinding and subsequent acid leaching acted as an important role in the whole synthesis process. NMR spectroscopy showed that Q3 structure (Si(SiO)3(OH)), condensed Q4 framework structure (Si(SiO)4), also the octahedral and tetrahedral Al existed in the leached sample and Al-MCM-41, with higher chemical contents of Q4 structure and the octahedral Al in final product Al-MCM-41 than those in the leached sample. A possible mechanism for the formation of Al-MCM-41 from natural kaolin was suggested.
Keywords: Al-MCM-41; Kaolin; Pretreatment; Hydrothermal treatment; Structural evolution
Cationic polyvinylamine binding to anionic microgels yields kinetically controlled structures
by Quan Wen; Andrew M. Vincelli; Robert Pelton (pp. 223-230).
Display Omitted► Anionic microgels irreversibly bind cationic polyvinylamine. ► Binding capacity increases with PVAm concentration. ► Relative rates of attachment and rearrangement determine capacity. ► Coated microgel composition is determined by mixing conditions.Polyvinylamine (PVAm) binding (absorption and adsorption) to carboxylated microgels gave colloidally stable, cationic microgels that can be centrifuged, washed, freeze dried, and redispersed in water with no loss in colloidal stability. Because both PVAm and the carboxylated microgels are pH sensitive, changes in microgel swelling and electrophoretic mobility in response to pH change can be positive or negative depending upon pH and the PVAm content of the microgels. For a given PVAm molecular weight, the steady-state saturated mass fraction of bound PVAm in the microgels varied by a factor of four in our experiments. We proposed that the PVAm content at saturation was controlled by the relative rates of the initial attachment of PVAm chains versus the rate of attached chain spreading on and into the microgel structure. This explanation was further supported by a series of quartz crystal microbalance measurements.Finally, PVAm binding to two types of PNIPAM microgels shows general features recently reported for other polyelectrolyte types. Specifically: (1) for surface localized anionic charges on the microgels, the mass fraction of bound PVAm increased with PVAm molecular weight and vice versa; (2) in virtually all conditions, the quantity of adsorbed cationic ammonium groups was much greater than the carboxylate content of the microgel; and (3) sodium chloride additions lowered the mass fraction of bound PVAm.
Keywords: Microgels; Polyvinylamine; Polyelectrolyte complexes; QCM; Electrokinetics; Microgel adsorption; Microgel swelling; Microgel charge distribution; Microgel binding isotherms; Microgel colloidal stability
Thermo-responsive Hercosett/Poly(N-isopropylacrylamide) films: A new, fast, optically responsive coating
by Jing Wang; Alessandra Sutti; Xungai Wang; Tong Lin (pp. 231-237).
Display Omitted► A new smart composite film was prepared using a cationic resin and thermo-responsive nanoparticles. ► The composite film showed impressive thermo-responsiveness with morphological and optical changes. ► The composite film showed very high response speed around the critical transition temperature. ► “Smart substrates” were prepared for optically triggered actuation/sensing.Poly(N-isopropylacrylamide) (PNIPAM) is a common thermo-responsive, water-soluble polymer, while Hercosett is a cationic resin commonly employed in the paper industry. In this paper, Hercosett™ and poly(N-isopropylacrylamide) (PNIPAM) nanoparticles were used to prepare composite films that show thermo-responsive behavior and swelling–shrinking properties in water. First, size-controlled PNIPAM hydrogel nanoparticles were synthesized. These were then embedded within a matrix of the cationic resin Kymene 577H by film casting. The distribution of nanoparticles in the resin film was investigated. The thermo-responsive properties of the as-synthesized PNIPAM hydrogel nanoparticles and of the composite films were characterized together with the repeatability of the swelling–shrinking cycles. The presence of nanoparticles endowed the film with highly enhanced water retention (in comparison with resin-only films) and, most importantly, thermo-responsiveness. A very fast optical and morphological response was in fact observed. Due to the dual (optical and morphological) response, this new system is suitable for applications in optical or morphological actuation and gating.
Keywords: Poly(N-isopropylacrylamide); Hydrogel; Hercosett; Thermo-responsive; Film; Optical actuator
Hydrotropic salt promotes anionic surfactant self-assembly into vesicles and ultralong fibers
by Yiyang Lin; Yan Qiao; Xinhao Cheng; Yun Yan; Zhibo Li; Jianbin Huang (pp. 238-244).
Display Omitted► A hydrotropic salt promotes SDBS self-assembly into unilamellar and multilamellar vesicles. ► These multilamellar vesicles can transform into ultralong fibers. ► These ultralong surfactant fibers can be separated from surfactant solutions.Molecular self-assembly has become a versatile approach to create complex and functional nanoarchitectures. In this work, the self-assembly behavior of an anionic surfactant (sodium dodecylbenzene sulfonate, SDBS) and a hydrotropic salt (benzylamine hydrochloride, BzCl) in aqueous solution is investigated. Benzylamine hydrochloride is found to facilitate close packing of surfactants in the aggregates, inducing the structural transformation from SDBS micelles into unilamellar vesicles, and multilamellar vesicles. The multilamellar vesicles can transform into macroscale fibers, which are long enough to be visualized by the naked eye. Particularly, these fibers are robust enough to be conveniently separated from the surfactant solution. The combined effect of non-covalent interactions (e.g., hydrophobic effect, electrostatic attractions, and π– π interactions) is supposed to be responsible for the robustness of these self-assembled aggregates, in which π– π interactions provide the directional driving force for one-dimensional fiber formation.
Keywords: Surfactant self-assembly; Hydrotropic salt; Fiber; Vesicle
Interactions of gemini surfactants with two model proteins: NMR, CD, and fluorescence spectroscopies
by Razieh Amiri; Abdol-Khalegh Bordbar; M Flor García-Mayoral; Ahmad Reza Khosropour; Iraj Mohammadpoor-Baltork; Margarita Menéndez; Douglas V. Laurents (pp. 245-255).
Display Omitted► Cationic gemini surfactants do not interact with RNase A and HEWL at acidic pH. ► Hydrogen exchange NMR indicated that the stability of RNase A is lowered by about 1kcalmol−1. ► At alkaline pH, RNase A and HEWL do interact with gemini surfactants. ► Three different ProteinGemini complexes are formed including large aggregates.Gemini surfactants have two polar head groups and two hydrocarbon tails. Compared with conventional surfactants, geminis have much lower (μM vs. mM) critical micelle concentrations and possess slower (ms vs. μs) monomer⇆ micelle kinetics. The structure of the gemini surfactants studied is [HOCH2CH2–, CH3–, CH3(CH2)15–N+–(CH2)s–N+–(CH2)15CH3,–CH3,–CH2CH2OH]·2Br− where s=4, 5, or 6. Our objective is to reveal the effect of these cationic gemini surfactants on the structure and stability of two model proteins: Ribonuclease A (RNase A) and Hen Egg White Lysozyme (HEWL). 2D1H NMR and Circular Dichroism (CD) spectroscopies show that the conformation of RNase A and HEWL is unaffected at low to neutral pH where these proteins are positively charged, although hydrogen exchange shows that RNase A’s conformational stability is slightly lowered. At alkaline pH, where these proteins lose their net positive charge, fluorescence and CD spectroscopies and ITC experiments show that they do interact with gemini surfactants, and multiple protein•gemini complexes are observed. Based on the results, we conclude that these cationic gemini surfactants neither interact strongly with nor severely destabilize these well folded proteins in physiological conditions, and we advance that they can serve as useful membrane mimetics for studying the interactions between membrane components and positively charged proteins.
Keywords: Gemini surfactant; Ribonuclease A; Hen egg white lysozyme; Hydrogen exchange; Fluorescence spectroscopy; Circular dichroism spectroscopy; Isothermal titration calorimetry
The cis-bis(decanoate)tin phthalocyanine/DPPC film at the air/water interface
by Salvador Ramos; Cristina Garza; Hiram I. Beltran; José Campos-Terán; Jesús Arenas-Alatorre; Rolando Castillo (pp. 256-266).
Display Omitted► Films of a tin phthalocyanine and DPPC at the water/air interface were observed. ► Compression isotherms of tin phthalocyanine/DPPC films were obtained. ► Films present phase separation domains enriched in tin phthalocyanine. ► Phase separation domains present optical anisotropy and molecular order. ► A model for a pure tin phthalocyanine film was developed at the air/water interface.Films made of cis-bis-decanoate-tinIV phthalocyanine (PcSn10) and racemic dipalmitoylphosphatidylcholine (DPPC) are studied with compression isotherms and Brewster angle microscopy (BAM) at the air/water interface. Films enriched in PcSn10 present phase separation elliptical-shaped domains. These domains present optical anisotropy and molecular order. They are enriched in PcSn10, and the film outside these domains is enriched in DPPC, as shown in by high-angle annular dark-field transmission electron microscopy on Langmuir–Blodgett (LB) transferred films. Film collapse area and atomic force microscopy images of LB transferred films on mica indicate that the films are actually multilayers. A computational survey was performed to determine how the PcSn10 molecules prefer to self-assemble, in films basically made of PcSn10. The relative energetic stability for several dimeric assemblies was obtained, and a crystal model of the film was developed through packing and repeating the PcSn10 molecules, along the crystallographic directions of the unit cell. Our results contribute to understanding the strong interaction between PcSn10 and DPPC at the air/water interface, where even small quantities of DPPC (∼1–2%) can modify the film in an important way.
Keywords: Tin phthalocyanine; Phthalocyanine/DPPC films; Air/water interface films; Tin phthalocyanines/DPPC mixtures; cis; -Bis-decanoate-tin; IV; phthalocyanine
Porphyrin nanofiber patterning by air/water interfacial assembly: Effect of molecular structure, surface pressure, and ionic liquid doped subphase
by Xufei Liu; Tianyu Wang; Minghua Liu (pp. 267-273).
Display Omitted► Porphyrin nanofiber patterning by air/water interfacial assembly. ► Ionic liquid (IL) doped water subphases are critical. ► Molecular geometries and high surface pressure play important roles.Porphyrin nanofiber patterning was generated by air/water interfacial assembly. The air/water interfacial aggregation behavior of two prophyrins, both of which contain two hydrophobic alkyl chains and two carboxylic acid substituent groups at different positions, was investigated using UV spectra, FT-IR spectra, and AFM measurements on the corresponding transferred films. The porphyrin nanofiber patterning can only be produced on ionic liquid (IL) doped water subphases by the assembly of the building blocks with two carboxylic acids located at the para-position (TPPA2b-A). The results suggest that the bulky cations of ionic liquids (ILs) can interact with the carboxylate of porphyrin electrostatically. The appropriate molecular geometries, ionic liquid (IL) doped water subphases, and relatively high surface pressures help theTPPA2b-A to form nanofiber patterns.
Keywords: Porphyrin; Patterning; Nanofibers
Solubility limits and phase diagrams for fatty acids in anionic (SLES) and zwitterionic (CAPB) micellar surfactant solutions
by Sylvia S. Tzocheva; Peter A. Kralchevsky; Krassimir D. Danov; Gergana S. Georgieva; Albert J. Post; Kavssery P. Ananthapadmanabhan (pp. 274-286).
Display Omitted► Solubility limits of fatty acids in micellar surfactant solutions are determined. ► The solubility limits increase proportionally to the surfactant concentration. ► The mixing of the two components in the micelles can be both ideal and non-ideal. ► The interaction parameter depends on the chainlength mismatch. ► Phase diagrams of the investigated mixed solutions are obtained.The limiting solubility of fatty acids in micellar solutions of the anionic surfactant sodium laurylethersulfate (SLES) and the zwitterionic surfactant cocamidopropyl betaine (CAPB) is experimentally determined. Saturated straight-chain fatty acids with n=10, 12, 14, 16, and 18 carbon atoms were investigated at working temperatures of 25, 30, 35, and 40°C. The rise of the fatty acid molar fraction in the micelles is accompanied by an increase in the equilibrium concentration of acid monomers in the aqueous phase. Theoretically, the solubility limit is explained with the precipitation of fatty acid crystallites when the monomer concentration reaches the solubility limit of the acid in pure water. In agreement with theory, the experiment shows that the solubility limit is proportional to the surfactant concentration. For ideal mixtures, the plot of the log of solubility limit vs. the chainlength, n, must be a straight line, which is fulfilled for n=14, 16, and 18. For the fatty acids of shorter chains, n=10 and 12, a deviation from linearity is observed, which is interpreted as non-ideal mixing due to a mismatch between the chainlengths of the surfactant and acid. The data analysis yields the solubilization energy and the interaction parameter for the fatty acid molecules in surfactant micelles. By using the determined parameter values, phase diagrams of the investigated mixed solutions are constructed. The four inter-domain boundary lines intersect in a quadruple point, whose coordinates have been determined. The results can be applied for the interpretation and prediction of the solubility, and phase behavior of medium- and long-chain fatty acids and other amphiphiles that are solubilizable in micellar surfactant solutions, as well as for determining the critical micellization concentration (CMC) of the respective mixed solution.
Keywords: Solubility limit of fatty acids; Fatty acids in surfactant micelles; Solubilization energy; CMC for mixed micelles; Regular solution theory
Adsorption of non-ionic surfactants to the sapphire/solution interface – Effects of temperature and pH
by Ningning Li; Robert K. Thomas; Adrian R. Rennie (pp. 287-293).
Display Omitted► Reversible adsorption of non-ionic surfactants at the sapphire/solution surface is correlated with the cloud point. ► Adsorption of C12EO5 to sapphire is enhanced at low pH. ► Neutron reflection shows that adsorbed layers are highly hydrated.The adsorption of the non-ionic surfactants tetraoxyethylene glycol monododecyl ether (C12EO4), pentaoxyethylene glycol monododecyl ether (C12EO5), and hexaoxyethylene glycol monododecyl ether (C12EO6) to single crystal sapphire substrates has been studied using specular neutron reflection for solutions at the critical micelle concentration. The effects of temperature and pH of the solutions were studied as well as the differences between two different crystal faces, the C and the R planes. At neutral pH, significant adsorption was only observed when the temperature was raised above the cloud temperature. This adsorption was reversible and surfactant was displaced on cooling. Reducing the pH to 3 results in significantly increased adsorption of C12EO5 at 25°C with a central layer consisting mainly of surfactant (about 90%) on the C-plane substrate. A slightly smaller surface excess was observed for the R-plane. This contrasts with the significantly lower density observed even at high temperatures at neutral pH on both substrates. The results suggest that for neutral solutions surfactant association above the cloud point is the primary driving force for adsorption. At low pH, specific interactions with protonated surfaces are important. The structures of the highly hydrated layers are similar to those found for the surfactants at hydrophilic silica surfaces.
Keywords: Adsorption; Non-ionic surfactants; Aluminum oxide; Neutron reflectivity
Effect of support and pre-treatment conditions on Pt–Sn catalysts: Application to nitrate reduction in water
by Olívia Salomé G.P. Soares; Erika O. Jardim; Álvaro Reyes-Carmona; Javier Ruiz-Martínez; Joaquín Silvestre-Albero; Enrique Rodríguez-Castellón; José J.M. Órfão; Antonio Sepúlveda-Escribano; Manuel Fernando R. Pereira (pp. 294-301).
Display Omitted► Different preparation conditions lead to significant changes in catalysts surface. ► Pt monometallic catalyst is active for nitrate reduction only when supported on TiO2. ► Pt–Sn supported on AC is less active and more selective to N2 than on TiO2. ► The TiO2 support is directly involved in the reaction mechanism.The effect of the support (activated carbon or titanium dioxide) on the catalytic activity and selectivity to nitrogen of Pt–Sn catalysts in nitrate reduction was studied. The effects of the preparation conditions and the Pt:Sn atomic ratio were also evaluated. It was observed that the support plays an important role in nitrate reduction and that different preparation conditions lead to different catalytic activities and selectivities. Generally, the catalysts supported on activated carbon were less active but more selective to nitrogen than those supported on titanium dioxide. The monometallic Pt catalyst is active for nitrate reduction only when supported on titanium dioxide, which is explained by the involvement of the support in the reaction mechanism. The catalysts were characterized by different techniques, and significant changes on metal chemical states were observed for the different preparation conditions used. Only metallic Pt and oxidized Sn were observed at low calcination and reduction temperatures, but some metallic Sn was also present when high temperatures were used, being also possible the formation of Pt–Sn alloys.
Keywords: Nitrate reduction; Pt–Sn catalysts; Activated carbon; Titanium dioxide
Electrooxidation of nitrite on a silica–cerium mixed oxide carbon paste electrode
by Gustavo Silveira; Andréia de Morais; Paulo César Mendes Villis; Camila Marchetti Maroneze; Yoshitaka Gushikem; Alzira Maria Serpa Lucho; Fábio Luiz Pissetti (pp. 302-308).
Display Omitted► Highly dispersed silica–cerium mixed oxides are obtained by the sol–gel method. ► Cerium ions are present with oxidation states III and IV in the mixed oxide. ► The charge transfer resistance for the material was 32Ω cm−2. ► Electrooxidation of nitrite without electron mediators was observed.A silica–cerium mixed oxide (SiCe) was prepared by the sol–gel process, using tetraethylorthosilicate and cerium nitrate as precursors and obtained as an amorphous solid possessing a specific surface area of 459m2g−1. Infrared spectroscopy of the SiCe material showed the formation of the SiOCe linkage in the mixed oxide. Scanning electron microscopy/energy dispersive spectroscopy indicated that the cerium oxide particles were homogenously dispersed on the matrix surface. X-ray diffraction and29Si solid-state nuclear magnetic resonance implied non-crystalline silica matrices with chemical environments that are typical for silica-based mixed oxides. X-ray photoelectron spectroscopy showed that Ce was present in approximately equal amounts of both the 3+ and 4+ oxidation states. Cyclic voltammetry data of electrode prepared from the silica–cerium mixed oxide showed a peak for oxidation of Ce3+/Ce4+ at 0.76V and electrochemical impedance spectroscopy equivalent circuit indicated a porous structure with low charge transfer resistance. In the presence of nitrite, the SiCe electrode shows an anodic oxidation peak at 0.76V with a linear response as the concentration of the analyte increases from 3×10−5 at 3.9×10−3molL−1.
Keywords: Sol–gel process; Mixed oxide; Silica–ceria; Electrochemical sensor
One-pot deposition of palladium on hybrid TiO2 nanoparticles and catalytic applications in hydrogenation
by Afef Mehri; Hafedh Kochkar; Stéphane Daniele; Violaine Mendez; Abdelhamid Ghorbel; Gilles Berhault (pp. 309-316).
Display Omitted► Pd deposition was performed by mixing Pd precursors with citrate-functionalized TiO2. ► Strong interaction of citrate with Pd led to well dispersed systems. ► Tuning the Ti/citrate molar ratio controls Pd particle size. ► Possible formation of highly intrinsically active Pd/TiO2 catalysts.One-pot deposition of Pd onto TiO2 has been achieved through directly contacting palladium(II) salt with nanosized functionalized TiO2 support initially obtained by sol–gel process using titanium isopropoxide and citric acid. Citrate groups act as functional moieties able to directly reduce the Pd salt avoiding any further reducing treatment. Various palladium salts (Na2PdCl4 and Pd(NH3)4Cl2·H2O) and titanium to citrate (Ti/CA) ratios (20, 50, and 100) were used in order to study the effect of the nature of the precursor and of the citrate content on the final Pd particle size and catalytic properties of the as-obtained Pd/TiO2 systems. Characterization was performed using N2 adsorption–desorption isotherms, ICP-AES, FTIR, XRD, XPS, and TEM. The as-obtained hybrid Pd/TiO2 catalysts were tested in the selective hydrogenation (HYD) of an α,β-unsaturated aldehyde, i.e. cinnamaldehyde. Citrate-free Pd/TiO2-based catalysts present lower selectivity into saturated alcohol. However, citrate-functionalized Pd/TiO2 catalyst seems to control the selectivity, the particle size and dispersion of Pd NPs leading to high intrinsic activity.
Keywords: Palladium; Nanoparticles; TiO; 2; Citrate; Hybrid; Hydrogenation
Adsorption and protection of plasmid DNA on mesoporous silica nanoparticles modified with various amounts of organosilane
by Hong Yang; Kun Zheng; Zuoming Zhang; Wei Shi; Shubo Jing; Li Wang; Wei Zheng; Dazhou Zhao; Jianing Xu; Ping Zhang (pp. 317-322).
Display Omitted► Adsorption and protection of pDNA on Am-MSNs with various APTES amounts were studied. ► All the Am-MSNs exhibited good adsorption capacity of pDNA. ► Samples with moderate APTES amount could totally protect pDNA. ► The effect of APTES amount on pDNA protection was addressed. ► The materials might be good candidates for gene carriers.Ordered MCM-41-type mesoporous silica nanoparticles (MSNs) with pore size of 2.6nm were synthesized and were further modified with various amounts of 3-aminopropyltriethoxysilane (APTES), respectively, by a direct co-condensation method. These amine functionalized mesoporous silica nanoparticles (Am-MSNs) were employed to complex with plasmid DNA (pDNA) to study their adsorption and protection capacities. The results demonstrate the MSNs functionalized with aminopropyl groups present advanced adsorption capacities for pDNA immobilization. And Am-MSNs with high APTES amount lead to high amount of pDNA adsorption. Further investigation of pDNA protection shows that Am-MSNs with moderate APTES amount could completely protect pDNA from enzymatic degradation, while those with smaller and/or higher amount of APTES could partially provide protection of pDNA.
Keywords: Am-MSNs; PDNA; Adsorption; Protection; Enzymatic degradation
Synthesis, characterization and visible light photocatalytic properties of Bi2WO6/rectorite composites
by Yadan Guo; Gaoke Zhang; Huihui Gan (pp. 323-329).
Display Omitted► The visible light-induced Bi2WO6/rectorite was prepared by a sol–gel method. ► The photocatalyst shows excellent visible light photocatalytic activity. ► The photocatalyst remained stable after four photocatalytic degradation cycles.Visible light-induced Bi2WO6/rectorite (BR) composites were prepared by a sol–gel method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectrum, Fourier transform infrared (FTIR) spectrum, X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmet–Teller (BET). The UV absorption edges of the BR-450 catalyst showed a marked red shift as compared to that of the pure Bi2WO6. The photocatalytic activities of the as-prepared samples were evaluated by the photocatalytic degradation of 4BS dye in aqueous solution under visible light irradiation (>420nm). The results showed that the BR-450 catalyst exhibited a strong adsorption capability and a higher photocatalytic degradation activity than the pure Bi2WO6 for 4BS dye, which could be attributed to the synergetic effects of the adsorbability of rectorite and the photocatalytic property of Bi2WO6 in it.
Keywords: Bi; 2; WO; 6; Rectorite; Bi; 2; WO; 6; /rectorite; 4BS; Photocatalysis; Visible light; Sol–gel method
Amine-functionalised SBA-15 of tailored pore size for heavy metal adsorption
by Colm McManamon; Aoife M. Burke; Justin D. Holmes; Michael A. Morris (pp. 330-337).
Display Omitted► Synthesis of SBA-15 with tailored pore sizes through controlled thermal treatment. ► Adsorption of Pb and Cd ions from wastewater. ► Slower thermal treatment increases metal ion adsorption. ► Regeneration was achieved using HCl with little adverse effect on the material.This study examines the synthesis of SBA-15 with tailored pore sizes through controlled thermal treatment for the adsorption of Pb and Cd ions. The aim is to produce a material that can adsorb heavy metals at both high and low concentrations. The materials were characterised by means of N2 physisorption, powder X-ray diffraction (PXRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), microanalysis and transmission electron microscopy (TEM). The surface areas ranged from 410 to 871m2g−1, and pore diameter was increased from 5.9 to 10.8nm. This method allows for maximum adsorption of metal ions at very low concentrations. Metal ion adsorption was determined using an Atomic Absorption Spectrophotometer. The effects of pH were found to play a major role in the precipitation and, therefore, adsorption of metal ions. This method proved to be efficient at adsorbing large quantities of both metals (39 and 41mgg−1 for Pb and Cd, respectively).
Keywords: Metal ion adsorption; Pore size expansion; Functionalisation
Mesoporous silica nanoparticles immobilized salicylaldimine cobalt complexes as high efficient catalysts for polymerization of 1,3-butadiene
by Duihai Tang; Lei Zhang; Yinling Zhang; Zhen-An Qiao; Yunling Liu; Qisheng Huo (pp. 338-343).
Display Omitted► We synthesize a series of new nanocatalysts by the grafting method. ► All the catalysts are spherical morphology and monodisperse. ► All the catalysts are stable up to at least 200°C. ► All the catalysts show high conversion for polymerization of 1,3-butadiene. ► This is a facile way to synthesize the polymer–silica composite materials.We have synthesized a series of nanocatalysts with different sizes (50–200nm) for polymerization of 1,3-butadiene (Bd) by immobilizing salicylaldimine cobalt complexes on the mesoporous silica nanoparticles (MSNs). The prepared catalysts have been characterized by infrared (IR) spectra, thermal gravimetric analyses (TGAs), chemical composition analysis, nitrogen adsorption–desorption, scanning electron microscope (SEM), and transmission electron microscope (TEM). The nanocatalysts in combination with methylaluminoxane (MAO) show excellent catalytic efficiency in polymerization of 1,3-butadiene. The results reveal that these nanocatalysts also show higher activity than the homogeneous analog of cobalt complex and the same catalyst on bulky mesoporous silica supporting materials. The yield and the molecular weight of the poly-butadiene product depend on the particle size of the catalyst support. This catalysis process is also a facile way to directly synthesize the polymer/silica composite materials.
Keywords: Polymerization of 1,3-butadiene; Salicylaldimine transition metal complexes; Mesoporous silica nanoparticles; Polymer/silica composite materials
Preparation of trimethylchlorosilane-modified acid vermiculites for removing diethyl phthalate from water
by Xu-biao Yu; Chao-hai Wei; Lin Ke; Hai-zhen Wu; Xin-sheng Chai; Yun Hu (pp. 344-351).
Display Omitted► A hybrid organic–inorganic adsorbent based on acid vermiculite was prepared. ► The specific surface area of this adsorbent was much larger than that of traditional organoclay. ► The adsorbent exhibited strong organic affinity for the removal of hydrophobic pollutant. ► The length of alkyl chain of organic modifier was not the key factor for the adsorption performance of organoclay.A hybrid organic–inorganic material based on vermiculite was prepared to remove diethyl phthalate (DEP) from aqueous solution. Natural vermiculite was activated with HCl to improve the specific surface area and was then modified by silanization using trimethylchlorosilane. Organovermiculite prepared by ion exchange with hexadecyl trimethylammonium bromide (HDTMAB) was also tested for comparison. The leaching of 2molL−1 HCl at 80°C increased the specific surface area of vermiculite from 14.4 to 500.0m2g−1, and the average pore-diameter was decreased from 7.90nm to 2.75nm. Fourier transform infrared spectroscopy (FTIR) spectra indicated that trimethysilyl groups were grafted covalently on the surface of acid vermiculites. The specific surface area of trimethylchlorosilane-modified acid vermiculites (TMAVs) (355.4m2g−1) was much larger than that of organovermiculite (6.0m2g−1). The isotherm adsorption experiments of DEP showed that TMAVs exhibited linear isotherms, suggesting that the uptake of DEP was controlled by partitioning mechanism. The maximal partition coefficient (K d) of TMAVs was 3.1 times higher than that of organovermiculite, implying that TMAVs had stronger organic affinity than organovermiculite. The results demonstrate that the adsorption capacity and mechanism of organoclays were controlled by the specific surface area and organic loading, whereas the length of alkyl chain of organic modifier was not the key factor.
Keywords: Adsorption; Partition; Clay; Vermiculite; Diethyl phthalate
Activation energy of the reaction between hexacyanoferrate (Ш) and thiosulfate ions catalyzed by platinum nanoparticles confined in nanometer space
by Hongfang Li; Minna Cao; Tianfu Liu; Rong Cao (pp. 352-357).
.Display Omitted► The encapsulated Pt NPs are size and location controlled. ► The activation energy for reduction reaction is calculated in detail. ► The pore structures of supports greatly influenced the catalytic performance of Pt NPs.Pt nanoparticles (NPs) have been successfully encapsulated in SBA-15 mesoporous silica support. The silica was firstly functionalized by polyaminoamine (PAMAM) dendrimers with various generations and provided different nanometer space for Pt NPs. The growth of Pt NPs is restricted by the double confinement effect of PAMAM dendrimers and SBA-15 mesopores. The Pt NPs can be precisely controlled to localize inter- or intradendrimeric within SBA-15 tunnels. The different pore structures of Gn-PAMAM-SBA-15 (Gn-PS15) support have great influence on the catalytic performance of the encapsulated Pt NPs. The blocking structure of higher generation Gn-PS15 support debased the catalytic performance and increased the activation energy of reaction betweenFe(CN)63- andS2O32- in a certain degree.
Keywords: Pt NPs; Encapsulation; Support; Activation energy; Catalysis
Adsorption/bioadsorption of phthalic acid, an organic micropollutant present in landfill leachates, on activated carbons
by José D. Méndez-Díaz; Mahmoud M. Abdel daiem; José Rivera-Utrilla; Manuel Sánchez-Polo; Isidora Bautista-Toledo (pp. 358-365).
Display Omitted► Phthalic acid adsorption is governed by dispersion and electrostatic interactions. ► The phthalic acid adsorption process is highly dependent on the solution pH. ► The presence of microorganisms during adsorption increases the adsorption yield. ► Phthalic acid removal varies as a function of the natural water type.This study investigated the adsorption of phthalic acid (PA) in aqueous phase on two activated carbons with different chemical natures, analyzing the influence of: solution pH, ionic strength, water matrix (ultrapure water, ground water, surface water, and wastewater), the presence of microorganisms in the medium, and the type of regime (static and dynamic). The activated carbons used had a high adsorption capacity (242.9mg/g and 274.5mg/g), which is enhanced with their phenolic groups content. The solution pH had a major effect on PA adsorption on activated carbon; this process is favored at acidic pHs. PA adsorption was not affected by the presence of electrolytes (ionic strength) in solution, but was enhanced by the presence of microorganisms (bacteria) due to their adsorption on the carbon, which led up to an increase in the activated carbon surface hydrophobicity. PA removal varies as a function of the water type, increasing in the order: ground water
Keywords: Activated carbon; Adsorption; Phthalic acid; Microorganisms
Comprehensive study of mesoporous carbon functionalized with carboxylate groups and magnetic nanoparticles as a promising adsorbent
by Yue Chi; Wangchang Geng; Liang Zhao; Xiao Yan; Qing Yuan; Nan Li; Xiaotian Li (pp. 366-372).
Display Omitted► Ordered mesoporous carbon functionalized with carboxylate groups and magnetic nanoparticles. ► The functionalizations of mesoporous carbon material lead to an enhanced adsorption performance. ► Carboxylic functional groups result in an extremely rapid adsorption rate. ► Magnetic nanoparticles endow the mesoporous carbon with an easy magnetically separable process.Highly ordered mesoporous carbon functionalized with carboxylate groups and magnetic nanoparticles has been successfully synthesized. By oxidative treatment using (NH4)2S2O8 and H2SO4 mixed solution, numerous hydrophilic groups were created in the mesopores without destroying the ordered mesostructure of CMK-3. Through the in situ reduction in Fe3+, magnetic nanoparticles were successfully introduced into the mesopores, resulting in the multifunctional mesoporous carbon Fe-CMK-3. The obtained hybrid carbon material possesses ordered mesostructure, high Brunauer–Emmett–Teller (BET) surface area up to 1013m2/g, large pore volume of about 1.16cm3/g, carboxylic surface, and excellent magnetic property. When used as an adsorbent, Fe-CMK-3 exhibits excellent performances for removing toxic organic compounds from waster-water, with a high adsorption capacity, an extremely rapid adsorption rate, and an easy magnetically separable process. In the case of requiring emergency removal of large amount of organic pollutants in aqueous, the hybrid carbon adsorbent would be an ideal choice.
Keywords: Mesoporous carbon material; Carboxylic surface; Magnetic property; Adsorbent
Fe-ions modified mesoporous Bi2WO6 nanosheets with high visible light photocatalytic activity
by Sen Guo; Xiaofang Li; Haiqiang Wang; Fan Dong; Zhongbiao Wu (pp. 373-380).
Display Omitted► Fe-ions modified mesoporous Bi2WO6 nanosheets were successfully synthesized via a simple two-step method. ► The addition of small amount Fe-ions could markedly improve the activity of Bi2WO6. ► The optimized Fe-ions content was found to be 0.1wt.% in this investigation. ► Fe-ions mainly existed as Fe3+ and Fe2+ ions and were well uniformly distributed on the surface of photocatalyst.Fe-ions modified mesoporous Bi2WO6 nanosheets (Fe-Bi2WO6) were successfully synthesized via a simple two-step method, which involved a template-free hydrothermal process and a following impregnation treatment. The resultant products were characterized by XRD, TEM, XPS, EDX, ESR, UV–Vis, PL, and visible light photocatalytic measurements. Experimental results indicated that the addition of a small amount Fe-ions (optimized content at 0.1wt.%) could evidently improve the activity of Bi2WO6. The apparent reaction rate of Fe-Bi2WO6-0.1% ( k, 0.099min−1) was 3.2 times higher than that of Fe-Bi2WO6-0% ( k, 0.031min−1). The Fe-ions mainly existed as Fe3+ and Fe2+ ions, which were uniformly distributed on the surface of Bi2WO6 nanosheets and some Fe3+-ions substituted Bi3+-ions in Bi2O2 layers. Both of the concentration and state of Fe-ions played vital factors for the improved visible light photocatalytic activities.
Keywords: Bi; 2; WO; 6; Visible light; Photocatalysis; Toluene; Impregnation; Fe-ions
SiO2/graphene composite for highly selective adsorption of Pb(II) ion
by Liying Hao; Hongjie Song; Lichun Zhang; Xiangyu Wan; Yurong Tang; Yi Lv (pp. 381-387).
Display Omitted► SiO2/graphene composite prepared by a facile chemical route was considered as a novel adsorbent for Pb(II) ion. ► SiO2/graphene composite indicated high selectivity and efficiency for the removal of Pb(II) ion. ► The Pb(II) ion adsorption rate of the composite is rapid. ► Potential to be used in the water treatment as an adsorbent for Pb(II) ion.SiO2/graphene composite was prepared through a simple two-step reaction, including the preparation of SiO2/graphene oxide and the reduction of graphene oxide (GO). The composite was characterized by UV–Vis spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscope, and X-ray photoelectron spectroscopy, and what is more, the adsorption behavior of as-synthesized SiO2/graphene composite was investigated. It was interestingly found that the composite shows high efficiency and high selectivity toward Pb(II) ion. The maximum adsorption capacity of SiO2/graphene composite for Pb(II) ion was found to be 113.6mgg−1, which was much higher than that of bare SiO2 nanoparticles. The results indicated that SiO2/graphene composite with high adsorption efficiency and fast adsorption equilibrium can be used as a practical adsorbent for Pb(II) ion.
Keywords: Pb(II) ion; SiO; 2; /graphene composite; Adsorption
Synthesis of MCM-22 zeolite using rice husk as a silica source under varying-temperature conditions
by Yue Cheng; Mang Lu; Jiansheng Li; Xiaoyuan Su; Shunlong Pan; Chuang Jiao; Maohua Feng (pp. 388-394).
Display Omitted► Rice husk was utilized as a silica source for the synthesis of MCM-22. ► MCM-22 was synthesized using three-stage varying-temperature hydrothermal method. ► The prepared zeolite has strong adsorption capacity.In this study, rice husk, an abundant agricultural byproduct, was utilized as an alternative silica source for the synthesis of MCM-22. The zeolite with high crystalline was synthesized using a three-stage varying-temperature hydrothermal method. The prepared silica and MCM-22 were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that the duration required for zeolite crystallization was significantly decreased under varying-temperature conditions. The MCM-22 was in the form of thin platelet-like crystals, and no amorphous material existed in the framework of the MCM-22 after calcination and ammonium exchange. Cationic brilliant red 5GN, a basic dye used in the wool and blanket factories for fiber dyeing, was selected as the adsorptive to study the adsorption performance of the MCM-22. Adsorption experiments indicated that the maximum extent of adsorption was obtained at pH of 10, contact time of 60min, and MCM-22 dose of 1.0g/L. The adsorption kinetic has been described by first-order and pseudo-second-order models. It was observed that the rate of dye adsorption followed pseudo-second-order model.
Keywords: Rice husk ash; Hydrothermal method; Crystallinity; Adsorption kinetics
Electrophoretic deposition of TiO2 nanoparticles using organic dyes
by Y. Sun; M.S. Ata; I. Zhitomirsky (pp. 395-401).
Display Omitted► TiO2 films were obtained by electrophoretic deposition. ► Organic dyes provided charging and dispersion of TiO2 nanoparticles. ► Alizarin red, alizarin yellow, pyrocatechol violet and aurintricarboxylic acid dyes were used. ► The adsorption of dyes, deposition mechanism and deposition yield were studied. ► Dye-sensitized TiO2 films can be used for photovoltaic devices.Electrophoretic deposition method has been developed for the deposition of TiO2 nanoparticles modified with organic dyes. Alizarin red, alizarin yellow and pyrocatechol violet dyes were used for the dispersion and charging of TiO2 in ethanol and anodic electrophoretic deposition of TiO2 films. The deposition yield was varied by the variation of dye concentration in suspensions and deposition time. Aurintricarboxylic acid dye was used for the deposition of TiO2 from aqueous suspensions. It was found that thin films of pure aurintricarboxylic acid and composite aurintricarboxylic acid TiO2 films can be obtained. The deposition yield was studied by quartz crystal microbalance. Dye film thickness was varied in the range of 0.1–2μm by variation in the deposition time at a constant voltage. The composition of the films and the amount of the deposited material can be varied by the variation of TiO2 and dye concentration in suspensions and deposition time. The films were studied by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis and electron microscopy. The deposition mechanisms were discussed. The electrophoretic deposition method offers advantages for the fabrication of dye-sensitized TiO2 films.
Keywords: Titanium dioxide; Electrophoretic deposition; Dyes; Adsorption; Film
A mathematical model for the interactions between non-identical rough spheres, liquid bridge and liquid vapor
by A.H. Nazemi; A. Majnooni-Heris (pp. 402-410).
Display Omitted► Filling angles for a liquid volume between two spheres depend on the size ratio and surface roughness of the spheres. ► Liquid volume and capillary force relate to the suction, contact and filling angles, spheres roughness, and size ratio. ► The calculated equilibrium relations are shown to possess non-uniqueness. ► For any given humidity of the pore air, the suction increases with increasing particle size and increasing size ratio.Investigation of the interactions between the skeleton of an unsaturated particulate material and the contained liquid involves the general interaction model consisting of a liquid bridge in contact with two rigid smooth spherical particles of unequal size and dissimilar material, at a separation determined by their actual surface roughness, and surrounded by a gas with a vapor pressure at equilibrium with the liquid. The liquid retention and capillary force of the system are related to the capillary suction, liquid–solid contact angles, filling angles, roughness of the particles, and the ratio of particle radii in normalized terms by assuming a circular arc for the shape of the liquid profile. The normalized suction is also related to the corresponding relative humidity of the pore air. The calculated equilibrium relations are shown to possess non-uniqueness, which is interpreted in terms of mechanical properties of unsaturated particulate materials. The model is able to provide new insights into the behavior of an unsaturated particulate material.
Keywords: Capillary force; Liquid retention; Liquid bridge; Rough particles; Particulate systems
Wettability switching of SDS-doped polyaniline from hydrophobic to hydrophilic induced by alkaline/reduction reactions
by Wenguang Leng; Shuxue Zhou; Guangxin Gu; Limin Wu (pp. 411-418).
Wettability switching mechanism of SDS-doped PANI according to alkaline/reduction reaction from hydrophobic to hydrophilic.Display Omitted► Both morphology and wettability of polyaniline are controlled by SDS amount. ► Wettability switching is induced by either alkaline reaction or reduction reaction. ► The reduction reaction caused variation from hydrophobic to hydrophilic is obvious.In this paper, sodium dodecyl sulfate (SDS) is used as dopant to manipulate both morphology and wettability of polyaniline (PANI). When SDS amount is controlled within a certain range, micro/nano double-rough PANI with hydrophobic surface can be obtained, while insufficient or excess SDS can only lead to hydrophilic PANI. The double-rough PANI shows stimuli-responsive change in wettability to either alkaline reaction or reduction reaction from hydrophobicity to hydrophilicity. This quick response can be applied to quantitatively estimate NaOH concentrations within the range of 10−3–10−1M and to detect various reducing liquids.
Keywords: Polyaniline; Stimuli-responsive; Alkaline reaction; Reduction reaction; Hydrophobicity; Hydrophilicity
Analytical investigation and numerical modeling of collisions between a droplet and a fiber
by Jakub M. Gac; Leon Gradoń (pp. 419-425).
Display Omitted► Energy balance-based calculations allow to predict the scenario of droplet–fiber collision. ► Scenario of collision between droplet and fiber depends on non-dimensional parameters. ► Deposition occurs at low Weber and capillary number – otherwise detachment observed. ► Breakup of a droplet is observed at low impact parameter and high Weber number. ► Two-color lattice-Boltzmann method as an effective tool for droplet–fiber collisions modeling.The kinetics of the collisions between droplet and the fiber is being studied in both theoretical and numerical way. During theoretical investigations the balances between the various components of total energy of the droplet have been used. As a result, we have obtained the conditions (expressed in terms of non-dimensional parameters characterizing the system) at which the deposition of the droplet on the fiber or the separation of the droplet from the fiber occurs. The results of theoretical computation have been compared with the results of the numerical simulations using the two-color lattice-Boltzmann method.
Keywords: Numerical modeling; Droplet-fiber collisions; Surface tension; Lattice-Boltzmann method
Short time spreading and wetting of offset printing liquids on model calcium carbonate coating structures
by Hanna Koivula; Martti Toivakka; Patrick Gane (pp. 426-434).
Display Omitted► Imaging of offset printing liquids spreading on porous pigment surfaces with a high speed camera. ► Short time spreading controlled mainly by liquid properties. ► Pore structure important, especially for polar liquids, both at short and long times. ► Verifies the theory that linseed oil absorbs through adsorption along the pore walls. ► Findings useful for redesigning matt paper coatings to resist print rub.Spreading of oils and water on porous and pre-saturated model carbonate coating structures was studied with high speed video imaging. The short-time data were complemented with long time absorption and wicking experiments. The results indicate a strong dependence between surface structural features of the pigment tablets and water spreading at short times, both in non-saturated and water pre-saturated cases, while the oil spreading is mainly dependent on the liquid properties. Sodium polyacrylate dispersant on pigment surfaces is shown to contribute to water spreading and absorption. On pre-saturated structures the liquid-liquid interactions are dominant and the majority of results support spreading according to the molecular kinetic model. The evidence supports the hypothesis of S. Rousu, P. Gane, and D. Eklund, [“Influence of coating pigment chemistry and morphology on the chromatographic separation of offset ink constituents,” in The Science of Papermaking Transactions of the 12th Fundamental Research Symposium, FRC The Pulp & Paper Fundamental Research Society, Oxford, UK, 2001, p. 1115] that at long times the oils absorb into the porous structure at a rate proportional to the ratio of viscosity and surface tension, provided there is no sorptive action with the binder. A combination of nanosized pores and large surface area is useful for providing sufficient absorption capability for carbonate based coatings.
Keywords: Offset printing liquids; Linseed oil; Calcium carbonate; Spreading; Imbibition; Porous structure; Pore surface area
Surface self-segregation, wettability, and adsorption behavior of core–shell and pentablock fluorosilicone acrylate copolymers
by Junyan Liang; Ling He; Xia Dong; Tie Zhou (pp. 435-441).
Display Omitted► PDMS-b-(PMMA-b-PDFHM)2 in chloroform has strong surface migration of F and Si atoms. ► Surface oleophobicity of films is highly sensitive to the presence of Si enrichment. ► QCM-D technique is carried out to investigate the surface adsorption behavior of film. ► Cross-linked BA/MMA/DFHM/MPTMS/D4 shows high surface structural stability for water.The surfaces of films cast from core–shell fluorosilicone acrylate copolymer (BA/MMA/DFHM and BA/MMA/DFHM/MPTMS/D4) latexes and linear pentablock fluorosilicone acrylate copolymer (PDMS-b-(PMMA-b-PDFHM)2) solutions are intensively investigated and compared by XPS, DCA, AFM, and QCM-D measurements. It is found that the molecular structures and in-solution aggregate structures of these well-defined copolymers have a dramatic influence on the surface structure formation, surface wetting, and adsorption behavior. The PDMS-b-(PMMA-b-PDFHM)2 film cast from chloroform solution with high concentration of low-density unimers is able to perform as strong surface self-segregation of fluorine-containing groups as core–shell copolymer latex films. The BA/MMA/DFHM/MPTMS/D4 in the core–shell latex particles exhibits the less pronounced surface self-segregation of silicon-containing groups than PDMS-b-(PMMA-b-PDFHM)2 due to the occurrence of cross-linking reactions between polysiloxane chains. Indeed, such reactions induce the formation of silica network within the film material, which immobilizes tightly the fluorinated groups on the film surface and thus endows the film with higher surface structural stability for water compared to PDMS-b-(PMMA-b-PDFHM)2 film with similar surface fluorine concentration and even higher silicon concentration. Still, the PDMS-b-(PMMA-b-PDFHM)2 film definitely demonstrates higher advancing and receding contact angles for water than BA/MMA/DFHM/MPTMS/D4 latex film in the case of synergism between surface enrichment of fluorine and silicon.
Keywords: Fluorosilicone acrylate copolymers; Core–shell structure; Pentablock structure; Self-segregation; Wetting; Adsorption
Electrokinetic transport through the nanopores in cell membrane during electroporation
by Saeid Movahed; Dongqing Li (pp. 442-452).
Display Omitted► Mass transfer and fluid flow in nanopores during cell electroporation were studied. ► Poisson–Nernst–Planck and modified Navier–Stokes equations were simulated directly. ► Electrokinetics has great influences on ionic mass transfer through nanopores. ► Bigger nanopores have greater convective ionic flux. ► Ionic flux and fluid flow are different on two sides of cell membrane.In electroporation, applied electric field creates hydrophilic nanopores in a cell membrane that can serve as a pathway for inserting biological samples to the cell. It is highly desirable to understand the ionic transfer and fluid flow through the nanopores in order to control and improve the cell transfection. Because of submicron dimensions, conventional theories of electrokinetics may lose their applicability in such nanopores. In the current study, the Poisson–Nernst–Planck equations along with modified Navier–Stokes equations and the continuity equation are solved in order to find electric potential, fluid flow, and ionic concentration through the nanopores. The results show that the electric potential, velocity field, and ionic concentration vary with the size of the nanopores and are different through the nanopores located at the front and backside of the cell membrane. However, on a given side of the cell membrane, angular position of nanopores has fewer influences on liquid flow and ionic transfer. By increasing the radius of the nanopores, the averaged velocity and ionic concentration through the nanopores are increased. It is also shown that, in the presence of electric pulse, electrokinetic effects (electroosmosis and electrophoresis) have significant influences on ionic mass transfer through the nanopores, while the effect of diffusion on ionic mass flux is negligible in comparison with electrokinetics. Increasing the radius of the nanopores intensifies the effect of convection (electroosmosis) in comparison with electrophoresis on ionic flux.
Keywords: Cell electroporation; Cell transfection; Electroosmosis; Electrophoresis; Nanopore
Efficiency of layered double hydroxide nanoparticle-mediated delivery of siRNA is determined by nucleotide sequence
by Yunyi Wong; Helen M. Cooper; Kai Zhang; Min Chen; Perry Bartlett; Zhi Ping Xu (pp. 453-459).
Display Omitted► Layered double hydroxide (LDH) nanoparticle-mediated siRNA delivery. ► Cellular delivery efficiency of siRNAs using LDH depending on nucleotide sequence. ► dsDNA intercalation into LDH interlayer. ► Three interaction modes between dsDNAs and LDHs. ► The dsDNA:LDH mass ratio at the point of zero charge.In this paper, we report the novel finding that the cellular delivery efficiency of siRNAs or their mimic double-stranded (ds)DNA using layered double hydroxide (LDH) nanoparticles is dependent upon the nucleotide sequence. Efficacy of LDH-mediated delivery of four different siRNAs into cortical neurons and NIH 3T3 cells was found to vary widely (from 6 to 80%, and 2–11%, respectively). Our investigation into the formation of dsDNA–LDH complexes through monitoring the dsDNA:LDH mass ratio at the point of zero charge (PZC) indicated that the degree of intercalation of the individual dsDNA sequences into the LDH nanoparticles varied significantly. The dsDNA:LDH mass ratio at the PZC was found to be dependent on the nucleotide sequence. We further observed that PZC for each sequence was positively related to the extent of LDH-mediated internalization of the equivalent siRNA into neurons and fibroblasts. This novel finding therefore suggests that the mass ratio at the PZC is a useful predictive tool with which to assess the intercalation efficiency of selected siRNA sequences into the LDH interlayer and subsequent internalization into the cell cytoplasm. This finding will allow a more controlled approach to the design of suitable siRNA sequences for LDH-mediated siRNA delivery.
Keywords: Layered double hydroxide (LDH); siRNA delivery; Cellular uptake efficiency; Nucleotide sequence; Nucleic acid–LDH interactions
Highly active nanoscale zero-valent iron (nZVI)–Fe3O4 nanocomposites for the removal of chromium(VI) from aqueous solutions
by Xiaoshu Lv; Jiang Xu; Guangming Jiang; Jie Tang; Xinhua Xu (pp. 460-469).
Display Omitted► Fe0–Fe3O4 nanocomposites were synthesized and used for Cr(VI) removal. ► The synthesized nanocomposites were observed by SEM, HRTEM, XRD, and XPS. ► Effects of mass composition, pH, and initial Cr(VI) concentration were investigated. ► Kinetics and adsorption isotherms of such system were firstly described. ► Reaction mechanism has been deeply discussed and clearly presented in the figures.For the first time, nanoscale zero-valent iron (nZVI)–Fe3O4 nanocomposites, prepared by an in situ reduction method, are employed for chromium(VI) removal in aqueous environment. 96.4% Cr(VI) could be removed by these novel materials within 2h under pH of 8.0 and initial Cr concentration of 20mgL−1, compared with 48.8% by bare nFe3O4 and 18.8% by bare nZVI. Effects of several factors, including mass composition of nZVI–Fe3O4 nanocomposites, initial pH and Cr(VI) concentration, were evaluated. The optimal ratio of nFe3O4 to nZVI mass lies at 12:1 with a fixed nZVI concentration of 0.05gL−1. Low pH and initial Cr(VI) concentration could increase both the Cr(VI) removal efficiency and reaction rate. Corresponding reaction kinetics fitted well with the pseudo second-order adsorption model. Free energy change (Δ G) of this reaction was calculated to be −4.6kJmol−1 by thermodynamic study, which confirmed its spontaneous and endothermic characteristic. The experimental data could be well described by the Langmuir and Freundlich model, and the maximum capacity ( qmax) obtained from the Langmuir model was 100 and 29.43mgg−1 at pH 3.0 and 8.0, respectively. The reaction mechanism was discussed in terms of the mutual benefit brought by the electron transfer from Fe0 to Fe3O4.
Keywords: Nanoscale zero-valent iron; Magnetite; Nanocomposites; Cr(VI) removal
Structural and mechanical properties of Laponite–PEG hybrid films
by Kazuhiro Shikinaka; Kazuto Aizawa; Yoshihiko Murakami; Yoshihito Osada; Masatoshi Tokita; Junji Watanabe; Kiyotaka Shigehara (pp. 470-476).
Display Omitted► Flexible and transparent films were obtained by modification of PEG to Laponite. ► The ordered structure of Laponite platelets emerged in the films. ► The films consisted of PEG with short chain showed good mechanical properties. ► The mechanical properties originate from quasi-homogeneous dispersion of components.Inorganic/organic hybrids were obtained by the sol–gel type organic modification reaction of Laponite sidewalls with poly(ethylene glycol) (PEG) bearing alkoxysiloxy terminal functionality. By casting an aqueous dispersion of the hybrid, the flexible and transparent hybrid films were obtained. Regardless of the inorganic/organic component ratio, the hybrid film had the ordered structure of Laponite in-plane flat arrays. The mechanical strength of hybrid films was drastically improved by the presence of cross-linking among alkoxysilyl functionalities of PEG terminals and the absence of PEG crystallines. Hybrid films, especially those that consisted of PEG with short chain, showed good mechanical properties that originate from quasi-homogeneous dispersion of components due to anchoring of PEG terminal to Laponite sidewall and interaction of PEG to Laponite surface.
Keywords: Laponite; Hybrid; Sol–gel type organic modification reaction
Selective patterning of Si-based biosensor surfaces using isotropic silicon etchants
by Bradley W. Biggs; Heather K. Hunt; Andrea M. Armani (pp. 477-481).
Display Omitted► Achieved selective bioconjugation of integrated silica-on-silicon biosensors. ► Verified selective patterning with XPS, AFM and fluorescence microscopy. ► Demonstrated that device fabrication chemistries enabled selective patterning. ► Selective patterning approach is broadly applicable to other biosensor geometries.Ultra-sensitive, label-free biosensors have the potential to have a tremendous impact on fields like medical diagnostics. For the majority of these Si-based integrated devices, it is necessary to functionalize the surface with a targeting ligand in order to perform specific biodetection. To do this, silane coupling agents are commonly used to immobilize the targeting ligand. However, this method typically results in the bioconjugation of the entire device surface, which is undesirable. To compensate for this effect, researchers have developed complex blocking strategies that result in selective patterning of the sensor surface. Recently, silane coupling agents were used to attach biomolecules to the surface of silica toroidal biosensors integrated on a silicon wafer. Interestingly, only the silica biosensor surface was conjugated. Here, we hypothesize why this selective patterning occurred. Specifically, the silicon etchant (xenon difluoride), which is used in the fabrication of the biosensor, appears to reduce the efficiency of the silane coupling attachment to the underlying silicon wafer. These results will enable future researchers to more easily control the bioconjugation of their sensor surfaces, thus improving biosensor device performance.
Keywords: Biological sensors; Surface immobilization; Bioconjugation
Anionically cross linked homopolymer colloids applied in formation of platinum nanoparticles
by Behzad Tangeysh; Michael Fryd; Sara E.N. Hayik; Amanda C. Kamps; Bradford B. Wayland (pp. 482-484).
Display Omitted► Colloid particle formation occurs upon addition of diprotic acids to PDMAEMA. ► [PtCl6]2− cross linked polymer networks are observed to function as nanoreactors. ► Small narrowly dispersed platinum metal particles are produced from [PtCl6]2− cross linked polymer colloids. ► Large polydisperse platinum particles are obtained in the absence of polymer colloids. ► A convenient room temperature route is reported for formation of metal nanoparticles.Diprotonic sulfuric and succinic acids react efficiently with the tertiary amine sites in polydimethylaminoethylmethacrylate (PDMAEMA) to produce polymer colloid nano-particles held together by dinegatively charged anions that cross link the partially protonated PDMAEMA homopolymer. This procedure is used to encorporate [PtCl6]2− as a cross linker into the framework of well defined polymer network colloid particles that have dual roles as nanoreactors and a source of protective polymer coating. Reduction of the cross linking [PtCl6]2− groups produces platinum metal nano-particles (1.12(.25)nm) that are relatively small and narrowly dispersed. Formation of colloid particles by reaction of diprotic acids with homopolymers that have proton accepting centers provides a convenient intentional route to incorporate a variety of homopolymers into self assembled polymer network materials for applications as nanoreactors and transport systems.
Keywords: Colloid; Self assembly; Ionic cross linking; Dinegative anion cross linked polymer; PDMAEMA homo polymer; Platinum nanoparticles