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Liquid crystal codendrimers with a statistical distribution of phenolic and mesogenic groups : Behavior as langmuir and langmuir - Blodgett films

The first series of carbosilane liquid crystal codendrimers with groups of different polarity has been synthesized. The chemical structure of the newly synthesized materials and the composition of the codendrimers were studied by NMR spectroscopy and MALDI-TOF MS. It was found that the codendrimers tend to form stable Langmuir films at the air-water surface. The influence of composition and genera

Structural evolution of surfactant - Silica film-forming solutions, investigated using small-angle neutron scattering

Time-resolved small-angle neutron scattering has been used to investigate the evolution of micelles in the subphase of surfactant-templated silica film-forming solutions. Two samples have been prepared using cetyltrimethylammonium bromide (CTABr), as the structure-directing agent, and different amounts of tetramethoxysilane (TMOS) (CTABr/TMOS molar ratio 0.093, 0.139). The solutions have been repr

Accessibility of dye molecules embedded in surfactant-silica hybrid materials in both powder and film forms

Two CTABr-silica mesophases have been prepared, one of them as a powder with hexagonal structure containing Congo Red, the other one as a film with cubic structure containing Disperse Red 1. In the former case the dye has been occluded via co-entrapping, whereas in the latter it has been covalently anchored to the silica matrix via a co-condensation route. In both systems, the dye molecules proved

Accessibility to gases of dye molecules in hybrid surfactant-silica mesophases

Two types of CTABr-silica mesophases have been prepared, one of them a powder with hexagonal structure containing Congo Red, another one a film with cubic structure containing Disperse Red 1. In the former case the dye has been occluded via co-entrapping, whereas in the latter it has been covalently anchored to the silica matrix via a co-condensation route. In both systems, the dye molecules prove

Underpotential surface reduction of mesoporous CeO 2 nanoparticle films

The formation of variable-thickness CeO 2 nanoparticle mesoporous films from a colloidal nanoparticle solution (approximately 1-3-nm-diameter CeO 2) is demonstrated using a layer-by-layer deposition process with small organic binder molecules such as cyclohexanehexacarboxylate and phytate. Film growth is characterised by scanning and transmission electron microscopies, X-ray scattering and quartz

Macroscopic, mesostructured cationic surfactant/neutral polymer films : Structure and cross-linking

Mesostructured films of alkyltrimethylammonium bromides or cetylpyridinium bromide and polyethylenimines that spontaneously self-assemble at the air/water interface have been examined using a range of surface sensitive techniques. These films are unusual in that they can be micrometers thick and are relatively robust. Here we show that the films can be cross-linked and thus removed from the liquid

Template-induced crystal growth

The process of "mineralisation" in biology leads to a diversity of inorganic structures based on silica or calcium carbonate. Some of these are composite and, at the same time, highly crystalline. In all cases a molecular or self assembled "template" species has been identified as the promoter for the crystallisation of the new structure. In biology these "templates" are the end step in the convey

Concentration-dependent formation mechanisms in mesophase silica-surfactant films

The development of surfactant-templated mesoporous films grown at the air/water interface was investigated using specular and off-specular X-ray reflectivity techniques. The samples were prepared in acidic conditions using cetyltrimethylammonium bromide (CTABr, 0.075 M) and different concentrations (0.27-0.88 M) of tetramethyloxysilane (TMOS). At CTABr/TMOS molar ratio between 0.277 and 0.093, the

The role of protein hydrophobicity in thionin-phospholipid interactions : A comparison of α1 and α2-purothionin adsorbed anionic phospholipid monolayers

The plant defence proteins α1- and α2-purothionin (Pth) are type 1 thionins from common wheat (Triticum aestivum). These highly homologous proteins possess characteristics common amongst antimicrobial peptides and proteins, that is, cationic charge, amphiphilicity and hydrophobicity. Both α1- and α2-Pth possess the same net charge, but differ in relative hydrophobicity as determined by C18 reverse

Formation of shear thinning gels from partially oxidised cellulose nanofibrils

Partially C(6) oxidised, dispersed cellulose nanofibres form shear thinning gels in the presence of moderate amounts of simple salts or surfactants providing a novel method to structure aqueous formulations, which may be of use in a substantial number of applications where it is desirable to enhance the viscosity of formulated materials using components from a renewable, sustainable source.

Preparation dependent stability of pure silica MCM-41

The degradation of pure silica MCM-41 materials prepared under various synthesis conditions has been investigated. Materials from preparations titrated with acid during synthesis not only show improved long range ordering of the pore system but also greater stability. This effect is greatest in unheated preparations.

Formation of mesophase surfactant-templated silica thin films from acidic solutions

The formation of mesophase silica-surfactant thin films at the air/solution interface has been studied in situ using off-specular X-ray reflectivity, Brewster angle microscopy and small angle scattering. Results for cetyltrimethylammonium bromide-templated films suggest that the formation mechanism is strongly dependent on the silica:surfactant ratio, and this is confirmed by studies on the subpha

Hydrothermal core-shell carbon nanoparticle films : Thinning the shell leads to dramatic pH response

Carbon nanoparticles with phenylsulfonate negative surface functionality (Emperor 2000, Cabot Corp.) are coated with positive chitosan followed by hydrothermal carbonization to give highly pH-responsive core-shell nanocarbon composite materials. With optimised core-shell ratio (resulting in an average shell thickness of ca. 4 nm, estimated from SANS data) modified electrodes exhibit highly pH-sens

Soap and sand : Construction tools for nanotechnology

Nanotechnology is the science of making and using very small structures. As the scales of the constructions become smaller, the existing methods of making these structures - lithography, etching and micromoulding - although constantly improving, will reach physical limits. To overcome the limitations and create smaller, designed and ordered structures, a so-called 'bottom-up' approach must be used

Preparation and characterisation of chemisorbents based on heteropolyacids supported on synthetic mesoporous carbons and silica

The preparation of chemisorbents based on tungsto- and molybdophosphoric acids supported on two types of synthetic mesoporous carbons and two types of mesoporous silica is described. Strong solid acids with good accessibility to acid sites may potentially be effective adsorbents for the removal of basic molecular impurities, such as amines, from ultrapure manufacturing environments. Prepared mater

The effect of hydrogen on the morphology of n-type silicon electrodes under electrochemical conditions

We study the electrochemical roughening of a silicon electrode surface during the hydrogen evolution reaction in a fluoride electrolyte using neutron reflection. We demonstrate that as the roughening process modifies the morphology of the silicon surface we can follow the changes by observing the changes in the shape of the total reflection feature. We assume that the change in the morphology of t

Formation of surfactant-silica mesophase films at a silica interface

Neutron reflectometry has been used to study the development of mesoporous silicated films at a hydrophilic silicon-solution interface. We find the time for film formation was altered in a manner similar to that seen at the air-liquid interface as the silica source-to-surfactant ratio was altered. Interestingly for films grown at the silica-liquid interface in a cell with no air space only one gro

Electrochemically active mercury nanodroplets trapped in a carbon nanoparticle - chitosan matrix

A thin composite film of carbon nanoparticles (ca. 8 nm diameter) and chitosan biopolymer (poly-D-glucosamine, from chitin, 75-85% deacetylated) was prepared by evaporation from aqueous dispersion onto glassy carbon electrode surfaces. The amine groups in the chitosan biopolymer were used to effectively bind Hg(II) ions from an aqueous pH 5 KCl solution. During redox cycling voltammetric responses