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Langmuir-blodgett deposited monolayers of silicalite-1 seeds for secondary growth of continuous zeolite film

The formation of a dense monolayer of methanol treated Silicate-1 nanocrystals on Si wafer was demonstrated using the Langmuir-Blodgett (LB) technique and its successful use as a seed layer for preparing a continuous zeolite film by subsequent secondary growth was presented. SEM results proved that a well developed dense Silicate-1 film was obtained, which demonstrated that the LB monolayers are i

Liquid crystalline assemblies of ordered gold nanorods

Gold nanorods have been prepared in aqueous solution using a seed-mediated growth approach in the presence of surfactant. We observe the formation of liquid crystalline phases in concentrated solutions of high aspect ratio (13-18) gold nanorods by polarizing microscopy, transmission electron microscopy, and small angle x-ray scattering. These phases, which are stable up to 200°C, exhibit concentra

An experimental study of gas adsorption on fractal surfaces

The validity of the fractal versions of the FHH and BET theories for describing the adsorption of butane and nitrogen on a variety of partially dehydroxylated silica surfaces has been tested. The fractal dimensions obtained from adsorption data have been compared with those obtained completely independently using SAXS. It was found that the fractal dimensions obtained from butane adsorption isothe

The effect of surface texture on total reflection of neutrons and X-rays from modified interfaces

X-ray and neutron scattering from macroscopically rough surfaces and interfaces is considered and a new method of analysis based on the variation of the shape of the total reflection edge in the reflectivity profile is proposed. It was shown that in the limit that the correlation length and the height of the surface roughness are larger than the wavelength (at least 100 times bigger) of the incomi

Tuning percolation speed in layer-by-layer assembled polyaniline- nanocellulose composite films

Polyaniline of low molecular weight (ca. 10 kDa) is combined with cellulose nanofibrils (sisal, 4-5 nm average cross-sectional edge length, with surface sulphate ester groups) in an electrostatic layer-by-layer deposition process to form thin nano-composite films on tin-doped indium oxide (ITO) substrates. AFM analysis suggests a growth in thickness of ca. 4 nm per layer. Stable and strongly adher

Small-angle neutron scattering studies on the mesoporous molecular sieve MCM-41

A pure silica MCM-41 preparation with high crystalline order perpendicular to the channels has been examined using small-angle neutron scattering and the contrast variation method in both the calcined and template-containing forms. This defines various structural features such as template and water distributions and content, local silica density, and surface properties. Adsorption isotherm data, N

Silica-surfactant-polyelectrolyte film formation : Evolution in the subphase

We have previously reported that robust mesostructured films will grow at the surface of alkaline solutions containing cetyltrimethylammonium bromide (CTAB), polyethylenimine (PEI), and silica precursors. Here we have used time-resolved small-angle X-ray scattering to investigate the structural evolution of the micellar solution from which the films form, at several different CTAB-PEI concentratio

Multiple thin film formation from dilute mixtures of polyethyleneimine (PEI) and cetyltrimethylammonium bromide (CTAB)

Dilute mixtures of the water soluble polymer polyethyleneimine (PEI) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) form mesostructured thin films at the air/solution interface. In this paper we show that these films form spontaneously, reaching an equilibrium composition. When the film is removed, a new solid film rapidly reforms, with a similar morphology when inspected by Bre

Direct reversible voltammetry and electrocatalysis with surface-stabilised Fe2O3 redox states

Nanoparticle film voltammetry is employed to explore the presence and reactivity of surface-stabilised iron redox centers at the interface of immobilised Fe2O3 nanoparticles of ca. 4 nm diameter and aqueous buffer media. Mesoporous films of Fe2O3 nanoparticles on tin-doped indium oxide (ITO) substrates are formed in a layer-by-layer deposition process from aqueous colloidal Fe2O3 and aqueous cyclo

Studies of structure-transport relationships in biodegradable polymer microspheres for drug delivery using NMR cryodiffusometry

In order to rationally design polymer vehicles for controlled drug delivery it is important to completely understand the nature and mechanisms of the structural evolution of the polymer matrix that ultimately controls drug release kinetics. NMR cryoporometry has been used previously to study drug release from polymer vehicles. However, no previous studies have employed the integrated cryoporometry

Thin films of polyethylenimine and alkyltrimethylammonium bromides at the air/water interface

We have prepared and analyzed thin film structures formed by polyethylenimine and alkyltrimethylammonium bromide (CnTAB) surfactants at the air/water interface, using both surface and bulk sensitive techniques. In initial experiments it was observed that hexagonal arrays of rodlike micelles surrounded by the polymer were formed at the solution surface, with the principal axis of the micelles runni

Boronic acid dendrimer receptor modified nanofibrillar cellulose membranes

Cellulose nanofibrils from sisal of typically 4-5 nm diameter and ca. 250 ± 100 nm length are reconstituted into thin films of ca. 6 m thickness (or thicker freestanding films). Pure cellulose and cellulose composite films are obtained in a solvent evaporation process. A boronic acid appended dendrimer is embedded as a receptor in the nanofibrillar cellulose membrane. The number of boronic acid bi

Mesoporous silver films from dilute mixed-surfactant solutions by using dip-coating

A dilute mixed-surfactant solution to synthesize mesoporous silver films by using a dip-coating method was used for the creation of films over a large area of substrate. The method allows facile creation of films over a large area of substrate, unlike electrochemical deposition, and uses smaller amounts of surfactant than typical LLC syntheses. The silver ions in the solution, deposited in the int

Formation of CTAB-templated mesophase silicate films from acidic solutions

We have examined the effect of the different components in the spontaneous formation of surfactant-templated mesostructured silicate films grown at the air/solution interface. The rate of film formation shows differing dependencies on the concentrations of the silica precursor, tetramethoxysilane, the surfactant template, cetyltrimethylammonium bromide (CTAB), water and the solution pH. Further, w

Characterization of the structure of mesoporous thin films grown at the air/water interface using X-ray surface techniques

Grazing incidence X-ray diffraction (GIKD) and X-ray reflectivity have been used in situ to study the structure of surfactant-templated silica films grown at the air/water interface at different depths in the film. The results confirm that cylindrical silica-encased surfactant micelles are predominantly organized into a two-dimensional hexagonal structure, with the long axis parallel to the surfac

Self-assembly and phase behaviour of PEI : Cationic surfactant aqueous mixtures forming mesostructured films at the air/solution interface

Self-assembly processes and corresponding phase boundaries depend on the structure of interacting molecules. We have studied the effect of surfactant head-group structure and counterion on the self-assembly processes occurring in aqueous mixtures of the cationic polymer polyethylenimine (PEI) and the cationic surfactants cetyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPB) and cety

Ultrathin carbon film electrodes from vacuum-carbonised cellulose nanofibril composite

A novel way to produce ultrathin transparent carbon layers on tin-doped indium oxide (ITO) substrates is developed. The ITO surface is coated with cellulose nanofibrils (from sisal) via layer-by-layer electrostatic binding with poly(diallyldimethylammonium chloride) or PDDAC acting as the binder. The cellulose nanofibril-PDDAC composite film is then vacuum-carbonised at 5008C. The resulting carbon