Lamellar multilayer hexadecylaniline-modified gold nanoparticle films deposited by the Langmuir-Blodgett technique

Organization of hexadecylaniline (HDA)-modified colloidal gold particles at the air-water interface and the formation thereafter of lamellar, multilayer films of gold nanoparticles by the Langmuir-Blodgett technique is described in this paper. Formation of HDA-capped gold nanoparticles is accomplished by a simple biphasic mixture experiment wherein the molecule hexadecylaniline present in the organic phase leads to electrostatic complexation and reduction of aqueous chloroaurate ions, capping of the gold nanoparticles thus formed and phase transfer of the now hydrophobic particles into the organic phase. Organization of gold nanoparticles at the air-water interface is followed by surface pressure-area isotherm measurements while the formation of multilayer films of the nanoparticles by the Langmuir-Blodgett technique is monitored by quartz crystal microgravimetry, UV-Vis spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy

Effect of Nanographite on Electrical Mechanical and Wear Characteristics of Graphite Epoxy Composites

Effect of weight fraction (WF) of nanographite (NG, 400 nm) on electrical, mechanical and wear and characteristics of graphite epoxy composites (GECs) were investigated. For this purpose, a series of GECs was prepared through dispersion of various WF of NG into epoxy resin, followed by curing with polyamine. Dispersion of NG into epoxy matrix and onward formation of GECs and was revealed through UV, Fourier transformed spectra and atomic force microscopy (AFM). Photoelastic analysis in combination with AFM reveals the presence of uniformly dispersed domain of NG into stress free GECs with fringe order ranging 0.23 - 0.61 under compression of 8 - 20 kgf. GECs have rendered a rising trend in DC conductance ranging 98.32 - 0.54 μS/cm with electrical percolation threshold at 175 WF of NG. GECs have shown enhanced compressive, impact, tensile, strength, Rockwell hardness and wear resistance at 200 WF of NG. In general, GECs has shown a marginal modification in their compressive strength by 5.30 % over cured epoxy. However, their impact and tensile strengths were largely improved to 31.78% and 43.98% over cured epoxy. The present manuscript provides a novel method of modification in electrical, mechanical and wear behaviour epoxy through introducing NG as a novel alternative to traditionally used graphite as filler for development of GECs

Effect of Cr and Fe Doping on the Structural and Optical Properties of ZnO Nanostructures

In the present study, we have synthesized Cr and Fe doped zinc oxide (ZnO) nano-structures (Zn1-δCraFebO; where δ= a + b=20%, a = 5, 6, 8 & 10% and b=15, 14, 12 & 10%) via sol-gel method at different doping concentrations. The synthesized samples were characterized for structural properties by X-ray diffractometer and field emission scanning electron microscope and the optical properties were carried out through photoluminescence and UV-visible spectroscopy. The particle size calculated through field emission scanning electron microscope varies from 41 to 96 nm for the samples synthesized at different doping concentrations. The optical band gaps calculated through UV-visible spectroscopy are found to be decreasing from 3.27 to 3.02 eV as the doping concentration of Cr increases and Fe decreases

Variation in morphology of gold nanoparticles synthesized by the spontaneous reduction of aqueous chloroaurate ions by alkylated tyrosine at a liquid-liquid and air-water interface

We demonstrate the formation of gold nanocrystals of different morphologies using alkylated tyrosine (AT) as a reducing agent at a liquid-liquid and air-water interface. The reduction of aqueous chloroaurate ions occurs in a single step wherein the AT molecule plays the multifunctional role of a phase transfer, reducing and capping agent. Gold nanoparticles formed at the air-water interface are very thin, flat sheet or ribbon-like nanostructures, which are highly oriented in the (111) direction. On the other hand, reduction of aqueous chloroaurate ions at a liquid-liquid interface by AT molecules present in the organic phase yielded nanoparticles having predominantly spherical morphology but with no specific crystallographic orientation. The difference in morphology of the nanoparticles may be due to the different orientational and translational degrees of freedom of the AT molecules and gold ions at these two interfaces. The AT-capped gold nanoparticles were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and nuclear magnetic resonance spectroscopy (1H NMR), while the LB films of flat gold sheets were also studied by X-ray photoemission spectroscopy (XPS)

Water-dispersible nanoparticles via interdigitation of sodium dodecylsulphate molecules in octadecylamine-capped gold nanoparticles at a liquid-liquid interface

This paper describes the formation of water-dispersible gold nano-particles capped with a bilayer of sodium dodecylsulphate (SDS) and octadecylamine (ODA) molecules. Vigorous shaking of abiphasic mixture consisting of ODA-capped gold nanoparticles in chloroform and SDS in water results in the rapid phase transfer of ODA-capped gold nanoparticles from the organic to the aqueous phase, the latter acquiring a pink, foam-like appearance in the process. Drying of the coloured aqueous phase results in the formation of a highly stable, reddish powder of gold nanoparticles that may be readily redispersed in water. The water-dispersible gold nanoparticles have been investigated by UV-Vis spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). These studies indicate the presence of interdigitated bilayers consisting of an ODA primary monolayer directly coordinated to the gold nanoparticle surface and a secondary monolayer of SDS, this secondary monolayer providing sufficient hydrophilicity to facilitate gold nanoparticle transfer into water and rendering them water-dispersible

Cationic surfactant mediated hybridization and hydrophobization of DNA molecules at the liquid/liquid interface and their phase transfer

Hybridization of complementary oligonucleotides mediated by a cationic surfactant at the water/hexane interface leads to hydrophobic, double-helical DNA which may be readily phase transferred to the organic phase and cast into thin films on solid substrates

Glucose induced in-situ reduction of chloroaurate ions entrapped in a fatty amine film: formation of gold nanoparticle-lipid composites

The formation of gold nanoparticle-lipid composite films by glucose-induced reduction of chloroaurate ions entrapped in thermally evaporated fatty amine films is described. Simple immersion of films of the salt of octadecylamine and chloroaurate ions (formed by immersion of thermally evaporated fatty amine films in chloroauric acid solution) in glucose solution leads to the facile in-situ reduction of the metal ions to form gold nanoparticles in the fatty amine matrix. The formation of gold nanoparticles is readily detected by the appearance of a violet color in the film and thus forms the basis of a possible new, gold nanoparticle-based colorimetric sensor for glucose. The formation of the fatty amine salt of chloroauric acid and the subsequent reduction of the metal ions by glucose has been followed by quartz crystal microgravimetry, Fourier transform infrared spectroscopy, X-ray photoemission spectroscopy and transmission electron microscopy measurements

Crystallization of SrCO<SUB>3</SUB> within thermally evaporated fatty acid films: unusual morphology of crystal aggregates

Reaction of CO2 with electrostatically entrapped Sr2+ ions within thermally evaporated stearic acid films leads to the in-situ growth of SrCO3 crystals in highly organized assemblies, the organization possibly occurring due to hydrophobic association of the crystallites covered by a monolayer of stearic acid

Morphology of BaSO<SUB>4</SUB> crystals grown at the liquid-liquid interface

Barite crystals were grown at the interface between an aqueous solution of Ba2+ ions and organic solutions of chloroform and hexane containing fatty acid/fatty amine molecules by reaction with sodium sulfate. The crystals grown at the interface in all cases had a nearly similar flat, plate-like morphology consistent with the barite structure. This morphology of the crystals resembles that of barite obtained during growth in solution in the presence of crystal growth inhibitors and is significantly different from that of barite crystals grown at the air-water interface. The use of interfacial effects such as dielectric discontinuity, finite solubility of the two solvents, etc., opens up exciting possibilities for tailoring the morphology of crystals at the liquid-liquid interface

Phase transfer of platinum nanoparticles from aqueous to organic solutions using fatty amine molecules

In this report we demonstrate a simple process based on amine chemistry for the phase transfer of platinum nanoparticles from an aqueous to an organic solution. The phase transfer was accomplished by vigorous shaking of a biphasic mixture of platinum nanoparticles synthesised in an aqueous medium and octadecylamine (ODA) in hexane. During shaking of the biphasic mixture, the aqueous platinum nanoparticles complex via either coordination bond formation or weak covalent interaction with the ODA molecules present in the organic phase. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilised platinum nanoparticles could be separated out from hexane in the form of a powder that is readily redispersible in weakly polar and non-polar organic solvents. The ODA-capped platinum nanoparticles show high catalytic activity in hydrogenation reactions and this is demonstrated in the efficient conversion of styrene to ethyl benzene. The nature of binding of the ODA molecules to the platinum nanoparticles surface was characterised by thermogravimetry, transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR)