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A new synthetic route has been utilized for the formation of multiple-shaped Pt nanoparticles (NPs) under UV-photoirradiation. The one-step process exclusively generates different shapes, such as spheres, cubes, short and long wires, and flakelike nanostructures. The reduction of Pt(IV) ions was done using alkaline 2,7-DHN in CTAB micellar media under 3 h UV-photoirradiation. The synthesized Pt NPs are stable for more than 4 months in ambient conditions. By changing the surfactant-to-metal ion molar ratios and the concentration of reducing agent, the particle size and shape can be tuned. The mechanisms of the particles formation with variable shapes and the effects of different reaction parameters are studied in detail. The present approach can be extended to a fast synthetic method for the formation of other metallic and semiconductor particles with variable shapes. The evolved Pt NPs will find promising applications in different types of organic and inorganic catalysis reactions, medicinal applications, and nanoelectronics.

In this paper a convenient route for synthesizing Au(core)-Pd(shell) bimetallic nanoparticles in toluene has been reported as a result of co-reduction of gold(III) and palladium(II) precursors in toluene. N,N-Dimethyldodecylamine was used as a capping agent for the core-shell particles, which not only imparts stability to the organosol but also controls morphology of the evolved particles. The particles were characterized using UV-visible, transmission electron microscopy, and X-ray diffraction measurements. All results substantiate the formation of core-shell structure of the synthesized particles.

A new fluorescent probe, methylamino derivative of pyrene, has been considered to characterize the concentration dependent emission behavior of an aqueous solution of anionic surfactants, viz., SDS, DSS, and SDBS. It was found that the emission of the probe is uniquely sensitive to the changes in surfactant (anionic) concentration due to the functional group effect of the probe over the parent moiety, pyrene. Here, 1-methylaminopyrene (MAP) showed significant quenching of emission well below the critical micellar concentration (cmc) of the surfactant. Excimer emission of the probe due to the formation of premicellar aggregates of the surfactant solutions at a concentration close to but below the cmc and again an enhanced emission of the probe above the cmc were observed as a consequence of definite MAP-surfactant interactions. These observations assisted the possible quantification ofsurfactant concentrations and their chain length dependent premicellar aggregate formations. Significant monomer emission in relation to probe distribution in micelle was analytically authenticated. Dynamic light scattering (DLS) studies revealed the incorporation of the probe molecules in the micellar core. The fluorophore emission showed nonlinear behavior when the surfactant concentration was far above the cmc. Abrupt changes in the emission characteristics in relation to the micellar concentration led to the determination of the cmc of the surfactants.

In anionic micelles, SDS has been found to remove the kinetic barrier for the reaction between methylene blue (MB) and arsine. The color bleaching (reduction) of SDS micelle bound MB by arsine gives a quantitative measureof arsenic concentration in the sub-parts-per-million levels for a test sample. Arsine is generated by reacting NaBH 4 with arsenic-containing samples present along with the other reagents. The extent of the micelle-bound dye reduction is facilitated in the presence of Ag or Au nanoparticles. The micelles, in turn, help to increase the collision probability between the dye and arsine, whereas nanoparticles help the electron relay from AsH 3 to the micelle-bound dye. This method depicts for the first time a simple, reproducible way to demonstrate nanoparticle-catalyzed dye reduction by arsine in an organized medium.

Formation of stable gold nanoparticles of different size and shape has been reported via UV photoactivation of HAuCl4 in variable concentrations of TX-100. It has been shown that smaller particles ...