Dodecanethiol-stabilized gold nanoparticles with similar average size organize into different superlattice structures depending upon the method of preparation of the nanocrystals. Particles synthesized by the inverse micelle technique preferentially assemble into face-centered cubic (fcc) structures with long-range translational and orientational ordering. Gold nanoparticles obtained by the solvated metal atom dispersion (SMAD) method behave like "hard" spheres and predominantly organize into hexagonal close-packed (hcp) nanocrystal superlattices with long-range translational ordering. Different packing behavior results from differences in nanoparticle core morphologies induced by the synthetic method; fcc ordering is preferred by single crystalline nanoparticles, while hcp is preferred by polycrystalline nanoparticles. A combination of optical microscopy, transmission electron microscopy (TEM and HRTEM), selected area electron diffraction (SAED), atomic force microscopy (AFM), and X-ray diffraction (XRD) were used to characterize both the dispersed nanoparticles and the nanocrystal superlattices.

Oxidation of TiO or Ti2O3 led to the formation of TiO2 with activity in visible light much higher than when TiN was used as a precursor, pointing out the importance of oxygen defects/vacancies for extension of activity of TiO2 into the visible region.

Solid solutions of the formula, A,-,La,Ti3~,Nb,0,0 (A= K, Rb), exist for the range O

No abstract

No abstract

Titania-supported mesoporous materials are evoking interest in the field of photocatalysis. [1] In particular, transitionmetal-ion-containing MCM-41-supported TiO 2 photocatalysts have been studied for the degradation of pollutants. [2][3][4] However, MCM-41 has a unidirectional pore system and this type of pore arrangement restricts the transport of products and reactants. MCM-48 possesses a continuous three-dimensional (3D) pore system that provides favorable mass-transfer kinetics and seems to be a more attractive candidate for catalytic applications. There is no report to date of a single-step synthesis for the preparation of a visible-light, transition-metal-ion-containing MCM-48-supported TiO 2 photocatalyst.The Ti-Cr-MCM-48 photocatalyst prepared in a single step exhibits far superior photocatalytic activity compared to the TiO 2 -Cr-MCM-48 prepared by a post-impregnation method. The high activity of the Ti-Cr-MCM-48 photocatalyst is attributed to a synergistic interaction between Cr ions dispersed in the silica framework and the nanocrystalline nature of titania crystallites anchored onto the pore walls.Treatment of polluted air by catalytic techniques is a wellestablished process. Catalytic combustion processes require temperatures of 473-1473 K for efficient operation and hence are energy intensive. Furthermore, these traditional methods of treatment are not economically feasible at low pollutant concentrations. There is a need for an ambient temperature catalytic process that can carry out complete detoxification of air pollutants at low levels. Hence, extensive research is underway in this area. Acetaldehyde is a common indoor air pollutant, emitted from incomplete combustion from fireplaces, and consumer products such as adhesives, nail polish, etc.Photocatalysis has attracted the attention of research scientists for several years. [5,6] Titanium dioxide is one of the most widely studied photocatalysts. [7,8] A common approach to enhance the photocatalytic activity of TiO 2 is to use supported TiO 2 catalysts. Herrmann and co-workers [9] and Xu and Langford [1,10] have shown that nanometer-sized titania on a highsurface-area support produces higher quantum yields than pure titania. The discovery of mesoporous materials has attracted the attention of many research workers. [11,12] Transition-metal-incorporated mesoporous materials have been extended for use as photocatalysts. [13][14][15][16] Smirniotis and co-workers [2][3][4] have reported the photodegradation of organics using TiO 2 -loaded Cr-incorporated MCM-41. However, the catalysts employed in their studies were prepared by a two-step process and the preparation of such titania-loaded transition-metal-containing MCM-41 photocatalysts typically took at least 4 days if not more. The loading of titania was carried out by impregnation, which led to partial breakage of the tubular walls of the MCM-41, resulting in a decrease in surface area. Thus, there is a need for shortening the time of synthesis of titania-supported mesoporous materials while k...

No abstract

No abstract