Absorption and fluorescence spectroscopy of rhodamine 6G in titanium dioxide nanocomposites

A comparison has been made between the spectroscopic properties of the laser dye rhodamine 6G (R6G) in mesostructured titanium dioxide (TiO2) and in ethanol. Steady-state excitation and emission techniques have been used to probe the dye-matrix interactions. We show that the TiO2-nanocomposite studied is a good host for R6G, as it allows high dye concentrations, while keeping dye molecules isolated, and preventing aggregation. Our findings have important implications in the context of solid state dye-lasers and microphotonic device applications. (C) 2003 Elsevier B.V. All rights reserved.

A Two-Step Sol–Gel Method for Synthesis of Nanoporous TiO2

This article reports a study of the effects of synthesis parameters on the preparation and formation of mesoporous titania nanopowders by employing a two-step sol-gel method. These materials displayed crystalline domains characteristic of anatase. The first step of the process involved the hydrolysis of titanium isopropoxide in a basic aqueous solution mediated by neutral surfactant. The solid product obtained from step 1 was then treated in an acidified ethanol solution containing the same titanium precursor to thicken the pore walls. Low pH and higher loading of the Ti precursor in step 2 produced better mesoporosity and crystallinity of titanium dioxide polymorphs. The resultant powder exhibited a high surface area (73.8 m(2)/g) and large pore volume (0.17 cm(3)/g) with uniform mesopores. These materials are envisaged to be used as precursors for mesoporous titania films as a wide band gap semiconductor in dye-sensitized nanocrystalline TiO2 solar cells.

Nanocrystalline zirconia as catalyst support in methanol synthosis

Nanocrystalline zirconia was synthesized and used as catalyst support for methanol synthesis. The nanocrystallite particles have new physical and textural properties which are critical in determining the catalytic performance. Nanocrystalline zirconia changes the electronic structure and affects the metal and support interactions on the catalyst. leading to facile reduction. intimate interaction between copper and zirconia, more corner defects and oxygen vacancies on the surface of the catalyst. All these changes are beneficial to the reaction of methanol synthesis from hydrogenation of CO2. As a result. higher conversion of CO2 and selectivity of methanol are achieved compared to the catalysts prepared by conventional co-precipitation method. (C) 2004 Elsevier B.V. All rights reserved.

Mesoporous nanocrystalline zirconia with lamellar and MSU structure

Without introduction of any stabilizer, the mesoporous nanocrystalline zirconia with lamellar and MSU structure was obtained via solid state reaction coupled with surfactant templating method. The phase, surface area and pore structure of zirconia prepared with this novel method could be designed, tailored and controlled by varying synthesis parameters. The phase transformation was controlled by particle size. The mesostructure possesses nanocrystalline pore wall, which renders it more thermally stable than amorphous framework. The results suggest strongly that in solid state synthesis system mesostructure formation still follow the supramolecular self-assembly mechanism. The lamellar and reverse hexagonal structure could be transformed at different OH-/Zr molar ratios in order to sustain the low surface energy of the mesophases. The lamellar structure was preferred at higher OH-/Zr molar ratios but reverse hexagonal was at low ratios.