Non-hydrolytic Sol Gel Reaction Research Articles

Large-Scale Synthesis of TiO2 Nanorods via Nonhydrolytic Sol−Gel Ester Elimination Reaction and Their Application to Photocatalytic Inactivation of E. coli

A simple method of synthesizing a large quantity of TiO(2) nanorods was developed. A nonhydrolytic sol-gel reaction between titanium(IV) isopropoxide and oleic acid at 270 degrees C generated 3.4 nm (diameter) x 38 nm (length) sized TiO(2) nanocrystals. The transmission electron microscopic image showed that the particles have a uniform diameter distribution. X-ray diffraction and selected-area electron diffraction patterns combined with high-resolution transmission electron microscopic image showed that the TiO(2) nanorods are highly crystalline anatase crystal structure grown along the [001] direction. The diameters of the TiO(2) nanorods were controlled by adding 1-hexadecylamine to the reaction mixture as a cosurfactant. TiO(2) nanorods with average sizes of 2.7 nm x 28 nm, 2.2 nm x 32 nm, and 2.0 nm x 39 nm were obtained using 1, 5, and 10 mmol of 1-hexadecylamine, respectively. The optical absorption spectrum of the TiO(2) nanorods exhibited that the band gap of the nanorods was 3.33 eV at room temperature, which is 130 meV larger than that of bulk anatase (3.2 eV), demonstrating the quantum confinement effect. Oleic acid coordinated on the nanorod surface was removed by the reduction of the carboxyl group of oleic acid, and the Brunauer-Emmett-Teller surface area of the resulting naked TiO(2) nanorods was 198 m(2)/g. The naked TiO(2) nanorods exhibited higher photocatalytic activity than the P-25 photocatalyst for the photocatalytic inactivation of E. coli.

Preparation of multicomponent oxides via non-hydrolytic sol–gel routes from novel bimetallic alkoxides

New series of double alkoxides of erbium and its oxides have been prepared by non-hydrolytic sol–gel reactions for the first time. These compounds were characterized with the help of FT-IR, NMR, Mass, DTA-TGA and SEM. The mass spectra show similar types of fragmentation pattern in all compounds. The XRD diffraction pattern shows an enhanced homogeneity at high temperature. TGA/DTA measurements show that thermal decomposition occurs in steps and entirely depends on the chemical compositions and the synthesis routes. The SEM observation reveals a high dense and smooth microstructural uniformity of polycrystalline nature. The physico-chemical properties show that crystallization behaviors can be controlled with the help of fine-tuning the chemical properties of chelating agents in order to increase the solubility of metal alkoxides.

POLYHEDRAL METALLOPHOSPHONATES AND -SILICATES: SYNTHESIS, FUNCTIONALIZATION, AND TRANSFORMATIONS

We synthesized molecular cyclic and polyhedral precursors to aluminophosphate and silicate materials and studied their substitution and nonhydrolytic sol-gel reactions.

Novel Ceramic Foams from Crystals of AlCl3(Pri2O) complex

In this paper we report a novel process for the production of ultralight cellular ceramics. The foams are generated by the heat treatment of crystals of the aluminum chloride isopropyl ether complex [AlCl3(Pri2O)]. The crystals, which are the only foam precursor, are obtained from concentrated solutions of AlCl3, Pri2O, and CH2Cl2. The foams consist of an arrangement of closed cells, 50–300 μm in diameter, having cell walls approximately 1–2 μm thick. An exceptionally high porosity is obtained ranging from 94 to 99%, and the cellular structure is retained during heating at 1500 °C. The foaming mechanism involves two consecutive nonhydrolytic sol-gel chemical reactions and physical processes including crystal dissociation, solvation, phase separation, and foaming. While other foaming mechanisms cited in the literature utilize one or more of the processes above, no analog mechanism exists in the organic, ceramic, or metal foam production processes. The effectiveness of the process originates from an initial precursor which contains all the necessary foaming components in such a way that the application of mild heating accelerates its transformation to a solid, dry, ultralight foamed material.