Fe2o3 shell growth on Pt nanoparticles.

Fe2O3 shells have been synthesized around Pt cores to create Pt@Fe2O3 core-shell nanoparticles. The synthesis conditions allow control of the shell shape and allow the preparation of both hexagonal shells and spherical shells. 2D cross-sectional TEM images show that the cores are not positioned at the centers of the shells. By rotating the nanoparticles and monitoring the apparent motions of the cores in the 2D cross-sectional images, it is possible to determine quantitatively the radial position of the Pt core with respect to the center of the Fe2O3 shell. The distribution of core positions within the core-shell structures is bimodal. These observations suggest that the Fe2O3 shells grow on the Pt cores by a nucleation process, rather than layer-by-layer growth.

Tailoring the shapes of Fe(x)Pt(100-x) nanoparticles.

Fe(x)Pt(100-x) nanoparticles of varying composition have been synthesized with various shapes and sizes using a high pressure synthesis method which allows control of synthesis conditions, in particular the reaction temperature. Tailoring the shapes and sizes of Fe(x)Pt(1-x) nanoparticles allows one to control a variety of properties that are relevant to the many potential applications of metallic nanoparticles. Shape and composition can be used to control catalytic activity and to achieve high packing density in self-assembled films. Variation of both nanoparticle size and shape has been achieved by using various different solvents. The solvents used in the nanoparticle synthesis can influence the product because they can play a role as surfactants. Using solvents of various types it has been possible to synthesize Fe(x)Pt(100-x) nanoparticles with a variety of shapes including spherical, rod-like, cubic, hexagonal and high aspect ratio wires. Control of nanoparticle shape opens the door to their being used in various technological applications for which spherical nanoparticles are ineffective.

Optimization of mesoporous titanosilicate catalysts for cyclohexene epoxidation via statistically guided synthesis.

An efficient approach to improve the catalytic activity of titanosilicates is introduced. The Doehlert matrix (DM) statistical model was utilized to probe the synthetic parameters of mesoporous titanosilicate microspheres (MTSM), in order to increase their catalytic activity with a minimal number of experiments. Synthesis optimization was carried out by varying two parameters simultaneously: homogenizing temperature and surfactant weight. Thirteen different MTSM samples were synthesized in two sequential 'matrices' according to Doehlert conditions and were used to catalyse the epoxidation of cyclohexene with tert-butyl hydroperoxide. The samples (and the corresponding synthesis conditions) with superior catalytic activity in terms of product yield and selectivity were identified. In addition, this approach revealed the limiting values of each synthesis parameter, beyond which the material becomes catalytically ineffective. This study demonstrates that the DM approach can be broadly used as a powerful and time-efficient tool for investigating the optimal synthesis conditions of heterogeneous catalysts.