Fabrication of two-dhviensional and three-deviensional platinum nanoclusters to serve as high technology catalysts - catalyts capable of 100% reaction selectivity

Electron beam lithography and photolithography, followed by size reduction lithography, are carried out to produce two-dimensional nanostructures in the 1-100 nanometer range. The development of size reduction lithography in Berkeley permits parallel formation of 10¹¹ nanowires to provide 1 cm² surface area nanocluster catalyst that can be used in model studies of catalytic activity and selectivity for comparison with single crystal surfaces. Electron beam lithography, a series preparation technique can only produce 10⁹ nanoparticles or 1 mm² metal surface area after one day. In most cases, active surface areas of 1 cm² or more are required for reaction selectivity studies. We shall review the fabrication, cleaning, and characterization of these two-dimensional nanostructure catalysts and their performance in hydrogenation and dehydrogenation reactions, using ethylene and cyclohexene. The metal-oxide interface may be important for several of the catalytic processes that were studied. Three-dimensional nanoclusters with 10¹⁵ nanoparticles are prepared by stabilization of the nanoclusters on an inorganic mesoporous support. The large metal content coupled with the high surface-to-volume ratio of nanoclusters leads to 1 m² of metal surface area. Monodispersed platinum nanoparticles are prepared by alcohol reduction methods and then encapsulated in mesoporous silica, which is prepared by a hydrothermal reaction in the same aqueous solution. The encapsulated particles are reduced to the metallic state, making them active for catalysis. A second synthetic method produces well dispersed nanoclusters on mesoporous silica using a two-step method and Iow power sonication to facilitate nanocluster diffusion into the silica channels. Twe-dimensional and three dimensional nanoclusters which possess controlled spacing and monodispersed metallic nanoclusters, respectively, provide the opportunity to develop green catalysts that demonstrate 100% reaction selectivity.