TiO 2 -x N x nanoparticles were prepared by employing the direct amination of 6−10-nm-sized titania particles. Doping on the nanometer scale led to an enhanced nitrogen concentration of up to 8%, compared to e2% in thin films and micrometer-scale TiO 2 powders. The synthesized TiO 2 -x N x nanocrystals are catalytically active and absorb well into the visible region up to 600 nm, thus exemplifying the use of a nanostructurebased synthesis as a means of producing novel photocatalytic materials.

Using a simple nanoscale exclusive synthesis route, TiO 2-x N x photocatalysts that can be tuned to absorb across the visible region are produced in seconds at room temperature. The photocatalysts are formed by employing the direct nitridation of anatase TiO 2 nanostructures with alkylammonium salts. Depending on the degree of TiO 2 nanoparticle agglomeration, catalytically active TiO 2-x N x anatase structured particles are obtained whose absorption onset extends well into the visible region at λ ∼ 550 nm. The introduction of a small quantity of palladium in the form of the chloride or nitrate facilitates further nitrogen uptake, appears to lead to a partial phase transformation, displays a counterion effect when compared also to the acetate, and produces a material absorbing well into the near-infrared. The introduction of palladium via the chloride also facilitates the formation of small tetrahedral and octahedral palladium-based crystallites throughout the TiO 2-x N x lattice. Surprisingly, no organics appear to be incorporated into the final TiO 2-x N x products. The resulting photocatalysts readily photodegrade methylene blue and lead to the catalytic oxidation of ethylene as they are placed as gels on surfaces. In contrast to the current nitridation process, which is quite facile at the nanoscale, we observe a much slower nitration of Degussa P25 nanopowders and little or no direct nitridation of micrometer-sized anatase or rutile TiO 2 powders at room temperature. We thus demonstrate an example of how a traversal to the nanoscale can vastly improve the efficiency for producing important submicron materials.

Nanowires, sandwiched nanoribbons, and nanotubes of SnO2 are synthesized using elevated temperature synthesis techniques, and their structures are characterized in detail by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition to the normal rutile structured SnO2, it has been possible to form an orthorhombic superlattice-like structure in the present study. The orthorhombic structure can form in a thin nanowire, coexist with the normal rutile structured SnO2 in a sandwiched nanoribbon, or occur in the form of nanotubes. This result is distinct from that for bulk SnO2 where pressures in excess of 150 kbar are required to form the orthorhombic form. The orientation relationship between the orthorhombic SnO2 and the rutile structured SnO2 is determined to be [001]o || [102̄]t and (100)o || (010)t for the nanowires and sandwiched nanoribbons, and [001]o || [3 ]t and (110)o || (451)t for the nanotubes. Although the growth direction of the rutile structured SnO2 nanowires is along [101]t, two growth directions are found to occur in the nanostructures having the orthorhombic SnO2 structure. They are [010]o for nanowires and [1̄10]o for the sandwiched nanoribbons and nanotubes. The results in this study and the observation of orthorhombic SnO2 may result from the formation of the products in an oxygen deficient environment.