TiO 2 Nanoarray Photoanode Improves Dye-Sensitized Solar Cells
- PDF / 194,497 Bytes
- 2 Pages / 576 x 783 pts Page_size
- 1 Downloads / 250 Views
Laser-Beam Method Yields 3D Synthesis of Copper Nanoparticles Inside a Polymer Substrate Researchers from The Institute of Scientific and Industrial Research at Osaka University, Japan, recently reported the first 3D writing of copper nanoparticles inside a polymer matrix. M. Sakamoto, T. Majima and co-workers used a two-color laserbeam technique often employed in 3D dense wiring of microelectronic components and photonic devices such as photonic crystal waveguides. In a recent issue of Chemistry of Materials (DOI: 10.1021/cm702170h), the group demonstrated that simultaneous irradiation with low-power UV and relatively highpower visible laser beams could be a successful combination for the production of copper nanoclusters without ablation of the polymer substrate. The researchers first prepared 3-mm thick films containing polyvinyl alcohol as a future hydrogenation source, Cu2+ from copper(II) acetate, and benzophenone (BP), starting from a formic acid solution. Upon irradiation with a UV laser, BP was excited to a triplet state, BP(T1), which easily abstracts hydrogen from polyvinyl alcohol to form the ketyl (BPH•) and polyvinyl alcohol radicals. Both radicals can reduce Cu2+ ions to Cu+, as demonstrated in separate measurements by laser flash photolysis. This one-photon process is, however, inefficient in further reducing the Cu+ ions. Figure 1. Optical image of a 3D array of copThese ions have a highly negative per nanoparticles in a polymeric substrate. + reducing potential, and the Cu would The top inset shows a schematic of the syn2+ oxidize back to Cu . The simultanethesis process, while the bottom inset is a high-resolution transmission electron microous irradiation with a visible laser furscope image of the nanoparticles. Reprother excites BPH• to BPH•(D1), which duced with permission from M. Sakamoto, has some efficiency in reducing Cu+ T. Tachikawa, M. Fujitsuka, and T. Majima, ions. This efficiency is further ampliChem. Mater. 20, 6 (2008) 2060. © 2008 by fied after the formation of the first the American Chemical Society. neutral copper clusters because two helping phenomena occur: The copper ions absorbed by the clusters have a significantly higher reducing potential, accessible now to the BPH• and PVA radicals, and the film better absorbs the visible laser radiation, generating thermal effects that accelerate the reduction process of the ions. The result, after about one hour of irradiation, is the formation of a 3D array of copper nanoparticles at the intersection of the two laser beams, visible with the naked eye as a red coloring in the film (Figure 1). EUGEN PANAITESCU ed from the coefficients of the highest occupied molecular orbitals. Because good conductors have bandgaps lower than 25 meV (the thermal energy at room temperature) and also have inverse participation numbers close to zero, the researchers defined a potential surface function as the negative log of the product of bandgap and inverse participation number. Symmetry reduces the number of possible configurations to a grid of 5151 poi
Data Loading...
