Electron Spectroscopic Studies of Bis-(2,2‘-bipyridine)-(4,4‘-dicarboxy-2,2‘-bipyridine)-ruthenium(II) and Bis-(2,2‘-bipyridine)-(4,4‘-dicarboxy-2,2‘-bipyridine)-osmium(II) Adsorbed on Nanostructured TiO₂and ZnO Surfaces

Abstract

The adsorption of the dyes bis-(2,2‘-bipyridine)-(4,4‘-dicarboxy-2,2‘-bipyridine)-ruthenium(II) and bis-(2,2‘-bipyridine)-(4,4‘-dicarboxy-2,2‘-bipyridine)-osmium(II) on nanostructured TiO2 and ZnO was investigated by photoelectron spectroscopy (PES) using synchrotron radiation. Comparison of the results gives insight into the electronic structure of the molecules, as well as to their interaction with the substrates. The identity of the central metal ion of the dye complex was found not to influence the bonding mode of the molecule on the surfaces. However, when comparing the adsorption on the two metal oxides, the chemical state of the carboxyl group was found to be different. Binding to TiO2 results in four chemically equivalent carboxyl oxygens, while the oxygens are found chemically nonequivalent for adsorption onto ZnO. In addition, information concerning the frontier electronic structure was obtained by measuring the valence band region by PES using different photon energies and the N1s near edge X-ray absorption spectroscopy (NEXAFS) spectra for the two molecules adsorbed on the surfaces.

XPS characterization of sensitized n-TiO2 thin films for dye-sensitized solar cell applications

“…However, it is observed a widening of the O 1s peak, attributed to carboxylic groups adsorbed onto oxide surface [19,[31][32][33][34]. This interaction is responsible for the electronic coupling between TiO 2 nanocrystals and the adsorbed sensitizer.…”

Structural and optical properties of ZnO nanoparticles synthesized at different pH values

“…Among metal oxides, zinc oxide (ZnO) nanoparticles have been of great interest due to their potential applications in many important fields of science and technology such as gas sensors, solar-cells, field emitters, piezoelectric nano-generators, light emitting diodes (LED), excellent photo catalysts and nano-optoelectronic devices [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. ZnO is a direct band gap semiconductor with band gap energy of 3.36 eV, high exciton binding energy of 60 meV at room temperature and high dielectric constant [9,[21][22][23][24][25][26].…”

Chapter 9. Nano dimensional ZnO: new chemical insights from an old material

“…Additionally nanocrystalline ZnO has been widely studied due to potential applications in optoelectronic fields and fabricating nanodevices, 5 especially in varistors, piezoelectric devices, surface acoustics wave devices, solar cells, transparent conductors, transparent UV-protection films, gas-detecting chemical sensors and antibacterial activity. [6][7][8][9] Researchers have been able to develop a zinc-based coating capable of resisting a great range of temperatures, and the attack of ultraviolet exposure equivalent to 19,000 solar hours. ZnO coatings are now routinely used to protect components of spacecraft, which are some of the most technically advanced and complex machines ever made.…”