CENTRO DE INVESTIGACION Y DESARROLLO EN CIENCIAS APLICADAS "DR. JORGE J. RONCO"
Unidad Ejecutora - UE
Synthesis, characterization and photocatalytic activities of nanoparticulate N, S co-doped TiO2 having different surface-to-volume ratios
JULIÁN ANDRÉS RENGIFO-HERRERA; KATARZYNA PIERZCHALA; ANDREJZ SIENKIEWICZ; LAZLO FORRO; JHON KIWI; JACQUES E. MOSER; CESAR PULGARIN
JOURNAL OF PHYSICAL CHEMISTRY C
AMER CHEMICAL SOC
Año: 2010 vol. 114 p. 2717 - 2717
An efficient, visible-light active, N, S- co-doped TiO2-based photocatalyst was prepared by reacting thiourea with nanoparticulate anatase TiO2. Commercial anatase powders were manually ground with thiourea and annealed at 400 °C in two crucibles with different surface-to-volume ratios (S/V = 20 and 1.5) to prepare two N, S co-doped TiO2 materials. The differentiated aeration conditions during the catalyst annealing on the crucibles allowed for different amounts of O2 to reach the catalyst surface. The first material, with S/V = 20, herein referred as D-TKP 102-A, was clear beige colored. The second material, with S/V = 1.5, herein referred as D-TKP 102-B, was darker and revealed a markedly lower efficiency in Escherichia coli (E. coli) inactivation. The D-TKP 102-A powder presented visible light absorption due to the nitrogen (N) and sulfur (S) doping. X-ray photoelectron spectroscopy (XPS) signals for this catalyst were observed for N 1s peaks at binding energies (BE) of 399.2 and 400.7 eV due to interstitial N-doping or Ti-O-N species. The S 2p were due to SO4-2 signals with BE >168 eV and signals at 162.8 eV and 167.2 eV due to anionic and cationic S-doping respectively. By fast kinetic spectroscopy (DRTRS) the decay of the electron induced by pulsed light at l = 450 nm (~8 ns/ laser pulse) was followed for the D-TKP 102-A catalyst. Undoped D-TKP 102 catalyst did not promote the electron in the visible range and consequently no signal decay could be observed in the later case. Low-temperature Electron Spin Resonance (LT-ESR) measurements at 8 K provided evidence for electrons trapped in shallow traps, such as oxygen vacancies-Vo induced by N, S doped on D-TKP 102-A. The ESR measurements implementing the reactive scavenging with singlet oxygen scavenger, TMP-OH, revealed the production of singlet oxygen (1O2).