Synthesis, Characterization, and Photocatalytic Activities of Nanoparticulate N, S-Codoped TiO₂ Having Different Surface-to-Volume Ratios

Abstract

An efficient, visible light active, N, S-codoped TiO 2 -based photocatalyst was prepared by reacting thiourea with nanoparticulate anatase TiO 2 . 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-codoped TiO 2 materials. The differentiated aeration conditions during the catalyst annealing on the crucibles allowed for different amounts of O 2 to reach the catalyst surface. The first material, with S/V ) 20, herein referred to as D-TKP 102-A, was clear beige colored. The second material, with S/V ) 1.5, herein referred to as D-TKP 102-B, was darker and revealed a markedly lower efficiency in Escherichia 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 signals for this catalyst were observed for N 1s peaks at binding energies of 399.2 and 400.7 eV due to interstitial N-doping or Ti-O-N species. The S 2p were due to SO 4 -2 signals with BE >168 eV and signals at 162.8 and 167.2 eV due to anionic and cationic S-doping, respectively. By fast kinetic spectroscopy, the decay of the electron induced by pulsed light at λ ) 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 latter case. Low-temperature electron spin resonance measurements at 8 K provided evidence for electrons trapped in shallow traps, such as oxygen vacancies, V o , 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 ( 1 O 2 ).

Smart and green interfaces: From single bubbles/drops to industrial environmental and biomedical applications

“…Other examples of improved microstructures for textile functionalization were shown in [99,100,101]. The target was the design, synthesis, evaluation and characterization of environmentally friendly bactericide composites on textiles like polyester and on flexible thin low cost polymers like polyethylene.…”

Solar photocatalysis for water disinfection: materials and reactor design

“…McGuigan et al 3 also emphasize the importance of low cost of any employed method, pointing out the poorest are the most likely to have worst access to clean drinking water. Furthermore, taking into account that the 25 regions of the world most affected are those with large annual sunfall, it can be concluded that SODIS is a 'geographically' attractive method for the water quality assurance. Successful use of SODIS projects in Uganda and Vietnam have led to the UN description of SODIS as a 'sustainable' and 'transferrable' technology.…”

“…20 Although not currently recognized as good practice, another method of water disinfection in remote locations is use of a solar water disinfection system or plant. These systems may be distinguished from the bottles used in the SODIS protocol in that they are immobile and are typically continuous flow, engineered, 25 point of use reactors. Malato et al 5 have reviewed the state of the art of such solar reactors.…”

“…TiO 2 photocatalysis, therefore, has real potential for disinfection of resistant microorganisms. 7,[22][23][24][25][26] In addition to the hydroxyl radicals, other 15 oxidative species such as superoxide anions and singlet oxygen can also be created ( Figure 2). The first report of TiO 2 photocatalytic inactivation of bacteria was in 1985 by Matsunaga et al 27 , and since then a large number of microorganisms have been reported to be photocatalytically 20 inactivated.…”

“…A number of reviews address different aspects of the process such as application of photocatalysis for disinfection of water contaminated with pathogenic micro-organisms 28,29 , decontamination of water by solar photocatalysis 30 and proposed mechanisms and modeling. 31 The majority of photocatalytic 25 studies cite the hydroxyl radical ( • OH) as the reactive oxygen species (ROS) responsible for microorganism inactivation, although other ROS such as hydrogen peroxide (H 2 O 2 ) and the superoxide anion radical (O 2…”