Janus Nanostructures Based on Au−TiO₂ Heterodimers and Their Photocatalytic Activity in the Oxidation of Methanol

Abstract

Au-TiO 2 snowman-like heterodimer nanoparticles were prepared by a surface sol-gel process based on gold Janus nanoparticles whose surface-protecting monolayers consisted of a hemisphere of hydrophobic 1-hexanethiolates and the other of hydrophilic 2-(2-mercaptoethoxy)ethanol. Transmission electron microscopic measurements showed that the resulting TiO 2 nanoparticles (diameter 6 nm) exhibited well-defined lattice fringes that were consistent with the (101) diffraction planes of anatase TiO 2 . The heterodimer nanoparticles displayed apparent photoluminescence that was ascribed to electronic transitions involving trap states of TiO 2 particles, and the photocatalytic activity was manifested by the oxidative conversion of methanol into formaldehyde, which was detected quantitatively by the Nash method. The enhanced photocatalytic performance, as compared to that of the TiO 2 nanoparticles alone, was ascribed to the charge separation of photogenerated electrons and holes at the Au-TiO 2 interface that was facilitated by the close proximity of the gold nanoparticles. These results suggested that (i) there were at least two possible pathways for photogenerated electrons at the TiO 2 conduction band, decay to the trap states and transfer to the gold nanoparticles, and (ii) energy/electron transfer from the trap states to gold nanoparticles was less efficient. In essence, this study showed that the snowmanlike heterodimers might be exploited as a homogeneous photocatalytic system for the preparation of functional molecules and materials.

Photocatalytic reduction of CO2 in methanol to methyl formate over CuO–TiO2 composite catalysts

“…The potential of conduction band of CuO (E cb = À0.78 V) is more negative than those of formic acid and formaldehyde yield, and the potential of valence band of TiO 2 was more positive than those of methanol oxidation [21][22][23]. The potential of methanol oxidation by a hole to ÁCH 2 OH is E 0 CH 3 OH=CH 2 OH = 0.927 V [24,25]. Methyl formate can be produced through the esterification of formic acid and methanol and dimerization of formaldehyde via Tishchenko reaction [26].…”

Giant Enhancement of Near-Ultraviolet Light Absorption by TiO2 via a Three-Dimensional Aluminum Plasmonic Nano Funnel-Antenna

“…9 To activate the photocatalytic effect using UVlight with longer wavelengths and enhance this efficiency, many works have demonstrated that doping/mixing of other sulfides, metals, or oxides such as CdS, Fe 2 O 3 , Au, Ag, or Ag 2 O nanoparticles can be helpful. 9−11 Most of these works focus on sample structure 8,12,13 and preparation, 14−16 or chemical interaction among particles 17,18 to improve electron transition involved in the photocatalytic process.…”

Quick and Facile Preparation of Visible light-Driven TiO2 Photocatalyst with High Absorption and Photocatalytic Activity

“…These approaches include transition metal11 or nonmetal1213 doping, noble metal loading14, semiconductor compounding151617, and organic dye sensitizing18. Chen et al recently reported that disorder-engineered TiO 2 nanocrystals (black TiO 2 ) prepared by hydrogenating TiO 2 nanocrystals at 20 bars H 2 atmosphere for approximately 5 days exhibited substantial solar-driven photocatalytic activities, including the photo-oxidation of organic molecules in water and the production of hydrogen with the use of a sacrificial reagent19.…”