Gold–Titanium(IV) Oxide Plasmonic Photocatalysts Prepared by a Colloid-Photodeposition Method: Correlation Between Physical Properties and Photocatalytic Activities

Abstract

Colloidal gold (Au) nanoparticles were prepared and successfully loaded on titanium(IV) oxide (TiO(2)) without change in the original particle size using a method of colloid photodeposition operated in the presence of a hole scavenger (CPH). The prepared Au nanoparticles supported on TiO(2) showed strong photoabsorption at around 550 nm due to surface plasmon resonance (SPR) of Au and exhibited a photocatalytic activity in mineralization of formic acid in aqueous suspensions under irradiation of visible light (>ca. 520 nm). A linear correlation between photocatalytic activity and the amount of Au loaded, that is, the number of Au nanoparticles, was observed, indicating that the activity of Au/TiO(2) plasmonic photocatalysts can be controlled simply by the amount of Au loading using the CPH method and that the external surface area of Au nanoparticles is a decisive factor in mineralization of formic acid under visible light irradiation. Very high reaction rates were obtained in samples with 5 wt % Au or more, although the rate tended to be saturated. The CPH method can be widely applied for loading of Au nanoparticles on various TiO(2) supports without change in the original size independent of the TiO(2) phase. The rate of CO(2) formation also increased linearly with increase in the external surface area of Au. Interestingly, the TiO(2) supports showed different slopes of the plots. The slope is important for selection of TiO(2) as a material supporting colloidal Au nanoparticles.

Enhanced Photocatalytic Activity for H2 Evolution under Irradiation of UV–Vis Light by Au-Modified Nitrogen-Doped TiO2

“…Oxygen vacancies induced by nitrogen doping in TiO 2 can act as color centers and can also contribute to the visible light absorption [8]. In addition, after loading with Au, another absorbance band at approximately 550 nm can be found and is attributed to the surface plasmonic resonance (SPR) effect of the Au nanoparticles [34], [35]. Metal nanoparticles, such as Au, Cu, and Ag, are able to absorb and scatter photons in the visible region.…”

Eco-Friendly Physical Activation Methods for Suzuki–Miyaura Reactions

“…The possible relaxation mode for metal nanoparticles with a diameter < 30 nm is the non-radiative Landau damping process, which causes the formation of electron-hole pairs [171,172]. The electron-hole pairs are generated by the elevated electric fields caused by the resonance condition between the plasmonic metal nanoparticles and the electromagnetic radiation [173]. These energetic electrons, or so-called hot electrons, are available at the surface of the Pd sites in the bimetallic catalysts due, as explained before, to the considerably higher work function values of Pd (5.0 eV) than Ag (4.3 eV) and Au (4.7 eV), making the electron transfer process quite feasible.…”

Photodegradation of Dye Pollutants Catalyzed by H₃PW₁₂O₄₀/SiO₂ Treated with H₂O₂ under Simulated Solar Light Irradiation

“…In recent years, visible light responsive photocatalysts have been extensively studied. TiO 2 modified systems have been prepared to obtain visible-light reactivity in recent years [15][16][17][18]. Polyoxometalates (POMs) have also been recently studied as efficient photocatalysts for the degradation of organic dyes and it indicates that the photocatalytic activity of POMs is comparable to that of the semiconductor TiO 2 [19][20][21].…”