Photocatalytic Activity of Nanocomposite Catalyst Films Based on Nanocrystalline Metal/Semiconductors

Abstract

The photocatalytic properties of anatase TiO(2) nanorods (NRs) and noble metal-semiconductor nanocomposites (TiO(2) NRs/Ag) prepared by colloidal chemistry routes and immobilized onto suitable substrates were investigated. Photocatalytic experiments were performed under UV irradiation in order to test the degradation of a target compound (the azo dye, methyl red) in aqueous solution using TiO(2) P25 Degussa as a reference material. Absorbance spectroscopy and liquid chromatography/mass spectrometry (LC/MS) measurements pointed out that, according to pH conditions, TiO(2) NRs and TiO(2) NRs/Ag presented a photoactivity up to 1.3 and 2 times higher than TiO(2) P25 Degussa, respectively. Notably, the TiO(2) NRs/Ag-based catalysts demonstrated a photocatalytic activity 2-fold higher than bare TiO(2) NRs. Remarkably, only a negligible dependence on pH conditions was detected for the nanocomposite catalyst, whereas both TiO(2) NRs and TiO(2) P25 Degussa showed much higher photoactivity at acidic pH. In all the investigated cases, the identified byproducts pointed out the occurrence of the same reaction mechanism, basically relying on the hydroxyl radical attaching on the benzene ring and on the homolytic rupture of the nitrogen-carbon bond of the dimethyl-amino moiety

Visible-Light-Active TiO2-Based Hybrid Nanocatalysts for Environmental Applications

“…Various hybrid nanocrystals such as TiO 2 -Ag [83] and TiO 2 -Au have been prepared by a photo-reduction method [84]. For instance, this approach has been applied to grow Ag or Au nanoparticles onto TiO 2 NRs [85,86] or on TiO 2 supported on glass fibres [87], thus generating heterostructures.…”

Colloidal Nanocrystalline Semiconductor Materials as Photocatalysts for Environmental Protection of Architectural Stone

“…Figure 1a, reports the typical TEM micrograph of the obtained sample, which is found to consist of rod-shaped and high aspect ratio nanocrystals of about 3 nm in diameter and with an average length of 18 nm. The TiO2 structures result anatase in phase and with a surface area of 240 ± 5 m 2 /g [28,32].…”

“…A solution of Methyl Red (MR) in isopropanol was used as model compound to simulate a generic pollutant at the surface of the stone. The MR solution represents a convenient choice because its degradation mechanism was extensively investigated in water solution and it is thus possible to obtain reliable information on the photo-degradation course [25,28]. After treating each stone by casting a defined volume of MR solution, photocatalysis experiments were performed by monitoring total reflectance spectra at scheduled time intervals.…”

“…Thanks to their nanosize and anisotropic shape, TiO 2 NRs possess a high surface area, hence, a high amount of surface active sites [28]. In addition, the specific geometry limits the charge carriers recombination because e − /h + can, in principle, locate in distal part of anisotropic nanostructure, thus ensuring an efficient charge separation [29].…”

Direct growth of shape controlled TiO2 nanocrystals onto SWCNTs for highly active photocatalytic materials in the visible

“…Several strategies have been proposed to cope with the first two issues including surface modification of the semiconductor particles with red-ox couples or noble metals and/or doping or coupling with narrower band gap semiconductors [13,15,16]. Particularly interesting is the recent work by Bian and co-workers, where they synthesized TiO 2 mesocrystals modified with plasmonic Au nanoparticles with improved photocatalytic activity in the visible for organic pollutant degradation.…”