Non-aqueous sol–gel synthesis through a low-temperature solvothermal process of anatase showing visible-light photocatalytic activity

Abstract

A novel, facile method based on a non-aqueous sol-gel solvothermal process has been developed to synthesise spherical TiO 2 nanoparticles (NPs) in one pot. The reaction between titanium (IV) tert-butoxide (Ti[OC(CH 3 ) 3 ] 4 ) and benzyl alcohol is a simple procedure, that resulted in the formation of highly crystalline titania NPs with a small size of only 6 nm, and with a correspondingly high surface area. The chemical formation mechanism of the metal oxide NPs has been proposed, and the degree of surface hydroxyls (-OH groups) examined. The products of the synthesis were characterised by X-ray powder diffraction (XRPD) including the advanced whole powder pattern modelling (WPPM) method, high-resolution transmission electron microscopy (HR-TEM), thermo-gravimetric analysis (TGA), UV-visible diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR). The photocatalytic activity (PCA) was evaluated both in liquidsolid phase, by monitoring the degradation of an organic dye (methylene blue (MB)) under UV-light irradiation, and in gas-solid phase, by following the degradation of 2-propanol, under UV-and visible-light exposure. The synthesized titania powders showed themselves to be excellent photocatalysts in liquid-solid phase (under UV irradiation), but also to possess a superior PCA in gas-solid phase, under visible-light exposure. The effects on the PCA of the very small crystalline domain size, surface composition and the presence of organic molecules from the synthesis process of the TiO 2 NPs were shown to account for this behaviour.

Synthesis and photoactivity of anatase porous single crystals with different pore sizes

“…The band gap can be determined using a plot of the modified Kubelka-Munk function [26] (αhυ) 1/2 versus the energy of absorbed light (hυ): (αhυ) 1/2 =A(hυ-E g ), where α, h, υ, E g and A is adsorption coefficient, Planck constant, light frequency, band gap energy, and a constant related to the effective masses associated with the valence and conduction bands. By extrapolating the linear portion of (αhυ) 1/2 versus the hυ plot to α= 0, E g are established as about 3.22eV which agrees well with those reported in the literatures [27][28][29].…”

Mechanistic Aspects in the Formation, Growth and Surface Functionalization of Metal Oxide Nanoparticles in Organic Solvents

“…According to 1 H NMR data, an analogous ether elimination reaction was also found for the formation of anatase TiO 2 nanoparticles prepared from the reaction of titanium isopropoxide with benzyl alcohol on the surface of carbon nanomaterials using microwave heating . The solvothermal reaction between titanium(IV) tert ‐butoxide and benzyl alcohol led to the elimination of di‐ tert ‐butyl ether and benzyl ether …”

“…In recent years, the reaction between metal alkoxides and alcohols involving ether elimination has been widely applied for the nonhydrolytic synthesis of crystalline metal oxide nanoparticles. Benzyl alcohol favors the ether elimination reaction during solvothermal treatment with early transition metal alkoxides . Pinna et al.…”

Hydrothermal Synthesis of Rare-Earth Modified Titania: Influence on Phase Composition, Optical Properties, and Photocatalytic Activity

“…To calculate the relative activity of our samples, we used data from Table 3 , Table 4 and Table 5 . The data for P25 activity was taken from Karmaoui et al [ 58 ] for liquid-solid activity and from Tobaldi et al [ 39 ] for gas-solid photocatalytic activity measurement using NO x as a model pollutant. Activity of P25 is also included in Table 3 , Table 4 and Table 5 , which were used to plot the histograms in Figure 9 and Figure 10 .…”