Synthesis, Characterization, and Photoactivity of Ta2O5-Grafted SiO2 Nanoparticles

Herein, we discuss the synthesis as well as material and photochemical characterization of nanometer-sized Ta2O5 decorated, in a controlled fashion, on top of 20 nm diameter SiO2 particles to yield a composite oxide with a tunable band-gap width. Particular emphasis is paid to control of particle size, and control of the distribution of the overlying oxide. The nanoscale dimension imparts a high surface area and introduces quantum confinement effects that displace the conduction band more negatively and the valence band more positively on the electrochemical scale of potentials. This band shift results in an increase of the number of possible participants in photocatalytic reactions. The band shift is shown to result in an increase in driving force for thermodynamically feasible reactions. By decorating SiO2 with smaller-sized Ta2O5, the interplay of the Lewis acidity of SiO2 and the contact area between Ta2O5 and SiO2 is utilized to develop a photocatalyst with higher photoactivity than pure Ta2O5.