Femtosecond transient absorption spectroscopy of maghemite nanoparticles loaded with gold nanoparticles

Photocatalytic water splitting is very useful for solar energy conversion. Iron oxides are attracting a lot of interests due to absorption in the visible region. However, iron oxides have poor conductivity. As one of solutions, the photocatalytic performance may be enhanced with loaded gold nanoparticles (Au-NP) by the characteristic optical absorption and the charge trapping nature. In this study, hybrid material of maghemite (γ-Fe2O3) and Au-NP (denoted as Au-Fe2O3) was prepared and the photo-generated carrier dynamics was revealed by femtosecond transient absorption (TA) spectroscopy. The hybrid material was prepared by mixing maghemite powder into 40 nm Au-NP aqueous solution. TA decay of Au-Fe2O3 indicates faster decay and suggests occurrence of hole transfer from maghemite to Au-NP, which can suppress the charge recombination and may result in enhancement of the photocatalytic reactivity.