Longitudinal Dipole Modes of AuNRs for Photocatalytic Enhancement of Ultrathin Rutile TiO2 Nanosheets

Rutile-phase titanium dioxide (TiO2) nanosheets with a thickness of 4 nm were successfully prepared. Excellent visible light catalytic degradation effects have been observed from these nanosheets. To enhance the catalytic performance, aurum nanorods (AuNRs) were incorporated with the TiO2 nanosheets. Compared with sole TiO2 nanosheets, the Janus structures of the combined TiO2 and AuNRs (TiO2@AuNRs) showed three times the reaction rate for the degradation of Rhodamine B under visible and near-infrared light (> 410 nm, 300 W). This is attributed to the wide response range of AuNRs, which is demonstrated by the absorption spectra of the AuNRs colloids. The introduction of AuNRs with different aspect ratios in TiO2@AuNRs revealed better catalytic activities for AuNRs with larger aspect ratios. To study the physical mechanism of photocatalytic enhancement, the finite difference time domain method has been performed to simulate the optical properties of TiO2@AuNRs. The simulation results showed that the photocatalytic improvement of TiO2@AuNRs was caused by the longitudinal localized surface plasmon resonance mode of AuNR. Through the excitation of the longitudinal mode, 40 times enhancement of the near-field intensity can be observed. The results indicate that AuNRs can be used to improve the photocatalytic activity of TiO2 nanosheets through the injection of hot electrons from AuNR into TiO2.