Probing the inhomogeneity and intermediates in the photosensitized degradation of rhodamine B by Ag3PO4 nanoparticles from an ensemble to a single molecule approach

Abstract

The photoinduced dynamics related to the degradation of a surface adsorbate by a semiconductive catalyst is critical for understanding the photocatalytic mechanism and improving the catalytic property of nanoscale materials. Herein, we report the investigation of the inhomogeneous interactions between Ag₃PO₄ nanoparticles and rhodamine B (RhB), and the direct observation of the intermediates generated in the photodegradation of RhB, using ensemble-averaged as well as single-molecule time-resolved fluorescence spectroscopies. The results demonstrate the existence of electron injection from RhB into the conduction band of Ag₃PO₄ and the formation of a deethylation intermediate before the subsequent degradation process. The fluorescence diversity both in lifetime and intensity fluctuation indicates an inhomogeneous interfacial interaction between the RhB molecule and Ag₃PO₄ nanoparticle with surface heterogeneity. Based on the lifetime distribution, the duration time of single-molecule events and the related dynamical analysis, it was revealed that the RhB molecule adsorbed on the active site of the Ag₃PO₄ nanoparticle has a higher injection efficiency and better photocatalytic activity. Moreover, the lifetime evolution derived from a subsection of the single-molecule emission trajectories proved that the electron injection occurred prior to the degradation through the attack of free radical O₂˙⁻. These findings provide new insights into the heterogeneous interactions and dynamical information of the photosensitized degradation in an adsorbate/semiconductor catalyst.