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Uncovering the underlying kinetics mechanism of the charge carrier during the transfer process is of fundamental importance in pursuing outstanding photocatalytic activity. However, it still remains a challenge owing to the rapid reaction rate of the charge carrier on the surface of photocatalysts. Here, in situ single-molecule fluorescence microscopy is employed to study the photoelectron-transfer kinetics in real time for an individual TiO2-tipped carbon nanotube (TiO2-tipped CNT) using a redox-responsive fluorogenic probe. A visual transport process for electron transfer from TiO2 nanoparticles to CNT is obviously observed via single-molecule fluorescence imaging. Based on the fluorescent product formation rate, the kinetics information of the photoelectron-transfer process can be obtained. The kinetics analysis results show that heterogeneity of catalytic activity caused by the photoelectron reactive sites exists in an individual TiO2-tipped CNT heterostructure, which is always masked in the ensemble measurement. After applying an adaptive high-resolution algorithm, which considers temporal and spatial factors into consideration simultaneously, the dynamic heterogeneity of special location on CNT within the TiO2-tipped CNT heterostructure in product formation is revealed with 40 nm spatial resolution. Moreover, we prove that the photoelectron-transfer distance on CNT can be up to 16.82 μm. These results give a deep insight into the kinetics information of the photoelectron-transfer process and a policy toward designing better photocatalysts.

Gold (Au) electrodes are one of the most ideal electrodes and are extensively used to construct electrochemical biological detection platforms. The electrode–molecule interface between the Au electrode and biomolecules is critical to the stability and efficiency of the detection platform. However, traditional Au–sulfur (Au–S) interfaces experience distortion due to high levels of glutathione (GSH) and other biological thiols in biological samples as well as a high charge barrier when electrons are injected into the biomolecule from the Au electrode. In view of the higher bonding energy of Au–selenium (Au–Se) bonds than those of Au–S bonds and the elevated Fermi energy of the Au electrodes when Au–Se bonds are formed instead of Au–S bonds at the interface between the electrodes and molecules, we establish a new type of electrochemical platform based on the Au–Se interface (Au–Se electrochemical platform) for high-fidelity biological detection. Compared with that of the electrochemical platform based on the Au–S interface (Au–S electrochemical platform), the Au–Se electrochemical platform shows a higher charge transfer rate and excellent stability in millimolar levels of GSH. The Au–Se electrochemical platform supplies an ideal solution for accurate biological detection and has great potential in biomedical detection applications.

We constructed a single-molecule fluorescence imaging technique to monitor the spatiotemporal distribution of the hydroxyl radical (•OH) on TiO2-attached multiwalled carbon nanotubes (TiO2-MWCNTs) in aqueous. We found the heterogeneous distribution of •OH is closely related to the composition and heterostructure of the catalysts. The dynamic •OH production rate was evaluated by counting the single-molecule fluorescent bursts. We further confirmed the production of •OH on TiO2-MWCNTs mainly occurred via electron reduction during the aqueous photocatalytic process. Our study reveals the mechanism of reactive oxygen species involved photocatalytic reaction and guides the design of advanced semiconductor photocatalysts.