Reversible/Irreversible Photobleaching of Fluorescent Surface Defects of SiC Quantum Dots: Mechanism and Sensing of Solar UV Irradiation

摘要： Knowledge about photobleaching properties of the fluorescent surface defects of the semiconductor quantum dots (QDs) is crucial for their applications. Here, the photobleaching properties of the fluorescent surface defects of the colloidal 3C-SiC QDs are reported. The combined experimental and theoretical study reveals that the observed violet fluorescence at around 392 nm stems from the carboxylic acid group-related surface defects. When the SiC QDs are exposed to the UV irradiation, the 392 nm fluorescent surface defects show both reversible and irreversible photobleaching, whereas the 438 nm fluorescent surface defects show only irreversible photobleaching. The photochemical mechanisms dominating these phenomena are explored. The photobleaching property of the SiC QDs is utilized to detect the solar UV irradiation with high accuracy. The photobleaching of the SiC QDs is highly sensitive to the hydrogen or metal ion concentration in the colloid solution. These findings deepen the understanding of the properties of the fluorescent surface defects of the SiC QDs and pave the way for their applications in sensing.