Water-soluble Ag2Te Quantum Dots with Emission in the Second Near-infrared Window

Quantum dots (QDs) have a wide range of applications in the field of biomedicine due to their unique optical properties. Ag2Te, as a member of group I-VI. quantum dots, has the advantages of low biological toxicity and narrow band gap, which has attracted the attention of scholars at home and abroad. But currently there are few methods for synthesizing water-soluble Ag2Te quantum dots, and the tunable fluorescence emission wavelength range is limited. This paper presented a new method of preparing water-soluble Ag2Te quantum dots with fluorescence emission in the second near-infrared window (NIR-II). This method applied silver nitrate as the silver source and N-acetyl-L-cysteine as the ligand. Sodium tellurite was reduced with sodium borohydride to obtain the tellurium source. The reaction condition was mild, such as room temperature, atmospheric atmosphere, and no toxic organic compounds were involved. Moreover, through cationic treatment, the surface defects of Ag2Te QDs were passivated and ultra-small water-soluble Ag2Te quantum dots with uniform size could be obtained. The fluorescence emission was centered at 1160 nm with a quantum yield of 8.0% (using IR26 dye as reference) . The Ag2Te quantum dots synthesized by this method had good biocompatibility, and obvious near-infrared fluorescence could be observed after QDs being injected into mice, showing potential for further biological applications.