Preparation of AgInS2 quantum dots and their application for trypsin detection

Water-soluble AgInS2 quantum dots were prepared by hot injection method using glutathione (GSH) as the stabilizer. The obtained AIS QDs were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, High-resolution transmission electron microscopy, Photoluminescence spectrometer, and Dynamic light scattering. The results showed AIS QDs prepared at pH = 7.03 of reaction solution were of the strongest fluorescent and about 2.8 nm in size. AIS QDs were used directly as the fluorescent probe; a method for the determination of trypsin content was established based on the fluorescence quenching effect of trypsin on AIS QDs. Under the optimal condition, good linear relationships between the fluorescence quenching efficiency of AIS QDs and trypsin concentration were obtained in the range of 0.0625-4 mu g mL(-1), 10-320 mu g mL(-1) and 0.2-1.6 mg.mL(-1), and the correlation coefficients were 0.994, 0.998 and 0.998, respectively. The detection limit was 0.4 mu g mL(-1). The average recovery percent of trypsin in urine was between 96.9% and 105.9%. The possible fluorescence quenching mechanism was discussed in detail and the dynamic quenching mechanism of light-induced electron transfer was proposed.