Abstract: Blue luminescent gold(Au) quantum dots(QDs) were facilely prepared through a one-pot synthesis at room temperature. The as prepared Au QDs were well water-soluble and biocompatable. The mean size of Au QDs is about 3.0 nm. Gold QDs colloids showed a considerable blue fluorescence emission at 430 nm under excitation of 305 nm. Experimental results demonstrated that the addition of L-cysteine could significantly enhance the characteristic emission of Au QDs at 430 nm. Therein, a simple, rapid, sensitive detection of L-cysteine in aqueous solution was established. Under optimized conditions, the characteristic fluorescence intensity of Au QDs at 430 nm is linearly proportional to the concentration of L-cysteine in the range of 0.0 to 4.0×10-6 μmol/L and a detection limit as low as 5 nmol/L was obtained. The relative linear relationship coefficient is 0.9976. The relative standard deviation for 11 replicate detections of 2.0 μmol/L L-cysteine was 2.8%. In addition, this method also demonstrated a high selectivity to amino acids due to the strong affinity of L-cysteine to gold atoms.

Key words: Gold quantum dots, fluorescence, biosensor, L-cysteine