Green synthesis of gold nanoclusters using papaya juice for detection of l-lysine

Gold nanoclusters were rapid synthesized within 3 min at 120 °C by using papaya juice as a capping and reducing agent (P-AuNCs). The properties of the fluorescent probe were characterized by fluorescent spectroscopy, UV–vis spectroscopy, dynamic light scattering and transmission electron microscope. Based on the surface electron density increase-induced fluorescence enhancing principle, a high selective method for detection of l-lysine was developed with the as-prepared P-AuNCs coupling the fluorescence emission at 440 nm. The fluorescent probe showed high stability and good biocompatibility. Its fluorescence intensity was found to be linearly dependent on the l-lysine concentration in the range of 10.0 μmol/L to 1000.0 μmol/L (R2 = 0.969) with a limit of detection of 6.0 μmol/L. Furthermore, the P-AuNCs based approach was applied for monitoring the urine l-lysine contents, demonstrating great potential of fluorescent probes in real samples analysis.