Gold nanoparticles with stable yellow-green luminescence

Gold nanoparticles (NPs) coated with 6-mercaptopurine-9-β-Dribofuranoside (6-MPR) have been synthesised in aqueous media by replacement of the original citrate stabiliser. Unlike virtually all other Au nano-colloids, the resulting 6-MPR-Au NPs revealed fairly strong photoluminescence with emission maximum at 580 nm and a quantum yield of 6%. The luminescence slowly blue-shifts to 514 nm after several months of aging. Spectroscopic data indicate that the photoluminescence originates from the formation of a complex between gold ions and 6-MPR during the nucleation stage on the surface of the Au NPs, creating the stabilising shell. Au(III), in the presence of pure 6-MPR in aqueous solution has been found to form an Au(6-MPR)2 complex using the Job's variation method. The presence of Au core considerably enhances the stability of the surface complex, although has little effect on other spectroscopic characteristics. Produced luminescent Au NPs can be used as a convenient model system for biomedical and sensor applications of nanoparticles.