In situ photoreduced silver nanoparticles on cysteine: An insight into the origin of chirality

摘要

An experiment was conducted to demonstrate that Ag ~+ complexes with L- or D-isomers of cysteine (Ag ~+ Cys) could be in situ photoreduced to form Ag NPs without the assistant of any other reducing agents or protecting ligands. Ag ~+ Cys complexes of defined stoichiometry were first formed by mixing different amounts of AgNO _3 and L or D-cysteine with final concentrations of 0.5 mm. Upon mixing, the formation of Ag ~+ Cys complexes at r=1.1 was instantaneous, witnessed from both a dramatic increase in the UV absorbance and the significant CD signals of Ag ~+ Cys complexes. The most interesting is that the in situ photoreduction of Ag ~+ bound to cysteine generated an intense CD signal around the SPR frequency of Ag NPs centered at about λ=405 nm, which is completely different from that of Ag ~+ Cys complexes and that of presynthesized large Ag NPs modified with cysteines.