Influence of the photoluminescence property of carbon nanodots on the reduction of silver ions

Carbon nanodots have been demonstrated to be an effective reducing agent in fabricating silver nanoparticles. In this study, the dependence of reduction efficiency of the CDs on the irradiation wavelength and their photoluminescence property is investigated. We find that the CDs excited by short wavelength light shows much higher photoreducibility than those excited by longer wavelength irradiation, although their PL intensity might be about the same. By analyzing the PL and the time-resolved PL property of the formed CDs-Ag NPs composites we find that, when the CDs are excited, there are two kinds of recombination path ways of the carriers contributing to their photoluminescence: the direct excitation of surface states, and the excited electrons from carbonic-core transferred to the surface states; only the electrons originates from the intrinsic carbonic-core excited by short wavelength can reduce the Ag ions, while those originates from the direct excitation of the surface states by long wavelength light are ineffective. The proposed reduction kinetics of Ag ions is significant to understand the photoreduction property of the CDs.