Size effect of silver nanoparticles on the luminescence properties of nearby carbon dots

Abstract

To know the effect of localized surface plasmon resonance (LSPR), on the luminescence of the nearby fluorophore shell, silver nanoparticles (Ag NPs) and a core-shell nanoconjugate Ag@SiO2NPs have been synthesized and interaction with carbon dots (CDs) is studied by fluorescence spectroscopy and time-correlated single photon counting (TCSPC). In the present study, we have demonstrated the excitation energy transfer (EET) from carbon dots (CDs) to the uncoated silver nanoparticles and SiO2 coated silver nanoparticles (Ag@SiO2NPs). Spectral overlap between the emission spectrum of CDs and localized surface plasmon resonance of Ag NPs results in PL quenching of CDs. A more significant spectral overlap between the emission spectrum of CDs and localized surface plasmon resonance of Ag@SiO2 NPs result in drastic increase PL quenching. In addition, the PL lifetime of CDs is shortened more when the coating was done the three different size bare Ag NPs. The origin of this PL quenching has been rationalized on the basis of increased nonradiative decay rate due to excitation energy transfer from CDs to Ag NPs surface. The observed energy-transfer efficiency correlates well with the nanometal surface energy transfer theory with 1/d4 distance dependence rster resonance energy transfer theory. Finally, the energy-transfer efficiency values obtained from experiment have been used to calculate the distance between CDs and surface of uncoated and SiO2 coated Ag NPs.