Surfactant-Induced Modulation of Nanometal Surface Energy Transfer from Silicon Quantum Dots to Silver Nanoparticles

In the present study, we have demonstrated the excitation energy transfer (EET) from silicon quantum dots (Si QDs) to silver nanoparticles (Ag NPs) and its modulation in the presence of cetyltrimethylammonium bromide (CTAB) surfactant by means of steady-state and time-resolved photoluminescence (PL) spectroscopy. Significant spectral overlap between the emission spectrum of Si QDs and localized surface plasmon resonance of Ag NPs results in a substantial amount of PL quenching of Si QDs. In addition, the PL lifetime of Si QDs is shortened in the presence of 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 Si QDs to Ag NPs surface. The observed energy-transfer efficiency correlates well with the nanometal surface energy transfer theory with a 1/d(4) distance dependence rather than conventional Forster resonance energy transfer theory. It has also been observed that the EET efficiency drastically reduces in the presence of 0.5 mM CTAB. Dynamic light scattering and single-particle PL microscopy results indicate the formation of large surfactant-induced aggregates of Ag NPs. Finally, the energy-transfer efficiency values obtained from experiment have been used to calculate the distance between Si QDs and Ag NPs in the absence and presence of CTAB, which correlates well with the proposed model.