One-pot synthesis of Au/Ag bimetallic nanoparticles to modulate the emission of CdSe/CdS quantum dots

In this work, gold/silver bimetallic nanoparticles (Au/Ag NPs) have been synthesized via a facile one-pot protocol involving co-reduction of chloroauric acid and silver nitrate with N, N-dimethylformamide (DMF) solvent in the presence of water soluble polyvinylpyrrolidone (PVP). The morphology of obtained Au/Ag NPs can be readily modified by changing the reaction time and relative concentration ratio of the gold/silver precursors. Subsequently, the synthesized Au/Ag NPs have been employed to modulate the fluorescent emission of CdSe/CdS quantum dots (QD) in the solution phase on the basis of plasmon controlled fluorescence. The experimental results demonstrated that the fluorescent emission of CdSe/CdS QD can be either obviously quenched or enhanced, depending on the spectral overlap and local distance control between CdSe/CdS QD and Au/Ag bimetallic NPs. Specifically, the as-synthesized Au/Ag NPs significantly quenched the fluorescent emission of CdSe/CdS QD and the quenching effect was enhanced when the plasmonic wavelength of Au/Ag NPs was tuned towards the fluorescent emission wavelength of the CdSe/CdS QD. On the contrary, the fluorescent emission of CdSe/CdS QD can be obviously enhanced in the presence of SiO2 coated Au/Ag NPs with appropriate layer thickness.