Facile synthesis of luminescent silver nanoparticles and fluorescence interactions with blue-emitting polyarylene ether nitrile

In this work, fluorescent silver nanoparticles were synthesized in an organic phase via a facile one-step reaction. Their fluorescence emission is dependent on the excitation wavelength and can be effectively enhanced by a blue emitting intrinsic fluorescent polymer called polyarylene ether nitrile (PEN) via a resonance energy transfer process, which is confirmed by the time-correlated photoluminescence decay measurement and steady-state fluorescence spectroscopy. Specifically, luminescent Ag nanoparticles were synthesized by reducing silver nitrate (AgNO3) with polyvinylpyrrolidone (PVP) in N,N-dimethylformamide (DMF) solvent under a nitrogen atmosphere. It was found that obvious surface plasmon resonance combined with weak fluorescence under UV irradiation was observed from as-synthesized Ag nanoparticle stock solution. The larger sized silver nanoparticles (Ag NPs, 20 +/- 4 nm) were responsible for the plasmonic extinction peak at 415 nm, while the weak fluorescence emission at around 550 nm was attributed to the presence of ultra-small silver nanostructures. Furthermore, the dramatically enhanced fluorescence was observed from smaller Ag nanoparticles (6 +/- 2 nm) in the supernatant by removing the excess large sized Ag nanoparticles via high speed centrifugation. More interestingly, the purified smaller Ag nanoparticles showed an excitation wavelength dependent fluorescence emission profile, and their fluorescence under appropriate excitation can be further enhanced via the resonance energy transfer process from the energy donor of a blue emitting aromatic polymer that shows good spectral overlap with luminescent silver nanoparticles.