Resonant and non-resonant interaction of semiconductor quantum dots with plasmons localized in silver and zinc nanoparticles

Abstract

Optical properties of layered composite materials consisting of plasmonic nanostructures and semiconductor quantum dots (QDs) have been investigated both experimentally and theoretically. It was demonstrated that in the case of spectrally overlapping bands of plasmonic absorption and fluorescence of alloyed QDs placed directly onto silver island film, the fluorescent intensity increases. While in other samples with alloyed QDs the fluorescence was not sensitive to silver nanoparticles or even quenched by silver nanoparticles for core-shell QDs. That was explained by resonant and non-resonant interaction of QDs with the near fields of plasmonic structures. Measuring the fluorescence decay time, we observed a clear correlation between the fluorescence intensity of alloyed QDs and reducing fluorescent lifetime in the case of resonant interaction or the Purcell effect. The interaction between excitons in semiconductor material and plasmons in metal nanoparticle was explored also in the Zn-ZnO system via numerical modeling. This system is interesting because metal films may be easily created via magnetron sputtering on silica glass substrates and then fully or partially oxidized in the course of thermal annealing in air. Thus a core-shell nanostructure consisting of a semiconductor shell with promising chemical sensor properties (ZnO) and metallic core with the plasmon resonance in the same spectral region (Zn) will be created.