Plasmon-exciton nanostructures, based on CdS quantum dots with exciton and trap state luminescence

Abstract

The study is devoted to the establishment of plexciton coupling manifestations in the luminescence of colloidal CdS quantum dots (3.7 nm), passivated with Oleic acid (OA) in mixtures with spherical silver nanoparticles (Ag NPs), coated with Oleylamine (OAm) with size of 10–15 nm. Mixtures of CdS QDs and Ag NPs in toluene, in which the associates formation occurs as a result of the π-staking and dipole-dipole interaction have been realized. The case of the simultaneous effect of plasmonic nanoparticles on exciton and trap state luminescence is considered. Under conditions of maximum overlap of Ag NPs extinction spectrum (415 nm) and exciton luminescence band, it was found that the exciton luminescence quenching (430 nm), accompanied by an decrease in its lifetime from 7.4 ns to 2.5 nm due to resonance energy transfer with an efficiency of 0.66 is dominant effect. At the same time, under conditions of weak plexciton coupling, caused by an insignificant overlap of Ag NPs plasmon band, an increase in the intensity of trap state luminescence (603 nm) by a factor of 1.8 with simultaneous decrease in its luminescence lifetime from 75 ns to 25 ns was observed due to the manifestation of the Purcell effect. The obtained results demonstrate the possibility of increasing the quantum yield of QDs trap state luminescence due to the Purcell effect.