Plasmon-Assisted Enhancement and Tuning of Optical Properties in β-In<inf>2</inf>S<inf>3</inf> Quantum Dots

Exciton-plasmon coupling can significantly modify the spectral response of semiconductor quantum dots in a metal nanoparticle-semiconductor complex system. β-In2S3 quantum dots of size ∼3 nm and Ag nanospheres of size ∼100 nm were synthesized by chemical route and coated over glass substrates. In the strong coupling regime, the plasmons are shown to mediate indirect Coulomb interaction between the quantum dots. In the proximity of Ag plasmons, the excitonic binding energy of the β-In2S3 quantum dots increases by ∼500 meV, indicating that the interaction potential between the quantum dots is positive and repulsive in nature. This interaction also leads to strong coupling of the defect levels in the SQD complex. The defect emission wavelength can be enhanced by an order of 102 or shifted from red region (∼650 nm) to green (∼550 nm) by controlling the plasmon-induced defect level coupling. The experimental observation demonstrates one of the theoretically predicted consequences of exciton-plasmon interaction. This work demonstrates the possibility of harnessing the potential of the two complimentary systems (semiconductor quantum dots and metal nanoparticles) to achieve controllable emission and absorption properties for fabrication of nano plasmonic devices.