Microscopic Models of Hybrid Nanocrystal Superstructures: photonic properties

We investigate the optical properties of hybrid superstructures composed of metal and semiconductor nanoparticles (NPs), and bio-linkers/polymers. Our study is inspired by recent experiments on bio-conjugated semiconductor-metal NP complexes and their potential applications as sensors. Metal NPs can quench semiconductor NP photoluminescence (PL). However, a plasmon enhancement can be achieved by organizing many Au NPs into a spherical or cylindrical shell around a CdTe NP. We compute electromagnetic fields induced in NP superstructures using a multipole expansion approach to describe the optical response of these complexes. Enhancement of CdTe emission can result from plasmon mediated enhancement of the excitation (Ag structures) or enhancement of the emission process (Au structures). The resultant optical response comes from a complex interplay of this enhancement and quenching and determines the potential applications of these superstructures.