Directed assembly and in situ manipulation of semiconductor quantum dots in liquid crystal matrices

The ability to control and direct self-assembly of nanostructures into specific geometries with new functionalities, while preserving their original optical and electronic properties, is an attractive research endeavor. We have fabricated liquid crystal (LC) based matrices into which chemically synthesized nanostructures of varied morphologies and compositions are uniformly dispersed. Using high resolution spatiallyand time-resolved scanning photoluminescence (PL) measurements, we have demonstrated directed nanoparticle assembly and manipulation in situ. This includes (a) directional assembly and electric field modulated re-orientation of disk-shaped gallium selenide nanoparticles using a nematic LC matrix, and (b) spectral modulation of chemically synthesized core shell CdSe/ZnS quantum dots (QDs) embedded in a cholesteric liquid crystal (CLC) matrix. Our work opens up the possibility of designing new QD based optical devices where spatial control of orientation, wavelength and polarization of the embedded QDs would allow great flexibility and added functionalities.