Liquid-crystal gel-dispersed quantum dots: Reversible modulation of photoluminescence intensity using an electric field

A general approach of using the electric field-controllable liquid-crystal orientation to modulate the photoluminescence intensity of quantum dots is presented. Liquid-crystal gel-dispersed quantum dots of CdSe/ZnS were prepared using a cholesteric liquid crystal containing either a self-assembled physical network or a covalently crosslinked polymer. The reversible change in liquid-crystal orientational state in response to an applied voltage changes the internal scattering of the excitation light and thus the excitation of the dispersed quantum dots. This leads to an electrically switchable fluorescence emission of CdSe/ZnS in two different ways: high intensity at field-off and low intensity at field-on state, and vice versa.