Mesostructured composite materials with electrically tunable upconversion properties

摘要

A promising approach of designing mesostructured materials with novelphysical behavior is to combine unique optical and electronic properties ofsolid nanoparticles with long-range ordering and facile response of soft matterto weak external stimuli. Here we design, practically realize, and characterizeorientationally ordered nematic liquid crystalline dispersions of rod-likeupconversion nanoparticles. Boundary conditions on particle surfaces, definedthrough surface functionalization, promote spontaneous unidirectionalself-alignment of the dispersed rod-like nanoparticles, mechanically coupled tothe molecular ordering direction of the thermotropic nematic liquid crystalhost. As host is electrically switched at low voltages~ 1V, nanorods rotate,yielding tunable upconversion and polarized luminescence properties of thecomposite. We characterize spectral and polarization dependencies, explain themthrough invoking models of electrical switching and upconversion dependence oncrystalline matrices of nanorods, and discuss potential practical uses.