Electrically Switchable Anisometric Carbon Quantum Dots Exhibiting Linearly Polarized Photoluminescence: Syntheses, Anisotropic Properties, and Facile Control of Uniaxial Orientation

Carbon quantum dots (CQDs) have been extensively explored in diverse fields because of their exceptional features. The nanometric particles with photoluminescence (PL) benefit various optical and photonic applications. However, the majority of previous reports have mainly focused on either unpolarized or circular-polarized (CP) PL. Linearly polarized (LP) emission of CQDs is limited mainly because of their isometric shape and difficulties in macroscopic orientation control. Herein, we report syntheses of anisometric CQDs and facile control of the uniaxial orientation on a macroscopic scale, which results in linearly polarized photoluminescence (LP-PL). The anisometric CQDs are synthesized from rigid-rod-shaped precursors and evenly dispersed in the rod-like liquid crystal (LC) host. As-synthesized CQDs exhibit a PL quantum yield as high as 35% in chloroform. In addition to uniform alignment, facile directional switching of the elongated CQD is established by employing the electrical responsiveness of the CQD and host LC. Therefore, the dichroic photophysical properties of anisometric CQDs have been beneficially adopted for fabrications of polarization-sensitive and electrically switchable PL devices. Also, anisometric CQDs are embedded in polymer films with molecular orientational patterns and clearly recognized by LP-PL.

Automated summary

This study reports the synthesis of anisometric carbon quantum dots (CQDs) and the macroscopic control of their uniaxial orientation, resulting in linearly polarized photoluminescence (LP-PL). The as-synthesized CQDs exhibit a high PL quantum yield. The elongated CQDs can be directionally switched using the electrical responsiveness of the CQDs and the liquid crystal host. The anisometric CQDs have been successfully adopted for the fabrication of polarization-sensitive and electrically switchable PL devices.