Ultralong Room-Temperature Phosphorescence of Silicon-Based Pure Organic Crystal for Oxygen Sensing

Abstract

Quantitative oxygen detection is of great importance in biological fields, complex environments, and chemical process engineering. Due to the high sensitivity and rapid response of long-lived phosphorescence to oxygen, pure organic room-temperature phosphorescence (RTP) for oxygen detection has recently attracted considerable interest. However, to simultaneously achieve ultralong phosphorescence at room temperature and quantitative oxygen detection from pure organic crystals is difficult. Tight packing to restrict nonradiative decay is not apt to allow oxygen diffusion for sensing. Reported herein is an exceptional example, that is, a crystal of simple carbazole molecules that bridges with an ethoxysilane (DCzC2OSi) and is capable of oxygen sensing with remarkable sensitivity. Photophysical studies and single-crystal structure analysis reveal that DCzC2OSi crystals display ultralong RTP and suitable oxygen diffusion channels from its butterfly-like tetrahedron geometry. Further comparisons with the crystals of CzC2OH and DCzSi verify the important roles of silicon and ethoxy groups of DCzC2OSi for both enhanced phosphorescence lifetime and oxygen sensitivity. When the crystals of DCzC2OSi were doped into polymer, the lifetime-based oxygen sensor exhibited high KSV (5.308 kPa-1) with full reversibility, which is attractive for the development of practical oxygen sensors from pure organic crystals.