Fluorescence temperature sensing based on thermally activated singlet-triplet intersystem crossing in crystalline anthracene

TL;DR

This paper introduces a novel fluorescence temperature sensing method using anthracene crystals, based on the thermally activated singlet-triplet intersystem crossing, with the 2-0 transition serving as an effective temperature indicator.

Contribution

It reveals the mechanism behind the temperature-dependent fluorescence intensity ratio and demonstrates a new sensing approach based on this physical process.

Findings

The 2-0 transition intensity increases exponentially with temperature.

The intensity ratio γ2 provides the best temperature sensing performance.

The mechanism involves thermal coupling between T2 triplet and S1 singlet states.

Abstract

The temperature dependence of the steady-state fluorescence spectrum of anthracene crystals range from 300K to 500K had been investigated, which was in the temperature range of most tabletop laser-driven shock wave experiments. The interesting finding is that the fluorescence intensity of the 2-0 transition increases more rapidly than other transitions with the rising temperature. In particular, the transition intensity ratios {\gamma}n all shows a perfect exponential increasing curve, which can be used for fluorescence temperature sensing. The analysis of sensitivity {\eta} and random uncertainty {\Delta}T has demonstrated that the intensity ratio {\gamma}2 is the best comprehensive performance physical quantity for temperature sensing. The theoretical analysis and experimental results demonstrated that unusual intensity increasing of 2-0 transition was originated from the second excited triplet state T2, which was thermally coupled with the first excited singlet sate S1. In a word, we established a new fluorescence temperature sensing method based on the intensity ratio and clarified the mechanism of this method was the thermally activated singlet-triplet intersystem crossing.