# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1903.02138