A sensitive visual detection of thiamethoxam based on fluorescence resonance energy transfer from NH2-SiO2@CsPbBr3 to merocyanine configuration of spiropyran

The spiropyran (SP) compound is a typical photochromic compound. Its merocyanine configuration (MC) can accept energy and be excited by visible light, while the closed-loop configuration cannot. In this work, the SP was wrapped in beta-cyclodextrin (beta-CD-SP) firstly. When it was competitively replaced by thiamethoxam and dissociated out of beta-CD, it would be converted to MC, which could be excited by visible light around 550 nm to produce red fluorescence. Here, CsPbBr3 was selected as the energy donor based on the principle of fluorescence resonance energy transfer (FRET). In order to connect with beta-CD SP and improve its stability, CsPbBr3 was wrapped in mesoporous silica, and then the second wrapping was performed to block those mesopores and the amination reaction was carried out (NH2-SiO2@CsPbBr3). Subsequently, NH2-SiO2@CsPbBr3 with green fluorescence (506 nm) was used as the internal standard and excitation light source for MC, and the red fluorescence of MC was used as the response signal to construct a ratiometric fluorescence sensor. When thiamethoxam was added and excited by 365 nm ultraviolet light, the energy would be transferred from NH2-SiO2@CsPbBr3 (506 nm) that emitted green fluorescence to MC, which emitted red fluorescence. So, the fluorescence color changed from green to yellow to red with the addition of the thiamethoxam. This sensor was employed to detect thiamethoxam in soil and yam. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study utilized the properties of the photochromic compounds SP and MC, combined with the FRET principle and ratiometric fluorescence sensor technology, to construct a novel fluorescence sensor for detecting thiamethoxam.