A Ratio Fluorescent Sensor Based on Coumarin and Rhodamine for Sequential Detection of Aluminium Ion and Pyrophosphate and Its Applicability in Arabidopsis Thaliana

Abstract

A ratio fluorescent sensor N'-((E)-3-((E)-((3′, 6′-bis(diethylamino)-3-oxospiro[isoindoline-1, 9′-xanthen]-2-yl)imino)methyl)-2-hydroxy-5-methylbenzylidene)-7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide (I) based on the FRET mechanism was synthesized using coumarin as the donor and rhodamine as the receptor. Its structure was characterized by FT-IR, ¹H NMR, ¹³C NMR, and ESI-MS. The sensing performance of sensor I was studied using fluorescence spectrophotometry, and the detection mechanism was studied using density functional theory. The results indicated that in MeOH/H₂O medium, sensor I exhibits a significant fluorescence enhanced response to Al³⁺, with a detection limit of 5.8 × 10⁻⁷ mol/L. In addition, complex I-Al³⁺exhibits a significant fluorescence quenching response to PPi, with a detection limit of 3.7 × 10⁻⁷ mol/L, indicating that sensor I has high sensitivity and anti-interference ability for the recognition and detection of Al³⁺ and PPi. Through the analysis of complexation curves, it was found that the complexation ratio of sensor I to Al³⁺ was 1:1 and complex I-Al³⁺ to PPi was 2:1, and the cyclic response test could be performed stably for more than four times. The imaging results of Arabidopsis thaliana show that sensor I has low toxicity and good biocompatibility, which provides a way for the detection of Al³⁺ in plants.