A dual-mode subphthalocyanine-functionalized calix[4]arene based turn-off–on fluorescent sensor for selective detection of tebuconazole pesticide in food and water samples

Abstract

In this study, a novel subphthalocyanine-substituted calix[4]arene (Calix-Sub) fluorophore was designed and synthesized. Its structure was characterized by FT-IR, MALDI-TOF, ¹H-NMR, and elemental analyses. Calixarenes are promising sensors due to their rigid structures, complexation abilities, and selectivity, while subphthalocyanine provides strong fluorescence behaviour. The Calix-Sub sensor exhibited a “turn-off” fluorescence response toward Cu(II) ions and a “turn-on” response upon addition of tebuconazole pesticide, demonstrating its potential as an optical sensor. The system enabled quantification of tebuconazole in a linear range of 0.33–2.05 mmol L⁻¹ with a detection limit of 0.53 mmol L⁻¹. The sensor showed high selectivity and a clear fluorescence response toward tebuconazole over other metal ions and pesticides. Analytical parameters, including selectivity, precision, sensitivity, and recovery were optimized for environmental sample analysis.