A quinoxaline-modified coumarin fluorescent probe for sulfur dioxide detection and preparation of PVA hydrogel sensor

Abstract

Sulfur dioxide (SO₂) and its sulfite derivatives pose severe threats to environmental safety and public health through oxidative stress induction. To address the critical need for on-site SO₂ detection technologies, we rationally designed a novel 1,4-diethyl-decahydro-quinoxaline (DQ)-modified coumarin fluorescent probe (DQC) with dual-responsive sensing capabilities. The DQ modification induced a significant hypsochromic shift in emission wavelength (>100 nm) while enabling ratiometric colorimetric detection – a critical advancement overcoming conventional single-signal limitations. Subsequently, DQC probes were blended into polyvinyl alcohol (PVA) to construct portable hydrogel sensors through an optimized crosslinking scheme (DQC@PVA). The results showed that DQC@PVA achieved rapid SO₂ detection within 5 seconds through a unique dual-response mechanism: (1) fluorescence emission switching through nucleophilic addition induced electron redistribution (λ_em = 650 nm → 550 nm), (2) visible color change from blue to yellow-green under ambient light. The probe demonstrates exceptional selectivity over competing reactive species (detection limit = 0.28 μM) and Field validation confirmed its utility for direct visual monitoring of atmospheric SO₂ levels without instrumentation. This work establishes a new paradigm in environmental sensing by integrating molecular probe design with functional material engineering, providing an effective solution for ecological protection and air quality management.