A ratiometric fluorescent probe with a large emission shift for the detection of sulfur dioxide derivatives in live cells, foods and plant.

Sulfur dioxide (SO₂) derivatives fulfill essential roles within food additives, specific physiological contexts, and plant development mechanisms, yet heightened exposure levels are associated with adverse effects on human health and plant viability. Thus, the ratiometric fluorescent probe SX-TPA was engineered for detecting SO₂ derivatives, boasting high sensitivity (detection limit: 0.201 μM), excellent selectivity and anti-interference capability, and rapid response. SX-TPA discriminates SO₂ derivatives specifically via Michael nucleophilic addition. This reaction disrupts the π-conjugation within the probe skeleton and blocks the intramolecular charge transfer (ICT) process, thus eliciting a marked emission shift (Δλ = 259 nm). Importantly, the SX-TPA exhibits outstanding imaging and detection capabilities even in complex real food samples, biological living cells, and the epidermal tissue of plant onions.