Recent progress in the small-molecule fluorescent probes for the detection of sulfur dioxide derivatives (HSO3-/SO32-).

Sulfur dioxide (SO2) had been recognized as an environmental pollutant produced from industrial processes. SO2 is water soluble and forms hydrated SO2 (SO2·H2O), bisulfite ion (HSO3-), and sulfite ion (SO32-) upon dissolution in water. SO2 could be also produced endogenously from sulfur-containing amino acids l-cysteine in mammals. Endogenous SO2 can maintain the balance of biological sulfur and redox equilibrium in vivo, regulate blood insulin levels and reduce blood pressure. Excess intake of exogenous SO2 can result in respiratory diseases, cardiovascular diseases and neurological disorders. As a result, fluorescent probes to detect HSO3-/SO32- have attracted great attention in recent years. Herein, a general overview was provided with the aim to highlight the typical examples of the HSO3-/SO32- fluorescent probes reported since 2010, especially those in the past five years. We have classified HSO3-/SO32- fluorescent probes through different chemical reaction mechanisms and wish this review will give some help to the researchers in this field.