Tailoring Thiazole Decorated Polymer with Benzoselenadiazole for Enhanced SO2 Sensing

Sulfur dioxide (SO₂) is a hazardous pollutant that significantly poses a risk to human health and the environment. However, the development of SO₂ sensors that work at room temperature has been significantly hindered due to their inadequate recovery properties. In this context, we have introduced a thiazole decorated conjugated polymer (BBT) for the detection of SO₂ at 25 °C. Moreover, we improve the SO₂ sensing performance at 25 °C by modifying the backbone of the BBT polymer with a benzo[2,1,3]selenadiazole ring (BSe), resulting in BBTBSe. The BBTBSe sensor exhibits a 4.3× higher response compared to the BBT sensor. When exposed to 100 ppm of SO₂, the BBTBSe and BBT sensors show response values (R_g/R_a) of 199.4 and 45.7, respectively, with a rapid response/recovery time of 60/70 s at 25 °C. Additionally, both the BBTBSe and BBT sensors show excellent selectivity to SO₂ in comparison to other gases, with a selectivity factor greater than 5.3. The BBTBSe sensor exhibits a linear behavior in the concentration range of 1–50 ppm, with limit of detection (LOD) and limit of qualification (LOQ) values of 0.23 and 0.76 ppb, respectively. The BBTBSe sensor also exhibits complete reversibility and repeatability with prolonged stability. Additionally, a possible mechanism for SO₂ sensing has been proposed, based on acid–base and dipole–dipole interactions between the lone pair of nitrogen and SO₂ gas molecules. As a result, we believe that the results of the BBTBSe sensor offer a significant opportunity to develop a sensor with high sensitivity and selectivity, expanding its application in medical diagnosis and environmental pollution monitoring.