Enhanced sensing of SO3, SO2, HCN, and CO2 gases with [2,2':5',2''-Terthiophene]-3',4'-diamine: A theoretical study

In this study, a theoretical investigation employing the DFT/B3LYP-D3/6-31+G(d,p) method is used to examine the possible gas sensing applications of [2,2':5',2''-Terthiophene]-3',4'-diamine (DT) towards the poisonous gases like SO3, SO2, HCN, and CO2. The adsorption energy (ΔEads) analysis and QTAIM, NCI, and IRI results show that SO3 chemisorbs on DT, whereas other gases are physisorbed. The DT-SO2 complex exhibits the highest ΔEads and lowest energy gap (Eg), resulting in a lower recovery time (τ) and a high work function (Φ) value, leading to a significant variation in conductance. In contrast, SO3, with the highest ΔEads, Eg, τ, and lowest conductivity, hinders the effective electrical signal transmission of DT for SO3 detection. DT's lack of selectivity for HCN and CO2 stems from inadequate ΔEads, insignificant Φ changes, and limited responsiveness to an external electric field. Consequently, the study highlights DT's particular effectiveness in sensing SO2 gas, underscoring its selectivity for SO2.