Sensitivity of (5,5) SWSiCNTs and SWSiCNTs with Stone-Wales Defects toward Hazardous Molecules

In this work, adsorption of five types of gas (HCHO, CO, HCN, NH3, and N2H4) onto (5,5) single-walled SiCNTs (SWSiCNTs) and (5,5) SWSiCNTs with two types of Stone-Wales defects (SWDs) has been investigated through a density function theory based first-principles method. The detection limit and adsorption capacity of SWSiCNTs to gas molecules were addressed in detail. The pristine (5,5) SWSiCNT was found to be highly sensitive to HCHO, CO, and HCN, whereas it cannot effectively detect NH3 or N2H4. The (5,5) SWSiCNT with an SWD by a 180 degrees rotation of a SiC unit (SWD2) significantly improves the detection limit of NH3 and N2H4 in terms of charge transfer and band gap. Small binding energies between NH3 (N2H4) and the SWD2-SWSiCNT facilitate desorption of the two gas molecules from the SWD2-SWSiCNT at ambient temperature and enhance the reusability of the sensor. The band gap of the SWSiCNTs narrows with the increase of concentration of HCHO, CO, and HCN. The adsorption capacity of the SWSiCNTs is about 30% for HCHO, CO, and HCN, respectively.