## 4 Reliable and Highly Sensitive Gas-Sensitive Materials for Intelligent Monitoring
### 2D (Two-Dimensional) Material Sensor Material
RCTF sensors are highly sensitive and selective to hydrogen sulfide, but like most 2D materials, their recovery is slow. Compared to RCTF sensors, DCTF sensors offer significant improvements in selectivity, sensitivity, and recovery speed. The HTF sensor shows that the short thermal pulse is very effective in improving the recovery process of the gas sensor, and the recovery speed is the fastest. Non-ohmic contact between the gold electrode and the tellurium sheet can effectively improve gas sensing performance. Doping the transition metal (TMs) up to the InN can effectively control the electronic behavior of the InN monolayers, indicating that the doping system can significantly improve chemical activity and electron mobility [105]. [PERSON] et al. [94] investigated the application of doping Ru metal into the InN monolayer (Ru-InN). The results (Table 3) show that Ru-InN monolayer has strong adsorption behavior of SO\({}_{2}\), SOF\({}_{2}\), and SO\({}_{2}\)F\({}_{2}\) gases and can identify types of gases, indicating strong chemical interaction. Transition metal dihalides (TMDs) have received great attention as sensor materials due to their high detection capability, low power consumption, and unique electrical properties [106]. [PERSON] et al. [107] selected the transition metal Pt-doped WSe\({}_{2}\) monolayer and analyzed the adsorption of the decomposition gas on the Ptn-WSe\({}_{2}\) (\(n\) = 1, 2, 3) monolayer based on first principles theory. Pt-WSe\({}_{2}\) and  
Phosphate has stronger sensing properties compared to graphene and molybdenum disulfide. [PERSON] et al. [95] studied the possibility of phosphate in SF\({}_{6}\) decomposition gas sensors. The results (Table 3) show that the adsorption energy of SO\({}_{2}\) by phosphate is significantly higher than that of H\({}_{2}\)S, and SO\({}_{2}\) molecules can be easily adsorbed to the phosphorus surface for desorption. The closest atomic distance between the gas and phosphate is greater than the sum of the covalent radii of the corresponding atoms, which shows that the adsorption of these three gases is physical adsorption. Recently, a series of 2D metal phosphides, including InP\({}_{3}\)[109], GeP\({}_{3}\)[110], and CaP\({}_{3}\)[111], were found to have high carrier mobility. In particular, it has been reported that the InP\({}_{3}\) monolayer has high chemical stability, excellent indirect semiconductor performance, and good optical performance [109], which makes it a novel nanomaterial for applications. [PERSON] et al. [96] investigated the adsorption properties of the InP\({}_{3}\) monolayer for SO\({}_{2}\), SOF\({}_{2}\), and SO\({}_{2}\)F\({}_{2}\). The result of the adsorption performance (Table 3) for the three gases is SO\({}_{2}\)\(>\) SOF\({}_{2}\)\(>\) SO\({}_{2}\)F\({}_{2}\). After gas adsorption, the electronic behavior of the InP\({}_{3}\) monolayer will be changed, resulting in the redistribution of electrons and a change in band gap and conductivity. In Figure 8c, the desorption time of SO\({}_{2}\)F\({}_{2}\) is very short at room temperature, indicating the weak interaction between SO\({}_{2}\)F\({}_{2}\) and InP\({}_{3}\). The InP\({}_{3}\) monolayer is a good sensor material for SO\({}_{2}\) and SOF\({}_{2}\) detection. Detectable response and ideal desorption characteristics allow InP\({}_{3}\) monolayers to operate at room temperature. Antimonene is a new two-dimensional (2D) material, with higher air stability, higher carrier mobility, wider adjustable band gap, and a more curved structure than phosphorene [112; 113]. It is also considered an ideal material (Table 3) and showed better gas transduction of SbP to SO\({}_{2}\) than other gas molecule monolayers. Orbital hybridization is generated by the P orbitals of S and O atoms and the P orbitals of Sb and P atoms, which allows for strong interactions between SbP and SO\({}_{2}\). After comparing and analyzing the coefficients of different substrates, SbP is suitable for the sensing of SO\({}_{2}\). Antimonene inevitably introduces point defects during the synthesis process.