## 4 Conclusions  
For the adsorption of a single gas molecule, Pt-doped graphene has strong interactions with SO\({}_{2}\), SOF\({}_{2}\) and SO\({}_{2}\)F\({}_{2}\). For SO\({}_{2}\) adsorption, the energy gap width \(E_{g}\) decrease, which may result in the decrease of conductivity of the system. Compared with SO\({}_{2}\), the \(E_{ads}\) for single SOF\({}_{2}\) adsorption was slightly smaller, but the \(Q_{T}\) was slightly larger and the \(E_{g}\) was also slightly higher, which proved that SOF\({}_{2}\) brings the smallest chemical interactions but still leads to the decrease of the conductivity. The adsorption of SO\({}_{2}\)F\({}_{2}\) is a strong chemisorption process and moreover, the bonds in gas molecule tend to be broken. The adsorption of SO\({}_{2}\)F\({}_{2}\) also brings conductivity decrease. For the adsorption of double gas molecules, the increase in the number of molecules does not obviously change the chemical interactions to some gas molecule but may have very small interactions with the second adsorbed molecule. When adsorbing double SO\({}_{2}\), the adsorption energy and charge transfer amount are significantly increased compared with single gas molecules, but those of the adsorption of 2 SOF\({}_{2}\) and 2 SO\({}_{2}\)F\({}_{2}\) had not change. For the adsorption of two different gas molecules, the interactions are quite different with one molecule adsorption and the conductivity decreases to varying degrees and the distribution of HOMO, LUMO orbitals transfer around the gas molecule with different degrees and the value of \(E_{g}\) experience different changes. Figure 10: Distribution of HOMO (red-green) and LUMO (blue-yellow) (**a**) before and after (**b**) SO\({}_{2}\) & SOF\({}_{2}\), (**c**) SO\({}_{2}\) & SO\({}_{2}\)F\({}_{2}\) and (**d**) SOF\({}_{2}\) & SO\({}_{2}\)F\({}_{2}\) adsorption on Pt-graphene. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**System** & **LUMO** & **HOMO** & \(E_{g}\) **(eV)** \\ \hline graphene & \(-3.798\) & \(-4.229\) & \(0.489\) \\ Pt-graphene/SO\({}_{2}\)\& SOF\({}_{2}\) & \(-4.279\) & \(-4.843\) & \(0.564\) \\ Pt-graphene/SO\({}_{2}\)\& SO\({}_{2}\)F\({}_{2}\) & \(-4.645\) & \(-5.349\) & \(0.704\) \\ Pt-graphene/SOF\({}_{2}\)\&SO\({}_{2}\)F\({}_{2}\) & \(-4.607\) & \(-5.314\) & \(0.706\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: HOMO, LUMO, \(E_{g}\) before and after adsorption of double foreign SO\({}_{2}\), SOF\({}_{2}\), SO\({}_{2}\)F\({}_{2}\) by Pt-graphene. **Supplementary Materials**: The following are available online at [[http://www.mdpi.com/2076-3417/8/10/2010/s1](http://www.mdpi.com/2076-3417/8/10/2010/s1)]([http://www.mdpi.com/2076-3417/8/10/2010/s1](http://www.mdpi.com/2076-3417/8/10/2010/s1)), Figure S1: Adsorption structure and adsorption energy comparison of single molecule adsorbed on Pt-graphene. Figure S2: Adsorption structure and adsorption energy comparison of double SO\({}_{2}\), SOF\({}_{2}\) and SO\({}_{2}\)F\({}_{2}\) adsorbed on Pt-graphene. Figure S3: Adsorption structure and adsorption energy comparison of double double foreign molecules adsorbed on Pt-graphene. Table S1: Cartesian coordinates of SO\({}_{2}\), SOF\({}_{2}\) and SO\({}_{2}\)F\({}_{2}\). Table S2: Cartesian coordinates of graphene and Pt-graphene. Table S3: Cartesian coordinates of single molecule adsorbed on Pt-graphene. Table S4: Cartesian coordinates of double molecule (SO\({}_{2}\), SOF\({}_{2}\), 2 SO\({}_{2}\)F\({}_{2}\)) adsorbed on Pt-graphene. Table S5: Cartesian coordinates of double molecule (SO\({}_{2}\)& SOF\({}_{2}\), SO\({}_{2}\)& SO\({}_{2}\)F\({}_{2}\), SOF\({}_{2}\)& SO\({}_{2}\)F\({}_{2}\)) adsorbed on Pt-graphene. **Author Contributions**: [PERSON] and [PERSON] proposed the project and revised the manuscript. [PERSON] and [PERSON] contributed to the theoretical simulation and analyzed the simulation results. All authors read and approved the final manuscript. **Funding**: The authors are very grateful to the support by the Natural Science Foundation of the Guangxi Province (No. 2016 GXNSFAA380327).