## 3 Results and Discussion  
The SEM and AFM images of individual RuO\({}_{2}\) NSs dispersed on a glass substrate are illustrated in Figure 1a,b, respectively. Figure 1a depicts the smooth surface of the NSs, and Figure 1b clearly reveals exfoliated RuO\({}_{2}\) NSs, which have a smooth and flat surface with an almost uniform thickness. The thicknesses of the monolayer RuO\({}_{2}\) NSs were measured to be \(\sim\)1.2 nm, which is the same as their theoretical thickness [11]. Notably, in the SEM and AFM images depicted in Figure 1, the exfoliated RuO\({}_{2}\) NSs exhibit varying lateral sizes, which aids in the fabrication of conducting films from the RuO\({}_{2}\) NSs by enhancing the percolation between the NSs within a coating. Figure 2a depicts an SEM image of the conducting transparent films after the coating of a single layer of the RuO\({}_{2}\) NSs. The packing density was controlled by fine-tuning the surface pressure of the air-water interface during the LB coating process to ensure that it was approximately 90%. LB coating was repeatedly performed 5-10 times to form the electrical conducting path across the multi-layered NS films. Furthermore, HR-TEM was employed for investigating the lateral deposition structure of the conducting transparent RuO\({}_{2}\) NS films. Figure 2b illustrates the cross-sectional HR-TEM image of the 10-time-deposited RuO\({}_{2}\) NS films on a glass substrate, which exhibits a close-packed, uniform, and flat structure. These features are known to be advantageous for the fabrication of electrical-conducting pathways through these films [13]. Figure 1: Characterization of RuO\({}_{2}\) nanosheets. (**a**) FE-SEM image of a RuO\({}_{2}\) nanosheet (NS) with a large lateral diameter. (**b**) AFM image of a chemically exfoliated RuO\({}_{2}\) NS. To investigate the influence of UVO treatment time on the electrical as well as optical properties of the RuO\({}_{2}\) NS films, UVO exposure times were varied to a maximum of 60 min for the five-layered RuO\({}_{2}\) NS films. The observations depicted in Figure 3a indicate that \(R_{\rm s}\) decreased from 2548 to 2243 \(\Omega\)/sq, by 14%, as time progressed. In particular, the decline in the value of \(R_{\rm s}\) was rather significant in the first 30 min, demonstrating a decrease of \(\sim\)10% to 2286 \(\Omega\)/sq. The UVO is able to decompose the tetrabutylammonium cations (TBA\({}^{+}\)), which cover the surface of RuO\({}_{2}\) NS [16, 17]. [PERSON] et al. reported that ultraviolet and thermal treatment was effective for enhancing the electrical properties of nanosheets films by removing the TBA\({}^{+}\)[16]. However, beyond 30 min, the \(R_{\rm s}\) decrease became much smaller, as observed in the 45 min and 60 min UVO exposure samples. Therefore, we found that the effect of UVO treatment was marginal when its duration was longer than 30 min. The variation in the optical transmittance with the treatment time is depicted in Figure 3b. The enhancement of electrical conductivities was maintained for more than 24 h. This chemical stableness of RuO\({}_{2}\) NS films caused by the imperfect removal of TBAOH after UVO irradiation was reported by [PERSON] et al. [16]. It seems that the residual TBAOH after UVO irradiation serves as a stabilizer. The optical transmittance increased from 89.2 to 91.5% by 2.6% as time progressed. Moreover, we observed that after 30 min of treatment, the rate of increase in the optical transmittance was apparently saturated. From these observations, it can be concluded that a moderate amount of UVO improves the electrical and optical properties of the RuO\({}_{2}\) NS films simultaneously by eliminating the residual organic contaminations on the surfaces of the RuO\({}_{2}\) NS layers. Specifically, 30 min of UVO treatment reduced the \(R_{\rm s}\) by 10% and increased the optical transmittance by 2.4%.