Daylight-driven rechargeable antibacterial and antiviral nanofibrous membranes for bioprotective applications

Si, Yang; Zhang, Zheng; Wu, Wanrong; Fu, Qiuxia; Huang, Kang; Nitin, Nitin; Ding, Bin; Sun, Gang

The properties of photoactive nanofibrous-structured RNMs can be further demonstrated by their promising rechargeable biocidal functions. We have indicated that the photoactive cycle consists of the excitation, hydrogen abstraction, and quenching by oxygen. However, if the generated RNMH• was not fully quenched by oxygen or other organic burdens (for example, microbes), then other competing reactions related to activity storage could occur. To demonstrate this, we irradiated the relevant RNMs under daylight with increasing exposure time to 60 min and studied the photo-induced reaction and structure rearrangement with UV-vis spectroscopy and TD-DFT calculations, as shown in Fig. 3 (A to D) . The BA-RNM shows an obvious absorption peak shift from 262 to 252 nm, characteristic of the formation of reduced moieties in diphenylmethanol (DPM) form ( fig. S11 ) (41) . Meanwhile, besides the DPM formation, a distinct absorption increase was observed at 420 nm for BD-RNM, indicating the formation of a metastable transient photoproduct that was previously referred as the light-absorbing transient (LAT) moieties (fig. S12) (42, 43) . Similarly, the BDCA-RNM exhibited an even more distinct LAT formation without DPM transition. No visible change was recorded for CA-RNMs, which was due to the poor hydrogen abstraction ability. The formed DPM photoproduct was quite stable and was not able to go back to the original benzophenone statues ( fig. S13) . Meanwhile, the LAT moieties were proven to be oxygen-sensitive and can be readily quenched and reversed to benzophenone by reducing agents in the presence of oxygen (fig. S14), regenerating the photoactivity (42, 44) . A detailed mechanistic proposal for the rechargeable reactions of RNMs in the presence of oxygen is shown in Fig. 3E .