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 photo-induced ROS generation cycle involves the hydrogen abstraction (RNMH•/ 3 RNM) by the triplet RNMs and a subsequent oxidation (RNM/RNMH•) by oxygen. To provide insight into the mechanism of the photo-induced reaction, we used DFT to calculate the energy of the relevant reaction moieties (see details in table S2). We also quantified the reaction feasibility using Gibbs free energy change (DG). As shown in Fig. 2H , both BA-RNM and BD-RNM exhibited obvious negative DG (RNM/RNMH•) and DG (RNMH•/ 3 RNM), revealing that the hydrogen abstraction and oxidation reactions were highly spontaneous. However, the poor daylight absorption ability of BA-RNM resulted in its weak photoactivity. In contrast, the CA-RNM showed significantly high DG (RNM/RNMH•) of 290 kJ mol −1 due to the inactive p-p triplet transition, which means that the hydrogen abstraction largely does not occur to form active radicals; thus, further ROS generation was also disabled despite the high excitation rate. Moreover, benefiting from the unique charge transfer feature of n-p transition, the BDCA-RNM exhibited high reactivity for both inter-and intramolecular photoreaction (see details in fig. S10 ), leading to the robust ROS generation efficiency (38, 40) . These results were further supported by the electrostatic potential (ESP)-mapped electron density of the T 1 and ground state of these RNMs. As shown in Fig. 2I , the T 1 states of BA-RNM, BD-RNM, and BDCA-RNM exhibited obvious electron deficiency character on the oxygen atom in the carbonyl group compared with the ground state, implying the high tendency for hydrogen abstraction (35, 41) . In contrast, a slight increase of ESP in carbonyl oxygen was observed for CA-RNM, resulting in the inactive T 1 states. From these results, we propose that the photoactivity of the RNMs is dictated both by the light-absorbing capability (that is, the transition to singlet state) and by the character of the T 1 triplet state (excitation configuration and structure of frontier orbital).