Multifunctional polydopamine-carboxymethyl cellulose composite gels with Ag/AgCl/ZnO heterojunction to enhance sunlight-responsive photocatalytic activity.

Carboxymethyl cellulose (CMC) gel is an ideal substrate for supporting sunlight responsive photocatalysts, but the photocatalytic disinfection activity decreased due to the light-shielding effect of the gel. In order to enhance the formation of active oxygen species, polydopamine (PDA) was introduced in CMC gels to function as an intermediate to connect two semiconductors inside the gels via its quinhydrone charge-transfer complexation. CMC/PDA gel with a double-network was formed via chemical crosslinking and reversible hydrogen bonding between prepolymerized PDA and CMC, then Ag/AgCl, ZnO and Ag/AgCl/ZnO photocatalysts were formed in situ in CMC/PDA gel, respectively. Ag/AgCl/ZnO heterojunction loaded composite gel displayed a remarkable photocatalytic degradation activity, with a weight ratio of the degraded methyl orange divided by composite gels up to 0.00090 under sunlight irradiation for 30 min. Ag/AgCl/ZnO loaded gel presented the bactericidal rate of 99.9 % against E. coli and 99.8 % against S. aureus. The inhibition zone of Ag/AgCl/ZnO loaded composite gel with dopamine mass of 100 mg increased under 6 h of sunlight compared with 24 h in dark against both E. coli and S. aureus. The biocompatible Ag/AgCl/ZnO loaded composite gel with pH-responsive swelling property and sunlight-responsive antibacterial activity promised to broaden the application of CMC-based antibacterial gels.