Silver Sulfide Nanocrystals as a Biocompatible and Full-Spectrum Photocatalyst for Efficient Light-Driven Polymerization under Aqueous and Ambient Conditions

Abstract

Owing to current global environmental concerns, polymers must be prepared under eco-friendly reaction conditions based on sustainable chemistry. In this context, highly efficient photoinduced energy/electron transfer reversible addition- fragmentation chain-transfer (PET-RAFT) polymerization under ambient/aqueous conditions without additives and/or with the aid of sunlight is the optimal approach for producing polymers with well-defined structures. This can be accomplished with a photocatalyst (PC) that utilizes the full spectrum of sunlight for maximum efficiency and has excellent water solubility or dispersibility, oxygen tolerance, and biocompatibility. However, a PC with all of these features has not yet been developed. In this study, we confirmed that this could be achieved using Ag2S nanocrystals (NCs) as photocatalysts. The sufficient reducing power of Ag2S NCs enabled the successful aqueous PET-RAFT polymerization of numerous acrylic monomers under ambient natural sunlight illumination without any additives. Under illumination, the small band gap of Ag2S NCs suppressed the generation of singlet oxygen, resulting in low cytotoxicity toward three different cell lines. Finally, we demonstrated that PET-RAFT polymerization with Ag2S NCs can be accomplished in biologically relevant media under natural sunlight illumination, indicating adequate biocompatibility and efficacy of the system.