Hydrogen-bonding induced assembly of polymer-grafted nanoparticles towards photothermal antibacterial activities

The multiple hydrogen-bond has been introduced as a reversible driving force for directing the assembly of polymer-grafted nanoparticles (PGNPs). The complementary hydrogen-bonds among the polymer ligands lead to the spontaneous aggregation of PGNPs. However, it may also induce the uncontrollable aggregation of PGNPs into assemblies with non-uniform size, even irregular precipitates, due to the immoderate agglomeration associated with the strong interactions of multiple hydrogen-bonds. This severely limits the stable dispersion of PGNP aggregates in a solvent and their applications. In this work, the gold nanoparticles (AuNPs) grafted with thymine-terminated polystyrene (AuNP@PS-Thy) and diaminopyridine-terminated polystyrene (AuNP@PS-Dap) were synthesized, respectively. Their thermal-responsive assembly behavior in an organic solvent was systematically studied. By optimizing the assembly conditions, i.e., the concentration of PGNPs and the incubation time, the assemblies of AuNP@PS-Thy/AuNP@PS-Dap with controllable size were obtained. Interestingly, the assemblies deposited on a solid substrate showed excellent photothermal antimicrobial activities under irradiation of 808 nm and 655 nm lasers. The killing percentage of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) could reach 99 % after irradiating for 10 min. This work establishes an approach for controlling the hydrogen-bonding-induced assembly behavior of PGNPs, which may be extended to construct functional metamaterials with controllable structures.