Host–Guest Encapsulation of GQD and RB for Photodynamic and Quaternary Ammonium Dual-Action Antibacterial Coating

An amphiphilic, hyperbranched, and core–shell structured quaternized ammonium polymer, hexadecanol chloroacetate modified methylated hyperbranched polyethylenimine (MeHPEI-CCA), was prepared. Then, a facile host–guest encapsulation process through phase transfer was used to create a complex composed of MeHPEI-CCA as host and rose Bengal (RB) and graphene quantum dots (GQD) as guests, with combined photodynamic antimicrobial chemotherapy (PACT) function and quaternary ammonium salt antibacterial function. This is an example of GQD (about 3–5 nm) being encapsulated into a dendritic host. Subsequent cross-linking with epoxy-terminated polysilsesquioxane (PSi) by residual tertiary amino group-initiated ring-opening reaction gave the dual-effect antibacterial organic–inorganic coating. All the coating samples were transparent, flexible, and impact-resistant. Samples from QHP-0 to QHP-70 demonstrate excellent impact resistance. In particular, sample QHP-0 achieves a drop hammer height of 50 cm. Furthermore, samples ranging from QHP-20 to QHP-70 show a consistent bending deflection of merely 1 mm, indicating outstanding toughness. The nonguest-containing samples, QHP-10 to QHP-70, exhibited excellent antibacterial performance, while the samples, QHP-50-RB and QHP-50-GQD, containing RB and GQD, respectively, performed much better. Because there was a maximum loading capacity of GQD or RB, QHP-50-RB was further reinforced with GQD to give QHP-50-GQD&RB, which possesses the best antibacterial performance.