Synthesis, characterization and antimicrobial activity of ZnO-QDs @ bis MPA polyester-64-hydroxyl dendrimer nanostructures†

This study presents the successful synthesis and characterization of five novel zinc oxide quantum dots @ bis MPA polyester-64-hydroxyl dendrimer nanostructures with tuneable hydrophilicity. A unique feature of these ZnO quantum dots @ bis MPA polyester-64-hydroxyl dendrimer nanostructures is the functionalization of the bis MPA polyester-64-hydroxyl dendrimer with five different varying numbers of surface hydroxyl functional groups with zinc oxide quantum dots. The surface groups varied from 1, 5, 10, 20 and 40 zinc oxide quantum dots in ZnO-QDs @ bis MPA polyester-64-hydroxyl dendrimer nanostructures, respectively. The highly water-dispersible ZnO quantum dots @ bis MPA polyester-64-hydroxyl dendrimer nanostructures G4-R(ZnO-QDs)₁, G4-R(ZnO-QDs)₅, G4-R(ZnO-QDs)₁₀, G4-R(ZnO-QDs)₂₀ and G4-R(ZnO-QDs)₄₀ were chemically synthesized. The ZnO-QDs @ bis MPA polyester-64-hydroxyl dendrimer nanostructures were characterized using techniques such as UV-vis-NIR spectroscopy, atomic force microscopy, dynamic light scattering, attenuated total reflectance Fourier transform infrared spectroscopy, and Raman spectroscopy. Notably, these ZnO quantum dots @ bis MPA polyester-64-hydroxyl dendrimer nanostructures exhibited high water-dispersibility. A significant finding is that the unique feature of ZnO quantum dots @ bis MPA polyester-64-hydroxyl dendrimer nanostructures demonstrated synergistic antibacterial activity against Gram-positive bacteria. This research contributes to the growing field of nanotechnology by providing a method to tune the hydrophilicity, optical properties, molecular vibration, size and toxicity of nanostructures, which could have broad impacts on various scientific and technological domains.