Reconfigurable cellulose-supported ZnO microflowers for environmental remediation: from emerging pollutants photodegradation to smart antibacterial interfaces

The misuse/overuse of antibiotics in the last 20 years has caused a dramatic evolution of antimicrobial resistance1. To this aim, new strategies to overcome this challenge can by the employ of new rationally designed materials. Among the possible candidates, ZnO-based materials are increasingly studied, given their optimal photocatalytic properties and excellent biocompatibility as reported by the Food and Drug Administration (21CFR182.8991)2. The study focuses on the synthesis of ZnO microflowers (MFs) and their incorporation into cellulose foils or powder for the light-triggerable release of ROS (reactive oxygen species). It is demonstrated a synthetic approach of highly photocatalytic active ZnO MFs based on a central composite experimental design in which the synthesis parameters - such as zinc ions and KCl concentrations and synthesis temperature - are all investigated to obtain the optimal photodegradation response of dye pollutants (e.g. methylene blue). The ZnO MFs synthesis is further optimized to induce biologically-inspired dissipative motion for capturing pollutants3, by ZnO-based microrobots in the form of Ag/ZnO heterojunctions, resulting in promising features. The morphology and the physico-chemical properties of the materials are analysed by instrumental techniques (DRS, SEM, XPS, XRD, UV-Vis and ζ-potential). It is found an optimal ZnO loading to enhance the photocatalytic properties as a result of surface-to-bulk dispersion4. In parallel, preliminary antibacterial activity of the ZnO-based systems are studied on gram-positive and gram-negative strains.