Microwave-assisted hydrothermal synthesis of cellulose/ZnO composites and its thermal transformation to ZnO/carbon composites

Development of a simple and rapid method for the preparation of cellulose/ZnO composites is of great importance for broadening and improving their potential applications. In this work, the cellulose/ZnO composites were synthesized via the microwave-assisted hydrothermal method using cellulose, zinc nitrate hexahydrate, and ammonia in an aqueous solution. The influence of the cellulose on ZnO crystals was investigated in detail. Cell cytotoxicity of the as-obtained cellulose/ZnO composites was explored. All the cell viability values of the cellulose/ZnO composites were above 95%, indicating that cellulose/ZnO composites had essentially no cytotoxicity. ZnO/carbon (ZnO/C) composites were obtained by calcination at 600 degrees C in the N-2 atmosphere using cellulose/ZnO composites as precursors. The flower-shaped ZnO crystals could still maintain their morphologies via the N-2 atmosphere calcination. These ZnO/C composites exhibited good photocatalytic performances under both UV and visible light irradiation. Under the UV light irradiation, the degradation efficiency values of methylene blue and rhodamine B dyes were up to 99% and 97%, respectively. The kinetic linear model curves of the photocatalytic degradation of the two dyes could be assigned to the pseudo-first-order kinetics model. This work provided a potential strategy for the synthesis of metallic oxide/cellulose composites, which have broadened the applications of the composites.