Contribution of TEMPO-Oxidized Cellulose Gel in the Formation of Flower-Like Zinc Oxide Superstructures: Characterization of the TOCgel/ZnO Composite Films

In the present paper, we report on a simple and new approach for the synthesis of hierarchical flower-like zinc oxide superstructures ZnO (FL) in the presence of the TEMPO-oxidized cellulose gel (TOCgel) through a room temperature sol-gel process in aqueous medium. Resulting composite films based on TOCgel and ZnO were investigated by several techniques including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and mechanical tests. SEM images demonstrated the formation of well-shaped flower-like ZnO superstructures within the fibrous structure of the TOCgel with a uniform diameter (~5 μm). FTIR and XPS results clearly confirmed the formation of such ZnO structures. We suggested that the carboxylate groups of TOCgel fibers act as capping agents and promote the construction of such flower-like ZnO via a nucleation-growth process. A proposed mechanism based on the oriented attachment-driven growth was discussed in order to explain the formation of ZnO (FL). The photocatalytic activity of the TOCgel/ZnO composite in the degradation of methylene blue (MB) under UV irradiation was clearly confirmed. Finally, mechanical tests demonstrated that the former TOCgel/ZnO film maintained a good flexibility (bent up to ~120°) without losing its photocatalytic activity.