Green Synthesis, Structural Characterization and Photocatalytic Activities of Chitosan-ZnO Nano-composite

Chitosan was isolated from chitin, a direct derivative of snail shell, and further used to form a heterostructure with ZnO nanoparticles (ZnO NPs). This study was carried out to utilize green nanochemistry in the purification of waste water. The obtained ZnO-chitosan nanocomposite was made by precipitation method and characterized by Fourier Transform Infrared (FTIR), powder X-ray diffraction (pXRD), Energy dispersive X-ray (EDX), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses. The FTIR spectra among other peaks revealed bands around 1735-1740 cm(-1) in all the spectra due to C=O stretching band. The XRD patterns showed the crystalline nature of ZnO and the ZnO-chitosan nanocomposites with low intensities in the peaks of the nanocomposites, an indication of reduced crystallinity. The SEM micrographs showed thin strands of the chitin and chitosan whereas the ZnO NPs appeared as clustered spheroids with the ZnO-chitosan nanocomposites revealing the anchoring of the ZnO spheroids on the smooth strands of the chitosan. The EDX spectra showed various elemental compositions with 54.82% Zn in the ZnO NPs and 17.27% Zn in the ZnO-chitosan nanocomposites. TEM studies showed spherical images of the ZnO NPs (3.69 nm) and the quasi-spherical nature of the ZnO-chitosan nanocomposites (8.91 nm). The photodegradation of methylene blue dye by ZnONPs recorded gradual decomposition of the dye while in the composite, a tremendous change was observed within the first 15 min of the reaction.