Synergistic photocatalytic activity of zinc oxide and low molecular weight chitosan nanocomposite

This study explores the extraction of chitosan (CH) from Sepia brevimana cuttlebone. The CH is then exposed to gamma irradiation to convert it into low molecular weight chitosan (GIR-LMW-CH). The degree of deacetylation (DDA), which is 94.2%, is conclusively confirmed by nuclear magnetic resonance spectroscopy (NMR). By using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS), the molecular weight (MW) of the isolated CH is determined to be 697.4 Da. Then, zinc oxide (ZnO) nanocomposites are created using the GIR-LMW-CH. X-ray diffraction (XRD) revealed that the ZnO generated using the sol–gel technique had a particle size of about 13 nm. The synthesized ZnO-CH nanocomposites were characterized by thermogravimetric analysis (TGA), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), and dynamic light scattering (DLS) analysis, which revealed a hydrodynamic size of 16 nm. This nanocomposite’s photocatalytic activity is assessed using both anionic methyl orange (MO) and cationic methylene blue (MB) dyes. ZnO-GIR-LMW-CH, which was synthesized, has an exceptional decomposition efficiency, accomplishing 98.93% degradation of MB in just 1.5 h and an astounding 99.27% degradation of MO in 4.5 h. The effect of photocatalyst amount and its recyclability efficiency was also evaluated.