Effect of zinc chloride and sodium hydroxide concentration on the optical property of chitosan–ZnO nanostructure prepared in chitin deacetylation

Chitosan–ZnO nanostructures are prepared by eco-friendly way of synthesis. With same amount of chitin, three different ratios of zinc chloride and sodium hydroxide concentrations are used for preparation. The hexagonal shape of chitosan–ZnO nanostructures with size range of 40–100 nm are confirmed by transmission electron microscopy (TEM). Surface morphology is characterized by scanning electron microscopy. Maximum Zn/O atomic ratio of 77:23 is noticed by energy dispersive X-ray (EDAX) analysis. Presence of chitosan and ZnO structure are confirmed with FTIR spectra. Absorbance at 364 nm in the UV–vis spectra indicates the presence of ZnO. X-ray diffraction pattern indicates the size of crystallites are in 16–53 nm range. Optical studies revealed that chitosan–ZnO nanostructure with band gap of 3.4 eV have been prepared by slow addition of 45% sodium hydroxide into 15% zinc chloride and chitin solution.

► Micro addition of sodium hydroxide induced the nano particles crystallization. ► Nano crystals with maximum Zn/O ratio of 77:23 was prepared. ► Crystalline size with 16–53 nm was estimated by XRD. ► In this study, nanocrystalline powders with band gap of 3.32 eV was prepared.