Ex situ synthesis and characterization of chitosan-ZnO nanocomposites using ZnO nanoparticles prepared by the precipitation method

The varied properties of biopolymer nanocomposites, including their reactive functional groups and nanoscale dimensions, which are not found in bulk materials, have garnered considerable interest for a range of applications. However, their properties and effectiveness are significantly influenced by the synthesis processes employed, as well as the structure and distribution of their components. In this study, the precipitation method was used to prepare zinc oxide nanoparticles (ZnO NPs) at various reaction temperatures. Subsequently, chitosan-zinc oxide nanocomposites (CZ NCs) were synthesized via an ex-situ method, incorporating ZnO NPs with different concentrations of chitosan (CS). Morphological analysis indicated that the size and shape of ZnO NPs were affected by the reaction temperature, with particles synthesized at 40 °C being smaller and exhibiting less aggregation. FTIR analysis of CZ NCs revealed a broad peak at 3312 cm−1, characteristic of the amine and hydroxyl groups present in CS. This peak’s shift to a lower wavenumber suggests an interaction between these functional groups and ZnO NPs. Additionally, an absorbance peak at 614 cm−1 confirmed the presence of ZnO NPs within the composite. Crystalline analysis showed a reduction in the peak intensity of CZ NCs, attributed to the semi-crystalline nature of CS. Morphological analysis further indicated that the agglomeration of CZ NCs increased with higher concentrations of CS. The distribution of CS molecules within the composite was assessed by evaluating the physical interactions between the CZ NCs and methylene blue (MB) molecules. The sample with 10% chitosan (CS10) demonstrated a stronger interaction with MB molecules, suggesting a more even distribution of CS throughout the composite. Combining the precipitation method with ex-situ synthesis offers high productivity for nanocomposite production. This approach enables the synthesis of nanocomposites with nanoscale dimensions, which improves the dispersion of active sites and enhances their effectiveness and interaction with other materials. Consequently, these nanocomposites can serve as reinforcements to enhance the properties of various materials.