Cellulose/ZnO nanoparticles (CNC/ZnO NPs): synthesis, characterization, and evaluation of their antibacterial and antifungal activities

This study aims to repurpose plant waste, specifically pea husks, to synthesize cellulose/zinc oxide nanoparticles (CNC/ZnO NPs) using two environmentally friendly and low-cost techniques. Initially, cellulose nanocrystals (CNCs) were extracted from the cellulose-rich biomass of pea husks through chemical treatments. Subsequently, a hybrid material of CNCs and ZnO NPs was fabricated using two techniques: T1, involving the dissolution of cellulose (Cs) in a basic solution, and T2, utilizing Cs crystals directly. The yield of the obtained Cs and CNCs was quantified, demonstrating a high biomass yield of 93.04 ± 1.39% for Cs and 28.81 ± 2.18% for CNCs. Various analysis techniques, including Fourier-Transform Infrared spectroscopy (FT-IR), X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and Ultraviolet visible spectroscopy (UV–Vis), were employed to study the material's different properties. Furthermore, CNC/ZnO NPs were tested against human pathogenic bacteria and a fungus. Results indicated the crystalline nature of the CNC/ZnO NPs, with an average size of 20 nm. Morphological analysis showed a notable contrast in ZnO nanoparticle distribution on CNC surfaces. In the first method, ZnO NPs formed a complete and evenly distributed coating, resulting in a smooth structure. Conversely, the second method led to ZnO NPs appearing as scattered dots on the CNCs, resulting in the lowest ZnO NP content. The study demonstrated a significant increase in antimicrobial properties after coating Cs nanoparticles with ZnO NPs, with the hybrid material exhibiting higher antimicrobial activity than pure CNCs. These findings suggest the potential of CNC/ZnO NPs for antimicrobial pharmaceuticals and as a natural food preservative to control the growth of microorganisms.