Enhancement of the Structure, Thermal, Linear/Nonlinear Optical Properties, and Antibacterial Activity of Poly (vinyl alcohol)/Chitosan/ZnO Nanocomposites for Eco-Friendly Applications

The preparation of poly (vinyl alcohol)/chitosan/ZnO (PVA/Cs/ZnO) nanocomposite films as bioactive nanocomposites was implemented through an environmentally friendly approach that included mixing, solution pouring, and solvent evaporation. The nanocomposite films were characterized using various techniques such as X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and UV-Vis spectroscopy. The XRD study revealed the encapsulation of nanoparticles by the PVA/Cs blend matrix. The DSC results showed that the addition of ZnO NPs increased glass transition and melting temperature values of the PVA/Cs blend. ATR-FTIR spectra detected an irregular shift (either red or blue) in some of the characteristic bands of the PVA/Cs nanocomposite, indicating the existence of intra/intermolecular hydrogen bonding creating an interaction between the OH groups of PVA/Cs and ZnO nanoparticles. A thermogravimetric (TGA) analysis demonstrated that the nanocomposites achieved better thermal resistance than a pure PVA/Cs blend and its thermal stability was enhanced with increasing concentration of ZnO nanoparticles. UV analysis showed that with an increase in the content of ZnO NPs, the optical bandgap of PVA/Cs was decreased from 4.43 eV to 3.55 eV and linear and nonlinear parameters were enhanced. Our optical results suggest the use of PVA/Cs/ZnO nanocomposite films for various optoelectronics applications. PVA/Cs/ZnO nanocomposites exhibited significant antibacterial activity against Gram-positive and Gram-negative bacteria. It was found that nanocomposite samples were more effective against Gram-positive compared to Gram-negative bacteria.

Green synthesis of (CS/OLE) AgNPs and evaluation of their physico-chemical characteristic

The present article involves the bio-synthesis of (Chitosan/olive leaf extract) silver nanoparticles (CS/OLE) AgNPs using a simple green electrochemical procedure followed by UV-irradiation time. The properties and structure of the resulting (CS/OLE) AgNPs were characterized by employing several analytical techniques including, Infrared spectrum (FT-IR), UV–VIS spectroscopy, X-ray analysis (XRD), energy-dispersive X-ray (EDX) and degredation. Besides, the studying of the thermal characteristics of the (CS/OLE) AgNPs electrets were also investigated. Formation of Ag nanoparticles was observed upon varying the solution color from faint yellow into yellowish brown and was achieved by the appearance of absorption peak at about ~ 410 nm of the resulting AgNPs corresponding to the surface plasmon resonance (SPR). The sharp peaks appear at 32.16°, 46.19°, 54.75°, 57.59°, and 76.7°, indicating the presence of AgNPs as shown from XRD. With comparing the anti-bacterial efficiency of (CS/OLE) AgNPs and (CS/OLE) we found that the AgNPs display a relatively high anti-bacterial activity than in plant extract and chitosan alone. The electrical properties of (CS/OLE) AgNPs films were studied by global thermally stimulated depolarization current (TSDC) spectra for explaining the relaxation phenomena of the samples. In addition, the molecular parameters (The activation energy Ea and pre-exponential time τo), have been evaluated by the Arrhenius equation. The Ea was found in ~ (0.39–0.62 eV) for (CS/OLE).