ABSTRACT
Following the global corona virus pandemic and environmental contamination caused by chemical plastic packaging, awareness of the need for environmentally friendly biofilms and antibacterial coatings is increasing. In this study, a biodegradable hybrid film, comprising of green-synthesized zinc oxide nanoparticles (ZnO NPs) with a chitosan (CS) matrix, was fabricated using a simple casting procedure. The ZnO NPs were synthesized using wild Mentha pulegium extract, and the synthesized NPs and films were characterized using different approaches. The structural, morphological, mechanical, antibacterial, and optical properties, as well as the hydrophilicity, of the prepared samples were investigated using various techniques. Gas chromatography-mass spectrometry measurements revealed the presence of phenolic compounds in the M. pulegium extract. In addition, a strong coordination connection between Zn2+ and the chitosan matrix was confirmed, which resulted in a good dispersion of ZnO in the chitosan film. The surface of the composite films was transparent, smooth, and uniform, and the flexible bio-based hybrid films exhibited significant antibacterial and antioxidant characteristics, strong visible emission in the 480 nm region, and UV-blocking properties. The ZnO/CS films displayed a potential to extend the shelf life of fruits by up to eight days when stored at 23°C, and also acted as an acceptable barrier against oxygen and water. The biodegradable ZnO/CS film is expected to keep fruit fresher than general chemical plastic films and be used for the packaging of active ingredients.
ABSTRACT
High-quality LiNbO3 colloidal nanocrystals were synthesized by the sol-gel technique. Morphological, structural, and optical spectroscopy methods were used to characterize LiNbO3 colloidal nanocrystals. To investigate the optical properties, UV-visible absorption spectroscopy was used, which showed that the absorption peak was around 250 nm. Zeta potential was used to determine the stability of colloidal LN nanoparticles. Selected area electron diffraction patterns and X-ray diffraction patterns indicated that the dried LiNbO3 sol formed in the rhombohedral crystal system. Field-emission scanning electron microscopy and transmission electron microscopy were used to study the morphological properties, which showed that the average diameter of colloidal nanocrystals is about 23 nm. Finally, two emission peaks were observed at 420 (violet) and 485 nm (blue) wavelengths in the photoluminescence (PL) spectrum. Also, using the PL measurements, the quantum yield for colloidal LiNbO3 was calculated to be 87% at an excitation wavelength of 250 nm. Experimental results have shown that highly stable LiNbO3 colloidal nanocrystals were synthesized that have enough potential for quantum photonics applications such as waveguides. The highly stable colloidal form of LiNbO3 nanocrystals has not been synthesized before, and the mentioned optical properties are reported for the first time.
