Enhanced Crystallinity Behavior of Egg White Mediated h-MoO₃ Using Acid Precipitation Method for Improved Anti-Bacterial Properties against Multi Drug Resistant Bacteria

Hexagonal molybdenum trioxide (h-MoO₃) was synthesized using egg white with MoO₃ precursor, which was further treated with nitric acid (HNO₃) by solution-based chemical precipitation technique for comparison without treatment. The XRD analysis confirms the formation of metastable phase with hexagonal crystal system for h-MoO₃ with and without HNO₃ treatment. Subsequently, the result indicate that the HNO₃ treated h-MoO₃ shows enhanced crystalline behavior compared to untreated h-MoO₃. Raman and FTIR analysis confirmed the formation of h-MoO₃ where the variation in intensity of the peaks were observed when comparing h-MoO₃ with and without HNO₃ treatment as well as due to the changes in the crystalline structure of the samples. The band gaps obtained from Tauc plot for the synthesized h-MoO₃ with and without HNO₃ treatment were 3.17 eV and 3.26 eV, respectively. Observations by HRSEM and HRTEM allowed confirming the formation of nanorod and nanoplate like structures for h-MoO₃ treated with and without HNO₃, respectively. In addition, the increased crystallinity of the HNO₃ treated h-MoO₃ was displayed higher anti-bacterial activity than untreated h-MoO₃ with zones of inhibition values of 14 ± 1 and 12 ± 1 mm against multi drug resistant (MDR) E. coli and K. pneumoniae, respectively. Subsequently, the quantitative analysis of HNO₃ treated h-MoO₃ demonstrated 94% and 96% inhibition against E. coli and K. pneumoniae, respectively, at 250 µg/mL concentration. Oxidative stress mediated membrane damages and surface morphology alterations were observed after exposure of HNO₃-treated h-MoO₃ (improved crystallinity) against E. coli and K. pneumoniae as suggested by confocal laser scanning electron microscopy and scanning electron microscopy. Furthermore, very minimal cytotoxicity to human alveolar epithelial cell line (A549) for HNO₃ treated h-MoO₃ was observed, suggesting that this material is benign. The present study indicates that the enhanced crystallinity of HNO₃ treated h-MoO₃ synthesized in the presence of egg white can be considered as a promising alternative drug target material to fight against MDR bacteria.