Microplasma-assisted synthesis of chromium oxide nanoparticles and their biological activities

Abstract Chromium oxide nanoparticles are of significant interest and are widely used in numerous applications due to their exclusive physicochemical properties, including wide bandgap, increased stability, high melting temperature, and antibacterial and antifungal properties. In this study, the atmospheric pressure microplasma technique is used to synthesize chromium oxide nanoparticles by changing the precursor concentration (10, 15, and 20 mM). The nanoparticles are characterized by numerous techniques, including XRD, SEM, FTIR, UV-visible spectroscopy, RAMAN Spectroscopy, and antibacterial and antifungal activities. It is observed in XRD analysis that different phases of chromium oxide nanoparticles, Cr2O3 and CrO2, can be attained when the precursor concentration is changed. As a result, their efficiency can be tuned to different applications. The UV visible results depict that the band gap is reduced by increasing the precursor concentration (Cr(NO3)3.9H2O). The FTIR analysis is used to determine the surface functional groups of synthesized nanomaterials. Our results demonstrate the potential of chromium oxide nanoparticles as effective antibacterial and antifungal agents. Specifically, we found that these nanoparticles exhibit a strong antibacterial impact on gram-negative bacteria and a reasonable effect on gram-positive bacteria under some synthesis conditions. Moreover, they depict significant anti-fungal activity against two pathogenic fungus species, Penicillin Digitatum, and Rhizopus stolonifers. These promising findings, particularly for nanoparticles prepared at the concentration of 10 mM precursor with the Cr2O3 phase, reveal that these nanoparticles can be used efficiently for antibacterial (particularly gram-negative bacteria) and antifungal activities.