A Comparative Study of PEGylated Cobalt Oxide Nanoparticles (Co₃O₄-NPs) and Cobalt Sulfide Nanoparticles (Co₉S₈-NPs) for Biological and Photocatalytic Applications

Cobalt oxide nanoparticles (Co₃O₄-NPs) and cobalt sulfide nanoparticles (Co₉S₈-NPs) have shown extensive potential in electrochemical sensing, catalysis, specific drug targeting, and resonance imaging. However, Co₉S₈-NPs have been rarely explored for biomedical applications as compared to their oxide counterparts. Thus, in the current study, biocompatible PEGylated Co₉S₈-NPs and Co₃O₄-NPs are explored and compared for biological and photocatalytic properties. PEGylation of both the NPs is achieved using a simple chemical co-precipitation method followed by characterization using UV visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and pH-responsive dispersion study. After thorough characterization, the NPs are evaluated and compared for various biological applications including antibacterial, antifungal, antileishmanial, antioxidant, and biocompatibility as well as photo-catalytic dye degradation studies. Both the NPs have shown excellent biological applications; however, Co₉S₈-NPs exhibit comparatively better antibacterial, antifungal, and antioxidant properties except antileishmanial potential where Co₃O₄-NPs show slight superiority. Furthermore, Co₃O₄-NPs indicate a higher degradation potential of methylene blue (MB) up to 46.93%. In comparison, Co₉S₈-NPs have a degradation ability of up to 42%, at 20 mg/ml within 3 h, which indicates considerable remediation potential of the NPs. Interestingly, both the NPs exhibit non-hemolytic behavior, thus demonstrating a compatible and bio-safe nature of both the NPs.