Characterization and comparative assessment of bactericidal activity of carbon nanodots (CDs) and nanoparticles (CNPs) prepared from soot's of clarified butter and mustard oil, respectively

Carbon nanoparticles (CNPs) are carbon-based nanomaterial with dimensions in the range of 1–100 nm. In the present research, an ecofriendly, simple, and highly reproducible method was used to prepare the CNPs from the soot of clarified butter (carbon dots) and mustard oil (carbon nanospheres) in both pristine and oxidized forms. The obtained CNPs were subjected to various analyses such as UV-visible, Fourier transform infrared (FTIR), dynamic light scattering, high-resolution transmission electron microscopy, energy-dispersive X-ray, and X-ray diffraction (XRD). The analyses demonstrate that the size of butter-originated CNPs was found in the ranges of 10–90 nm (raw) and 5–20 nm (oxidized), whereas, in the case of mustard oil-originated CNPs, the size was observed in the ranges of 100–150 nm (raw) and 50–80 nm (oxidized). As per zeta potential results, the net surface charges on CNPs were observed as −9.05 and −14.6 mV in the case of raw and oxidized CNPs from butter, respectively, and −12.7 and −20.1 mV in the case of raw and oxidized CNPs from mustard oil, respectively. XRD results showed the typical graphitic crystalline nature of both kinds of CNPs irrespective of their initial raw material. FTIR results confirmed hydroxyl, carboxyl, carbonyl, and amide groups on CNPs that help in their capping and stabilization in the solvent media. Five bacterial strains, Staphylococcus aureus , Escherichia coli , Staphylococcus epidermidis , Klebsiella pneumoniae , and Moraxella catarrhalis , were used to assess the bactericidal potential of synthesized CNPs using agar-well and 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2 H - tetrazolium-5-carboxanilide-colorimetric methods. Butter-mediated oxidized CNPs were the most effective bactericidal agent against all the bacterial strains compared to mustard-originated CNPs. Furthermore, CNPs-mediated toxicity towards bacteria was both size and concentration dependent. Staphylococcus aureus and S. epidermidis were the most sensitive [minimum inhibitory concentration (MIC): 800 µg/ml] and resistant (MIC: 2.0 mg/ml) bacteria, respectively, towards CNPs-mediated toxicity. The synthesized CNPs were devoid of any metallic impurities and hence worthy of being used in various applications like imaging, labeling, sensor-technology, and environment monitoring and as an antibacterial agent.