Biocompatible Nanodiamonds Derived from Coal Washery Rejects: Antioxidant, Antiviral, and Phytotoxic Applications

Coal washery rejects (CWRs) are a major byproduct produced in coal washery industries. We have chemically derived biocompatible nanodiamonds (NDs) from CWRs toward a wide range of biological applications. The average particle sizes of the derived blue-emitting NDs are found to be in the range of 2-3.5 nm. High-resolution transmission electron microscopy of the derived NDs depicts the crystalline structure with a d-spacing of 0.218 nm, which is attributed to the 100 lattice plane of a cubic diamond. The Fourier infrared spectroscopy, zeta potential, and X-ray photoelectron spectroscopy (XPS) data revealed that the NDs are substantially functionalized with oxygen-containing functional groups. Interestingly, the CWR-derived NDs exhibit strong antiviral properties (high inhibition of 99.3% with an IC₅₀ value of 7.664 μg/mL) and moderate antioxidant activity that widen the possibility of biomedical applications. In addition, toxicological effects of NDs on the wheatgrass seed germination and seedling growth showed minimal inhibition (<9%) at the highest tested concentration of 300.0 μg/mL. The study also provides intriguing prospects of CWRs for the creation of novel antiviral therapies.