Nanodiamonds Produced from Low-Grade Indian Coals

Coal is considered to be an abundantly available cheap feedstock for the fabrication of carbon nanomaterials. In this Letter, a report on the formation of nanodiamond from low-grade coals during low-power ultrasonic-assisted stimulation in hydrogen peroxide (H2O2) followed by dialysis in 1 kDa is given. High resolution-transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), Raman spectroscopy, ultraviolet visible spectroscopy (UV-vis), fluorescence (FL), and Fourier transform infrared (FT-IR) spectroscopy analyses revealed the formation of carbon nanocrystals of monocrystalline and polycrystalline form with multiple plans. The nominal size of the carbon nanocrystals are found to be in the range of 4-15 nm. The planar spacing of the crystal lattice fingers is in the range of 2.0-2.3 angstrom and are in good agreement with the lattice planes of various diamond phases including cubic diamond and lonsdaleite. The present work significantly contributes an additional synthetic methodology of nanodiamond production by using the cheap low-grade coal feedstock. The nanodiamond formed shows bright blue fluorescence under UV-light with excitation dependent and holding promising application in bioimaging engineering, photovoltaics, and optoelectronics.