Chemical Fabrication of Efficient Blue‐luminescent Carbon Quantum Dots from Coal Washery Rejects (Waste) for Detection of Hg²⁺ and Cr⁶⁺ Ions in Water

Abstract

An economical facile method was established for the preparation of luminescent carbon quantum dots (CQDs) by utilizing the waste coal washery rejects as precursor materials. The derived CQDs were extensively characterized for their physiochemical properties and they (Mcqds and Dcqds) show an efficient maximum quantum yield of 11 % with an average particle size of 2.5-3.0 nm. The derived CQDs exhibited better physical and chemical properties at maximum excitation and emission wavelengths of 360 nm and 450 nm, respectively, with blue-light emission. The as-synthesized CQDs (Mcqds) were applied as a fluorescent sensing probe for sensitive detection of Hg 2 + and Cr 6 + ions in water samples, showing reasonable limit of detection and quantification with recovery percentage of 96-100 %. The study has shown potential for using such cheap waste-material derived CQDs as for further development of sensing devices in future.[a] A. Boruah

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

“…Coal washery rejects (CWRs) are the solid wastes such as coal fines, rock, and soil produced worldwide as leftover materials from washing the run-off-mine (ROM) coal in coal washery industries. These coal rejects are not properly utilized and usually dumped near the sites of coal washery industries which may pollute the nearby areas . The novelty of the present research work is the conversion of coal washery rejects (CWRs) into high-valued nanodiamonds (NDs) using an environmentally friendly and economically viable ultrasonic-assisted wet chemical oxidation method, holding great promise for the profitable utilization of these coal industry-generated waste materials along with possible control of the associated pollution.…”

Solid-State Phosphors from Coal-Derived Carbon Quantum Dots

“…The recent development of top-down methods for the synthesis of CQDs from the least expensive and abundant coal resources opens up new possibilities for using these nanomaterials in various technologically advanced applications. However, only limited research works have been conducted worldwide on developing carbonaceous nanomaterials from highly abundant coal sources. − Most notably, our group has developed a novel wet-chemical ultrasonic-assisted, environmentally friendly method for synthesizing bio-compatible heteroatom-doped CQDs and nanodiamonds from highly abundant low-quality Indian coals, coal washery rejects (CWRs), and biomass wastes. ,− The heteroatom-doped CQDs obtained from coal and biomass sources possess promising fluorescent properties with good quantum efficiency. The fluorescence emission of synthesized CQDs selectively gets quenched in the presence of metal ions, which was exploited to detect silver, mercury, and chromium ions in water. , Moreover, the metal ion-induced fluorescence quenching of CQDs could be reversible, enabling us to detect fluoride ions in water .…”

“…The fluorescence emission of synthesized CQDs selectively gets quenched in the presence of metal ions, which was exploited to detect silver, mercury, and chromium ions in water. 29 , 34 Moreover, the metal ion-induced fluorescence quenching of CQDs could be reversible, enabling us to detect fluoride ions in water. 35 Coal-derived CQDs were also used to synthesize silver/CQD nanocomposites that exhibit good antibacterial properties against Gram-positive and Gram-negative bacterial strains.…”