A. Azenkeng
University of North Dakota Energy & Environmental Research Center,
United States
Keywords: coal, impurities, ash, graphene, graphene quantum dots
Summary:
The impact of coal-borne impurities on coal-derived graphene quantum dots (GQDs) has been investigated on four U.S. coal ranks: lignite, subbituminous coal, bituminous coal, and anthracite. Preliminary characterization of the GQDs produced from raw and clean coals has been done using UV-vis and UV fluorescence spectroscopy techniques. Higher fluorescence emission intensities were observed from GQDs obtained from clean coal samples compared to those obtained from raw coal samples. The emission maxima show an increasing redshift from lowest to highest coal rank, i.e., lignite, subbituminous, bituminous, and anthracite. It was also observed that excitation of anthracite-derived GQDs in the UV region produces little to no fluorescence signal, but a maximum emission signal was observed when excitation was performed in the visible region. These results are relevant in tailoring specific optical applications of GQDs derived from different coal ranks.