Coal as an abundant source of graphene quantum dots

Abstract

Coal is the most abundant and readily combustible energy resource being used worldwide. However, its structural characteristic creates a perception that coal is only useful for producing energy via burning. Here we report a facile approach to synthesize tunable graphene quantum dots from various types of coal, and establish that the unique coal structure has an advantage over pure sp 2 -carbon allotropes for producing quantum dots. The crystalline carbon within the coal structure is easier to oxidatively displace than when pure sp 2 -carbon structures are used, resulting in nanometre-sized graphene quantum dots with amorphous carbon addends on the edges. The synthesized graphene quantum dots, produced in up to 20% isolated yield from coal, are soluble and fluorescent in aqueous solution, providing promise for applications in areas such as bioimaging, biomedicine, photovoltaics and optoelectronics, in addition to being inexpensive additives for structural composites.

Scale‐Up Synthesis of Fragrant Nitrogen‐Doped Carbon Dots from Bee Pollens for Bioimaging and Catalysis

“…A representative atomic force microscopy (AFM) image of the r‐CDs showed densely packed dots on the mica substrate with particle heights from 1.8 to 2.3 nm (Figure S5, Supporting Information), which met exactly with the size range by TEM measurement. The equivalence of particle height with size differentiates the CDs from their counterpart, the graphene quantum dots, which usually have larger size over height 13. In comparison with the CDs in literature fabricated from other biomass (Table S1, Supporting Information), the CDs from bee pollens are the smallest in size.…”

Graphene quantum dots: structural integrity and oxygen functional groups for high sulfur/sulfide utilization in lithium sulfur batteries

“…18,19 Interestingly, GQDs are enriched with oxygen functional groups on their edges, whereby unique properties such as a non-zero bandgap and luminescence on excitation have been reported. [20][21][22] Furthermore, it is expected that GQDs can uniformly cover the target material due to their small size.…”

Production of yellow-emitting carbon quantum dots from fullerene carbon soot

“…After the removal of insoluble substances and large particles by centrifugation, the sample was subjected to dialysis to obtain CQD dispersions. This treatment results in a mean Y of 40 ± 5%, which is much higher than that obtained from acid refluxing of CNTs (2%) [20], coal (10-20%) [23], candle soot (5-10%) [29], and some biomasses such as bagasse (3%) [40]. The as-prepared CQD dispersion contained particles with different sizes.…”

“…These methodologies can be mainly classified into two categories, namely, the "top-down" and "bottom-up" methods. The former includes laser ablation [12][13][14], plasma treatment [15], electrochemical oxidation [16][17][18][19], and acid-refluxing [20][21][22][23][24][25][26][27][28][29][30][31], while the latter is mainly focused on pyrolysis using simple heating and hydrothermal or microwave treatment [32][33][34][35]. Among these methods, the acid-refluxing of raw carbon materials offers a large-scale production of CQDs as it only needs simple instruments and can be easily scaled-up using standard industrial equipment.…”

“…Among these methods, the acid-refluxing of raw carbon materials offers a large-scale production of CQDs as it only needs simple instruments and can be easily scaled-up using standard industrial equipment. Theoretically, nearly all carbon-rich resources such as carbon nanotubes (CNTs) [20], carbon fibers [21], activated carbon [22], coals [23][24][25], petroleum coke [26][27][28], and carbon soot [29][30][31] can be used as the starting materials. For the large-scale production of CQDs, CNTs and carbon fibers can be ideal candidates if their prices can be further lowered in the future.…”