Highly fluorescent graphene quantum dots from biorefinery waste for tri-channel sensitive detection of Fe3+ ions

Renewable lignocellulosic biomass can be effectively transformed to value-added products, enabling fast growth of related downstream processing. However, valorization of the by-produced cellulose-poor fraction, which is also in large volumes, is only occasionally reported regarding existing technologies. Here, a simple, general, and effective strategy for fabricating graphene quantum dots (GQDs) from the Miscanthus (MC) biorefinery waste consisting of sugars and depolymerized lignin, is developed. This process involves the fast and selective removal of most lignin and hemicellulose based on mild acid hydrotrope fractionation, with followed hydrothermal carbonization. The as-fabricated MC-derived GQDs (M-GQDs) exhibit several advantages such as few-layer graphene-like single crystalline structure, sulfur and nitrogen co-doping, bright fluorescence, excitationdependent photoluminescence, and long fluorescence lifetime (11.95 ns). Furthermore, M-GQDs present prominent fluorescence reduction in the presence of Fe3+ with good linearity (< 0.995) and very low detection limit (? 1.41 nM). Later, it is found that the observed high sensitivity for Fe3+ is based on a dynamic quenching mechanism, which is caused by the Fe3+-induced increase in both the energy dissipation and photogenerated electron consumption. This work is anticipated to open new opportunities for promoting the integral valorization of biomass and sensitive fluorometric detection of Fe3+.

Automated summary

This study presents a simple, general, and effective strategy for fabricating graphene quantum dots from waste biomass, resulting in quantum dots with excellent optical properties and high sensitivity to iron ions.