Tailoring of low grade coal to fluorescent nanocarbon structures and their potential as a glucose sensor.

Lignite is an abundantly utilized feedstock for the facile synthesis of fluorescent carbon dots and carbon nanomaterials. Its value is appreciated as an energy source for combustion for long time. Herein we report a novel top-down strategy to synthesis lignite based fluorescent nano carbon structures by combined acidic oxidation and chemical reflux. The nanocarbon crystallites in lignite are converted to oxygenated nano carbon dots and graphene sheets. They exhibited stable fluorescence property in the visible region depending on their size, functionalities and defects which were highly stable in all the pH conditions. These nanocarbon structures are an effective probe for fluorescent sensing of label-free and selective detection of glucose ions with detection limit as low as 0.125 mM, promising real-world sensor applications. These findings establish a scalable method for the production of fluorescent carbon based glucose sensor from lignite.