Fluorescence characteristics and bioimaging application of carbon dots extracted from sugar mill flue gas

Bagasse is a by-product of the sugar industry, and its combustion generates dust containing a fraction of ultrafine particles smaller than 10 nm. In this study, carbon dots (CDs) were separated and extracted from bagasse combustion dust using a simple water-based purification method. The structure and optical properties of the CDs were characterized and analyzed. The results suggest that the CDs contain graphitic or graphene-like carbon domains, together with small amounts of N, S, Cl, and Na impurities in their lattices. The shells of CDs are mainly composed of functional groups such as hydroxyl, carbonyl, carboxyl, epoxy, and amino groups. The CDs exhibited blue photoluminescence under UV excitation and blue anti-Stokes emission under 675 nm excitation. The observation of this blue emission after insertion of a long-pass filter in the excitation path supports the assignment of this emission to anti-Stokes photoluminescence. The down-conversion photoluminescence (DCPL) intensity was approximately ten times higher than that of the anti-Stokes emission. The temperature-dependent PL response suggests that these CDs may be further explored for fluorescence-based temperature sensing. In addition, preliminary cell-imaging results demonstrate their feasibility for laser confocal bioimaging. This study provides a potential strategy for the resource utilization of biomass combustion soot and the reduction of solid particulate emissions.