Dual-emissive waste oil based S-doped carbon dots for acetone detection and Cr(VI) detection/reduction/removal

Dual-emissive water-dispersible sulfur-doped carbon dots (S-CDs) were prepared through simple heat treatment of canola oil as a carbon source. The S-CDs revealed excitation wavelength-dependent and independent emission band in UV (327 nm) and the visible region (633 nm), respectively. The fluorescent S-CDs ranged from 4 to 9 nm in size and exhibited selectivity and linear "turn-off" fluorescence in the presence of Cr(VI) and acetone, making them potential nanosensors for their detection. Concentration-dependent red-shift of the S-CDs emission spec-trum was observed in the presence of acetone, via incremental quenching of the peaks at 327 nm and 633 nm, accompanied by an emergence of new peak at adjacent higher wavelength. Linearity was observed in the range of 0.01-0.08 vol%, with a limit of detection (LOD) of 0.01 vol%. The nanoprobe was tested in spiked tap and river water for Cr(VI) along with acetone detection assays in spiked human urine and phosphate buffer solution. XPS analysis revealed the reduction of Cr(VI) to Cr(III) in the presence of S-CDs, a less toxic form. In addition to the optical detection, fluorescent probes incorporated into poly vinyl alcohol (PVA) matrix could be used for the removal of Cr(VI) ions from the contaminated water. Hence, the proposed S-CDs have potential applications as highly sensitive, selective, cost-effective, and environmental friendly sensors of acetone and Cr(VI), as well as for developing tools for the reduction and removal of Cr(VI) from contaminated water.