Surface adhered fluorescent carbon dots extracted from the harmful diesel soot for sensing Fe() and Hg() ions

Herein, a simpler isolation method has been proposed for using the loosely adsorbed surface-adhered waste from the surface of pollutant diesel soot (DS). The simple extraction protocol is based on Soxhlet-purification using acetone to extract the acetone-soluble fluorescent fraction from the bulk DS. The acetone soluble fraction contains some fraction that should be soluble in aqueous medium. So a gel-separation technique was used to separate the highly fluorescent water-soluble fraction of nano-carbons from the bulk. Transmission electron microscopy analysis reveals the carbon dot (CDs) like morphology of the as-extracted blue-green fluorescent water-soluble fraction. These CDs show strong fluorescence photostability (checked up to 4 hours) and have ∼8% quantum yield. The fluorescent water-soluble CDs are used for the selective sensing of Fe( iii ) and toxic-Hg( ii ) metal ions among most all the tested metal ions. To determine the plausible quenching mechanism, spectral overlap analysis and time-resolved photoluminescence analysis were performed. The fluorescence quenching by Fe( iii ) was mainly attributed to the inner filter effect (IFE) mechanism while in the case of Hg( ii ) ions, quenching was because of the ligand to metal charge transfer (LMCT) mechanism. The sensing of metal ions was additionally supported with the aid of cyclic voltammetry analysis. A simple cost effective isolation method has been described for the extraction of surface-adhered blue-green fluorescent carbon material from the diesel soot and used them for the selective sensing of Fe( iii ) and toxic Hg( ii ) metal ions in aqueous medium.