Ionic Liquid as a Precursor to Synthesize Nitrogen- and Sulfur-co-doped Carbon Dots for Detection of Copper(II) Ions

A facile approach was reported for the synthesis of nitrogen- and sulfur-co-doped carbon dots(N/S-CDs) by the sulfuric acid carbonization of 1-butyl-3-methylimidazolium 2-amino-3-mercaptopropionic acid(L-cysteine) salt[C(4)mim][Cys]) ionic liquid. The as-prepared N/S-CDs exhibited a good solubility, excitation-dependent emission behavior, and high resistance to photobleaching. Furthermore, the N/S-CDs were employed as a fluorescent probe for detecting Cu2+ in real water samples with satisfactory recovery.