Selective detection of MnO4- in non-standard explosives by nitrogen-doped carbon quantum dots-copper complexes (NCQDs@Cu)

Abstract

Nitrogen-doped carbon quantum dots (NCQDs) with bright yellow fluorescence (quantum yield of 27.3 %) were synthesized via a solvothermal method using 2,3-diaminopyridine as the carbon and nitrogen source and ethanol as the solvent. Subsequently, the NCQDs were reacted with Cu2+ in an aqueous solution, forming nitrogen-doped carbon quantum dots-copper complexes (NCQDs@Cu) with great potential for selective determination of MnO4- ions. The aqueous solution of NCQDs@Cu exhibiting a very weak fluorescence (quantum yield of 2.2 %) demonstrated a significant enhancement (quantum yield of 10.0 %) upon interaction with MnO4-(Turn-on). Furthermore, this enhancement remained unaffected by the interfering conventional or unconventional explosives, inorganic ions, and oxidants. Moreover, a good linear relationship existed between the fluorescence intensity of the NCQDs@Cu and the concentration of the permanganate ions in a range of 0 to 5 μmol/L with a detection limit of 32.4 nmol/L. Additionally, the study investigated the underlying principles of the detection mechanism using advanced technologies such as X-ray photoelectron spectroscopy(XPS), The Fourier-transform infrared (FTIR), ultraviolet visible spectrometer (UV–Vis), fluorescence spectrometer and other methods. Finally, the NCQDs@Cu were successfully applied for detecting MnO4- in simulated and actual unconventional explosives, demonstrating a good correlation with standard methods. Therefore, the developed NCQDs@Cu can be used for rapid on-site inspection in explosive incident scenarios. This new method of using carbon dots-metal complexes as fluorescent probes will also provide new ideas for researchers.