Corncob residues as carbon quantum dots sources and their application in detection of metal ions

Abstract

Carbon quantum dots (CQDs) have been attracting extensive attention due to their chemical inertness, high water solubility, size effect, non-toxicity, photoluminescence reaction, photo-induced electron transfer, and tunable light emissions, among other attributes. In the study, the CQDs were synthesized using a simple, green, energy-saving, and efficient hydrothermal method from corncob residues (CRs) obtained after hemicelluloses pre-extraction of corncobs, and the enzymatically hydrolyzed corncob residues (EHCRs). The resultant CQDs were characterized and their applications in detection of metal ions were investigated. The results showed that CRs and EHCRs were good sources for CQDs; the nitrogen doping improved the fluorescence intensity and stability of CQDs; the nitrogen-doped CQDs from EHCRs (E-N-CQDs) exhibited the strongest fluorescence compared with other CQDs; the E-N-CQDs had a strong emission at a wavelength of 414 nm and an optimal excitation wavelength of 318 nm, the strongest fluorescence intensity was found at pH 10.0; the E-N-CQDs were the most sensitive to Fe(III) with the detection limit of 0.75 μmol L−1, which was much lower than the concentration of Fe(III) in human blood (7.52 − 11.82 mmol L−1). The developed E-N-CQDs concept may provide a novel method for the detection of Fe(III) in human blood.