Guanhong Liu, Xinyi Li, Peipei Ren, Youtao Song

College of Environment, Liaoning University

Zhiyue Yu, Fan Yang, Jun Wang

College of Chemistry, Liaoning University

Abstract

In this study, we developed a new fluorescent strategy for detecting glucose based on copper ions supported on N-doped carbon quantum dots (N-CQDs) to form Cu²⁺/N-CQDs nanocomplexes. The N-CQDs were characterized using high resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The optical properties of the N-CQDs were also determined by ultraviolet–visible and fluorescence spectroscopy. The proposed strategy comprises three steps: quenching the fluorescence from the N-CQDs with Cu²⁺ ions, producing Cu₂O and gluconic acid via the Cu-catalyzed oxidation of glucose, and leaving Cu²⁺ ions on the surfaces of the N-CQDs to recover the fluorescence intensity. In the Cu²⁺/N-CQDs nanocomplexes, the Cu²⁺ ions act as quenchers to decrease the fluorescence from N-CQDs by surface energy transfer. The Cu-catalyzed oxidation of glucose reduces the Cu²⁺ ions to form Cu₂O, which frees the Cu²⁺ ions from the surfaces of the N-CQDs and restores the fluorescence of the N-CQDs. Therefore, the change in the fluorescence depends on the concentrations of Cu2+ and glucose. Under optimal conditions, the quantitative analysis of glucose had a detection limit of 0.455 μM. Thus, Cu²⁺/N-CQDs can be applied as nonenzymatic glucose probes to detect low concentrations of glucose. This method also has advantages due to the facile preparation of the nanomaterials, as well as high analytical sensitivity and low experimental costs.

Read the full article here:   88-Nonenzymatic detection of glucose based on Cu2+ catalytic oxidation on N-doped carbon quantum dots.pdf