A Novel Fluorescence Sensor for the Detection of Chloride Ion in Artificial Sweat and Environmental Water With Nitrogen-Doped Graphene Quantum Dots

Abstract

A new fluorescent detection route for chloride ion was designed with Nitrogen-doped graphene quantum dots (N-GQDs), which were prepared by a traditional hydrothermal method with citric acid as carbon source and urea as nitrogen source. The prepared N-GQDs solution was light yellow, and the freeze-dried solid was black. It emitted blue light under ultraviolet light. Meanwhile, The N-GQDs were characterized by TEM, XRD, UV-Vis and fluorescence, the results indicated that the N-GQDs had good dispersibility, photostability and excitation independent emission fluorescence. After addition of Ag+ solution, Ag+ combined to the surface functional groups of N-GQDs, resulting in an obvious quenching of the fluorescence intensity of N-GQDs. Nevertheless, the fluorescence intensity recovered significantly with the addition of Cl- to the N-GQDs/Ag+ system, this was because of AgCl was formed due to the “soft hard acid base principle”. The change of fluorescence intensity had a linear response to the chloride ion concentration in the range of 8.5-300 μmol L-1, with a detection limit (LOD) of 0.1 μmol L-1. To authenticate the application, the proposed method has been successfully used for quantitative analysis of chloride ion in real samples, including artificial sweat and environmental water.

Carbon Dot-Based Room-Temperature Phosphorescent Materials for Information Encryption

“…The optical properties of CDs-based composites were further investigated. As shown in Figure S6, CDs-1 and CDs-2 have a weak absorption peak at 300 nm, which is due to the n –π* transition caused by CO. , However, as the amount of melamine continues to increase, the peak at around 300 nm widens, and CDs-5 has a wide ultraviolet peak at 250 nm, which is due to the π–π* transition caused by CC . CDs-6 has an absorption peak at 340 nm, while CDs-3 and CDs-4 have characteristic absorption peaks at around 450 nm, which are attributed to the n –π* transition caused by CO and CN. , …”