One-pot synthesis of carbon dots co-doped with N and S: high quantum yield governed by molecular state and fluorescence detection of Ag+

Fluorescent carbon-based nanoparticles, called chronically as carbon dots (CDs), were synthesised from citric acid (CA) and 2-Aminothiophenol (2AT) via an N and S co-doped hydrothermal method. After a series of micro-structural characterisation, N and S elements could be sufficiently doped by means of the heteroatom in the CDs solution. The as-prepared CDs solution showed blue colour fluorescence with the highest QY of 78.6%, and study on the UV–visible and PL spectra further revealed that the outstanding fluorescence of as-prepared CDs mainly originates from the generated molecular fluorophores instead of the surface state. Owing to the strong fluorescence, the as-prepared CDs can be used as a sensing probe for the detection of Ag+ with high sensitivity and selectivity. However, the changes of fluorescence intensity exhibited the complex nature of the quenching mechanism due to the –SH and –NH2 groups on the fringes of carbonaceous cores or molecular fluorophores to aggregate into another fluorescent cores with the assistance of Ag+ ions, which promises a new approach for efficient detection of Ag+ for the application in industrial pollutants.This figure shows citric acid (CA) and 2-Aminothiophenol (2AT) via an N and S co-doped hydrothermal method to prepare CDs with blue colour fluorescence and the highest QY of 78.6%. Owing to the excellent fluorescence, the as-prepared CDs can be used as a sensing probe for the detection of Ag+ with high sensitivity and selectivity, and the changes of fluorescence intensity exhibited the complex nature of the quenching mechanism due to the –SH and –NH2 groups on the fringes of carbonaceous cores or molecular fluorophores to aggregate into another fluorescent cores with the assistance of Ag+ ions, which promises a new approach for efficient detection of Ag+ for the application in industrial pollutants.