Rapid Synthesis Of Carbon Dots Through One-pot Microwave-assisted Method And Their Application In Detecting Fe³⁺and Hg²⁺

Carbon dots?CDs?are one of the burgeoning fluorescent nanocarbon materials with good properties,such as low toxicity,stability,biocompatibility,anti-photobleaching,low cost of synthesis,ease of functionalization.Nowadays,CDs have raised more and more concerns in the analysis detection,fluorescence imaging,drug delivery,photoelectric device and many other areas.At present,many materials and methods are proposed for synthesizing CDs.However,current synthesis methods still suffer from some shortcomings:such as complicated synthesis steps and long synthesis time;In the detection of target,there still exist some problems such as poor anti-interference ability and low selectivity.In view of this,we hope to develop a fast and green synthesis method of CDs,explore the detecting mechanism of the CDs and establish a highly selective detection method.In this work,glycerol is used as a microwave reaction solvent and passivation,microwave-assisted synthesis of fluorescent carbon dots was used to develop several fluorescent probes for detecting Fe³⁺and Hg²⁺in water samples,the details are as follows:1.Using citric acid as the carbon source,glycerol as the high boiling point microwave reaction solvent,the CDs were successfully synthesized and passivated through one step microwave-assisted method.The synthesis method is rapid and environmentally friendly.The obtained CDs are with uniform size and good stability.The quantum yield of the CDs is 11.2%.The fluorescence of carbon dots can be selectively quenched by Fe³⁺,while other common metal ions have less effect on the fluorescence of CDs.Based on this feature,the detection method of Fe³⁺in water samples was successfully established.The linear range of detection was between 5-50?mol/L and the detection limit was 2.16?mol/L.The recoveries of the spiked real water samples are at 96.8-106.0%.2.On the basis of the first part,nitrogen-doped carbon dots?N-CDs?was synthesized by microwave assisted method by using citric acid as carbon source,urea as nitrogen dopant.N doping dramatically increases the quantum yield of carbon dots and alters the surface-state structure of carbon dots,which makes the N-CDs selective in detecting Hg²⁺.Based on this characteristic,we have successfully established a fluorescence quenching method to detect Hg²⁺in the real water samples.The linear range of detection was between 5-100?mol/L.The detection limit is 1.7?mol/L.The recoveries of the spiked real water samples are at 97.4-109%and the RSD is less than 3.1%.3.Using cystine as the carbon source,nitrogen and sulfur dopants,glycerol as the solvent,the N,S co-doped fluorescent carbon dots?N,S-CDs?was synthesized through one-pot microwave-assisted method.The as-prepared N,S-CDs are uniform in size with a clear lattice structure.In the experiment,N,S-CDs can be aggregated by Hg²⁺,and FL intensity of the CDs increases with the addition of Hg²⁺.Based on the aggregation induced enhancement effect?AIEE?of the N,S-CDs,we developed a method for detecting Hg²⁺in real samples,which has good selectivity and anti-interference ability.The method has a linear detection range of 1-75?mol/L The detection limit is 0.1?mol/L.The recoveries of the spiked sample are at 92-106%and the RSD is less than2.1%.