Construction Of A Doped Carbon Dot-based Sensor And Its Detection Of Metal Ions

With the advantages of good water solubility,easy functionalization,low toxicity and photostability,carbon dots are widely used in sensing and bioimaging.Heteroatom doping is an effective strategy to enhance the optical and chemical properties of carbon dots,which can effectively modulate the inherent properties of carbon dots and can broaden the applications of carbon dots in several fields.Doped carbon dot sensors with high stability,low cost and fast response have been widely studied in ion detection.In this paper,three different doped carbon dots（CD1,CD2 and CD3）were prepared by microwave method and used for the detection of metal ions,mainly as follows.:（1）Synthesis and characterization of doped carbon dots:Different doped carbon dots were synthesized by microwave method using citric acid as carbon source and thiourea,borax,urea and boric acid as dopants,respectively.And transmission electron microscopy,infrared spectroscopy and X-ray photoelectron spectroscopy were used to analyze them.The results showed that CD1 and CD2 were doped with N,S and B elements,and CD3 was doped with N and B elements.（2）Research on quantitative analysis of iron ions:Based on the doped carbon dot sensor,the concentration of iron ions in aqueous solution was analyzed by fluorescence spectrometry,UV-visible spectrometry,colorimeter detection method and cell phone APP Photo Metrix PRO detection method,and the results showed that the linear relationship between the concentration of iron ions and the detection value was good,with R² all greater than 0.98,and the applicable ranges were 0～3600μM,0～240μM,0～2.40 m M,0～2.00 m M,respectively.The limits of detection were 14.91 n M,62.56n M,1.33μM,and 28.00μM,respectively,and the limits of quantification were 49.69n M,0.21μM,4.43μM,and 93.35μM,respectively,indicating that the four analytical methods based on the doped carbon dot sensor can quantify ferrous ions,and the limits of detection and detection ranges are better.The limits of detection and detection ranges were better than those of other methods based on carbon dots for the determination of ferrous ions.（3）Qualitative and quantitative analysis of metal ions by doped carbon dot sensing array:CD1,CD2 and CD3 were used as sensing elements to construct a three-channel fluorescence sensing array,which could qualitatively and quantitatively analyze metal ions such as Na⁺,Mn²⁺,Cu²⁺,K⁺,Mg²⁺,Ni²⁺,Zn²⁺,Ca²⁺,Co²⁺,etc.The detection limits were 0.06μM,and the detection ranges were for Na⁺（0.6～36μM）,Mn²⁺（6～120μM）,Cu²⁺（0.6～300μM）,K⁺（12～300μM）,Mg²⁺（30～240μM）,Ni²⁺（18～300μM）,Zn²⁺（3～30μM）,Ca²⁺（120～300μM）,Co²⁺（0.6～300μM）,respectively.Combined with the linear discriminant analysis,the accuracy was found to be in the range of 86.67%～100%.The results indicate that the sensing array can qualitatively and quantitatively analyze common metal ions.（4）Analytical detection of complex samples by the sensing array:combined with LDA,it was shown that the ternary sensing array could accurately identify tea species with an accuracy of 99.23%.Further optimized into a binary sensing array,its discrimination accuracy was 93.85%.It indicates that the sensing array based on doped carbon dots can qualitatively identify complex samples.In summary,three different doped carbon dots were successfully synthesized,and a variety of methods for detecting iron ions were established based on the doped sensors.Sensing arrays were constructed using three doped carbon dots,which can qualitatively and quantitatively analyze common metal ions,and further studies found that the sensing arrays of doped carbon dots have the ability to qualitatively identify complex samples,providing some experimental guidance for the development and application of carbon dots.