Phosphorus-containing Carbon Dots And Their Application In Biothiols And Hg²⁺ Detection

In recent years,Carbon Quantum Dots?CDs?,a new favorite of the carbon nanofamily,has drawn the attention of researchers all over the world.Because it is superior to other fluorescent probes,for example,small particle size,low molecular weight,low toxicity,good biocompatibility,etc.It has been widely used in biological image,sensing,labeling and so on.In environmental monitor,it can be used as fluorescent probes to detect some toxic substances in water environment.In this paper,we use the excellent fluorescence properties of carbon quantum dots,a fluorescent probe was synthesized and designed to detect biothiols.The main work is as follows.In the first part,we study a mercury ions(Hg²⁺)mediated containting-phosphorus carbon dots?PCDs?,as a selective fluoresce probe detect?Cys?,and homocysteine?Hcys?.PCDs obtained by hydro–thermal reaction are sensitive to Hg²⁺ions and its fluorescence can be significantly quenched owing to Hg²⁺strong oxidizing property.Interestingly,the weak fluorescence of Hg²⁺–mediated PCDs could be gradually recovered with the addition of GSH,Cys,and Hcys.This can be attributed to the formation of Hg²⁺-S complex due to the super affinity of Hg²⁺–sulfydryl bond.The formation of Hg²⁺-S complex extremely reduces the oxidation ability of Hg²⁺.Thus,the green fluorescence of PCDs is switched on.Under optimized conditions,a good linear relationship between optical response and biothiol concentrations can be obtained in the range from 0 to 30?M for GSH?0-45?M for Cys,and 0-15?M for Hcys?.The limit of detection?LOD?for GSH,Cys,and Hcys are found to be 0.035,0.06,and 0.02?M,respectively.Furthermore,the present Hg²⁺–mediated PCDs assay exhibits a high selectivity for GSH,Cys,and Hcys and has been successfully used to detect the total biothiols content in human urine samples.In the second part,we designed a CdSe/ZnS core-shell quantum dots(?_em=630 nm)as a fluorescent source,the silica nanoparticles doped with PCDs.Then mix the QDs and PCDs together.It realizes the dual-emission ratiometric probe.The addition of Hg²⁺into the dual-emission nanocomposites system only quenched the green fluorescence.The fluorescence intensity of two kinds of quantum dots and carbon dots with different emission wavelengths also changed with the increase of Hg²⁺concentration.Therefore,a ratio fluorescence probe is designed.