Construction And Application Of Catalytic Sensing System Based On Metal Doped Carbon Dots Ots

Carbon dots（CDs）are widely used in bioanalytical sensing and catalysis,because of their excellent luminescence properties,low toxicity,good light stability and good biocompatibility.The aim of this paper is to synthesize bifunctional luminescent carbon dots that combine catalytic activity and process indicating function;in order to realize in-situ and real-time monitoring of catalytic reaction process without external indicator.The details are ut infra:1.Silver doped carbon dots（Ag-CDs）were prepared by way of one-step hydrothermal method using citric acid monohydrate and silver nitrate hydrate as precursors,and their structure and optical properties were characterized.Then,based on the complexation between sulfhydryl group and silver ion with the formation of insoluble thiolates,the silver ions fall off from the surface of the carbon quantum dots and result in fluorescence quenching of the carbon quantum dots effectively,furthermore,achieving highly sensitive and highly selective detection of L-cysteine,linear range 2×10^-6 to3.5×10^-5 mol/L,limit of detection 0.25μM.This sensing system has been successfully used for detection of L-Cys in honey.2.Ce doped carbon dots（Ce-CDs）were fabricated by hydrothermal method using disodium ethylenediamine tetraacetic acid disodium and cerium nitrate hexahydrate as precursor.The bis（4-nitrophenyl）phosphate ester salt（BNPP）was used as DNA model substrate to investigate the phosphodiesterase activity of Ce-CDs was studied.Obtained from experimental results that under the catalysis ofCe-CDs,the rate constant of hydrolytic cleavage reaction of BNPP is 1.03×10^-33 min^-1.The maximum absorption range of p-nitrophenol（PNP,cleavage products of BNPP）overlaps partly with the excitation spectrum of Ce-CDs（inner filter effect）,which results in fluorescence quenching of the Ce-CDs effectively.Accordingly,we can monitor the process of phosphate hydrolysis cleavage based on the fluorescence intensity changes of the Ce-CDs catalysts.Finally,the Ce-CDs were applied to the degradation of pesticide chlorpyrifos with satisfactory results.3.Nitrogen and iron co-doped CDs（N,Fe-CDs）were synthesized by one-step hydrothermal method using citric acid and ethylenediamine monohydrate and ferric nitrate nonahydrate as raw materials.The N,Fe-CDs possess good catalytic performance for the oxidation of 3,3,5,5-tetramethylbenzidine（TMB）system by H₂O₂.Next,based on the color fade of blue oxidation products,oxTMB,which is originated from the reducibility of hydroquinone（HQ）,a new,double-parameter（UV-vis spectrum,fluorescence spectrum）method of catalytic sensing for HQ was developed.