Construction Of Fluorescent Nanoprobes Based On Carbon Dots/Cu Nanoclusters For Detection Of Pollutants In The Environment

In recent years,due to the excellent optical properties of fluorescent nanomaterials(carbon dots,metal nanoparticles,semiconductor quantum dots,and nanocrystals),such as stability,sensitivity,and size dependence,providing an effective channel for environmental pollutants detection by establishing qualitative,quantitative and real-time analytical methods.Here,we discuss various environmental detection schemes for organic and inorganic contaminants by synthesizing novel carbon quantum dots to construct ratiometric fluorescent probes,and prepareing Cu nanoclusters by aggregation-induced luminescence effects(AIE).As a new type of carbon material,carbon dots can control their physical and chemical properties through surface treatment,they have mature characterization methods and the advantages of simple preparation method and environmental friendliness.The carbon quantum dots have been well used in the field of environmental detection,and related research has also emerged.At the same time,copper has a wide range of sources,abundant reserves and low cost,which provides some more attractive advantages for the study of Cu nanoclusters and their practical applications.Based on the above introduction,this thesis mainly describes the synthesis of new fluorescent carbon dots,the construction of carbon dots-based ratio fluorescent probes and the preparation of new copper nanoclusters.1.Conventional carbon dots synthesis uses linear organic amines.In this paper,a polyamine compound of cyclen with a cyclic structure,is dissolved in 10 ml of water with 1 mmol of citric acid.Then,one-step synthesis of carbon dots with bright blue emissions by microwave method,and the quantum yield was as high as 27.6%.The dispersed carbon dots solution has good solubility and will not precipitate when placed for a long time.Meantime,it has high stability,and even if it is stored in the natural environment,there will be no obvious fluorescence decay.These advantages make their practical application not very limited.In addition,by using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy and other characterization methods,it was confirmed that the emission of the functional carbon dots originated from the reaction between the carboxyl group of citric acid and the amino group of cyclen.That is,the center of the amide bond and its derivative.Because the surface of the prepared carbon dots is rich in functional groups,it can be well applied in many fields such as chemical sensing,biological imaging,and anti-counterfeiting detection.2.The surface of the functional carbon dots synthesized by the crosslinking-polymerization-carbonization process contains a large number of uncarbonized cyclic structures,which provides a site for the construction of detection probes.These binding sites on the surface of the carbon dots can be used to complex with metal europium ions.Subsequently,100 u1 of synthesized carbon dots,60 ul of lanthanum nitrate(0.1 mol/L)and 840 ul of ultrapure water were mixed and shaken for 5 h using a constant temperature shaker to form a stable ratio fluorescent probe.For europium ions,it has a weak ability to absorb excitation light,but when it is combined with tetracycline,due to the ?-diketone structure of tetracycline,this unique structure can complex with europium ions while attenuating the possibility of non-radiative transitions,thereby transferring the absorbed energy to Eu3+ through energy transfer,increasing the luminescence intensity of europium ions.Further,the fluorescence photographs of the carbon dot solution under different tetracycline concentrations are analyzed for RGB values.The tetracycline concentration value was quantified by the intensity ratio of the red emission value of the europium ion and the blue emission value of the carbon dots,and a good linear relationship was obtained.Using the triple signal-to-noise ratio,the detection limit was calculated to be 5.2 ng/ml(11.7 nM).Therefore,the obtained carbon dots-based ratio fluorescent probe can be used for detection analysis of tetracycline in the environment,3.Unlike silver or gold nanoclusters,the luminescence of single copper nanoparticles is weak.Due to the influence of AIE process,CuNCs show strong luminescence after aggregation.Traditionally,aggregation-induced luminescence phenomenon of copper clusters is used to construct chemical sensors.In turn,we use the AIE process to detect copper ions.Specifically,a working solution was prepared by mixing 800 ul of tetrahydrofuran,140 ul of ultrapure water,and 60 u1 of glutathione(0.5 M).Subsequently,a series of different concentrations of metallic copper ions were added to the working solution and spectral data were recorded.When copper ions were added to the working solution,they were quickly reduced to small copper nanoclusters.Immediately thereafter,the copper clusters aggregated to produce bright fluorescence emissions.The curve of the fluorescence enhancement of the working solution with the change of copper ion concentration was obtained by experiments.A good linear relationship indicates that they are closely related,and the detection limit was calculated to be as low as 0.17 uM.Therefore,based on the increased quantum yield of CuNCs after aggregation,a method for rapidly detecting the concentration of copper ions in the environment can be devised.