Synthesis Of Novel Green Fluorescent Carbon Dots And The Application In Molecular Spectrum Analysis

Carbon dots(CDs)are novel zero-dimensional carbon-based nanomaterials with a particle size of less than 10 nm.They have low manufacturing cost,simple synthesis method,good chemical stability,good biocompatibility,low toxicity,and environment friendliness and unique luminescent properties.In addition,carbon dots synthesized by different carbon sources have different physical,chemical and optical properties.Benefiting from these unprecedented characteristics,CDs have been widely used in analytical detection,biosensing,bioimaging and nanomedicine.Based on the excellent characteristics of CDs,this paper synthesized CDs with green fluorescence by screening carbon sources,and studied the morphology,physical and chemical stability and optical properties of CDs by various characterization methods.The CDs was used as a fluorescent probe to construct a fluorescent chemical sensor for detecting biomolecules,heavy metal ions and environmental pollutants.The response performance and reaction mechanism of the target were also discussed.The main work of this paper is as follows:1.Green fluorescent carbon dots prepared with L-cysteine and H2O2 as precursors for the detection of hematinThe green fluorescent carbon dots were prepared by hydrothermal method using Lcysteine and H2O2 as precursors,and then it was studied by high resolution transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FTIR),fluorescence spectroscopy and ultraviolet-visible(UV-vis)absorption spectroscopy.The CDs have some fascinating properties such as excellentwater solubility,high fluorescence quantum yield,and good stability over a wide pH range(7.0-11.0)and high ionic strength solutions.Hematin is an oxidized form of heme,and the abnormal levels of hematin in the human body can lead to various inflammatory lesions.Hence,there is still a need to establish a rapid,sensitive and efficient method for hematin detection.Excitingly,the fluorescence of CDs can be rapidly and selectively quenched by hematin via the inner filter effect.Therefore,in this paper,the green fluorescent CDs is used as a label-free fluorescent probe for the detection of hematin.the detection of hematin by the CDs fluorescent probe shows a good linearity in the concentration range of 0.5–30 ?M with a detection limit of 0.1 ?M.Finally,the probe was successfully applied to the detection of hematin in human blood samples.2.Green fluorescent carbon dots prepared with sodium salicylate and ethylenediamine as precursors for the detection of Hg2+ and biothiolsIn this chapter,green fluorescent carbon dots were synthesized using sodium salicylate and ethylenediamine(EDA)as precursors.Synthetic CDs have some attractive properties such as good oxidation resistance,excellent water solubility,and excellent stability in high ionic strength solutions or solutions with a pH of 6.0-10.0.Compared to other metal ions,only Hg2+ can quench the fluorescence of CDs,and with the introduction of biothiols,the fluorescence of the CDs/Hg2+ system can be recovered.Therefore,a turn off/on fluorescent dual sensor is constructed using CDs as the fluorescent probe for detecting Hg2+ and biothiols(glutathione,homocysteine and cysteine).In addition,the fluorescent sensor exhibits excellent selectivity and sensitivity,while the linear range of Hg2+ is 0.05-10 ?M with the detection limit of 44 nM.Glutathione,homocysteine,and cysteine all have a linear response at 0.5-10 ?M with the limit of detections are 80,76,and 69 nM,respectively.Furthermore,the fluorescent dual sensor is successfully used to detect Hg2+ in actual water samples and biothiols in human plasma.3.The green fluorescent carbon dots were used as probes to detect MnO-4Using sodium salicylate and ethylenediamine(EDA)as raw materials,the green fluorescent CDs were prepared by one-step hydrothermal method.At the same time,based on the internal filtration effect(IFE),a method for the determination of MnO-4using carbon dots as a fluorescent probe was constructed,which has the advantages of fast response time,high sensitivity,mild measurement conditions(at room temperature),and label-free detection.Based on this,we use this CDs as a fluorescent probe to detect MnO-4 in aqueous solution.The fluorescence quenching efficiency of CDs and the concentration of MnO-4 have a good linear response in the range of 0.1-5 ?M.Thedetection limit is 33 nM.Finally,the method is also applied to the detection of MnO-4content in tap water and lake water.