Preparation Of Carbon Dots And Its Application In Biosensors

Carbon dots are new stars in the field of fluorescent carbon-based nanomaterials,also known as fluorescent carbon dots or carbon nanodots.They refer to carbon nanoparticles with a size of generally less than 10 nm and a spherical shape with fluorescent properties.Due to its excellent properties,such as controlled photoluminescence,unique electronic properties,photostability,low toxicity and good biocompatibility,it is widely used in many fields,such as biochemical sensing,biomedicine.Bioimaging and catalysis.The application potential of carbon dots has attracted the attention of researchers.This paper focuses on the preparation of fluorescent carbon dots and their applications in biosensors.The preparation of high fluorescence efficiency carbon dots was achieved by a simple and low-cost hydrothermal method,and its structure,composition and optical properties were characterized.The fluorescent carbon dots were used as probes to study their applications in the determination of mercury ions and photoelectrochemical sensors.The paper has three main parts:(1)Firstly,the definition and classification of carbon dots are introduced.The various synthetic methods of carbon dots are summarized.The unique properties of carbon dots are reviewed.And a brief introduction to the application of carbon dots in various fields.(2)Using citric acid and ethanolamine as raw materials,fluorescent carbon dot is obtained by one-step synthesis at 180℃ by hydrothermal method.The effect of hydrothermal reaction time on the fluorescence yield of carbon dots was investigated.It was found that the prepared carbon dots had the highest fluorescence quantum yield of 47.0%under the conditions of 8 hours of reaction.The carbon dots have good dispersibility and dimensional uniformity(the size is mainly distributed at 3.5-5 nm and the average particle diameter is 4 nm).The optimum excitation and emission wavelengths of the carbon dots are 344 nm and 447 nm,respectively,and the carbon dots exhibit excitation-independent emission.And we found that the carbon dots exhibit up-conversion fluorescence properties.The results of Fourier transform infrared spectroscopy indicated that the surface of the carbon dots contained a large amount of hydroxyl groups,carboxyl groups and amino groups.In the mercury ion measurement,the hydroxyl group and the carboxyl group on the surface of the carbon dot can interact with Hg2+,and the fluorescence of the carbon dot is quenched by photoinduced electron transfer.The method for quantitative determination of Hg2+ concentration based on the fluorescence intensity of carbon dots established by this mechanism has a linear range of 2～10 μM,a linear correlation coefficient of 0.996,and good selectivity and sensitivity.(3)Since the carbon dots themselves have excellent electronic properties and up-conversion fluorescence emission properties,we combine the carbon dots synthesized in the previous chapter with TiO2 to greatly improve the photoelectric response of TiO2 under visible light.The TiO2 nanotube array was prepared by secondary anodization,The carbon dots are then synthesized in situ on the surface of the TiO2 nanotubes to finally obtain a CDs/TiO2 composite.Glucose was detected by photoelectrochemical method after loading glucose oxidase.The detection range was 0.1-18 mM,and the detection limit(3σ)was 0.027 mM.