Preparation And Application Of Water-soluble Carbon Quantum Dots Based On Cucurbit[n]uril

Carbon quantum dots?Carbondots,referred to as CQDs?are a new type of fluorescent carbon nanomaterials with uniform dispersion,spherical shape,particle size less than 10nm and stable luminescence.Because of their simple preparation,excellent fluorescence properties,rich surface functional groups,low toxicity,light bleaching resistance,good water solubility and biocompatibility,they are widely used in environmental detection,cell labeling,drug analysis,biological imaging,detection of heavy metal ions and other fields.In recent years,researchers continue to explore and innovate on the basis of existing research,and have made great progress in the synthesis of raw materials,optical properties and application prospects of carbon dots.Researchers found that after the carbon and nitrogen elements were doped and modified,the optical properties of the nitrogen-doped carbon dots?N-CQDs?were more stable and the quantum yield was higher,which further expanded its application.Based on the above contents,through the screening of carbon sources,cucurbit[6]uril and m-phenylenediamine,cucurbit[8]uril and ethylenediamine were selected as raw materials.nitrogen-doped water-soluble fluorescent carbon dots with controllable properties,size and morphology,multiple fluorescence emission wavelengths,highly targeted and cell imaging functions were synthesized by hydrothermal method.A variety of characterization methods were used to study the morphology,structure,physical and chemical stability of carbon dots.Using carbon spots as fluorescent probes,a fluorescent chemical sensor for the detection of heavy metal ions and environmental pollutants was constructed,and biological imaging and PC3 labeling of prostate cells were realized by using carbon dots biocompatibility,low cytotoxicity and excellent fluorescence characteristics.The main contents of this paper are summarized as follows:?1?The blue-green fluorescent carbon dots were prepared by hydrothermal method using cucurbit[6]uril and m-phenylenediamine as precursors.The fluorescence quantum yield of the prepared carbon dots is 5%.The effects of reaction ratio,reaction time and reaction temperature on the fluorescence properties of carbon dots were discussed.the structure and properties of carbon dots were studied by high resolution transmission electron microscopy,X-ray photoelectron spectroscopy,fluorescence spectra,UV-vis absorption spectra and Fourier transform infrared spectra.The characterization results of transmission electron microscope show that the carbon dots were spherical or spherical in shape,and the particle size distribution is 2-8 nm.X-ray electron spectroscopy and Fourier transform infrared spectroscopy show that the carbon dots mainly contain C,O,N three elements.with hydroxyl,carboxyl,amino and other functional groups,so that the carbon dots have excellent water solubility.The carbon dots also have good photoluminescence properties,and the maximum excitation wavelength and emission wavelength are located at 385nm and485nm,respectively.In addition,they also have good stability,and their fluorescence intensity almost do not change under the condition of acid-base and high salt concentration.In this work,the interaction between carbon dots and many kinds of metal ions was investigated,and it was found that Hg²⁺could obviously quench the fluorescence of carbon dots,and the fluorescence of carbon dots/Hg²⁺system was restored with the introduction of cysteine.On the other hand,Al³⁺can slightly enhance the fluorescence of carbon dots.Because of its low cytotoxicity and good biocompatibility,the carbon dots can enter the cell and fully light the whole cell,so it has the potential to be used as a biological imaging reagent.?2?Blue fluorescent carbon dots were synthesized using cucurbit[8]uril and ethylenediamine?EDA?as precursors.The effects of reaction ratio,reaction time and reaction temperature on the fluorescence properties of carbon dots were discussed..Under transmission electron microscope,the particle size of carbon dots was less than10 nm.The carbon dots had good water solubility and photostability,but the salt tolerance was very weak.The interaction between carbon dots and many kinds of metal ions was investigated.It was found that Fe³⁺and Co²⁺could obviously quench the fluorescence of carbon dots.On this basis,a method for the detection of Fe³⁺and Co²⁺was established,and the carbon dots were applied to the imaging of human prostate cancer cells?PC3?.It was observed that the PC3 cells labeled with carbon quantum dots showed a clear blue fluorescence image under green light excitation,and the outline of the cell is consistent with the white light field image.