Construction Of Three New Sensing Methods Based On Functionalized Doped Carbon Dots

Carbon dots?CDs?are a new type of zero-dimensional fluorescent nanomaterials.Since the first discovery of CDs in 2004,the past decade has witnessed the vigorous development of CDs in multi-mode biological imaging,sensing,photochemical energy storage and catalysis.CDs haves been widely used as a fluorescence probe because of its excellent photostability,tunable emission wavelength,good water solubility and low toxic and side effects.In this paper,functionalized carbon dots were prepared by hydrothermal method,based on the interaction between CDs and analytes to produce"ON-OFF-ON"or"ON-OFF"system response,established three new sensing methods,and successfully applied the methods to detect hydroquinone?HQ?,vanillin and 5-aminosalicylic acid?5-ASA?.The work of this thesis consists of three parts:1.Fluorometric determination of hydroquinone by using blue emitting N/S/P-codoped carbon dotsWe have synthesized N/S/P codoped CD with bright blue fluorescence from glyoxal and isocarbophos and further explored the use of CD-Fe³⁺system to detect HQ efficiently.This strategy was also efficient for HQ detection with high specificity in the presence of CC and RC.N/S/P codoped CD were prepared through hydrothermal heating of precursor materials at 140°C for 4 hour.In the procedure,glyoxal was used for carbon and oxygen,and isocarbophos was employed for nitrogen,sulphur,and phosphorus sources,respectively.Due to the abundant functional groups covering on the surface of CD,CD can coordinate with Fe³⁺easily,inducing CD aggregation and fluorescence quenching.When HQ was added to CD-Fe³⁺system,disaggregation of CD occurred owing to the redox reaction between HQ and Fe³⁺.The interaction of HQ and Fe³⁺resulted in fluorescence recovering of CD.Based on the distinguished fluorescence changes of CD,HQ can be identified.Moreover,it was demonstrated that this method was applied for detection of HQ quantitatively in developer and spiked water samples.Importantly,such a design strategy may be able to extend to other analytes in environmental samples.2.Construction of vanillin sensing method based on carbon dots fluorescence systemWe have developed nitrogen-doped carbon dots?N-CDs?as new fluorescent probes for the quantitative detection of vanillin.N-CDs are synthesized by this simple,low-cost,one-step hydrothermal carbonization pathway using glucose as a carbon source and tyrosine as N-dopant.At 330 nm excitation,the fluorescence of the synthesized N-CDs showed a strong blue color at 430 nm.The fluorescence intensity of N-CDs can quenched by the addition of vanillin,which may be due to the formation of non-fluorescent ground state complexes.Under the optimal conditions,the linear response of the N-CDs fluorescent probe was observed in the concentration range of 1.0²60?M with a detection limit of 0.25?M.Based on the N-CDs fluorescent probe,the detection result of vanillin is satisfactory,the method for detecting vanillin could be further applied to foods?essential oils,biscuits and yoghurts?.3.Construction of 5-aminosalicylic acid sensing method based on carbon dot fluorescence systemWe use adenosine triphosphate?ATP?and p-methylaniline as precursors,prepared N/P-codoped carbon dots?N/P-CDs?with moderate quantum yield and bright blue fluorescent.The luminescent properties of N/P-CDs were optimized by adjusting the precursor ratio?ATP:p-methylaniline?,reaction temperature and reaction time,and a high-sensitivity 5-ASA sensing platform was constructed by fluorescence detection technology.When the concentration of 5-ASA in the range of 0.50¹30?M,it show a good linear relationship with the fluorescence intensity of N/P-CDs,and the detection limit is 0.13?M.The method is simple,sensitive and low cost,and has been successfully applied to the detection of 5-ASA in practical drugs.