Preparation Of Carbon Quantum Dots And Its Application In Analysis Detection

Carbon quantum dots(Carbon dots,CDs)are a new type of carbon nanomaterials.Owing to their simple preparation steps,low cost and stable luminescence properties,they quickly become the substitute to semiconductor quantum dots(QD).In this paper,three kinds of fluorescent carbon dots were prepared by simple microwave method and hydrothermal method.Their structure and performance were studied and they were applied to the detection of pH,Al³⁺,curcumin and morin.For their good biocompatibility and low cytotoxicity,it is applied to cell imaging and further extended to actual samples.The main contents are as follows:Chapter 1:The composition structure and optical properties of carbon dots.On this basis,further outlines the preparation methods and research progress of carbon dots.Chapter 2:In this paper,the nitrogen and phosphorus co-doped green fluorescent carbon dots(N,P co-doped carbon dots,N,P-CDs)were obtained by microwave heating using p-Phenylenediamine,phosphoric acid and ethylenediamine as the carbon source,phosphorus source and nitrogen source,respectively.And their maximum excitation and emission wavelengths are413 nm and 513 nm,respectively.Furthermore the N,P-CDs are excitation wavelength independent.Moreover,a new florescent method for detecting Al³⁺was established with a linear range of 73.0?120.0?mol/L and a detection limit of 21.03?mol/L(S/N=3)based on the fluorescence of N,P-CDs being quenched effectively by Al³⁺statically.The recovery rate was95.0%?102.5%using the new established method for the detection of Al³⁺in actual water samples.In addition,the fluorescence properties of the N,P-CDs at different pH values were also investigated.The results show that the probe can also be applied for pH value detection in the acidic range(pH=4.00?6.00),and cell imaging was performed using laser scanning confocal microscopy(LSCM).The prepared N,P-CDs would be applied as a kind of bifunctional nanometer fluorescent probes that could be used for Al³⁺and pH detection and cell imagingChapter 3:Nitrogen doped carbon dots(N-CDs)were synthesized via one-step hydrothermal method with dopamine and ethylenediamine.The maximum excitation and emission wavelengths of the as-prepared N-CDs were 405 nm and 535 nm,respectively.Based on the internal filtration effect,a method for the detection of curcumin(Cur)in a wide concentration range of97.5 nmol/L?67.9024?mol/L was established.At the same time,it can be visually observed that as the concentration of Cur increases,the color of the N-CDs solution changes from yellow to red.In view of the color change of the solution and the decrease of the fluorescence intensity,the dual-mode Cur detection method of fluorescence quantitative and visual colorimetric semi-quantitative was developed.And this method is used for the detection of Cur in red pepper powder,refined ginger powder,ginger juice.The recovery rate is between 94.00%?110.00%and the relative standard deviation is between 0.30%?2.90%,which has potential application value for Cur in actual samples.Chapter 4:The synthesized B,N-CDs were obtained by one-step hydrothermal method through sodium tetraborate and polyethyleneimine as precursors and a ratiometric determination method for label-free detection of morin was constructed.The as-fabricated B,N-CDs have small size and good dispersibility.After the addition of morin,the B,N-CDs were excited at 340nm and the peak of B,N-CDs at 467 nm decreased,at the same time,a new peak appeared at 560 nm.Quantitative analysis results show that F_{560 nm}/F_467nmhas a good linear relationship with the morin concentration in the range of14.5?32.5?mol/L and the detection limit is 0.3?mol/L.In addition,the constructed B,N-CDs for the detection of Morin in urine has good application prospects.