Synthesis Of Fluorescent Carbon Quantum Dots And Determination Of Histidine And Mycotoxin

In recent years,with people’s pursuit of improved quality of life,food safety and drug safety have attracted more and more attention.In recent years,food safety incidents and drug safety incidents are not uncommon.Therefore,it is very important to establish a simple,rapid,and economical method for detecting food and drugs.Fluorescence method has attracted the attention of the scientific community because of its advantages such as good selectivity,high sensitivity and easy operation.Carbon quantum dots（CQDs）have become popular fluorescent probes for researchers due to their good optical characteristics,biocompatibility,low toxicity,good hydrophilicity,and easy surface functionalization.The carbon source selected in this paper is natural products,and CQDs with good fluorescence properties are synthesized by hydrothermal method,and different"off-on"fluorescent probes are constructed for the high sensitivity and selectivity of mycotoxins in foods and histidine in medicines.Detection.This provides a new method for the fluorescence analysis of food and medicine,and also broadens the application of CQDs in the field of analytical chemistry.The main work of this paper is as follows:1.Using natural product black beans as carbon source and diethylamine as nitrogen source,nitrogen-doped carbon quantum dots（N-CQDs）synthesized by hydrothermal method have good fluorescence performance and water solubility.And through a series of characterization to study its structure,the results show that the N-CQDs have good fluorescence stability and water solubility.Experiments have found that when N-CQDs are modified by Ag+,effective electron transfer is formed,which significantly reduces the fluorescence intensity of N-CQDs.When histidine（His）is added,the Ag+modified on the surface of N-CQDs binds to His and breaks away from the surface,thereby blocking electron transfer,and the fluorescence signal of N-CQDs is restored.And the recovered fluorescence signal has a good linear relationship with the amount of histidine added,and the detection limit can reach 1.1×10^-7μmol/L.Finally,the experiment successfully used the N-CQDs fluorescent probe for the detection of His in drugs,proving its potential application value in actual drug detection.2.Using tea as raw materials,green luminescent carbon quantum dots（T-CQDs）were synthesized by one-step hydrothermal method.The absorption peak of the gold nanoparticles coated with aptamer（Apta@Au NPs）overlaps with the emission spectrum of T-CQDs.The fluorescence of T-CQDs is effectively quenched by the fluorescence internal filter effect,making the fluorescence signal of T-CQDs""Closed",and after adding Ochratoxin A（OTA）,the OTA’s nucleic acid aptamer specifically binds to the OTA,causing Au NPs to aggregate,and its absorption spectrum is red-shifted away from the emission spectrum of T-CQDs,and T-CQDs fluorescence signal"Open"to form an"off-on"fluorescent probe for detecting OTA in food.The detection limit of the experiment is 2.6×10^-9 g/L.This method is used for the detection of OTA in a variety of foods in the local market,and compared with the national standard method,there is no significant difference.It provides a new fluorescence detection method for the determination of OTA.3.Using longan shells as raw materials,LS-CQDs with strong fluorescence properties were prepared by one-step hydrothermal method,and the luminescence characteristics and morphological characteristics of the LS-CQDs were analyzed.The results show that the LS-CQDs have an amorphous carbon structure with uniform size and uniform distribution.The surface is rich in hydrophilic groups such as hydroxyl,carbonyl,and carboxyl groups,so it has good light-emitting performance and water solubility.The experiment found that when in the buffer medium of HEPES at p H=8.00,the fluorescence internal filtration effect occurred between Apta@Ag NPs and LS-CQDs,which caused the fluorescence of LS-CQDs to be quenched.The addition of aflatoxin B1（AFB₁）can interact with Aptamer The specific binding restores the fluorescence signals of Ag NPs clusters and LS-CQDs.A system based on LS-CQDs and Apta@Ag NPs to detect AFB₁ was constructed,with a detection limit of 3.4×10^-9 g/L.This research provides a new method for the detection of AFB₁ and a new direction for the detection of mycotoxins.