Preparation Of Carbon Quantum Dots And Their Application In Optical Biological Detection

The detection of important biomasses in human body is of great significance for the prevention and early diagnosis of many diseases.Adrenaline is an important catecholamine hormone and neurotransmitter.Accurate determination of adrenaline concentration can help to diagnose many diseases,such as hypertension,Parkinson's disease and so on.Nitric oxide(NO)is an important messenger molecule in vivo,and the effective detection of NO is of great significance in the field of clinical medicine.Among the methods for detecting the above two biomasses,the fluorescence analysis method has been widely studied and applied due to its many advantages such as good selectivity and high sensitivity.Carbon quantum dots(CQDs),as a new type of fluorescent nanomaterials,have the advantages of excellent fluorescence performance,good chemical stability,low toxicity and so on.They have great application potential in biochemical detection and cell imaging.This thesis was financially supported by the National Natural Science Foundation of China(No.61575150).In this thesis,different carbon quantum dots were synthesized as the fluorescent probes for adrenaline detection and the optical sensing materials for fiber optic NO sensor,and the fiber optic NO sensor was fabricated.The detection of adrenaline and NO were realized,which were of great scientific significance.The main research contents are as follows:(1)CQDs-1 were prepared with hydrothermal method using citric acid and ammonia as the raw materials.CQDs-2 were prepared with microwave method using citric acid and o-phenylenediamine as the raw materials.The optical properties,cytotoxicity and fluorescence imaging of the two carbon quantum dots were studied.Using quinine sulfate solution as a reference,the quantum yields of CQDs-1 and CQDs-2 were detected to be 38.6%and 63.7%,respectively.(2)Based on the principle of fluorescence quenching,CQDs-1 were used as a fluorescent probe for the detection of epinephrine.The effect of different detection conditions(such as the concentration of CQD-1,reaction time,p H value)on the detection was studied,and the optimal detection conditions were obtained.According to Stern-Volmer equation,the standard curve for detection is I₀/I=0.0384[AD]+0.7568(R²=0.992).The detection range is 10?100?M and the detection limit is 1.1?M.The sensor has good selectivity for adrenaline detection;(3)Using CQDs-2 as the optical sensing material for NO detection and fixing the cellulose acetate film wrapped with CQDs-2 on the end face of the 600?m diameter fiber,an optical fiber sensing probe was prepared.A new optical fiber NO sensor is designed and constructed by combining with optical fiber sensing technology.The performance of the optical fiber sensor for NO detection range,detection limit,repeatability and anti-interference is studied.The results show that the detection range of NO concentration is 10?100 n M,the limit of detection is 2.1 n M,and the standard linear equation is:I₀/I=0.00402[NO]+1.02339(R²=0.980).The sensor has good selectivity and can be used for the detection of nitric oxide in actual human serum.