Precise Functionalization Of Fluorescence Sensing System With Amino Recognition Sites For Pattern-Based Recognition

Amino group is an important type of organic functional groups.It can interact with anions through hydrogen bonds,or coordinate with metal ions through their nitrogen atom.It can also be used as nucleophiles to attack carbonyl or other sites,so they can often be used in various fluorescent probes for the detection of anions,metal ions,aldehydes and ketones.Based on the advantages of amino groups including easy to synthesis,easy to be protonated,and high reactivity,we constructed an amino functionalized fluorescence sensing system and applied it to the detection of formaldehyde and heparin.The content of this paper is arranged as follows: Chapter 1 introduces fluorescent probes,and summarizes the applications of amino fluorescent probes in anion recognition and detection of nucleophilic reactive compounds.In Chapter 2,considering the environmental pollution and carcinogenicity of formaldehyde,and its biological activity,the development of new formaldehyde detection probes is still of great significance.We designed and synthesized a series of fluorescent probes(A1-A5)by changing the number and position of the amino group(s).Among them,A1 and A5 can detect formaldehyde under acidic conditions.After reaction with formaldehyde,the fluorescence of A1 decayed or even quenched,while the fluorescence of A5 decayed with a blue shift of the maximum emission wavelength.The sensing mechanism was studied in depth through LC-MS spectrometry,and the results showed that the amino group in the probe molecule reacted with formaldehyde to form a Schiff base structure in an acidic environment,resulting in a change in the fluorescence signal.Compared with traditional small organic fluorescent molecular probes,this method can detect formaldehyde in a "p H insurance" manner,so it can realize the controllable detection.Considering the high sensitivity of A1 to formaldehyde,we further loaded A1 on the filter paper to construct a paper-based sensor material,which was successfully applied to the detection of gaseous formaldehyde.In addition,a three components fluorescent sensor array was also constructed by dissolving A1 in three different p H environments,and successfully applied in distinguishing a variety of aldehydes with 100% accuracy by pattern recognition.The sensor array even has a good ability to discriminate unknown aldehydes.In Chapter 3,considering that heparin is widely used as an anticoagulant drug in clinical practice,but its detection is often indirect,so it is very necessary to develop a new method for heparin detection.We synthesized two amino-functionalized carbon quantum dots by hydrothermal method and named them as L-CD and G-CD.We expect that the carbon quantum dots and heparin will interact through electrostatic and hydrogen bonding to realize heparin detection.Studies have shown that the direct detection of heparin by carbon quantum dots is not effective.The result may be due to the low degree of functionalization of amino groups on the surface of carbon quantum dots,which limits the ability of carbon quantum dots to bind heparin.We then tried to use graphene oxide to improve the detection ability of carbon quantum dots with heparin.However,no obvious improvement has been made.It may be due to the coating of the carbon quantum dots by graphene oxide,which limits the detection capability.Although the detection signals we achieved are weak,these attempts have reference significance for the research of carbon quantum dot surface amination modification and heparin detection.Finally,the main work of this thesis was summarized and an outlook of the amino-functionalized fluorescence sensor system for the sensing of various analytes was discussed.