Study On Synthesis And Analytical Application Of Several Fluorescent Nanomaterials

In this thesis,four kinds of fluorescent nanomaterials,boric acid functionalized molybdenum disulfide quantum dots,gold nanocluster,graphitic carbon nitride and their nanocomposites,are used as research objects,and investigated their chemical structures and optical properties.Then these materials are respectively constructed into fluorescent sensors to detect several metal ions in the environment and ascorbic acid.At the same time,the interaction mechanism between fluorescent nanomaterials and detected substance is also deeply explored.The main research contents of this thesis are as follows:1)Boric acid-functionalized molybdenum disulfide quantum dots were synthesized by a simple amidation reaction between 3-aminobenzeneboronic acid and as-prepared molybdenum disulfide quantum dots,which applied for mercury ions detection.This material has excellent thermal stability,light stability and good salt resistance.These good characteristics can be used to build a new fluorescence sensing platform to detect mercury ions with high sensitivity and selectivity.As the mercury ions concentration increased from0.005?mol L^-1 to 41?mol L^-1,the fluorescence intensity of boric acid-functionalized molybdenum disulfide quantum dots decreased linearly,and the detection limit was 1.8 nmol L^-1.This proposed method has fast response,high sensitivity and selectivity for detecting mercury ions in different environmental waters,which is mainly attributed to the mercury ions promoted transmetalation reaction of aryl boronic acid.In addition,the boric acid-functionalized molybdenum disulfide quantum dots-based test paper can be also used to detect mercury ions with the naked eyes under UV light.2)Proposing a simple chemical oxidation-ultrasonic stripping method to synthesize ultra-thin graphitic carbon nitride nanosheets,applying for simultaneous detection of iron ions and ascorbic acid.Adding iron ions,the fluorescence intensity of ultra-thin graphitic carbon nitride nanosheets occured quenching,which was mainly based on the synergistic effect of inner effect and photo-induced electron transfer;after adding ascorbic acid,its fluorescence was restored gradually,which was ascribed to the redox reaction between iron ions and ascorbic acid.According to this phenomenon,building a graphitic carbon nitride nanosheets-based fluorescent switch platform to simultaneously detect iron ions and ascorbic acid,the detection linear range was 0.05-30?mol L^-1 and 0.2-112.5?mol L^-1,and the detection limit was 0.018 and 0.086?mol L^-1,respectively.This method had the advantages of fast response,good selectivity and wide detection range.Additionally,it is also used to determine the iron ions in lake water and the ascorbic acid in human serum.3)Gold nanoclusters with jacinth fluorescence were synthesized by using a simple method that glutathione as a thiolate ligand,which applied for copper ions detection.This material has good light stability,photobleaching resistance and salt resistance.In the presence of copper ions,the fluorescence intensity of gold nanoclusters emission peak at 600 nm was quenched rapidly,which was mainly ascribed to the aggregation-induced quenching mechanism.Based on this mechanism,we constructed a gold nanoclusters-based fluorescence sensor and successfully used it to quantitatively detect copper ions.The detection linear range was 0.05-25?mol L^-1 and the detection limit was 17.4 nmol L^-1.4)A dual-emission water-soluble graphitic carbon nitride@gold nanoclusters nanocomposite was synthesied by in-situ grouth of gold nanoclusters on the surface of water-soluble graphitic carbon nitride,which applied for ferrous ion and copper ions detection.This composite material emits yellow fluorescence,and its direct band gap is different from that of water-soluble graphitic carbon nitride.In the presence of ferrous ion or copper ions,the fluorescence intensity of the nanocomposite emission peak at 520 nm was quenched rapidly,and the fluorescence of the solution changed from yellow to blue,which was mainly attributed to the photo-induced electron transfer mechanism.In addition,cysteine reduction strategies can be used to distinguish the ferrous ion and copper ions.Based on this,we constructed a new type of water-soluble graphitic carbon nitride@gold nanoclusters-based dual-emitting fluorescence sensing platform for detecting ferrous ion and copper ions,and the detection limit was 1.73 and 3.63 nmol L^-1,respectively.This method had highly selective and sensitive to detect ferrous ions and copper ions even if there are interfering cation,and which also exhibited excellent performance in the detection of ferrous and copper ions in environmental water.