Synthesis And Sensing Investigation Of Fluorescent Gold Nanoclusters,Carbon Dots And Their Nanohybrids

Fluorescent nanomaterials exhibit many advantages,such as tunable morphology and size,superior photostability,as well as multifunction compared to traditional fluorescent molecules.Optical sensors based on fluorescent nanomaterials has formed a major thrust in the fields of chemistry,optics,biomedical and other interdisciplinary fields.In this paper,a series of excellent properties of novel fluorescent nanomaterials including gold nanoclusters?AuNCs?,carbon dots?CDs?and their nanohybrids?Au/CDs?were prepared,and new sensing platforms based on the fluorescence quenching or enhancement have been built,realizing the detection of H₂S,Cr?VI?,ascorbic acid and tetracycline.Chapter 1:We summarized the research progress on synthesis,properties and applications of fluorescent nanomaterials including quantum dots?QDs?,noble metal nanoclusters?MNCs?and carbon dots?CDs?.On this basis we proposed the related research content.Chapter 2:Acetylcysteine stabilized gold nanoclusters?ACC@AuNCs?-based fluorescent sensors had been successfully constructed for H₂S perception.The sensing principle was that H₂S-induced fluorescence quenching of AuNCs which attributed to both the formation of Au₂S between Au?I?in the AuNCs and H₂S and the increased particle size.The proposed sensors showed high selectivity toward H₂S over other anions,amino acids and thiols,and exhibited a stable response for H₂S from 0.002 to120?mol·L^-1 with a detection limit of 1.8 nmol·L^-1?S/N=3?.In addition,the practical application of the designed sensors was further evaluated with water and serum samples,and the tested results agreed well with those obtained by ICP-AES method.The satisfactory recoveries and good precision show that the proposed fluorescent sensors has potential application in biological and environmental fields.Chapter 3:A high dispersibility,sensitivity and good stability of nitrogen doped carbon dots?N-CDs?was constructed by microwave assisted heating method,which taking corn as carbon source,diethylenetriamine?DETA?for passivation agent.In the presence of Cr?VI?,the fluorescence of N-CDs could be quenched dramatically owing to internal filter effect,and when adding into ascorbic acid?AA?,the fluorescence could be recovered.Based on quenching and recovery of N-CDs fluorescence,we developed N-CDs as a dual-channel fluorescent sensor for Cr?VI?and AA detection.The linear ranges for Cr?VI?and AA were 0.0179-575?mol·L^-1 and 18-212?mol·L^-1,respectively.The detection limits?S/N=3?were 0.6224 nmol·L^-1 for Cr?VI?and 0.93?mol·L^-1 for AA.In addition,N-CDs has been successfully applied to the detection of actual samples because of its good repeatability and stability,and a good recovery has been obtained.Chapter 4:Gold nanoclusters?AuNCs?and carbon dots?CDs?were prepared respectively.On this basis,the microwave assisted heating method was used to obtain the fluorescent nanohybrids Au/CDs.The nanohybrids Au/CDs has better optical properties than the original single material because of the combination of the advantages of AuNCs and CDs.Compared with a series of important small molecules,only tetracycline?TCs?can significantly quench the fluorescence of Au/CDs.Thus the sensor system with good selectivity and high sensitivity is constructed.The linear ranges for TCs were 0.02-203?mol·L^-1 and the detection limits?S/N=3?were 2.8nmol·L^-1.It's expected to be applied to the detection of tetracycline residues in food.Chapter 5:We summarized the research results about the AuNCs,CDs and their nanohybrids Au/CDs as novel fluorescence sensors for applications in ions and small molecules detection.Moreover,the follow-up research was prospected.