The Application Of Gold Nanoclusters In The Detection Of Hydrogen Peroxide And Ascorbic Acid

Fluorescent gold nanoclusters(Au NCs),a new type of luminescent nanomaterials,have recently attracted great interest.They are composed of several to tens of atoms.Owing to their unique properties,such as ease of preparation,tunable emission,low toxicity,high photoluminescence qumitum yield,excellent biocompatibility and photostability,Au NCs can be used in the field of bioimaging,ions,small biomolecules and protein detection and so on.Many methods have been developed to prepare the Au NCs.Among them,the protein-directed approach,which could synthesize Au NCs with the reaction condition of green and mild,has attracted enormous attention.In this thesis,we are focusing on the the fluorescent gold nanoclusters applied in the field of the biomolecules detection,and the specific research content is as follows:Part one.The synthesis of the GOx-AuNCs and the application in the evaluation of H2O2 scavenging activity.Glucose oxidase was used for the first time as a stabilizing and reducing agent for the preparation of Au NCs through a simple green "bottom-up" chemical route.The prepared glucose oxidase-stabilized Au NCs consist of about eight gold atoms with an average size of less than 1 nm and exhibit intense blue emission with the maximum peak at 450 nm under the excitation of 360 nm.The fluorescence quantum yield(QY)of the AuNCs was about 1.1%by using quinine sulfate as a reference.The synthetic route is simple and the materials are commercially available and fairly inexpensive.What is more,the AuNCs can be prepared under the conditions of pH 5-12.The maximum emission wavelengths are the same and independent on the pH of the reaction employed,indicating that they had the same size.Then,we use the Fenton reaction which can induce a significant fluorescence quenching of the prepared AuNCs and H2O2 to estimate the scavenging activity of H2O2.A linear relationship between the inhibition ratio and the concentration of H2O2 was observed in the range of 0.5-10.0 ?mo1·L-1 with the detection limit of 0.23 ?mol·L-1.Our method has been successfully applied to evaluate the scavenging activity of H2O2.Part two.Detecting ascorbic acid based on the method of fluorescence resonance energy transfer(FRET).Under the acid conditions,cobalt oxyhydroxide(CoOOH)can react with 3,3',5,5'-tetramethylbenzidine(TMB).The oxidative products of TMB appeared a absorption peak at 654 nm.The as-prepared bovine serum albumin-stabilized Au NCs(BSA-Au NCs)have a strong fluorescence at about 620 nm with excitation at 502 nm which has a large overlap with the absorption peak of the oxidative products of TMB.What is more,ascorbic acid and TMB can competitively react with CoOOH.Therefore,we could use the BSA-Au NCs and the oxidative products of TMB respectively as the donor and acceptor to develop a method of FRET to detect ascorbic acid.In this "turn off-turn on" process of the Au NCs,the recovery of the fluorescence intensity is proportional to the concentration of ascorbic acid in the range from 0.25 to 20.0?mol·L-1 with the detection limit of 0.068 ?mol·L-1.The procedure has been successfully applied to the determination of ascorbic acid in practical sample of vitamin C tablets.In summary,we have successfully prepared blue-emitting glucose oxidase-stabilized Au NCs using "bottom-up" methods.Meanwhile,we realized the detection of certain biomolecules by use of the excellent fluorescent properties of the Au NCs.Our works will provide a reference for the other fluorescent metal nanoclusters used in the field of biosensors.