Research On Fluorescence Sensing Based On Noble Metal Nanoclusters

In recent years,noble metal nanoclusters have been widely used in catalysis,chemical sensors,electronic devices and bioimaging owing to their unique physical,electrical and optical properties.Metal nanoclusters composed of several to several tens of metal atoms have a size close to the electron Fermi wavelength,and they exhibit significant photoluminescence characteristics due to discrete energy levels and quantum confinement.At present,a large number of fluorescent detection methods using Au NCs and Ag NCs as probes have been developed.These detection methods are generally based on the quenching of the nanoclusters fluorescence by the detection substance.Compared with the fluorescence quenching method,fluorescence enhanced detection methods have higher sensitivity and are less affected by the environment and other quenchers.In addition,since most of the substances only affect the fluorescent intensity of the fluorescent probe,they do not cause change of the emission wavelength and are hardly affected by other disturbances such as particle density and background noise.Therefore,the detection method based on the wavelength shift of the fluorescence peak has better accuracy than that of the fluorescence intensity change.These advantages make detection methods based on fluorescence enhancement and wavelength shift have a wide range of application prospects.In the second chapter,a "signal-on" fluorescence method for determination of hydrogen peroxide(H2O2)and glucose was developed using bovine serum albumin-capped Ag nanoclusters(BSA-Ag NCs)as sensing probe.The prepared BSA-Ag NCs have an average diameter of-3.4 nm and exhibit a red emission at 620 nm.The fluorescence intensity of BSA-Ag NCs could be enhanced by H2O2 with the etching and then formation of smaller clusters.Under the optimum experimental conditions,a linear calibration curve for H2O2 was obtained within the concentration range of 5-300 ?M with detection limit of 1.7 ?M.Coupling with glucose oxidase(GOD)catalytic reaction,the BSA-Ag NCs sensing platform could also be used to detect glucose.The enhancement of fluorescence intensity(F-F0)/F0 was linear related to the concentration of glucose over the range 5-300 ?M with detection limit of 3.4 ?M.This method was successfully applied to the determination of glucose in human serum samples with satisfactory result.In Chapter three,we synthesized BSA-AuAg NCs with an average particle size of about 1.5 nm.The alloy nanoclusters showed a red emission at 650 nm.When the biothiols was added,the thiols group of the biohiols was combined with the alloy nanoclusters to form an Ag-S complex.At this time,the fluorescence emission peak of the AuAg NCs showed a significant red shift.Based on this,we have developed a biothiols detection method based on fluorescence wavelength red shift and successfully applied to the detection of biothiols in human plasma.There is a good linear relationship between the concentration of biothiols and wavelength,with a minimum detection limit of 1.1?M for cysteine,1.3 ?M for homocysteine,and 1.6 ?M for glutathione respectively.