| The detection of heavy metal ions is of great significance in the fields of medicine,pharmacy,chemical production and environmental monitoring.The detection of heavy metal ions in the environment can effectively prevent pollution and poisoning events.In order to detect heavy metal ions,people have been trying to use various new sensitive materials.In recent years,due to the rapid development of quantum dots preparation methods and their unique fluorescence properties,the application of quantum dots in the detection of heavy metal ions has been rapidly developed.In particular,the Cd based quantum dot is the main In the same time,the research on the optical fiber sensor has drawn much attention in recent years because of its intrinsic safety,high sensitivity,high detection precision,fast response time,not subject to electromagnetic interference,and the capability to realize remote monitoring,continuous and online.In this study,a new type of optical fiber chemical sensor based on fluorescence quenching effect of quantum dots was developed.This new type of optical fiber used CdSe/ZnS@SiO2 quantum dots as fluorescent indicator mixed in PVA as matrix by Sol-Gel method combined with the current detection methods of heavy metals.Then the gel mixed with CdSe/ZnS@SiO2 quantum dots was fixed in the tip of the optical fiber which is specially dealt with in the purpose of being more compatible for sensor probe.After the formation of sensitive film,a new type of environmentally friendly optical fiber chemical sensor based on the fluorescence quenching effect of quantum dots was developed,which was suitable for the on-line monitoring of the concentration of copper ion.The main content of this paper includes the following four aspects.(1)Preparation and study of CdSe/ZnS@SiO2 quantum dots.The water soluble composite quantum dots(CdSe/ZnS@SiO2)were prepared by inverse microemulsion method and the microstructure was characterized.The results show that the quantum dots have uniform size(about 10nm)and good dispersion.Then the optical properties are studied.The results show that the quantum dots have wide excitation spectrum and narrow emission spectrum(the corresponding wavelength is 600nm).Finally,the principle of detecting copper ion was analyzed.(2)Fabrication of fiber optic sensing probe.After Polishing and cleaning the optical fiber end face,the gel mixed CdSe/ZnS@SiO2 type quantum dots with polyvinyl alcohol was made by using the sol-gel method,and then the gel was attached to the end surface of the optic fiber probe by dip coating method,in the end the sensitive film was made out.(3)Construction of optical fiber heavy metal ion sensing system.By combining the fiber sensor probe with the optical fiber sensing system,a complete set of sensor system for copper ion concentration detection was set up,which can realize the measurement of the concentration of copper ion in aqueous solution.(4)Experimental study on fiber optic heavy metal ion sensing system.The relation between fluorescence quenching rate of the sensor and copper ion concentration was gotten by the measurement of copper ion between 0 and 4?M.The results showed that the sensor system had good linear response to the concentration of copper ion between 0 and 4?M,and the response time of the sensor was 15 minutes,and the sensitivity was 0.625/?M.The sensor system was found insensitive to the acidic aqueous solution in the measurement of sample with pH from 1 to 7,which proved that the sensor system can be used for acidic copper ion detection samples. |
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