Fabrication And Application Of Fiber-optic Localized Surface Plasmon Resonance Metal Ion Sensor Based On Gold Nanorods

Metal ions(such as iron ions)have important impact on human health.A small amount of metal ions is beneficial to human body,but it will threaten human health when the metal ions are excessive.Therefore,simple and rapid metal ion detection technologies have important research significances in the fields of environmental monitoring and food safety.Traditional metal ions detection techniques,such as atomic absorption spectroscopy,have complex operation and high cost.It is urgent to develop a miniaturized,portable and highly sensitive metal ion detection method to meet the needs of human health and safety detection.Localized surface plasmon resonance(LSPR)owns the characteristics of label free and pollution-free for biochemical sensing.Fiber-optic LSPR sensors have attracted more and more attentions due to their unique advantages,such as simplicity,low cost and resistant to electromagnetic interferences.In order to solve the problems of long detection time,complicated operation and inability to detect on-site for metal ions,in this thesis,we design and construct a type of gold nanorods(Au NRs)based fiber-optic LSPR sensor by utilizing the high refractive index sensitivity and adjustable longitudinal plasmon band of Au NRs,and realize fast and highprecision detection of metal ions.The main research works of the thesis are listed as following:Firstly,we describe the development of SPR and LSPR,and introduce the features and applications of Au NRs.We also investigate the operational principle of surface plasmon resonance sensors,which provides the theoretical foundation for designing Au NRs based fiberoptic LSPR sensor.In this study,we build a fiber-optic LSPR sensing system,in which Au NRs are synthesized by seed-mediated growth method and are deposited on the surface of the fiberoptic using(3-aminopropyl)trimethoxysilane.To meet the rapid need of high-sensitive mercury ion detection technique,we design a Au NRs fiber-optic LSPR mercury ion sensor based on the LSPR characteristics of Au NRs.The detection mechanism is that mercury ions are reduced to elemental mercury in the presence of ascorbic acid;and gold amalgam is rapidly formed on the surface of the Au NRs;then it induces the change of morphology of Au NRs,which leads to the shift of the longitudinal LSPR wavelength of Au NRs.Under the optimized conditions,the detection sensitivity of mercury ion concentration is 0.08 nm/?M,and the linear range of the concentration is 5-100 ?M.Experimental result and analysis show that this LSPR sensor has good selectivity and stability.Next,we control the Au NRs' morphology by etching technique and develop an Au NRs fiber-optic LSPR iron ion sensor.In acidic environment,ferric ions have redox reactions with iodide ions,then its product can etch Au NRs,which further regulates the aspect ratio of the Au NRs.As a result,the change of aspect ratio leads to a blue shift of longitudinal LSPR wavelength.The sensor tests demonstrate that the concentration sensitivity of ferric ions is 0.28nm/?M,and the detection range is 5-50 ?M.The experimental results show that the fiber-optic LSPR iron ion sensor can realize real-time detection of iron ions in complex environments.Finally,we summarize our entire work.The work of this thesis provides a simple and fast detection technology for metal ions detection,which has important practical value in the field of environmental monitoring.