Preparation Of Plasmonic/magnetic Nanocomposites And Their Application In Colorimetric Sensing

The development of colorimetric sensors with fast response,excellent sensitivity and selectivity which can meet the demands of instantaneous detection,convenient operation,visualized and accurate results is always the hotspot in the field of analytical chemistry.Metal nanomaterials are unique in structure and performs superior optical,electrical,magnetic and chemical properties,which provides new ideas and broadens the research field for the development of colorimetric sensors.Focusing on the unique properties of metal nanomaterials,this paper includes six parts:The first chapter is the introduction which includes the basic knowledge of colorimetric sensor,the introduction of colorimetric method,the concept of chemical sensor,the construction of metal nano-colorimetric sensors and a brief description of the research.The second chapter investigates the Ag Pt-Fe₃O₄ for colorimetric detection of H₂S by simulating enzyme activity.The dumbbell-type heterogeneous nanoparticles with multiple metal centers were successfully prepared by green and mild aqueous phase synthesis method.Besides,the uniform metal nanoparticles were obtained with good morphology and high yield.The natural peroxidase activity of Ag Pt-Fe₃O₄ in catalyzing color reaction was studied under the presence of hydrogen peroxide and TMB substrate,which showed better performance than natural enzymes.By means of the poisoning of H₂S molecules on this material,a colorimetric sensor with high sensitivity and selectivity towards H₂S molecules was established.Combining the chromatic aberration method,the recognition limit of the eye was greatly reduced.In the third chapter,the simulating enzyme activity of Au-Fe₃O₄ nanoparticles in colorimetric detection of biological thiol was studied.Similarly,the dumbbell-type heterogeneous Au-Fe₃O₄ nanoparticles with catalase activity were prepared by aqueous phase method,and the natural peroxidase activity of the material was investigated in the presence of hydrogen peroxide and TMB substrate.Taking advantages of the formation of Au-S bonds between sulfhydryl group in biological thiol and noble metal,the colorimetric sensor with high sensitivity and selectivity to biological thiol was established,and this colorimetric sensor was applied to detect the thiol content in human urine samples.The fourth chapter is based on preparing the silver/gold nanocomposites and constructing enzyme-free glucose sensors.Firstly,silver/gold nano probe was synthesized by reducing chloroauric acid by ascorbic acid and depositing gold frame on silver triangle sheets.Then taking advantage of glucose oxidase ability of gold and the local surface plasma resonance effect of silver/gold nanostructure,a glucose detection method based on silver/gold nanostructure etching was explored.TEM characterization results showed that the silver nano-sheets were triangular and they were wrapped by gold to form the core/shell structure.The UV detection limit of glucose is 1m M of this method,the glucose concentration has good linear relationship in the range of 1-30 m M,and the correlation coefficient was 0.988.Therefore,a fast visualized and reliable glucose detection method is obtained in this study,which provides a new idea for the portable and rapid detection of blood glucose and urine sugar.The fifth chapter focuses on the preparation and application of Au_shell-Fe₃O₄ nanoparticles.The Au_shell-Fe₃O₄ nanoparticles with wide and adjustable LSPR was synthesized by mild aqueous method.These nanomaterials are believed to show a huge potential in the field of catalysis,biomedical and drug release.Finally,we summarize the work in this thesis and give some personal perspectives on the directions of future research in this field.