Silver Micro-Nanomaterials: Synthesis And Application For Surface Enhanced Raman Spectroscopy

Surface Enhanced Raman Spectroscopy is a powerful detecting technique, which has attracted much attention because of its advantage of sensitivity and convenient detection. With all these advantages of Surface Enhanced Raman Spectroscopy, it has a broad application on health care, environmental safety, bioscience and national defence safety. The surface enhanced Raman scattering(SERS) mainly denpendent on the nanostructure of substrates. The localized surface plasmon resonance can significantly increase the strength of Raman signal. So considerable efforts has been devoted to the design and preparation of SERS substrates. With the development of nanotechnology, different preparation methods have been studied successfully. In this dissertation, the synthesis and SERS performace of silver(Ag) micronanomaterials have been studied. The various fabrication methods of micro and nanostructure were conducted to obtain a series of SERS substrate with different morphologies and SERS performance. Our study provides a value theoretical and experimental evidence for the further development of SERS theories and real-world application. The important and valuable results in this dissertation can be summarized as follows.1. Ag micro-nanoparticles were synthesized by reducing silver nitrate with ascorbic acid as the reductant. The influencing factors of Ag micro-nanoparticles have been studied, such as concentration, solution constituent and mixing method. Flower-like silver(Ag) micronanoparticles which were assembled by nanosheet were synthesized in a higher concentration of reaction solution with vigorous stirring. It has a good SERS property because the large surface area and more cracks. The limit of detetion of R6 G is 10-7 M. The enhancement factor could be achieved 1.3×105.2. Ag nanoparticles were synthesized by photochemical synthesis. The influence of concentration of solution, PVP and stirring on morphologies of Ag nanoparticles have been studied. The results indicate that stirring can accelerate the reaction and the reaction can be controlled by illumination. PVP also has a great influence on the transformations of Ag nanoparticles. Without PVP, the Ag nanoparticles will be coalesced together in the process of particle growth. With PVP, the Ag nanoparticles growth is depended on the epitaxial growth.3. The Ag dendritic micro-nanomaterials were deposited on the surface of AAO or filter membrance by electrochemical deposition method. Electrodeposition potential, reaction time and the constituent of solution have been studied. The application of AAO or filter based Ag dendritic micro-nanomaterials as SERS substrate has been researched. The study shows that the limit of detetion of R6 G is 10-11 M and its enhancement efactor is 1.31×106. Furthermore, the AAO-based Ag dendritic micro-nanomaterials as SERS-active substrate can be used to detect fluoranthene which cannot be attached directly on the surface of noble metal without modification.4. The FDTD Solutions software was used to study the electmmagnetic enhancement of silver dendrities. When excitation light source(the wavelength is 785 nm) was perpendicular to the Ag microstructures with a neighboring branch separation of 90 nm and its polarization orientation is paralleled to the trunk of dendritie, the electmmagnetic filed has the strongest enhancement. It also can be concluded that the transformation of plasma has effect on the electmmagnetic enhancement.5. AAO decorated with Ag dendritic micro-nanomaterials as SERS substrate to detect gas analytes has been investigated. A gas detecting device is designed. The detections for the vapor of 2,4-DNT, formaldehyde and xylene by the device have been studied. This research provides a significant hint for the further investigation for the application of rapid real-time detection of trace gas analytes.