Research On The Controlling Growth And Optical Properties Of Gold And Silver Nanostructures

Nanometer, one billionth of a meter, brings about the most promising nanomaterial in the21thcentury. After80s of20th century, researchers found that when the bulk material was decreasedinto nanometer sized particles, properties （in electronics, magnetics, optics, thermology, catalysis,biology et al.） of nanomaterials change greatly compared with normal bulk materials. Amongvarious nanomatierals, noble metal nanostructure is one of the research hotspots, exhibiting uniqueoptical property that originated from the surface plasma resonance. It is found that the frequencyand band of surface plasma resonance absorption closely correlated to the size and shape ofnanoparticles. Therefore, the design and realization of the size-and shape-controllednanostructures synthesis are important for the study of tunable optical property and theirapplications in many fields, such as photonics, sensing, catalysis, biological science.The main content of this dissertation involves some items, involving design a simple andeffective method for the synthesis of size-and shape-controlled gold and silver nanostructures;Structures, morphology and spectra characterizations carried out by field emission scanningelectron microscope （FE-SEM）, transmission electron microscopy （TEM）, high-resolutiontransmission electron microscopy （HRTEM）, atomic force microscope （AFM）, X-ray diffraction（XRD） and UV-visible spectrometer （UV-Vis）; Optical properties of and growth mechanisms ofthe obtained nanostructures. The main results of this work are listed as follows:1. We present the development of nanotechnology, properties and application of nanomaterials,and give a summary on the common synthesis the noble metal nanoparticles.2. Gold nanoplates with star-like, shield-like and polygonal shapes are successfully achievedthrough a hydrothermal method with the presence of surfactant agent PVP. The possible growthprocess of Au nanoplates was proposed through analysis on the nanostructure.3. A rapid seed-based method for the production of silver nanoplates is presented at a roomtemperature. The position of the main plasmon resonance of the nanoplates can be readilycontrolled through adjustment of the amount of the silver precursor that added into the growthsolution.4. Silver nanocrystals including single-crystalline cubic nanostructures and multiply twinedpolyhedrons have been synthesized by a hydrothermal method with the presence ofpolyvinylpyrrolidone （PVP）. Field-emission scanning electron microscopy （FE-SEM）,transmission electron microscopy （TEM）, X-ray diffraction （XRD） and UV-Vis-NIR spectrometerhave been employed to investigate the morphology and optical properties of the products. Theresults show that the shapes of Ag nanostructures are mainly correlated to the molar ratio betweenPVP and AgNO₃. The plausible growth mechanisms for the nanostructures were present, in which PVP servers as both reducing and surfactant agent for the reduction of Ag precursor and growthmodifier of the nanocrystals.