Study On The Synthesis And Optical Properties Of Gold And Silver Nanowires

In recent years, noble metal nanomaterials have been of extensive interest in electronic, catalytic,optical and many other areas for their special physical and chemical properties. Driven byfoundational research and technological usage, the synthesis of noble nanostructures has achievedgreat progress. Nanostructures with different shapes have been synthesized successively. Shapecontrol provides one of the most powerful means to tailor the properties of noble metal nanostructures.Among various noble metal nanomaterials, the highly chemical inertness and low resistivity of gold,the highest electrical and thermal conductivities of silver, and their unique surface plasmon resonance(SPR) properties gained gold and silver nanomaterials extensive interest and research. In this paper,we studied the synthetic innovation of gold and silver nanostructures with high purity and excellentproperties. First, we used a new wet chemistry method to synthesize gold nanowires with high aspectratios on the surface of anion exchange resin. Secondly, an improved hydrothermalpolyvinylpyrrolidone (PVP)-directed polyol process was applied to synthesize silver nanowires. Theeffects of experimental conditions on the products were further studied. Finally, silvernanodecahedrons were also synthesized using hydrothermal method. Specific work can be detailed asfollows:1. The synthesis of gold nanowires. A new wet chemistry method was used to synthesize goldnanowires. Ion exchange resin can exchange with ions in the solution so that AuCl-4anions can beimmobilized on the surface of anion exchange resin beads. Heated by oil bath, the aqueous solution ofEDTA-2Na was used as reducing agent to reduce AuCl4-anions. Gold nanoparticles are polarized bythe charged resin matrix and longitudinally aligned on the resin matrix by dipole-dipole interaction.The products were characterized by field-emission scanning electron microscopy (FE-SEM) andTransmission electron microscopy (TEM). It is found that gold nanowires synthesized by this methodare of high purity. And the separation process is quite simple that only by ultrasound can we separategold nanowires with resin beads which also won’t damage the structure of gold nanowires.2. The synthesis of silver nanowires. An improved hydrothermal PVP-directed polyol processwas applied to synthesize silver nanowires. Sliver nanowires of different diameters and aspect ratioswere successfully obtained with PVP of different molecular weights in the autoclaves. Transmissionelectron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), X-rayDiffraction (XRD) and UV-Vis spectrum were used to characterize the microstructure and optical properties of silver nanowires. On the basis of the original experiment, the effects of experimentalreagents and parameters on the products were further studied by contrast experiments and plausiblegrowth mechanisms were analyzed.3. The synthesis of silver nanodecahedrons. Also in the autoclaves, the hydrothermal method wasused to synthesize silver nanodecahedrons. There were only two reagents (AgNO3and PVP-K17) inthe reaction system. AgNO3acted as precursor, while PVP-K17was reducing agent as well assurfactant. TEM, FE-SEM, XRD and UV-Vis spectrum were also used to characterize themicrostructure and optical properties of the products. The growth mechanisms of silvernanodecahedrons and nanowires are in common which are both grown from five-fold twinned seeds.Different reaction reagents and growth kinetics lead to different products.