Study On The Controllable Synthesis And Optical Property Of Silver Nanostructures

In recent years, noble metal nanomaterials have been an important research topic in the nano-science due to their unique electronic, optical, catalytic and potentials related to these properties.As it is known that the material structures determine their properties. With the improvement of synthesis methods and characterizations, it is found that many of the excellent properties are highly dependent on the morphology and size of the nanostructures, and controllable synthesis of noble metal nanostructures has achieved great progress. In this paper, silver nanostructures with high purity and excellent properties were synthesized through improved methods. The related research and results can be detailed as follows:1. Synthesis of silver nanorodsThe synthesis of Ag nanorods with high purity is very important and challenging in the fundamental research. In this work, Ag nanorods were synthesized by a seed-mediated growth method with silver ammonia solution(Ag(NH3)2OH) as the precursor. By changing the amount of seeds added,the silver nanorods with different aspect ratios can be produced. Due to the instability of silver nanostructures, influence of experimental operations on Ag nanorods was considered. Based on the changes of UV-Vis-NIR spectrum of silver nanorods, the instability caused in the process of centrifugation was simply discussed. Then, Ag nanorods have also been synthesized by a polyol process with the reference to the growth mechanism of Ag nanowires. Through adjusting the molecular weight of PVP, Ag nanorods of large aspect ratios were prepared.2. Synthesis of silver nanocubesUniform silver nanocubes with high purity is very important for the fundamental study of self-assembly and further research on the hollow nanostructures, gold nanocages for instance. In this work, Ag nanocubes of different sizes were synthesized by an improved polyol method. With addition of HCl solution, Ag nanocubes with size about 100 nm were obtained under an air atmosphere. And Ag nanocubes with size around 50 nm can be produced in a short time under Argon atmosphere with the presence of Na HS instead of HCl. Meanwhile, uniform Ag nanocubes with size larger than 100 nm were also synthesized successfully via adjusting experiment parameters. Results from transmission electron microscopy(TEM) combined with selected area electron diffraction(SAED)show that the Ag nanocubes are single crystalline with six(200) surface plane. In the UV-Vis-NIR optical absorption spectrum, the dipole moment resonance absorption peak is changed in the range of420--500 nm with the increase of Ag nanocubes size.3. Synthesis of silver nanoplatesSilver nanoplates were synthesized in the autoclaves through hydrothermal method. Using PVP as growth modifier, silver nanoplates were synthesized by reducing AgNO3 in the presence of N,N-dimethyl formamide(DMF). In the synthesis process, DMF was used as both solvent and reducing agent. Through adjusting different parameters, such as the reaction temperature and the mole ratio of PVP and AgNO3, various morphology and size of silver nanoplates were synthesized.