Study Of Controllable Preparation And Application Of Low Dimension Ag Nanostructures

As fossil energy is increasingly being exhausted, how to solve the problems of energy shortage have become a hot spot of social concern. Further development and application of low carbon, green, environmental protection and new low cost materials are the important measures to solve the energy crisis and environment problems. Silver nanomaterials are one of the important metal nanomaterials, because of thier excellent optical, electrical, magnetic, thermal properties, which have exhibited great potential application in the field of catalysis, electronic and photovoltaic power generation. However, there are still many problems in the preparation and modification of lower dimension silver nanosructures, which largely limit the development and extensive application of silver nano-materials. In view of these points, in this dissertation, different methods were studied to synthesize various morphologies of lower dimension silver nanostructures. Based on some of these silver nanostructures, on one hand, the modification of silver nanowires by magnetron sputtering method and ultrasonic vibrating were studied; on the other hand, the mechanisms of silicon surface etching morphology by silver nanoparticles and silver nanowires were revealed. In addition, the synthetic processes and photocatalytic properties of Ag-Ag2S and Ag2S-NiO nanocomposites are discussed in detail. The main research works are as follows:Different silver nanostructures were synthesized by hydrothermal, seed mediated growth, and magnetron sputtering methods. Silver nanocubes, nanopolyhedrons and nanowires were synthesized with hydrothermal method by adjusting the amout of PVP or Na2S. A special structure of silver nanospheres packed with coacervate of silver nanoparticles was systhsized by slliver seed growth method. The reaction time directly affected the size and uniformity of silver nanospheres. The relations between sputtering current and morphology of silver nanoparticles were studied. Hemispherical, elliptic balls and large irregular shaped silver nanoparticles were formed on the surface of silicon under different sputtering currents.Silver nanowires with large draw ratio were synthesized by hydrothermal method. The modification of silver nanowires by magnetron sputtering method and ultrasonic vibrating and the process of ordering silver nanowire arrays by spontaneous spreading were expounded. The forming process of spinulose prominence of silver nanowires surface by using magnetron sputtering method was explored. The results indicated that sputtering time was important to the qualifiable degree of silver nanowires. The SERS performance of modified silver nanowires was analyzed. The cavatition and friction in the solution made silver nanowires to bend and break off in liquid environment under ultrasonic vibrating. The atomic arrangement and fracture characteristic of the bended silver nanowires with different diameters were studied. The absorption property of silver nanowires was enhanced after ultrasonic vibrating. The large alignment of Ag nanowires was realized by spontaneous spreading of volatile solution droplet onto solid substrate. The spreading microfluid in the suspension and the subsequent adhering on the solid surface were the important factors for alignment of Ag nanowires. A simple device was designed to transfer and align the radial shaped oriented Ag nanowires onto a target substrate into one direction.Silver nanoparticles and Silver nanowires assisted silicon etching processes were studied respectively. Special crateriform structures with gradually varying radius were achieved by the surface electromagnetic field enhancement effect of LSPR. According to the Maxwel and electrochemistry analysis theories, the formation kinetics of the crateriform structures conformed to the local electromagnetic field enhancement and forward scattering induced by LSPR. The relations between the size of crateriform structures and scattering cross section of silver nanoparticles were expounded. Assisted by Ag nanowires, the influence of the interface contact between Ag nanowires and silicon on the etching results was investigated. Around the Ag nanowires, with the etching process proceeding, the etching morphology of silicon surface exhibited smooth etching and porous etching. The effect mechanisms of the gradual changes in the contact between Ag nanowires and silicon surface on etching morphologies were studied based on electrochemical theories.The synthesis and photocatalytic properties of Ag-Ag2S and Ag2S-NiO nanocomposites were studied in detail. The formation process and mechanism of polyhedron Ag-Ag2S nanostructure were exposed. The synthesis method and structural features of Ag2S-NiO nanostructure were discussed. The visible light catalytic properties of Ag-Ag2S and Ag2S-NiO nanostructures were studied and two structures showed good preformance.