Controlled Synthesis Of Low-dimensional Noble Nanomaterials And Their Applications

Nanomaterials show special physicochemical properties and draw great attention due to their remarkable small size effect,surface effects,the effect of quantum size and the tunnel effect of macroscopic quantum.Metal nanomaterials especially noble metal nanomaterials have played important roles in many areas such as catalysis,medication,electrical,energy and optical applications.They have been regarded as crucial materials in economy,national defense and the development of society.As a result of the close relationship between structures and performances,size and shape controlled synthesis of noble nanomaterials has been one of the greatest challenges.This thesis is intended to the simple and efficient synthesis of low-dimensional noble nanomaterials.At the same time design and system study the nanomaterials from the structure and surface property.The main work in this thesis is as follows:(1)A series of carbon protected Pt/TiO2 nanostructures were synthesized through an ultraviolet irradiation route.Firstly,a lytropic liquid crystals system containing H2PtC16 precursor was fabricated from nonionic/anionic mixed surfactants.By the reducing property excited by UV light irradiation,Pt nanoparticles with small size and narrow diameter distribution were obtained without additional reducing agent.The carbon layer of Pt/TiO2 nanostructures were adjusted by varying the calcination condition(Ar,Air,and O2).Surface and interface properties were investigated by TEM,HRTEM,Raman spectra,XPS,etc.Further applications were tested by visible light degradation of RhB,hydrogenation of nitrobenzene reaction and CO oxidation.The influences of carbon layers were discussed during these catalytic reactions.(2)Au nanosheets(Au NSs)were prepared in lamellar liquid crystals through a novel photochemical route.Firstly,the liquid crystals system(LCs)contained both chloroauric acid and lytropic liquid crystals of nonionic/anionic mixed surfactants as templates.Due to the reduction ability of H-/OH-radicals,which was excited by sunlight,chloroauric acid precursor within water layers was reduced into Auo nanoseeds and gradually grew into small single-crystalline Au NSs of high quality.The strength of light irradiation was one of the key factors for the highly efficient growth of Au NSs,and the natural sunlight was found as an optimum and green light source for the production of Au NSs.Slow and mild reduction process was one of the most important conditions.Besides,it was confirmed that both irradiation time and concentration of chloroauric acid were the controlling factors for inducing anisotropic growth of Au NSs.Representative Au NSs have approximate thicknesses of 8 nm,50 nm,and 100 nm.It is found that?50 nm thick Au NSs present much stronger surface-enhanced Raman scattering(SERS)effect than that of Au NSs with thickness of?8 nm and 100 nm.(3)Ultrathin gold nanowires with surface-clean surface have been prepared in the absence of organic reagent.Au3+ ions were reduced into small Au nanoseeds by Cu sheets during pretreatment.Best condition for growth was proposed after the investigation of dropping seed solution.The morphology evolution from Au nanoparticles to Au nanowires provides new understanding on the growth mechanism.Furthermore,TEM and HRTEM analysis showed excellent SERS ability of Cu grid supported Au NWs than that of blank Cu grid.Ultrathin Au NWs supported on Cu grid was a natural,simple,and effective SERS substrate.