Study On The Controllable Synthesis And Optical Properties Of Au Nanoparticles

The gold nanoparticles exhibit strong surface plasmon resonance?LSPR?,and their absorption peaks are related to the geometry,core-shell structure,size and surrounding media of nanoparticles.Although LSPR can detect the analyte molecules adsorbed on the surface of gold nanoparticles,the overall characteristics of the adsorbed molecular structure are not be recognized by the extinction spectrum,but the vibration spectrum can compensate for this shortcoming.Surface-enhanced Raman spectroscopy?SERS?can show the characteristic vibrational map of the molecule without damaging the structure of the analyte.The quantitative and qualitative information of the analyte can be obtained by combining LSPR and SERS.The non-spherical gold nanoparticles are widely concerned by changing the size and shape of the nanocomposites to achieve visible and infrared tunable continuous tuning,matching with different excitation wavelength detection targets.In this paper,we designed and synthesized the gold nanoparticles with different structures,and explored the application of gold nanoparticles in molecular detection.In addition,the Au@Cu₂O heterojunction composite structures are prepared and used in photocatalytic degradation applications study.The main contents are as follows:1.Regulation of gold nanoparticles and the application in SERS?1?A series of gold nanorod structures with different aspect ratios were prepared by aqueous phase synthesis.The aspect ratio of gold nanorods was mainly adjusted by the content of silver nitrate and seed solution,and its corresponding LSPR peak of the Au nanorods could be regulated precisely by adjusting the aspect ratio.The correlation between LSPR and SERS was analyzed by using the gold nanorods with different LSPRs.The experimental and theoretical results showed that the gold nanorods are used for the determination of Raman molecules with high sensitivity.The enhancement effect can reach 10-7 mol / L when the LSPR and Raman excitation wavelength matched.?2?The systematic evolutions of gold nanoparticles from rod-like to truncated octahedrons to octahedrons were effectively realized by using gold nanorods as seed solutions.This lateral growth mode provided an alternative way for gold nanorods to adjust the extinction cross section and the longitudinal plasma wavelength,which will facilitate its application as a new material in biotechnology,optoelectronics and optics.?3?The gold nanobipyramidsand and Au@Ag nanorods were synthesized and the corresponding enhancement effects in SERS were investigated.Experimental and theoretical results showed that the gold nanobipyramids have a pentagonal base and two sharp vertices that produce new extra "hot spots".Therefore,the gold nanobipyramids are more sensitive to the surrounding refractive index and can obtain stronger local electric field enhancement effectcompared with the gold nanorods.Moreover,this material can be applied to biological in vivo,the detection of cancer cells in the future has a huge potential.2.Preparation of Au@Cu₂O heterojunction structure and the application inphotocatalytic degradationThe growth mechanism of the Cu₂ O cube and the necessity of surfactant were discussed.The influences of Cu₂ O shell on the absorption spectrum were also discussed.Finally,Cu₂ O cube structure and Au@Cu₂O composite structure were used to degrade rhodamine B.The results showed that the photo-degradation ability of Au@Cu₂O heterojunction structure is stronger than the Cu₂ O cube structure.In this paper,we studied the properties of surface Plasmon excitation metal nanostructures and explored the relationship between the induced local electric field enhancement effect and the microstructures,and modulated the surface Plasmon resonance through design the geometric parameters of the nanostructure,realizing the accurate control technique of Au nanostructures particles with high-efficiency SERS for the desired requirement,It provides the theoretical and experimental basis for the further development of gold nanoparticles.