Controllable Synthesis,Assembly And Optical Properties Study Of Silver Cubes

Surface-Enhanced Raman Spectroscopy(SERS)has received great attention in many field such as bioscience and environmental sciences since it was discovered in 1974 due to its extraordinarily high surface sensitivity and selectivity.SERS can also provide fingerprint information of many target molecules.The most common plsamonic nanomaterials used for preparing SERS substrates are Ag,Au,Cu.Because of the high quality factor,atomically flat facets,sharp corners,large contact area,and directional emittance,Ag cubes show great potential in plasmonic application,such as SERS and LSPR sensing and so on.Although there are increasing plasmonic applications of Ag nanocubes,it is still a challenge to controllably synthesizing Ag cubes with a wide sizes range,which restrain the application of silver nanocubes.At the same time,research about the optical property of Ag nanocubes is finite.To solve these problems,we developed the synthesis method of Ag cubes with large size range,and systematically studied its SERS property.The main work of this thesis are as follow:1.The synthesis methods of Ag cubes with different sizes were developed.The first method was to use Au cubes as the seeds and indirectly synthsize Au@Ag cubes with different sizes by water bath method.The second method was combined with polyol reduction method and the multi-step seed-mediated growth.the 50-1400 nm Ag cubes was successfully synthesized by controlling the growth step and the added volume of AgNO3.The prepared Ag cubes were uniform and monodispere,the operation is simple and the size of Ag cubes could be controlled accurately.To our knowledge,the size of the synthesized Ag cubes is much larger than that reported in the literature.2.The SERS properties of Ag cubes structures with different sizes and dimensions were systematically investigated for the first time.The optical properties and SERS properties of the Ag cubes zero-dimension and one-dimensional structures were studied by using SEM-SERS-dark field scattering technique.We measured the SERS spectra of Ag cubes 2D structures with different cubes sizes under 532,638,785 nm lasers.The experiment results show that the 80,110,130 nm Ag cubes SERS substrates have highest enhancement under three lasers,respectively.The relationship between the SERS intensity and the layer number of Ag cubes 3D structures was analyzed.We used the optimized SERS substrates to detect malachite green molecules,and the SERS substrate show good detection sensitivity and linear detection capability.3.We further synthesized the Ag@SiO2 core-shell structure and Ag@Pt satellite structure,and preliminarily investigated their optical properties and applications in enhanced fluorescence and photocatalysis.