【作者】 邹志宇；

【导师】 陈相君；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2009， 博士

【摘要】 随着纳米科学的发展,纳米材料的制备和光电性质方面的研究变得越来越重要。贵金属纳米粒子复合玻璃(本论文中专指贵金属纳米粒子掺杂的硅酸盐玻璃)由于其中金属纳米粒子的表面等离子体共振效应使它具有超强的三阶非线性磁化系数和超快非线性响应性质,被广泛地用于光子学领域的各个方面,例如光学数据存储、光波导、全光转换开光等等。对于所有的这些应用,贵金属纳米粒子复合玻璃的光学性质强烈地依赖于体系中金属纳米粒子的尺寸、形状、密度和空间分布。在本论文中,我们成功制备了多种贵金属纳米粒子复合玻璃,利用后续的处理手段实现了对金属纳米粒子上述性质的有效控制。总结具体的细节工作如下所示:成功制备了多种贵金属(金和银)纳米粒子复合玻璃。使用了三种不同的材料制备方法成功制备了具有不同金属纳米粒子空间分布的复合玻璃。我们使用熔融-热处理法制备了金掺杂的硅酸盐玻璃,金纳米粒子分布在整个样品内部。使用离子溅射结合后续热处理方法,在载玻片表面制备了单分散的金纳米粒子,这些金纳米粒子部分嵌入在玻璃基体中。样品的吸收光谱反映出金纳米粒子特有的吸收峰。结合不同制备条件下样品的扫描电镜照片,讨论了这种单分散金纳米粒子的形成机理。利用银钠离子交换结合热处理的方法制备了银纳米粒子复合玻璃,样品中的银纳米粒子是分布在基体玻璃表面层。自行设计和制作了实验装置,实现了硅酸盐玻璃中金棒的电场辅助溶解。考虑实验过程中的多方面影响,自行设计和制作了电场辅助溶解的实验装置。并且利用这一装置实现了硅酸盐玻璃中金棒的电场辅助溶解。我们利用扫描电子显微镜观察了阳极边缘附近的样品区域的表面形貌,结果表明一些具有较大长径比的金棒溶解成准球形的纳米粒子,而另外一些仍然保持着一种椭圆形的结构。这一结果与样品在这个区域内的吸收光谱结果相符合。基于电场辅助溶解实验过程中电流-电压特性的测量,研究表明金粒子的溶解归因于电子的隧穿导电和金阳离子的导电。为金纳米粒子的电场辅助溶解提供了最为直接的证据,清晰地描述了金属纳米粒子的电场辅助溶解过程的物理情景。利用电场辅助溶解技术,对使用金靶溅射和后续热处理方法制备带有部分内含在玻璃内球形金纳米粒子的样品进行实验。从实验后样品表面的扫描电镜照片中可以发现,在直流电场辅助热处理下,原来球形的金纳米粒子部分溶解成类似于日蚀-月蚀的形状;有的粒子甚至被完全溶解,作为结果在样品表面上留下了纳米孔的结构。这些现象为金纳米粒子的电场辅助溶解提供了最为直接的证据。我们详细地讨论了整个实验过程中回路中电流随时间的演化规律。研究发现当实验中采用步进式增加电压形式的加压工艺时,在每一个电压增大的最初,回路中的电流都会出现一个非常锋利的增加过程;接下来在保持这个电压值不变的时间里,电流会经历一个缓慢衰减过程。初始时电流快速增加的现象表明了电子传输的开端,这种电子传输过程将导致金纳米粒子的极化和离子化。电流缓慢衰减过程其实是来自阴极提供的导电电子和离子化的带正电的金团簇进行中和的过程。我们特别指出,在整个回路电流中只有金阳离子传输的贡献才是导致金原子从纳米粒子上溶解到玻璃体系中的原因。成功制备了具有表面增强拉曼散射效应的基片。通过对溅射条件和热处理条件的控制,成功制备了具有一定表面增强拉曼散射活性的含有金纳米粒子的玻璃基片。结合样品表面的扫描电镜照片,考虑金纳米粒子特有的表面等离子体共振效应,讨论了此类基片表面拉曼散射增强效应的电磁场增强机理。研究了离子交换法制备的银纳米粒子复合玻璃的飞秒三阶非线性吸收性质。我们使用波长为800 nm、脉宽为120 fs的钛宝石飞秒激光脉冲,利用开孔的单光束Z扫描方法,测量了样品中银纳米粒子的三阶非线性吸收性质。从样品开孔的归一化透过率曲线的形状可以判定银纳米粒子的非线性吸收是反饱和吸收,这种反饱和吸收的产生可以由双光子吸收过程引起的带间跃迁来解释。更多还原

【Abstract】 With the development of nanoscience, preparation of nanomaterials and the research of photoelectric properties are becoming more and more important. Noble metals nanoparticles composite glass (noble metal nanoparticles doped silicate glass) have the large third-order nonlinear susceptibility and the ultrafast nonlinear response due to surface plasmon resonance of metal nanoparticles, therefore, it has been widely used in the field of photonics, such as optical data storage, optical waveguide , all optical switches and so on. For all of these applications, the optical properties of noble metal nanoparticles composite glass strongly depend on the size, shape, density and spatial distribution of the metal nanoparticles in the glass matrix. In this thesis, varied noble metal nanoparticles composites glass have prepared successfully, and the effective control on the above characteristics of metal nanoparticles using the subsequent treatment was realized. Specific details of the work as follows:Varied noble metal (gold and silver) nanoparticles composite glasses have been prepared successfully. Three different materials preparation methods have been used to prepare metal nanoparticles of composite glass with different spatial distribution. The gold-doped glass was prepared by using the melting-heat treatment method, and the gold nanoparticles were distributed in the whole sample. The monodisperse gold nanoparticles have been obtained in the slide surface with the aids of ion sputtering method and subsequent heat-treatment. These gold nanoparticles partially embedded in glass matrix. The absorption spectrum of samples reflected the specific absorption peak of gold nanoparticles. Combining the scattering electron microscope (SEM) images of samples prepared under different conditions, the formation mechanism of such monodisperse gold nanoparticles was discussed concretely. The silver nanoparticles composite glass was also obtained by using the methods of silver sodium ion-exchanged and subsequent heat-treatment, and we found the silver nanoparticles just distributed in the surface of glass.Experimental device was designed and produced, and the electric field assisted dissolution (EFAD) of gold rods in silicate glass was realized. Considering influences in the experiment, we designed and fabricated the experimental device of EFAD. And the EFAD of gold rods in silicate glass was realized by this device. The sample surface morphology near the edge of anode region was observed by SEM, and the results show that some gold rods with large aspect ratio dissolved into quasi-spherical nanoparticles, and the others remain elliptical structure. This result is consistent with the sample absorption spectra in this region. The dissolution of the gold particles is attributed to electrons tunneling and the gold cations conductivity basing on the measurement of current-voltage characteristics in EFAD experiment.The directest evidence was provided for the EFAD of gold nanoparticles, and the physical process of EFAD of metal nanoparticles was described clear. With the aids of EFAD technique, the EFAD experiment of samples with gold nanopartilces partially embedded glass, it have been prepared by the gold target sputtering and subsequent heat treatment. From SEM images of the samples after the experiments, it can be seen that some of the original spherical gold nanoparticles are dissolved to lunar-eclipselike structure and even fully dissolved, which left the nano-hole structure in the sample surface. These phenomena provided directest evidence for electric field assisted dissolution of gold nanoparticles.The loop current evolution with time was discussed in detail during the entire experiment. It was found that when the voltage used in the experiments is increasing step-by-step, in the initial of every increase voltage, loop current has a very sharp increase in the current process; then the current will experience a very long slow process of decay maintaining the same voltage value. The initial rapid increase in current suggests that this is the beginning of the electronic transmission, and such electronic transmission of the gold nanoparticles will lead to polarization and ionization. In fact, the long process of current decay is the process of the cathode conductivity of electrons and ions with positively charged gold clusters. In particular, it was pointed out that in the loop current, the contribution of gold cations transfer is the sole cause leading to those gold atoms dissolved into the glass from nanoparticles.The substrates for surface enhanced Raman scattering were prepared successfully. Through controlling the conditions of the sputtering and heat treatment, the silica substrates with a certain surface-enhanced Raman scattering active gold nanoparticles was prepared successfully. Combination of the SEM photographs of the sample surface and gold nanoparticles specific surface plasmon resonance effect, the electromagnetic field enhancement mechanism of such sample surface enhanced Raman scattering was discussed.The femtosecond third-order nonlinear absorption properties of silver nanoparticles composite glass by ion-exchanged method were studied. The femtosecond third-order nonlinear absorption properties of silver nanoparticles were measured by Z scan method with a single beam, with the use of the Ti-sapphire femtosecond laser system with wavelength of 800 nm and pulse width of 120 fs. For the silver nanoparticles, the reverse saturable absorption can be determined from the open aperture normalized transmittance curve shape, and the emergence of reverse saturable absorption can be explained by interband transitions of electron caused by two-photon absorption process.更多还原