金纳米阵列的表面等离激元氢气监测研究

发布时间：2018-09-09 12:21

【摘要】：人类对氢气的研究已经有很长的历史了,进入21世纪以后,能源短缺是人类社会面临的重大问题,对氢气的研究也越来越受到人们的重视。目前对氢气的研究的最大的挑战主要是在生产,分配,储存和利用氢气的过程中尽可能地优化成本,增加稳定性和安全性。因此,氢气监测在很多潜在的领域有非常重大的用途。氢气监测器已经被研究了一个世纪。传统的方法主要有气象色谱法,质谱分析法,热导率监测器和激光气体分析。也有一些商业用监测器,这些监测器一般是以固态的方法来进行氢气监测。相对于传统的电学监测器,光学监测器有许多优点。其中最大的优点是光学监测器在工作的时候没有产生火花的风险,这是非常大优点,因为若在操作的时候在氢气的气氛中产生火花将是非常致命的。另外光学监测器也具有避免电磁场干扰的优点,可以在恶劣环境中远程显示等优点。本文我们就是利用金属结构中形成的的局域表面等离子共振来研究光学监测器。由于金属中含有大量的自由电子,当用一束光来照射金属纳米颗粒,由于金属纳米颗粒的尺寸相对于波长足够小,导体中的自由电子就会与晶格中固有阳离子发生共振,产生局域表面等离子共振。由于在发生共振的时候纳米颗粒表面的电荷分离,就会在纳米颗粒附近产生很强的叠加电场。经研究发现有很多因素影响局域表面等离子共振(Localized surface plasmon resonance,LSPR)的共振波长,例如纳米颗粒的尺寸,形状,材料外界环境的介电性能。所以,通过寻求LSPR的共振波长,就可以监测到纳米颗粒的任何变化或者纳米颗粒周围的的介电性能变化。这两种监测分别被叫做直接局域表面等离子共振监测和间接局域表面等离子共振监测。本文我们主要研究了不同形状的金属纳米结构的局域表面等离子共振特性。首先我们主要研究了金月牙纳米结构阵列的局域表面等离子共振的特性。实验部分我们用电子束刻蚀的方法制作了不同尺寸的金月牙纳米结构阵列,然后获得了其吸收谱线。从获得的吸收谱线中我们发现了不同尺寸的金月牙纳米结构阵列它们发生表面等离子共振的位置不同。接下来我们通过软件FDTD Solutions 8.6获得了金月牙纳米结构阵列在共振时的电磁场、表面电荷分布等表面等离激元特性,发现了金月牙纳米结构的电荷大都分布在月牙尖端,而且电磁场增强也发生在月牙的尖端。后来我们通过对金月牙纳米结构的吸收—能级图的研究,用等离子体杂化理论完美的解释了金月牙纳米结构的局域表面等离子共振特性。随后我们研究了一系列不同尺寸的金月牙纳米结构,发现随着月牙腰宽的增加,它们的共振峰会发生蓝移,这为制造金月牙纳米结构监测器具有指导意义。最后我们引进了一个介质圆盘,通过对金月牙纳米结构不同位置与介质盘的耦合的研究,我们发现金月牙尖端与介质盘作用时,金月牙纳米结构对光的吸收要更加明显,因为此时的吸收谱线的共振峰移动要更加明显(与没有介质圆盘时相比较),这说明金月牙纳米结构的月牙尖端是最理想的监测位置。我们还通过单介质盘(一个介质盘放置在任一月牙尖端)和双介质盘(两个介质盘分别放置在两个月牙尖端)的比较,发现双介质盘时金月牙纳米结构有更明显的共振峰位移动,这说明对于金月牙纳米结构可以两点激发、监测,而且有更好的监测效果,这为制造多触点激发、监测提供了理论指导。然后,我们研究了金三角形纳米结构阵列的局域表面等离子共振的特性。和金月牙结构相似,我们首先得到了金三角形纳米结构阵列的吸收谱线,然后根据吸收谱线我们获得了金三角形纳米结构在共振峰位置处的电场分布和表面电荷分布。通过对金三角形纳米结构的电场和表面电荷分布的研究,我们发现金三角形的电场增强和电荷分布主要聚集在金三角形沿入射光方向的顶点处。所以对于金三角形结构,它的顶点处是理想的监测位置。在最后的工作中,我们首先用相同的方法研究了矩形纳米结构,在得到矩形纳米结构阵列的吸收谱线的前提下,我们获得了金矩形纳米结构在共振峰位置处的电场分布和表面电荷分布。然后我们系统的比较了金月牙纳米结构、三角形和矩形纳米结构在共振峰位置处的电场分布、表面电荷分布和吸收谱线。分析了结果以后,我们发现矩形结构的局域表面等离子共振特性没有月牙结构和三角形结构好;而且从吸收谱线来看,三角形和金月牙纳米结构有更小的半高宽。所以相对于矩形结构,三角形和金月牙纳米结构是理想的监测器结构。但是相对于三角型纳米结构,金月牙纳米结构监测器有更加好的电场增强和更密集的表面电荷分布,更重要的一点是金月牙纳米结构可以两端激发,而且两端激发的时候,金月牙纳米结构的吸收谱线有更明显的共振峰位移动,这为制造多触点激发、监测提供了理论指导。
[Abstract]:The study of hydrogen has a long history. Since the beginning of the 21st century, energy shortage has become a major problem facing the human society. More and more attention has been paid to the study of hydrogen. Hydrogen monitors have been studied for a century. Traditional methods include meteorological chromatography, mass spectrometry, thermal conductivity monitors and laser gas analysis. There are also some commercial monitors, which are generally based on Optical monitors have many advantages over conventional electrical monitors. One of the biggest advantages of optical monitors is that they do not run the risk of sparks. This is a great advantage because it can be very lethal to produce sparks in the hydrogen atmosphere during operation. Optical monitors also have the advantages of avoiding electromagnetic interference and can be displayed remotely in harsh environments. In this paper, we use the local surface plasmon resonance formed in metal structures to study optical monitors. When the size of the nanoparticles is small enough relative to the wavelength, the free electrons in the conductor will resonate with the intrinsic cations in the lattice, resulting in local surface plasmon resonance. Elements affect the resonance wavelengths of local surface plasmon resonance (LSPR), such as the size, shape of nanoparticles, and dielectric properties of materials in the external environment. Two kinds of monitoring are called direct local surface plasmon resonance monitoring and indirect local surface plasmon resonance monitoring. In this paper, we mainly study the local surface plasmon resonance characteristics of metal nanostructures with different shapes. In the experimental part, we fabricated the gold crescent nanostructured arrays with different sizes by electron beam etching, and then obtained their absorption spectra. From the absorption spectra we found that the different sizes of gold crescent nanostructured arrays have different surface plasmon resonance locations. Ions 8.6 obtained the electromagnetic field and surface charge distribution of the gold crescent nanostructured arrays in resonance. It was found that the charge of the gold crescent nanostructured arrays was mostly distributed at the tip of the crescent, and the enhancement of the electromagnetic field occurred at the tip of the crescent. Later, we used the absorption-level diagram of the gold crescent nanostructured arrays. Then we studied a series of gold crescent nanostructures with different sizes and found that their resonance peaks blue shift with the increase of the waist width of the crescent, which provides guidance for the fabrication of gold crescent nanostructure monitor. Meaning. Finally, we introduce a dielectric disk. Through the study of the coupling between the different positions of the gold crescent nanostructure and the dielectric disk, we find that when the gold crescent tip interacts with the dielectric disk, the light absorption of the gold crescent nanostructure is more obvious, because the resonance peak shift of the absorption spectrum is more obvious (and there is no medium). We also found that the crescent nanostructures of gold crescent have more obvious commonalities when compared with single dielectric disc (one dielectric disc is placed at the tip of any crescent) and double dielectric disc (two dielectric discs are placed at the tip of two crescents). The peak displacement shows that the gold crescent nanostructures can be excited and monitored by two points and have better monitoring effect, which provides theoretical guidance for the fabrication of multi-contact excitation and monitoring. According to the absorption spectra of the gold triangle nanostructure arrays, the electric field distribution and the surface charge distribution of the gold triangle nanostructure at the resonance peak are obtained. In the final work, we first studied the rectangular nanostructures with the same method. On the premise of obtaining the absorption spectra of the rectangular nanostructures array, we obtained the gold rectangle. Then we systematically compare the electric field distribution, surface charge distribution and absorption spectra of crescent nanostructures, triangular nanostructures and rectangular nanostructures at the resonance peaks. Compared with the rectangular structure, the triangular and the crescent nanostructures are the ideal monitors. But compared with the triangular nanostructures, the crescent nanostructure monitors are better. More importantly, the absorption spectra of gold crescent nanostructures can be excited at both ends, and when excited at both ends, the absorption spectra of gold crescent nanostructures have more obvious formant shifts, which provides theoretical guidance for manufacturing multi-contact excitation and monitoring.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O614.123

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