金银纳米颗粒光学特性的理论研究

发布时间：2018-05-14 17:47

本文选题：纳米颗粒 + 去极化光谱　；参考：《中北大学》2015年硕士论文

【摘要】：纳米颗粒由于其微小的尺寸，决定了它异于块体材料的特殊性质。纳米材料已经在材料、医学、能源、工业、电子、环境等领域发挥了其巨大的作用，推动了产业化发展进程，方便和改善了人们的日常生活。目前，对纳米材料的制备、特性以及表面等离子体共振、表面增强拉曼散射、量子尺寸效应、宏观量子隧道效应、介电限域效应等物理特性的理论研究已经比较成熟。其中纳米粉体材料的生产已经初具规模，并且应用在了纳米制剂、纳米微电子等领域。但是，纳米颗粒的去极化效应是近几年才开始研究的特性，对此方面的研究还不是很完善。为了研究其去极化光谱，，了解它与等离子共振吸收光谱的联系和区别，本文建立了球形纳米颗粒的去极化场模型，详细推导了球形纳米颗粒的去极化场公式。由于去极化公式中与介电常数有很大关系，因此对与普通磁性介质不同的金属的介电常数以及核壳结构的复合纳米颗粒的介电常数进行了讨论。以球形金、银、金-银复合纳米颗粒以及核壳结构的金银复合纳米颗粒为研究对象，采用matlab软件编程模拟了它们在均匀散射场中的去极化行为，测量了其去极化光学吸收光谱。并且讨论了金属纳米颗粒半径、外部介质、光照强度以及颗粒的核壳比等因素对其光谱的影响。研究结果表明，纯金、纯银以及金银复合、金芯-银壳复合纳米颗粒去极化光谱都具有单峰的特征。在不同能量光照下，其介电常数是不同的，所以其去极化光谱也是变化的。但是金银复合纳米颗粒以及金芯-银壳复合纳米颗粒的峰值总是介于纯金和纯银纳米颗粒去极化峰值之间。去极化场的相对透射光强度会随着粒子尺寸的增加而红移，也会随着外部介质的改变，即介电常数的增加而红移，并且粒子尺寸越大、外部介质介电常数越大，相对透射光强度也越大。对于金属复合纳米颗粒，去极化峰还会随着复合材料中金银组分或者核壳比值的改变而发生近乎线性的红移或蓝移。究其原因，都是由于去极化场的存在改变了金属表面等离子体共振的情况。这说明可以通过控制入射光的能量、纳米颗粒半径、外部介质、金银的组分或者核壳比来可控的改变金属纳米颗粒的去极化光谱，以实现其在医学造影成像方面更有选择性的应用。
[Abstract]:Because of its small size, nanoparticles are different from the special properties of bulk materials. Nanomaterials have played an important role in the fields of materials, medicine, energy, industry, electronics, environment and so on. At present, the preparation, properties, surface plasmon resonance, surface-enhanced Raman scattering, quantum size effect, macroscopic quantum tunneling effect, dielectric limiting effect and other physical properties of nanocrystalline materials have been well studied. The production of nano-powder materials has begun to take shape, and has been applied in nano-preparation, nano-microelectronics and other fields. However, the depolarization effect of nanoparticles is only studied in recent years, and the research on this aspect is not perfect. In order to study the depolarization spectrum and understand the relation and difference between the depolarization spectrum and the plasmon resonance absorption spectrum, the depolarization field model of spherical nanoparticles is established, and the depolarization field formula of spherical nanoparticles is deduced in detail. Because the formula of depolarization is related to the dielectric constant, the dielectric constant of the metal and the composite nanoparticles with core-shell structure are discussed. The depolarization behavior of spherical gold, silver, gold-silver composite nanoparticles and core-shell structure gold-silver composite nanoparticles were simulated by matlab software, and their depolarization optical absorption spectra were measured. The effects of the radius of metal nanoparticles, the external medium, the illumination intensity and the core-shell ratio of the particles on their spectra were discussed. The results show that the depolarization spectra of pure gold, pure silver, gold-silver and gold core-silver shell composite nanoparticles have the characteristics of single peak. Under different energy illumination, the dielectric constant is different, so the depolarization spectrum is also changed. However, the peak values of gold and silver composite nanoparticles and gold core-silver shell composite nanoparticles are always between the depolarization peaks of pure gold and pure silver nanoparticles. The relative transmitted light intensity of the depolarization field will shift red with the increase of particle size and with the change of external medium, that is, the increase of dielectric constant, and the larger the particle size, the greater the dielectric constant of external medium. The greater the relative intensity of transmitted light is. For the metal composite nanoparticles, the depolarization peak also shows a nearly linear redshift or blue shift with the change of the composition of gold and silver or the core-shell ratio. The reason is that the depolarization field changes the metal surface plasmon resonance. This means that the depolarization spectrum of metal nanoparticles can be controlled by controlling the energy of incident light, the radius of nanoparticles, the external media, the composition of gold and silver, or the ratio of core to shell. In order to achieve a more selective application in medical imaging.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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