Optimization Study Of The Electromagnetic Field Distribution And Structure Of The Metal Nanoparticles

Due to its unique electromagnetic nature, nano-scale metal particles have broad application prospects in the fields of optics, biotechnology and so on. With the development of theoretical research and characterizations technique, the compositions of nanostructure have varied from the initial single noble metal to a composite structure, which consists of a variety of materials. And the shapes of nanostructure have developed from single spherical structure to single irregular structure, the present line clusters, surface clusters and other structures. Gold nanoshell, consisting of a dielectric core coated with a thin gold shell, is a typical composite structure. Its attractive optical property derives from the gold surface plasmon resonance. It has been discovered that the resonance frequency is mainly modulated by the core-shell radius ratio of a particle. Beside, the external environment, particle shape and size have influences on the resonance peak.The physical mechanism of extinction property is discussed simply, and the computational tools and related theoretical knowledge are introduced in this paper.By analyzing shell thickness, core radius, overall size and light wave polarization, the movement law of absorption peak are attained in order to study the best absorption condition. And the results can offer a reference for the practical application. Analysis shows that the polarization mode has little influence on absorption efficiency. While different polarization modes can change the electromagnetic loss distribution, thereby adjust the electromagnetic distribution of nanoshell.The scattered field of nanoshells is also analyzed in this thesis. Both amplitude and phase of space scattered field at 820nm and 1024nm wavelengths are attained, which are widely used in the field of medicine. And the results may offer a reference for scattering imaging.The electromagnetic loss distributions of the single nanoshell and nanoshell groups are calculated. The results show that electromagnetic loss of a single nanoshell shows symmetrical distribution. The electromagnetic loss distribution of 2-dimension groups also shows symmetrical distribution, while its individual particle shows unique loss distribution. So the new composite structure with photo-thermal polarity is proposed, which is composed of two nanoparticles, one is gold nanoshell and the other is ideal medium nanoparticle.Finally, the movement of the composite structure in liquid is discussed simply. The results show that the composite structure has self-rotation ability under certain condition.