Optical Properties Of Nonspherical Gold Nanoparticles And Measurement Of Its Size And Concentration

Gold nanoparticles exhibit excellent optical properties that bulk materials do not have. The localized surface plasmon resonance phenomenon of gold nanoparticles, which leads to the absorption and scattering of light by nanoparticles, will be strongly enhanced. These special optical properties of gold nanoparticles make them have tremendous applications in many fields, including biology, medicine, chemistry, information, energy, and environment. A deep knowledge and understanding for variation and regulation mechanism of optical properties of gold nonspherical nanoparticles has important guiding significance for the practical application of it. Size and concentration of gold nanoparticle determine the properties and behavior of gold nanoparticles in the practical applications. Spectral extinction method is a simple, fast, and low-cost method for measurement of particle size. It could be used in particle size and concentration measurement of nonspherical particles.The developments of preparation technology of gold nanorods in nonspherical metal nanoparticles, wide resonance harmonization wavelength range, great optical absorption, scattering cross section, and high photothermal conversion efficiency make it become the most widely application nonspherical nanoparticles in metal nanoparticles. This paper will select gold nanorods as a typical nonspherical metal nanoparticles. T matrix method as one of methods used to solve the nonspherical particles scattering problem has many advantages: high calculation speed, large size parameters of the calculation, high precision. And the program code of this method is open, easy to use and modify. We also added rod model in the T matrix method program code.In this paper, based on the T-matrix method of extended precision and the size correction model of dielectric function, we systematically studied the influence of width, length and volume of gold nanoellipsoid, nanocylinder and nanorods on the position and intensity of the resonance peak of extinction spectrum. We summarizes the variation of the resonance wavelength and intensity, which provides theoretical guidance for the applications of resonant optical properties of gold nanoparticles. For the application of gold nanorods in photothermal therapy and bioimaging, we investigated the dependence of the absorption and backscattering properties of gold nanorods on the diameter and length using the T-matrix method. We obtained the optimal gold nanorod structure in photothermal therapy, and the optimal gold nanorod structure in bioimaging, the optimal gold nanorod structure at the same time in photothermal therapy and bioimaging. Finally, the spectral extinction method is used for measuring the size distribution and concentration of polydisperse gold nonsherical nanoparticles. We measured extinction laboratories spectra of different sizes and concentrations of the gold nanorod sample and retrieved the diameter, length distribution and concentration of it. The resluts is identical with standard value relatively.