Mendoza Herrera Luis J, Bruvera Ignacio J, Scaffardi Lucía B, Schinca Daniel C
Centro de Investigaciones Ópticas (CIOp) (CONICET-CIC-UNLP) Cno, Parque Centenario e/505 y 508 Gonnet, C.C. 3 (1897) Gonnet, Buenos Aires, Argentina.
Phys Chem Chem Phys. 2017 Jan 25;19(4):3076-3083. doi: 10.1039/c6cp08260b.
Optical extinction is a handy and ubiquitous technique that allows us to study colloidal nanoparticles in their native state. The typical analysis of the extinction spectrum can be extended in order to obtain structural information of the sample such as the size distribution of the cores and the thickness of the coating layers. In this work the extinction spectra of FeO, FeO@Au, and FeO@SiO@Au single and multilayer nanoparticles are obtained by solving full Mie theory with a frequency dependent susceptibility derived from the Gilbert equation and considering the effect of Eddy currents. The results are compared with non-magnetic Mie theory, magnetic dipolar approximation and magnetic Mie theory without Eddy currents. The particle size-wavelength ranges of validity of these different approaches are explored and novel results are obtained for Eddy current effects in optical extinction. These results are used to obtain particle size and shell thickness information from the experimental extinction spectra of FeO and FeO@Au nanoparticles in good agreement with TEM results, and to predict the plasmon peak parameters for FeO@SiO@Au three layer nanoparticles.
光消光是一种方便且普遍存在的技术，它使我们能够研究处于自然状态的胶体纳米颗粒。为了获得样品的结构信息，如核的尺寸分布和涂层的厚度，可以对消光光谱进行典型分析。在这项工作中，通过求解全米氏理论，利用从吉尔伯特方程导出的频率相关磁化率，并考虑涡电流的影响，获得了FeO、FeO@Au和FeO@SiO@Au单层和多层纳米颗粒的消光光谱。将结果与非磁性米氏理论、磁偶极近似和无涡电流的磁性米氏理论进行了比较。探索了这些不同方法的粒径-波长有效范围，并获得了光消光中涡电流效应的新结果。这些结果用于从FeO和FeO@Au纳米颗粒的实验消光光谱中获取粒径和壳层厚度信息，与透射电子显微镜（TEM）结果吻合良好，并用于预测FeO@SiO@Au三层纳米颗粒的等离子体峰参数。
