Characteristics of gold nanorods and their applications to analytical sciences

Gold nanorods (AuNRs), which are rod-shaped gold nanoparticles, exhibit unique localized surface plasmon resonance (LSPR) on the basis of their anisotropic shape. Particularly, the longitudinal mode of LSPR, based on the oscillation of free electrons, appears in the near infra-red region, and generates much stronger electric fields as compared to spherical nanoparticles. In addition, it exhibits a larger peak shift, depending on the refractive indices of the surrounding medium, as compared with the case of spherical nanoparticles. Furthermore, the anisotropic shape leads to drastic changes in the optical properties of AuNRs, depending on their agglomeration (organization) conditions. Accordingly, AuNRs are expected to be promising in various fields, such as polarized filters, photoenergy conversion systems, sensors, and so on. In this paper, resent research results on AuNRs carried out in our group will be summarized from the viewpoints of analytical science.