Investigation of nanostructure scattering and absorption for combined optical diagnostic and therapeutic applications

Abstract

Medical applications of metal nanoparticles are the subject of intense research due to their unique properties which make them suitable for both diagnostic and therapeutic use. One such property is surface plasmon resonance which results in strong enhancement of the absorption and scattering of electromagnetic radiation. The combination of metal type, size, and shape characteristics provides unique tunability of a nanostructure's optical properties. Several types of nanoparticles have been explored for medical and biological applications. Here we present a theoretical investigation of novel metal nanostructures which have distinct absorption and scattering spectra. This could be beneficial for combined diagnostic and therapeutic applications since the diagnostic and therapeutic laser wavelengths can be decoupled for increased efficacy and safety. For this purpose, it is desirable to have the most intense scattering, with minimal absorption, in the near-infrared for imaging and the opposite in the red, for therapy. The efficiency factor for various metals, shapes and sizes was first calculated using the Discrete Dipole Approximation (DDA) method. From the results, nanostructures consisting of combinations of cubes and spheres were found to have the most appropriate scattering and absorption spectra and their optical properties were thoroughly investigated. The size, number and material (silver or gold) of the nanospheres and, to a lesser extent, the dimensions of the cubes were varied in order to obtain the optimum nanostructure with distinct absorption and scattering spectra. Given its properties, these nanostructures have the potential to be used for enhancement of various imaging and therapeutic methods.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.