Optical properties of metal nanoparticles and nanoparticle aggregates important in biosensors

This article describes recent advances in electrodynamics theory that are b eing used to describe the extinction spectra of noble metal nanoparticles a nd of aggregates of nanoparticles. In one application we have extended the finite element discrete dipole approximation theory to the description of n onspherical metal particles, including the substrate on which they are sitt ing. In another application, we have developed a new dynamic effective medi um approximation for the description of aggregates of spherical gold nanopa rticles that are linked using DNA. (C) 2000 Elsevier Science B.V. All right s reserved.