DNA-modified gold nanoparticle composites are materials consisting of
many small gold particles (with diameters typically of order 20-40 nm)
linked together by DNA strands. The optical properties of such
composites depend dramatically on temperature [1,2]. At high
temperatures, there is a strong extinction peak around 500 nm which is
attributed to the surface plasmon resonances of individual gold
nanoparticles, but as the temperature is lowered, this peak shifts
towards longer wavelengths and broadens substantially. In this talk,
we will describe a theory for this temperature-dependent change. The
theory consists of two parts: (i) a model for the
temperature-dependence of the composite structure, which is
responsible for the change in the optical properties and (ii) a model
calculation for the extinction coefficient of the composite, based on
an application of the discrete dipole approximation [3] to the
temperature-dependent structure.
References
[1] C.-H. Kiang and R. Ramos, LANL
preprint physics/0111002 (2001)
[2] A. A. Lazarides and G. C. Schatz,
J. Phys. Chem. 104, 460 (2000).
[3] E. M. Purcell and
C. R. Pennypacker, Ap. J. 186, 705 (1973).