Tuning the surface-plasmon resonance in nanoparticles for glazing applications

Issues affecting the performance of polymers doped with conducting nanoparticles for use with windows are examined in terms of impact on visible and solar transmittance, solar heat gain, and residual scattering. Emphasis is on visible transmittance fixed in the range of 30%-75%, combined with maximal blocking of the near-infrared (NIR) component of solar energy in the wavelength range of 750-1300 nm. Spectral data and surface-plasmon resonance (SPR) models of absorbance for LaB6 and indium tin oxide nanoparticles embedded in polymer are quite distinct from each other, but both can be used and each material has its advantages and disadvantages. The SPR of LaB6 nanoparticles is very efficient at NIR blocking, as it lies near 1000 nm, but as a result its tail overlaps the visible. In contrast the SPR of ITO lies well beyond 1000 nm and is thus far less efficient, only relying on its SPR tail. However, this means it only weakly affects the visible. Results of a quasistatic model for the optical properties are presented, along with comparisons to full Mie scattering calculations. It is found that ellipsoidal particles are required to explain the properties of the studied LaB6 particles, and that scattering can be significant in the NIR while weak in the visible. Furthermore, the forward-to-backward-scattering ratio is different for Rayleigh scattering in the visible and scattering near the SPR. The latter is much more isotropic, even for larger particles. (c) 2005 American Institute of Physics.