Optical Limiting Materials Based on Gold Nanoparticles
Final rept. 1 Mar 2009-22 Apr 2014
ILLINOIS UNIV AT URBANA DEPT OF CHEMISTRY
Pagination or Media Count:
Two-photon absorption TPA is a phenomenon of great interest for various optical limiting applications. The enhancement of molecular TPA cross-sections by placement of TPA chromophores within the plasmonic field of resonant and nonresonant plasmonic gold nanoparticles was explored. Polyelectrolyte layer-by-layer wrapping was employed to provide spacer layers between the chromophores and the gold surface. For on-resonant cases, TPA cross-sections could be enhanced by a factor of 40 for chromophores closest to the gold surface. The distance dependence of the TPA cross-section enhancement followed the calculated electric field. In contrast, for off-resonant gold nanoparticles, the calculated electric field dependence decreased then increased as a function of distance from the gold surface, in accord with experiment. Finally, TPA chromophores were covalently attached to the wrapping layers to put the chromophores even closer to the gold surface but the observed distance dependence was flat, suggesting that chromophore orientation may have been compromised by covalent attachment.