am301121k_si_001.pdf (1.75 MB)
Size-Dependent Two-Photon Excitation Photoluminescence Enhancement in Coupled Noble-Metal Nanoparticles
journal contribution
posted on 2012-09-26, 00:00 authored by Fei Han, Zhenping Guan, Teck Soon Tan, Qing-Hua XuPlasmon coupling is known to enhance the two-photon excitation
photoluminescence of metal nanoparticles significantly. Here, Au and
Ag nanospheres of different sizes were prepared to systematically
investigate the effects of particle size on plasmon coupling enhanced
two-photon excitation photoluminescence. An oppositely charged polyelectrolyte,
poly(diallyldimethylammonium chloride) (PDDA), was used to induce
the coupling of Au and Ag nanospheres. The two-photon excitation photoluminescence
enhancement factor was found to first increase and then decrease with
the increasing particle size for both Au and Ag nanospheres. Optimum
enhancement factors of 25-fold and 14-fold were obtained for coupled
55-nm Au nanospheres and 50-nm Ag nanospheres, respectively. The coupled
Au and Ag nanospheres displayed two-photon action cross sections of
up to 9 × 104 GM per particle (where 1 GM = 10–50 cm4 s/photon). Similar to Ag nanoparticles,
Au nanoparticles also displayed large coupling induced enhancement
of two-photon excitation photoluminescence. Considering their excellent
biocompatibility, high inertness, and easy preparation, Au nanoparticles
are expected to find many new applications in two-photon biosensing
and bioimaging.