Researchers at Argonne National Laboratory have succeeded in
tuning the luminescence from gold nanorods by adjusting their
lengths. By varying length from 300 nanometers down to 50 nm
while fixing the diameter at 30 nm, the team demonstrated
photoluminescence at 400- to 700-nm wavelengths. Further
enhancements could make it possible to use the optical emissions
from gold nanorods as a light source inside a silicon chip,
transducing light for optical network switches, routers and all-
optical computers. Other researchers had shown that surface
plasmons could influence luminescence emission spectra, but the
Argonne group wanted to verify that the spectra of
photoluminescent gold nanorods could be controlled by surface
plasmon resonances. When excited by two-photon-induced
photoluminescence, the nanorods exhibited two spectral
resonances, corresponding to their longitudinal and transverse
dimensions, demonstrating sensitivity to both excitation energy
and polarization. Surface plasmons are collective oscillations