Nanosecond switchable localized surface plasmons through resettable contact angle behavior in silver nanoparticles.

In this article, we show nanosecond switchable localized surface plasmon resonance (LSPR) dipole and quadrupole modes from silver (Ag) nanoparticles on fused quartz substrates. Near-spherical Ag nanoparticles (contact angle of 166 ^° ± 9 ) were synthesized by Ultra Violet (UV) laser dewetting of Ag thin films under a glycerol fluid environment. Under a single 9 nanosecond laser pulse irradiation of the particles in air, the particles were changed into a near-hemispherical shape (with contact angle of 103 ^° ± 7 ). The resulting changes in particle contact area and volume fraction in the dielectric media resulted in substantial shift in the wavelength and intensity of the dipolar and quadrupolar LSPR modes to the violet side of visible spectrum. This switching of the plasmon resonance wavelength position could be repeated over multiple cycles by resetting the contact angle by laser re-irradiation under glycerol. This reusable nanoparticle system with reversible plasmonic properties within nanosecond time scales could prove a cost-effective way of designing high speed plasmonic devices in desired wavelength regions.