Pulsed infrared laser annealing of gold nanoparticles embedded in a silica matrix

Pulsed infrared laser irradiation was used to modify the optical and physical properties of gold nanoparticles in a SiO2 substrate. The primary laser wavelength used for annealing was 8 μm, where the primary absorption was in the substrate. The optical absorption spectra exhibit a typical surface plasmon peak at 520 nm, which increases with laser fluence. This implies growth of the gold nanoparticles during laser annealing but the size distribution remains narrow, unlike some thermal annealing procedures that produce bimodal size distributions. The results were confirmed by scanning transmission electron microscopy and were consistent with the calculations of expected extinction spectra.