Plasmonic Ga nanoparticles (NPs) were thermally oxidized at low temperature in order to increase the native Ga2O3 shell thickness and to improve their stability during the chemical functionalization. The optical, structural and chemical properties of the oxidized NPs have been studied by spectroscopic ellipsometry, scanning electron microscopy, grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy. A clear redshift of the peak wavelength is observed with the increasing annealing time due to the Ga2O3 thickness increase, and barely affecting the intensity of the plasmon resonance. This oxide layer enhances the stability of the NPs upon immersion in ethanol or water. The surface sensitivity properties of the as-grown and oxidized NPs were investigated by linking a thiol group from 6-Mercapto-1-hexanol through immersion. Ellipsometric spectra at the reversal polarization handedness (RPH) condition are in agreement with the Langmuir absorption model, indicating the formation of a thiol monolayer on the NPs.
S. Catalán-Gómez, M. Briones, A. Redondo-Cubero, F. J. Palomares, F. Nucciarelli, E. Lorenzo, and J. L. Pau, "The role of the oxide shell in the chemical functionalization of plasmonic gallium nanoparticles," Proc. SPIE 10231, Optical Sensors 2017, 102310D (Presented at SPIE Optics + Optoelectronics: April 24, 2017; Published: 16 May 2017); https://doi.org/10.1117/12.2265665.
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