Localised detection of thiophenol with gold nanotriangles highly structured as honeycombs by nonlinear sum frequency generation spectroscopy
Résumé
Gold nanotriangles structured as honeycombs and fabricated by nanosphere lithography on a gold film are functionalized by thiophenol molecules in order to be used as plasmonic sensors in nonlinear optical sum-frequency generation (SFG) spectroscopy. The monitoring and the characterization of the surface optical properties are performed by UV-Visible differential reflectance spectroscopy showing an absorbance maximum located at 540 nm for p-and s-polarisation beams. SFG spectroscopy proves to be effective for thiophenol detection in ssp-polarisation scheme while the molecular SFG signal disappears in ppp-configuration due to the strong s-d interband contribution of gold. However, in ssp-configuration, the vibration modes of thiophe-nol molecules at 3050 and 3071 cm −1 are yet observed thanks to the excitation of a transversal plasmon mode by the incident visible laser beam, whereas they are usually very difficult to distinguish by Surface Enhanced Raman Scattering (SERS) and other vibrational optical probes.
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