Localised detection of thiophenol with gold nanotriangles highly structured as honeycombs by nonlinear sum frequency generation spectroscopy

Abstract

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 thiophenol 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.

Semiconductor quantum dots reveal dipolar coupling from exciton to ligand vibration

“…Vibrational SFG spectra were acquired thanks to a home-made setup described in ref. 70 . A pulsed IR laser source (Nd:YVO 4 , 1064 nm, 7.5 ps, HighQ laser) is coupled to an acousto-optic modulator (62.5 MHz micropulse repetition rate, 2 μs train, 25 Hz macropulse repetition rate) and is used, after amplification, to pump two optical parametric oscillators (OPO): i, an IR OPO tunable in the 2500-4000 cm −1 spectral range and, ii, a visible OPO tunable between 440 and 710 nm.…”

Sum-Frequency Generation Spectroscopy of Plasmonic Nanomaterials: A Review

“…( b ) SFG spectrum of the sample of ( a ) in ssp-polarization, revealing the two C–H (phenyl ring) of the thiophenol. Figure panel is adapted from reference [78].…”

Latest Novelties on Plasmonic and Non-Plasmonic Nanomaterials for SERS Sensing

“…The key point in order to obtain zones of strong electric field (called hotspots) is a precise control of the shape, size, and spatial organization of plasmonic nanostructures. The control of these parameters is enabled and realized thanks to a great number of lithographies such electron beam lithography [ 24 , 25 , 26 , 27 ], optical lithographies [ 28 , 29 , 30 ], nanosphere lithography [ 31 , 32 , 33 ], and nanoimprint lithography [ 34 , 35 , 36 ]. Several groups examined a broad number of designs as plasmonic nanodisks, nanodimers, and nanorods, which have reached important EF values (EF = 10 6 –10 9 ) [ 37 , 38 , 39 ].…”