Plasmonic Gold Nanohole Arrays for Surface-Enhanced Sum Frequency Generation Detection

Abstract

Nobel metal nanohole arrays have been used extensively in chemical and biological systems because of their fascinating optical properties. Gold nanohole arrays (Au NHAs) were prepared as surface plasmon polariton (SPP) generators for the surface-enhanced sum-frequency generation (SFG) detection of 4-Mercaptobenzonitrile (4-MBN). The angle-resolved reflectance spectra revealed that the Au NHAs have three angle-dependent SPP modes and two non-dispersive localized surface plasmon resonance (LSPR) modes under different structural orientation angles (sample surface orientation). An enhancement factor of ~30 was achieved when the SPP and LSPR modes of the Au NHAs were tuned to match the incident visible (VIS) and output SFG, respectively. This multi-mode matching strategy provided flexible controls and selective spectral windows for surface-enhanced measurements, and was especially useful in nonlinear spectroscopy where more than one light beam was involved. The structural orientation- and power-dependent performance demonstrated the potential of plasmonic NHAs in SFG and other nonlinear sensing applications, and provided a promising surface molecular analysis development platform.

Evidence for a Local Field Effect in Surface Plasmon-Enhanced Sum Frequency Generation Vibrational Spectra

“…For example, Humbert et al found that the SFG signals of thiophenols grafted on gold nanospheres can be detected even if the surface coverage of thiophenol molecules is as low as 1%. , Wang et al significantly enhanced the monolayer SFG signals of p -mercaptobenzonitrile adsorbed on Au films by using shell-isolated nanoparticles as nanoantennas and found that the nonlinear coupling of SFG and DFG contributed to signal enhancement . The enhancement factor is reported to range from 10 to 10 5 . ,,,− However, a few very limited works have been reported to address the influence of plasmon local electric field on the enhancements in SFG intensity.…”

Colloidal Plasmonic Metasurfaces for the Enhancement of Non‐Linear Optical Processes and Molecular Spectroscopies

“…Currently, metasurfaces can display a virtually unlimited variety of shapes and compositions (Figure 2), including nanoholes, [36][37][38] nanoparticles, [39][40][41] pillars, [42,43] chiral shapes, [44][45][46][47][48] and antennas, [49][50][51][52] translating directly into an incredible versatility of their optical response, which can be tuned by modifying both the localized plasmonic response of each repeating unit, as well as the geometrical parameters of the array. These parameters will ultimately regulate the quality and the spectral position of all localized and collective resonances, driving the boost of quantum efficiency of the various NL optical processes.…”

Chiral Sum Frequency Generation by Chiral Gold Nanoparticles Amplifies Weak Sum Frequency Signals and Enables Monitoring of Enantioselective Reactions

“…This is advantageous because SFG signals can be weak depending on the order and symmetry of adsorbed molecules at the interface. , Therefore, plasmonic surface enhancement of signals, in analogy to surface-enhanced Raman spectroscopy, has been employed to increase achiral SFG signal levels. Plasmonic resonances can be excited in nanostructured materials, with concomitant amplification of electromagnetic fields at subwavelength particle dimensions. − Metal structures with plasmonic resonances overlapping with the fundamental or signal beams can lead to significant signal enhancement. − For this reason, the SFG response of metal nanoparticles with different sizes and shapes has been studied in detail.…”