“…[4] Substrate development is also a highly active area in SEIRS research. The substrates developed specifically for SEIRS include vacuum-deposited metal islands, [6] nanorod arrays, [20] subwavelength holes, [21] and nanoparticles (NPs). [6,7,[22][23][24][25][26][27] Recently, a SEIRS enhancement factor of 2000 was achieved by "in situ" tailoring of the size of the metallic nanofeatures.…”
Three-dimensional nanostructured metallic substrates for enhanced vibrational spectroscopy are fabricated by self-assembly. Nanostructures consisting of one to 20 depositions of 13 nm-diameter Au nanoparticles (NPs) on Au films are prepared and characterized by means of AFM and UV/Vis reflection-absorption spectroscopy. Surface-enhanced polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) is observed from Au NPs modified by the probe molecule 4-hydroxythiophenol. The limitation of this kind of substrate for surface-enhanced PM-IRRAS is discussed. The surface-enhanced Raman scattering (SERS) from the same probe molecule is also observed and the effect of the number of Au-NP depositions on the SERS efficiency is studied. The SERS signal from the probe molecule maximizes after 11 Au-NP depositions, and the absolute SERS intensities from different batches are reproducible within 20%. In situ electrochemical SERS measurements show that these substrates are stable within the potential window between -800 and +200 mV (vs. Ag/AgCl/sat. Cl(-)).
“…[4] Substrate development is also a highly active area in SEIRS research. The substrates developed specifically for SEIRS include vacuum-deposited metal islands, [6] nanorod arrays, [20] subwavelength holes, [21] and nanoparticles (NPs). [6,7,[22][23][24][25][26][27] Recently, a SEIRS enhancement factor of 2000 was achieved by "in situ" tailoring of the size of the metallic nanofeatures.…”
Three-dimensional nanostructured metallic substrates for enhanced vibrational spectroscopy are fabricated by self-assembly. Nanostructures consisting of one to 20 depositions of 13 nm-diameter Au nanoparticles (NPs) on Au films are prepared and characterized by means of AFM and UV/Vis reflection-absorption spectroscopy. Surface-enhanced polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) is observed from Au NPs modified by the probe molecule 4-hydroxythiophenol. The limitation of this kind of substrate for surface-enhanced PM-IRRAS is discussed. The surface-enhanced Raman scattering (SERS) from the same probe molecule is also observed and the effect of the number of Au-NP depositions on the SERS efficiency is studied. The SERS signal from the probe molecule maximizes after 11 Au-NP depositions, and the absolute SERS intensities from different batches are reproducible within 20%. In situ electrochemical SERS measurements show that these substrates are stable within the potential window between -800 and +200 mV (vs. Ag/AgCl/sat. Cl(-)).
“…[1][2][3][4][5][6][7][8][9][10] Recent works have experimented with the effects on transmission that arise from changing the hole shape. [11][12][13] The main findings of those works is that elliptical or rectangular holes can dramatically influence the polarization, the resonance wavelength, and the intensity of the transmission.…”
A theory is presented to describe the optical transmission through a rectangular hole in a real metal film. The previous theory of the transmission through a rectangular hole in a perfect electric conductor is extended to include the effects associated with having a real metal by adding surface-impedance boundary conditions and an effective index mode calculation. Both the peak and amplitude of the Fabry-Pérot resonance of the fundamental mode agree quantitatively with experiments. Finite-difference time-domain calculations are used to verify the theoretical findings as well as to show the effects of including loss, which is not included in the theory. The localized nature of the transmission resonances is also revealed by analyzing the electric field maps associated with the enhanced transmission process. DOI: 10.1103/PhysRevB.74.153411 PACS number͑s͒: 78.66.Bz, 42.25.Bs, 41.20.Jb, 42.79.Ag Observations of extraordinary optical transmission through arrays of subwavelength holes in metal films have spurred on intense research activity into understanding and utilizing this phenomenon. 1-10 Recent works have experimented with the effects on transmission that arise from changing the hole shape. [11][12][13] The main findings of those works is that elliptical or rectangular holes can dramatically influence the polarization, the resonance wavelength, and the intensity of the transmission. Random arrays of rectangular holes were used to demonstrate that a resonance exists in the transmission spectrum which is governed by the shape of the individual hole. 12 The peak wavelength of the resonance could be redshifted by decreasing the width of the short side of the hole. On the other hand, recent studies on isolated rectangular holes have shown the same effects of a resonance in transmission and a redshift that arises when reducing the width of the hole. 14 To explain how the shape-controlled resonance wavelength arises from a single hole, the influence of the hole shape on the cutoff wavelength of the modes within the hole was considered. 15 It was shown that the cutoff wavelength increases for a real metal due to increased coupling between evanescent fields on the long edges inside the hole. Later, the origin of the resonance was explained with a theory that incorporated the coupling between the mode inside the hole with the free-space regions on either side of the film. 16 The physical nature of this effect was attributed to a Fabry-Pérot resonance due to multiple reflections of the mode within the hole at the interfaces with the free-space regions. That theory did not capture the observed redshift phenomenon that arises when the width of the hole is reduced in a real metal because it considered only a perfect electric conductor.In this paper, a theory that describes quantitatively the transmission resonance for a rectangular hole in a metal film is presented. Here, the previous theory has been generalized to allow for a finite dielectric constant, and thereby captures the new physics associated with having a real ...
“…also Figure 3 in Ref. [122]). Nevertheless, the signal enhancement was strong enough to detect the much weaker CH 2 -wagging and rocking modes and their progression with increasing chain length, thanks to a good S/N achieved by averaging 1000 scans.…”
At the beginning of the 1980s, the first reports of surface-enhanced infrared spectroscopy (SEIRS) surfaced. Probably due to signal-enhancement factors of only 10 1 to 10 3 , which are modest compared to those of surface-enhanced Raman spectroscopy (SERS), SEIRS did not reach the same significance up to date. However, taking the compared to Raman scattering much larger crosssections of infrared absorptions and the enhancement factors together, SEIRS reaches about the same sensitivity for molecular species on a surface in terms of the crosssections as SERS and, due to the complementary nature of both techniques, can valuably augment information gained by SERS. For the first 20 years since its discovery, SEIRS relied completely on metal island films, fabricated by either vapor or electrochemical deposition. The resulting films showed a strong variance concerning their structure, which was essentially random. Therefore, the increase in the corresponding signal-enhancement factors of these structures stagnated in the last years. In the very same years, however, the development of periodic array-based substrates helped SEIRS to gather momentum. This development was supported by technological progress concerning electromagnetic field solvers, which help to understand plasmonic properties and allow targeted design. In addition, the strong progress concerning modern fabrication methods allowed to implement these designs into practice. The aim of this contribution is to critically review the development of these engineered surfaces for SEIRS, to compare the different approaches with regard to their performance where possible, and report further gain of knowledge around and in relation to these structures.
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