Impact of the plasmonic near- and far-field resonance-energy shift on the enhancement of infrared vibrational signals

Vogt, Jochen; Huck, Christian; Neubrech, Frank; Toma, Andréa; Gerbert, David; Pucci, Annemarie

doi:10.1039/c4cp04851b

Cited by 65 publications

(110 citation statements)

References 44 publications

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“…5,19,20 Here we point out that the ratio between the antenna's scattering losses and intrinsic losses is an important design parameter to consider for the hosting antennas which can be tuned to optimize the SEIRA performance. In order to prove this, we present results for a series of antennas which have the same resonance frequency but different volume and hence different proportion between the maximum values of their scattering and absorption cross sections (scattering−absorption ratio).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…21 In the SEIRA simulations, the length and the diameter respectively of the antenna are chosen to lead to a match of the plasmonic resonance and the vibrational spectral feature, which is the basic condition for a high SEIRA signal. 5,6,19,20 The values of l and d are given in the figures. The given length l is the total length including the caps.…”

Section: ■ Experimental and Simulation Methodsmentioning

confidence: 99%

“…The absorption and scattering cross sections were calculated by considering the net power flowing inward and outward, respectively, through the respective evaluation surface embedding the antenna. The SEIRA signal size (contrast) is evaluated as a difference between the maximum and the minimum of the baseline corrected cross-section spectrum, 5,11,14,19,20 using the smoothing algorithm proposed by Eilers. 21 In the SEIRA simulations, the length and the diameter respectively of the antenna are chosen to lead to a match of the plasmonic resonance and the vibrational spectral feature, which is the basic condition for a high SEIRA signal.…”

Section: ■ Experimental and Simulation Methodsmentioning

confidence: 99%

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Importance of Plasmonic Scattering for an Optimal Enhancement of Vibrational Absorption in SEIRA with Linear Metallic Antennas

et al. 2015

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Surface-enhanced infrared absorption (SEIRA) and surface-enhanced Raman scattering (SERS) represent very effective techniques to detect molecular vibrational fingerprints. These techniques can be improved thanks to the use of plasmonic antennas that produce strong resonant near-fields in their vicinity, enhancing the signal of vibrational samples. Here we study the role of plasmonic absorption and scattering of the hosting antennas in the resulting SEIRA signal. Using numerical simulations of the antenna−sample infrared response, we show that the optimal SEIRA signal measured in transmittance (as extinction) is achieved when the spectral maxima of absorption and scattering of the antennas are of similar magnitude. Paradoxically, when the optimal condition for SEIRA is fulfilled, the decomposition of the signal into the contribution from scattering and from absorption show that the vibrational fingerprint is exclusively a result of the scattering, with no contribution from absorption. Using a simple analytical model for the description of the fundamental resonance of linear nanoantennas made of a Drude-type metal, we provide guidelines for controlling the plasmonic light scattering and light absorption properties, thus showing how the optimal condition for SEIRA can be achieved in practical situations. ■ INTRODUCTIONInfrared (IR) vibrational spectroscopy is a powerful tool for the identification of the chemical composition and the molecular geometry via the vibrational fingerprints. However, one big problem hampers the successful application of IR spectroscopy, especially in the case where small amounts of molecules are present. This problem consists in the extremely small IR absorption cross section of molecules which is much smaller than the squared wavelength of the probing IR radiation at the vibrational frequency of the molecule (see Supporting Information). This problem can be overcome by placing the molecule into strongly enhanced electromagnetic near-fields, for example, such of a resonant plasmonic antenna. In this article we will demonstrate that the resonant plasmonic scattering of these hosting antennas is especially relevant for the measurement of enhanced IR vibrational absorption signals.The first findings on enhanced signals of molecules on metal nanoparticles, ca. 50 years ago, were named "anomalous transmission".1 This kind of surface-enhanced IR absorption (SEIRA) of adsorbates on metal−nanoparticle aggregates can reach 3 orders of magnitude and can be modeled by effective media theories (EMT) if the particles are small enough. Usually, the metal nanoparticles in such SEIRA studies have diameters of only a few nanometers, and therefore their light scattering (proportional to the fourth power of the ratio of the particle diameter to the wavelength) almost vanishes in the IR. On the other hand, the optical absorption of these structures even in the IR is strong because the mutual interaction of the nanoparticles broadens and red-shifts their resonances.3 The observed vibrational line-sh...

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Experimental and Simulation Methodsmentioning

confidence: 99%

Section: ■ Experimental and Simulation Methodsmentioning

confidence: 99%

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Importance of Plasmonic Scattering for an Optimal Enhancement of Vibrational Absorption in SEIRA with Linear Metallic Antennas

et al. 2015

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“…The first is the fact that the wavenumber of a plasmonic resonance extracted from far-field measurements (assuming that a maximum or minimum in a spectrum equals this wavenumber) usually differs from the position of the highest enhancement by up to 100 cm −1 [28]. This difference is, as Vogt et al point out, probably insignificant in the few cases of .…”

Section: On-resonance Enhancementmentioning

confidence: 98%

Periodic array-based substrates for surface-enhanced infrared spectroscopy

Mayerhöfer

Popp

2017

Nanophotonics

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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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“…The polarization selective resonances of the investigated HDSC nanoantennas are particularly suitable for resonant SEIRA spectroscopy at mid-IR wavelengths. The condition of the resonant tuning between the large plasmonic resonance and the narrow IR absorption features of molecules is fulfilled at two center wavelengths and covers several absorption features close to the longitudinal and transverse resonance wavelengths, especially on the long wavelength side of the resonance maximum [50]. As a case study for SEIRA and SPR, we used vanillin (4-hydroxy-3-methoxybenzaldehyde) as an analyte molecule.…”

Section: Resonant Seira and Spr Sensing Demonstrationmentioning

confidence: 99%

Highly doped semiconductor plasmonic nanoantenna arrays for polarization selective broadband surface-enhanced infrared absorption spectroscopy of vanillin

et al. 2017

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Tailored plasmonic nanoantennas are needed for diverse applications, among those sensing. Surfaceenhanced infrared absorption (SEIRA) spectroscopy using adapted nanoantenna substrates is an efficient technique for the selective detection of molecules by their vibrational spectra, even in small quantity. Highly doped semiconductors have been proposed as innovative materials for plasmonics, especially for more flexibility concerning the targeted spectral range. Here, we report on rectangularshaped, highly Si-doped InAsSb nanoantennas sustaining polarization switchable longitudinal and transverse plasmonic resonances in the mid-infrared. For small array periodicities, the highest reflectance intensity is obtained. Large periodicities can be used to combine localized surface plasmon resonances (SPR) with array resonances, as shown in electromagnetic calculations. The nanoantenna arrays can be efficiently used for broadband SEIRA spectroscopy, exploiting the spectral overlap between the large longitudinal or transverse plasmonic resonances and narrow infrared active absorption features of an analyte molecule. We demonstrate an increase of the vibrational line intensity up to a factor of 5.7 of infrared-active absorption features of vanillin in the fingerprint spectral region, yielding enhancement factors of three to four orders of magnitude. Moreover, an optimized readout for SPR sensing is proposed based on slightly overlapping longitudinal and transverse localized SPR.

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Impact of the plasmonic near- and far-field resonance-energy shift on the enhancement of infrared vibrational signals

Cited by 65 publications

References 44 publications

Importance of Plasmonic Scattering for an Optimal Enhancement of Vibrational Absorption in SEIRA with Linear Metallic Antennas

Importance of Plasmonic Scattering for an Optimal Enhancement of Vibrational Absorption in SEIRA with Linear Metallic Antennas

Periodic array-based substrates for surface-enhanced infrared spectroscopy

Highly doped semiconductor plasmonic nanoantenna arrays for polarization selective broadband surface-enhanced infrared absorption spectroscopy of vanillin

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