Distance dependence of surface enhanced Raman scattering probed by alkanethiol self-assembled monolayers

Compagnini, Giuseppe; Galati, C.; Pignataro, S.

doi:10.1039/a901034c

Cited by 61 publications

(61 citation statements)

References 9 publications

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“…Several studies 17,18 performed on long chains of alkanethiols attached to silver surfaces show that the enhancement for remote chemical groups vanishes at extremely short distances (2 − 3 nm), which is in accordance with the theoretically predicted power law 17 ∼ 1 + h r −10 derived for a chaotic array of noninteracting nanoparticles, where r is the mean radius and h is the molecule-to-surface distance. Experiments using spacers created on nanostructured surfaces by atomic layer deposition of Al 2 O 3 also show very short-range SERS enhancements 19 , possibly resulting from the modification of the metal surface properties during the atomic layer deposition process.…”

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confidence: 83%

Long-range manifestation of surface-enhanced Raman scattering

2013

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The long-range action of surface-enhanced Raman scattering (SERS) is probed via distancedependent measurements of molecular Raman spectra. To this end, identical SERS substrates composed of irregular silver nanoisland arrays were covered by dielectric spacer layers with variable thickness, and the strength of the SERS signal produced from analyte molecules deposited on top of the structure was analyzed. The obtained distance dependence of the signal strength exhibited a shelf-like behavior up to 30 nm away from the enhancing surface and then rapidly decreased further away. Thus, the observed behavior of the electromagnetic mechanism of SERS enhancement in metal island films contradicts the widely accepted picture of extremely rapid (2-3 nm) decay of SERS-enhancement of 2D nanoparticle ensembles. Because of the observed steady enhancement factors at distances of ∼30 nm from the surface, SERS can be used for probing the spectra of macromolecules or other objects relatively distant from the metal surface. PACS numbers:Since its first observation by Fleischmann et al.(1974) 1 surface-enhanced Raman scattering (SERS) has been thoroughly investigated as an amazing physical phenomenon itself and one of the most promising tools for analytical applications. The first perception of SERS as a giant enhancement over conventional Raman scattering in experiments of Jeanmaire, Van Duyne 2 and Albrecht, Creighton 3 was followed by an extensive theoretical and experimental analysis, searching for the most general explanation of the enhancement mechanism. The enhancement of Raman scattering signals from organic molecules absorbed on nanostructured metal surfaces and photoexcited in a certain spectral range has been shown to reach 6-10 orders of magnitude 2,4 . Further enhancement of up to ∼14 orders of magnitude was observed on molecules residing in silver colloidal aggregates, enabling single molecule detection 5 . It is now generally agreed that more than one effect contributes to the total enhancement of Raman signals. The enhancement mechanisms are roughly divided into so-called electromagnetic (EM) field enhancement 6-8 and chemical first-layer effects 9-11 . The electromagnetic enhancement is caused by the enhanced local optical fields at the place of the molecule nearby the metal surface due to excitation of electromagnetic resonances, called surface plasmon polaritons. For isolated silver or gold spheroidal nanoparticles typical values for electromagnetic enhancement of SERS are on the order of 12,13 10 6 − 10 7 . For the more sophisticated case of closely spaced interacting particles (or clusters of particles), the individual dipole oscillators of the small particles couple, thereby generating normal modes of plasmon excitation that embrace the cluster. According to theoretical evaluations, the excitation is not distributed uniformly over the cluster but tends to be spatially localized in so-called "hot" areas [14][15][16] . Effects of chemical enhancement arise from the electronic coupling between the adsorbate molecule...

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confidence: 83%

Long-range manifestation of surface-enhanced Raman scattering

2013

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“…15 This technique is also highly surface specific, dropping off rapidly with increasing separation between the substrate and the SERS-active adsorbate. 16,17 Finally, the selection rules for SERS allow the detection of adsorbate vibrations with no component perpendicular to the surface (e.g. benzene bound in a planar geometry), unlike IR spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Attenuation of surface‐enhanced Raman spectroscopy response in gold–platinum core‐shell nanoparticles

Flynn¹,

Gewirth²

2002

J Raman Spectroscopy

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Colloidal gold particles (11.2 nm) were coated with platinum overlayers, resulting in bimetallic particles with 1-8 mol% Pt. These particles were characterized using electron microscopy, energy-dispersive x-ray spectroscopy and electrochemistry confirming the Au-Pt core-shell structure. The UV-visible spectra showed only minimal red shifts with increasing Pt content. The Raman spectra, on the other hand, changed dramatically with slight increases in Pt, resulting in a loss of appreciable surface-enhancement effects by 4 mol% Pt.

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“…14 This technique is based on the enhancement of Raman signals molecules adsorbed on rough metal surface. A distance dependence study of the surface enhanced Raman (SER) effect has been performed using alkanethiol [CH 3 -(CH 2 ) n SH] SAMs on top of rough silver surfaces by Giuseppe Compagnini et al 15 . They found decrease of the enhancement signal of the CH 3 heads by a factor of 2, increasing the CH 3 surface distance from 0⋅8 to 2⋅5 nm (n = 5-17).…”

Section: Surface Enhanced Raman Spectroscopy (Sers)mentioning

confidence: 99%

Tailoring self-assembled monolayers at the electrochemical interface

2009

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Abstract. The main focus of this review is to illustrate the amenability of self-assembled monolayers (SAMs) for functionalisation with different receptors, catalytic materials, biomolecules, enzymes, antigen-antibody, etc for various applications. The review discusses initially about the preparation and characterization of SAMs and tailoring of SAMs by incorporation of suitable recognition elements. A description of how the molecular recognition is achieved through forces like electrostatic, covalent and host-guest interactions is included in the review.

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Distance dependence of surface enhanced Raman scattering probed by alkanethiol self-assembled monolayers

Cited by 61 publications

References 9 publications

Long-range manifestation of surface-enhanced Raman scattering

Long-range manifestation of surface-enhanced Raman scattering

Attenuation of surface‐enhanced Raman spectroscopy response in gold–platinum core‐shell nanoparticles

Tailoring self-assembled monolayers at the electrochemical interface

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