Surface-Enhanced Raman Scattering Spectroscopy of Single Carbon Domains on Individual Ag Nanoparticles on a 25 ms Time Scale

Moyer, Patrick J.; Schmidt, Jochen; Eng, Lukas M.; Meixner, Alfred J.; Sandmann, G.; Dietz, and Hartmut; Plieth, W.

doi:10.1021/ja000703g

Cited by 82 publications

(114 citation statements)

References 17 publications

(39 reference statements)

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“…14 Similarly, Moyer et al observed SERS of single carbon domains from 75% of the Ag particles in their sample, all of which consisted of clusters of Ag crystallites. 15 It is well-known that the addition of low concentrations of Cl -ions (1-10 mM) to the Ag colloid yields significant increases in SERS signals. Since extinction spectra, TEM, and AFM measurements have shown that such low quantities of Cl -ions do not cause any significant aggregation of the sample, it has often been proposed that the anions serve as "activating agents".…”

Section: Resultsmentioning

confidence: 99%

Ag Nanocrystal Junctions as the Site for Surface-Enhanced Raman Scattering of Single Rhodamine 6G Molecules

2000

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Atomic force microscopy (AFM) measurements show that the Ag nanoparticles that yield surface-enhanced Raman scattering (SERS) of single molecules of Rhodamine (R6G) are all compact aggregates consisting of a minimum of two individual particles. Comparison of 514.5 and 632.8 nm excitation shows that the single molecule R6G signal is significantly higher when the excitation wavelength is resonant with the absorption band of R6G and suggests that the Raman excitation spectrum follows the absorption profile for R6G. We have also observed an interesting superlinear power dependence of the SERS signal. On average, by increasing the incident power by 2 orders of magnitude and decreasing the integration time by the same factor to maintain constant fluence, increases of 4 to 6 times were observed in the SERS intensity. We discuss these results in terms of model where the R6G molecule that yields single molecule SERS signals is located at the junction of two Ag nanoparticles. We have also modeled the system using molecular resonance Raman theory to provide further insight into the enhancement mechanism.

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Section: Resultsmentioning

confidence: 99%

Ag Nanocrystal Junctions as the Site for Surface-Enhanced Raman Scattering of Single Rhodamine 6G Molecules

2000

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“…3a of Ref. 1, we refer to SER studies on carbon chain segments by Kudelski and Pettinger 15 and on single carbon domains on individual Ag nanoparticles by Meixner et al 16 We claim that the broad bands between 1530 cm -1 and 1590 cm -1 and between 1295 cm -1 and 1342 cm -1 are due to carbon contamination and that the MG near-field spectra presented in Ref. 1, in fact, show carbonaceous species resulting from the (photo)decomposition of MG.…”

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confidence: 99%

“…Broad bands are found at 1590 cm -1 and 1380 cm -1 for carbon on Ag 16 and at 1580 cm -1 and 1340 cm -1 for carbon at Au, 15 respectively, denoted in the literature as D-and G-bands. The spectra show large fluctuations over time, similar to the ones observed by Neacsu et al (Fig.…”

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Comment on “Scanning-probe Raman spectroscopy with single-molecule sensitivity”

Domke

Pettinger

2007

Phys. Rev. B

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We reinterpret the scanning-probe Raman spectra shown in the above paper [C.C. Neacsu et al., Phys. Rev. B 73, 193406 (2006)] and compare it to a variety of single-molecule surface-enhanced Raman (SER) studies. The observed blinking behaviour and spectral features must be attributed to carbon contaminations rather than to Malachite Green (MG) single molecules, because, under the given experimental conditions, the extremely high field enhancement of 5 x 10 9 will inevitably lead to a quick (photo)decomposition of the adsorbate.PACS numbers: 68.37. Uv, 33.20.Fb In a recent paper, 1 Neacsu et al. present an AFMtip-enhanced Raman (TER) study on Malachite Green (MG) at gold films. They analyze near-field (tip approx. 5 nm above sample surface) and far-field (tip several 100 nm above sample surface) spectra of a Au surface covered with MG at low adsorbate concentration in correlation with a DFT calculation as well as of the clean Au surface. In a time series of 100 AFM-TER spectra (1 s integration time per spectrum) for a submonolayer MG surface coverage, spectral diffusion is observed and interpreted as characteristic single-molecule (SM) behaviour due to "random surface diffusion of MG in and out of the near-field-confined surface area under the tip, facilitated by the thin most likely liquid water layer on the gold surface". A Raman enhancement of up to 5 x 10 9 is derived from comparison of tip-enhanced versus far-field response of the same surface monolayer.Figures 2b and 2c in Ref. 1 show a near-field (tip approached) and a far-field (no tip) spectrum of MG on Au, respectively. The far-field spectrum exhibits the typical Raman features of MG which can be ssigned according to Lueck et al. 2 ) and a DFT calculation (Fig. 2c in Ref. 1), but the near-field spectrum does not resemble neither the far-field nor the DFT spectrum.The authors state that "the pronounced spectral difference between the tip-enhanced and the far-field response resembles the observation frequently made in SERS" (surface-enhanced Raman spectroscopy) and claim that "this characteristical difference is the result of the strong optical field localization, and related to different selection rules for the tip-scattered response, akin to SERS". Different selection rules cannot be held responsible for the so remarkable differences between near-field and farfield spectra presented by Neacsu et al. Note in this context that SER as well as TER spectra usually strongly resemble the far-field spectra of the investigated species in the band positions, in a way that the unambiguous identification of the molecule is always possible. In fact, a comparison of the Raman bands found in literature for MG in water (far-field, Ref. 2) and MG on silver colloids (near-field, Ref.3) does not reveal any band displacements larger than ± 3 cm −1 , and also the relative band intensities are similar. Variations in band intensities may occur according to surface selection rules (changes in the polarizability perpendicularly to the surface, i.e. parallel to the incident...

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“…We attribute these relatively intense and broad bands of amorphous carbon [235][236][237][238] to burning events, caused by locally increased temperatures. Although low laser doses are used, the cell samples are prone to burning because they are dry and reside on a gold layer.…”

Section: 236mentioning

confidence: 96%

Microspectroscopic characterisation of gold nanorods for cancer detection

Hartsuiker

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Surface-Enhanced Raman Scattering Spectroscopy of Single Carbon Domains on Individual Ag Nanoparticles on a 25 ms Time Scale

Cited by 82 publications

References 17 publications

Ag Nanocrystal Junctions as the Site for Surface-Enhanced Raman Scattering of Single Rhodamine 6G Molecules

Ag Nanocrystal Junctions as the Site for Surface-Enhanced Raman Scattering of Single Rhodamine 6G Molecules

Comment on “Scanning-probe Raman spectroscopy with single-molecule sensitivity”

Microspectroscopic characterisation of gold nanorods for cancer detection

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