DFT, SERS, and Single-Molecule SERS of Crystal Violet

Cañamares, María Vega; Chenal, Cat; Birke, Ronald L.; Lombardi, John R.

doi:10.1021/jp807807j

Cited by 315 publications

(290 citation statements)

References 33 publications

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“…Thus, if the Fermi energy of the metal is around -4.1 eV, light of 2 eV (633 nm) will simultaneously excite both a molecule-to-metal CT transition and the π-π* molecular resonance, the latter with oscillator strength around 0.8. 31 In agreement with this conclusion, an electrochemical SERS study of CV + on a Ag surface showed a V MAX of -0.5 V vs SCE reference electrode. 32 In Figures 4 and 5, we illustrate the various resonances in a molecule-metal system for two commonly studied molecules, pyridine ( Figure 4) and crystal violet cation ( Figure 5).…”

Section: A Unified Expression For Serssupporting

confidence: 70%

A Unified View of Surface-Enhanced Raman Scattering

2009

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In the late 1970s, signal intensity in Raman spectroscopy was found to be enormously enhanced, by a factor of 10 6 and more recently by as much as 10 14 , when an analyte was placed in the vicinity of a metal nanoparticle (particularly Ag). The underlying source of this huge increase in signal in surface-enhanced Raman scattering (SERS) spectroscopy has since been characterized by considerable controversy. Three possible contributions to the enhancement factor have been identified: (i) the surface plasmon resonance in the metal nanoparticle, (ii) a charge-transfer resonance involving transfer of electrons between the molecule and the conduction band of the metal, and (iii) resonances within the molecule itself. These three components are often treated as independently contributing to the overall effect, with the implication that by properly choosing the experimental parameters, one or more can be ignored. Although varying experimental conditions can influence the relative degree to which each resonance influences the total enhancement, higher enhancements can often be obtained by combining two or more resonances. Each resonance has a somewhat different effect on the appearance of the resulting Raman spectrum, and it is necessary to invoke one or more of these resonances to completely describe a particular experiment. However, it is impossible to completely describe all observations of the SERS phenomenon without consideration of all three of these contributions. Furthermore, the relative enhancements of individual spectral lines, and therefore the appearance of the spectrum, depend crucially on the exact extent to which each resonance makes a contribution.In this Account, by examining breakdowns in the Born-Oppenheimer approximation, we have used Herzberg-Teller coupling to derive a single expression for SERS, which includes contributions from all three resonances. Moreover, we show that these three types of resonances are intimately linked by Herzberg-Teller vibronic coupling terms and cannot be considered separately.We also examine the differences between SERS and normal Raman spectra. Because of the various resonant contributions, SERS spectra vary with excitation wavelength considerably more than normal Raman spectra. The relative contributions of totally symmetric and non-totally symmetric lines are also quite different; these differences are due to several effects. The orientation of the molecule with respect to the surface and the inclusion of the metal Fermi level in the list of contributors to the accessible states of the molecule-metal system have a strong influence on the observed changes in the Raman spectrum.

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Section: A Unified Expression For Serssupporting

confidence: 70%

A Unified View of Surface-Enhanced Raman Scattering

2009

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“…The structures of these dyes are illustrated in Table 3. The interpretation of the obtained Raman spectra (Figure 4) using the data from the literature is presented in Table 4 [30][31][32]. Moreover, the Raman spectra corresponding to the B type recorded at 532 nm are resonant since this wavelength corresponds to the maximum of absorption band of dyes related to this ink type.…”

Section: Resultsmentioning

confidence: 94%

“…Data The results presented above were compared with the Raman peaks of other components of writing inks in order to analyze the overlapping peaks in the Raman spectra. For that purpose, the Raman spectra of pure solvents were measured ( Figure 6); as result, the solvent peaks were compared with the peaks of writing ink dyes of different types (Table 5 [ [30][31][32]). In Table 4, the frequencies referring to peaks, which were chosen to plot the time dependencies of peak intensity ratios [16], are highlighted in blue.…”

Section: Common Names (Ci Generic Name) Structural Formulamentioning

confidence: 99%

Analysis of the Aging Processes of Writing Ink: Raman Spectroscopy versus Gas Chromatography Aspects

Grechukha¹,

Gorshkova

Panov

et al. 2017

Applied Sciences

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This work is devoted to the extremely popular but poorly developed scientific and forensic problem of the estimation of the actual dates of inscriptions placed on paper and made by ballpoint pens. It is shown that the degradation of writing inks with time may be controlled via Raman spectroscopy and gas chromatography. The time intervals for the implementation of each of these methods were determined using the ratios of the Raman peak intensities as degradation characteristics rather than their absolute values. In turn, this eliminates the effect of the concentration of a dye. The mutual influence of the volatile components and dyes of writing inks was also investigated and the time interval within which such influence is critical was found. According to the obtained results, a new methodological scheme for determining the age of documents, which were created at least 40 months ago, was proposed.

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“…The SERS intensity varied appreciably with the soaking time, the density, and the distance between AuNPs immobilized on the substrates. Here, we focused our attention on the C-C in-plane stretching mode observed at 1,620 cm −1 [32]. Figure 3c shows the enhancement intensity as a function of the density of AuNPs adsorbed on the substrates (immersion time in the colloidal solution of AuNPs, see Fig.…”

Section: Resultsmentioning

confidence: 99%

Nanostructured and nanopatterned gold surfaces: application to the surface-enhanced Raman spectroscopy

et al. 2013

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Surface-enhanced Raman spectroscopy (SERS) has enormous potential for a range of applications where high sensitivity needs to be combined with good discrimination between molecular targets. However, the SERS technique has trouble finding its industrial development, as was the case with the surface plasmon resonance technology. The main reason is the difficulty to produce stable, reproducible, and highly efficient substrates for quantitative measurements. In this paper, we report a method to obtain two-dimensional regular nanopatterns of gold nanoparticles (AuNPs). The resulting patterns were evaluated by SERS. Our bottom-up strategy was divided into two steps: (a) nanopatterning of the substrate by e-beam lithography and (b) electrostatic adsorption of AuNPs on functionalized substrates. This approach enabled us to highlight the optimal conditions to obtain monolayer, rows, or ring of AuNPs, with homogeneous distribution and high density (800 AuNPs/μm 2 ). The nanostructure distributions on the substrates were displayed by scanning electron microscopy and atomic force microscopy images. Optical properties of our nanostructures were characterized by visible extinction spectra and by the measured enhancements of Raman scattering. Finally, we tried to demonstrate experimentally that, to observe a significant enhancement of SERS, the gold diffusers must be extremely closer. If electron beam lithography is a very attractive technique to perform reproducible SERS substrates, the realization of pattern needs a very high resolution, with distances between nanostructures probably of less than 20 nm.

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DFT, SERS, and Single-Molecule SERS of Crystal Violet

Cited by 315 publications

References 33 publications

A Unified View of Surface-Enhanced Raman Scattering

A Unified View of Surface-Enhanced Raman Scattering

Analysis of the Aging Processes of Writing Ink: Raman Spectroscopy versus Gas Chromatography Aspects

Nanostructured and nanopatterned gold surfaces: application to the surface-enhanced Raman spectroscopy

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