Nanoscale Vibrational Analysis of Single-Walled Carbon Nanotubes

Anderson, Neil; Hartschuh, Achim; Cronin, Steve; Novotny, Lukas

doi:10.1021/ja045190i

Cited by 224 publications

(177 citation statements)

References 21 publications

Supporting

Mentioning

164

Contrasting

Unclassified

Order By: Relevance

“…Ren ular adsorbates on smooth single-crystal substrates (Figure 6; 56). Anderson et al have applied TERS to study single-walled carbon nanotubes with 14-nm spatial resolution (57). These experiments demonstrate the technique's salient features, which are the ability to probe molecules on non-SERS active substrates and high spatial resolution.…”

Section: The Futurementioning

confidence: 98%

Surface-Enhanced Raman Spectroscopy

Haynes¹,

McFarland²,

Duyne³

2005

Anal. Chem.

1,077

855

View full text Add to dashboard Cite

mekal theoretically predicted inelastic light scattering in 1923 (1). Raman and Krishnan first experimentally observed the phenomenon and reported in their 1928 Nature paper that the inelastic scattering effect was characterized by "its feebleness in comparison with the ordinary scattering" (2). This "feeble" phenomenon is now known as Raman scattering. The change in wavelength that is observed when a photon undergoes Raman scattering is attributed to the excitation (or relaxation) of vibrational modes of a molecule. Because different functional groups have different characteristic vibrational energies, every molecule has a unique Raman spectrum. In accordance with the Raman selection rule, the molecular polarizability changes as the molecular vibrations displace the constituent atoms from their equilibrium positions. The intensity of Raman scattering is proportional to the magnitude of the change in molecular polarizability. Thus, aromatic molecules exhibit more intense Raman scattering than aliphatic molecules.Even so, Raman scattering cross sections are typically 14 orders of magnitude smaller than those of fluorescence; therefore, the Raman signal is still several orders of magnitude weaker than the fluorescence emission in most cases. Because of the inherently small intensity of the Raman signal, the sensitivity limits of available detectors, and the intensity of the excitation sources, the applicability of Raman scattering was restricted for many years. However, its utility as an analytical technique improved with the advent of the laser and the evolution of photon detection technology.In 1977, Jeanmaire and Van Duyne demonstrated that the magnitude of the Raman scattering signal can be greatly enhanced when the scatterer is placed on or near a roughened noble-metal substrate (3). Strong electromagnetic fields are generated when the localized surface plasmon resonance (LSPR) of nanoscale roughness features on a silver, gold, or copper substrate is excited by visible light. When the Raman scatterer is subjected to these intensified electromagnetic fields, the magnitude of the induced dipole increases, and accordingly, the intensity of the inelastic scattering increases. This enhanced scattering process is known as surface-enhanced Raman (SER) scattering-a term that emphasizes the key role of the noblemetal substrate in this phenomenon.

show abstract

Section: The Futurementioning

confidence: 98%

Surface-Enhanced Raman Spectroscopy

Haynes¹,

McFarland²,

Duyne³

2005

Anal. Chem.

1,077

855

View full text Add to dashboard Cite

show abstract

“…[1] The tip apex functions as a single 'hot' spot, which enhances the Raman scattering from the scanned sample area. At optimized conditions, single-molecule sensitivity [2] can be achieved and the spatial resolution can reach ∼10 nm, [3] making TERS an important candidate for nanoscale chemical analysis.…”

Section: Introductionmentioning

confidence: 99%

Local field enhancement of an infinite conical metal tip illuminated by a focused beam

Zhang

Cui

Martin

2009

J Raman Spectroscopy

View full text Add to dashboard Cite

We present a systematic numerical investigation of conical metal tips which are commonly used in tip-enhanced Raman spectroscopy (TERS). Different from previous studies, we focus on how the tip length and the illumination condition influence the local field enhancement at the tip apex, and provide a useful reference for real experiments. In particular, we show that the type of illumination has a dramatic influence on the field enhancement: a localized illumination spot -as used in experiments -producing a very different response than a plane wave illumination -as usually used in previous models. Also, the effect of the different geometrical parameters, such as the sharpness of the tip apex and the cone angle, provides guidance to optimize the tip design. Finally, we investigate the influence of the substrate and compare numerical data with results deduced from a simplified model, finding good agreement. This brings new insights into the enhancement mechanism of TERS.

show abstract

“…Surface-enhanced (resonance) Raman spectroscopy [SE(R)RS] from a metal-coated AFM tip does not suffer from these limitations. Indeed, it has been shown that fingerprint signatures of molecules and functional groups can be obtained with this technique, in the best case with nanometer resolution (72,73). As illustrated in Fig.…”

Section: Integration Of Techniques and Perspectivesmentioning

confidence: 97%

Single-molecule fluorescence spectroscopy in (bio)catalysis

Roeffaers

Cremer

Uji‐i

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

146

114

View full text Add to dashboard Cite

The ever-improving time and space resolution and molecular detection sensitivity of fluorescence microscopy offer unique opportunities to deepen our insights into the function of chemical and biological catalysts. Because single-molecule microscopy allows for counting the turnover events one by one, one can map the distribution of the catalytic activities of different sites in solid heterogeneous catalysts, or one can study time-dependent activity fluctuations of individual sites in enzymes or chemical catalysts. By experimentally monitoring individuals rather than populations, the origin of complex behavior, e.g., in kinetics or in deactivation processes, can be successfully elucidated. Recent progress of temporal and spatial resolution in single-molecule fluorescence microscopy is discussed in light of its impact on catalytic assays. Key concepts are illustrated regarding the use of fluorescent reporters in catalytic reactions. Future challenges comprising the integration of other techniques, such as diffraction, scanning probe, or vibrational methods in single-molecule fluorescence spectroscopy are suggested.S ingle-molecule fluorescence spectroscopy (SMFS) has recently developed into a powerful tool for studying biophysical and biochemical phenomena. In studies of enzymatic catalysis, SMFS has revealed that there are large differences between the catalytic activity of individual enzymes within a population (''static disorder'') and that the rate constant (k cat ) of an individual enzyme may strongly fluctuate over time (''dynamic disorder''), the latter resulting from conformational changes of the enzyme. The recent application of SMFS to catalysis by solid materials has shown that heterogeneities in k cat also exist between individual catalytic crystals of one powder sample and even between the sites of an individual crystal. In this case, heterogeneity might arise from different chemical environments within the catalyst sample. The observation of heterogeneity in the k cat of those different catalytic systems suggests that the parallel introduction and evolution of SMFS techniques in bioand chemocatalysis will deepen our insights in almost any type of catalytic conversion. Indeed, the challenge to derive overall kinetics from the contributions of individuals within a population is essentially the same for biological, heterogeneous and even homogeneous systems, as discussed in From Populations to Individuals.From a technical viewpoint, SMFS requires strongly fluorescent probe molecules. The concepts to use such probes and even the probes themselves can be exchanged freely between heterogeneous, homogeneous, and biocatalysis, as discussed in Probes for SMFS in (Bio)Catalysis. If one wants to map in even more detail the contributions of the individual enzymes or catalytic sites to the overall kinetics, further improvements of the spatial and temporal resolution of SMFS will be required (see Spatial Resolution: Micro-and Nanoscopy and Time Resolution and Dynamics). Finally, to complement the information from S...

show abstract

Nanoscale Vibrational Analysis of Single-Walled Carbon Nanotubes

Cited by 224 publications

References 21 publications

Surface-Enhanced Raman Spectroscopy

Surface-Enhanced Raman Spectroscopy

Local field enhancement of an infinite conical metal tip illuminated by a focused beam

Single-molecule fluorescence spectroscopy in (bio)catalysis

Contact Info

Product

Resources

About