Effect of Electric Field Gradient on Sub-nanometer Spatial Resolution of Tip-enhanced Raman Spectroscopy

Meng, Lingyan; Yang, Zhilin; Chen, Jianing; Sun, Mengtao

doi:10.1038/srep09240

Cited by 88 publications

(81 citation statements)

References 29 publications

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“…Therefore, we can conclude that H2TBPP adopts the concave configuration in the experiments and the plasmonic size is around 2 nm. The conclusion for the size of plasmon is consistent with advanced EM simulations and further confirmed by a recent experiment …”

Section: Raman Images Of Single Moleculessupporting

confidence: 88%

Theoretical modeling of surface and tip‐enhanced Raman spectroscopies

Duan

Luo

2016

WIREs Comput Mol Sci

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Raman spectroscopy is a powerful technique in molecular science because of the ability of providing vibrational ‘finger‐print’. The developments of the surface‐enhanced Raman spectroscopy (SERS) and tip‐enhanced Raman spectroscopy (TERS) have significantly improved the detection sensitivity and efficiency. However, they also introduce complications for the spectral assignments, for which advanced theoretical modeling has played an important role. Here we summarize some of our recent progresses for SERS and TERS, which generally combine both solid‐state physics and quantum chemistry methods with two different schemes, namely the cluster model and the periodic boundary condition (PBC) model. In the cluster model, direct Raman spectra calculations are performed for the cluster taken from the accurate PBC structure. For PBC model, we have developed a quasi‐analytical approach that enables us to calculate the Raman spectra of entire system. Under the TERS condition, the non‐uniformity of plasmonic field in real space can drastically alter the interaction between the molecule and the light. By taking into account the local distributions of the plasmonic field, a new interaction Hamiltonian is constructed and applied to model the super‐high‐resolution Raman images of a single molecule. It shows that the resonant Raman images reflect the transition density between ground and excited states, which are generally vibrational insensitive. The nonresonant Raman images, on the other hand, allow to visualize the atomic movement of individual vibrational modes in real space. The inclusion of non‐uniformity of plasmonic field provides ample opportunities to discover new physics and new applications in the future. WIREs Comput Mol Sci 2017, 7:e1293. doi: 10.1002/wcms.1293 This article is categorized under: Structure and Mechanism > Molecular Structures Structure and Mechanism > Computational Materials Science Theoretical and Physical Chemistry > Spectroscopy

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Section: Raman Images Of Single Moleculessupporting

confidence: 88%

Theoretical modeling of surface and tip‐enhanced Raman spectroscopies

Duan

Luo

2016

WIREs Comput Mol Sci

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“…Besides, according to the definition, the first-order Taylor expansion for E(r, R T ) would lead to electric field gradient effects in Raman spectroscopy (or the socalled quadruple Raman), as discussed in the literature. 25,26,32,33 However, we should stress that with such a highly confined field employed in the modeling of the images, the use of the gradient term alone could not well describe the plasmonic field. Therefore, the higher-order terms have to be included.…”

mentioning

confidence: 99%

Theoretical Modeling of Plasmon-Enhanced Raman Images of a Single Molecule with Subnanometer Resolution

et al. 2015

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Under local plasmonic excitation, Raman images of single molecules can now surprisingly reach subnanometer resolution. However, its physical origin has not been fully understood. Here we report a quantum-mechanical description of the interaction between a molecule and a highly confined plasmonic field. We show that when the spatial distribution of the plasmonic field is comparable to the size of the molecule, the optical transition matrix of the molecule becomes dependent on the position and distribution of the plasmonic field, resulting in a spatially resolved high-resolution Raman image of the molecule. The resonant Raman image reflects the electronic transition density of the molecule. In combination with first-principles calculations, the simulated Raman image of a porphyrin derivative adsorbed on a silver surface nicely reproduces its experimental counterpart. The present theory provides the basic framework for describing linear and nonlinear responses of molecules under highly confined plasmonic fields.

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“…A highly confined electromagnetic field generates a huge gradient of field intensity, which may affect the spatial resolution and selection rule for the detection of specific vibrational modes [31]. The contribution of the field gradient on a TERS image is still under discussion [32]. The interpretation of the observed enhanced Raman spectrum with TERS requires further careful considerations on the interaction between the molecule and the LSPR field to determine the chemical structure, orientation, excited states of electrons, and vibrations of the molecule on the surface, even when the interaction with the surface is relatively weak [33].…”

Section: −8mentioning

confidence: 99%

Single-site surface-enhanced Raman scattering beyond spectroscopy

2016

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Recent progress in the observation of surface-enhanced Raman scattering (SERS) is reviewed to examine the possibility of finding a novel route for the effective photoexcitation of materials. The importance of well-controlled SERS experiments on a single molecule at a single site is discussed based on the difference in the information obtained from ensemble SERS measurements using multiple active sites with an uncontrolled number of molecules. A single-molecule SERS observation performed at a mechanically controllable breaking junction with a simultaneous conductivity measurement provides clear evidence of the drastic changes both in the intensity and in the Raman mode selectivity of the electromagnetic field generated by localized surface plasmon resonance. Careful control of the field at a few-nanometer-wide gap of a metal nanodimer results in the modification of the selection rule of electronic excitation of an isolated single-walled carbon nanotube. The examples shown in this review suggest that a single-site SERS observation could be used as a novel tool to find, develop, and implement applications of plasmon-induced photoexcitation of materials.

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Effect of Electric Field Gradient on Sub-nanometer Spatial Resolution of Tip-enhanced Raman Spectroscopy

Cited by 88 publications

References 29 publications

Theoretical modeling of surface and tip‐enhanced Raman spectroscopies

Theoretical modeling of surface and tip‐enhanced Raman spectroscopies

Theoretical Modeling of Plasmon-Enhanced Raman Images of a Single Molecule with Subnanometer Resolution

Single-site surface-enhanced Raman scattering beyond spectroscopy

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