Probing Adsorption Configurations of Small Molecules on Surfaces by Single‐Molecule Tip‐Enhanced Raman Spectroscopy

Zhang, Yao; Zhang, Rui; Jiang, Song; Dong, Zhen‐Chao

doi:10.1002/cphc.201800861

Cited by 24 publications

(25 citation statements)

References 39 publications

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“…For the flat‐lying and latericumbent‐lying configurations (brown and purple lines in Figure 4b), the atomistic Raman spectrum is quite similar to the nonresonance illumination condition in Figure 4a, because for those particular configurations, all the atoms are located in a region of electric field with nearly homogeneous intensity distribution. This also coincides with the spectral features observed in experiments for the 44BPY molecule in a relatively homogeneous field [65] …”

Section: Scanning Raman Picoscopy Of a Single Moleculesupporting

confidence: 89%

Theoretical treatment of single‐molecule scanning Raman picoscopy in strongly inhomogeneous near fields

Zhang

Dong

Aizpurua

2020

J Raman Spectroscopy

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Tip‐enhanced Raman spectroscopy (TERS) of a single molecule is commonly described by considering the change in the polarizability of the molecule with respect to a normal coordinate induced by homogeneous illumination. However, the local fields induced by nanoscale and atomic‐scale features at the surface of metallic clusters and nanogaps show strong inhomogeneities in their spatial distribution, which induces breaking of Raman selection rules. In this context, the spatial extension of the molecular electronic states subjected to strongly varying local fields challenges the validity of the point–dipole approximation as an adequate description of TERS in such configurations. Here, we introduce a general treatment to simulate single‐molecule TERS spectra and their energy‐filtered vibrational fingerprints maps, in which the polarization properties of the single molecule and that of the optical enhancing nanoresonator can be calculated separately and then conveniently combined to obtain the total Raman cross section of the molecule under the strongly inhomogeneous field. We apply the general method to study tip‐enhanced scanning Raman picoscopy of a 4,4′‐bipyridine and biphenyl molecules in the proximity of a silver icosahedral cluster with a few atoms at the tip apex mimicking an enhancing picocavity. The polarization of the molecules is calculated within density functional theory (DFT), and the optical response of the tip is calculated within a classical atomistic discrete–dipole approximation. The Raman spectra are found to be extremely sensitive to the spatial distribution of the local fields and to the orientation of the molecule. Our calculations show that the spatial mapping of molecular vibrational fingerprints, as probed by a tip with atomic protrusions, is capable to reveal intramolecular features of a single molecule in real space and thus establish a robust basis for scanning Raman picoscopy.

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Section: Scanning Raman Picoscopy Of a Single Moleculesupporting

confidence: 89%

Theoretical treatment of single‐molecule scanning Raman picoscopy in strongly inhomogeneous near fields

Zhang

Dong

Aizpurua

2020

J Raman Spectroscopy

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“…Improves lateral spatial resolution to as low as 10 nm, about the diameter of the tip probe. Achieves single molecule detection and discrimination of bacterial pathogens [167,168].…”

Section: Tip-enhanced Raman Spectroscopy (Ters)mentioning

confidence: 99%

Enhancing Disease Diagnosis: Biomedical Applications of Surface-Enhanced Raman Scattering

et al. 2019

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Surface-enhanced Raman scattering (SERS) has recently gained increasing attention for the detection of trace quantities of biomolecules due to its excellent molecular specificity, ultrasensitivity, and quantitative multiplex ability. Specific single or multiple biomarkers in complex biological environments generate strong and distinct SERS spectral signals when they are in the vicinity of optically active nanoparticles (NPs). When multivariate chemometrics are applied to decipher underlying biomarker patterns, SERS provides qualitative and quantitative information on the inherent biochemical composition and properties that may be indicative of healthy or diseased states. Moreover, SERS allows for differentiation among many closely-related causative agents of diseases exhibiting similar symptoms to guide early prescription of appropriate, targeted and individualised therapeutics. This review provides an overview of recent progress made by the application of SERS in the diagnosis of cancers, microbial and respiratory infections. It is envisaged that recent technology development will help realise full benefits of SERS to gain deeper insights into the pathological pathways for various diseases at the molecular level.

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“…As shown in Figure 1f, the typical TERS spectrum (red spectrum) acquired from the BPY monolayer is characterized by a dominant peak at ∼806 cm −1 , which is different from the corresponding powder Raman spectra (brown spectrum). Previous TERS studies [ 45 ] have suggested that the distinct difference between the TERS and normal Raman of BPY molecules is attributed to the surface selection rule of TERS as well as the change in the molecular adsorption configurations. The strong peak at ∼806 cm −1 in the observed TERS spectra is associated with an out‐of‐plane vibration for a flat‐lying adsorption configuration of BPY on Ag(111), giving further justification for the structural model proposed in Figure 1e.…”

Section: Resultsmentioning

confidence: 99%

Bicomponent supramolecular self‐assemblies studied with tip‐enhanced Raman spectroscopy

Jiang

Zhang

et al. 2020

J Raman Spectroscopy

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The formation of well‐ordered supramolecular self‐assembly based on cytosine and 4,4′‐bipyridine on Ag(111) has been investigated with subnanometer‐resolved tip‐enhanced Raman spectroscopy (TERS) using a low‐temperature ultrahigh‐vacuum scanning tunneling microscope (STM). The co‐deposition of two molecules on the Ag(111) surface held at room temperature results in well‐ordered hydrogen‐bonded monolayer islands, which transform into well‐aligned double‐stranded chains after thermal annealing. Site‐dependent TERS spectra help to identify the packing structures of molecular assemblies. The changes of molecule‐specific vibrational fingerprints across the assemblies can be clearly monitored by combining high‐resolution TERS spectra with advanced multivariate analysis. Furthermore, the peak positions and relative intensities for characteristic vibrational modes of the two molecules are found to vary due to the changes of the local hydrogen bonding and interaction environment in different molecular samples. Our findings demonstrate that TERS is sensitive to the local molecular interactions, provides new potentials to monitor the functionality of molecular architectures on demand, and opens new opportunities to probe surface chemistry at the nanoscale.

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Probing Adsorption Configurations of Small Molecules on Surfaces by Single‐Molecule Tip‐Enhanced Raman Spectroscopy

Cited by 24 publications

References 39 publications

Theoretical treatment of single‐molecule scanning Raman picoscopy in strongly inhomogeneous near fields

Theoretical treatment of single‐molecule scanning Raman picoscopy in strongly inhomogeneous near fields

Enhancing Disease Diagnosis: Biomedical Applications of Surface-Enhanced Raman Scattering

Bicomponent supramolecular self‐assemblies studied with tip‐enhanced Raman spectroscopy

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