Single Molecule Dynamics at a Mechanically Controllable Break Junction in Solution at Room Temperature

Konishi, Tatsuya; Kiguchi, Manabu; Takase, Mai; Nagasawa, Fumika; Nabika, Hideki; Ikeda, Katsuyoshi; Uosaki, Kohei; Ueno, Kosei; Misawa, Hiroaki; Murakoshi, Kei

doi:10.1021/ja307821u

Cited by 144 publications

(165 citation statements)

References 34 publications

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“…As in previous studies (20,21,23,25,33), correlations as a function of time are observed between spectral intensity fluctuations ("blinking") and the measured conductance in the tunneling regime. Because the tunneling conductance is dominated by a molecular-scale volume at the point of closest interelectrode separation, these correlations imply few-or single-molecule Raman sensitivity.…”

supporting

confidence: 79%

“…Plasmonic junctions between extended electrodes (19)(20)(21)(22)(23)(24)(25) show correlations of Raman response and conductance implying single-or few-molecule sensitivity, and enable studies of vibrational physics as a function of electrical bias. Spectral diffusion often is observed in singlemolecule SERS experiments (18,25,26), and there is some preliminary evidence of bias-driven mode shifts in such junctions (23), with the mechanisms of these phenomena remaining unclear.…”

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confidence: 99%

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Voltage tuning of vibrational mode energies in single-molecule junctions

Doak

Kronik

et al. 2014

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

106

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Vibrational modes of molecules are fundamental properties determined by intramolecular bonding, atomic masses, and molecular geometry, and often serve as important channels for dissipation in nanoscale processes. Although single-molecule junctions have been used to manipulate electronic structure and related functional properties of molecules, electrical control of vibrational mode energies has remained elusive. Here we use simultaneous transport and surface-enhanced Raman spectroscopy measurements to demonstrate large, reversible, voltage-driven shifts of vibrational mode energies of C 60 molecules in gold junctions. C 60 mode energies are found to vary approximately quadratically with bias, but in a manner inconsistent with a simple vibrational Stark effect. Our theoretical model instead suggests that the mode shifts are a signature of bias-driven addition of electronic charge to the molecule. These results imply that voltage-controlled tuning of vibrational modes is a general phenomenon at metal-molecule interfaces and is a means of achieving significant shifts in vibrational energies relative to a pure Stark effect.plasmonics | nanoscale junctions | molecular electronics M echanical couplings between atoms within molecules, manifested through vibrational spectra, are critically important in many processes at the nanoscale, from energy dissipation to chemical reactions. These couplings originate from the self-consistent electronic structure and ionic positions within the molecule (1). Vibrational spectroscopy examines this bonding, and advanced time-resolved techniques (2-5) can manipulate vibrational populations. Single-molecule junctions (6, 7) also have proven to be valuable tools for examining vibrational physics. Previous work showed that vibrational frequencies may be altered in mechanical break junctions if the chemical linkage to the moving contacts is sufficient to strain bonds in the molecule (8, 9), but also showed vibrations to be unaffected when the linkage to the contacts is less robust (10). Controllably altering vibrational energies in the steady state is difficult, however. Electric fields can redistribute the molecular electron density and shift vibrational modes in the vibrational Stark effect (11), enabling spectroscopic probes of local static electric fields in charge double layers (12, 13) and biosystems (14-16). However, other physics also may be relevant, and studies of electrical tuning of molecular vibrational energies in single-or few-molecule-based solid-state junctions, which often provide clarity that is difficult to obtain from measurements of molecular ensembles, have been lacking.Surface-enhanced Raman spectroscopy (SERS) (17, 18), in which surface plasmons enhance the Raman scattering rate for molecules, opens up the possibility of performing detailed vibrational studies at the single-molecule level. Plasmonic junctions between extended electrodes (19-25) show correlations of Raman response and conductance implying single-or few-molecule sensitivity, and enable studies of vib...

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supporting

confidence: 79%

mentioning

confidence: 99%

Voltage tuning of vibrational mode energies in single-molecule junctions

Doak

Kronik

et al. 2014

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

106

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“…The mechanically controllable break junction (MCBJ) technique has been used for simultaneous measurements of SERS and conductivity [41][42][43][44][45]. Although the scanning probe technique is also available to characterize single-molecule junctions, this method is often suitable for high-speed conductance dynamics characterization during the breaking junction [27].…”

Section: Simultaneous Observation Of Sers and Conductivity Of A Singlmentioning

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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“…Surface-enhanced Raman scattering (SERS) is a promising tool for detecting the interactions between molecules and localized plasmons, especially for monitoring the plasmon-induced photoexcitation process. [11][12][13][14] Based on detailed SERS measurements of an isolated single-walled carbon nanotube (SWNT) by introducing a metal nanodimer with controlled nanogap, SWNTs with certain chirality have been observed via the resonant excitation of normally forbidden transitions. 15 The newly developed extended discrete dipole approximation method showed that the highly confined electromagnetic field at the nanogap (less than 2 nm) generates an intensity gradient of the field, resulting in the excitation of higher order polarization in the direction of the radial breathing mode in the SWNT.…”

Section: ¹1mentioning

confidence: 99%

Molecule Manipulation at Electrified Interfaces using Metal Nanogates

et al. 2014

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Previously documented results on molecule manipulation using metal nanogates are comprehensively reviewed to conclude novel characteristics, which could be widely used for the developments of the systems at electrified interfaces. Novel systems to segregate molecules from self-spreading lipid bilayers in electrolyte solutions have been developed by using metal nanogate structures on solid surfaces. The spatial distribution of target molecules in the lipid bilayer changes depending on the molecule characteristics, such as charge, size, and flexibility. Energy dissipation during the spreading of the molecules on the surface contributes to the compression of the lipid bilayer at the nanogate, leading to the formation of a gradient of the electrochemical potential of the bilayer system including the target molecule in the vicinity of the nanogate (<100 nm from the gate). The gradient results in a segregation force being applied to target molecules in the order of 10 −15 N per molecule. The segregation property can be tuned by changing the electrolytes, lipid molecules, temperature, and the width and surface hydrophobicity of the metal nanogate. Introduction of asymmetry to the nanogate leads to further effective diffusion control in a direction perpendicular to the spreading. It has been demonstrated that target molecules with a different number of glycolipid per protein in the lipid bilayer are effectively separated based on the Brownian ratchet mechanism.

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Single Molecule Dynamics at a Mechanically Controllable Break Junction in Solution at Room Temperature

Cited by 144 publications

References 34 publications

Voltage tuning of vibrational mode energies in single-molecule junctions

Voltage tuning of vibrational mode energies in single-molecule junctions

Single-site surface-enhanced Raman scattering beyond spectroscopy

Molecule Manipulation at Electrified Interfaces using Metal Nanogates

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