Re-examining the origins of spectral blinking in single-molecule and single-nanoparticleSERS

Emory, Steven R.; Jensen, Rebecca A.; Wenda, Teresa; Han, Ming‐Yong; Nie, Shuming

doi:10.1039/b509223j

Cited by 116 publications

(159 citation statements)

References 56 publications

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“…However, we note that formation of a picocavity can be facilitated by the stability of goldthiol 'staples': two thiols cooperatively pull a gold atom into an elevated position forming a bridge-like arrangement (see (21) and references therein). Our findings are also in line with observations that SERS blinking has both a thermal-activated and a light-activated component (22). Picocavities only show up in near-field-sensitive measurements such as SERS, while no changes are seen in far-field scattering that depend only on the properties of the larger hosting nanocavity.…”

supporting

confidence: 80%

Single-molecule optomechanics in “picocavities”

Benz

Schmidt

Dreismann

et al. 2016

Science

738

854

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Coinage metal nanostructures support localised surface plasmons, which confine optical fields much tighter than their wavelength (1). This extreme enhancement enables vibrational spectroscopy within small volumes, even down to single molecules (2,3). For many years lateral resolution was believed to be 10 nm (4), however recent experiments resolve the atomic structure of single molecules using tipenhanced Raman spectroscopy (3) and directly sequence RNA strands (5). Atomistic simulations also suggest plasmonic confinement to atomic scales is possible (6). Here we show that light-activated mobilisation of surface atoms in a plasmonic hotspot triggers the formation of additional 'picocavities'bounded by a single gold atom. Their ultra-small light localisation alters which vibrational modes of trapped molecules are observed, due to strong optical field gradients that switch the Raman selection rules. The resulting cascaded ultra-strong plasmonic confinement pumps specific molecular bonds, thereby creating non-thermal vibrational populations, and forms a new type of optomechanical

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supporting

confidence: 80%

Single-molecule optomechanics in “picocavities”

Benz

Schmidt

Dreismann

et al. 2016

Science

738

854

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“…Therefore, the nature and the origin of SM-SERS blinking effect is still a hot topic in this field. One typical explanation for this phenomenon is that the blinking contains both a thermo-activated component and a light-induced component, which means that the blinking is caused from thermally activated diffusion of individual molecules on the particle surface coupled with photo-induced electron transfer and structural relaxation of surface active sites [42]. Therefore, an investigation of blinking effect (spectra fluctuations) will help in addressing some of the fundamental issues, such as the statistical ageing and entanglement of vibrational modes, etc.…”

Section: Basics Of Single-molecule Surface-enhancedmentioning

confidence: 99%

Surface-enhanced Raman spectroscopy at single-molecule scale and its implications in biology

Wang

Irudayaraj

2013

Phil. Trans. R. Soc. B

106

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Single-molecule (SM) spectroscopy has been an exciting area of research offering significant promise and hope in the field of sensor development to detect targets at ultra-low levels down to SM resolution. To the experts and developers in the field of surface-enhanced Raman spectroscopy (SERS), this has often been a challenge and a significant opportunity for exploration. Needless to say, the opportunities and excitement of this multidisciplinary area impacts span the fields of physics, chemistry and engineering, along with a significant thrust in applications constituting areas in medicine, biology, environment and agriculture among others. In this review, we will attempt to provide a quick snapshot of the basics of SM-SERS, nanostructures and devices that can enable SM Raman measurement. We will conclude with a discussion on SERS implications in biomedical sciences.

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“…Plasmonic junctions between extended electrodes (19-25) 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.We report vibrational mode softening in C 60 molecules on the order of tens of wavenumbers, approximately quadratic in the external dc bias, V, applied across such a junction. We compare these observations with density functional theory (DFT) calculations to determine the underlying mechanism.…”

mentioning

confidence: 99%

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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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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Re-examining the origins of spectral blinking in single-molecule and single-nanoparticleSERS

Cited by 116 publications

References 56 publications

Single-molecule optomechanics in “picocavities”

Single-molecule optomechanics in “picocavities”

Surface-enhanced Raman spectroscopy at single-molecule scale and its implications in biology

Voltage tuning of vibrational mode energies in single-molecule junctions

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