Excited electron dynamics at ferrocene-terminated self-assembled monolayers on Au(111): Lengthened lifetime of image potential state

Hirata, Naoyuki; Shibuta, Masahiro; Eguchi, Toyoaki; Nakajima, Atsushi

doi:10.1016/j.cplett.2013.01.053

Cited by 9 publications

(13 citation statements)

References 45 publications

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“…Figure a shows single-color 2PPE spectra with various photon energies ( h ν) ranging from h ν 1 = 4.47 to 5.17 eV. A peak at 3.84 eV above the Fermi level ( E F ) originates from the first IPS formed outside the surface showing selectivity for p-polarized incident photons (Figure b) and a 2D-free electron-like dispersive nature parallel to the surface (Figure c). , The IPS observation also guarantees the molecular uniformity from the viewpoint of electronic structures because IPS is observable only on an atomically flat surface. , …”

Section: Resultsmentioning

confidence: 76%

“…29,30 The IPS observation also guarantees the molecular uniformity from the viewpoint of electronic structures because IPS is observable only on an atomically flat surface. 31,32 At hν 1 > 4.6 eV, another peak strongly appears at E F +3.17 eV, and it is maximized at hν 1 = 4.90 eV, implying a resonance electron−hole excitation involving occupied and unoccupied states. In fact, an ultraviolet photoelectron spectrum (UPS, Figure S5) shows a peak at E F −1.7 eV assignable to the highest occupied molecular orbital (HOMO) of the anthracene moiety, 27 and therefore, it is reasonable that the peak at E F +3.17 eV appears from the resonance electron excitation from the HOMO with hν 1 = 4.90 eV (≅3.17 + 1.7 eV).…”

Section: Resultsmentioning

confidence: 99%

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Photoexcited State Confinement in Two-Dimensional Crystalline Anthracene Monolayer at Room Temperature

et al. 2017

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Organic thin film electronics place a high demand on bottom-up technology to form a two-dimensionally (2D) functional unit consisting of a single molecular crystalline layer bound to a layered structure. As the strong interaction between a substrate and molecules makes it difficult to evaluate the electronic properties of organic films, the nature of electronic excited states has not been elucidated. Here, we study a 2D crystalline anthracene monolayer electronically decoupled by alkanethiolates on a gold substrate using scanning tunneling microscopy and time-resolved two-photon photoemission spectroscopy and unravel the geometric/electronic structures and excited electron dynamics. Our data reveal that dispersive 2D excited electrons on the surface can be highly coupled with an annihilation of nondispersive excitons that facilitate electron emission with vibronic interaction. Our results provide a fundamental framework for understanding photoexcited anthracene monolayer and show how the coupling between dispersive and nondispersive excited states may assist charge separation in crystalline molecular layers.

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Section: Resultsmentioning

confidence: 76%

Section: Resultsmentioning

confidence: 99%

Photoexcited State Confinement in Two-Dimensional Crystalline Anthracene Monolayer at Room Temperature

et al. 2017

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“…alkyl chain and Au substrate) at binding energies >2 eV (Supplementary Fig. 11 ) 57 . The extended valence spectra further supports differences in the interfacial ion-pair structures as seen by the pronounced TFSI − spectral features in the binding energy range 4–12 eV (Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

Probing consequences of anion-dictated electrochemistry on the electrode/monolayer/electrolyte interfacial properties

et al. 2020

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Altering electrochemical interfaces by using electrolyte effects or so-called “electrolyte engineering” provides a versatile means to modulate the electrochemical response. However, the long-standing challenge is going “beyond cyclic voltammetry” where electrolyte effects are interrogated from the standpoint of the interfacial properties of the electrode/electrolyte interface. Here, we employ ferrocene-terminated self-assembled monolayers as a molecular probe and investigate how the anion-dictated electrochemical responses are translated in terms of the electronic and structural properties of the electrode/monolayer/electrolyte interface. We utilise a photoelectron-based spectroelectrochemical approach that is capable of capturing “snapshots” into (1) anion dependencies of the ferrocene/ferrocenium (Fc/Fc + ) redox process including ion-pairing with counter anions (Fc + –anion) caused by differences in Fc + –anion interactions and steric constraints, and (2) interfacial energetics concerning the electrostatic potential across the electrode/monolayer/electrolyte interface. Our work can be extended to provide electrolyte-related structure-property relationships in redox-active polymers and functionalised electrodes for pseudocapacitive energy storage.

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“…We also performed UPS measurements for three types of Fc-terminated SAMs possessing different electron-donating abilities and revealed a linear relation with a slope of ∼0.7 between the HOMO-related states and the formal potential determined by electrochemical measurements. , De Leo et al . and Hirata et al have reported UPS results of mixed SAMs of ferrocenylalkanethiol and n -alkanethiol, and the latter group revealed that when increasing the surface density of Fc derivatives, the binding energy of HOMO-related states is shifted to a lower value. Whereas the valence band of Fc-terminated SAMs has also been studied through density functional theory (DFT), the dependence of the electronic state on the local environment of the Fc moiety has not been studied so far.…”

Section: Introductionmentioning

confidence: 99%

“…Although these studies have provided significant insight into the electron-transfer processes of Fc-terminated SAMs, knowledge concerning electronic states of these systems, which is directly related to the electrochemical properties, is very limited. − Using ultraviolet photoelectron spectroscopy (UPS), Sikes et al investigated the energy difference between the electronic states composed of highest-occupied molecular orbital (HOMO) and its vicinities (presumably HOMO–1 and HOMO–2 states; we call these states as HOMO-related states hereafter) of the Fc moiety and the electrode Fermi level for applications in molecular electronics . We also performed UPS measurements for three types of Fc-terminated SAMs possessing different electron-donating abilities and revealed a linear relation with a slope of ∼0.7 between the HOMO-related states and the formal potential determined by electrochemical measurements. , De Leo et al .…”

Section: Introductionmentioning

confidence: 99%

Density Functional Theory Investigations of Ferrocene-Terminated Self-Assembled Monolayers: Electronic State Changes Induced by Electric Dipole Field of Coadsorbed Species

et al. 2016

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Ferrocene-terminated self-assembled monolayers (SAMs) have been widely studied in the past quarter century to reveal the electrochemical properties of chemically modified electrodes. It has been well-known that the formal potential of the system strongly depends on the local environment of the ferrocene moiety. Although electronic states of ferroceneterminated SAMs should directly affect the electrochemical properties, knowledge concerning electronic structures with respect to different local environment is very limited. In this study, we performed density functional theory calculations of ferrocene-terminated SAMs with different coadsorbed species to reveal the relationship between the electronic structures and the local environment of ferrocene moieties. Depending on the local electrostatic potential, density of states derived from the highest-occupied molecular orbital (HOMO) and its vicinities (HOMO−1 and HOMO−2) of the ferrocene moiety were found to largely shift with respect to the electrode Fermi level up to 0.75 eV. This result leads to a novel strategy for designing sophisticated chemically modified electrodes where the electronic properties are electrostatically regulated by coadsorbed inert molecules.

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Excited electron dynamics at ferrocene-terminated self-assembled monolayers on Au(111): Lengthened lifetime of image potential state

Cited by 9 publications

References 45 publications

Photoexcited State Confinement in Two-Dimensional Crystalline Anthracene Monolayer at Room Temperature

Photoexcited State Confinement in Two-Dimensional Crystalline Anthracene Monolayer at Room Temperature

Probing consequences of anion-dictated electrochemistry on the electrode/monolayer/electrolyte interfacial properties

Density Functional Theory Investigations of Ferrocene-Terminated Self-Assembled Monolayers: Electronic State Changes Induced by Electric Dipole Field of Coadsorbed Species

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