Decay of the Exciton in Quaterthiophene-Terminated Alkanethiolate Self-Assembled Monolayers on Au(111)

Kato, Hiroyuki; Murakami, Yoshinari; Kiriyama, Yoshiaki; Saitoh, Riyo; Ueba, Takahiro; Yamada, Takashi; Ie, Yutaka; Aso, Yoshio; Munakata, Toshiaki

doi:10.1021/acs.jpcc.5b02105

Cited by 18 publications

(50 citation statements)

References 56 publications

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“…The energy levels of both occupied and unoccupied molecular orbitals for the functional groups are reported to be very similar to those of their molecules. 14,15 In the case of Im-SAMs, as expected, the imidazole groups can interact with several types of molecules in solution, 16−18 in which the imino N in the imidazole group ligates with metalloporphyrin 17 or heme in cytochrome c 18 as metal complexes. Hence, we deduce that the imino N on Im-SAMs makes hydrogen bonds as H + acceptor sites with H +donating molecules.…”

Section: Introductionmentioning

confidence: 71%

Strong Hydrogen Bonds at the Interface between Proton-Donating and -Accepting Self-Assembled Monolayers on Au(111)

et al. 2018

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Hydrogen-bonding heterogeneous bilayers on substrates have been studied as a base for new functions of molecular adlayers by means of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRAS), and density functional theory (DFT) calculations. Here, we report the formation of the catechol-fused bis(methylthio)tetrathiafulvalene (HCat-BMT-TTF) adlayer hydrogen bonding with an imidazole-terminated alkanethiolate self-assembled monolayer (Im-SAM) on Au(111). The heterogeneous bilayer is realized by sequential two-step immersions in solutions for the individual Im-SAM and HCat-BMT-TTF adlayer formations. In the measurements by AFM, a grained HCat-BMT-TTF adlayer on Im-SAM is revealed. The coverage and the chemical states of HCat-BMT-TTF on Im-SAM are specified by XPS. On the vibrational spectrum measured by IRAS, the strong hydrogen bonds between HCat-BMT-TTF and Im-SAM are characterized by the remarkably red-shifted OH stretching mode at 3140 cm, which is much lower than that for hydrogen-bonding water (typically ∼3300 cm). The OH stretching mode frequency and the adsorption strength for the HCat-BMT-TTF molecule hydrogen bonding with imidazole groups are quantitatively examined on the basis of DFT calculations.

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Section: Introductionmentioning

confidence: 71%

Strong Hydrogen Bonds at the Interface between Proton-Donating and -Accepting Self-Assembled Monolayers on Au(111)

et al. 2018

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“…We chose T4C4 because it is known to form densely packed SAMs. 25 − 27 For comparison to previously reported mechanical studies, we used decanethiol (C10). We chose C10 specifically because the properties of SAMs of C10 have been studied extensively by CP-AFM.…”

Section: Resultsmentioning

confidence: 99%

Mechanically and Electrically Robust Self-Assembled Monolayers for Large-Area Tunneling Junctions

et al. 2017

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This paper examines the relationship between mechanical deformation and the electronic properties of self-assembled monolayers (SAMs) of the oligothiophene 4-([2,2′:5′,2″:5″,2‴-quaterthiophen]-5-yl)butane-1-thiol (T4C4) in tunneling junctions using conductive probe atomic force microscopy (CP-AFM) and eutectic Ga–In (EGaIn). We compared shifts in conductivity, transition voltages of T4C4 with increasing AFM tip loading force to alkanethiolates. While these shifts result from an increasing tilt angle from penetration of the SAM by the AFM tip for the latter, we ascribe them to distortions of the π system present in T4C4, which is more mechanically robust than alkanethiolates of comparable length; SAMs comprising T4C4 shows about five times higher Young’s modulus than alkanethiolates. Density functional theory calculations confirm that mechanical deformations shift the barrier height due to changes in the frontier orbitals caused by small rearrangements to the conformation of the quaterthiophene moiety. The mechanical robustness of T4C4 manifests as an increased tolerance to high bias in large-area EGaIn junctions suggesting that electrostatic pressure plays a significant role in the shorting of molecular junctions at high bias.

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“…Because the S 1 lifetime in an anthracene crystal is much longer (∼30 ns), the decay mechanism of S 1 in the 2D crystalline monolayer seems different from that in the bulk crystal. Generally, exciton decay when there is a thin separating insulating layer can be explained by an energy transfer to the substrate, , where the decay is accelerated for a thinner spacer layer. In fact, the S 1 lifetime is decreased to 1.7 ps in a shorter alkyl chain, Ant-C10-SAM (Figure S8).…”

Section: Resultsmentioning

confidence: 99%

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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Decay of the Exciton in Quaterthiophene-Terminated Alkanethiolate Self-Assembled Monolayers on Au(111)

Cited by 18 publications

References 56 publications

Strong Hydrogen Bonds at the Interface between Proton-Donating and -Accepting Self-Assembled Monolayers on Au(111)

Strong Hydrogen Bonds at the Interface between Proton-Donating and -Accepting Self-Assembled Monolayers on Au(111)

Mechanically and Electrically Robust Self-Assembled Monolayers for Large-Area Tunneling Junctions

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

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