Imaging the reactivity and width of graphene's boundary region

AlSalem, Huda S.; Al‐Goul, Soha T.; Ferrari, Alejandro García‐Miranda; Brownson, Dale A. C.; Velarde, Luis; Koehler, Sven P. K.

doi:10.1039/d0cc02675a

Cited by 4 publications

(2 citation statements)

References 38 publications

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“…In contrast, highly reactive molecules can form supramolecular bonds anywhere on graphene. However, due to the termination of π-electron cloud (dangling bonds), edges are more vulnerable to external perturbations such as hydrogenation or oxide formation via molecular attachment, etc. , Furthermore, the low dipole moment of toluene, chlorobenzene, and THF molecules is responsible for not affecting the graphene’s electron cloud anywhere on graphene. Further technical details of this aspect will be discussed in later sections.…”

Section: Resultsmentioning

confidence: 99%

Revealing the Microscopic Picture of the Charge Transfer Mechanism between Graphene and Dopant Molecules

Khandelwal,

Srivastava,

Nagaraja

et al. 2023

J. Phys. Chem. C

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It is generally recognized that the dipole moment of the adsorbed molecules is a crucial factor in determining the chargetransfer interaction between molecules and graphene. However, the microscopic details of this process have remained elusive. In this study, we experimentally investigate the charge-transfer interaction between adsorbed molecules and graphene, which holds great promise for achieving controllable doping. By trapping various molecules at the graphene−substrate interface, our results emphasize that the doping effect primarily depends on the reactivity of the constituent atoms in the attached molecules rather than just their dipole moment. Observation of (i) the emergence of the Raman D peak exclusively at the edges for trapped molecules without reactive atoms, and throughout the entire basal plane for those with reactive atoms, and (ii) variations in the density of attached molecules (with and without reactive atoms) to graphene with their respective dipole moments provides compelling evidence to support our claim. These findings are well-supported by experimental results and first-principles density functional theory calculations.

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Section: Resultsmentioning

confidence: 99%

Revealing the Microscopic Picture of the Charge Transfer Mechanism between Graphene and Dopant Molecules

Khandelwal,

Srivastava,

Nagaraja

et al. 2023

J. Phys. Chem. C

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“…We have previously validated the value of the nonlinear laser spectroscopy technique of vibrational sum-frequency generation (vSFG) for the study of (modified) graphene . Due to the inversion symmetry in (most) media, vSFG is forbidden in the bulk, but this symmetry is broken at an interface. , Since graphene inherently is an interface and inversion symmetry is broken for supported graphene, vSFG is ideally suited to explore the chemistry and physics occurring on graphene .…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Vibrational Dephasing Times of Modified Graphene

AlSalem

Koehler

2022

J. Phys. Chem. C

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We have measured the ultrafast dephasing times of vibrational quanta in functional groups covalently bound to graphene. It has been previously shown that electronic relaxation in graphene occurs on subpicosecond timescales, but this is the first venture into the vibrational dephasing times in functionalized graphene. We have employed time-resolved sum-frequency generation spectroscopy to observe the decay of the coherent signal arising due to vibrational excitation by delaying the upconversion pulse with respect to the infrared (IR) laser pulse. We observe decay times of 0.8 and 1.4 ps for vibrational stretches in phenyl groups attached to graphene or gold, respectively, but for the vibrations of the bond covalently connecting H atoms to graphene in hydrogenated graphene, we measure much faster decay times of 0.3 ps. This is likely due to coupling between the C−H stretch and either the two-dimensional (2D) mode of graphene or nonadiabatic coupling to electrons photoexcited by the upconversion laser pulse.

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Surface-Confined Biomolecules for Application in Bioelectronics

Iost

2022

Advances in Bioelectrochemistry Volume 1

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Imaging the reactivity and width of graphene's boundary region

Abstract: The reactivity of graphene at its basal plane versus its boundary region has been imaged using surface-selective non-linear vibrational spectroscopy in order to address the long-standing controversy as to whether...

Cited by 4 publications

References 38 publications

Revealing the Microscopic Picture of the Charge Transfer Mechanism between Graphene and Dopant Molecules

Revealing the Microscopic Picture of the Charge Transfer Mechanism between Graphene and Dopant Molecules

Ultrafast Vibrational Dephasing Times of Modified Graphene

Surface-Confined Biomolecules for Application in Bioelectronics

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