Influence of O<sub>2</sub>, H<sub>2</sub>O and airborne hydrocarbons on the properties of selected 2D materials

Peng, Zhenbo; Yang, Rui; Kim, Min A; Li, Lei; Liu, Haitao

doi:10.1039/c7ra02130e

Cited by 39 publications

(33 citation statements)

References 74 publications

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“…As such, the results in Table 1 are intuitively understood as the increase in binding energy of the anchor to graphene correlates with an increase in JFP. Sufficient binding energy of the anchor to the graphene is likely required to displace adsorbed hydrocarbons, water, and other atmospheric contaminants, [28] as well as potential geometric changes (such as rotation of the aryl groups) necessary for adsorption, but increasing the binding energy further (comparing 5 with 6)…”

Section: Statisticsmentioning

confidence: 99%

Anchor Groups for Graphene‐Porphyrin Single‐Molecule Transistors

Limburg

Thomas

Holloway

et al. 2018

Adv Funct Materials

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The effectiveness of five different anchor groups for non-covalent interfacing to graphene electrodes are compared. A family of six molecules is tested in single-molecule junctions: five consist of the same porphyrin core with different anchor groups, and the sixth is a reference molecule without anchor groups. The junction formation probability (JFP) has a strong dependence on the anchor group. Larger anchors give higher binding energies to the graphene surface, correlating with higher JFPs. The best anchor groups tested are 1,3,8-tridodecyloxypyrene and 2,5,8,11,14-pentadodecylhexa-peri-hexabenzocoronene, with JFPs of 36% and 38%, respectively. Many junctions are tested at 77 K for each molecule by measuring source-drain current as a function of bias and gate voltage. For each compound, there is wide variation in the strength of the electronic coupling to the electrodes and in the location of Coulomb peaks. In most cases, this device-to-device variability makes it impossible to observe trends between the anchor and the charge-transport characteristics. Tetrabenzofluorene anchors, which are not π-conjugated with the

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Section: Statisticsmentioning

confidence: 99%

Anchor Groups for Graphene‐Porphyrin Single‐Molecule Transistors

Limburg

Thomas

Holloway

et al. 2018

Adv Funct Materials

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“…The weak binding of the contaminant causes significant challenges in their structural characterization. Therefor, no structural information about the contaminants has been reported so far . Our assumption of using a nonpolar hydrocarbon can be justified by the fact that adsorption of hydrocarbon contaminants has been shown to promote hydrophobicity.…”

Section: Resultsmentioning

confidence: 99%

Effects of Thickness and Adsorption of Airborne Hydrocarbons on Wetting Properties of MoS₂: An Atomistic Simulation Study

2018

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Molybdenum disulfide (MoS2) has attracted great attention due to its distinctive electronic, optical, chemical, and mechanical properties. In almost all of these applications, having a clear understanding about the wetting properties of MoS2 is essential. The basal plane of MoS2 has been generally believed to be hydrophobic with water contact angle (WCA) around 90°. Kozbial et al. have recently suggested that the freshly exfoliated MoS2 was intrinsically relative hydrophilic (WCA = 69.0 ± 3.8°); however, it could become fairly hydrophobic after 1 day exposure to the ambient air (WCA = 89.0 ± 3.1°) (Understanding the Intrinsic Water Wettability of Molybdenum Disulfide (MoS2)Langmuir20153184298435). They contributed this change in wetting properties to the adsorption of airborne hydrocarbons. The number of layers is another important factor that is believed to affect the wetting properties in ultrathin MoS2 films. For highly crystalline samples grown at high temperature (900°C), Gaur et al. showed that the WCA was a function of number of layers and changed from 98° in monolayer sample to 88° in a sample with 11 layers (Surface Energy Engineering for Tunable Wettability through controlled synthesis of MoS2 Nano Lett.20141443144321). In this work, we study the effects of these two parameters, namely, adsorption of airborne hydrocarbon contaminants and the number of layers, on MoS2 wetting properties using atomistic simulations. Results of our simulations confirm that both of these factors can affect the wetting properties of MoS2 through altering van der Waals interactions between MoS2 and water. We also show that the contributions of both energy and entropy of adhesion should be considered to understand the wetting properties of MoS2. Results of this work improve our understanding about the wetting properties of MoS2 and other transition metal dichalcogenides.

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“…This type of doping is indicated by a shift of the G-peak position to high wavenumbers during Raman measurements of graphene exposed to dry O 2 , and occurs because of an electron transfer from trapped O 2 under the graphene layer. This charge transfer leads to the development of a negatively charged adsorbate layer over graphene, which should modulate its wettability 27 . Physisorbed water, both on the graphene surface and trapped under the graphene layer, amplifies the doping effect of oxygen, resulting in permanent shifts of the G-peak during Raman measurement and amplifying any observed shift in the wettability 27 .…”

Section: Intrinsic Perturbation Of the Wetting Behavior Of 2d Materialsmentioning

confidence: 99%

“…This charge transfer leads to the development of a negatively charged adsorbate layer over graphene, which should modulate its wettability 27 . Physisorbed water, both on the graphene surface and trapped under the graphene layer, amplifies the doping effect of oxygen, resulting in permanent shifts of the G-peak during Raman measurement and amplifying any observed shift in the wettability 27 . Recent studies integrating fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and static WCA measurements with DFT-predicted WCAs and DFT AFM force simulations predict the formation of ice-like water layers on top of graphene under ambient conditions ( Fig.…”

Section: Intrinsic Perturbation Of the Wetting Behavior Of 2d Materialsmentioning

confidence: 99%

Interaction of 2D materials with liquids: wettability, electrochemical properties, friction, and emerging directions

et al. 2020

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The emergence of two-dimensional (2D) materials as functional surfaces for sensing, electronics, mechanics, and other myriad applications underscores the importance of understanding 2D material-liquid interactions. The thinness and environmental sensitivity of 2D materials induce novel surface forces that drive liquid interactions. This complexity makes fundamental 2D material-liquid interactions variable. In this review, we discuss the (1) wettability, (2) electrical double layer (EDL) structure, and (3) frictional interactions originating from 2D material-liquid interactions. While many 2D materials are inherently hydrophilic, their wettability is perturbed by their substrate and contaminants, which can shift the contact angle. This modulation of the wetting behavior enables templating, filtration, and actuation. Similarly, the inherent EDL at 2D material-liquid interfaces is easily perturbed. This EDL modulation partially explains the wettability modulation and enables distinctive electrofluidic systems, including supercapacitors, energy harvesters, microfluidic sensors, and nanojunction gating devices. Furthermore, nanoconfinement of liquid molecules at 2D material surfaces arising from a perturbed liquid structure results in distinctive hydrofrictional behavior, influencing the use of 2D materials in microchannels. We expect 2D material-liquid interactions to inform future fields of study, including modulation of the chemical reactivity of 2D materials via tuning 2D material-liquid interactions. Overall, 2D material-liquid interactions are a rich area for research that enables the unique tuning of surface properties, electrical and mechanical interactions, and chemistry. Origin of 2D material interactions with liquids The ideal interaction between a surface and a liquid is dictated by surface forces. Surface forces can be subdivided into three components: van der Waals forces, which exist at any interface between solids and liquids; electrostatic interactions, which exist between charged or polar surfaces and fluids; and structural forces, principally hydrogen bonding 1. These interactions influence the wetting behavior and determine whether the interaction with water is hydrophilic or hydrophobic, control the electronic structure at the liquid-solid interface, influence the frictional interaction, and modulate the chemical activity. However, this ideal picture of the surface interactions is complicated when considering surface heterogeneities, including roughness 2 and contamination 3 , which interfere with the formation of an equilibrium configuration between the liquid and the surface, leading to eccentric behaviors, including superwetting, superslipping, and superhydrophobicity. These surface heterogeneities also allow the surface liquid interactions to be tuned, enabling an array of applications in sensing, chemical transport, and actuation. Two-dimensional (2D) materials, which are extremely thin, have unique electrical properties, and have a tendency to deform and accumulate contamination during proce...

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Influence of O₂, H₂O and airborne hydrocarbons on the properties of selected 2D materials

Abstract: Adsorption of molecules from the ambient environment significantly changes the optical, electrical, electrochemical, and tribological properties of 2D materials.

Cited by 39 publications

References 74 publications

Anchor Groups for Graphene‐Porphyrin Single‐Molecule Transistors

Anchor Groups for Graphene‐Porphyrin Single‐Molecule Transistors

Effects of Thickness and Adsorption of Airborne Hydrocarbons on Wetting Properties of MoS₂: An Atomistic Simulation Study

Interaction of 2D materials with liquids: wettability, electrochemical properties, friction, and emerging directions

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Influence of O2, H2O and airborne hydrocarbons on the properties of selected 2D materials

Abstract: Adsorption of molecules from the ambient environment significantly changes the optical, electrical, electrochemical, and tribological properties of 2D materials.

Cited by 39 publications

References 74 publications

Anchor Groups for Graphene‐Porphyrin Single‐Molecule Transistors

Anchor Groups for Graphene‐Porphyrin Single‐Molecule Transistors

Effects of Thickness and Adsorption of Airborne Hydrocarbons on Wetting Properties of MoS2: An Atomistic Simulation Study

Interaction of 2D materials with liquids: wettability, electrochemical properties, friction, and emerging directions

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Influence of O₂, H₂O and airborne hydrocarbons on the properties of selected 2D materials

Effects of Thickness and Adsorption of Airborne Hydrocarbons on Wetting Properties of MoS₂: An Atomistic Simulation Study