Wettability of Graphene-Coated Surface: Free Energy Investigations Using Molecular Dynamics Simulation

Hung, Shih‐Wei; Hsiao, Pai‐Yi; Chen, Chien-Pin; Chieng, Ching-Chang

doi:10.1021/jp511036e

Cited by 37 publications

(30 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This result is in line with other studies that have shown graphite surfaces to be mildly hydrophilic with a contact angle of about 50ᵒ, 35,36,37 Although higher aqueous contact angle values have been reported in the literature, 38,39,40 variations are expected depending on the sample quality, measurement environment (including surface contamination which increases the contact angle) and droplet size. 35,36,41 Given the short timescale (<5 s) on which the droplet was deposited after cleavage of surface, 9 the value we report can be taken as the intrinsic CA of 1 mM NaClO4 at AM HOPG, and is in line with theoretical predictions. 11 % at +1.13 V, while the CA was reduced from 51ᵒ to 38ᵒ.…”

Section: Voltage Effect On Electrowettingsupporting

confidence: 81%

Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

2016

View full text Add to dashboard Cite

We demonstrate low-voltage electrowetting at the surface of freshly cleaved highly oriented pyrolytic graphite (HOPG). Using cyclic voltammetry (CV), electrowetting of a droplet of sodium perchlorate solution is observed at moderately positive potentials on high-quality (low step edge coverage) HOPG, leading to significant changes in contact angle and relative contact diameter that is comparable to the widely studied electrowetting on dielectric (EWOD) system, but over a much lower voltage range. The electrowetting behavior is found to be reasonably fast, reversible and repeatable for at least 20 cyclic scans (maximum tested). In contrast to classical electrowetting, e.g. EWOD, the electrowetting of the droplet on HOPG occurs with the intercalation/de-intercalation of anions between the graphene layers of graphite, driven by the applied potential, observed in the CV response, and detected by X-ray photoelectron spectroscopy. The electrowetting behavior is strongly influenced by those factors that affect the extent of the intercalation/de-intercalation of ions on graphite, such as scan rate, potential polarity, quality of the HOPG substrate (step edge and step height), and type of anion in the solution. In addition to perchlorate, sulfate salts also promote electrowetting, but some other salts do not. Our findings suggest a new mechanism for electrowetting based on ion intercalation and the results are of importance to fundamental 2 electrochemistry, as well as diversifying the means by which electrowetting can be controlled and applied.3

show abstract

Section: Voltage Effect On Electrowettingsupporting

confidence: 81%

Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

2016

View full text Add to dashboard Cite

show abstract

“…The effect of monolayer graphene on the contact angle compared to the underlying substrate can usually be ignored because it is transparent to wetting effects in most cases 8 . Note that modelling by Hung et al 9 shows that graphene screens substrate effects and has a larger contribution. Our measurements predominantly agree with conclusions made by Rafiee et al 8 as we measure graphene having no discernible affect on measured contact angle compared to the bare treated substrate, see Fig.…”

Section: Resultsmentioning

confidence: 97%

Correlation of p-doping in CVD Graphene with Substrate Surface Charges

Goniszewski

Adabi

Shaforost

et al. 2016

Sci Rep

View full text Add to dashboard Cite

Correlations between the level of p-doping exhibited in large area chemical vapour deposition (CVD) graphene field effect transistor structures (gFETs) and residual charges created by a variety of surface treatments to the silicon dioxide (SiO2) substrates prior to CVD graphene transfer are measured. Beginning with graphene on untreated thermal oxidised silicon, a minimum conductivity (σmin) occurring at gate voltage Vg = 15 V (Dirac Point) is measured. It was found that more aggressive treatments (O2 plasma and UV Ozone treatments) further increase the gate voltage of the Dirac point up to 65 V, corresponding to a significant increase of the level of p-doping displayed in the graphene. An electrowetting model describing the measured relationship between the contact angle (θ) of a water droplet applied to the treated substrate/graphene surface and an effective gate voltage from a surface charge density is proposed to describe biasing of Vg at σmin and was found to fit the measurements with multiplication of a correction factor, allowing effective non-destructive approximation of substrate added charge carrier density using contact angle measurements.

show abstract

“…These observations are consistent with recent theoretical predictions. 61 The meniscus detached at position 7, and the iDC (meniscus confined to the pipet) decreased suddenly to its original value. and Cu-supported CVD graphene with the same, and similar, redox species.…”

Section: Wetting and Electrochemistry Of Supported And Suspended Grapmentioning

confidence: 98%

“…Yet, the relatively few studies available are not in agreement, especially on the effect of the substrate. 29,60,61 To the best of our knowledge, the intrinsic wettability of suspended graphene has only been predicted theoretically by molecular dynamics, 62 and has not been measured, due to experimental challenges. Our studies suggest that Cu-supported graphene exhibits stronger wettability compared with a free-standing graphene sheet.…”

Section: Wetting and Electrochemistry Of Supported And Suspended Grapmentioning

confidence: 99%

Versatile Polymer-Free Graphene Transfer Method and Applications

Zhang

Güell

Kirkman

et al. 2016

ACS Appl. Mater. Interfaces

107

View full text Add to dashboard Cite

A new method for transferring chemical vapor deposition (CVD)-grown monolayer graphene, to a variety of substrates is described. The method makes use of an organic/aqueous biphasic configuration, avoiding the use of any polymeric materials that can cause severe contamination problems. The graphene-coated copper foil sample (on which graphene was grown) sits at the interface between hexane and an aqueous etching solution of ammonium persulfate to remove the copper. With the aid of an Si/SiO2 substrate, the graphene layer is then transferred to a second hexane/water interface, to remove etching products. From this new location, CVD graphene is readily transferred to arbitrary substrates, including three dimensional architectures as represented by atomic force microscopy (AFM) tips and transmission electron microscopy (TEM) grids. Graphene produces a conformal layer on AFM tips, to the very end, allowing the easy production of tips for conductive AFM imaging. Graphene transferred to copper TEM grids provides large area, highly electrontransparent substrates for TEM imaging. These substrates can also be used as working electrodes for electrochemistry and high resolution wetting studies. By using scanning electrochemical cell microscopy, it is possible to make electrochemical and wetting measurements at either a free-standing graphene film or a copper-supported graphene area, and readily determine any differences in behavior.3

show abstract

Wettability of Graphene-Coated Surface: Free Energy Investigations Using Molecular Dynamics Simulation

Cited by 37 publications

References 53 publications

Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

Correlation of p-doping in CVD Graphene with Substrate Surface Charges

Versatile Polymer-Free Graphene Transfer Method and Applications

Contact Info

Product

Resources

About