Electron Transfer Kinetics on Mono- and Multilayer Graphene
- Matěj Velický ,
- Dan F. Bradley ,
- Adam J. Cooper ,
- Ernie W. Hill ,
- Ian A. Kinloch ,
- Artem Mishchenko ,
- Konstantin S. Novoselov ,
- Hollie V. Patten ,
- Peter S. Toth ,
- Anna T. Valota ,
- Stephen D. Worrall , and
- Robert A. W. Dryfe
Abstract

Understanding of the electrochemical properties of graphene, especially the electron transfer kinetics of a redox reaction between the graphene surface and a molecule, in comparison to graphite or other carbon-based materials, is essential for its potential in energy conversion and storage to be realized. Here we use voltammetric determination of the electron transfer rate for three redox mediators, ferricyanide, hexaammineruthenium, and hexachloroiridate (Fe(CN)63–, Ru(NH3)63+, and IrCl62–, respectively), to measure the reactivity of graphene samples prepared by mechanical exfoliation of natural graphite. Electron transfer rates are measured for varied number of graphene layers (1 to ca. 1000 layers) using microscopic droplets. The basal planes of mono- and multilayer graphene, supported on an insulating Si/SiO2 substrate, exhibit significant electron transfer activity and changes in kinetics are observed for all three mediators. No significant trend in kinetics with flake thickness is discernible for each mediator; however, a large variation in kinetics is observed across the basal plane of the same flakes, indicating that local surface conditions affect the electrochemical performance. This is confirmed by in situ graphite exfoliation, which reveals significant deterioration of initially, near-reversible kinetics for Ru(NH3)63+ when comparing the atmosphere-aged and freshly exfoliated graphite surfaces.
Figure 1

Figure 1. Experimental setup. (a) Photograph of the experimental setup. (b) Schematic depicting the Si/SiO2 wafer with mechanically exfoliated flakes (working electrode, WE) contacted via silver epoxy and copper wire, microscope objective and a micropipette, which contains reference (RE) and counter electrodes (CE) and is connected to a micromanipulator and microinjector. (c) An optical micrograph of a droplet deposited on the surface of a monolayer graphene flake. The dashed lines and curves indicate edge planes (black), steps (white), cracks/defects (orange), folds (green), and microdroplet/flake interface (blue).
Results and Discussion
Cyclic Voltammetry on Basal Plane Graphene/Graphite
where ψ is the dimensionless kinetic parameter determined from ΔEp, α is the transfer coefficient, n is the number of electrons transferred, F is the Faraday constant, and R and T have their usual meanings. In most cases, it can be assumed that the diffusion coefficients of the oxidized and reduced form (DO and DR, respectively) of the mediator are approximately equal and the reduction/oxidation kinetics are fairly symmetrical (α ∼ 0.5). In that case, ΔEp depends solely on ψ (one-electron processes), (31) the latter is determined from ΔEp, and eq 1 can be simplified to
In practice, ψ is calculated from ΔEp using an appropriate working function and k0 determined from the slope of the ψ–ν–0.5 dependence corresponding to eq 2 as shown in Figure 2e.Figure 2

Figure 2. Cyclic voltammograms and associated kinetic analyses at graphene/graphite electrodes. (a) CV of Fe(CN)63–/4– on bilayer graphene, (b and d) show comparison of ET kinetics on 4-layer graphene using Ru(NH3)63+/2+ and on ∼70-layer thick graphite using IrCl62–/3–. Corresponding Klingler-Kochi and Nicholson analyses and calculated ET rates (k0) are shown in (c) and (e), respectively. The insets in the bottom right of graphs (a), (b), and (d) show micrographs of the deposited droplets. The series of voltammetric curves were obtained starting from the fastest scan rate of 1000 mV s–1 (dark blue) down to the slowest scan rate of 100 mV s–1 (gray) for Fe(CN)63–/4– and Ru(NH3)63+/2+ and 3000–250 mV s–1 for IrCl62–/3–. The potential was referenced against Ag/AgCl wire in 6 M LiCl, and held at the upper vertex potential for 10 s prior to the voltammetry (1 V for IrCl62–/3–). Change of the initial direction of the potential sweep had no observable effect.
As in the case of Nicholson analysis, it was assumed that the reduction and oxidation are symmetrical, i.e., α ≈ 0.5. The method was also validated by finite-element simulation of the voltammograms (Figure S4, Supporting Information).
where A is the area of the flake surface in contact with the liquid and c is the bulk concentration of the mediator. Although eq 4 has been widely used by researchers to determine diffusion coefficients during ET rate measurements, it is only strictly valid for reversible electrochemical reactions, i.e., where ET kinetics are significantly faster than mass-transport. The peak current in quasi-reversible reactions, as is the case here, is no longer proportional to ν1/2 and instead more complex analysis is required to describe the peak current, with the quasi-reversible reaction zone corresponding to ΔEp of ∼62/n to 1000/n mV. (34) We also found that the linear ψ–ν–0.5 dependence breaks down when the droplet is significantly smaller than 20 μm in diameter and/or the scan rate is decreased below 100 mV s–1, most likely due to a deviation from the ideal semi-infinite linear diffusion regime within small droplets. Hence, the applied scan rate was kept between the limits of 100 and 1000 mV s–1, or 250 and 3000 mV s–1, corresponding to typical ΔEp ranges of 200–600 and 300–900 mV, or 60–250 mV, for Fe(CN)63– and Ru(NH3)63+, or IrCl62–, respectively. For these reasons, diffusion coefficients of the redox mediators in 6 M LiCl (aq.) were determined independently, using a platinum disk macro-electrode with well-defined reversible ET behavior, as 1.84 (±0.19) × 10–6 cm2 s–1, 2.36 (±0.11) × 10–6 cm2 s–1, 2.27 (±0.14) × 10–6 cm2 s–1 for Fe(CN)63–, Ru(NH3)63+ and IrCl62–, respectively (full details of analysis in Supporting Information).Dependence of Electron Transfer Kinetics on the Number of Graphene Layers
Figure 3

Figure 3. Heterogeneous ET rate, k0, between the aqueous-based redox mediator and mechanically exfoliated graphite flakes of varied thicknesses. The averaged ET rates of reduction/oxidation of (a) Fe(CN)63–/4–, (b) Ru(NH3)63+/2+ and IrCl62–/3– reduction/oxidation are plotted as a function of the number of graphene layers. Each point on the graph is an arithmetic mean of at least 8 (thick flakes >7 layers) or 12 (thin flakes ≤7 layers) individual droplet measurements on a pristine basal plane surface of one or more flakes of a given thickness. The error bars are standard deviations of the mean. The number of individual droplets included in the analysis was 145, 146, and 144 for Fe(CN)63–/4–, Ru(NH3)63+/2+, and IrCl62–/3–, respectively. In total, 69 individual crystal surfaces were used for the analysis. Note that the graphs are shown on a semilogarithmic scale.
| Fe(CN)63–/4– | Ru(NH3)63+/2+ | IrCl62–/3– | ||||
|---|---|---|---|---|---|---|
| no. of layers | k0/10–3 cm s–1 | Δ/k0 | k0/10–4 cm s–1 | Δ/k0 | k0/10–2 cm s–2 | Δ/k0 |
| 1 | 0.15 ± 0.02 | 0.12 | 0.31 ± 0.10 | 0.31 | 3.48 ± 0.47 | 0.13 |
| 2 | 0.13 ± 0.02 | 0.16 | 1.02 ± 0.12 | 0.12 | 4.91 ± 0.58 | 0.12 |
| 3 | 0.93 ± 0.35 | 0.38 | 0.52 ± 0.12 | 0.23 | 3.15 ± 0.48 | 0.15 |
| 4 | 0.57 ± 0.13 | 0.22 | 0.36 ± 0.09 | 0.24 | 3.07 ± 0.22 | 0.07 |
| 5 | 0.23 ± 0.05 | 0.23 | 0.52 ± 0.09 | 0.17 | 2.87 ± 0.19 | 0.07 |
| 6 | 0.46 ± 0.11 | 0.25 | 1.14 ± 0.12 | 0.10 | 2.93 ± 0.17 | 0.06 |
| 7 | 2.09 ± 1.27 | 0.61 | 1.55 ± 0.14 | 0.09 | 4.08 ± 0.47 | 0.11 |
| 8–9 | – | – | 0.95 ± 0.25 | 0.27 | 2.14 ± 0.32 | 0.15 |
| 11–13 | 2.07 ± 0.83 | 0.40 | 0.15 ± 0.05 | 0.34 | 3.16 ± 0.20 | 0.06 |
| 20–30 | 1.97 ± 0.98 | 0.50 | 0.11 ± 0.06 | 0.59 | 3.40 ± 0.11 | 0.03 |
| 50–60 | 0.68 ± 0.17 | 0.25 | 0.22 ± 0.10 | 0.47 | 3.11 ± 0.17 | 0.05 |
| 80–90 | 0.24 ± 0.12 | 0.51 | 0.28 ± 0.08 | 0.29 | 2.73 ± 0.22 | 0.08 |
| 100–130 | 1.22 ± 0.16 | 0.13 | 0.36 ± 0.03 | 0.09 | 3.20 ± 0.15 | 0.05 |
| 220–250 | 0.84 ± 0.17 | 0.20 | 0.17 ± 0.03 | 0.16 | 2.87 ± 0.12 | 0.04 |
| 300–500 | 1.33 ± 0.49 | 0.37 | 0.45 ± 0.08 | 0.19 | 3.30 ± 0.15 | 0.05 |
| >1000 | 0.78 ± 0.18 | 0.23 | 0.23 ± 0.07 | 0.31 | 2.25 ± 0.15 | 0.07 |
| mean | 0.90 ± 0.13 | 0.30 | 0.53 ± 0.04 | 0.25 | 3.13 ± 0.10 | 0.08 |
| cleaved | – | – | 47.3 ± 3.9 | 0.08 | – | – |
The errors are standard deviations of 8 or more measurements at various locations on flakes of the same thickness. The number of graphene layers was determined using a combination of optical microscopy, Raman spectroscopy and atomic force microscopy (AFM) as described in the Methods. The variation of the ET kinetics on flakes of the same thickness is reflected in the relative error, Δ/k0. Arithmetic means and their standard deviations are also listed at the bottom of table.
Surface Sensitivity to Contaminants
Figure 4

Figure 4. XPS survey spectra of atmosphere-aged (>1 month) graphite surface (top green) and pristine graphite surface cleaved immediately prior the XPS measurement (bottom red). Both spectra show data averaged from 5 different sites on the surface (spot size of 400 μm2). The quantitative elemental analysis is given in Table 2.
| surface site variation/At% | mean/At% | |||
|---|---|---|---|---|
| element | aged | cleaved | aged | cleaved |
| C | 88.54–94.08 | 85.76–97.42 | 92.84 | 93.17 |
| N | 0.09–0.56 | 0.00–0.33 | 0.37 | 0.12 |
| O | 4.31–8.06 | 1.35–12.10 | 4.98 | 4.39 |
| F | 0.23–1.55 | 0.45–1.87 | 0.78 | 1.09 |
| Na | <0.01 | 0.01–0.51 | 0.01 | 0.08 |
| Al | 0.07–0.49 | 0.01–0.79 | 0.16 | 0.34 |
| Si | 0.39–1.60 | 0.51–1.51 | 0.65 | 0.72 |
| S | 0.14–0.24 | 0.00–0.10 | 0.14 | 0.03 |
| K | 0.00–0.13 | 0.00–0.10 | 0.04 | 0.04 |
| Ca | 0.00–1.64 | <0.01 | 0.03 | 0.00 |
| Fe | <0.01 | <0.01 | 0.00 | 0.00 |
| Ni | 0.00–0.01 | 0.00–0.06 | 0.01 | 0.03 |
Figure 5

Figure 5. Effect of impurities on hybridization and functionalization of carbon atoms expressed by XPS analysis of both atmosphere-aged (circles) and cleaved (triangles) graphite surface. The extent of carbon sp2 hybridization, determined from C 1s peak (green) and Auger peak (D-parameter, blue), is proportional to the total carbon content (XPS survey quantification).
Comparison of the Kinetics for Fe(CN)63–/4–, Ru(NH3)63+/2+, and IrCl62–/3–
Figure 6

Figure 6. (a) Cyclic voltammograms recorded on natural graphite (solid curve), HOPG (dashed curve), platinum (dotted curve), and gold (dash-dot curve), and (b) corresponding ET kinetics obtained as an arithmetic mean of three independent measurements. Data in red and gray correspond to aged and cleaved surfaces, respectively. Mechanically polished metal surfaces exhibited almost reversible kinetics (>10–2 cm s–1) with peak separation below 65 mV at 1 V s–1.
Conclusions
Methods
Chemicals
Experimental Setup
where X is K3Fe(CN)6, Ru(NH3)6Cl3, or (NH4)2IrCl6. The reference electrode potential (Ag/AgCl, 6 M LiCl) of +193 mV vs SHE was determined from the Nernst equation and thermodynamic data (eqs S1–S3, Supporting Information). The high concentration of the electrolyte was used to prevent evaporation of the droplet. Dispensing and aspiration of the liquid from/into the micropipette was controlled via a microinjector (PV820 Pneumatic PicoPump, WPI, Worcester, MA) and argon gas (99.998%, BOC Industrial Gases, U.K.). The diameter of the deposited droplet (typically 20–50 μm in diameter, 2–30 pL volume) was controlled via combination of pressure and deposition time. The micropipette and the liquid was changed every 6–10th droplet deposition. A micrograph in Figure 1c shows a microdroplet deposited on a basal plane surface of a graphene monolayer. The droplet/graphene interfacial area was determined using either GXCapture 7.3 software (GT Vision Ltd., U.K.) or NIS Elements (D) software (Nikon Metrology, UK Ltd.). The experiments were carried out at ambient temperature (25–29 °C), which was recorded and accounted for in k0 calculations.Flake Preparation
Flake Characterization
Figure 7

Figure 7. (a) Raman spectra of the mono-, bi-, tri-, tetra/penta-, and multilayer graphene flakes, bottom to top, respectively (each spectrum is shown on a different intensity scale for the purpose of clarity). (b) 3D and 2D AFM scans (top and bottom-left, respectively) of a ca. 4/5-layer thick graphene flake with another monolayer on top, inset (bottom-right) shows the optical image of the scanned area, (c) cross-section of the same flake, indicated by green lines in (b).
Supporting Information
Micropipette preparation, reference electrode potential determination, Nicholson method, cyclic voltammetry fitting, mediator-free blank voltammetry, AFM of the stable and collapsed microdroplets, flake preparation procedure, determination of the redox mediator diffusion coefficients, kinetics-droplet size correlation, comparison of the raw and analyzed kinetic data, uncompensated resistance, comparison of electrode kinetics on basal and edge plane of graphite, and X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) analysis of atmosphere-aged and freshly cleaved graphite surface. This material is available free of charge via the Internet at http://pubs.acs.org.
Terms & Conditions
Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.
Acknowledgment
The authors thank EPSRC (grant references: EP/I005145/1, EP/K039547/1 and EP/K016954/1) for financial support. The authors also thank Dr. Anders Barlow at nanoLAB (Newcastle University) for XPS measurement, and Greg Auton, Sheng Hu and Huafeng Yang, all from Manchester University, for their help with sample preparation and characterization.
References
This article references 53 other publications.
- 1Mayorov, A. S.; Gorbachev, R. V.; Morozov, S. V.; Britnell, L.; Jalil, R.; Ponomarenko, L. A.; Blake, P.; Novoselov, K. S.; Watanabe, K.; Taniguchi, T.et al. Micrometer-Scale Ballistic Transport in Encapsulated Graphene at Room Temperature Nano Lett. 2011, 11, 2396– 2399[ACS Full Text
], [CAS], Google Scholar1https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXmtFSitr4%253D&md5=fe2d8b4f0479b5e28a3c60b02d46bb23Micrometer-scale ballistic transport in encapsulated graphene at room temperatureMayorov, Alexander S.; Gorbachev, Roman V.; Morozov, Sergey V.; Britnell, Liam; Jalil, Rashid; Ponomarenko, Leonid A.; Blake, Peter; Novoselov, Kostya S.; Watanabe, Kenji; Taniguchi, Takashi; Geim, A. K.Nano Letters (2011), 11 (6), 2396-2399CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Devices made from graphene encapsulated in hexagonal BN exhibit pronounced neg. bend resistance and an anomalous Hall effect, which are a direct consequence of room-temp. ballistic transport at a micrometer scale for a wide range of carrier concns. The encapsulation makes graphene practically insusceptible to the ambient atm. and, simultaneously, allows the use of BN as an ultrathin top gate dielec. - 2Balandin, A. A. Thermal Properties of Graphene and Nanostructured Carbon Materials Nat. Mater. 2011, 10, 569– 581[Crossref], [PubMed], [CAS], Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXpt1arur4%253D&md5=c421c612c38341eb8688df9055be32a9Thermal properties of graphene and nanostructured carbon materialsBalandin, Alexander A.Nature Materials (2011), 10 (8), 569-581CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)A review. Recent years have seen a rapid growth of interest by the scientific and engineering communities in the thermal properties of materials. Heat removal has become a crucial issue for continuing progress in the electronic industry, and thermal conduction in low-dimensional structures has revealed truly intriguing features. C allotropes and their derivs. occupy a unique place in terms of their ability to conduct heat. The room-temp. thermal cond. of C materials span an extraordinary large range, of over 5 orders of magnitude, from the lowest in amorphous carbons to the highest in graphene and C nanotubes. Here, I review the thermal properties of C materials focusing on recent results for graphene, C nanotubes, and nanostructured C materials with different degrees of disorder. Special attention is given to the unusual size dependence of heat conduction in 2D crystals and, specifically, in graphene. I also describe the prospects of applications of graphene and C materials for thermal management of electronics.
- 3Lee, C.; Wei, X.; Kysar, J. W.; Hone, J. Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene Science 2008, 321, 385– 388[Crossref], [PubMed], [CAS], Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXosVOrs7k%253D&md5=c85babfb5827a1ce93f7e9673a4c8b86Measurement of the Elastic Properties and Intrinsic Strength of Monolayer GrapheneLee, Changgu; Wei, Xiaoding; Kysar, Jeffrey W.; Hone, JamesScience (Washington, DC, United States) (2008), 321 (5887), 385-388CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an at. force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per m (N m-1) and -690 N m-1, resp. The breaking strength is 42 N m-1 and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of σint = 130 gigapascals for bulk graphite. These expts. establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mech. tested to deformations well beyond the linear regime.
- 4Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A. Electric Field in Atomically Thin Carbon Films Science 2004, 306, 666– 669[Crossref], [PubMed], [CAS], Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXos1Kqt70%253D&md5=488da13500bf24e8fc419052dc1a9e84Electric Field Effect in Atomically Thin Carbon FilmsNovoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A.Science (Washington, DC, United States) (2004), 306 (5696), 666-669CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The authors describe monocryst. graphitic films, which are a few atoms thick but are nonetheless stable under ambient conditions, metallic, and of remarkably high quality. The films are a two-dimensional semimetal with a tiny overlap between valence and conductance bands, and they exhibit a strong ambipolar elec. field effect such that electrons and holes in concns. up to 1013 per square centimeter and with room-temp. mobilities of ∼10,000 square centimeters per V-second can be induced by applying gate voltage.
- 5Geim, A. K. Graphene: Status and Prospects Science 2009, 324, 1530– 1534[Crossref], [PubMed], [CAS], Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXnsFOrsLk%253D&md5=246440adb8c23a1d5ff923d1d80ff920Graphene: Status and ProspectsGeim, A. K.Science (Washington, DC, United States) (2009), 324 (5934), 1530-1534CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A review. Graphene is a wonder material with many superlatives to its name. It is the thinnest known material in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic mobility, have zero effective mass, and can travel for micrometers without scattering at room temp. Graphene can sustain current densities six orders of magnitude higher than that of copper, shows record thermal cond. and stiffness, is impermeable to gases, and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation, which allows the investigation of relativistic quantum phenomena in a benchtop expt. This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.
- 6Novoselov, K. S.; Fal’Ko, V. I.; Colombo, L.; Gellert, P. R.; Schwab, M. G.; Kim, K. A Roadmap for Graphene Nature 2012, 490, 192– 200[Crossref], [PubMed], [CAS], Google Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsVyrsrrO&md5=39fd29cc6d8a772bfa811f57bc142fd7A roadmap for grapheneNovoselov, K. S.; Fal'ko, V. I.; Colombo, L.; Gellert, P. R.; Schwab, M. G.; Kim, K.Nature (London, United Kingdom) (2012), 490 (7419), 192-200CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)A review. Recent years have witnessed many breakthroughs in research on graphene (the first 2D at. crystal) as well as a significant advance in the mass prodn. of this material. This one-atom-thick fabric of C uniquely combines extreme mech. strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of prodn. methods, and critically analyze the feasibility of various graphene applications.
- 7Nair, R. R.; Blake, P.; Grigorenko, A. N.; Novoselov, K. S.; Booth, T. J.; Stauber, T.; Peres, N. M. R.; Geim, A. K. Fine Structure Constant Defines Visual Transparency of Graphene Science 2008, 320, 1308[Crossref], [PubMed], [CAS], Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXmslWgt7k%253D&md5=e99cdff43e2bef193cf9767c6619b4daFine Structure Constant Defines Visual Transparency of GrapheneNair, R. R.; Blake, P.; Grigorenko, A. N.; Novoselov, K. S.; Booth, T. J.; Stauber, T.; Peres, N. M. R.; Geim, A. K.Science (Washington, DC, United States) (2008), 320 (5881), 1308CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)There is a small group of phenomena in condensed matter physics that is defined only by the fundamental consts. and does not depend on material parameters. Examples are the resistivity quantum, h/e2 (h is Planck's const. and e the electron charge), that appears in a variety of transport expts. and the magnetic flux quantum, h/e, playing an important role in the physics of supercond. By and large, sophisticated facilities and special measurement conditions are required to observe any of these phenomena. We show that the opacity of suspended graphene is defined solely by the fine structure const., α = e2/ℏc ≈ 1/137 (where c is the speed of light), the parameter that describes coupling between light and relativistic electrons and that is traditionally assocd. with quantum electrodynamics rather than materials science. Despite being only one atom thick, graphene is found to absorb a significant (πα = 2.3%) fraction of incident white light, a consequence of graphene's unique electronic structure.
- 8Moser, J.; Barreiro, A.; Bachtold, A. Current-Induced Cleaning of Graphene Appl. Phys. Lett. 2007, 91Google ScholarThere is no corresponding record for this reference.
- 9Topsakal, M.; Aahin, H.; Ciraci, S. Graphene Coatings: An Efficient Protection from Oxidation Phys. Rev. B: Condens. Matter Mater. Phys. 2012, 85Google ScholarThere is no corresponding record for this reference.
- 10Wang, Y.; Li, Z.; Wang, J.; Li, J.; Lin, Y. Graphene and Graphene Oxide: Biofunctionalization and Applications in Biotechnology Trends Biotechnol. 2011, 29, 205– 212[Crossref], [PubMed], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXltFegtrY%253D&md5=4f02be84ecfa6dbc1cd617f8bab2f76fGraphene and graphene oxide: biofunctionalization and applications in biotechnologyWang, Ying; Li, Zhaohui; Wang, Jun; Li, Jinghong; Lin, YueheTrends in Biotechnology (2011), 29 (5), 205-212CODEN: TRBIDM; ISSN:0167-7799. (Elsevier B.V.)A review. Graphene is the basic building block of 0D fullerene, 1D carbon nanotubes, and 3D graphite. Graphene has a unique planar structure, as well as novel electronic properties, which have attracted great interests from scientists. This review selectively analyzes current advances in the field of graphene bioapplications. In particular, the biofunctionalization of graphene for biol. applications, fluorescence-resonance-energy-transfer-based biosensor development by graphene or graphene-based nanomaterials, and the investigation of graphene or graphene-based nanomaterials for living cell studies are summarized in more detail. Future perspectives and possible challenges in this rapidly developing area are also discussed.
- 11Lee, J. K.; Smith, K. B.; Hayner, C. M.; Kung, H. H. Silicon Nanoparticles-Graphene Paper Composites for Li Ion Battery Anodes Chem. Commun. (Cambridge, U.K.) 2010, 46, 2025– 2027[Crossref], [PubMed], [CAS], Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXjtVSnsrw%253D&md5=627b7dfbe71bdbbbde0dd9da672b4fb7Silicon nanoparticles-graphene paper composites for Li ion battery anodesLee, Jeong K.; Smith, Kurt B.; Hayner, Cary M.; Kung, Harold H.Chemical Communications (Cambridge, United Kingdom) (2010), 46 (12), 2025-2027CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)Composites of Si nanoparticles highly dispersed between graphene sheets, and supported by a three-dimensional network of graphite formed by reconstituting regions of graphene stacks exhibit high Li ion storage capacities and cycling stability. An electrode was prepd. with a storage capacity >2200 mA-h/g after 50 cycles and >1500 mA-h/g after 200 cycles that decreased by <0.5% per cycle.
- 12Wang, X.; Zhi, L.; Müllen, K. Transparent, Conductive Graphene Electrodes for Dye-Sensitized Solar Cells Nano Lett. 2008, 8, 323– 327[ACS Full Text
], [CAS], Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhsVejtbnK&md5=75dbbd7c51272355e9ca50a75e9de3acTransparent, Conductive Graphene Electrodes for Dye-Sensitized Solar CellsWang, Xuan; Zhi, Linjie; Muellen, KlausNano Letters (2008), 8 (1), 323-327CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)A transparent, conductive and ultrathin graphene film is an alternative to a metal oxide window electrode for solid-state dye-sensitized solar cells. The graphene films are fabricated from exfoliated graphite oxide, followed by thermal redn. These films exhibit a high cond. of 550 S/cm and a transparency of >70% over 1000-3000 nm. They also have good chem. and thermal stabilities as well as an ultra-smooth surface with tunable wettability. - 13Stoller, M. D.; Park, S.; Yanwu, Z.; An, J.; Ruoff, R. S. Graphene-Based Ultracapacitors Nano Lett. 2008, 8, 3498– 3502[ACS Full Text
], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtFaitLjE&md5=935ad6b5a3e3685d1907eb62d1fd5ad6Graphene-Based UltracapacitorsStoller, Meryl D.; Park, Sungjin; Zhu, Yanwu; An, Jinho; Ruoff, Rodney S.Nano Letters (2008), 8 (10), 3498-3502CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)The surface area of a single graphene sheet is 2630 m2/g, substantially higher than values derived from BET surface area measurements of activated carbons used in current electrochem. double layer capacitors. The authors' group has pioneered a new carbon material that the authors call chem. modified graphene (CMG). CMG materials are made from 1-atom thick sheets of carbon, functionalized as needed, and here the authors demonstrate in an ultracapacitor cell their performance. Specific capacitances of 135 and 99 F/g in aq. and org. electrolytes, resp., were measured. High elec. cond. gives these materials consistently good performance over a wide range of voltage scan rates. These encouraging results illustrate the exciting potential for high performance, elec. energy storage devices based on this new class of carbon material. - 14Brownson, D. A. C.; Kampouris, D. K.; Banks, C. E. Graphene Electrochemistry: Fundamental Concepts through to Prominent Applications Chem. Soc. Rev. 2012, 41, 6944– 6976[Crossref], [PubMed], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsVOnurfN&md5=7d643e49014b33d7dc63736ae2424df2Graphene electrochemistry: fundamental concepts through to prominent applicationsBrownson, Dale A. C.; Kampouris, Dimitrios K.; Banks, Craig E.Chemical Society Reviews (2012), 41 (21), 6944-6976CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. The use of graphene, a one atom thick individual planar carbon layer, has exploded in a plethora of scientific disciplines since it was reported to possess a range of unique and exclusive properties. Despite graphene being explored theor. since the 1940s and known to exist since the 1960s, the recent burst of interest from a large proportion of scientists globally can be correlated with work by Geim and Novoselov in 2004/5, who reported the so-called "scotch tape method" for the prodn. of graphene in addn. to identifying its unique electronic properties which has escalated into graphene being reported to be superior in a superfluity of areas. Consequently, many are involved in the pursuit of producing new methodologies to fabricate pristine graphene on an industrial scale to meet the current world-wide appetite for graphene. One area which receives considerable interest is the field of electrochem., where graphene was reported to be beneficial in various applications ranging from sensing through to energy storage and generation and carbon-based mol. electronics. Electrochem. is an interfacial technique which is dominated by processes that occur at the solid-liq. interface and thus with the correct understanding can be beneficially utilized to characterize the surface under investigation. In this tutorial review fundamental concepts of Graphene Electrochem. are overviewed, making electrochem. characterization accessible to those who are working on new methodologies to fabricate graphene, bridging the gap between materials scientists and electrochemists and also assisting those exploring graphene in electrochem. areas, or that wish to start to. An overview of the recent understanding of graphene-modified electrodes is also provided, highlighting prominent applications reported in the current literature.
- 15McCreery, R. L. Advanced Carbon Electrode Materials for Molecular Electrochemistry Chem. Rev. (Washington, DC, U.S.) 2008, 108, 2646– 2687[ACS Full Text
], [CAS], Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXnt1Wjsb8%253D&md5=7f0e9958035ae161b937dd0508b959bfAdvanced Carbon Electrode Materials for Molecular ElectrochemistryMcCreery, Richard L.Chemical Reviews (Washington, DC, United States) (2008), 108 (7), 2646-2687CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. The properties of C are described and how these properties relate electrochem. properties, including electrode kinetics, adsorption and electrocatalysis. Fabrication and novel aspects are described for carbon materials, including, boron-doped diamond, carbon nanotubes, vapor deposited carbon films and various composite electrodes. Carbon electrode material for org. and biol. redox reactions are cited. - 16Li, W.; Tan, C.; Lowe, M. A.; Abruña, H. D.; Ralph, D. C. Electrochemistry of Individual Monolayer Graphene Sheets ACS Nano 2011, 5, 2264– 2270[ACS Full Text
], [CAS], Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXit1Witb0%253D&md5=e035a4b7f819411254811fe6f70c32d4Electrochemistry of Individual Monolayer Graphene SheetsLi, Wan; Tan, Cen; Lowe, Michael A.; Abruna, Hector D.; Ralph, Daniel C.ACS Nano (2011), 5 (3), 2264-2270CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)We report on the fabrication and measurement of devices designed to study the electrochem. behavior of individual monolayer graphene sheets as electrodes. We have examd. both mech. exfoliated and chem. vapor deposited (CVD) graphene. The effective device areas, detd. from cyclic voltammetric measurements, show good agreement with the geometric area of the graphene sheets, indicating that the redox reactions occur on clean graphene surfaces. The electron transfer rates of ferrocenemethanol at both types of graphene electrodes were >10-fold faster than at the basal plane of bulk graphite, which we ascribe to corrugations in the graphene sheets. We further describe an electrochem. investigation of adsorptive phenomena on graphene surfaces. Our results show that electrochem. can provide a powerful means of investigating the interactions between mols. and the surfaces of graphene sheets as electrodes. - 17Valota, A. T.; Kinloch, I. A.; Novoselov, K. S.; Casiraghi, C.; Eckmann, A.; Hill, E. W.; Dryfe, R. A. W. Electrochemical Behavior of Monolayer and Bilayer Graphene ACS Nano 2011, 5, 8809– 8815
- 18Sharma, R.; Baik, J. H.; Perera, C. J.; Strano, M. S. Anomalously Large Reactivity of Single Graphene Layers and Edges toward Electron Transfer Chemistries Nano Lett. 2010, 10, 398– 405[ACS Full Text
], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXivFOhtQ%253D%253D&md5=701e94e1a48832b205e58cd763046153Anomalously Large Reactivity of Single Graphene Layers and Edges toward Electron Transfer ChemistriesSharma, Richa; Baik, Joon Hyun; Perera, Chrisantha J.; Strano, Michael S.Nano Letters (2010), 10 (2), 398-405CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)The reactivity of graphene and its various multilayers toward electron transfer chemistries with 4-nitrobenzene diazonium tetrafluoroborate is probed by Raman spectroscopy after reaction on-chip. Single graphene sheets are found to be almost 10 times more reactive than bi- or multilayers of graphene according to the relative disorder (D) peak in the Raman spectrum examd. before and after chem. reaction in water. A model whereby electron puddles that shift the Dirac point locally to values below the Fermi level is consistent with the reactivity difference. Because the chem. at the graphene edge is important for controlling its electronic properties, particularly in ribbon form, we have developed a spectroscopic test to examine the relative reactivity of graphene edges vs. the bulk. We show, for the first time, that the reactivity of edges is at least two times higher than the reactivity of the bulk single graphene sheet, as supported by electron transfer theory. These differences in electron transfer rates may be important for selecting and manipulating graphitic materials on-chip. - 19Toth, P. S.; Valota, A.; Velicky, M.; Kinloch, I.; Novoselov, K.; Hill, E. W.; Dryfe, R. A. W. Electrochemistry in a Drop: A Study of the Electrochemical Behaviour of Mechanically Exfoliated Graphene on Photoresist Coated Silicon Substrate Chem. Sci. 2014, 5, 582– 589[Crossref], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXitVSqtbrM&md5=20b1f3d19a920a4bdfa138f712b9b7eaElectrochemistry in a drop: a study of the electrochemical behaviour of mechanically exfoliated graphene on photoresist coated silicon substrateToth, Peter S.; Valota, Anna T.; Velicky, Matej; Kinloch, Ian A.; Novoselov, Kostya S.; Hill, Ernie W.; Dryfe, Robert A. W.Chemical Science (2014), 5 (2), 582-589CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)A micro app. for electrochem. studies on individual high quality graphene flakes is presented. A microinjection-micromanipulator system has been employed to deposit droplets of aq. solns. contg. redox-active species directly on selected micro-scale areas of mech. exfoliated graphene layers on polymer coated silicon wafers. This approach allows the clear distinction between the electrochem. activity of pristine basal planes and the edges (defects) or steps to be measured. Voltammetric measurements were performed in a two-electrode configuration, and the std. heterogeneous electron transfer rate (k°) for redn. of hexachloroiridate (IrCl62-) was estd. The kinetics of electron transfer were evaluated for several types of graphene: mono, bi, and few layer basal planes, and the k° was estd. for an edge/step between two few layer graphene flakes. As a comparison, the kinetic behavior of graphite basal planes was measured for the deposited aq. droplets. The appearance of ruptures on the graphene monolayer was obsd. after deposition of the aq. soln. for the case of graphene on a bare silicon/silicon oxide substrate.
- 20Brownson, D. A. C.; Munro, L. J.; Kampouris, D. K.; Banks, C. E. Electrochemistry of Graphene: Not Such a Beneficial Electrode Material? RSC Adv. 2011, 1, 978– 988[Crossref], [CAS], Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtl2nsrjJ&md5=037ab9679226def75a8bc4a9c7f1babfElectrochemistry of graphene: not such a beneficial electrode material?Brownson, Dale A. C.; Munro, Lindsey J.; Kampouris, Dimitrios K.; Banks, Craig E.RSC Advances (2011), 1 (6), 978-988CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)The authors critically evaluate the reported electro-catalysis of graphene using inner-sphere and outer-sphere electrochem. redox probes, K ferrocyanide (II) and hexaammine-Ru(III) chloride, in addn. to L-ascorbic acid and β-NAD. Well characterized com. available graphene was used which was not chem. treated, is free from surfactants, and as a result of its fabrication has an extremely low O content allowing the electronic properties to be properly de-convoluted. Surprisingly graphene exhibits slow electron transfer towards the electrochem. probes studied, effectively blocking underlying electron transfer of the supporting electrode substrate likely due to its large basal and low edge plane content. Such observations, never reported before, suggest that graphene may not be such a beneficial electrode material as widely reported in the literature. D. Functional Theory is conducted on sym. graphene flakes of varying sizes indicating that the HOMO and LUMO energies are concd. around the edge of the graphene sheet, at the edge plane sites, rather than the central basal plane region, consistent with exptl. observations. The authors define differentiating coverage-based working regions for the electrochem. use of graphene: Zone I, where graphene addns. do not result in complete coverage of the underlying electrode and thus increasing basal contribution from graphene modification leads to increasingly reduced electron transfer and electrochem. activity; Zone II, once complete single-layer coverage is achieved, layered graphene viz graphite materializes with increased edge plane content and thus an increase in heterogeneous electron transfer is obsd. with increased layering. The authors offer insight into the electrochem. properties of these C materials, invaluable where electrode design for electrochem. sensing applications is sought.
- 21Goh, M. S.; Pumera, M. The Electrochemical Response of Graphene Sheets Is Independent of the Number of Layers from a Single Graphene Sheet to Multilayer Stacked Graphene Platelets Chem.—Asian J. 2010, 5, 2355– 2357[Crossref], [PubMed], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtlGmsLbO&md5=7eaf4ecf2cd2850ee4ad17a8a95a1845The Electrochemical Response of Graphene Sheets is Independent of the Number of Layers from a Single Graphene Sheet to Multilayer Stacked Graphene PlateletsGoh, Madeline Shuhua; Pumera, MartinChemistry - An Asian Journal (2010), 5 (11), 2355-2357CODEN: CAAJBI; ISSN:1861-4728. (Wiley-VCH Verlag GmbH & Co. KGaA)A comparison of electrochem. response of single, few- and multilayered graphene sheets was carried out and there in no significant difference between them in terms of voltammetric behavior. It appears that there is no need for single-layer graphene sheets for electrochem. applications. These is consistent with our observation that multilayered graphene nanoribbons exhibit a similar capacitance as the few-layer and single-layer graphene counter parts. The electrochem. oxidn. of dopamine and ascorbic acid on there electrodes was compared.
- 22Xie, X.; Zhao, K.; Xu, X.; Zhao, W.; Liu, S.; Zhu, Z.; Li, M.; Shi, Z.; Shao, Y. Study of Heterogeneous Electron Transfer on the Graphene/Self-Assembled Monolayer Modified Gold Electrode by Electrochemical Approaches J. Phys. Chem. C 2010, 114, 14243– 14250
- 23De, S.; Coleman, J. N. Are There Fundamental Limitations on the Sheet Resistance and Transmittance of Thin Graphene Films? ACS Nano 2010, 4, 2713– 2720[ACS Full Text
], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXksFeqtbY%253D&md5=775c95a20910210fcadd419ddd8ce215Are There Fundamental Limitations on the Sheet Resistance and Transmittance of Thin Graphene Films?De, Sukanta; Coleman, Jonathan N.ACS Nano (2010), 4 (5), 2713-2720CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)From published transmittance and sheet resistance data, we have calcd. a figure of merit for transparent, conducting graphene films; the DC to optical cond. ratio, σDC/σOp. For most reported results, this cond. ratio clusters around the values σDC/σOp = 0.7, 4.5, and 11. We show that these represent fundamental limiting values for networks of graphene flakes, undoped graphene stacks, and graphite films, resp. The limiting value for graphene flake networks is much too low for transparent-electrode applications. For graphite, a cond. ratio of 11 gives Rs = 377Ω/.box. for T = 90%, far short of the 10 Ω/.box. min. requirement for transparent conductors in current driven applications. However, we suggest that substrate-induced doping can potentially increase the 2-dimensional DC cond. enough to make graphene a viable transparent conductor. We show that four randomly stacked graphene layers can display T ≈ 90% and 10 Ω/.box. if the product of carrier d. and mobility reaches nμ = 1.3 × 1017 V-1 s-1. Given achieved doping values and attainable mobilities, this is just possible, resulting in potential values of σDC/σOp of up to 330. This is high enough for any transparent conductor application. - 24Zhang, B.; Fan, L.; Zhong, H.; Liu, Y.; Chen, S. Graphene Nanoelectrodes: Fabrication and Size-Dependent Electrochemistry J. Am. Chem. Soc. 2013, 135, 10073– 10080[ACS Full Text
], [CAS], Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXpsFWku7s%253D&md5=0dbeaa45d7c9cdd00e059d19302b8606Graphene Nanoelectrodes: Fabrication and Size-Dependent ElectrochemistryZhang, Bo; Fan, Lixin; Zhong, Huawei; Liu, Yuwen; Chen, ShengliJournal of the American Chemical Society (2013), 135 (27), 10073-10080CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The fabrication and electrochem. of a new class of graphene electrodes are presented. Through high-temp. annealing of hydrazine-reduced graphene oxides followed by high-speed centrifugation and size-selected ultrafiltration, flakes of reduced graphene oxides (r-GOs) of nanometer and submicrometer dimensions, resp., were obtained and sepd. from the larger ones. Using n-dodecanethiol-modified Au ultramicroelectrodes of appropriately small sizes, quick dipping in dil. suspensions of these small r-GOs allows attachment of only a single flake on the thiol monolayer. The electrodes thus fabricated were used to study the heterogeneous electron transfer (ET) kinetics at r-GOs and the nanoscopic charge transport dynamics at electrochem. interfaces. The r-GOs exhibit similarly high activity for electrochem. ET reactions to metal electrodes. Voltammetric anal. for the relatively slow ET reaction of Fe(CN)63- redn. produces slightly higher ET rate consts. at r-GOs of nanometer sizes than at large ones. These ET kinetic features are in accordance with the defect-dominant nature of the r-GOs and the increased defect d. in the nanometer-sized flakes as revealed by Raman spectroscopic measurements. The voltammetric enhancement and inhibition for the redn. of Ru(NH3)63+ and Fe(CN)63-, resp., at r-GO flakes of submicrometer and nanometer dimensions upon removal of supporting electrolyte significantly deviate in magnitude from those predicted by the electroneutrality-based electromigration theory, which may evidence the increased penetration of the diffuse double layer into the mass transport layer at nanoscopic electrochem. interfaces. - 25Ambrosi, A.; Bonanni, A.; Pumera, M. Electrochemistry of Folded Graphene Edges Nanoscale 2011, 3, 2256– 2260Google ScholarThere is no corresponding record for this reference.
- 26Brownson, D. A. C.; Banks, C. E. Cvd Graphene Electrochemistry: The Role of Graphitic Islands Phys. Chem. Chem. Phys. 2011, 13, 15825– 15828[Crossref], [PubMed], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVKjsr%252FE&md5=2023934a1cb6dd1a1b1a95e15009a553CVD graphene electrochemistry: the role of graphitic islandsBrownson, Dale A. C.; Banks, Craig E.Physical Chemistry Chemical Physics (2011), 13 (35), 15825-15828CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Graphitic islands are shown to dominate the electrochem. response at CVD grown graphene electrodes.
- 27Valota, A. T.; Toth, P. S.; Kim, Y. J.; Hong, B. H.; Kinloch, I. A.; Novoselov, K. S.; Hill, E. W.; Dryfe, R. A. W. Electrochemical Investigation of Chemical Vapour Deposition Monolayer and Bilayer Graphene on the Microscale Electrochim. Acta 2013, 110, 9– 15Google ScholarThere is no corresponding record for this reference.
- 28Tan, C.; Rodríguez-López, J.; Parks, J. J.; Ritzert, N. L.; Ralph, D. C.; Abruña, H. D. Reactivity of Monolayer Chemical Vapor Deposited Graphene Imperfections Studied Using Scanning Electrochemical Microscopy ACS Nano 2012, 6, 3070– 3079
- 29Ritzert, N. L.; Rodríguez-López, J.; Tan, C.; Abruña, H. D. Kinetics of Interfacial Electron Transfer at Single-Layer Graphene Electrodes in Aqueous and Nonaqueous Solutions Langmuir 2013, 29, 1683– 1694[ACS Full Text
], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXntVSrtQ%253D%253D&md5=8f8d99c4dac93ca5fb39c431598f3676Kinetics of Interfacial Electron Transfer at Single-Layer Graphene Electrodes in Aqueous and Nonaqueous SolutionsRitzert, Nicole L.; Rodriguez-Lopez, Joaquin; Tan, Cen; Abruna, Hector D.Langmuir (2013), 29 (5), 1683-1694CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The authors present a catalog of electron transfer mediators for studying the heterogeneous electron transfer kinetics of large-area, single-layer graphene electrodes. Scanning electrochem. microscopy (SECM) was used to probe the apparent std. electron transfer rate const. of mediators in aq. solns. and in MeCN and DMF, allowing for studies of graphene electroactivity at different potentials and in both aq. and nonaq. media. In aq. soln., Fe(III) EDTA, hexacyanoruthenate(II), hexacyanoferrate(II), hexacyanoferrate(III), octacyanomalybdate(IV), Co(III) sepulchrate, and hydroxymethylferrocene exhibited quasi-reversible electron transfer behavior. The electron transfer kinetics of hexaammineruthenium(III), Me viologen, and tris(2,2'-bipyridyl)ruthenium(II) are reversible in these studies. The electron transfer rate const. of hydroxymethylferrocene and ferrocene, in org. media, was similar to that for hydroxymethylferrocene in H2O, which, although fast, shows clear kinetic complications that the authors believe are inherent to graphene. Viologens, known to be reversible at metal electrodes, exhibited quasi-reversible electron transfer. For [Co(dapa)2]2+, where dapa is 2,6-bis[1-(phenylimino)ethyl]pyridine, in DMF, the oxidn. state of the redox pair studied affected the obsd. kinetics. Under similar exptl. conditions, the Co(I/II) couple exhibited nearly reversible behavior whereas Co(II/III) had finite kinetics. This behavior was ascribed to the large difference in self-exchange rates for these two processes. To demonstrate the utility of using these mediators for examg. graphene electrodes, the kinetics of two mediators with quasi-reversible electron transfer behavior, Fe EDTA and hexacyanoruthenate, were measured in the presence of a redox-active species [Os(bpy)2(dipy)Cl]PF6, where bpy is 2,2'-bipyridine and dipy is 4,4'-trimethylenedipyridine, adsorbed onto the graphene surface. The kinetics of both mediators were enhanced in the presence of 1-hundredth of a monolayer of the Os complex, showing that even small amts. of impurities on the graphene surface are capable of enhancing the obsd. kinetics. - 30Güell, A. G.; Ebejer, N.; Snowden, M. E.; MacPherson, J. V.; Unwin, P. R. Structural Correlations in Heterogeneous Electron Transfer at Monolayer and Multilayer Graphene Electrodes J. Am. Chem. Soc. 2012, 134, 7258– 7261
- 31Nicholson, R. S. Theory and Application of Cyclic Voltammetry for Measurement of Electrode Reaction Kinetics Anal. Chem. 1965, 37, 1351– 1355[ACS Full Text
], [CAS], Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF28XisFSksQ%253D%253D&md5=7f3073eb040d007e31d8989539fe8dceTheory and application of cyclic voltammetry for measurement of electrode reaction kineticsNicholson, Richard S.(1965), 37 (11), 1351-5CODEN: ANCHAM; ISSN:0003-2700.The theory of cyclic voltammetry is extended to include electron transfer reactions described by the electrochem. abs. rate equation. By use of numerical analysis, it is shown that a system which appears reversible at one frequency may be made to exhibit kinetic behavior at higher frequencies as indicated by increased sepn. of cathodic and anodic peak potentials. The standard rate const. for electron transfer is detd. from this peak potential sepn. and frequency. The redn. of Cd++ is used as an illustration. - 32Klingler, R. J.; Kochi, J. K. Electron-Transfer Kinetics from Cyclic Voltammetry. Quantitative Description of Electrochemical Reversibility J. Phys. Chem. 1981, 85, 1731– 1741[ACS Full Text
], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3MXktFGisr0%253D&md5=56df69cc55692b72e2b4881b11fb8995Electron-transfer kinetics from cyclic voltammetry. Quantitative description of electrochemical reversibilityKlingler, R. J.; Kochi, J. K.Journal of Physical Chemistry (1981), 85 (12), 1731-41CODEN: JPCHAX; ISSN:0022-3654.The measurement of the heterogeneous rate consts. for electron transfer from std. cyclic-voltammetric (CV) data is described. A variety of organometals were used as the electroactive species in which the forward electron transfer is unidirectional, i.e., totally irreversible. The heterogeneous rate consts. for the anodic process are quant. correlated with electron-transfer rate consts. obtained in homogeneous soln. with a variety of chem. oxidants. Since the CV method derives from a totally irreversible electrode process, a quant. measure of electrochem. reversibility was developed. The reversibility factor fr is a continuous function of the electrode kinetics, varying smoothly from fr = 1 for Nernstian behavior to fr = 0 for total irreversibility. The theor. and exptl. limits of error encountered in the application of the CV method were quant. evaluated by the reversibility factor fr. - 33Randles, J. E. B. A Cathode Ray Polarograph. Part II. The Current-Voltage Curves Trans. Faraday Soc. 1948, 44, 327– 338[Crossref], [CAS], Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaH1MXitF2h&md5=df554684034a19783951152a4ea3f42cCathode-ray polarograph. II. Current-voltage curvesRandles, J. E. B.Transactions of the Faraday Society (1948), 44 (), 327-38CODEN: TFSOA4; ISSN:0014-7672.A microelectrode immersed in a soln. contg. small amts. of electro-reducible or -oxidizable substances can be subjected to a fairly rapidly changing potential and the corresponding changes in the electrode current recorded on the screen of a cathode-ray tube. The diffusion current-voltage curve so obtained shows a sharp max. of the current corresponding to the onset of each electro-reduction or -oxidation. The theory of the diffusion process under these conditions is discussed, and a graphic solution is obtained for the case that the electrode reaction occurs reversibly, and that the reactants and products are sol. either in the aq. medium or the electrode material (which may be Hg). Good agreement between theoretical and exptl. curves is obtained. Photographs of exptl. cathode-ray traces show the effect on the current-voltage curves of slowness of the electrode reaction (irreversible electrode process), of variation in the rate of change of potential of the electrode, and of phenomena similar to polarographic maxima. Exptl. data are presented which indicate a strict proportionality between the concn. of a substance which reacts at the electrode, and the value of the corresponding diffusion current at its max. The cathode-ray polarograph can therefore be used for analytical purposes.
- 34Bard, A. J.; Faulkner, L. R. Electrochemical Methods. Fundamentals and Applications, 2nd ed.; John Wiley & Sons, Inc.: New York, 2001.Google ScholarThere is no corresponding record for this reference.
- 35Patel, A. N.; Collignon, M. G.; Oconnell, M. A.; Hung, W. O. Y.; McKelvey, K.; MacPherson, J. V.; Unwin, P. R. A New View of Electrochemistry at Highly Oriented Pyrolytic Graphite J. Am. Chem. Soc. 2012, 134, 20117– 20130[ACS Full Text
], [CAS], Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xhs1GrurvL&md5=d38b8f7b501d3ff1d4c9a5976867ddbbA New View of Electrochemistry at Highly Oriented Pyrolytic GraphitePatel, Anisha N.; Collignon, Manon Guille; O Connell, Michael A.; Hung, Wendy O. Y.; McKelvey, Kim; Macpherson, Julie V.; Unwin, Patrick R.Journal of the American Chemical Society (2012), 134 (49), 20117-20130CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Major new insights on electrochem. processes at graphite electrodes are reported, following extensive studies of two of the most studied redox couples, Fe(CN)64-/3- and Ru(NH3)63+/2+. Expts. were carried out on five different grades of highly oriented pyrolytic graphite (HOPG) that vary in step-edge height and surface coverage. Significantly, the same electrochem. characteristic is obsd. on all surfaces, independent of surface quality: initial cyclic voltammetry (CV) is close to reversible on freshly cleaved surfaces (>400 measurements for Fe(CN)64-/3- and >100 for Ru(NH3)63+/2+), in marked contrast to previous studies that found very slow electron transfer (ET) kinetics, with an interpretation that ET only occurs at step edges. Significantly, high spatial resoln. electrochem. imaging with scanning electrochem. cell microscopy, on the highest quality mech. cleaved HOPG, demonstrates definitively that the pristine basal surface supports fast ET, and that ET is not confined to step edges. However, the history of the HOPG surface strongly influences the electrochem. behavior. Thus, Fe(CN)64-/3- shows markedly diminished ET kinetics with either extended exposure of the HOPG surface to the ambient environment or repeated CV measurements. In situ at. force microscopy (AFM) reveals that the deterioration in apparent ET kinetics is coupled with the deposition of material on the HOPG electrode, while conducting-AFM highlights that, after cleaving, the local surface cond. of HOPG deteriorates significantly with time. These observations and new insights are not only important for graphite, but have significant implications for electrochem. at related C materials such as graphene and C nanotubes. - 36Edwards, M. A.; Bertoncello, P.; Unwin, P. R. Slow Diffusion Reveals the Intrinsic Electrochemical Activity of Basal Plane Highly Oriented Pyrolytic Graphite Electrodes J. Phys. Chem. C 2009, 113, 9218– 9223
- 37Lai, S. C. S.; Patel, A. N.; McKelvey, K.; Unwin, P. R. Definitive Evidence for Fast Electron Transfer at Pristine Basal Plane Graphite from High-Resolution Electrochemical Imaging Angew. Chem., Int. Ed. 2012, 51, 5405– 5408[Crossref], [CAS], Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xls1eisL4%253D&md5=911263889fe0dba6cf4c660485d8bf34Definitive Evidence for Fast Electron Transfer at Pristine Basal Plane Graphite from High-Resolution Electrochemical ImagingLai, Stanley C. S.; Patel, Anisha N.; McKelvey, Kim; Unwin, Patrick R.Angewandte Chemie, International Edition (2012), 51 (22), 5405-5408, S5405/1-S5405/12CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)SECCM has allowed to study ET at basal plane HOPG under conditions of very high mass transport and high spatial resoln., and where the liq. probe makes a series of fresh measurements across the surface. Authors have been able to isolate the response of the pristine basal plane (directly after cleaving, thus reflecting the intrinsic material properties), and they show unambiguously that ET is fast (close to reversible) for the two most studied redox couples. This new view which overturns more than two decades of past research not only impacts the understanding of the electroactivity of HOPG, but potentially the properties of related sp2 materials, such as carbon nanotubes and graphene, illustrating the importance of the findings. The studies also demonstrate the significant potential of SECCM as a new nanoscale probe of electrochem. and interfacial processes.
- 38Banks, C. E.; Davies, T. J.; Wildgoose, G. G.; Compton, R. G. Electrocatalysis at Graphite and Carbon Nanotube Modified Electrodes: Edge-Plane Sites and Tube Ends Are the Reactive Sites Chem. Commun. (Cambridge, U.K.) 2005, 829– 841[Crossref], [PubMed], [CAS], Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1Kru7k%253D&md5=b8ce2a6d898db36d7724da186c62bfe9Electrocatalysis at graphite and carbon nanotube modified electrodes: edge-plane sites and tube ends are the reactive sitesBanks, Craig E.; Davies, Trevor J.; Wildgoose, Gregory G.; Compton, Richard G.Chemical Communications (Cambridge, United Kingdom) (2005), (7), 829-841CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)A review. Carbon, and particularly graphite in its various forms, is an attractive electrode material. Two areas of particular interest are modified C electrodes and C nanotube electrodes. The authors focus on the relation between surface structure and electrochem. and chem. reactivity of electrodes based on these materials. The authors overview recent work in this area which led one to believe that much of the catalytic activity, electron transfer and chem. reactivity of graphitic C electrodes is at surface defect sites, and in particular edge-plane-like defect sites. The authors also question the claimed special catalytic properties of C nanotube modified electrodes.
- 39McDermott, M. T.; Kneten, K.; McCreery, R. L. Anthraquinonedisulfonate Adsorption, Electron-Transfer Kinetics, and Capacitance on Ordered Graphite Electrodes: The Important Role of Surface Defects J. Phys. Chem. 1992, 96, 3124– 3130
- 40Li, Z.; Wang, Y.; Kozbial, A.; Shenoy, G.; Zhou, F.; McGinley, R.; Ireland, P.; Morganstein, B.; Kunkel, A.; Surwade, S. P.et al. Effect of Airborne Contaminants on the Wettability of Supported Graphene and Graphite Nat. Mater. 2013, 12, 925– 931[Crossref], [PubMed], [CAS], Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFCjtL7L&md5=fb8e5319415cb6d764ad4d5ec9bb2f43Effect of airborne contaminants on the wettability of supported graphene and graphiteLi, Zhiting; Wang, Yongjin; Kozbial, Andrew; Shenoy, Ganesh; Zhou, Feng; McGinley, Rebecca; Ireland, Patrick; Morganstein, Brittni; Kunkel, Alyssa; Surwade, Sumedh P.; Li, Lei; Liu, HaitaoNature Materials (2013), 12 (10), 925-931CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)It is generally accepted that supported graphene is hydrophobic and that its water contact angle is similar to that of graphite. The authors show that the water contact angles of freshly prepd. supported graphene and graphite surfaces increase when they are exposed to ambient air. By using IR spectroscopy and XPS, the authors demonstrate that airborne hydrocarbons adsorb on graphitic surfaces, and that a concurrent decrease in the water contact angle occurs when these contaminants are partially removed by both thermal annealing and controlled UV-O3 treatment. Graphitic surfaces are more hydrophilic than previously believed, and these results suggest that previously reported data on the wettability of graphitic surfaces may have been affected by unintentional hydrocarbon contamination from ambient air.
- 41Hardcastle, T. P.; Seabourne, C. R.; Zan, R.; Brydson, R. M. D.; Bangert, U.; Ramasse, Q. M.; Novoselov, K. S.; Scott, A. J. Mobile Metal Adatoms on Single Layer, Bilayer, and Trilayer Graphene: An ab Initio DFT Study with van der Waals Corrections Correlated with Electron Microscopy Data Phys. Rev. B: Condens. Matter Mater. Phys. 2013, 87Google ScholarThere is no corresponding record for this reference.
- 42Zan, R.; Ramasse, Q. M.; Bangert, U.; Novoselov, K. S. Graphene Reknits Its Holes Nano Lett. 2012, 12, 3936– 3940[ACS Full Text
], [CAS], Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XpvVKlsLk%253D&md5=d45e6e40ff5388426ae04597f0b1b701Graphene Reknits Its HolesZan, Recep; Ramasse, Quentin M.; Bangert, Ursel; Novoselov, Konstantin S.Nano Letters (2012), 12 (8), 3936-3940CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Nanoholes, etched under an electron beam at room temp. in single-layer graphene sheets as a result of their interaction with metal impurities, are shown to heal spontaneously by filling up with either nonhexagon, graphene-like, or perfect hexagon 2D structures. Scanning transmission electron microscopy was employed to capture the healing process and study atom-by-atom the regrown structure. A combination of these nanoscale etching and reknitting processes could lead to new graphene tailoring approaches. - 43Rooney, M. B.; Coomber, D. C.; Bond, A. M. Achievement of Near-Reversible Behavior for the [Fe(CN)6]3–/4– Redox Couple Using Cyclic Voltammetry at Glassy Carbon, Gold, and Platinum Macrodisk Electrodes in the Absence of Added Supporting Electrolyte Anal. Chem. 2000, 72, 3486– 3491
- 44Meyer, J. C.; Geim, A. K.; Katsnelson, M. I.; Novoselov, K. S.; Booth, T. J.; Roth, S. The Structure of Suspended Graphene Sheets Nature 2007, 446, 60– 63[Crossref], [PubMed], [CAS], Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXit1arsLs%253D&md5=b15d9e9c829cd3cb83d96c4e04b2f335The structure of suspended graphene sheetsMeyer, Jannik C.; Geim, A. K.; Katsnelson, M. I.; Novoselov, K. S.; Booth, T. J.; Roth, S.Nature (London, United Kingdom) (2007), 446 (7131), 60-63CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)The recent discovery of graphene has sparked much interest, thus far focused on the peculiar electronic structure of this material, in which charge carriers mimic massless relativistic particles. However, the phys. structure of graphene-a single layer of carbon atoms densely packed in a honeycomb crystal lattice-is also puzzling. On the one hand, graphene appears to be a strictly two-dimensional material, exhibiting such a high crystal quality that electrons can travel submicrometre distances without scattering. However, perfect two-dimensional crystals cannot exist in the free state, according to both theory and expt. This incompatibility can be avoided by arguing that all the graphene structures studied so far were an integral part of larger three-dimensional structures, either supported by a bulk substrate or embedded in a three-dimensional matrix. Here the authors report on individual graphene sheets freely suspended on a microfabricated scaffold in vacuum or air. These membranes are only one atom thick, yet they still display long-range cryst. order. However, the authors' studies by TEM also reveal that these suspended graphene sheets are not perfectly flat: they exhibit intrinsic microscopic roughening such that the surface normal varies by several degrees and out-of-plane deformations reach 1 nm. The atomically thin single-crystal membranes offer ample scope for fundamental research and new technologies, whereas the obsd. corrugations in the 3rd dimension may provide subtle reasons for the stability of two-dimensional crystals.
- 45Wang, Q. H.; Jin, Z.; Kim, K. K.; Hilmer, A. J.; Paulus, G. L. C.; Shih, C. J.; Ham, M. H.; Sanchez-Yamagishi, J. D.; Watanabe, K.; Taniguchi, T.et al. Understanding and Controlling the Substrate Effect on Graphene Electron-Transfer Chemistry via Reactivity Imprint Lithography Nat. Chem. 2012, 4, 724– 732[Crossref], [PubMed], [CAS], Google Scholar45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFOgtrbM&md5=9cae91dfb1930855e06a54d1df3396edUnderstanding and controlling the substrate effect on graphene electron-transfer chemistry via reactivity imprint lithographyWang, Qing Hua; Jin, Zhong; Kim, Ki Kang; Hilmer, Andrew J.; Paulus, Geraldine L. C.; Shih, Chih-Jen; Ham, Moon-Ho; Sanchez-Yamagishi, Javier D.; Watanabe, Kenji; Taniguchi, Takashi; Kong, Jing; Jarillo-Herrero, Pablo; Strano, Michael S.Nature Chemistry (2012), 4 (9), 724-732CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Graphene has exceptional electronic, optical, mech. and thermal properties, which provide it with great potential for use in electronic, optoelectronic and sensing applications. The chem. functionalization of graphene was studied with a view to controlling its electronic properties and interactions with other materials. Covalent modification of graphene by org. diazonium salts was used to achieve these goals, but because graphene comprises only a single at. layer, it is strongly influenced by the underlying substrate. Here, the authors show a Stark difference in the rate of electron-transfer reactions with org. diazonium salts for monolayer graphene supported on a variety of substrates. Reactions proceed rapidly for graphene supported on SiO2 and Al2O3 (sapphire), but negligibly on alkyl-terminated and hexagonal boron nitride (hBN) surfaces, as shown by Raman spectroscopy. The authors also develop a model of reactivity based on substrate-induced electron-hole puddles in graphene, and achieve spatial patterning of chem. reactions in graphene by patterning the substrate.
- 46Elias, D. C.; Nair, R. R.; Mohiuddin, T. M. G.; Morozov, S. V.; Blake, P.; Halsall, M. P.; Ferrari, A. C.; Boukhvalov, D. W.; Katsnelson, M. I.; Geim, A. K.et al. Control of Graphene’s Properties by Reversible Hydrogenation: Evidence for Graphane Science 2009, 323, 610– 613Google ScholarThere is no corresponding record for this reference.
- 47Pierce, C.; Ewing, B. Localized Adsorption on Graphite Surfaces J. Phys. Chem. 1967, 71, 3408– 3413
- 48Schedin, F.; Geim, A. K.; Morozov, S. V.; Hill, E. W.; Blake, P.; Katsnelson, M. I.; Novoselov, K. S. Detection of Individual Gas Molecules Adsorbed on Graphene Nat. Mater. 2007, 6, 652– 655[Crossref], [PubMed], [CAS], Google Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXpvFKjsrs%253D&md5=dedbfc7b95a13316bcbb8ebc5956c1d3Detection of individual gas molecules adsorbed on grapheneSchedin, F.; Geim, A. K.; Morozov, S. V.; Hill, E. W.; Blake, P.; Katsnelson, M. I.; Novoselov, K. S.Nature Materials (2007), 6 (9), 652-655CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)Authors show that micrometre-size sensors made from graphene are capable of detecting individual events when a gas mol. attaches to or detaches from graphene's surface. The adsorbed mols. change the local carrier concn. in graphene one by one electron, which leads to step-like changes in resistance. The achieved sensitivity is due to the fact that graphene is an exceptionally low-noise material electronically, which makes it a promising candidate not only for chem. detectors but also for other applications where local probes sensitive to external charge, magnetic field or mech. strain are required.
- 49Davies, T. J.; Moore, R. R.; Banks, C. E.; Compton, R. G. The Cyclic Voltammetric Response of Electrochemically Heterogeneous Surfaces J. Electroanal. Chem. 2004, 574, 123– 152[Crossref], [CAS], Google Scholar49https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXps1Oqsbs%253D&md5=ea55c8ee14ae44d03bad09bdd9874aa7The cyclic voltammetric response of electrochemically heterogeneous surfacesDavies, Trevor J.; Moore, Ryan R.; Banks, Craig E.; Compton, Richard G.Journal of Electroanalytical Chemistry (2004), 574 (1), 123-152CODEN: JECHES ISSN:. (Elsevier B.V.)The cyclic voltammetric response of an electrode composed of 2 different electrode materials is modeled using finite difference simulations. The system can be thought of as an array of microelectrodes of one material dispersed over a different electrode material. First, a detailed study into the diffusional effects which arise when the distance between the individual microelectrodes is varied, leads to a simple method with which to obtain qual. data regarding the size of the different electrode materials and diffusion layer thickness. Second, a more quant. method is employed to det. the fractional coverage and no. of Au particles on an anthraquinone modified edge plane pyrolytic graphite electrode by comparing exptl. peak to peak sepns. with simulated working curves. The results are compared with a scanning electron microscope anal. of the same electrode surface. Third, the diffusion domain approach is applied to the basal plane highly ordered pyrolytic graphite (HOPG) surface in an attempt to explain the characteristic shapes of basal plane HOPG voltammograms. A method is presented for the approx. detn. of surface defect d., using macroelectrode cyclic voltammetry, and then trialled on a no. of different redox couples. The results are compared with 2 previous scanning tunneling microscopy studies of basal plane HOPG.
- 50Blake, P.; Hill, E. W.; Castro Neto, A. H.; Novoselov, K. S.; Jiang, D.; Yang, R.; Booth, T. J.; Geim, A. K. Making Graphene Visible Appl. Phys. Lett. 2007, 91Google ScholarThere is no corresponding record for this reference.
- 51Ferrari, A. C. Raman Spectroscopy of Graphene and Graphite: Disorder, Electron-Phonon Coupling, Doping and Nonadiabatic Effects Solid State Commun. 2007, 143, 47– 57[Crossref], [CAS], Google Scholar51https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXmt1yhtr0%253D&md5=b67986a7f5f92c4a5ab64950f3330d7aRaman spectroscopy of graphene and graphite: Disorder, electron-phonon coupling, doping and nonadiabatic effectsFerrari, Andrea C.Solid State Communications (2007), 143 (1-2), 47-57CODEN: SSCOA4; ISSN:0038-1098. (Elsevier Ltd.)The authors review recent work on Raman spectroscopy of graphite and graphene. The authors focus on the origin of the D and G peaks and the 2nd order of the D peak. The G and 2 D Raman peaks change in shape, position and relative intensity with no. of graphene layers. This reflects the evolution of the electronic structure and electron-phonon interactions. The authors then consider the effects of doping on the Raman spectra of graphene. The Fermi energy is tuned by applying a gate-voltage. This induces a stiffening of the Raman G peak for both holes and electrons doping. Thus Raman spectroscopy can be efficiently used to monitor no. of layers, quality of layers, doping level and confinement.
- 52Malard, L. M.; Pimenta, M. A.; Dresselhaus, G.; Dresselhaus, M. S. Raman Spectroscopy in Graphene Phys. Rep. 2009, 473, 51– 87[Crossref], [CAS], Google Scholar52https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXkvVSlt7o%253D&md5=12bf1e7387b80149aa99cd1a9c14a6d2Raman spectroscopy in grapheneMalard, L. M.; Pimenta, M. A.; Dresselhaus, G.; Dresselhaus, M. S.Physics Reports (2009), 473 (5-6), 51-87CODEN: PRPLCM; ISSN:0370-1573. (Elsevier B.V.)A review. Recent Raman scattering studies in different types of graphene samples are reviewed here. We first discuss the first-order and the double resonance Raman scattering mechanisms in graphene, which give rise to the most prominent Raman features. The detn. of the no. of layers in few-layer graphene is discussed, giving special emphasis to the possibility of using Raman spectroscopy to distinguish a monolayer from few-layer graphene stacked in the Bernal (AB) configuration. Different types of graphene samples produced both by exfoliation and using epitaxial methods are described and their Raman spectra are compared with those of 3D cryst. graphite and turbostratic graphite, in which the layers are stacked with rotational disorder. We show that Resonance Raman studies, where the energy of the excitation laser line can be tuned continuously, can be used to probe electrons and phonons near the Dirac point of graphene and, in particular allowing a detn. to be made of the tight-binding parameters for bilayer graphene. The special process of electron-phonon interaction that renormalizes the phonon energy giving rise to the Kohn anomaly is discussed, and is illustrated by gated expts. where the position of the Fermi level can be changed exptl. Finally, we discuss the ability of distinguishing armchair and zig-zag edges by Raman spectroscopy and studies in graphene nanoribbons in which the Raman signal is enhanced due to resonance with singularities in the d. of electronic states.
- 53Walker, P. L.; McKinstry, H. A.; Wright, C. C. X-Ray Diffraction Studies of a Graphitized Carbon—Changes in Interlayer Spacing and Binding Energy with Temperature Ind. Eng. Chem. 1953, 45, 1711– 1715
Cited By
This article is cited by 120 publications.
- Matěj Velický. Electrolyte versus Dielectric Gating of Two-Dimensional Materials. The Journal of Physical Chemistry C 2021, 125 (40) , 21803-21809. https://doi.org/10.1021/acs.jpcc.1c04795
- Péter S. Tóth, Gábor Szabó, Csaba Janáky. Structural Features Dictate the Photoelectrochemical Activities of Two-Dimensional MoSe2 and WSe2 Nanostructures. The Journal of Physical Chemistry C 2021, 125 (14) , 7701-7710. https://doi.org/10.1021/acs.jpcc.1c01265
- Manu Gautam, Zahid M. Bhat, Abdul Raafik, Steven Le Vot, Mruthunjayachari C. Devendrachari, Alagar Raja Kottaichamy, Neethu Christudas Dargily, Ravikumar Thimmappa, Olivier Fontaine, Musthafa Ottakam Thotiyl. Coulombic Force Gated Molecular Transport in Redox Flow Batteries. The Journal of Physical Chemistry Letters 2021, 12 (5) , 1374-1383. https://doi.org/10.1021/acs.jpclett.0c03584
- Anur Yadav, Michel Wehrhold, Tilmann J. Neubert, Rodrigo M. Iost, Kannan Balasubramanian. Fast Electron Transfer Kinetics at an Isolated Graphene Edge Nanoelectrode with and without Nanoparticles: Implications for Sensing Electroactive Species. ACS Applied Nano Materials 2020, 3 (12) , 11725-11735. https://doi.org/10.1021/acsanm.0c02171
- Irina M. Terrero Rodríguez, Alexandra J. Borrill, Katherine J. Schaffer, Jocelyn B. Hernandez, Glen D. O’Neil. Light-Addressable Electrochemical Sensing with Electrodeposited n-Silicon/Gold Nanoparticle Schottky Junctions. Analytical Chemistry 2020, 92 (16) , 11444-11452. https://doi.org/10.1021/acs.analchem.0c02512
- Matěj Velický, Sheng Hu, Colin R. Woods, Péter S. Tóth, Viktor Zólyomi, Andre K. Geim, Héctor D. Abruña, Kostya S. Novoselov, Robert A. W. Dryfe. Electron Tunneling through Boron Nitride Confirms Marcus–Hush Theory Predictions for Ultramicroelectrodes. ACS Nano 2020, 14 (1) , 993-1002. https://doi.org/10.1021/acsnano.9b08308
- Yi Xiao, Yi Su, Xiaodong Liu, Weilin Xu. Defect-Driven Heterogeneous Electron Transfer between an Individual Graphene Sheet and Electrode. The Journal of Physical Chemistry Letters 2019, 10 (18) , 5402-5407. https://doi.org/10.1021/acs.jpclett.9b02134
- Renat R. Nazmutdinov, Michael D. Bronshtein, Elizabeth Santos. Electron Transfer across the Graphene Electrode/Solution Interface: Interplay between Different Kinetic Regimes. The Journal of Physical Chemistry C 2019, 123 (19) , 12346-12354. https://doi.org/10.1021/acs.jpcc.9b02164
- Matěj Velický, Peter S. Toth, Colin R. Woods, Kostya S. Novoselov, Robert A. W. Dryfe. Electrochemistry of the Basal Plane versus Edge Plane of Graphite Revisited. The Journal of Physical Chemistry C 2019, 123 (18) , 11677-11685. https://doi.org/10.1021/acs.jpcc.9b01010
- O. Charles Nwamba, Elena Echeverria, David N. McIlroy, Aaron Austin, Jean’ne M. Shreeve, D. Eric Aston. Thermal Modification of Graphite for Fast Electron Transport and Increased Capacitance. ACS Applied Nano Materials 2019, 2 (1) , 228-240. https://doi.org/10.1021/acsanm.8b01887
- Elham Rahmanian, Carmen C. Mayorga-Martinez, Rasoul Malekfar, Jan Luxa, Zdenek Sofer, Martin Pumera. 1T-Phase Tungsten Chalcogenides (WS2, WSe2, WTe2) Decorated with TiO2 Nanoplatelets with Enhanced Electron Transfer Activity for Biosensing Applications. ACS Applied Nano Materials 2018, 1 (12) , 7006-7015. https://doi.org/10.1021/acsanm.8b01796
- Kai-Wen Chang, Ian Alvarez Santos, Yen Nguyen, Yen-Hsun Su, Chia Chen Hsu, Ya-Ping Hsieh, Mario Hofmann. Electrostatic Control over the Electrochemical Reactivity of Graphene. Chemistry of Materials 2018, 30 (20) , 7178-7182. https://doi.org/10.1021/acs.chemmater.8b03152
- Ran Chen, Amin Morteza Najarian, Niraja Kurapati, Ryan J. Balla, Alexander Oleinick, Irina Svir, Christian Amatore, Richard L. McCreery, Shigeru Amemiya. Self-Inhibitory Electron Transfer of the Co(III)/Co(II)-Complex Redox Couple at Pristine Carbon Electrode. Analytical Chemistry 2018, 90 (18) , 11115-11123. https://doi.org/10.1021/acs.analchem.8b03023
- Joel M. Katzen, Matěj Velický, Yuefeng Huang, Stacey Drakeley, William Hendren, Robert M. Bowman, Qiran Cai, Ying Chen, Lu Hua Li, Fumin Huang. Rigorous and Accurate Contrast Spectroscopy for Ultimate Thickness Determination of Micrometer-Sized Graphene on Gold and Molecular Sensing. ACS Applied Materials & Interfaces 2018, 10 (26) , 22520-22528. https://doi.org/10.1021/acsami.8b01208
- Amin Morteza Najarian, Ran Chen, Ryan J. Balla, Shigeru Amemiya, and Richard L. McCreery . Ultraflat, Pristine, and Robust Carbon Electrode for Fast Electron-Transfer Kinetics. Analytical Chemistry 2017, 89 (24) , 13532-13540. https://doi.org/10.1021/acs.analchem.7b03903
- R. Narayanan, H. Yamada, B. C. Marin, A. Zaretski, and P. R. Bandaru . Dimensionality-Dependent Electrochemical Kinetics at the Single-Layer Graphene–Electrolyte Interface. The Journal of Physical Chemistry Letters 2017, 8 (17) , 4004-4008. https://doi.org/10.1021/acs.jpclett.7b01688
- Xiao-Dong Yang, Yanping Zheng, Jing Yang, Wei Shi, Jin-Hui Zhong, Cankun Zhang, Xue Zhang, Yu-Hao Hong, Xin-Xing Peng, Zhi-You Zhou, and Shi-Gang Sun . Modeling Fe/N/C Catalysts in Monolayer Graphene. ACS Catalysis 2017, 7 (1) , 139-145. https://doi.org/10.1021/acscatal.6b02702
- Yuqin Zou, Alex S. Walton, Ian A. Kinloch, and Robert A. W. Dryfe . Investigation of the Differential Capacitance of Highly Ordered Pyrolytic Graphite as a Model Material of Graphene. Langmuir 2016, 32 (44) , 11448-11455. https://doi.org/10.1021/acs.langmuir.6b02910
- Xianwen Mao, Fei Guo, Esther H. Yan, Gregory C. Rutledge, and T. Alan Hatton . Remarkably High Heterogeneous Electron Transfer Activity of Carbon-Nanotube-Supported Reduced Graphene Oxide. Chemistry of Materials 2016, 28 (20) , 7422-7432. https://doi.org/10.1021/acs.chemmater.6b03024
- Patrick R. Unwin, Aleix G. Güell, and Guohui Zhang . Nanoscale Electrochemistry of sp2 Carbon Materials: From Graphite and Graphene to Carbon Nanotubes. Accounts of Chemical Research 2016, 49 (9) , 2041-2048. https://doi.org/10.1021/acs.accounts.6b00301
- Shigeru Amemiya, Ran Chen, Nikoloz Nioradze, and Jiyeon Kim . Scanning Electrochemical Microscopy of Carbon Nanomaterials and Graphite. Accounts of Chemical Research 2016, 49 (9) , 2007-2014. https://doi.org/10.1021/acs.accounts.6b00323
- Ran Chen, Ryan J. Balla, Zhiting Li, Haitao Liu, and Shigeru Amemiya . Origin of Asymmetry of Paired Nanogap Voltammograms Based on Scanning Electrochemical Microscopy: Contamination Not Adsorption. Analytical Chemistry 2016, 88 (16) , 8323-8331. https://doi.org/10.1021/acs.analchem.6b02273
- Matěj Velický, Mark A. Bissett, Colin R. Woods, Peter S. Toth, Thanasis Georgiou, Ian A. Kinloch, Kostya S. Novoselov, and Robert A. W. Dryfe . Photoelectrochemistry of Pristine Mono- and Few-Layer MoS2. Nano Letters 2016, 16 (3) , 2023-2032. https://doi.org/10.1021/acs.nanolett.5b05317
- Zhiting Li, Andrew Kozbial, Nikoloz Nioradze, David Parobek, Ganesh Jagadeesh Shenoy, Muhammad Salim, Shigeru Amemiya, Lei Li, and Haitao Liu . Water Protects Graphitic Surface from Airborne Hydrocarbon Contamination. ACS Nano 2016, 10 (1) , 349-359. https://doi.org/10.1021/acsnano.5b04843
- Philippe Fortgang, Teddy Tite, Vincent Barnier, Nedjla Zehani, Chiranjeevi Maddi, Florence Lagarde, Anne-Sophie Loir, Nicole Jaffrezic-Renault, Christophe Donnet, Florence Garrelie, and Carole Chaix . Robust Electrografting on Self-Organized 3D Graphene Electrodes. ACS Applied Materials & Interfaces 2016, 8 (2) , 1424-1433. https://doi.org/10.1021/acsami.5b10647
- Aleix G. Güell, Anatolii S. Cuharuc, Yang-Rae Kim, Guohui Zhang, Sze-yin Tan, Neil Ebejer, and Patrick R. Unwin . Redox-Dependent Spatially Resolved Electrochemistry at Graphene and Graphite Step Edges. ACS Nano 2015, 9 (4) , 3558-3571. https://doi.org/10.1021/acsnano.5b00550
- Jing Jiang, Guangcan Luo, Ziling Zhang, Bo Tan, Xuxiang Guo, Wei Li, Jingquan Zhang. Highly responsive ZnO nanorods array ultraviolet photodetectors modificated with reduced graphene oxide layer. Journal of Physics D: Applied Physics 2021, 54 (31) , 315104. https://doi.org/10.1088/1361-6463/abfe7d
- Muhammad Munem Ali, Jacob John Mitchell, Gregory Burwell, Klaudia Rejnhard, Cerys Anne Jenkins, Ehsaneh Daghigh Ahmadi, Sanjiv Sharma, Owen James Guy. Application of Molecular Vapour Deposited Al2O3 for Graphene-Based Biosensor Passivation and Improvements in Graphene Device Homogeneity. Nanomaterials 2021, 11 (8) , 2121. https://doi.org/10.3390/nano11082121
- Yabin An, Tengyu Liu, Chen Li, Xiong Zhang, Tao Hu, Xianzhong Sun, Kai Wang, Chengduo Wang, Yanwei Ma. A general route for the mass production of graphene-enhanced carbon composites toward practical pouch lithium-ion capacitors. Journal of Materials Chemistry A 2021, 9 (28) , 15654-15664. https://doi.org/10.1039/D1TA03933D
- Kai Luo, Ye-Bin Dai, Ming Li, Xue-Feng Wang, Li-Ping Zhou. Full range modulation of giant magnetoresistance in graphene–like zigzag nanoribbons via dual edge disorders. Physica E: Low-dimensional Systems and Nanostructures 2021, 130 , 114703. https://doi.org/10.1016/j.physe.2021.114703
- Stefan Goodwin, Zachary Coldrick, Sebastian Heeg, Bruce Grieve, Aravind Vijayaraghavan, Ernie W. Hill. Fabrication and electrochemical response of pristine graphene ultramicroelectrodes. Carbon 2021, 177 , 207-215. https://doi.org/10.1016/j.carbon.2021.02.078
- Zuzana Vlčková Živcová, Milan Bouša, Matěj Velický, Otakar Frank, Ladislav Kavan. In Situ Raman Microdroplet Spectroelectrochemical Investigation of CuSCN Electrodeposited on Different Substrates. Nanomaterials 2021, 11 (5) , 1256. https://doi.org/10.3390/nano11051256
- Sergey V. Doronin, Yury A. Budkov, Daniil M. Itkis. Electrocatalytic activity of doped graphene: Quantum-mechanical theory view. Carbon 2021, 175 , 202-214. https://doi.org/10.1016/j.carbon.2021.01.020
- Jiahong Wang, Zhen Zhang, Si Wang. Facile fabrication of Ag/GO/Ti electrode by one-step electrodeposition for the enhanced cathodic reduction of nitrate pollution. Journal of Water Process Engineering 2021, 40 , 101839. https://doi.org/10.1016/j.jwpe.2020.101839
- Wenjie Liu, Xiong Zhang, Yanan Xu, Chen Li, Kai Wang, Xianzhong Sun, Fangyuan Su, Cheng‐Meng Chen, Fangyan Liu, Zhong‐Shuai Wu, Yanwei Ma. Recent Advances on Carbon‐Based Materials for High Performance Lithium‐Ion Capacitors. Batteries & Supercaps 2021, 4 (3) , 407-428. https://doi.org/10.1002/batt.202000264
- Qiuqiu Wang, Juanhua Zhang, Yanbo Xu, Yingyi Wang, Liang Wu, Xuexiang Weng, Chunping You, Jiuju Feng. A one-step electrochemically reduced graphene oxide based sensor for sensitive voltammetric determination of furfural in milk products. Analytical Methods 2021, 13 (1) , 56-63. https://doi.org/10.1039/D0AY01789B
- R. Ashwini, V.G. Dileepkumar, K.R. Balaji, R. Viswanatha, C.R. Ravikumar, Chandan Srivastava, Mysore Sridhar Santosh. Ternary alkali metal chalcogenide engineered reduced graphene oxide (rGO) as a new class of composite (NaFeS2-rGO) and its electrochemical performance. Sensors International 2021, 2 , 100125. https://doi.org/10.1016/j.sintl.2021.100125
- Matěj Velický, Robert A.W. Dryfe. Electrochemistry of 2D nanomaterials. 2021,,, 485-536. https://doi.org/10.1016/B978-0-12-820055-1.00009-5
- Sergey A. Kislenko, Sergey V. Pavlov, Renat R. Nazmutdinov, Vitaliy A. Kislenko, Petr M. Chekushkin. Effect of a Au underlayer on outer-sphere electron transfer across a Au/graphene/electrolyte interface. Physical Chemistry Chemical Physics 2021, 26 https://doi.org/10.1039/D1CP03051E
- Natasha Ross, Noniko Civilized Nqakala. Electrochemical Determination of Hydrogen Peroxide by a Nonenzymatic Catalytically Enhanced Silver-Iron (III) Oxide/Polyoxometalate/Reduced Graphene Oxide Modified Glassy Carbon Electrode. Analytical Letters 2020, 53 (15) , 2445-2464. https://doi.org/10.1080/00032719.2020.1745223
- Tilmann J Neubert, Michel Wehrhold, Nur Selin Kaya, Kannan Balasubramanian. Faradaic effects in electrochemically gated graphene sensors in the presence of redox active molecules. Nanotechnology 2020, 31 (40) , 405201. https://doi.org/10.1088/1361-6528/ab98bc
- Reda Elshafey, Patrick Brisebois, Haya Abdulkarim, Ricardo Izquierdo, Ana C. Tavares, Mohamed Siaj. Effect of Graphene Oxide Sheet Size on the Response of a Label‐free Voltammetric Immunosensor for Cancer Marker VEGF. Electroanalysis 2020, 32 (10) , 2205-2212. https://doi.org/10.1002/elan.202000065
- Susan Sadeghi, Samaneh Ebadi. Sensitive Quantification of Fe(III) in Food Samples at Screen Printed Carbon Electrode Modified with Graphene and Piroxicam by Catalytic Adsorptive Voltammetry. Electroanalysis 2020, 32 (9) , 1983-1992. https://doi.org/10.1002/elan.202060068
- Zonglin Pan, Fangpeng Yu, Lin Li, Ming Liu, Chengwen Song, Jiawei Yang, Hanxu Li, Chunlei Wang, Yanqiu Pan, Tonghua Wang. Electrochemical filtration carbon membrane derived from coal for wastewater treatment: Insights into the evolution of electrical conductivity and electrochemical performance during carbonization. Separation and Purification Technology 2020, 247 , 116948. https://doi.org/10.1016/j.seppur.2020.116948
- O. Charles Nwamba, Elena Echeverria, Qiong Yu, Krishnan S. Raja, David N. McIlroy, Jean’ne M. Shreeve, D. Eric Aston. Increased electron transfer kinetics and thermally treated graphite stability through improved tunneling paths. Journal of Materials Science 2020, 55 (25) , 11411-11430. https://doi.org/10.1007/s10853-020-04846-6
- Tylan S. Watkins, Dipobrato Sarbapalli, Michael J. Counihan, Andrew S. Danis, Jingjing Zhang, Lu Zhang, Kevin R. Zavadil, Joaquín Rodríguez-López. A combined SECM and electrochemical AFM approach to probe interfacial processes affecting molecular reactivity at redox flow battery electrodes. Journal of Materials Chemistry A 2020, 8 (31) , 15734-15745. https://doi.org/10.1039/D0TA00836B
- Meng Jiang, Leiyu Feng, Xiong Zheng, Yinguang Chen. Bio-denitrification performance enhanced by graphene-facilitated iron acquisition. Water Research 2020, 180 , 115916. https://doi.org/10.1016/j.watres.2020.115916
- Philippa M. Shellard, Thunyaporn Srisubin, Mirja Hartmann, Joseph Butcher, Fan Fei, Henry Cox, Thomas P. McNamara, Trevor McArdle, Ashley M. Shepherd, Robert M. J. Jacobs, Thomas A. Waigh, Sabine L. Flitsch, Christopher F. Blanford. A versatile route to edge-specific modifications to pristine graphene by electrophilic aromatic substitution. Journal of Materials Science 2020, 55 (24) , 10284-10302. https://doi.org/10.1007/s10853-020-04662-y
- Pawin Iamprasertkun, Andinet Ejigu, Robert A. W. Dryfe. Understanding the electrochemistry of “water-in-salt” electrolytes: basal plane highly ordered pyrolytic graphite as a model system. Chemical Science 2020, 11 (27) , 6978-6989. https://doi.org/10.1039/D0SC01754J
- Elham Rahmanian, Carmen C. Mayorga-Martinez, Nasuha Rohaizad, Jan Luxa, Zdenek Sofer, Martin Pumera. Structural transition induced by niobium doping in layered titanium disulfide: The impact on electrocatalytic performance. Applied Materials Today 2020, 19 , 100555. https://doi.org/10.1016/j.apmt.2020.100555
- Natalia Festinger, Kamila Morawska, Vladimir Ivanovski, Magdalena Ziąbka, Katarzyna Jedlińska, Witold Ciesielski, Sylwia Smarzewska. Comparative Electroanalytical Studies of Graphite Flake and Multilayer Graphene Paste Electrodes. Sensors 2020, 20 (6) , 1684. https://doi.org/10.3390/s20061684
- Feiyan Liu, Huiping Zhang, Haoxin Huang, Ying Yan. Synthesis of graphene with different layers on paper-like sintered stainless steel fibers and its application as a metal-free catalyst for catalytic wet peroxide oxidation of phenol. Journal of Hazardous Materials 2020, 384 , 121246. https://doi.org/10.1016/j.jhazmat.2019.121246
- Shigeru Amemiya. Nanoelectrochemistry of Adsorption‐Coupled Electron Transfer at Carbon Electrodes. 2020,,, 1-31. https://doi.org/10.1002/9781119468288.ch1
- Je Min Yoo. Catalytic Degradation of Phenols by Recyclable CVD Graphene Films. 2020,,, 15-27. https://doi.org/10.1007/978-981-15-2233-8_2
- Marcin S. Filipiak, Daniel Vetter, Kishan Thodkar, Oscar Gutiérrez-Sanz, Martin Jönsson-Niedziółka, Alexey Tarasov. Electron transfer from FAD-dependent glucose dehydrogenase to single-sheet graphene electrodes. Electrochimica Acta 2020, 330 , 134998. https://doi.org/10.1016/j.electacta.2019.134998
- Di Yin, Yiyang Liu, Pengfei Song, Peng Chen, Xie Liu, Lankun Cai, Lehua Zhang. In situ growth of copper/reduced graphene oxide on graphite surfaces for the electrocatalytic reduction of nitrate. Electrochimica Acta 2019, 324 , 134846. https://doi.org/10.1016/j.electacta.2019.134846
- Jie Zhang, Jiayao Guo, Duan Chen, Jin-Hui Zhong, Jun-Yang Liu, Dongping Zhan. Heterogeneous electron transfer kinetics of defective graphene investigated by scanning electrochemical microscopy. Applied Surface Science 2019, 491 , 553-559. https://doi.org/10.1016/j.apsusc.2019.06.181
- Xuelei Pan, Xufeng Hong, Lin Xu, Yanxi Li, Mengyu Yan, Liqiang Mai. On-chip micro/nano devices for energy conversion and storage. Nano Today 2019, 28 , 100764. https://doi.org/10.1016/j.nantod.2019.100764
- Rubén Rizo, Sara Pérez‐Rodríguez, Gonzalo García. Well‐Defined Platinum Surfaces for the Ethanol Oxidation Reaction. ChemElectroChem 2019, 6 (18) , 4725-4738. https://doi.org/10.1002/celc.201900600
- Michel Wehrhold, Tilmann J. Neubert, Anur Yadav, Martin Vondráček, Rodrigo M. Iost, Jan Honolka, Kannan Balasubramanian. pH sensitivity of interfacial electron transfer at a supported graphene monolayer. Nanoscale 2019, 11 (31) , 14742-14756. https://doi.org/10.1039/C9NR05049C
- F. Bourquard, C. Donnet, F. Garrelie, A.‐S. Loir, F. Vocanson, V. Barnier, C. Chaix, C. Farre, N. Jaffrezic‐Renault, F. Lagarde, G. Raimondi. Self‐Organized 3D Graphene as a Robust Sensing Platform. 2019,,, 483-507. https://doi.org/10.1002/9781119468455.ch102
- Chen Li, Xiong Zhang, Congkai Sun, Kai Wang, Xianzhong Sun, Yanwei Ma. Recent progress of graphene-based materials in lithium-ion capacitors. Journal of Physics D: Applied Physics 2019, 52 (14) , 143001. https://doi.org/10.1088/1361-6463/aaff3a
- Meichuan Liu, Hongyang Ke, Caiqin Sun, Guoqiang Wang, Yu Wang, Guohua Zhao. A simple and highly selective electrochemical label-free aptasensor of 17β-estradiol based on signal amplification of bi-functional graphene. Talanta 2019, 194 , 266-272. https://doi.org/10.1016/j.talanta.2018.10.035
- Lucyano J. A. Macedo, Rodrigo M. Iost, Ayaz Hassan, Kannan Balasubramanian, Frank N. Crespilho. Bioelectronics and Interfaces Using Monolayer Graphene. ChemElectroChem 2019, 6 (1) , 31-59. https://doi.org/10.1002/celc.201800934
- Meichuan Liu, Caiqin Sun, Guoqiang Wang, Yu Wang, Hanxing Lu, Huijie Shi, Guohua Zhao. A simple, supersensitive and highly selective electrochemical aptasensor for Microcystin-LR based on synergistic signal amplification strategy with graphene, DNase I enzyme and Au nanoparticles. Electrochimica Acta 2019, 293 , 220-229. https://doi.org/10.1016/j.electacta.2018.09.197
- Zhenfei Chen, Yan Zhang, Jing Zhang, Jian Zhou. Electrochemical Sensing Platform Based on Three-Dimensional Holey Graphene for Highly Selective and Ultra-Sensitive Detection of Ascorbic Acid, Uric Acid, and Nitrite. Journal of The Electrochemical Society 2019, 166 (10) , B787-B792. https://doi.org/10.1149/2.1111910jes
- Jing Zhang, Yan Zhang, Jian Zhou, Ling Wang. Construction of a highly sensitive non-enzymatic nitrite sensor using electrochemically reduced holey graphene. Analytica Chimica Acta 2018, 1043 , 28-34. https://doi.org/10.1016/j.aca.2018.08.045
- Lin Jiang, Wangyang Fu, Yuvraj Y. Birdja, Marc T. M. Koper, Grégory F. Schneider. Quantum and electrochemical interplays in hydrogenated graphene. Nature Communications 2018, 9 (1) https://doi.org/10.1038/s41467-018-03026-0
- Réka Csiki, Simon Drieschner, Alina Lyuleeva, Anna Cattani-Scholz, Martin Stutzmann, Jose A. Garrido. Photocurrent generation of biohybrid systems based on bacterial reaction centers and graphene electrodes. Diamond and Related Materials 2018, 89 , 286-292. https://doi.org/10.1016/j.diamond.2018.09.005
- Xuejiao Ma, Miao Li, Xiang Liu, Lele Wang, Nan Chen, Jiacheng Li, Chuanping Feng. A graphene oxide nanosheet-modified Ti nanocomposite electrode with enhanced electrochemical property and stability for nitrate reduction. Chemical Engineering Journal 2018, 348 , 171-179. https://doi.org/10.1016/j.cej.2018.04.168
- Sabine Szunerits, Rabah Boukherroub. Graphene-based nanomaterials in innovative electrochemistry. Current Opinion in Electrochemistry 2018, 10 , 24-30. https://doi.org/10.1016/j.coelec.2018.03.016
- Xing Xuan, Hyo S. Yoon, Jae Y. Park. A wearable electrochemical glucose sensor based on simple and low-cost fabrication supported micro-patterned reduced graphene oxide nanocomposite electrode on flexible substrate. Biosensors and Bioelectronics 2018, 109 , 75-82. https://doi.org/10.1016/j.bios.2018.02.054
- Karsten Lehmann, Olena Yurchenko, Julia Melke, Anna Fischer, Gerald Urban. High electrocatalytic activity of metal-free and non-doped hierarchical carbon nanowalls towards oxygen reduction reaction. Electrochimica Acta 2018, 269 , 657-667. https://doi.org/10.1016/j.electacta.2018.03.054
- Swagotom Sarker, Pavan Chaturvedi, Litao Yan, Tom Nakotte, Xinqi Chen, Stephanie K. Richins, Sanjib Das, Jonathan Peters, Meng Zhou, Sergei N. Smirnov, Hongmei Luo. Synergistic effect of iron diselenide decorated multi-walled carbon nanotubes for enhanced heterogeneous electron transfer and electrochemical hydrogen evolution. Electrochimica Acta 2018, 270 , 138-146. https://doi.org/10.1016/j.electacta.2018.03.064
- Qi Xiao, Mengmeng Feng, Yi Liu, Shuangyan Lu, Yingzi He, Shan Huang. The graphene/polypyrrole/chitosan-modified glassy carbon electrode for electrochemical nitrite detection. Ionics 2018, 24 (3) , 845-859. https://doi.org/10.1007/s11581-017-2247-y
- Samuel J. Rowley-Neale, Edward P. Randviir, Ahmed S. Abo Dena, Craig E. Banks. An overview of recent applications of reduced graphene oxide as a basis of electroanalytical sensing platforms. Applied Materials Today 2018, 10 , 218-226. https://doi.org/10.1016/j.apmt.2017.11.010
- Xiao Zhang, Yanhua Wu, Yanfang Sun, Peng Ding, Qingyun Liu, Lin Tang, Jinxue Guo. Hybrid of Fe4[Fe(CN)6]3 nanocubes and MoS2 nanosheets on nitrogen-doped graphene realizing improved electrochemical hydrogen production. Electrochimica Acta 2018, 263 , 140-146. https://doi.org/10.1016/j.electacta.2018.01.051
- Chandan Singh, Md. Azahar Ali, Venu Reddy, Dinesh Singh, Cheol Gi Kim, G. Sumana, B.D. Malhotra. Biofunctionalized graphene oxide wrapped carbon nanotubes enabled microfluidic immunochip for bacterial cells detection. Sensors and Actuators B: Chemical 2018, 255 , 2495-2503. https://doi.org/10.1016/j.snb.2017.09.054
- Edward P. Randviir, Craig E. Banks. Graphene-Based Electrochemical Sensors. 2018,,, 141-164. https://doi.org/10.1007/5346_2018_25
- Qinggang Zhang, Wenming Xu, Congcong Han, Xiaokai Wang, Yixian Wang, Zhongtao Li, Wenting Wu, Mingbo Wu. Graphene structure boosts electron transfer of dual-metal doped carbon dots in photooxidation. Carbon 2018, 126 , 128-134. https://doi.org/10.1016/j.carbon.2017.10.006
- Qi Xiao, Jinrong Feng, Jiawen Li, Mengmeng Feng, Shan Huang. A label-free and ultrasensitive electrochemical aptasensor for lead( ii ) using a N,P dual-doped carbon dot–chitosan composite as a signal-enhancing platform and thionine as a signaling molecule. The Analyst 2018, 143 (19) , 4764-4773. https://doi.org/10.1039/C8AN00994E
- Je Min Yoo, Baekwon Park, Sang Jin Kim, Yong Seok Choi, Sungmin Park, Eun Hye Jeong, Hyukjin Lee, Byung Hee Hong. Catalytic degradation of phenols by recyclable CVD graphene films. Nanoscale 2018, 10 (13) , 5840-5844. https://doi.org/10.1039/C8NR00045J
- Pranati Nayak, Qiu Jiang, Rajeshkumar Mohanraman, Dalaver Anjum, Mohamed Nejib Hedhili, Husam N. Alshareef. Inherent electrochemistry and charge transfer properties of few-layered two-dimensional Ti 3 C 2 T x MXene. Nanoscale 2018, 10 (36) , 17030-17037. https://doi.org/10.1039/C8NR01883A
- Maziar Ghazinejad, Sunshine Holmberg, Oscar Pilloni, Laura Oropeza-Ramos, Marc Madou. Graphitizing Non-graphitizable Carbons by Stress-induced Routes. Scientific Reports 2017, 7 (1) https://doi.org/10.1038/s41598-017-16424-z
- Qi Xiao, Shuangyan Lu, Chusheng Huang, Wei Su, Shuyu Zhou, Jiarong Sheng, Shan Huang. An electrochemical chiral sensor based on amino-functionalized graphene quantum dots/β-cyclodextrin modified glassy carbon electrode for enantioselective detection of tryptophan isomers. Journal of the Iranian Chemical Society 2017, 14 (9) , 1957-1970. https://doi.org/10.1007/s13738-017-1134-9
- K. Jaouen, O. Henrotte, S. Campidelli, B. Jousselme, V. Derycke, R. Cornut. Localized electrochemistry for the investigation and the modification of 2D materials. Applied Materials Today 2017, 8 , 116-124. https://doi.org/10.1016/j.apmt.2017.05.001
- Matěj Velický, Peter S. Toth. From two-dimensional materials to their heterostructures: An electrochemist's perspective. Applied Materials Today 2017, 8 , 68-103. https://doi.org/10.1016/j.apmt.2017.05.003
- Peter S. Toth, Matěj Velický, Thomas J.A. Slater, Stephen D. Worrall, Sarah J. Haigh. Hydrogen evolution and capacitance behavior of Au/Pd nanoparticle-decorated graphene heterostructures. Applied Materials Today 2017, 8 , 125-131. https://doi.org/10.1016/j.apmt.2017.07.008
- H. Yamada, R. Narayanan, P. R. Bandaru. Electrochemical kinetics and dimensional considerations at the nanoscale: the influence of the density of states. MRS Communications 2017, 7 (3) , 651-657. https://doi.org/10.1557/mrc.2017.93
- Daniela Báez, Helena Pardo, Ignacio Laborda, José Marco, Claudia Yáñez, Soledad Bollo. Reduced Graphene Oxides: Influence of the Reduction Method on the Electrocatalytic Effect towards Nucleic Acid Oxidation. Nanomaterials 2017, 7 (7) , 168. https://doi.org/10.3390/nano7070168
- Matěj Velický, Peter S. Toth, Alexander M. Rakowski, Aidan P. Rooney, Aleksey Kozikov, Colin R. Woods, Artem Mishchenko, Laura Fumagalli, Jun Yin, Viktor Zólyomi, Thanasis Georgiou, Sarah J. Haigh, Kostya S. Novoselov, Robert A. W. Dryfe. Exfoliation of natural van der Waals heterostructures to a single unit cell thickness. Nature Communications 2017, 8 (1) https://doi.org/10.1038/ncomms14410
- Jicun Li, Feng Wang. Water graphene contact surface investigated by pairwise potentials from force-matching PAW-PBE with dispersion correction. The Journal of Chemical Physics 2017, 146 (5) , 054702. https://doi.org/10.1063/1.4974921
- Benjamin Diby Ossonon, Daniel Bélanger. Functionalization of graphene sheets by the diazonium chemistry during electrochemical exfoliation of graphite. Carbon 2017, 111 , 83-93. https://doi.org/10.1016/j.carbon.2016.09.063
- Kontad Ounnunkad, Hollie V. Patten, Matěj Velický, Anna K. Farquhar, Paula A. Brooksby, Alison J. Downard, Robert A. W. Dryfe. Electrowetting on conductors: anatomy of the phenomenon. Faraday Discussions 2017, 199 , 49-61. https://doi.org/10.1039/C6FD00252H
- Dongtao Liu, Md. Mahbubur Rahman, Chuangye Ge, Jaecheon Kim, Jae-Joon Lee. Highly stable and conductive PEDOT:PSS/graphene nanocomposites for biosensor applications in aqueous medium. New Journal of Chemistry 2017, 41 (24) , 15458-15465. https://doi.org/10.1039/C7NJ03330C
- Zhenbo Peng, Rui Yang, Min A. Kim, Lei Li, Haitao Liu. Influence of O 2 , H 2 O and airborne hydrocarbons on the properties of selected 2D materials. RSC Advances 2017, 7 (43) , 27048-27057. https://doi.org/10.1039/C7RA02130E
- Y. C. Jeong, J. H. Kim, S. H. Kwon, J. Y. Oh, J. Park, Y. Jung, S. G. Lee, S. J. Yang, C. R. Park. Rational design of exfoliated 1T MoS 2 @CNT-based bifunctional separators for lithium sulfur batteries. Journal of Materials Chemistry A 2017, 5 (45) , 23909-23918. https://doi.org/10.1039/C7TA08153G
- Yan Zhang, Congyu Wu, Jingyan Zhang, Shouwu Guo. Mass Transport Effect on Graphene Based Enzyme Electrochemical Biosensor for Oxalic Acid Detection. Journal of The Electrochemical Society 2017, 164 (2) , B29-B33. https://doi.org/10.1149/2.0401702jes
- Arunas Ramanavicius, Natalija German, Almira Ramanaviciene. Evaluation of Electron Transfer in Electrochemical System Based on Immobilized Gold Nanoparticles and Glucose Oxidase. Journal of The Electrochemical Society 2017, 164 (4) , G45-G49. https://doi.org/10.1149/2.0691704jes
- Yan Zhang, Huilian Hao, Linlin Wang. Effect of morphology and defect density on electron transfer of electrochemically reduced graphene oxide. Applied Surface Science 2016, 390 , 385-392. https://doi.org/10.1016/j.apsusc.2016.08.127
Abstract

Figure 1

Figure 1. Experimental setup. (a) Photograph of the experimental setup. (b) Schematic depicting the Si/SiO2 wafer with mechanically exfoliated flakes (working electrode, WE) contacted via silver epoxy and copper wire, microscope objective and a micropipette, which contains reference (RE) and counter electrodes (CE) and is connected to a micromanipulator and microinjector. (c) An optical micrograph of a droplet deposited on the surface of a monolayer graphene flake. The dashed lines and curves indicate edge planes (black), steps (white), cracks/defects (orange), folds (green), and microdroplet/flake interface (blue).
Figure 2

Figure 2. Cyclic voltammograms and associated kinetic analyses at graphene/graphite electrodes. (a) CV of Fe(CN)63–/4– on bilayer graphene, (b and d) show comparison of ET kinetics on 4-layer graphene using Ru(NH3)63+/2+ and on ∼70-layer thick graphite using IrCl62–/3–. Corresponding Klingler-Kochi and Nicholson analyses and calculated ET rates (k0) are shown in (c) and (e), respectively. The insets in the bottom right of graphs (a), (b), and (d) show micrographs of the deposited droplets. The series of voltammetric curves were obtained starting from the fastest scan rate of 1000 mV s–1 (dark blue) down to the slowest scan rate of 100 mV s–1 (gray) for Fe(CN)63–/4– and Ru(NH3)63+/2+ and 3000–250 mV s–1 for IrCl62–/3–. The potential was referenced against Ag/AgCl wire in 6 M LiCl, and held at the upper vertex potential for 10 s prior to the voltammetry (1 V for IrCl62–/3–). Change of the initial direction of the potential sweep had no observable effect.
Figure 3

Figure 3. Heterogeneous ET rate, k0, between the aqueous-based redox mediator and mechanically exfoliated graphite flakes of varied thicknesses. The averaged ET rates of reduction/oxidation of (a) Fe(CN)63–/4–, (b) Ru(NH3)63+/2+ and IrCl62–/3– reduction/oxidation are plotted as a function of the number of graphene layers. Each point on the graph is an arithmetic mean of at least 8 (thick flakes >7 layers) or 12 (thin flakes ≤7 layers) individual droplet measurements on a pristine basal plane surface of one or more flakes of a given thickness. The error bars are standard deviations of the mean. The number of individual droplets included in the analysis was 145, 146, and 144 for Fe(CN)63–/4–, Ru(NH3)63+/2+, and IrCl62–/3–, respectively. In total, 69 individual crystal surfaces were used for the analysis. Note that the graphs are shown on a semilogarithmic scale.
Figure 4

Figure 4. XPS survey spectra of atmosphere-aged (>1 month) graphite surface (top green) and pristine graphite surface cleaved immediately prior the XPS measurement (bottom red). Both spectra show data averaged from 5 different sites on the surface (spot size of 400 μm2). The quantitative elemental analysis is given in Table 2.
Figure 5

Figure 5. Effect of impurities on hybridization and functionalization of carbon atoms expressed by XPS analysis of both atmosphere-aged (circles) and cleaved (triangles) graphite surface. The extent of carbon sp2 hybridization, determined from C 1s peak (green) and Auger peak (D-parameter, blue), is proportional to the total carbon content (XPS survey quantification).
Figure 6

Figure 6. (a) Cyclic voltammograms recorded on natural graphite (solid curve), HOPG (dashed curve), platinum (dotted curve), and gold (dash-dot curve), and (b) corresponding ET kinetics obtained as an arithmetic mean of three independent measurements. Data in red and gray correspond to aged and cleaved surfaces, respectively. Mechanically polished metal surfaces exhibited almost reversible kinetics (>10–2 cm s–1) with peak separation below 65 mV at 1 V s–1.
Figure 7

Figure 7. (a) Raman spectra of the mono-, bi-, tri-, tetra/penta-, and multilayer graphene flakes, bottom to top, respectively (each spectrum is shown on a different intensity scale for the purpose of clarity). (b) 3D and 2D AFM scans (top and bottom-left, respectively) of a ca. 4/5-layer thick graphene flake with another monolayer on top, inset (bottom-right) shows the optical image of the scanned area, (c) cross-section of the same flake, indicated by green lines in (b).
References
ARTICLE SECTIONSThis article references 53 other publications.
- 1Mayorov, A. S.; Gorbachev, R. V.; Morozov, S. V.; Britnell, L.; Jalil, R.; Ponomarenko, L. A.; Blake, P.; Novoselov, K. S.; Watanabe, K.; Taniguchi, T.et al. Micrometer-Scale Ballistic Transport in Encapsulated Graphene at Room Temperature Nano Lett. 2011, 11, 2396– 2399[ACS Full Text
], [CAS], Google Scholar1https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXmtFSitr4%253D&md5=fe2d8b4f0479b5e28a3c60b02d46bb23Micrometer-scale ballistic transport in encapsulated graphene at room temperatureMayorov, Alexander S.; Gorbachev, Roman V.; Morozov, Sergey V.; Britnell, Liam; Jalil, Rashid; Ponomarenko, Leonid A.; Blake, Peter; Novoselov, Kostya S.; Watanabe, Kenji; Taniguchi, Takashi; Geim, A. K.Nano Letters (2011), 11 (6), 2396-2399CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Devices made from graphene encapsulated in hexagonal BN exhibit pronounced neg. bend resistance and an anomalous Hall effect, which are a direct consequence of room-temp. ballistic transport at a micrometer scale for a wide range of carrier concns. The encapsulation makes graphene practically insusceptible to the ambient atm. and, simultaneously, allows the use of BN as an ultrathin top gate dielec. - 2Balandin, A. A. Thermal Properties of Graphene and Nanostructured Carbon Materials Nat. Mater. 2011, 10, 569– 581[Crossref], [PubMed], [CAS], Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXpt1arur4%253D&md5=c421c612c38341eb8688df9055be32a9Thermal properties of graphene and nanostructured carbon materialsBalandin, Alexander A.Nature Materials (2011), 10 (8), 569-581CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)A review. Recent years have seen a rapid growth of interest by the scientific and engineering communities in the thermal properties of materials. Heat removal has become a crucial issue for continuing progress in the electronic industry, and thermal conduction in low-dimensional structures has revealed truly intriguing features. C allotropes and their derivs. occupy a unique place in terms of their ability to conduct heat. The room-temp. thermal cond. of C materials span an extraordinary large range, of over 5 orders of magnitude, from the lowest in amorphous carbons to the highest in graphene and C nanotubes. Here, I review the thermal properties of C materials focusing on recent results for graphene, C nanotubes, and nanostructured C materials with different degrees of disorder. Special attention is given to the unusual size dependence of heat conduction in 2D crystals and, specifically, in graphene. I also describe the prospects of applications of graphene and C materials for thermal management of electronics.
- 3Lee, C.; Wei, X.; Kysar, J. W.; Hone, J. Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene Science 2008, 321, 385– 388[Crossref], [PubMed], [CAS], Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXosVOrs7k%253D&md5=c85babfb5827a1ce93f7e9673a4c8b86Measurement of the Elastic Properties and Intrinsic Strength of Monolayer GrapheneLee, Changgu; Wei, Xiaoding; Kysar, Jeffrey W.; Hone, JamesScience (Washington, DC, United States) (2008), 321 (5887), 385-388CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an at. force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per m (N m-1) and -690 N m-1, resp. The breaking strength is 42 N m-1 and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of σint = 130 gigapascals for bulk graphite. These expts. establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mech. tested to deformations well beyond the linear regime.
- 4Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A. Electric Field in Atomically Thin Carbon Films Science 2004, 306, 666– 669[Crossref], [PubMed], [CAS], Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXos1Kqt70%253D&md5=488da13500bf24e8fc419052dc1a9e84Electric Field Effect in Atomically Thin Carbon FilmsNovoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A.Science (Washington, DC, United States) (2004), 306 (5696), 666-669CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The authors describe monocryst. graphitic films, which are a few atoms thick but are nonetheless stable under ambient conditions, metallic, and of remarkably high quality. The films are a two-dimensional semimetal with a tiny overlap between valence and conductance bands, and they exhibit a strong ambipolar elec. field effect such that electrons and holes in concns. up to 1013 per square centimeter and with room-temp. mobilities of ∼10,000 square centimeters per V-second can be induced by applying gate voltage.
- 5Geim, A. K. Graphene: Status and Prospects Science 2009, 324, 1530– 1534[Crossref], [PubMed], [CAS], Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXnsFOrsLk%253D&md5=246440adb8c23a1d5ff923d1d80ff920Graphene: Status and ProspectsGeim, A. K.Science (Washington, DC, United States) (2009), 324 (5934), 1530-1534CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A review. Graphene is a wonder material with many superlatives to its name. It is the thinnest known material in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic mobility, have zero effective mass, and can travel for micrometers without scattering at room temp. Graphene can sustain current densities six orders of magnitude higher than that of copper, shows record thermal cond. and stiffness, is impermeable to gases, and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation, which allows the investigation of relativistic quantum phenomena in a benchtop expt. This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.
- 6Novoselov, K. S.; Fal’Ko, V. I.; Colombo, L.; Gellert, P. R.; Schwab, M. G.; Kim, K. A Roadmap for Graphene Nature 2012, 490, 192– 200[Crossref], [PubMed], [CAS], Google Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsVyrsrrO&md5=39fd29cc6d8a772bfa811f57bc142fd7A roadmap for grapheneNovoselov, K. S.; Fal'ko, V. I.; Colombo, L.; Gellert, P. R.; Schwab, M. G.; Kim, K.Nature (London, United Kingdom) (2012), 490 (7419), 192-200CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)A review. Recent years have witnessed many breakthroughs in research on graphene (the first 2D at. crystal) as well as a significant advance in the mass prodn. of this material. This one-atom-thick fabric of C uniquely combines extreme mech. strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of prodn. methods, and critically analyze the feasibility of various graphene applications.
- 7Nair, R. R.; Blake, P.; Grigorenko, A. N.; Novoselov, K. S.; Booth, T. J.; Stauber, T.; Peres, N. M. R.; Geim, A. K. Fine Structure Constant Defines Visual Transparency of Graphene Science 2008, 320, 1308[Crossref], [PubMed], [CAS], Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXmslWgt7k%253D&md5=e99cdff43e2bef193cf9767c6619b4daFine Structure Constant Defines Visual Transparency of GrapheneNair, R. R.; Blake, P.; Grigorenko, A. N.; Novoselov, K. S.; Booth, T. J.; Stauber, T.; Peres, N. M. R.; Geim, A. K.Science (Washington, DC, United States) (2008), 320 (5881), 1308CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)There is a small group of phenomena in condensed matter physics that is defined only by the fundamental consts. and does not depend on material parameters. Examples are the resistivity quantum, h/e2 (h is Planck's const. and e the electron charge), that appears in a variety of transport expts. and the magnetic flux quantum, h/e, playing an important role in the physics of supercond. By and large, sophisticated facilities and special measurement conditions are required to observe any of these phenomena. We show that the opacity of suspended graphene is defined solely by the fine structure const., α = e2/ℏc ≈ 1/137 (where c is the speed of light), the parameter that describes coupling between light and relativistic electrons and that is traditionally assocd. with quantum electrodynamics rather than materials science. Despite being only one atom thick, graphene is found to absorb a significant (πα = 2.3%) fraction of incident white light, a consequence of graphene's unique electronic structure.
- 8Moser, J.; Barreiro, A.; Bachtold, A. Current-Induced Cleaning of Graphene Appl. Phys. Lett. 2007, 91Google ScholarThere is no corresponding record for this reference.
- 9Topsakal, M.; Aahin, H.; Ciraci, S. Graphene Coatings: An Efficient Protection from Oxidation Phys. Rev. B: Condens. Matter Mater. Phys. 2012, 85Google ScholarThere is no corresponding record for this reference.
- 10Wang, Y.; Li, Z.; Wang, J.; Li, J.; Lin, Y. Graphene and Graphene Oxide: Biofunctionalization and Applications in Biotechnology Trends Biotechnol. 2011, 29, 205– 212[Crossref], [PubMed], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXltFegtrY%253D&md5=4f02be84ecfa6dbc1cd617f8bab2f76fGraphene and graphene oxide: biofunctionalization and applications in biotechnologyWang, Ying; Li, Zhaohui; Wang, Jun; Li, Jinghong; Lin, YueheTrends in Biotechnology (2011), 29 (5), 205-212CODEN: TRBIDM; ISSN:0167-7799. (Elsevier B.V.)A review. Graphene is the basic building block of 0D fullerene, 1D carbon nanotubes, and 3D graphite. Graphene has a unique planar structure, as well as novel electronic properties, which have attracted great interests from scientists. This review selectively analyzes current advances in the field of graphene bioapplications. In particular, the biofunctionalization of graphene for biol. applications, fluorescence-resonance-energy-transfer-based biosensor development by graphene or graphene-based nanomaterials, and the investigation of graphene or graphene-based nanomaterials for living cell studies are summarized in more detail. Future perspectives and possible challenges in this rapidly developing area are also discussed.
- 11Lee, J. K.; Smith, K. B.; Hayner, C. M.; Kung, H. H. Silicon Nanoparticles-Graphene Paper Composites for Li Ion Battery Anodes Chem. Commun. (Cambridge, U.K.) 2010, 46, 2025– 2027[Crossref], [PubMed], [CAS], Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXjtVSnsrw%253D&md5=627b7dfbe71bdbbbde0dd9da672b4fb7Silicon nanoparticles-graphene paper composites for Li ion battery anodesLee, Jeong K.; Smith, Kurt B.; Hayner, Cary M.; Kung, Harold H.Chemical Communications (Cambridge, United Kingdom) (2010), 46 (12), 2025-2027CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)Composites of Si nanoparticles highly dispersed between graphene sheets, and supported by a three-dimensional network of graphite formed by reconstituting regions of graphene stacks exhibit high Li ion storage capacities and cycling stability. An electrode was prepd. with a storage capacity >2200 mA-h/g after 50 cycles and >1500 mA-h/g after 200 cycles that decreased by <0.5% per cycle.
- 12Wang, X.; Zhi, L.; Müllen, K. Transparent, Conductive Graphene Electrodes for Dye-Sensitized Solar Cells Nano Lett. 2008, 8, 323– 327[ACS Full Text
], [CAS], Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhsVejtbnK&md5=75dbbd7c51272355e9ca50a75e9de3acTransparent, Conductive Graphene Electrodes for Dye-Sensitized Solar CellsWang, Xuan; Zhi, Linjie; Muellen, KlausNano Letters (2008), 8 (1), 323-327CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)A transparent, conductive and ultrathin graphene film is an alternative to a metal oxide window electrode for solid-state dye-sensitized solar cells. The graphene films are fabricated from exfoliated graphite oxide, followed by thermal redn. These films exhibit a high cond. of 550 S/cm and a transparency of >70% over 1000-3000 nm. They also have good chem. and thermal stabilities as well as an ultra-smooth surface with tunable wettability. - 13Stoller, M. D.; Park, S.; Yanwu, Z.; An, J.; Ruoff, R. S. Graphene-Based Ultracapacitors Nano Lett. 2008, 8, 3498– 3502[ACS Full Text
], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtFaitLjE&md5=935ad6b5a3e3685d1907eb62d1fd5ad6Graphene-Based UltracapacitorsStoller, Meryl D.; Park, Sungjin; Zhu, Yanwu; An, Jinho; Ruoff, Rodney S.Nano Letters (2008), 8 (10), 3498-3502CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)The surface area of a single graphene sheet is 2630 m2/g, substantially higher than values derived from BET surface area measurements of activated carbons used in current electrochem. double layer capacitors. The authors' group has pioneered a new carbon material that the authors call chem. modified graphene (CMG). CMG materials are made from 1-atom thick sheets of carbon, functionalized as needed, and here the authors demonstrate in an ultracapacitor cell their performance. Specific capacitances of 135 and 99 F/g in aq. and org. electrolytes, resp., were measured. High elec. cond. gives these materials consistently good performance over a wide range of voltage scan rates. These encouraging results illustrate the exciting potential for high performance, elec. energy storage devices based on this new class of carbon material. - 14Brownson, D. A. C.; Kampouris, D. K.; Banks, C. E. Graphene Electrochemistry: Fundamental Concepts through to Prominent Applications Chem. Soc. Rev. 2012, 41, 6944– 6976[Crossref], [PubMed], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsVOnurfN&md5=7d643e49014b33d7dc63736ae2424df2Graphene electrochemistry: fundamental concepts through to prominent applicationsBrownson, Dale A. C.; Kampouris, Dimitrios K.; Banks, Craig E.Chemical Society Reviews (2012), 41 (21), 6944-6976CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. The use of graphene, a one atom thick individual planar carbon layer, has exploded in a plethora of scientific disciplines since it was reported to possess a range of unique and exclusive properties. Despite graphene being explored theor. since the 1940s and known to exist since the 1960s, the recent burst of interest from a large proportion of scientists globally can be correlated with work by Geim and Novoselov in 2004/5, who reported the so-called "scotch tape method" for the prodn. of graphene in addn. to identifying its unique electronic properties which has escalated into graphene being reported to be superior in a superfluity of areas. Consequently, many are involved in the pursuit of producing new methodologies to fabricate pristine graphene on an industrial scale to meet the current world-wide appetite for graphene. One area which receives considerable interest is the field of electrochem., where graphene was reported to be beneficial in various applications ranging from sensing through to energy storage and generation and carbon-based mol. electronics. Electrochem. is an interfacial technique which is dominated by processes that occur at the solid-liq. interface and thus with the correct understanding can be beneficially utilized to characterize the surface under investigation. In this tutorial review fundamental concepts of Graphene Electrochem. are overviewed, making electrochem. characterization accessible to those who are working on new methodologies to fabricate graphene, bridging the gap between materials scientists and electrochemists and also assisting those exploring graphene in electrochem. areas, or that wish to start to. An overview of the recent understanding of graphene-modified electrodes is also provided, highlighting prominent applications reported in the current literature.
- 15McCreery, R. L. Advanced Carbon Electrode Materials for Molecular Electrochemistry Chem. Rev. (Washington, DC, U.S.) 2008, 108, 2646– 2687[ACS Full Text
], [CAS], Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXnt1Wjsb8%253D&md5=7f0e9958035ae161b937dd0508b959bfAdvanced Carbon Electrode Materials for Molecular ElectrochemistryMcCreery, Richard L.Chemical Reviews (Washington, DC, United States) (2008), 108 (7), 2646-2687CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. The properties of C are described and how these properties relate electrochem. properties, including electrode kinetics, adsorption and electrocatalysis. Fabrication and novel aspects are described for carbon materials, including, boron-doped diamond, carbon nanotubes, vapor deposited carbon films and various composite electrodes. Carbon electrode material for org. and biol. redox reactions are cited. - 16Li, W.; Tan, C.; Lowe, M. A.; Abruña, H. D.; Ralph, D. C. Electrochemistry of Individual Monolayer Graphene Sheets ACS Nano 2011, 5, 2264– 2270[ACS Full Text
], [CAS], Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXit1Witb0%253D&md5=e035a4b7f819411254811fe6f70c32d4Electrochemistry of Individual Monolayer Graphene SheetsLi, Wan; Tan, Cen; Lowe, Michael A.; Abruna, Hector D.; Ralph, Daniel C.ACS Nano (2011), 5 (3), 2264-2270CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)We report on the fabrication and measurement of devices designed to study the electrochem. behavior of individual monolayer graphene sheets as electrodes. We have examd. both mech. exfoliated and chem. vapor deposited (CVD) graphene. The effective device areas, detd. from cyclic voltammetric measurements, show good agreement with the geometric area of the graphene sheets, indicating that the redox reactions occur on clean graphene surfaces. The electron transfer rates of ferrocenemethanol at both types of graphene electrodes were >10-fold faster than at the basal plane of bulk graphite, which we ascribe to corrugations in the graphene sheets. We further describe an electrochem. investigation of adsorptive phenomena on graphene surfaces. Our results show that electrochem. can provide a powerful means of investigating the interactions between mols. and the surfaces of graphene sheets as electrodes. - 17Valota, A. T.; Kinloch, I. A.; Novoselov, K. S.; Casiraghi, C.; Eckmann, A.; Hill, E. W.; Dryfe, R. A. W. Electrochemical Behavior of Monolayer and Bilayer Graphene ACS Nano 2011, 5, 8809– 8815
- 18Sharma, R.; Baik, J. H.; Perera, C. J.; Strano, M. S. Anomalously Large Reactivity of Single Graphene Layers and Edges toward Electron Transfer Chemistries Nano Lett. 2010, 10, 398– 405[ACS Full Text
], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXivFOhtQ%253D%253D&md5=701e94e1a48832b205e58cd763046153Anomalously Large Reactivity of Single Graphene Layers and Edges toward Electron Transfer ChemistriesSharma, Richa; Baik, Joon Hyun; Perera, Chrisantha J.; Strano, Michael S.Nano Letters (2010), 10 (2), 398-405CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)The reactivity of graphene and its various multilayers toward electron transfer chemistries with 4-nitrobenzene diazonium tetrafluoroborate is probed by Raman spectroscopy after reaction on-chip. Single graphene sheets are found to be almost 10 times more reactive than bi- or multilayers of graphene according to the relative disorder (D) peak in the Raman spectrum examd. before and after chem. reaction in water. A model whereby electron puddles that shift the Dirac point locally to values below the Fermi level is consistent with the reactivity difference. Because the chem. at the graphene edge is important for controlling its electronic properties, particularly in ribbon form, we have developed a spectroscopic test to examine the relative reactivity of graphene edges vs. the bulk. We show, for the first time, that the reactivity of edges is at least two times higher than the reactivity of the bulk single graphene sheet, as supported by electron transfer theory. These differences in electron transfer rates may be important for selecting and manipulating graphitic materials on-chip. - 19Toth, P. S.; Valota, A.; Velicky, M.; Kinloch, I.; Novoselov, K.; Hill, E. W.; Dryfe, R. A. W. Electrochemistry in a Drop: A Study of the Electrochemical Behaviour of Mechanically Exfoliated Graphene on Photoresist Coated Silicon Substrate Chem. Sci. 2014, 5, 582– 589[Crossref], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXitVSqtbrM&md5=20b1f3d19a920a4bdfa138f712b9b7eaElectrochemistry in a drop: a study of the electrochemical behaviour of mechanically exfoliated graphene on photoresist coated silicon substrateToth, Peter S.; Valota, Anna T.; Velicky, Matej; Kinloch, Ian A.; Novoselov, Kostya S.; Hill, Ernie W.; Dryfe, Robert A. W.Chemical Science (2014), 5 (2), 582-589CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)A micro app. for electrochem. studies on individual high quality graphene flakes is presented. A microinjection-micromanipulator system has been employed to deposit droplets of aq. solns. contg. redox-active species directly on selected micro-scale areas of mech. exfoliated graphene layers on polymer coated silicon wafers. This approach allows the clear distinction between the electrochem. activity of pristine basal planes and the edges (defects) or steps to be measured. Voltammetric measurements were performed in a two-electrode configuration, and the std. heterogeneous electron transfer rate (k°) for redn. of hexachloroiridate (IrCl62-) was estd. The kinetics of electron transfer were evaluated for several types of graphene: mono, bi, and few layer basal planes, and the k° was estd. for an edge/step between two few layer graphene flakes. As a comparison, the kinetic behavior of graphite basal planes was measured for the deposited aq. droplets. The appearance of ruptures on the graphene monolayer was obsd. after deposition of the aq. soln. for the case of graphene on a bare silicon/silicon oxide substrate.
- 20Brownson, D. A. C.; Munro, L. J.; Kampouris, D. K.; Banks, C. E. Electrochemistry of Graphene: Not Such a Beneficial Electrode Material? RSC Adv. 2011, 1, 978– 988[Crossref], [CAS], Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtl2nsrjJ&md5=037ab9679226def75a8bc4a9c7f1babfElectrochemistry of graphene: not such a beneficial electrode material?Brownson, Dale A. C.; Munro, Lindsey J.; Kampouris, Dimitrios K.; Banks, Craig E.RSC Advances (2011), 1 (6), 978-988CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)The authors critically evaluate the reported electro-catalysis of graphene using inner-sphere and outer-sphere electrochem. redox probes, K ferrocyanide (II) and hexaammine-Ru(III) chloride, in addn. to L-ascorbic acid and β-NAD. Well characterized com. available graphene was used which was not chem. treated, is free from surfactants, and as a result of its fabrication has an extremely low O content allowing the electronic properties to be properly de-convoluted. Surprisingly graphene exhibits slow electron transfer towards the electrochem. probes studied, effectively blocking underlying electron transfer of the supporting electrode substrate likely due to its large basal and low edge plane content. Such observations, never reported before, suggest that graphene may not be such a beneficial electrode material as widely reported in the literature. D. Functional Theory is conducted on sym. graphene flakes of varying sizes indicating that the HOMO and LUMO energies are concd. around the edge of the graphene sheet, at the edge plane sites, rather than the central basal plane region, consistent with exptl. observations. The authors define differentiating coverage-based working regions for the electrochem. use of graphene: Zone I, where graphene addns. do not result in complete coverage of the underlying electrode and thus increasing basal contribution from graphene modification leads to increasingly reduced electron transfer and electrochem. activity; Zone II, once complete single-layer coverage is achieved, layered graphene viz graphite materializes with increased edge plane content and thus an increase in heterogeneous electron transfer is obsd. with increased layering. The authors offer insight into the electrochem. properties of these C materials, invaluable where electrode design for electrochem. sensing applications is sought.
- 21Goh, M. S.; Pumera, M. The Electrochemical Response of Graphene Sheets Is Independent of the Number of Layers from a Single Graphene Sheet to Multilayer Stacked Graphene Platelets Chem.—Asian J. 2010, 5, 2355– 2357[Crossref], [PubMed], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtlGmsLbO&md5=7eaf4ecf2cd2850ee4ad17a8a95a1845The Electrochemical Response of Graphene Sheets is Independent of the Number of Layers from a Single Graphene Sheet to Multilayer Stacked Graphene PlateletsGoh, Madeline Shuhua; Pumera, MartinChemistry - An Asian Journal (2010), 5 (11), 2355-2357CODEN: CAAJBI; ISSN:1861-4728. (Wiley-VCH Verlag GmbH & Co. KGaA)A comparison of electrochem. response of single, few- and multilayered graphene sheets was carried out and there in no significant difference between them in terms of voltammetric behavior. It appears that there is no need for single-layer graphene sheets for electrochem. applications. These is consistent with our observation that multilayered graphene nanoribbons exhibit a similar capacitance as the few-layer and single-layer graphene counter parts. The electrochem. oxidn. of dopamine and ascorbic acid on there electrodes was compared.
- 22Xie, X.; Zhao, K.; Xu, X.; Zhao, W.; Liu, S.; Zhu, Z.; Li, M.; Shi, Z.; Shao, Y. Study of Heterogeneous Electron Transfer on the Graphene/Self-Assembled Monolayer Modified Gold Electrode by Electrochemical Approaches J. Phys. Chem. C 2010, 114, 14243– 14250
- 23De, S.; Coleman, J. N. Are There Fundamental Limitations on the Sheet Resistance and Transmittance of Thin Graphene Films? ACS Nano 2010, 4, 2713– 2720[ACS Full Text
], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXksFeqtbY%253D&md5=775c95a20910210fcadd419ddd8ce215Are There Fundamental Limitations on the Sheet Resistance and Transmittance of Thin Graphene Films?De, Sukanta; Coleman, Jonathan N.ACS Nano (2010), 4 (5), 2713-2720CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)From published transmittance and sheet resistance data, we have calcd. a figure of merit for transparent, conducting graphene films; the DC to optical cond. ratio, σDC/σOp. For most reported results, this cond. ratio clusters around the values σDC/σOp = 0.7, 4.5, and 11. We show that these represent fundamental limiting values for networks of graphene flakes, undoped graphene stacks, and graphite films, resp. The limiting value for graphene flake networks is much too low for transparent-electrode applications. For graphite, a cond. ratio of 11 gives Rs = 377Ω/.box. for T = 90%, far short of the 10 Ω/.box. min. requirement for transparent conductors in current driven applications. However, we suggest that substrate-induced doping can potentially increase the 2-dimensional DC cond. enough to make graphene a viable transparent conductor. We show that four randomly stacked graphene layers can display T ≈ 90% and 10 Ω/.box. if the product of carrier d. and mobility reaches nμ = 1.3 × 1017 V-1 s-1. Given achieved doping values and attainable mobilities, this is just possible, resulting in potential values of σDC/σOp of up to 330. This is high enough for any transparent conductor application. - 24Zhang, B.; Fan, L.; Zhong, H.; Liu, Y.; Chen, S. Graphene Nanoelectrodes: Fabrication and Size-Dependent Electrochemistry J. Am. Chem. Soc. 2013, 135, 10073– 10080[ACS Full Text
], [CAS], Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXpsFWku7s%253D&md5=0dbeaa45d7c9cdd00e059d19302b8606Graphene Nanoelectrodes: Fabrication and Size-Dependent ElectrochemistryZhang, Bo; Fan, Lixin; Zhong, Huawei; Liu, Yuwen; Chen, ShengliJournal of the American Chemical Society (2013), 135 (27), 10073-10080CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The fabrication and electrochem. of a new class of graphene electrodes are presented. Through high-temp. annealing of hydrazine-reduced graphene oxides followed by high-speed centrifugation and size-selected ultrafiltration, flakes of reduced graphene oxides (r-GOs) of nanometer and submicrometer dimensions, resp., were obtained and sepd. from the larger ones. Using n-dodecanethiol-modified Au ultramicroelectrodes of appropriately small sizes, quick dipping in dil. suspensions of these small r-GOs allows attachment of only a single flake on the thiol monolayer. The electrodes thus fabricated were used to study the heterogeneous electron transfer (ET) kinetics at r-GOs and the nanoscopic charge transport dynamics at electrochem. interfaces. The r-GOs exhibit similarly high activity for electrochem. ET reactions to metal electrodes. Voltammetric anal. for the relatively slow ET reaction of Fe(CN)63- redn. produces slightly higher ET rate consts. at r-GOs of nanometer sizes than at large ones. These ET kinetic features are in accordance with the defect-dominant nature of the r-GOs and the increased defect d. in the nanometer-sized flakes as revealed by Raman spectroscopic measurements. The voltammetric enhancement and inhibition for the redn. of Ru(NH3)63+ and Fe(CN)63-, resp., at r-GO flakes of submicrometer and nanometer dimensions upon removal of supporting electrolyte significantly deviate in magnitude from those predicted by the electroneutrality-based electromigration theory, which may evidence the increased penetration of the diffuse double layer into the mass transport layer at nanoscopic electrochem. interfaces. - 25Ambrosi, A.; Bonanni, A.; Pumera, M. Electrochemistry of Folded Graphene Edges Nanoscale 2011, 3, 2256– 2260Google ScholarThere is no corresponding record for this reference.
- 26Brownson, D. A. C.; Banks, C. E. Cvd Graphene Electrochemistry: The Role of Graphitic Islands Phys. Chem. Chem. Phys. 2011, 13, 15825– 15828[Crossref], [PubMed], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVKjsr%252FE&md5=2023934a1cb6dd1a1b1a95e15009a553CVD graphene electrochemistry: the role of graphitic islandsBrownson, Dale A. C.; Banks, Craig E.Physical Chemistry Chemical Physics (2011), 13 (35), 15825-15828CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Graphitic islands are shown to dominate the electrochem. response at CVD grown graphene electrodes.
- 27Valota, A. T.; Toth, P. S.; Kim, Y. J.; Hong, B. H.; Kinloch, I. A.; Novoselov, K. S.; Hill, E. W.; Dryfe, R. A. W. Electrochemical Investigation of Chemical Vapour Deposition Monolayer and Bilayer Graphene on the Microscale Electrochim. Acta 2013, 110, 9– 15Google ScholarThere is no corresponding record for this reference.
- 28Tan, C.; Rodríguez-López, J.; Parks, J. J.; Ritzert, N. L.; Ralph, D. C.; Abruña, H. D. Reactivity of Monolayer Chemical Vapor Deposited Graphene Imperfections Studied Using Scanning Electrochemical Microscopy ACS Nano 2012, 6, 3070– 3079
- 29Ritzert, N. L.; Rodríguez-López, J.; Tan, C.; Abruña, H. D. Kinetics of Interfacial Electron Transfer at Single-Layer Graphene Electrodes in Aqueous and Nonaqueous Solutions Langmuir 2013, 29, 1683– 1694[ACS Full Text
], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXntVSrtQ%253D%253D&md5=8f8d99c4dac93ca5fb39c431598f3676Kinetics of Interfacial Electron Transfer at Single-Layer Graphene Electrodes in Aqueous and Nonaqueous SolutionsRitzert, Nicole L.; Rodriguez-Lopez, Joaquin; Tan, Cen; Abruna, Hector D.Langmuir (2013), 29 (5), 1683-1694CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The authors present a catalog of electron transfer mediators for studying the heterogeneous electron transfer kinetics of large-area, single-layer graphene electrodes. Scanning electrochem. microscopy (SECM) was used to probe the apparent std. electron transfer rate const. of mediators in aq. solns. and in MeCN and DMF, allowing for studies of graphene electroactivity at different potentials and in both aq. and nonaq. media. In aq. soln., Fe(III) EDTA, hexacyanoruthenate(II), hexacyanoferrate(II), hexacyanoferrate(III), octacyanomalybdate(IV), Co(III) sepulchrate, and hydroxymethylferrocene exhibited quasi-reversible electron transfer behavior. The electron transfer kinetics of hexaammineruthenium(III), Me viologen, and tris(2,2'-bipyridyl)ruthenium(II) are reversible in these studies. The electron transfer rate const. of hydroxymethylferrocene and ferrocene, in org. media, was similar to that for hydroxymethylferrocene in H2O, which, although fast, shows clear kinetic complications that the authors believe are inherent to graphene. Viologens, known to be reversible at metal electrodes, exhibited quasi-reversible electron transfer. For [Co(dapa)2]2+, where dapa is 2,6-bis[1-(phenylimino)ethyl]pyridine, in DMF, the oxidn. state of the redox pair studied affected the obsd. kinetics. Under similar exptl. conditions, the Co(I/II) couple exhibited nearly reversible behavior whereas Co(II/III) had finite kinetics. This behavior was ascribed to the large difference in self-exchange rates for these two processes. To demonstrate the utility of using these mediators for examg. graphene electrodes, the kinetics of two mediators with quasi-reversible electron transfer behavior, Fe EDTA and hexacyanoruthenate, were measured in the presence of a redox-active species [Os(bpy)2(dipy)Cl]PF6, where bpy is 2,2'-bipyridine and dipy is 4,4'-trimethylenedipyridine, adsorbed onto the graphene surface. The kinetics of both mediators were enhanced in the presence of 1-hundredth of a monolayer of the Os complex, showing that even small amts. of impurities on the graphene surface are capable of enhancing the obsd. kinetics. - 30Güell, A. G.; Ebejer, N.; Snowden, M. E.; MacPherson, J. V.; Unwin, P. R. Structural Correlations in Heterogeneous Electron Transfer at Monolayer and Multilayer Graphene Electrodes J. Am. Chem. Soc. 2012, 134, 7258– 7261
- 31Nicholson, R. S. Theory and Application of Cyclic Voltammetry for Measurement of Electrode Reaction Kinetics Anal. Chem. 1965, 37, 1351– 1355[ACS Full Text
], [CAS], Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF28XisFSksQ%253D%253D&md5=7f3073eb040d007e31d8989539fe8dceTheory and application of cyclic voltammetry for measurement of electrode reaction kineticsNicholson, Richard S.(1965), 37 (11), 1351-5CODEN: ANCHAM; ISSN:0003-2700.The theory of cyclic voltammetry is extended to include electron transfer reactions described by the electrochem. abs. rate equation. By use of numerical analysis, it is shown that a system which appears reversible at one frequency may be made to exhibit kinetic behavior at higher frequencies as indicated by increased sepn. of cathodic and anodic peak potentials. The standard rate const. for electron transfer is detd. from this peak potential sepn. and frequency. The redn. of Cd++ is used as an illustration. - 32Klingler, R. J.; Kochi, J. K. Electron-Transfer Kinetics from Cyclic Voltammetry. Quantitative Description of Electrochemical Reversibility J. Phys. Chem. 1981, 85, 1731– 1741[ACS Full Text
], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3MXktFGisr0%253D&md5=56df69cc55692b72e2b4881b11fb8995Electron-transfer kinetics from cyclic voltammetry. Quantitative description of electrochemical reversibilityKlingler, R. J.; Kochi, J. K.Journal of Physical Chemistry (1981), 85 (12), 1731-41CODEN: JPCHAX; ISSN:0022-3654.The measurement of the heterogeneous rate consts. for electron transfer from std. cyclic-voltammetric (CV) data is described. A variety of organometals were used as the electroactive species in which the forward electron transfer is unidirectional, i.e., totally irreversible. The heterogeneous rate consts. for the anodic process are quant. correlated with electron-transfer rate consts. obtained in homogeneous soln. with a variety of chem. oxidants. Since the CV method derives from a totally irreversible electrode process, a quant. measure of electrochem. reversibility was developed. The reversibility factor fr is a continuous function of the electrode kinetics, varying smoothly from fr = 1 for Nernstian behavior to fr = 0 for total irreversibility. The theor. and exptl. limits of error encountered in the application of the CV method were quant. evaluated by the reversibility factor fr. - 33Randles, J. E. B. A Cathode Ray Polarograph. Part II. The Current-Voltage Curves Trans. Faraday Soc. 1948, 44, 327– 338[Crossref], [CAS], Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaH1MXitF2h&md5=df554684034a19783951152a4ea3f42cCathode-ray polarograph. II. Current-voltage curvesRandles, J. E. B.Transactions of the Faraday Society (1948), 44 (), 327-38CODEN: TFSOA4; ISSN:0014-7672.A microelectrode immersed in a soln. contg. small amts. of electro-reducible or -oxidizable substances can be subjected to a fairly rapidly changing potential and the corresponding changes in the electrode current recorded on the screen of a cathode-ray tube. The diffusion current-voltage curve so obtained shows a sharp max. of the current corresponding to the onset of each electro-reduction or -oxidation. The theory of the diffusion process under these conditions is discussed, and a graphic solution is obtained for the case that the electrode reaction occurs reversibly, and that the reactants and products are sol. either in the aq. medium or the electrode material (which may be Hg). Good agreement between theoretical and exptl. curves is obtained. Photographs of exptl. cathode-ray traces show the effect on the current-voltage curves of slowness of the electrode reaction (irreversible electrode process), of variation in the rate of change of potential of the electrode, and of phenomena similar to polarographic maxima. Exptl. data are presented which indicate a strict proportionality between the concn. of a substance which reacts at the electrode, and the value of the corresponding diffusion current at its max. The cathode-ray polarograph can therefore be used for analytical purposes.
- 34Bard, A. J.; Faulkner, L. R. Electrochemical Methods. Fundamentals and Applications, 2nd ed.; John Wiley & Sons, Inc.: New York, 2001.Google ScholarThere is no corresponding record for this reference.
- 35Patel, A. N.; Collignon, M. G.; Oconnell, M. A.; Hung, W. O. Y.; McKelvey, K.; MacPherson, J. V.; Unwin, P. R. A New View of Electrochemistry at Highly Oriented Pyrolytic Graphite J. Am. Chem. Soc. 2012, 134, 20117– 20130[ACS Full Text
], [CAS], Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xhs1GrurvL&md5=d38b8f7b501d3ff1d4c9a5976867ddbbA New View of Electrochemistry at Highly Oriented Pyrolytic GraphitePatel, Anisha N.; Collignon, Manon Guille; O Connell, Michael A.; Hung, Wendy O. Y.; McKelvey, Kim; Macpherson, Julie V.; Unwin, Patrick R.Journal of the American Chemical Society (2012), 134 (49), 20117-20130CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Major new insights on electrochem. processes at graphite electrodes are reported, following extensive studies of two of the most studied redox couples, Fe(CN)64-/3- and Ru(NH3)63+/2+. Expts. were carried out on five different grades of highly oriented pyrolytic graphite (HOPG) that vary in step-edge height and surface coverage. Significantly, the same electrochem. characteristic is obsd. on all surfaces, independent of surface quality: initial cyclic voltammetry (CV) is close to reversible on freshly cleaved surfaces (>400 measurements for Fe(CN)64-/3- and >100 for Ru(NH3)63+/2+), in marked contrast to previous studies that found very slow electron transfer (ET) kinetics, with an interpretation that ET only occurs at step edges. Significantly, high spatial resoln. electrochem. imaging with scanning electrochem. cell microscopy, on the highest quality mech. cleaved HOPG, demonstrates definitively that the pristine basal surface supports fast ET, and that ET is not confined to step edges. However, the history of the HOPG surface strongly influences the electrochem. behavior. Thus, Fe(CN)64-/3- shows markedly diminished ET kinetics with either extended exposure of the HOPG surface to the ambient environment or repeated CV measurements. In situ at. force microscopy (AFM) reveals that the deterioration in apparent ET kinetics is coupled with the deposition of material on the HOPG electrode, while conducting-AFM highlights that, after cleaving, the local surface cond. of HOPG deteriorates significantly with time. These observations and new insights are not only important for graphite, but have significant implications for electrochem. at related C materials such as graphene and C nanotubes. - 36Edwards, M. A.; Bertoncello, P.; Unwin, P. R. Slow Diffusion Reveals the Intrinsic Electrochemical Activity of Basal Plane Highly Oriented Pyrolytic Graphite Electrodes J. Phys. Chem. C 2009, 113, 9218– 9223
- 37Lai, S. C. S.; Patel, A. N.; McKelvey, K.; Unwin, P. R. Definitive Evidence for Fast Electron Transfer at Pristine Basal Plane Graphite from High-Resolution Electrochemical Imaging Angew. Chem., Int. Ed. 2012, 51, 5405– 5408[Crossref], [CAS], Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xls1eisL4%253D&md5=911263889fe0dba6cf4c660485d8bf34Definitive Evidence for Fast Electron Transfer at Pristine Basal Plane Graphite from High-Resolution Electrochemical ImagingLai, Stanley C. S.; Patel, Anisha N.; McKelvey, Kim; Unwin, Patrick R.Angewandte Chemie, International Edition (2012), 51 (22), 5405-5408, S5405/1-S5405/12CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)SECCM has allowed to study ET at basal plane HOPG under conditions of very high mass transport and high spatial resoln., and where the liq. probe makes a series of fresh measurements across the surface. Authors have been able to isolate the response of the pristine basal plane (directly after cleaving, thus reflecting the intrinsic material properties), and they show unambiguously that ET is fast (close to reversible) for the two most studied redox couples. This new view which overturns more than two decades of past research not only impacts the understanding of the electroactivity of HOPG, but potentially the properties of related sp2 materials, such as carbon nanotubes and graphene, illustrating the importance of the findings. The studies also demonstrate the significant potential of SECCM as a new nanoscale probe of electrochem. and interfacial processes.
- 38Banks, C. E.; Davies, T. J.; Wildgoose, G. G.; Compton, R. G. Electrocatalysis at Graphite and Carbon Nanotube Modified Electrodes: Edge-Plane Sites and Tube Ends Are the Reactive Sites Chem. Commun. (Cambridge, U.K.) 2005, 829– 841[Crossref], [PubMed], [CAS], Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1Kru7k%253D&md5=b8ce2a6d898db36d7724da186c62bfe9Electrocatalysis at graphite and carbon nanotube modified electrodes: edge-plane sites and tube ends are the reactive sitesBanks, Craig E.; Davies, Trevor J.; Wildgoose, Gregory G.; Compton, Richard G.Chemical Communications (Cambridge, United Kingdom) (2005), (7), 829-841CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)A review. Carbon, and particularly graphite in its various forms, is an attractive electrode material. Two areas of particular interest are modified C electrodes and C nanotube electrodes. The authors focus on the relation between surface structure and electrochem. and chem. reactivity of electrodes based on these materials. The authors overview recent work in this area which led one to believe that much of the catalytic activity, electron transfer and chem. reactivity of graphitic C electrodes is at surface defect sites, and in particular edge-plane-like defect sites. The authors also question the claimed special catalytic properties of C nanotube modified electrodes.
- 39McDermott, M. T.; Kneten, K.; McCreery, R. L. Anthraquinonedisulfonate Adsorption, Electron-Transfer Kinetics, and Capacitance on Ordered Graphite Electrodes: The Important Role of Surface Defects J. Phys. Chem. 1992, 96, 3124– 3130
- 40Li, Z.; Wang, Y.; Kozbial, A.; Shenoy, G.; Zhou, F.; McGinley, R.; Ireland, P.; Morganstein, B.; Kunkel, A.; Surwade, S. P.et al. Effect of Airborne Contaminants on the Wettability of Supported Graphene and Graphite Nat. Mater. 2013, 12, 925– 931[Crossref], [PubMed], [CAS], Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFCjtL7L&md5=fb8e5319415cb6d764ad4d5ec9bb2f43Effect of airborne contaminants on the wettability of supported graphene and graphiteLi, Zhiting; Wang, Yongjin; Kozbial, Andrew; Shenoy, Ganesh; Zhou, Feng; McGinley, Rebecca; Ireland, Patrick; Morganstein, Brittni; Kunkel, Alyssa; Surwade, Sumedh P.; Li, Lei; Liu, HaitaoNature Materials (2013), 12 (10), 925-931CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)It is generally accepted that supported graphene is hydrophobic and that its water contact angle is similar to that of graphite. The authors show that the water contact angles of freshly prepd. supported graphene and graphite surfaces increase when they are exposed to ambient air. By using IR spectroscopy and XPS, the authors demonstrate that airborne hydrocarbons adsorb on graphitic surfaces, and that a concurrent decrease in the water contact angle occurs when these contaminants are partially removed by both thermal annealing and controlled UV-O3 treatment. Graphitic surfaces are more hydrophilic than previously believed, and these results suggest that previously reported data on the wettability of graphitic surfaces may have been affected by unintentional hydrocarbon contamination from ambient air.
- 41Hardcastle, T. P.; Seabourne, C. R.; Zan, R.; Brydson, R. M. D.; Bangert, U.; Ramasse, Q. M.; Novoselov, K. S.; Scott, A. J. Mobile Metal Adatoms on Single Layer, Bilayer, and Trilayer Graphene: An ab Initio DFT Study with van der Waals Corrections Correlated with Electron Microscopy Data Phys. Rev. B: Condens. Matter Mater. Phys. 2013, 87Google ScholarThere is no corresponding record for this reference.
- 42Zan, R.; Ramasse, Q. M.; Bangert, U.; Novoselov, K. S. Graphene Reknits Its Holes Nano Lett. 2012, 12, 3936– 3940[ACS Full Text
], [CAS], Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XpvVKlsLk%253D&md5=d45e6e40ff5388426ae04597f0b1b701Graphene Reknits Its HolesZan, Recep; Ramasse, Quentin M.; Bangert, Ursel; Novoselov, Konstantin S.Nano Letters (2012), 12 (8), 3936-3940CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Nanoholes, etched under an electron beam at room temp. in single-layer graphene sheets as a result of their interaction with metal impurities, are shown to heal spontaneously by filling up with either nonhexagon, graphene-like, or perfect hexagon 2D structures. Scanning transmission electron microscopy was employed to capture the healing process and study atom-by-atom the regrown structure. A combination of these nanoscale etching and reknitting processes could lead to new graphene tailoring approaches. - 43Rooney, M. B.; Coomber, D. C.; Bond, A. M. Achievement of Near-Reversible Behavior for the [Fe(CN)6]3–/4– Redox Couple Using Cyclic Voltammetry at Glassy Carbon, Gold, and Platinum Macrodisk Electrodes in the Absence of Added Supporting Electrolyte Anal. Chem. 2000, 72, 3486– 3491
- 44Meyer, J. C.; Geim, A. K.; Katsnelson, M. I.; Novoselov, K. S.; Booth, T. J.; Roth, S. The Structure of Suspended Graphene Sheets Nature 2007, 446, 60– 63[Crossref], [PubMed], [CAS], Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXit1arsLs%253D&md5=b15d9e9c829cd3cb83d96c4e04b2f335The structure of suspended graphene sheetsMeyer, Jannik C.; Geim, A. K.; Katsnelson, M. I.; Novoselov, K. S.; Booth, T. J.; Roth, S.Nature (London, United Kingdom) (2007), 446 (7131), 60-63CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)The recent discovery of graphene has sparked much interest, thus far focused on the peculiar electronic structure of this material, in which charge carriers mimic massless relativistic particles. However, the phys. structure of graphene-a single layer of carbon atoms densely packed in a honeycomb crystal lattice-is also puzzling. On the one hand, graphene appears to be a strictly two-dimensional material, exhibiting such a high crystal quality that electrons can travel submicrometre distances without scattering. However, perfect two-dimensional crystals cannot exist in the free state, according to both theory and expt. This incompatibility can be avoided by arguing that all the graphene structures studied so far were an integral part of larger three-dimensional structures, either supported by a bulk substrate or embedded in a three-dimensional matrix. Here the authors report on individual graphene sheets freely suspended on a microfabricated scaffold in vacuum or air. These membranes are only one atom thick, yet they still display long-range cryst. order. However, the authors' studies by TEM also reveal that these suspended graphene sheets are not perfectly flat: they exhibit intrinsic microscopic roughening such that the surface normal varies by several degrees and out-of-plane deformations reach 1 nm. The atomically thin single-crystal membranes offer ample scope for fundamental research and new technologies, whereas the obsd. corrugations in the 3rd dimension may provide subtle reasons for the stability of two-dimensional crystals.
- 45Wang, Q. H.; Jin, Z.; Kim, K. K.; Hilmer, A. J.; Paulus, G. L. C.; Shih, C. J.; Ham, M. H.; Sanchez-Yamagishi, J. D.; Watanabe, K.; Taniguchi, T.et al. Understanding and Controlling the Substrate Effect on Graphene Electron-Transfer Chemistry via Reactivity Imprint Lithography Nat. Chem. 2012, 4, 724– 732[Crossref], [PubMed], [CAS], Google Scholar45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFOgtrbM&md5=9cae91dfb1930855e06a54d1df3396edUnderstanding and controlling the substrate effect on graphene electron-transfer chemistry via reactivity imprint lithographyWang, Qing Hua; Jin, Zhong; Kim, Ki Kang; Hilmer, Andrew J.; Paulus, Geraldine L. C.; Shih, Chih-Jen; Ham, Moon-Ho; Sanchez-Yamagishi, Javier D.; Watanabe, Kenji; Taniguchi, Takashi; Kong, Jing; Jarillo-Herrero, Pablo; Strano, Michael S.Nature Chemistry (2012), 4 (9), 724-732CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Graphene has exceptional electronic, optical, mech. and thermal properties, which provide it with great potential for use in electronic, optoelectronic and sensing applications. The chem. functionalization of graphene was studied with a view to controlling its electronic properties and interactions with other materials. Covalent modification of graphene by org. diazonium salts was used to achieve these goals, but because graphene comprises only a single at. layer, it is strongly influenced by the underlying substrate. Here, the authors show a Stark difference in the rate of electron-transfer reactions with org. diazonium salts for monolayer graphene supported on a variety of substrates. Reactions proceed rapidly for graphene supported on SiO2 and Al2O3 (sapphire), but negligibly on alkyl-terminated and hexagonal boron nitride (hBN) surfaces, as shown by Raman spectroscopy. The authors also develop a model of reactivity based on substrate-induced electron-hole puddles in graphene, and achieve spatial patterning of chem. reactions in graphene by patterning the substrate.
- 46Elias, D. C.; Nair, R. R.; Mohiuddin, T. M. G.; Morozov, S. V.; Blake, P.; Halsall, M. P.; Ferrari, A. C.; Boukhvalov, D. W.; Katsnelson, M. I.; Geim, A. K.et al. Control of Graphene’s Properties by Reversible Hydrogenation: Evidence for Graphane Science 2009, 323, 610– 613Google ScholarThere is no corresponding record for this reference.
- 47Pierce, C.; Ewing, B. Localized Adsorption on Graphite Surfaces J. Phys. Chem. 1967, 71, 3408– 3413
- 48Schedin, F.; Geim, A. K.; Morozov, S. V.; Hill, E. W.; Blake, P.; Katsnelson, M. I.; Novoselov, K. S. Detection of Individual Gas Molecules Adsorbed on Graphene Nat. Mater. 2007, 6, 652– 655[Crossref], [PubMed], [CAS], Google Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXpvFKjsrs%253D&md5=dedbfc7b95a13316bcbb8ebc5956c1d3Detection of individual gas molecules adsorbed on grapheneSchedin, F.; Geim, A. K.; Morozov, S. V.; Hill, E. W.; Blake, P.; Katsnelson, M. I.; Novoselov, K. S.Nature Materials (2007), 6 (9), 652-655CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)Authors show that micrometre-size sensors made from graphene are capable of detecting individual events when a gas mol. attaches to or detaches from graphene's surface. The adsorbed mols. change the local carrier concn. in graphene one by one electron, which leads to step-like changes in resistance. The achieved sensitivity is due to the fact that graphene is an exceptionally low-noise material electronically, which makes it a promising candidate not only for chem. detectors but also for other applications where local probes sensitive to external charge, magnetic field or mech. strain are required.
- 49Davies, T. J.; Moore, R. R.; Banks, C. E.; Compton, R. G. The Cyclic Voltammetric Response of Electrochemically Heterogeneous Surfaces J. Electroanal. Chem. 2004, 574, 123– 152[Crossref], [CAS], Google Scholar49https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXps1Oqsbs%253D&md5=ea55c8ee14ae44d03bad09bdd9874aa7The cyclic voltammetric response of electrochemically heterogeneous surfacesDavies, Trevor J.; Moore, Ryan R.; Banks, Craig E.; Compton, Richard G.Journal of Electroanalytical Chemistry (2004), 574 (1), 123-152CODEN: JECHES ISSN:. (Elsevier B.V.)The cyclic voltammetric response of an electrode composed of 2 different electrode materials is modeled using finite difference simulations. The system can be thought of as an array of microelectrodes of one material dispersed over a different electrode material. First, a detailed study into the diffusional effects which arise when the distance between the individual microelectrodes is varied, leads to a simple method with which to obtain qual. data regarding the size of the different electrode materials and diffusion layer thickness. Second, a more quant. method is employed to det. the fractional coverage and no. of Au particles on an anthraquinone modified edge plane pyrolytic graphite electrode by comparing exptl. peak to peak sepns. with simulated working curves. The results are compared with a scanning electron microscope anal. of the same electrode surface. Third, the diffusion domain approach is applied to the basal plane highly ordered pyrolytic graphite (HOPG) surface in an attempt to explain the characteristic shapes of basal plane HOPG voltammograms. A method is presented for the approx. detn. of surface defect d., using macroelectrode cyclic voltammetry, and then trialled on a no. of different redox couples. The results are compared with 2 previous scanning tunneling microscopy studies of basal plane HOPG.
- 50Blake, P.; Hill, E. W.; Castro Neto, A. H.; Novoselov, K. S.; Jiang, D.; Yang, R.; Booth, T. J.; Geim, A. K. Making Graphene Visible Appl. Phys. Lett. 2007, 91Google ScholarThere is no corresponding record for this reference.
- 51Ferrari, A. C. Raman Spectroscopy of Graphene and Graphite: Disorder, Electron-Phonon Coupling, Doping and Nonadiabatic Effects Solid State Commun. 2007, 143, 47– 57[Crossref], [CAS], Google Scholar51https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXmt1yhtr0%253D&md5=b67986a7f5f92c4a5ab64950f3330d7aRaman spectroscopy of graphene and graphite: Disorder, electron-phonon coupling, doping and nonadiabatic effectsFerrari, Andrea C.Solid State Communications (2007), 143 (1-2), 47-57CODEN: SSCOA4; ISSN:0038-1098. (Elsevier Ltd.)The authors review recent work on Raman spectroscopy of graphite and graphene. The authors focus on the origin of the D and G peaks and the 2nd order of the D peak. The G and 2 D Raman peaks change in shape, position and relative intensity with no. of graphene layers. This reflects the evolution of the electronic structure and electron-phonon interactions. The authors then consider the effects of doping on the Raman spectra of graphene. The Fermi energy is tuned by applying a gate-voltage. This induces a stiffening of the Raman G peak for both holes and electrons doping. Thus Raman spectroscopy can be efficiently used to monitor no. of layers, quality of layers, doping level and confinement.
- 52Malard, L. M.; Pimenta, M. A.; Dresselhaus, G.; Dresselhaus, M. S. Raman Spectroscopy in Graphene Phys. Rep. 2009, 473, 51– 87[Crossref], [CAS], Google Scholar52https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXkvVSlt7o%253D&md5=12bf1e7387b80149aa99cd1a9c14a6d2Raman spectroscopy in grapheneMalard, L. M.; Pimenta, M. A.; Dresselhaus, G.; Dresselhaus, M. S.Physics Reports (2009), 473 (5-6), 51-87CODEN: PRPLCM; ISSN:0370-1573. (Elsevier B.V.)A review. Recent Raman scattering studies in different types of graphene samples are reviewed here. We first discuss the first-order and the double resonance Raman scattering mechanisms in graphene, which give rise to the most prominent Raman features. The detn. of the no. of layers in few-layer graphene is discussed, giving special emphasis to the possibility of using Raman spectroscopy to distinguish a monolayer from few-layer graphene stacked in the Bernal (AB) configuration. Different types of graphene samples produced both by exfoliation and using epitaxial methods are described and their Raman spectra are compared with those of 3D cryst. graphite and turbostratic graphite, in which the layers are stacked with rotational disorder. We show that Resonance Raman studies, where the energy of the excitation laser line can be tuned continuously, can be used to probe electrons and phonons near the Dirac point of graphene and, in particular allowing a detn. to be made of the tight-binding parameters for bilayer graphene. The special process of electron-phonon interaction that renormalizes the phonon energy giving rise to the Kohn anomaly is discussed, and is illustrated by gated expts. where the position of the Fermi level can be changed exptl. Finally, we discuss the ability of distinguishing armchair and zig-zag edges by Raman spectroscopy and studies in graphene nanoribbons in which the Raman signal is enhanced due to resonance with singularities in the d. of electronic states.
- 53Walker, P. L.; McKinstry, H. A.; Wright, C. C. X-Ray Diffraction Studies of a Graphitized Carbon—Changes in Interlayer Spacing and Binding Energy with Temperature Ind. Eng. Chem. 1953, 45, 1711– 1715
Supporting Information
Supporting Information
ARTICLE SECTIONSMicropipette preparation, reference electrode potential determination, Nicholson method, cyclic voltammetry fitting, mediator-free blank voltammetry, AFM of the stable and collapsed microdroplets, flake preparation procedure, determination of the redox mediator diffusion coefficients, kinetics-droplet size correlation, comparison of the raw and analyzed kinetic data, uncompensated resistance, comparison of electrode kinetics on basal and edge plane of graphite, and X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) analysis of atmosphere-aged and freshly cleaved graphite surface. This material is available free of charge via the Internet at http://pubs.acs.org.
Terms & Conditions
Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.



