A Case Study 2
“liquid phase exfoliation”:
Abstract: “Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. Two main routes are possible: largescale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to 0.01 mg ml-1, produced by dispersion and exfoliation of graphite in organic solvents such as N-methyl-pyrrolidone. This is possible because the energy required to exfoliate graphene is balanced by the solvent–graphene interaction for solvents whose surface energies match that of graphene. We confirm the presence of individual graphene sheets by …… Our method results in a monolayer yield of 1 wt%, which could potentially be improved to 7–12 wt% with further processing. The absence of defects or oxides is confirmed by ……We are able to produce semi-transparent conducting films and conducting composites. Solution processing of graphene opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry.”
(X-ray fluorescence, Z>4)
Example: D. Wei et al., “Synthesis of N-Doped Graphene by Chemical Vapor Deposition and Its Electrical Properties”,Nano Lett., 2009, 9, 1752
• EELS/HREELS (electron energy loss)
– EELS (often in TEM) similar to XPS – elemental/chemical
A. Dato et al., Nano Lett., 2008, 8 (7), pp 2012–2016
H. Yanagisawa et al., Surface and Interface Analysis 37, 133 (2005) R J Koch, P hys. Status Solidi C 7, No. 2, 394–397 (2010)
STM based IETS
Inelastic electron tunneling spectroscopy
/~wilsonho/wilsonho.html Inducing and Viewing the Rotational Motion of a Single Molecule. Science 1998, 279, 1907. B.C. Stipe, M.A. Rezaei, and W. Ho. Single-Molecule Vibrational Spectroscopy and Microscopy. Science 1998, 280, 1732. B.C. Stipe, M.A. Rezaei, and W. Ho.
D. A. Mueller et al., Atomic-Scale Chemical Imaging of Composition and Bonding by Aberration-Corrected Microscopy, Science, 319. 1073 (2008) F. Carbone et al., Science 325, 181 (2009) –time resolved Reviews: S.J. Pennycook et al., Atomic-resolution spectroscopic imaging: past, present and future, Journal of Electron Microscopy 58(3): 87–97 (2009) K.W. Urban, Studying Atomic Structures by Aberration-Corrected Transmission Electron Microscopy Science 321, 506 (2008)
Case Study
Nature Nanotechnology 3, 563 - 568 (2008)
Optical Absorption/Transmission & Graphite Dispersion Concentration
EM
TEM
Raman & XPS
Discussion
Angle resolved photoemission spectroscopy (ARPES)
•X-ray vs UV (energy scale) •Atomic vs solid •ARPES measures electronic excitations • in solid band structure
– Can measure chemical bonding and phonon spectrum (HREELS)
• Optical • SPM • Electrical Transport
What about Grand Challenge?
ueV
Many body/collective
100nm
/research_arpesoverview.html
What do you think/questions
• Growth mechanisms? • Other gases (other than Ar?) --- Si-X collision and evaporation temperatures • …
(UV)
/wiki/ARPES
Applications in graphene: A. Bostwick et al., Nature Phys. 3, 38 (2007) SY Zhou et al., Nature Materials 7, 259 - 260 (2008) P Sutter et al., Nano Lett 9, 2654 (2009)
Methods: The graphite was dispersed in the relevant solvent (cylindrical vial, 10-25 ml solvent) at a concentration of 0.1 mg/ml by sonicating in a low power sonic bath (Model Ney Ultrasonic) for 30 minutes. Care must be taken as excessive sonication can lead to destruction of the graphene. The resultant dispersion was then centrifuged (CF) using a Hettich Mikro 22R centrifuge for 90 minutes at 500 rpm. After CF, decantation was carried out by pipetting off the top half of the dispersion. … Thin films were prepared by vacuum filtration onto either polyvinylidene fluoride (PVDF) membranes (pore size: 100 nm) or porous alumina membranes (pore size: 20 nm). Initial sample drying was carried out in a vacuum oven at room temperature at a pressure of ~10-3 mbar. Subsequently, in some cases, annealing was carried out to remove residual solvent using a vacuum tube furnace from GERO Hochtemperaturöfen GmbH. The samples were heated to 400C for 4 hours in either vacuum or forming gas. Samples for … were prepared by spraying th e graphene dispersions onto silicon dioxide substrates using an Evolution Airbrush () spray gun. The solvent was removed by annealing under forming gas at 400 degrees for 4 hours.