JPK Instruments, a world-leading manufacturer of
nanoanalytic instrumentation for research in life sciences and soft matter,
reports on a keynote paper in Nano Letters where Dr Nikolai Severin and his
co-workers from the group of Professor Jürgen P. Rabe have applied JPK's
NanoWizard®II Ultra system to improve their understanding of the properties of
graphene.
The Physics of Macromolecules group of Professor Jürgen P. Rabe has a central
research goal to correlate structure and dynamics of molecular systems at
interfaces with mechanical, electronic, optical and (bio-)chemical properties from
molecular to macroscopic length and time scales. Manipulation and imaging of
single molecules and supramolecular systems with a scanning force microscope
(SFM) is of paramount importance to the understanding of structure formation
and the measurement of mechanical properties. The group is also involved in
understanding and developing molecular electronics and organic electronic
properties.
Within this group is Dr Nikolai Severin, recently the lead author of a paper in
Nano Letters* which shows the use of AFM in the study of graphenes. The
electronic properties of graphenes depend sensitively on their deformation, and
therefore strain-engineered graphene electronics is envisioned. In order to
deform graphenes locally, the group has mechanically exfoliated single and few
layer graphenes onto atomically flat mica surfaces covered with isolated double
stranded plasmid DNA rings. Using scanning force microscopy in both contact and
intermittent contact modes, they have found that the graphenes replicate the topography
of the underlying DNA with high precision. The availability of macromolecules
of different topologies, e.g., programmable DNA patterns render this approach
promising for new graphene based device designs. Furthermore, the encapsulation
of single macromolecules offers new prospects for analytical scanning probe
microscopy techniques.
Dr Severin has seen that graphene provides enhanced protection of DNA molecules
to shear forces exerted during scanning force microscopy in contact mode. In
addition, graphene will act as a surface protective layer against the ambient,
e.g., against oxidation, since it is impermeable to gases. Taking into account
both the high electric conductivity of graphene and its extremely small
thickness, this offers new opportunities for scanning probe microscopies and
spectroscopies, such as scanning tunneling or tip enhanced Raman spectroscopy
for analyses of both locally deformed graphene and confined molecules.
Summarising, Dr Severin said, "We have successfully demonstrated that
topography of graphenes can be controlled with the precision down to single
molecules, i.e. graphenes are so flexible that they can replicate the
topography of single molecules, when deposited on these molecules."
He also commented on some of the reasons for choosing to work with JPK
NanoWizard® II for this work: "We are able to use a relatively large size
of samples and scan areas of up to 30 microns. The linearized scanner is most
important for us to precisely measure the height of DNA and their cross
sections. The system shows little thermal drift which is important when making
measurements on such small length scales. I also found the software was quite
easy to use."
For more details about JPK's specialist products and applications for the bio and
nano sciences, please contact JPK on +49 30533112070, visit the web site:
http://www.jpk.com/
or see more on Facebook:
www.jpk.com/facebook
* Reference acknowledgment:
Replication of Single Macromolecules with Graphene, N . Severin*†, M. Dorn†, A.
Kalachev‡, and J. P. Rabe*†;†Department of Physics, Humboldt-Universitaat zu
Berlin, Newtonstrasse 15, 12489 Berlin, Germany. ‡ PlasmaChem GmbH, Rudower
Chaussee 29, 12489 Berlin, Germany: Nano Lett., 2011, 11 (6), pp 2436-2439;
DOI: 10.1021/nl200846f; Publication Date (Web): May 16, 2011; Copyright © 2011
American Chemical Society
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