70 MICROSCOPY & IMAGING
Report on how researchers at the Free University of Berlin are using atomic force microscopy (AFM) to study carbon-based nanoparticles (from graphene sheets)
FORCE for M
anufacturer of nanoanalytic instrumentation for research in life sciences and soft matter, JPK
Instruments, reports on the research of the Eigler Group in the Institute for Chemistry & Biochemistry at the Free University of Berlin. T e team is studying carbon-based nanoparticles with JPK’s NanoWizard Ultra Speed AFM system as part of a development of new bio-electrical devices. PhD student, Christian Halbig, is a member of the research group led by Professor Dr Siegfried Eigler at the Institute of Chemistry & Biochemistry at the Free University of Berlin (FUB). T e group is focused on the preparation and characterisation of carbon-based nanoparticles. T ey mainly use single layered graphene sheets obtained from graphene oxide that are then modifi ed by diff erent functionalisation techniques. T ese synthesised nanoparticles are then further tested for biological and technical applications in, for example, electrical devices.
AFM is one of the main tools used to
have a closer look at the nanoparticles. Images obtained from AFM provide detailed information about the particle size distribution from the micron scale down to nanometer-sized particles as
/Si wafers. GOOD T e AFM is a tip-scanning system
An image of a Langmuir-Blodgett fi lm of graphene imaged using the AFM
well as particle thickness before and after functionalisation. AFM is used in conjunction with 2D Raman spectroscopy and light microscopy to study graphene coated onto SiO2
Asked about the benefi ts of using the
NanoWizard Ultra Speed AFM system, Halbig says, “T e biggest benefi t of our new AFM is its programmability. It allows us to break the limits of the scanner by the automatic generation of individual small AFM images. T ese can be merged then to get large area images of coated surfaces.”
controlled by powerful software. T e cantilever is mounted onto a glass cantilever holder with an optical access from the top. With this set-up, it is possible to measure in liquids (water) as well as in air without changing the confi guration. In addition to standard imaging modes such as contact and AC, the company’s Quantitative Imaging (QI) mode is available. QI mode works by making point- to-point force-distance curves making the analysis of, for example, mechanical properties, possible. T e automated set-up allows the use of scripts to plan experiments and make statistical analysis from diff erent sample areas. T e system used at the Free University
of Berlin also includes the more specialised electrical modes such as Kelvin Probe and Conductive AFM for the determination of the work function or electrical inhomogeneities of samples.
Christian Halbig of the Eigler Group at FU-Berlin with the JPK NanoWizard Ultra Speed AFM
For more information visit
www.jpk.com
www.scientistlive.com
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