Studying Dynamic Molecular Structures in Aqueous Environment Using NTEGRA Prima Atomic Force Microscope (AFM) from NT-MDT

Topics Covered

Background
Performing AFM in Liquids
Materials and Equipment Used
Sample
AFM Equipment and Probe

Background

NT-MDT Co. was established in 1991 with the purpose to apply all accumulated experience and knowledge in the field of nanotechnology to supply researchers with the instruments suitable to solve any possible task laying in nanometer scale dimensions. The company NT-MDT was founded in Zelenograd - the center of Russian Microelectronics. The products development are based on the combination of the MEMS technology, power of modern software, use of high-end microelectronic components and precision mechanical parts. As a commercial enterprise NT-MDT Co. exists from 1993.

Performing AFM in Liquids

It's a widely spread idea that performing AFM in liquids is a rather complicated research approach. Actually, many tasks related to the investigation of molecular structures and complexes in a liquid environment claim high demands on the SPM equipment. The picture below shows an AFM scan of surfactant molecules dynamically self-assembled into parallel, hemicylindrical micelles on a hydrophobic graphite surface.

Observation of the dynamically self-assembled molecular structure in this case was a challenge. The imaging mode used is the "soft contact mode" - scanning with constant force using a very low set point. The vertical force of the probe needs to be kept as close as possible to the set point, in this case ~ 100 pN. If the force exceeds this value, the native molecular assembly will be disturbed (the periodicity of the micelles is ~5 nm.). For lower forces, the contrast vanishes. Note that the vertical topography modulation is only 0.1-0.2 nm, but still significantly above the noise level. This example shows also that NTEGRA nanolaboratory provides enough sensitivity and stability to study dynamic molecular structures in an aqueous environment.

Materials and Equipment Used

Sample

10 mM aqueous solution of cetyltrimethylammonium bromide surfactant in contact with HOPG.

AFM Equipment and Probe

AFM Equipment - NTEGRA Prima, Constant force imaging mode in liquid cell using a very low set point ("so contact mode"- force ~100pN).

AFM Probe - CSG01, 0.03 N/m

Source: "Surfactant micelles in aqueous solution: critical resolution in AFM" by Hannes Schniepp, The College of William and Mary, Williamsburg, VA, USA

For more information on this source please visit NT-MDT Co.

Date Added: Aug 11, 2009 | Updated: Jun 11, 2013
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