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
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
This information has been sourced, reviewed and adapted from materials provided by NT-MDT Spectrum Instruments.
For more information on this source, please visit NT-MDT Spectrum Instruments.