1 research outputs found
Probe–Sample Interaction-Independent Atomic Force Microscopy–Infrared Spectroscopy: Toward Robust Nanoscale Compositional Mapping
Nanoscale topological
imaging using atomic force microscopy (AFM)
combined with infrared (IR) spectroscopy (AFM-IR) is a rapidly emerging
modality to record correlated structural and chemical images. Although
the expectation is that the spectral data faithfully represents the
underlying chemical composition, the sample mechanical properties
affect the recorded data (known as the probe–sample-interaction
effect). Although experts in the field are aware of this effect, the
contribution is not fully understood. Further, when the sample properties
are not well-known or when AFM-IR experiments are conducted by nonexperts,
there is a chance that these nonmolecular properties may affect analytical
measurements in an uncertain manner. Techniques such as resonance-enhanced
imaging and normalization of the IR signal using ratios might improve
fidelity of recorded data, but they are not universally effective.
Here, we provide a fully analytical model that relates cantilever
response to the local sample expansion which opens several avenues.
We demonstrate a new method for removing probe–sample-interaction
effects in AFM-IR images by measuring the cantilever responsivity
using a mechanically induced, out-of-plane sample vibration. This
method is then applied to model polymers and mammary epithelial cells
to show improvements in sensitivity, accuracy, and repeatability for
measuring soft matter when compared to the current state of the art
(resonance-enhanced operation). Understanding of the sample-dependent
cantilever responsivity is an essential addition to AFM-IR imaging
if the identification of chemical features at nanoscale resolutions
is to be realized for arbitrary samples