IR Nanochemical Mapping

Research nanoscale chemical distribution

Infrared nanochemical mapping is about answering questions of nanoscale chemical distribution. Which chemistry is under the AFM tip, and exactly how are chemistries mixed or phase separated? These are increasingly important and challenging questions in a world where nanoscale structuring in multicomponent systems is used to achieve material properties by design, and where molecularly thin, compatibilizing layers at interfaces play critical roles. The solution combines the power of infrared absorption spectroscopy for non-destructive, label-free chemical identification with the nanoscale resolution afforded by atomic force microscopy.

Scanning probe infrared imaging scheme
Scanning probe infrared imaging scheme. Nanoscale infrared absorption and reflection are mapped directly as optical signal, utilizing the tip as oscillating optical antenna to isolate the near field signal.

Using direct optical-light scattering off a metal coated AFM tip, scanning probe infrared imaging on Inspire provides nanoscale resolution, infrared absorption and reflection maps independent of thermal and mechanical sample properties, with 10nm lateral resolution and monolayer sensitivity.

Just choose an infrared wavelength to match a characteristic absorption band of the moiety of interest, and map out nanoscale chemistry at the surface of any sample compatible with atomic force microscopy.

Infrared absorption image of PS PMMA blend
Infrared absorption image of PS-PMMA blend at 1730cm-1. Image size 5 microns.
Infrared reflection image of Pentacene film
Infrared reflection image resolving individual molecular layers of Pentacene film. Image size 3.3 microns.

Highest resolution can open a window, beyond chemistry, to subtle changes near phase boundaries where a given chemistry is exposed to a gradient of chemical environments (see B. Pollard, E.A. Muller, K. Hinrichs, and M.B. Raschke, "Vibrational Nano-Spectroscopic Imaging Correlating Structure with Intermolecular Coupling and Dynamics," Nature Communications 5 (2014): 3587, doi:10.1038/ncomms4587).

 

The key to highest resolution, artifact-free imaging is to retain the integrity of the AFM tip. Traditional indirect approaches that rely on contact mode rarely provide a good means for obtaining high-resolution images on polymers due to the severe tip wear and sample damage inevitably caused by  the mode's intrinsic lateral forces.

 

Inspire solves this issue by offering a choice of either TappingMode or PeakForce Tapping feedback. Though TappingMode eliminates lateral forces, it can still suffer from destructive transient forces when encountering challenging geometries. The most consistently artifact-free, high-resolution imaging is achieved by Bruker's proprietary PeakForce Tapping feedback, which eliminates these forces completely.