Special CPM Seminar

Nanoscale Chemical Imaging by Photo-Induced Force Microscopy

Tom Albrecht

Molecular Vista, Inc.

Correlating spatial chemical information with the morphology of multi-component nanostructures remains a challenge for the scientific community as many such systems are not easily interrogated at the nanometer scale in real-space via conventional approaches based on optics or electrons. A novel scanning probe technique called Photo-induced Force Microscopy (PiFM) measures the photo-induced polarizability of the sample directly in the near-field by detecting the force acting between the tip and sample which arises from local polarization. Imaging with infrared wavelengths specific to different molecular components, PiFM can map the nanometer-scale distribution of individual chemical species in diverse multi-phase and multi-component materials. When coupled with a widely tunable quantum cascade laser system, a rich spectral analysis mode, which we refer to as hyperspectral imaging, can be realized. A hyperspectral image consists of a PiFM spectrum (which generally correlates well with bulk FTIR spectra for most species) at each pixel of a (n x n) image. By detecting the molecular infrared absorption via mechanical force measurement on a sharp tip, PiFM achieves spatial resolution that surpasses the diffraction limit by an astonishing factor of ~1000X. The power and utility of PiFM and hyperspectral imaging is demonstrated by experimental results on several multi-component nanosystems, including self-assembled block copolymer patterns, polymer blends, and a variety of other organic materials.