There are a variety of tools for characterizing nanoscale morphology and structure, such as scanning probe, scanning electron, and transmission electron microscopies. In contrast, the typical tools for analyzing chemical composition yield information at a larger length scale, often missing critically important nanoscale information. For example, the most widely used infrared technique, Fourier transform infrared spectroscopy, generates chemical data with micrometer spatial resolution. To address this gap, we installed a multifunctional instrument capable of simultaneously providing correlated topological, chemical (via infrared spectroscopy), thermal, and mechanical property maps with a spatial resolution below the diffraction limit of infrared radiation. We are currently working to further improve the instrument performance in terms of spectral range, spectral resolution and sensitivity.
The size dependent properties of nanomaterials give them functionality not found in their macroscopic counterparts. Determining the relationship between the structural, physical and chemical properties of nanomaterials is important for technological applications including electronics, photovoltaics, catalysis, biology and therapeutics. While infrared (IR) spectroscopy provides rich chemical and structural information, the wavelengths used to excite molecular vibrations, typically in the 3 μm - 15 μm range, are far larger than the characteristic dimensions of nanomaterials or cellular sub-components. Due to these longer wavelengths, IR imaging beyond the diffraction limit at the length scales typical of nanomaterials is more challenging than with visible light.
Fig. 1. Polymer sample made from polymethylmethacrylate (PMMA, large particles) and polystyrene (PS, small particles) embedded in an epoxy matrix as seen in an AFM height image (left). A simultaneous IR image (right) recorded at 1720 cm-1 adds chemical contrast, allowing for material identification. The carboxylic groups in PMMA absorb light at 1720 cm-1 while the PS and the epoxy matrix do not.
Lead Organizational Unit:cnst
Kevin Kjoller (Anasys Instruments)
Vibrational Spectroscopy Laboratory
Andrea Centrone, Phone 301-975-8225