Researchers in the Department of Electrical and Computer Engineering at The University of Texas at Austin (UT ECE) have demonstrated the ability to perform nanoscale chemical analysis of molecular films with unprecedented sensitivity by detecting molecular photoexpansion. PhD students Feng Lu and Mingzhou Jin led by Prof. Mikhail Belkin successfully acquired high-quality infrared spectra from as few as 300 molecules in a monolayer film in ambient conditions. These capabilities enable a highly-sensitive nanoscale analytical tool for chemists, biologists and materials scientists. The results were published in Nature Photonics in January this year.
Infrared spectroscopy is one of the most popular techniques in chemical analysis. The pattern of molecular infrared absorption peaks acts as a chemical fingerprint, enabling identification. Due to light diffraction, however, traditional infrared microscopy can only achieve spatial resolution of several microns.
In 2005, French researcher Alexander Dazzi and colleagues showed that infrared absorption in materials can be recorded by observing a sample's photoexpansion using an atomic force microscope (AFM) probe, a technique called AFM-IR.
By employing a combination of electromagnetic and resonance enhancement mechanisms, researchers at The University of Texas at Austin achieved approximately two orders of magnitude improvement in sensitivity, enabling for the first time broadband high-quality nanoscale infrared spectroscopy of films as thin as a single molecule.
The Belkin group is now transferring this technology to a California-based company Anasys Instruments that develops a variety of tools for nanoscale materials characterization. "We are extremely excited about this research," says Craig Prater, Chief Technology Officer at Anasys. "Extending the sensitivity of the AFM-IR technique to the scale of individual monolayers opens up a huge range of potential applications that were previously out of reach."
The research is supported by the Robert A. Welch Foundation. The technology transfer is sponsored by the U.S. Department of Energy under the Small Business Technology Transfer program.