SAN SEBASTIAN, Spain - Nanoscience researchers have developed a new instrument that helps chemically identify materials at the nanometer scale.

Researchers from the nanoscience research center NanoGUNE (San Sebastian, Spain), the university of Munich and Neaspec GmbH (Martinsried, Germany) presented a new instrumental development that solves a prime question of materials science and nanotechnology: how to chemically identify materials at the nanometer scale (F. Huth et al., Nano Letters, 2012, DOI: 10.1021/nl301159v).

An ultimate goal in modern chemistry and materials science is the non-invasive chemical mapping of materials with nanometer-scale resolution. A variety of high-resolution imaging techniques exist (e.g. electron microscopy or scanning probe microscopy), however, their chemical sensitivity cannot meet the demands of modern chemical nano-analytics. Optical spectroscopy, on the other hand, offers high chemical sensitivity but its resolution is limited by diffraction to about half the wavelength, thus preventing nanoscale-resolved chemical mapping.

Nanoscale chemical identification and mapping of materials now becomes possible with nano-FTIR, an optical technique that combines scattering-type scanning near-field optical microscopy (s-SNOM) and Fourier transform infrared (FTIR) spectroscopy. By illuminating the metalized tip of an atomic force microscope (AFM) with a broadband infrared laser, and analyzing the backscattered light with a specially designed Fourier Transform spectrometer, the researchers could demonstrate local infrared spectroscopy with a spatial resolution of less than 20 nm. “Nano-FTIR thus allows for fast and reliable chemical identification of virtually any infrared-active material on the nanometer scale,” said Florian Huth, who performed the experiments.

An important aspect of the advancement, with enormous practical relevance, is that the nano-FTIR spectra match extremely well with conventional FTIR spectra, while the spatial resolution is increased by more than a factor of 300 compared to conventional infrared spectroscopy. “The high sensitivity to chemical composition combined with ultra-high resolution makes nano-FTIR a unique tool for research, development and quality control in polymer chemistry, biomedicine and pharmaceutical industry” concluded Rainer Hillenbrand, leader of the Nanooptics group at nanoGUNE.