Spanish and German researchers have made a new instrumental development that solves a key materials science and nanotechnology question: how to chemically identify materials at the nanometre scale.

One of modern chemistry and materials science's main goals is to achieve the non-invasive chemical mapping of materials with nanometre-scale resolution.

Although a variety of high-resolution imaging techniques currently exist, such as electron microscopy or scanning probe microscopy, their chemical sensitivity cannot meet the demands of modern chemical nano-analytics. And despite the high chemical sensitivity offered by optical spectroscopy, its resolution is limited by diffraction to about half the wavelength, thus preventing nano-scale-resolved chemical mapping.

But now the European team has come up with a new method called Nano-FTIR, as they explain in the journal Nano Letters.

Nano-FTIR is an optical technique that combines scattering-type scanning near-field optical microscopy (s-SNOM) and Fourier Transform infrared (FTIR) spectroscopy.

The team illuminated the metallised tip of an atomic force microscope (AFM) with a broadband infrared laser, and analysed the backscattered light with a specially designed Fourier Transform spectrometer. This meant they could demonstrate local infrared spectroscopy with a spatial resolution of less than 20 nanometres.

Lead study author Florian Huth from Spanish research centre nanoGUNE, based in San Sebastin, comments: 'Nano-FTIR thus allows for fast and reliable chemical identification of virtually any infrared-active material on the nanometer scale.'

To boot, nano-FTIR spectra match extremely well with conventional FTIR spectra. The spatial resolution is increased by more than a factor of 300 compared to conventional infrared spectroscopy.

Rainer Hillenbrand, also from nanoGUNE, says: '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.'

For example, nano-FTIR can be applied for the chemical identification of nano-scale sample contaminations.

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European researchers identify materials at the nanoscale