17 | 03 | 2017

The paper, Hyperspectral infrared nanoimaging of organic samples based on Fourier transform infrared nanospectroscopy in which CIDETEC has participated, has been published in Nature Communications.


On February 15, Nature Communications published the article that contains the results of the research carried out by researchers from Nanogune, Ikerbasque, Cidetec and the Robert Koch Institut in Berlin.

A new dimension in chemical nanoimaging 
An ultimate goal in materials science, biomedicine or nanotechnology is the non-invasive compositional mapping of materials with nanometer-scale spatial resolution. Although high-resolution imaging techniques exist (for example, electron or scanning probe microscopies) they cannot meet the increasing demands in research, development and industry while simultaneously offering noninvasive techniques and offering the highest chemical sensitivity. 
Nanoscale chemical analysis has recently become possible with nano-FTIR spectroscopy, 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 or a synchrotron, and analyzing the backscattered light with a specially designed Fourier Transform spectrometer, infrared spectroscopy with a spatial resolution of less than 20 nm has been achieved. However, only point spectra or line scans comprising no more than a few tens of nano-FTIR spectra could be achieved on organic samples, owing to the long acquisition times. 
Now, researchers from nanoGUNE (San Sebastian, Spain), Ikerbasque (Bilbao, Spain), Cidetec (San Sebastian, Spain) and the Robert Koch-Institut (Berlin, Germany) developed hyperspectral infrared nanoimaging. The technique allows for recording two-dimensional arrays of several thousand of nano-FTIR spectra – usually referred as to hyperspectral data cubes – in few hours, and this with a spatial resolution and precision below 30 nm. 
“The excellent data quality allows for extracting nanoscale-resolved chemical and structural information applying multivariate data analysis procedures, which are statistical techniques that use the complete spectroscopic information available at each pixel”, says Iban Amenabar, first author of the work. For instance, identification and 2D mapping of target components can be done based on widely available FTIR databases. Even without any previous information about the sample and its components, pixels with similar infrared spectra can be grouped automatically with the help of hierarchical cluster analysis. Imaging a three-component polymer blend and applying multivariate analysis, the researchers obtained chemical maps that do not only reveal the spatial distribution of the individual components but also spectral anomalies that were explained by local chemical interaction. 
For their experiments, the researchers used the commercial nano-FTIR system from Neaspec GmbH including a mid-infrared laser continuum that covers the mid-infrared spectral range from 1000 to 1900 cm-1. Multivariate analysis of the hyperspectral data was done with the software tool CytoSpec, which was developed by coauthor Peter Lasch. 
“With the rapid development of high-performance mid-infrared lasers and by applying advanced noise reduction strategies, we obtain high-quality hyperspectral infrared nanoimaging in just a few minutes”, concludes Rainer Hillenbrand who led the work. “We see a large application potential in various fields of science and technology, including the chemical mapping of polymer composites, pharmaceutical products, organic and inorganic nanocomposite materials or biomedical imaging”, he adds. 

Original publication: 
I. Amenabar, S. Poly, M. Goikoetxea, W. Nuansing, P. Lasch, and R. Hillenbrand, Hyperspectral infrared nanoimaging of organic samples based on Fourier transform infrared nanospectroscopy, Nat. Commun. 8:14402 doi: 10.1038/ncomms14402 (2017

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