Global Raman imaging is an exceptional technique for the analysis of large surfaces of thin films and advanced materials. Its rapidity makes it a great tool not only for universities and research institutes, but also for industrial laboratories. With no or minimal sample preparation, RIMA™, Photon etc.’s new hyperspectral Raman imager, can easily take part in routine analysis, where the prompt access to information about sample composition is crucial for the development of new materials.
With systems based on point-to-point or scanning technologies, the acquisition of maps of large areas is often tedious and time consuming: the analysis of a sample may take hours. RIMA™ expedites in minutes the acquisition of the whole area in the field of view, rendering full maps of a sample with unmatched rapidity. In fact, the hyperspectral cube is built image by image, along the spectral window of interest, with a spectral resolution better than 7 cm-1. Since a spectrum is recorded for each pixel, it is possible, with a 1024 x 1024 pixels camera, to collect more than one million spectra without moving the sample. Moreover, the size of the maps can be as large as 650 x 650 mm2, depending on the magnification of the objective used for the analysis. Photon etc.’s filters used for hyperspectral imaging are based on holographic gratings, and provide very high efficiency for an optimal acquisition of the weak Raman scattering. Combined with top of the line low noise CCD or EMCCD cameras, RIMA™ is the most efficient Raman imaging system on the market.
In order to show the advantages of RIMA™ in the analysis of nanomaterials in biological systems, carbon nanotubes (CNT) have been incubated with a sample of Candida Albicans yeast cells and exposed to a homogeneous (flat-top) laser excitation of 532 nm on the entire field of view. With a 50X objective, an area of 260 x 130 μm2 was imaged, with a step of 4.5 cm-1 and an exposition time of 15 s. The complete analysis took 20 minutes, for a total of more than 60,000 spectra.
Figure 1 shows the Raman hyperspectral cube of a portion of the imaged area containing the yeast. The monochromatic Raman images revealed the position of the aggregated yeast cells stained with the CNTs. The typical signal of CNTs (red line) confirmed their presence on the yeast cells, while in other areas the hyperspectral camera did not detect any CNT Raman signal (blue line).
Results kindly provided by: Nicolas Cottenye, Étienne Gaufrès, Nathalie Tang and Richard Martel, at Université de Montréal, Canada.