Electron energy-loss spectroscopy (EELS) is widely used to identify elemental compositions of materials studied by microscopy. We demonstrate that the sensitivity and spatial resolution of EELS can be extended to the single-atom limit. A chemical map for gadolinium (Gd) clearly reveals the distribution of Gd atoms inside a single chain of metallofullerene molecules (Gd@C82) generated within a single-wall carbon nanotube. This characterization technique thus provides the "eyes" to see and identify individual atoms in nanostructures. It is likely to find broad application in nanoscale science and technology research.

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Abstract. Among electron beam microanalytical techniques, electron energy loss spectrometry (EELS) offers unique advantages in terms of information content, sensitivity, limits of detection. This paper describes new methods and tools for acquiring families of spectra over many pixels on the specimen, i.e. spectrumimages, and for processing them. Applications in different fields of research, both in materials science and in life sciences, demonstrate the potential impact of the technique for characterizing nano-sized structures.Key words: electron microscopy, nanoanalysis, electron energy loss spectrum, image-spectrum aquisition and processing.Electron energy loss spectrometry (EELS) measures the energy loss suffered by high energy incident electrons transmitted through the specimen prepared as a thin foil. Its information content is very diversified. The low loss range, between 5 and 50 eV, reflects mostly the collective behaviour of the conduction electron gas through the appearance of plasmon peaks, the energy of which is determined by the average electron density. After some lengthy data analysis one can also have access to optical properties and to localized surface electronic properties. The high energy range, from 50 eV up to 1000 or 2000 eV, exhibits the core-edges associated with the excitation of inner-shell atomic levels. Its main interest is for elemental identification. Moreover the study of the fine structures on these edges offers fingerprints for the determination of site symmetry and for the evaluation of bond lengths.When recorded in the electron microscope, EELS data also contain spatial information [1], which is usually intended for chemical analysis. In essence, one makes a map of the spatial origin of chemically significant signals such as the characteristic core-edges and this technique complements the standard X-ray compositional imaging mode. However it constitutes only one aspect of the richness of the field of applications for EELS mapping. The present paper discusses recent progress in spatially resolved EELS and its use as a nanoanalytical tool, in which spectra can be acquired from many adjacent nanosized areas in a heterogeneous material and processed quantitatively.

X-ray fluorescence microscopy (microXRF) is applied for the first time to study macrophages exposed to unpurified and purified single-walled (SW) and multiwalled (MW) carbon nanotubes (CNT). Investigating chemical elemental distributions allows one to (i) image nanotube localization within a cell and (ii) detect chemical modification of the cell after CNT internalization. An excess of calcium is detected for cells exposed to unpurified SWCNT and MWCNT and related toxicological assays are discussed.

Nucleation and growth have been studied on a cluster scale for preformed antimony clusters soft landed on an amorphous carbon substrate. It is shown how incident cluster size is a good parameter in monitoring independently the average island size and island density at room temperature. By exploiting the decrease of cluster mobility as the cluster size increases, we observe that, superimposed to a narrowing of the supported island distribution, the average island size distribution shifts down, presents a minimum, and increases.

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Abstract. 2014 Parallel-detection electron energy loss spectrometers are able to detect the EELS signal originating from only a few atoms on thin substrates. The instrumental requirements for attaining this level of performance, and the methodology for quantifying the results are described. For the case of small thorium clusters on a thin carbon film, the detection limit with currently available instrumentation is shown to be one atom.