Electron Microscopy for Catalysis

The electron microscopy techniques are among the most powerful methodologies in order to characterize the structure, the morphology and the chemistry of a catalyst at the nanoscale. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are right now routinely tools, but they are also a precious help for advanced studies, disclosing the intimate relation between structure and activity.  In TEM a parallel beam of electrons is transmitted through a thin section/ small particles (<100nm) to form images and collect diffraction, chemical information (EELS) and elemental maps (EFTEM). Next to it, STEM technique allows the collection of Z-contrast or crystalline-contrast micrographs helping to elucidate structural and metal dispersion of catalytic systems. In SEM, a focused electron beam scans the sample surface, interact with it and produce secondary electrons and backscattered electrons used to reconstruct the topography and the composition (combining SEM with EDX analysis). Some examples of application relative to the main TEM and SEM techniques in the catalytic field are listed below.



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The 200kV ZEISS LIBRA200FE is a high-resolution electron microscope that can be operated both in standard transmission (TEM) and scanning (STEM) modes. It enables the observation of morphological and structural details with sub-nanometer resolution. Crystalline structure can be investigated in detail thanks to electron diffraction and HRTEM capabilities. The in-column Omega spectrometer and the Oxford EDS/EDX system provide complementary techniques to investigate chemical composition at the nanoscale in the form of elemental maps. Tomographic reconstruction of the three-dimensional shape of the specimen is also possible with improved accuracy thanks to the reduced missing wedge. The high flexibility in experimental scheme and data acquisition make the LIBRA200FE a unique investigation tool for high-resolution characterization in nanotechnology, materials and life science.
ISTeM provides state-of-the-art technology, expert image collection and analysis, and welcomes customers on its premises even during image collection.
Philips XL30 ESEM

Philips XL30 ESEM

The XL-30 ESEM take advantage of a High-Brightness Field Emission Gun (FEG) operating from 200V - 30kV with 20Å resolution digital imaging in order to disclose the surface morphology of conductive or insulating samples. The unique futures of its chamber allow different operating mode: classical high-vacuum mode, low-vacuum mode, and environmental mode. Basically, all the samples from hydrated to non-conductive ones could be examined, avoiding so specimen coating. These modes are not affecting the instrument resolution: even in the saturated water vapor environment, the XL-30 is able to go down to 2.0 nm at 30 kV. The instrument is equipped with a secondary electron detector for high vacuum (SE) and low vacuum (GSE) and a backscattered detector (BSE). The microscope is equipped with an EDX detector (EDAX energy dispersive x-ray detector) in order to collect X-Ray data and unveil the analytical composition at the micro/nanoscale. Thanks to the EDAX software, point analysis, linescan and elemental maps are available. The cryo stage and the heating stage (able to cool down the sample at -30°C or heat up till 1500°C) implement and extend the instrument capability for analysis in critical condition.

ISTEM have access to XL-30 ESEM through the active collaboration with the DISAT department of the Unversity of Insubria (Como - IT).

Electron Microscopy Applications

High Resolution TEM Images

TEM analysis allows picturing the catalyst morphology at the nanoscale, defining shape, size and size distribution of nanostructured materials. Pushing forward the resolution, a new set of information could be extracted in order to fully describe the catalyst down to the nanoscale. The local nanocrystalline structure could be disclosed learning about particle interactions, fine structure, crystalline orientation and morphology of nano-hetero structure and junction.  HRTEM images along with related FFT analysis could be used also to reveal material composition through the single crystalline pattern identification.

On the left side: 'LACTIC ACID FROM GLYCEROL BY ETHYLENE-STABILIZED PLATINUM-NANOPARTICLES' W. Oberhauser, C. Evangelisti, C. Tiozzo, F. Vizza and R. Psaro - ACS Catal.,6, 2016,1671

‘ELECTROCHEMICAL MILLING AND FACETING: SIZE REDUCTION AND CATALYTIC ACTIVATION OF PALLADIUM NANOPARTICLES’ Y. Chen, A. Lavacchi, S. Chen, F. di Benedetto,M. Bevilacqua, C. Bianchini, P. Fornasiero, M. Innocenti, M. Marelli, W. Oberhauser, S. Sun, and F. Vizza - Angew. Chem. Int. Ed.; Vol.51, 2012, 8500

‘THE CRITICAL ROLE OF INTRAGAP STATES IN THE ENERGY TRANSFER FROM GOLD NANOPARTICLES TO TIO2 ‘ A. Naldoni, F. Fabbri, M. Altomare, M. Marelli, R. Psaro, E. Selli, G. Salviati and V. Dal Santo - Phys. Chem. Chem. Phys., Vol. 17, 2015, 4864.


Elemental Maps at Nanoscale

Original Image Original
Modified Image Ce_Map

One of the most powerful tools included in the TEM/STEM methodologies is the local elemental analysis and maps at the nanoscale. The ISTEM microscopy allows two analysis mode: TEM-EELS analysis and maps (ESI electron spectroscopy image) and STEM-EDS (Energy Dispersive Spectroscopy). The first one could map a large number of elements giving information on the oxidation state, structure and the elemental map information is related to TEM morphology. The second use the X-ray generated by the interaction between the material and the electron beam. The EDS analysis allows collecting fast survey of elemental composition, semi-quant analysis and to map single elements in STEM mode.

on the left side: ‘HIGHLY ACTIVE NANOSTRUCTURED PALLADIUM-CERIA ELECTROCATALYSTS FOR THE HYDROGEN OXIDATION REACTION IN ALKALINE MEDIUM’ H. A. Miller, F. Vizza, M. Marelli, A. Zadick, L. Dubau, M. Chatenet, S. Geiger, S. Cherevko, H. Doan, R. K. Pavlicek, S. Mukerjee, D. R. Dekel - Nano Energy, 33, 2017, 293

‘α-Fe2O3/NiOOH: AN EFFECTIVE HETERO STRUCTURE FOR PHOTOELECTROCHEMICAL WATER OXIDATION’ F. Malara, A. Minguzzi, M. Marelli, S. Morandi, R. Psaro, V. Dal Santo, A. Naldoni ACS Catalysis , 5, 2015, 5292.

‘DEHYDROGENATIVE COUPLING PROMOTED BY COPPER CATALYSTS: A WAY TO OPTIMISE AND UPGRADE BIO-ALCOHOLS’ Scotti, N.; Zaccheria, F.; Evangelisti, C.; Psaro, R.; Ravasio, N.. Catal. Sci. Technol. 2017, 7 (6), 1386

‘BROADBAND HOT ELECTRON COLLECTION FOR SOLAR WATER SPLITTING WITH PLASMONIC TITANIUM NITRIDE’ A. Naldoni, U. Guler, Z. Wang, M. Marelli, F. Malara, X. Meng, L. V. Besteiro, A. O. Govorov, A. V. Kildishev, A. Boltasseva, V. M. Shalaev - Advanced Optical Materials, 2017, 1601031

High Z-Contrast STEM images


In STEM mode, the electron beam is focused in a spot (with size less than 1 nm) and used to scan the sample point o point. Tha transmitted information is then collected by a high angle annular dark-field (HAADF) detector in order to reconstruct the image where the contrast is ruled over by the atomic number (Z-Contrast) highlighting the presence of tiny metal NPs or enhancing the contrast of different materials in a heterostructure. Changing the associated camera length is possible to move in a crystalline-ruled over contrast mode, enhancing the crystalline phases vs. amorphous one. STEM mode could be coupled with EDS mapping and analysis in order to elucidate elemental analysis at the nanoscale. STEM could be coupled also with a special tomo-holder in order to collect 2D projection images series at incremental tilts and reconstruct the 3D tomographic volume, collecting information about the internal and external material structure.

‘TIO2 NANOTUBES ARRAYS LOADED WITH LIGAND-FREE AU NANOPARTICLES: ENHANCEMENT IN PHOTOCATALYTIC ACTIVITY’ M. Marelli, C. Evangelisti, M. V. Diamanti, M. P. Pedeferri, C. L. Bianchi, L. Schiavi, V. Dal Santo, A. Strini - ACS Applied Materials & Interfaces, 8, 2016, 31051.

‘CONTROL OF COPPER PARTICLES DEPOSITION IN MESOPOROUS SBA-15 SILICA BY MODIFIED CVD METHOD’ - T. Tsoncheva, A. Gallo, I. Genova, I. Spassova, M. Marelli, M. Dimitrov, M. Khristova, G. Atanasova, D. Kovacheva, D. Nihtyanova, V. Dal Santo - Inorganica Chimica Acta, Vol. 423, 2014, 145

‘NANOSTRUCTURED Fe–Ag ELECTROCATALYSTS FOR THE OXYGEN REDUCTION REACTION IN ALKALINE MEDIA’ - H. A. Miller, M. Bevilacqua, J. Filippi, A. Lavacchi, A. Marchionni, M. Marelli, S. Moneti, W. Oberhauser, E. Vesselli, M. Innocenti and F. Vizza - J. Mater. Chem. A, Vol. 1, 2013, 13337.

Electron Diffraction


Electron diffraction in TEM, or better Selected Area Electron Diffraction (SAED), is a crystallographic methodology inside TEM that takes advantage of the interaction electron/matter and the resulting transmitted diffracted electron beam. An electron diffraction pattern is composed by spot or crystal reflex that satisfy the diffraction condition of the crystal structure. Single crystal will provide neat spot pattern, whereas polycrystalline system will provide bright ring patterns. SAED could be used (as X-ray diffraction) to identify crystal structure, different phases, crystal defects and measure lattice parameters Thanks to the SAED aperture, is possible to limit the investigated area to small portion or even single nanocrystals, giving a unique space resolved diffraction.

'A CONVENIENT PREPARATION OF La2CuO4 FROM MOLECULAR PRECURSORS’ D. Belli Dell'Amico, A. Di Giacomo, L. Falchia, L. Labella, M. Marelli, C. Evangelisti, M. Lezzerini, F. Marchetti, S. Samaritani - Polyhedron, 123, 2017, 33.

‘SYNTHESIS OF NANOCRYSTALLINE TiOF2 EMBEDDED IN A CARBONACEOUS MATRIX FROM TiF4 AND D-FRUCTOSE’ C. Evangelisti,; M. Hayatifar, F. Marchetti, M. Marelli, G. Pampaloni, F. Piccinelli - Inorganic Chemistry, 55, 2016, 1816

‘PHOTOELECTROCHEMICAL BEHAVIOR OF ELECTROPHORETICALLY DEPOSITED HEMATITE THIN FILMS MODIFIED WITH Ti(IV)’ N. Dalle Carbonare, R. Boaretto, S. Caramori, R. Argazzi, M. Dal Colle, L. Pasquini, R. Bertoncello, M. Marelli, C. Evangelisti, C. A. Bignozzi - Molecules, 21, 2016, 942.

High and Low Vacuum SEM

Original Image SE
Modified Image BSE

SEM could be used to picture the sample down to micro- and nano-scale. Using secondary electron (SE) the fine surface morphology could be revealed and could be extremely useful to analyze hierarchical or anchored nanostructures such as electrodes or particle loaded monolith. Moreover, ESEM or low vacuum mode available with the XL-30 SEM allows the direct analysis of non-conductive and semiconductor material without any coating treatment (i.e. gold or graphite coating). These coating treatments could hide the fine sample's nanofeatures or modify the sample morphology. The use of back-scattered electrons (BSE) decrease the resolution but allows the detection of different elements due to their dependence on the element atomic number (Z). The BSE images could be successfully used to highlight the presence of nanostructured metal nanoparticle, hardly detectable with the sole SE signal. SEM could be coupled with EDS methodology in order to analyze the local elemental composition and produce elemental maps at the micro- and nano-scale.

‘HIERARCHICAL HEMATITE NANOPLATELETS FOR PHOTOELECTROCHEMICAL WATER SPLITTING’ – M. Marelli, A. Naldoni, A. Minguzzi, M. Allieta, T. Virgili, G. Scavia, S. Recchia, R. Psaro, and V. Dal Santo - ACS Applied Materials & Interfaces, Vol. 6, 2014, 11997.


‘TIO2 NANOTUBES ARRAYS LOADED WITH LIGAND-FREE AU NANOPARTICLES: ENHANCEMENT IN PHOTOCATALYTIC ACTIVITY’ M. Marelli, C. Evangelisti, M. V. Diamanti, M. P. Pedeferri, C. L. Bianchi, L. Schiavi, V. Dal Santo, A. Strini - ACS Applied Materials & Interfaces, 8, 2016, 31051.



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