Article

Molecular Mapping by Low-Energy-Loss Energy-Filtered Transmission Electron Microscopy Imaging

Institute of Chemistry, Universidade Estadual de Campinas, Caixa Postal 6154, 13083-970, Campinas, SP, Brazil.
Analytical Chemistry (Impact Factor: 5.83). 03/2009; 81(6):2317-24. DOI: 10.1021/ac8024834
Source: PubMed

ABSTRACT Structure-function relationships in supramolecular systems depend on the spatial distribution of molecules, ions, and particles within complex arrays. Imaging the spatial distribution of molecular components within nanostructured solids is the objective of many recent techniques, and a powerful tool is electron spectroscopy imaging in the transmission electron microscope (ESI-TEM) in the low-energy-loss range, 0-80 eV. This technique was applied to particulate and thin film samples of dielectric polymers and inorganic compounds, providing excellent distinction between areas occupied by various macromolecules and particles. Domains differentiated by small changes in molecular composition and minor differences in elemental contents are clearly shown. Slight changes in the molecules produce intensity variations in molecular spectra that are in turn expressed in sets of low-energy-loss images, using the standard energy-filtered transmission electron microscopy (EFTEM) procedures. The molecular map resolution is in the nanometer range and very close to the bright-field resolution achieved for the same sample, in the same instrument. Moreover, contrast is excellent, even though sample exposure to the electron beam is minimal.

Download full-text

Full-text

Available from: Camila A Rezende, Jun 25, 2014
0 Followers
 · 
113 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Specimen contamination induced by electron beam irradiation has long been a serious problem for high-resolution imaging and analysis by a transmission electron microscope (TEM). It creates a deposition of carbonaceous compounds on a region under study, causing the loss of resolution. We developed a method to reduce the beam-induced specimen contamination by cleaning a TEM with activated oxygen radicals. The hydrocarbon contaminants accumulated inside the microscope's chamber can be etched away by gentle chemical oxidation without causing any damage to the microscope. The "contamination-free TEM" can effectively suppress the deposition of carbon-rich products on a specimen and therefore enables us to perform high-resolution carbon elemental mapping by energy-filtering transmission electron microscopy (EFTEM). In this study, we investigated the structure of polymer brushes immobilized on a silica nanoparticle (SiNP), of which molecular weight, length, and density of the brushes had been characterized in detail. The isolated particle showed the stretched formations of the polymer chains growing from the surface, while the densely distributed particles showed the connection of the polymer chains between neighboring particles. Moreover, the polymer brush layer and the surface initiator could be differentiated from each other by the component-specific contrast achieved by electron spectroscopic imaging (ESI). The contamination-free TEM can allow us to perform high-resolution carbon mapping and is expected to provide deep insights of soft materials' nanostructures.
    ACS Nano 05/2009; 3(5):1297-304. DOI:10.1021/nn9001598 · 12.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Energy-filtering electron transmission spectroscopy observation has been achieved to elucidate the nanostructures of powdery nanohybrids, which were produced by the dry mechanical milling of organic pigments and silica nanoparticles. The hybrids possess core-shell structures, irrespective of the levels of aggregation of primary particles, whereas hollow sites of aggregates of primary silica particles were filled with the pigment, leading to the locally concentrated distribution of the pigment to reduce the surface areas of the hybrids. The results imply that nanohybridization is referred to as the buildup method, although mechanical tools and procedures are quite the same as those for the conventional breakdown method.
    ACS Applied Materials & Interfaces 05/2009; 1(5):977-81. DOI:10.1021/am900066y · 6.72 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Charge distribution in insulators has received considerable attention but still poses great scientific challenges, largely due to a current lack of firm knowledge about the nature and speciation of charges. Recent studies using analytical microscopies have shown that insulators contain domains with excess fixed ions forming various kinds of potential distribution patterns, which are also imaged by potential mapping using scanning electric probe microscopy. Results from the authors' laboratory show that solid insulators are seldom electroneutral, as opposed to a widespread current assumption. Excess charges can derive from a host of charging mechanisms: excess local ion concentration, radiochemical and tribochemical reactions added to the partition of hydroxonium and hydronium ions derived from atmospheric water. The last factor has been largely overlooked in the literature, but recent experimental evidence suggests that it plays a decisive role in insulator charging. Progress along this line is expected to help solve problems related to unwanted electrostatic discharges, while creating new possibilities for energy storage and handling as well as new electrostatic devices.
    Journal of Physics Condensed Matter 07/2009; 21(26):263002. DOI:10.1088/0953-8984/21/26/263002 · 2.35 Impact Factor
Show more