Using low-loss energy-filtering transmission electron microscopy (EFTEM) imaging, we map surface plasmon resonances (SPRs) at optical wavelengths on single triangular silver nanoprisms. We show that EFTEM imaging combining high spatial sampling and high energy resolution enables the detection and for the first time, to the best of our knowledge, mapping at the nanoscale of an extra multipolar SPR on these nanoparticles. As illustrated on a 276.5 nm long nanoprism, this eigenmode is found to be enhanced on the three edges where it exhibits a two-lobe distribution.
"According to the above definition, metallic nano-particles would not be considered quantum dots because they lack single localised charge carriers. The free electrons typically found in metals are here responsible for low-energy surface plasmons, however, that are intricately linked to the particle sizes (Alvarez et al., 1997) and geometries, that is, faceting, (Nelayah et al., 2009) and often yield resonances in the optical frequency range so that such systems are also interesting for applications as optical waveguides, in nanophotonic devices and as sensors (Hutter & Fendler, 2004). The basis of such plasmonics remains, however, fundamentally different from quantum confinement in semiconductor quantum dots. "
[Show abstract][Hide abstract] ABSTRACT: This brief review describes the different types of semiconduc-tor quantum dot systems, their main applications and which types of microscopy methods are used to characterize them. Emphasis is put on the need for a comprehensive investigation of their size distribution, microstructure, chemical composi-tion, strain state and electronic properties, all of which influ-ence the optical properties and can be measured by different types of imaging, diffraction and spectroscopy methods in an electron microscope. Quantum dot systems
Journal of Microscopy 11/2014; 00(3):1-8. DOI:10.1111/jmi.12196 · 2.33 Impact Factor
"Recent developments include the use of dedicated in situ plasma cleaning in the TEM for EFTEM C K-edge studies of hybrid Au@polymer specimens (Horiuchi et al., 2009). Although low-loss EFTEM in the surface plasmon range (<5 eV) is now used intensively (e.g., Nelayah et al., 2009) the bulk plasmon range is much less explored because of the difficulty of data interpretation (Howie, 2003). However bulk plasmons can be been used to create high-contrast images with high signal-to-noise ratios to distinguish between different carbonaceous materials (Hunt et al., 1995; Du Chesne, 1999; Daniels et al., 2003; Linares et al., 2009). "
[Show abstract][Hide abstract] ABSTRACT: Hybrid (organic shell-inorganic core) nanoparticles have important applications in nanomedicine. Although the inorganic components of hybrid nanoparticles can be characterized readily using conventional transmission electron microscopy (TEM) techniques, the structural and chemical arrangement of the organic molecular components remains largely unknown. Here, we apply TEM to the physico-chemical characterization of Au nanoparticles that are coated with plasma-polymerized-allylamine, an organic compound with the formula C3H5NH2. We discuss the use of energy-filtered TEM in the low-energy-loss range as a contrast enhancement mechanism for imaging the organic shells of such particles. We also study electron-beam-induced crystallization and amorphization of the shells and the formation of graphitic-like layers that contain both C and N. The resistance of the samples to irradiation by high-energy electrons, which is relevant for optical tuning and for understanding the degree to which such hybrid nanostructures are stable in the presence of biomedical radiation, is also discussed.
"As a result, the electrons lose energy. More precisely, typical transmission electron microscopes deliver electrons with kinetic energies ranging from several 10 keV to several 100 keV, while the corresponding energy losses associated with plasmons range between 0.5 eV and 20 eV    . This suggests that in such processes the electron's momentum remains practically unchanged. "
[Show abstract][Hide abstract] ABSTRACT: In this work, we demonstrate how to extract electron energy loss spectra of metallic nano-particles from time-domain computations. Specifically, we employ the Discontinuous Galerkin Time-Domain (DGTD) method in order to model the excitation of individual metallic nano-spheres and dimers of spheres by a tightly focussed electron beam. The resulting electromagnetic fields that emanate from the particles act back on the electrons and the accumulated effect determines the electrons' total energy loss. We validate this approach by comparing with analytical results for single spheres. For dimers, we find that the electron beam allows for an efficient excitation of dark modes that are inaccessible for optical spectroscopy. In addition, our time-domain approach provides a basis for dealing with materials that exhibit a significant nonlinear response.
Photonics and Nanostructures - Fundamentals and Applications 05/2011; 9(4). DOI:10.1016/j.photonics.2011.04.003 · 1.47 Impact Factor
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