Three-dimensional imaging of localized surface plasmon resonances of metal nanoparticles

• Published in: Nature (London) 2013-10, Vol.502 (7469), p.80-84
• Main Authors: Nicoletti, Olivia, de la Peña, Francisco, Leary, Rowan K., Holland, Daniel J., Ducati, Caterina, Midgley, Paul A.
• Format: Article
• Language: English
• Subjects: 639/301/357/354; 639/301/930/2735; 639/624/400/1021; 639/925/357/354; Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electron and ion emission by liquids and solids; impact phenomena; Electron energy loss spectra; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Humanities and Social Sciences; Hybridization; Impact phenomena (including electron spectra and sputtering); letter; Materials science; Methods; multidisciplinary; Nanoparticles; Nanopowders; Nanoscale materials and structures: fabrication and characterization; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Photovoltaics; Physics; Science; Silver; Spatial distribution; Structure; Surface and interface electron states; Surface plasmon resonance
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature12469

Localized surface plasmon resonances of an individual silver nanocube are reconstructed in three dimensions using electron energy-loss spectrum imaging, resulting in a better understanding of the optical response of noble-metal nanoparticles. Observing surface excitations for nano-optics Metal nanoparticles exhibit a range of striking and useful optical properties thanks to the excitation of localized surface plasmon resonances (LSPRs). But the precise relationship between the three-dimensional structure of the nanoparticles and the resulting LSPRs can be hard to determine. Paul Midgley and colleagues have developed a spectrally sensitive imaging technique, based on electron energy-loss spectroscopy, that permits three-dimensional visualization of many of the key features associated with these LSPRs. With this technique, the interplay between the LSPRs, nanoparticle structure and substrate–nanoparticle interactions can be directly probed. This study focuses on silver nanocubes, but the method demonstrated is applicable to similar plasmonic phenomena across all metal nanoparticles. The remarkable optical properties of metal nanoparticles are governed by the excitation of localized surface plasmon resonances (LSPRs). The sensitivity of each LSPR mode, whose spatial distribution and resonant energy depend on the nanoparticle structure, composition and environment, has given rise to many potential photonic, optoelectronic, catalytic, photovoltaic, and gas- and bio-sensing applications 1 , 2 , 3 . However, the precise interplay between the three-dimensional (3D) nanoparticle structure and the LSPRs is not always fully understood and a spectrally sensitive 3D imaging technique is needed to visualize the excitation on the nanometre scale. Here we show that 3D images related to LSPRs of an individual silver nanocube can be reconstructed through the application of electron energy-loss spectrum imaging 4 , mapping the excitation across a range of orientations, with a novel combination of non-negative matrix factorization 5 , 6 , compressed sensing 7 , 8 and electron tomography 9 . Our results extend the idea of substrate-mediated hybridization of dipolar and quadrupolar modes predicted by theory, simulations, and electron and optical spectroscopy 10 , 11 , 12 , and provide experimental evidence of higher-energy mode hybridization. This work represents an advance both in the understanding of the optical response of noble-metal nanoparticles and in the probing, analys