Poly- and single-crystalline Au micro- and nanostructures are synthesized at GSI by electrodeposition in etched ion-track membranes. Currently fabricated structures include cylindrical Au, AuAg, and porous Au nanowires with diameters down to 25 nm as well as nanowire dimers.

With infrared spectroscopic microscopy using synchrotron light, the resonant light scattering from single metal nanowires with diameters in the 100 nm range and with lengths of a few microns was investigated in collaboration with the group of Prof. A.M. Pucci at the University of Heidelberg. Significant antenna-like plasmon resonances were observed in good agreement with  light-scattering calculations. The resonances depend not only on wire length and diameter but also on the dielectric surrounding of the nanowire. 

In collaboration with the Max-Planck Institute for Intelligent Systems in Stuttgart, scanning transmission electron microscopy (STEM) imaging combined with electron energy-loss spectroscopy (EELS) is employed to investigate longitudinal surface plasmon resonance coupling in metallic nanowire dimers with gap sizes down to about 7 nm. Applying this method, we investigate bright and dark longitudinal as well as transversal modes with a very high spatial resolution of a few nanometers, and study the influence of gap size, aspect ratio, and multipole order on mode splitting. A high-energy resolution of 0.12 eV enabled the study of mode splitting into bonding and antibonding modes, amounting to 0.23 eV for a gap of about 8 nm. These investigations continue to characterize the plasmonic properties of further novel nanostructures synthesized by ion-track technology.

Recent publications

• Plasmonic modes in Au and AuAg nanowires and nanowire dimers studied by electron energy loss spectroscopy, I. Schubert and M.E. Toimil-Molares, Chapter 4 in the book “Plasmonics” edited by Tatjana Gric, ISBN 978-1-78984-434-4, InTech (2018).
• Porous gold nanowires: plasmonic response and SEIRA, I. Schubert, C. Huck, P. Kröber, F. Neubrech, A. Pucci, M.E. Toimil-Molares, C. Trautmann, J. Vogt, Advanced Optical Materials, 4 (2016) 1838-1845.
• Growth and morphological analysis of segmented AuAg alloy nanowires created by pulsed electrodeposition in ion-track etched membranes, I. Schubert, L. Burr, C. Trautmann, M.E. Toimil-Molares, Beilstein J. of Nanotechnology 6 (2015) 1272.
• STEM-EELS analysis of multipole surface plasmon modes in symmetry-broken AuAg nanowire dimers, I. Alber, W. Sigle, P. van Aken, C. Trautmann, M.E. Toimil-Molares, Nanoscale 7 (2015) 4935.
• Multipole surface plasmon resonances in conductively coupled metal nanowire dimers, I. Alber, W. Sigle, F. Demming-Janssen, R. Neumann, C. Trautmann, P.A. van Aken, M.E. Toimil-Molares, ACS Nano 6 (2012) 9711-9717.
• Visualization of Multipolar Longitudinal and Transversal Surface Plasmon Modes in Nanowire Dimers, I. Alber, W. Sigle, S. Müller, R. Neumann, O. Picht, M. Rauber, P.A. van Aken, M.E. Toimil-Molares, ACS Nano 5 (2011) 9845–9853.
• Resonant Plasmonic and Vibrational Coupling in a Tailored Nanoantenna for Infrared Detection, F. Neubrech, A. Pucci, T.W. Cornelius, S. Karim, A. Garcia-Etxarri, J. Aizpurua, Phy. Rev. Lett. 101 (2008) 157403.
• Resonances of individual metal nanowires in the infrared, F. Neubrech, T. Kolb, R. Lovrincic, G. Fahsold, A. Pucci, J. Aizpurua, T.W. Cornelius, M.E. Toimil-Molares, R. Neumann, S. Karim, Appl. Phys. Lett. 89 (2006) 253104.
• Synthesis of gold nanowires with controlled crystallographic characteristics, S. Karim,M.E. Toimil-Molares, F. Maurer, G. Miehe, W. Ensinger, J. Liu, T.W. Cornelius, R. Neumann, Appl. Phys. A 84 (2006) 403-407.
• Electrochemical fabrication of single-crystalline and polycrystalline Au nanowires: The influence of deposition parameters, J. Liu, J.L. Duan, M.E. Toimil-Molares, S. Karim, T.W. Cornelius, D. Dobrev, H.J. Yao, Y.M. Sun, M.D. Hou, D. Mo, Z.G. Wang, R. Neumann, Nanotechnology 17 (2006) 1922-1926.

 GSI contact: m.e.toimilmolares(at)gsi.de