TY - JOUR T1 - Multimodal plasmon coupling in low symmetry gold nanoparticle pairs detected in surface-enhanced Raman scattering JF - Applied Physics Letters Y1 - 2011 A1 - Dreaden, Erik A1 - Near, R. D. A1 - Abdallah, T. A1 - Talaat, M. H. A1 - El-Sayed, Mostafa A AB - We report on surface-enhanced Raman scattering of silicon phonon vibrations from arrays of gold nanoprism pairs fabricated by electron beam lithography. We found that resonant excitation of the quadrupolar surface plasmon mode of the nanoprisms increases Raman scattering intensity from the substrate as the distance between the nanoparticle pairs decreases. Finite element modeling and plasmon coupling theory indicate that symmetry is reduced as the nanoparticles approach, resulting in increased dipole-quadrupole coupling. Plasmonic enhancement of the incident and Raman-scattered photons results from the dipolar component of the mixed plasmonic field. This effect is expected to be largest in assemblies/aggregates of nanoparticles. (C) 2011 American Institute of Physics. [doi:10.1063/1.3555429] VL - 98 SN - 0003-6951 N1 - Dreaden, Erik C. Near, Rachel D. Abdallah, Tamer Talaat, M. Hassan El-Sayed, Mostafa A. M3 - 10.1063/1.3555429 ER - TY - JOUR T1 - The sensitivity of the energy band gap to changes in the dimensions of the CdSe quantum rods at room temperature: STM and theoretical studies JF - Chemical Physics Letters Y1 - 2009 A1 - Talaat, M. H. A1 - Abdallah, T. A1 - Mohamed, MB A1 - Negm, S. A1 - El-Sayed, Mostafa A AB - The energy band gap of a series of different sizes of CdSe quantum rods have been determined by STM technique at room temperature. The results confirm that the band gap of CdSe quantum rods (QRs) depends mainly on the width (the dimension of the electron confinement) and only slightly on the length as shown previously in the literatures. The experimental data is compared to that calculated using two theoretical models, the effective mass approximation (EMA) and the semi-empirical pseudopotential method (SEPM). The theoretical values for the energy band gap at varying radius are in agreement with the experimental results within 0.08 eV. (c) 2008 Published by Elsevier B.V. VL - 473 SN - 0009-2614 N1 - Talaat, H. Abdallah, T. Mohamed, M. B. Negm, S. El-Sayed, Mostafa A. M3 - 10.1016/j.cplett.2008.11.025 ER -