Person:
El-Sayed, Mostafa A.

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    Surface properties of semiconductor and metallic nanocrystals
    (Georgia Institute of Technology, 2010-01-23) El-Sayed, Mostafa A. ; Nigm, Soheir ; Talaat, Hassan
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    The stability of colloidal metallic nanoparticles in reactive chemical environments
    (Georgia Institute of Technology, 7/31/2009) El-Sayed, Mostafa A.
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    Cancer Nanotechnology
    (Georgia Institute of Technology, 2009-05-01) Nie, Shuming ; McDonald, John F. ; El-Sayed, Mostafa A.
    Shuming Nie is the Wallace H. Coulter Distinguished Chair Professor in Biomedical Engineering at Emory University and the Georgia Institute of Technology. His research interest is broadly in biomolecular engineering and nanotechnology. John McDonald is taking an integrated systems approach to the study of cancer. This means that he views cancer not as a defect in any particular gene or protein, but as a de-regulated cellular/ inter-cellular process. Mostafa El-Sayed is the Julius Brown Chair and Regents Professor in the School of Chemistry and Biochemistry at Georgia Tech. He researches Nanoscience and also investigates how Nanoparticles can be used in Nanomedicine, Nano Catalysis, and Nanophotonics.
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    The stability of colloidal metallic nanoparticles in reactive chemical environments
    (Georgia Institute of Technology, 2009-02-01) El-Sayed, Mostafa A. ; Wang, Zhong
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    Electron dynamics in gold and gold–silver alloy nanoparticles: The influence of a nonequilibrium electron distribution and the size dependence of the electron–phonon relaxation
    (Georgia Institute of Technology, 1999-07-15) Link, S. ; Burda,  C. ; Wang, Z. L. (Zhong Lin) ; El-Sayed, Mostafa A.
    Electron dynamics in gold nanoparticles with an average diameter between 9 and 48 nm have been studied by femtosecond transient absorption spectroscopy. Following the plasmon bleach recovery after low power excitation indicates that a non-Fermi electron distribution thermalizes by electron–electron relaxation on a time scale of 500 fs to a Fermi distribution. This effect is only observed at low excitation power and when the electron distribution is perturbed by mixing with the intraband transitions within the conduction band (i.e., when the excitation wavelength is 630 or 800 nm). However, exciting the interband transitions at 400 nm does not allow following the early electron thermalization process. Electron thermalization with the lattice of the nanoparticle by electron–phonon interactions occurs within 1.7 ps under these conditions, independent of the excitation wavelength. In agreement with the experiments, simulations of the optical response arising from thermalized and nonthermalized electron distributions show that a non-Fermi electron distribution leads to a less intense bleach of the plasmon absorption. Furthermore, the difference between the response from the two electron distributions is greater for small temperature changes of the electron gas (low excitation powers). No size dependence of the electron thermalization dynamics is observed for gold nanoparticles with diameters between 9 and 48 nm. High-resolution transmission electron microscopy (HRTEM) reveals that these gold nanoparticles possess defect structures. The effect of this on the electron–phonon relaxation processes is discussed. 18 nm gold–silver alloy nanoparticles with a gold mole fraction of 0.8 are compared to 15 nm gold nanoparticles. While mixing silver leads to a blue-shift of the plasmon absorption in the ground-state absorption spectrum, no difference is observed in the femtosecond dynamics of the system.