Browsing by Author "Hassounah, Ibrahim"

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    Piezoresponse, Mechanical, and Electrical Characteristics of Synthetic Spider Silk Nanofibers
    Shehata, Nader; Kandas, Ishac; Hassounah, Ibrahim; Sobolčiak, Patrik; Krupa, Igor; Mrlik, Miroslav; Popelka, Anton; Steadman, Jesse; Lewis, Randolph (MDPI, 2018-08-01)
    This work presents electrospun nanofibers from synthetic spider silk protein, and their application as both a mechanical vibration and humidity sensor. Spider silk solution was synthesized from minor ampullate silk protein (MaSp) and then electrospun into nanofibers with a mean diameter of less than 100 nm. Then, mechanical vibrations were detected through piezoelectric characteristics analysis using a piezo force microscope and a dynamic mechanical analyzer with a voltage probe. The piezoelectric coefficient (d33) was determined to be 3.62 pC/N. During humidity sensing, both mechanical and electric resistance properties of spider silk nanofibers were evaluated at varying high-level humidity, beyond a relative humidity of 70%. The mechanical characterizations of the nanofibers show promising results, with Young’s modulus and maximum strain of up to 4.32 MPa and 40.90%, respectively. One more interesting feature is the electric resistivity of the spider silk nanofibers, which were observed to be decaying with humidity over time, showing a cyclic effect in both the absence and presence of humidity due to the cyclic shrinkage/expansion of the protein chains. The synthesized nanocomposite can be useful for further biomedical applications, such as nerve cell regrowth and drug delivery.
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    Reduced erbium-doped ceria nanoparticles: one nano-host applicable for simultaneous optical down- and up-conversions
    Shehata, Nader; Meehan, Kathleen; Hassounah, Ibrahim; Hudait, Mantu K.; Jain, Nikhil; Clavel, Michael B.; Elhelw, Sarah; Madi, Nabil (Springer, 2014-05-13)
    This paper introduces a new synthesis procedure to form erbium-doped ceria nanoparticles (EDC NPs) that can act as an optical medium for both up-conversion and down-conversion in the same time. This synthesis process results qualitatively in a high concentration of Ce3+ ions required to obtain high fluorescence efficiency in the down-conversion process. Simultaneously, the synthesized nanoparticles contain the molecular energy levels of erbium that are required for up-conversion. Therefore, the synthesized EDC NPs can emit visible light when excited with either UV or IR photons. This opens new opportunities for applications where emission of light via both up- and down-conversions from a single nanomaterial is desired such as solar cells and bio-imaging.