Browsing by Author "Zhan, Xiaobo"

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    Bifunctional Luminomagnetic Rare-Earth Nanorods for High-Contrast Bioimaging Nanoprobes
    (Springer Nature, 2016) Gupta, Bipin Kumar; Singh, Satbir; Kumar, Pawan; Lee, Yean; Kedawat, Garima; Narayanan, Tharangattu N.; Vithayathil, Sajna Antony; Ge, Liehui; Zhan, Xiaobo; Gupta, Sarika; Martí, Angel A.; Vajtai, Robert; Ajayan, Pulickel M.; Kaipparettu, Benny Abraham
    Nanoparticles exhibiting both magnetic and luminescent properties are need of the hour for many biological applications. A single compound exhibiting this combination of properties is uncommon. Herein, we report a strategy to synthesize a bifunctional luminomagnetic Gd2−xEuxO3 (x = 0.05 to 0.5) nanorod, with a diameter of ~20 nm and length in ~0.6 μm, using hydrothermal method. Gd2O3:Eu3+ nanorods have been characterized by studying its structural, optical and magnetic properties. The advantage offered by photoluminescent imaging with Gd2O3:Eu3+ nanorods is that this ultrafine nanorod material exhibits hypersensitive intense red emission (610 nm) with good brightness (quantum yield more than 90%), which is an essential parameter for high-contrast bioimaging, especially for overcoming auto fluorescent background. The utility of luminomagnetic nanorods for biological applications in high-contrast cell imaging capability and cell toxicity to image two human breast cancer cell lines T47D and MDA-MB-231 are also evaluated. Additionally, to understand the significance of shape of the nanostructure, the photoluminescence and paramagnetic characteristic of Gd2O3:Eu3+ nanorods were compared with the spherical nanoparticles of Gd2O3:Eu3+.
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    Nanostructure Silicon Anodes Prepared by Chemical Reduction Method for Lithium Ion Batteries
    (2013-04-18) Zhan, Xiaobo; Ajayan, Pulickel M.; Barrera, Enrique V.; Vajtai, Robert
    Silicon is a promising anode material in high energy density application of lithium ion batteries because it is known to have the largest specific capacity (~4200mAh/g), ten time that of the commercially graphite carbon. However, they have shown great capacity fading and short battery life due to big volume changes upon insertion and extraction of lithium, which results in pulverization and loss of the electrical contact between the active material and the current collector. In this thesis, we successfully fabricated two kinds of nanostructured silicon anodes by chemical reduction method and test them versus Li as half-cell. Porous Si showed a reversible capacity of 1482mAh/g after 30 cycles, which is 50% of its initial capacity. Carbon coating greatly improves the cycling stability and increase the capacity retention to 85%. Compared Si nanosheets structure, graphene-silica sandwich structure showed great improvements in capacity and cycling stability. This chemical reduction method is facile, mass productive and thus is promising in the nanostructure silicon anode fabrication.