Browsing by Author "Sun, Zhengzong"

Now showing 1 - 5 of 5
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    Graphene chemistry: Synthesis and modulation
    (2012) Sun, Zhengzong; Tour, James M.
    This thesis investigates the chemistry of graphene from its basic synthesis to further modulation of its structure, geometry and surface chemical functional groups. A series of wet chemistry and dry chemistry experiments were performed. The wet chemistry includes the diazonium salt functionalization, graphene oxidation and reduction, nanotube unzipping chemistry, graphite intercalation and exfoliation. The dry chemistry includes chemical vapor deposition and solid carbon source synthesis of graphene, the control of domain size and stacking order, graphene hydrogenation and lithographically patterned graphene superlattices. With all these chemical approaches, graphene's electrical and optical properties, solubility in organic solvents, crystallography, and chemical reactivity were carefully investigated and discussed. In addition to the fundamental chemistry of graphene, the bio- and environmental impact of this new material was also taken into consideration and investigated.
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    Growth of graphene films from non-gaseous carbon sources
    (2015-08-04) Tour, James; Sun, Zhengzong; Yan, Zheng; Ruan, Gedeng; Peng, Zhiwei; Rice University; United States Patent and Trademark Office
    In various embodiments, the present disclosure provides methods of forming graphene films by: (1) depositing a non-gaseous carbon source onto a catalyst surface; (2) exposing the non-gaseous carbon source to at least one gas with a flow rate; and (3) initiating the conversion of the non-gaseous carbon source to the graphene film, where the thickness of the graphene film is controllable by the gas flow rate. Additional embodiments of the present disclosure pertain to graphene films made in accordance with the methods of the present disclosure.
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    Methods of controllably forming bernal-stacked graphene layers
    (2018-08-21) Tour, James M.; Sun, Zhengzong; Raji, Abdul-rahman O.; Rice University; United States Patent and Trademark Office
    Methods of controllably forming Bernal-stacked graphene layers are disclosed. The methods comprise: (1) cleaning a surface of a catalyst; (2) annealing the surface of the catalyst; (3) applying a carbon source onto the cleaned and annealed surface of the catalyst in a reaction chamber; and (4) growing the Bernal-stacked graphene layers on the surface of the catalyst in the reaction chamber, where the number of formed Bernal-stacked graphene layers is controllable as a function of one or more growth parameters, such as a total pressure of the reaction chamber. Further embodiments of the present disclosure also include steps of: (5) terminating the growing step; and (6) transferring the formed Bernal-stacked graphene layers from the surface of the catalyst onto a substrate.
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    Nanoparticulate carbon black in cigarette smoke induces DNA cleavage and Th17-mediated emphysema
    (eLife Sciences Publications Ltd., 2015) You, Ran; Lu, Wen; Shan, Ming; Berlin, Jacob M.; Samuel, Errol L.G.; Marcano, Daniela C.; Sun, Zhengzong; Sikkema, William K.A.; Yuan, Xiaoyi; Song, Lizhen; Hendrix, Amanda Y.; Tour, James M.; Corry, David B.; Kheradmand, Farrah
    Chronic inhalation of cigarette smoke is the major cause of sterile inflammation and pulmonary emphysema. The effect of carbon black (CB), a universal constituent of smoke derived from the incomplete combustion of organic material, in smokers and non-smokers is less known. In this study, we show that insoluble nanoparticulate carbon black (nCB) accumulates in human myeloid dendritic cells (mDCs) from emphysematous lung and in CD11c+ lung antigen presenting cells (APC) of mice exposed to smoke. Likewise, nCB intranasal administration induced emphysema in mouse lungs. Delivered by smoking or intranasally, nCB persisted indefinitely in mouse lung, activated lung APCs, and promoted T helper 17 cell differentiation through double-stranded DNA break (DSB) and ASC-mediated inflammasome assembly in phagocytes. Increasing the polarity or size of CB mitigated many adverse effects. Thus, nCB causes sterile inflammation, DSB, and emphysema and explains adverse health outcomes seen in smokers while implicating the dangers of nCB exposure in non-smokers.
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    Terahertz and Infrared Spectroscopy of Gated Large-Area Graphene
    (American Chemical Society, 2012) Ren, Lei; Zhang, Qi; Yao, Jun; Sun, Zhengzong; Kaneko, Ryosuke; Yan, Zheng; Nanot, Sébastien L.; Jin, Zhong; Kawayama, Iwao; Tonouchi, Masayoshi; Tour, James M.; Kono, Junichiro; Applied Physics Program
    We have fabricated a centimeter-size single-layer graphene device with a gate electrode, which can modulate the transmission of terahertz and infrared waves. Using time-domain terahertz spectroscopy and Fourier-transform infrared spectroscopy in a wide frequency range (10–10 000 cm–1), we measured the dynamic conductivity change induced by electrical gating and thermal annealing. Both methods were able to effectively tune the Fermi energy, EF, which in turn modified the Drude-like intraband absorption in the terahertz as well as the “2EF onset” for interband absorption in the mid-infrared. These results not only provide fundamental insight into the electromagnetic response of Dirac fermions in graphene but also demonstrate the key functionalities of large-area graphene devices that are desired for components in terahertz and infrared optoelectronics.