Li, Zhiting (2016) ENVIRONMENTAL AND SUBSTRATE EFFECT ON THE SURFACE PROPERTIES OF GRAPHENE AND GRAPHITE. Doctoral Dissertation, University of Pittsburgh. (Unpublished)
|PDF (PhD dissertation by Zhiting Li)|
This dissertation is focused on understanding and controlling of surface properties of graphene and graphite. Four specific topics are presented: 1) study the intrinsic wettability of graphene; 2) minimize the airborne hydrocarbon contamination on graphitic surface during storage; 3) investigate the anti-corrosion performance of graphene during a long-term ambient oxidation process at room temperature; 4) study the catalytic effect of copper substrate during the atmospheric oxidation of graphene at high temperature. All the results have important implications for the characterization, processing, and storage of graphene (graphite) samples and related devices.
Specifically, chapter 2 reports the intrinsic wettability of graphene and the effect of airborne hydrocarbon contamination during its storage. This work overturned the long-held view that graphitic surfaces (including graphene and graphite) are hydrophobic. In chapter 3, efforts have been made to minimize the airborne hydrocarbon adsorption during the storage of graphitic surfaces, this work aimed at maintaining the intrinsic property of graphene and graphite surfaces over a long period of air exposure. Chapter 4 and 5 aimed to elucidate the mutual interactions between graphene and copper substrate during ambient air exposure as well as atmospheric oxidation at high temperature. This work is closely related to the potential application of graphene as an anti-corrosion film for metallic substrates.
|Item Type:||University of Pittsburgh ETD|
|Date:||21 January 2016|
|Defense Date:||26 October 2015|
|Approval Date:||21 January 2016|
|Submission Date:||30 October 2015|
|Access Restriction:||No restriction; Release the ETD for access worldwide immediately.|
|Number of Pages:||162|
|Institution:||University of Pittsburgh|
|Schools and Programs:||Dietrich School of Arts and Sciences > Chemistry|
|Degree:||PhD - Doctor of Philosophy|
|Thesis Type:||Doctoral Dissertation|
|Uncontrolled Keywords:||graphene and graphite; surface wetting; hydrocarbons adsorption; anti-corrosion; catalytic oxidation; water adsorption|
|Date Deposited:||21 Jan 2016 16:29|
|Last Modified:||15 Nov 2016 14:30|
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Lin, Liangxu (2013) The Preparation and Characterisation of Graphene and Its Analogues. PhD thesis, University of Sheffield.
The studies in this thesis give deep insights on the large scale preparation of graphene and the fabrication and properties of novel monolayered quantum dots (QDs). Graphene has received remarkable attention due to its interesting physical and chemical properties. Among various preparations for graphene, the solvothermal deoxidation of graphene oxide (GO) is highly attractive as it potentially offers a relatively economical and scalable manufacturing route for use in industrial applications. Unfortunately, the deep deoxidation of GO and highly dispersable reduced GO (rGO) are difficult to achieve using this approach, although the reasons for this deoxidation remain unclear. This thesis shows that the agglomeration/self-assembly of partially reduced GO (p-rGO) sheets in the solvothermal deoxidation reaction suppresses the deep deoxidation of GO and led to low dispersibility/electrical conductivity of the product. By tuning the surface energy of the solvent to minimize the surface enthalpy of the dispersion, these technical problems can be ameliorated and full deoxidation of GO with high dispersibility and electrical conductivity achieved. In this thesis, an alternative novel and effective route to fabricating graphene QDs (GQDs, lateral size ~ 20 nm) is also described. This technique of delaminating layered structures has also been developed to produce monolayered QDs of boron nitride (BN, lateral size of ~ 10 nm), tungsten disulfide (WS2, lateral size ~ 8-15 nm) and molybdenum disulfide (MoS2, lateral size of ~ 8-20 nm). This has opened up many opportunities in studying these interesting materials with reduced dimensions, with new behaviours and properties emerging from the various QDs. The zigzag edges of GQDs led to the appearance of new band gaps and give strong blue-green luminescence centred at 420 nm wavelength (quantum yield of ~7.6%). In monolayered BN QDs, carbene-replaced zigzag edges, carbon-replaced N vacancy point and BOx- (x = 1 and 2) species added new luminescence at around 425 nm wavelength (quantum yield of ~2.5%). Strong luminescence was created by the reduced dimensions of WS2 and MoS2 monolayered QDs causing them to became direct semiconductors. The reduced lateral dimensions also caused marked quantum confinement effects to arise, such as large blue shifts in absorption features of BN, WS2 and MoS2 monolayered QDs. The formation of monolayered WS2 and MoS2 QDs also led to their valance bands being split by giant spin-orbit coupling effects to a far greater degree than is observed form monolayered sheets. The studies suggest strongly that these features are likely to be tunable with lateral dimensions, which makes the QDs potentially very interesting for applications. Although these uses may include spintronics, optoelectronics and even quantum computing, their application in biology is demonstrated by all the monolayered QDs being used as non-toxic fluorescent labels in confocal microscopy of biological cells.