Graphene and monoatomic boron nitride as members of the new class of two dimensional materials are discussed in this thesis. Since the discovery of graphene in 2004, various aspects of this one atom thick material have been studied with previously unexpected results. Out of many outstanding amazing properties of graphene, its elastic properties are remarkable as graphene can bear strain up to 20% of its actual size without breaking. This is the record value amongst all known materials. In this work experiments were conducted to study the mechanical behaviour of graphene under compression and tension. For this purpose graphene monolayers were prepared on top of polymer (PMMA) substrates. They were then successfully subjected to uniaxial deformation (tension- compression) using a micromechanical technique known as cantilever beam analysis. The mechanical response of graphene was monitored by Raman spectroscopy. A nonlinear behaviour of the graphene G and 2D Raman bands was observed under uniaxial deformation of the graphene monolayers. Furthermore the buckling strength of graphene monolayers embedded in the Polymer was determined. The critical buckling strain as the moment of the final failure of the graphene was found to be dependent on the size and the geometry of the graphene monolayer flakes. Classical Euler analysis show that graphene monolayers embedded in the polymer provide higher values of the critical buckling strain as compared to the suspended graphene monolayers. From these studies we find that the lateral support provided by the polymer substrate enhances the buckling strain more than 6 orders of magnitude as compared to the suspended graphene. This property of bearing stress more than any other material can be utilized in different applications including graphene polymer nanocomposites and strain engineering on graphene based devices. The second part of the thesis focuses on a two dimensional insulator, single layer boron nitride. These novel two dimensional crystals have been successfully isolated and thoroughly characterized. Large area boron nitride layers were prepared by mechanical exfoliation from bulk boron nitride onto an oxidized silicon wafer. For their detection, it is described that how varying the thickness of SiO2 and using optical filters improves the low optical contrast of ultrathin boron nitride layers. Raman spectroscopy studies are presented showing how this technique allows to identify the number of boron nitride layers. The Raman frequency shift and intensity of the characteristic Raman peak of boron nitride layers of different thickness was analyzed for this purpose. Monolayer boron nitride shows an upward shift as compared to the other thicknesses up to bulk boron nitride. The Raman intensity decreases as the number of boron nitride layers decreases. Complementary studies have been carried out using atomic force microscopy. With the achieved results it is now possible to successfully employ ultrathin boron nitride crystals for precise fabrication of artificial heterostrutures such as graphene-boron nitride heterostrutures.

Polyhedral boranes and carboranes have acquired their popularity for constructing meso and nano-size structures for an array of applications from pharmaceuticals to material science. These three-dimensional boranes range from 4 to 22 boron atom per molecules with delocalized bonding analogous to aromatic compounds. The unique vibrational spectroscopy of the BH function allows for possible application of these species to bioimaging. Silver nanoparticles functionalized with ortho-carboranes have been reported for bioimaging using Surface-enhanced Raman scattering (SERS). The silver nanoparticles were functionalized with antibodies specific to cancer cell receptors. Bonding thiol-substituted carboranes to these particles allowed for observation of enhanced Raman signals as the imaging mode. Here, attempts to synthesize second generation carborane molecules with additional Raman-active group such as nitrile were conducted. Hybrid diblock copolymers have the ability to self-assemble in different morphological patterns depending on the type and ratio of monomers and the compatibilities in various solvents. Linear hybrid diblock copolymers were synthesized by ring-opening metathesis polymerization (ROMP) reactions with norbornenyl-based decaborane and various amounts of norbornene and norbornenyl-ester derivative monomers. Their self-assembly behaviour in various solvents were characterized by NMR, TGA, DSC, and SEM. P(norbornene)60-b-p(norbornenyl-decaborane)40 polymers showed lamellar morphology patterns when slowly evaporated from chloroform. Based on results and the SEM images, a few of these diblock copolymers were used as ceramic precursors and pyrolyzed to elevated temperatures forming boron nitride and boron carbonitride nano-ordered ceramics

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published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Cubic boron nitride (cBN) thin films offer attractive mechanical and electrical properties. The synthesis of cBN films have been deposited using both physical and chemical vapor deposition methods, which generate internal residual, stresses that result in delamination of the film from substrates. Boron nitride films were deposited using electron beam evaporation without bias voltage and nitrogen bombardment (to reduce stresses) were characterize using FTIR, XRD, SEM, EDS, TEM, and AFM techniques. In addition, a pin-on-disk tribological test was used to measure coefficient of friction. Results indicated that samples deposited at 400°C contained higher cubic phase of BN compared to those films deposited at room temperature. A BN film containing cubic phase deposited at 400°C for 2 hours showed 0.1 friction coefficient.

Thesis advisor: Dunwei Wang / Water splitting has been recognized as a promising solution to challenges associated with the intermittent nature of solar energy for over four decades. A great deal of research has been done to develop high efficient and cost-effective catalysts for this process. Among which tantalum nitride (Ta₃N₅) has been considered as a promising candidate to serve as a good catalyst for solar water splitting based on its suitable band structure, chemical stability and high theoretical efficiency. However, this semiconductor is suffered from its special self-oxidation problem under photoelectrochemical water splitting conditions. Several key unique properties of graphitic carbon nitride (g-C₃N₄) render it an ideal choice for the protection of Ta₃N₅. In this work, Ta₃N₅/g-C₃N₄ hybrid photoanode was successfully synthesized. After addition of co-catalyst, the solar water splitting performance of this hybrid photoanode was enhanced. And this protection method could also act as a potential general protection strategy for other unstable semiconductors. / Thesis (MS) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 100-110). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). "September 2008." Includes bibliographical references (p. [190]-210). Also available via the World Wide Web.