The local atomic structure of graphene oxide has been probed using synchrotron radiations. Detailed investigations of recently proposed simplistic model of graphene oxide using x-ray absorption near edge spectroscopy have been performed. X-ray diffraction measurements and calculations indicate loss of coherence between graphene-like layers. However, larger in-plane structural coherence is understood to be present. Selected area electron diffraction measurements indicate the presence of graphitic regions in graphene oxide which is expected to produce interesting confinement effects in graphene oxide which could be important for the development of tunable electronic and photonic devices.

A study of the local structure of graphene oxide is presented. Graphene oxide is understood to be partially oxidized graphene. Absorption peaks corresponding to interlayer states suggest the presence of pristine graphitic nanoislands in graphene oxide. Site-projected partial density of states of carbon atoms bonded to oxygen atoms suggests that the broadening of the peak due to interlayer states in the carbon K-edge spectrum of graphene oxide is predominantly due to formation of epoxide linkages. Density functional theory suggests that multilayers of graphene oxide are linked by peroxide-like linkages. SECTION Nanoparticles and Nanostructures

Stanene is one of most important of 2D materials due to its potential to demonstrate room temperature topological effects due to opening of spin-orbit gap. In this pursuit we report synthesis and investigation of optical properties of stanene up to few layers, a two-dimensional hexagonal structural analogue of graphene. Atomic scale morphological and elemental characterization using HRTEM equipped with SAED and EDAX detectors confirm the presence of hexagonal lattice of Sn atoms. The position of Raman peak along with the inter-planar ‘d’ spacing obtained from SAED for prepared samples are in good agreement with that obtained from first principles calculations and confirm that the sheets are not (111) α-Sn sheets. Further, the optical signature calculated using density functional theory at ~191 nm and ~233 nm for low buckled stanene are in qualitative agreement with the measured UV-Vis absorption spectrum. AFM measurements suggest interlayer spacing of ~0.33 nm in good agreement with that reported for epitaxial stanene sheets. No traces of oxygen were observed in the EDAX spectrum suggesting the absence of any oxidized phases. This is also confirmed by Raman measurements by comparing with oxidized stanene sheets.

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The effect of electron confinement due to the formation of graphitic islands in graphene oxide has been studied using optical techniques. Photoluminescence studies indicate a strong ultraviolet (UV) emission at ∼356 nm along with a broadened feature in the green region of the visible electromagnetic spectrum. Strong UV emission suggests probable application of graphene oxide in photodynamic therapy and nanophotonic devices.

The extraordinary success of graphene in various applications has led to the quest to innovate techniques for production and patterning of nanomaterials. Numerous techniques such as vapor deposition, epitaxial growth, mechanical and chemical exfoliation have been explored to achieve this goal. These new methods have enabled the synthesis of a monolayer to a few layer graphene structures, in various forms such as films, nanoribbons, and 3D nanocomposites that are dispersed in solutions, suspended or deposited on substrates. However, several challenges still exist in processing graphene for futuristic device fabrication. Thus, there is a need to review the traditional processing and synthesis techniques developed for obtaining graphene. This review will provide a solid foundation on technology development for achieving economical and high throughput synthesis of high quality graphene for scalable applications. In this review, we provide a brief discussion on the theory of graphene, discuss synthesis techniques along with conventional and recent approaches to pattern graphene structures, and conclude with an emphasis on direct patterning methods. Discussions on the properties of graphene produced using different techniques and their emerging applications will assist in selecting an appropriate methodology for achieving desired properties in graphene. This is expected to be instrumental in the development of new strategies for fabrication of futuristic graphene-based devices.

A study of the structural stability of boron nanoribbons is presented. Antiaromatic instabilities are found to destabilize boron nanoribbons. Our studies suggest that nanoribbons obtained from "α sheets" are more stable than those from reconstructed {1221} sheets and traditional triangular boron sheets. The stability of the nanoribbons increases with an increasing ribbon width resulting in an increased hole density (η) and, hence, an increased number of hexagonal motifs in the nanoribbon. The boron nanoribbons formed are mostly metallic; however, semiconducting structures have also been observed.

A novel quasi-two-dimensional phase of carbon and the formation of a metastable hexagonal phase of single-walled carbon nanotubes (SWCNTs) have been investigated using density functional theory (DFT) by subjecting the SWCNT bundles to hydrostatic pressure. The chirality of the nanotubes determines the breaking of symmetry of the nanotubes under compression. Interestingly SWCNTs are found to undergo a mixture of sp(2) and sp(3) hybridization and are found to form novel interacting quasi-two-dimensional sheets of interlinked SWCNTs under hydrostatic pressure. Symmetry breaking, leading to the formation of highly directional bonds at stressed edges, is found to play an important role in the interlinking of the nanotubes. (3n + 3, 3n + 3) SWCNTs are found to acquire a hexagonal cross-section when subjected to hydrostatic pressures. The opening of a pseudogap is observed for small as well as large diameter armchair SWCNTs in nanotube bundles. Equilibrium separations calculated using the Leonard-Jones potentials indicate excellent agreement with the predictions of density functional calculations and experimental observations.