Solid-State Growth of One- and Two-Dimensional Silica Structures on Metal Surfaces

Crystalline or vitreous silica layers are new two-dimensional (2D) nanomaterials, which have shown surprising structural similarities with graphene and promise interesting properties. In this study, one-dimensional (1D) silica structures are formed on metal surfaces. In an in situ electron microscopy experiment it is demonstrated that lines of silica grow along step edges on metal surfaces. The growth of 1D silica occurs in competition with the formation of 2D networks and adopts the crystalline symmetry of the metal surface. Transformations between 1D and 2D structures are observed. Density functional theory calculations show that 1D silica is energetically favorable over 2D structures if surface steps prevail on the substrate. Our results indicate that lateral heterostructures with interesting properties may be developed on metal substrates

<i>In Situ</i> Growth of Cellular Two-Dimensional Silicon Oxide on Metal Substrates

Crystalline hexagonally ordered silicon oxide layers with a thickness of less than a nanometer are grown on transition metal surfaces in an <i>in situ</i> electron microscopy experiment. The nucleation and growth of silica bilayers and monolayers, which represent the thinnest possible ordered structures of silicon oxide, are monitored in real time. The emerging layers show structural defects reminiscent of those in graphene and can also be vitreous. First-principles calculations provide atomistic insight into the energetics of the growth process. The interplay between the gain in silica–metal interaction energy due to their epitaxial match and energy loss associated with the mechanical strain of the silica network is addressed. The results of calculations indicate that both ordered and vitreous mono/bilayer structures are possible, so that the actual morphology of the layer is defined by the kinetics of the growth process

<i>In Situ</i> Growth of Cellular Two-Dimensional Silicon Oxide on Metal Substrates

Crystalline hexagonally ordered silicon oxide layers with a thickness of less than a nanometer are grown on transition metal surfaces in an <i>in situ</i> electron microscopy experiment. The nucleation and growth of silica bilayers and monolayers, which represent the thinnest possible ordered structures of silicon oxide, are monitored in real time. The emerging layers show structural defects reminiscent of those in graphene and can also be vitreous. First-principles calculations provide atomistic insight into the energetics of the growth process. The interplay between the gain in silica–metal interaction energy due to their epitaxial match and energy loss associated with the mechanical strain of the silica network is addressed. The results of calculations indicate that both ordered and vitreous mono/bilayer structures are possible, so that the actual morphology of the layer is defined by the kinetics of the growth process

Electrical Transport Measured in Atomic Carbon Chains

The first electrical-transport measurements of monatomic carbon chains are reported in this study. The chains were obtained by unraveling carbon atoms from graphene ribbons while an electrical current flowed through the ribbon and, successively, through the chain. The formation of the chains was accompanied by a characteristic drop in the electrical conductivity. The conductivity of the chains was much lower than previously predicted for ideal chains. First-principles calculations using both density functional and many-body perturbation theory show that strain in the chains has an increasing effect on the conductivity as the length of the chains increases. Indeed, carbon chains are always under varying nonzero strain that transforms their atomic structure from the <i>cumulene</i> to the <i>polyyne</i> configuration, thus inducing a tunable band gap. The modified electronic structure and the characteristics of the contact to the graphitic periphery explain the low conductivity of the locally constrained carbon chain

Electrical Transport Measured in Atomic Carbon Chains

The first electrical-transport measurements of monatomic carbon chains are reported in this study. The chains were obtained by unraveling carbon atoms from graphene ribbons while an electrical current flowed through the ribbon and, successively, through the chain. The formation of the chains was accompanied by a characteristic drop in the electrical conductivity. The conductivity of the chains was much lower than previously predicted for ideal chains. First-principles calculations using both density functional and many-body perturbation theory show that strain in the chains has an increasing effect on the conductivity as the length of the chains increases. Indeed, carbon chains are always under varying nonzero strain that transforms their atomic structure from the <i>cumulene</i> to the <i>polyyne</i> configuration, thus inducing a tunable band gap. The modified electronic structure and the characteristics of the contact to the graphitic periphery explain the low conductivity of the locally constrained carbon chain

Electrical Transport Measured in Atomic Carbon Chains

The first electrical-transport measurements of monatomic carbon chains are reported in this study. The chains were obtained by unraveling carbon atoms from graphene ribbons while an electrical current flowed through the ribbon and, successively, through the chain. The formation of the chains was accompanied by a characteristic drop in the electrical conductivity. The conductivity of the chains was much lower than previously predicted for ideal chains. First-principles calculations using both density functional and many-body perturbation theory show that strain in the chains has an increasing effect on the conductivity as the length of the chains increases. Indeed, carbon chains are always under varying nonzero strain that transforms their atomic structure from the <i>cumulene</i> to the <i>polyyne</i> configuration, thus inducing a tunable band gap. The modified electronic structure and the characteristics of the contact to the graphitic periphery explain the low conductivity of the locally constrained carbon chain

Investigating the thermostability of succinate: quinone oxidoreductase enzymes by direct electrochemistry at SWNTs-modified electrodes and FTIR spectroscopy

Succinate Quinone reductases (SQRs) are the enzymes which couple the oxidation of succinate and the reduction of quinones in the respiratory chain of prokaryotes and eukaryotes. We compare herein the temperature-dependent activity and structural stability of two SQRs, the first one from the mesophilic bacterium E. coli and the second one from the thermophilic bacterium T. thermophilus by a combined electrochemical and infrared spectroscopy approach. Direct electron transfer was achieved with the full membrane protein complexes at SWNTs-modified electrodes. The possible structural factors which contribute to the temperature-dependent activity of the enzymes and to the thermostability of the T. thermophiles SQR in particular, are discussed

Electron Beam Etching of CaO Crystals Observed Atom by Atom

With the rapid development of nanoscale structuring technology, the precision in the etching reaches the sub-10 nm scale today. However, with the ongoing development of nanofabrication the etching mechanisms with atomic precision still have to be understood in detail and improved. Here we observe, atom by atom, how preferential facets form in CaO crystals that are etched by an electron beam in an in situ high-resolution transmission electron microscope (HRTEM). An etching mechanism under electron beam irradiation is observed that is surprisingly similar to chemical etching and results in the formation of nanofacets. The observations also explain the dynamics of surface roughening. Our findings show how electron beam etching technology can be developed to ultimately realize tailoring of the facets of various crystalline materials with atomic precision