Phosphorene is a promising two dimensional (2D) material with a direct band gap, high carrier mobility, and anisotropic electronic properties. Phosphorene-based electronic devices, however, are found to degrade upon exposure to air. In this paper, we provide an atomic level understanding of stability of phosphorene in terms of its interaction with O 2 and H 2 O. The results based on density functional theory together with first principles molecular dynamics calculations show that O 2 could spontaneously dissociate on phosphorene at room temperature. H 2 O will not strongly interact with pristine phosphorene, however, an exothermic reaction could occur if phosphorene is first oxidized. The pathway of oxidation first followed by exothermic reaction with water is the most likely route for the chemical degradation of the phosphorene-based devices in air.
Interactions of DNA oligomers with
two categories of semiconducting
nanostructureschalcogenide quantum dots (QDs) and boron nitride
nanotubes (BNNTs)owing to their widespread presence in bio-inspired
processes are investigated using the first-principles density functional
theory and continuum solvent model. The chalcogenide QDs interact
strongly at their metal centers featuring electrostatic interaction
with DNA oligomers at oxygen or nitrogen site, while BNNTs form covalent
bonds with DNA oligomers at multiple surface sites. It is found that
the different bonding nature leads to distinctly different response
to the aqueous environment; the presence of solvent drastically reduces
the binding strength of nucleobases with the QDs due to the strong
electrostatic screening. This is not the case with BNNTs for which
the covalent bonding is barely affected by the solvent. This study
thus clearly shows how a solvent medium influences chemical interactions
providing guidance for technological applications of bioconjugated
systems.
A series of charge-transfer complexes in which the electron donor was one of the polymers: polystyrene, poly-a-vinylnaphthalene, polyacenaphthylene or polyvinyl mesitylene, and the electron acceptor was one of the species : tetracyanoethylene, tetrachloro-p-benzoquinone (chloranil), 2,3dichloro-5,6-dicyano p-benzoquinone, or silver perchlorate, have been prepared and examined in the solid state. For the polyvinylnaphthalene-tetracyanoethylene system the complexes with a stereoregular (isotactic) polymer have also been prepared and examined. All the complexes prepared showed an exponential variation of specific conductivity with temperature in the range
20-75°C.Values of E and loglo 00 calculated from u = 00 exp (--E/XT) were not found to be very sensitive to the proportion of the two components in the complexes. Seebeck coefficients were measured for certain of the materials and showed thc majority current carriers to be positively charged. From a combination of the conductance and Seebeck coefficient data the carrier concentration and mobility have been calculated for these materials. In solution, spectra showing charge-transfer absorption bands are recorded for the polymers poly-a-vinyl naphthalene and polyvinylmesitylene behaving as electron donors and tetracyanoethylene, or tetrachlorobenzoquinone (chloranil) behaving as acceptors. The spectrum of one chloranil complex is also recorded in the solid state. Spectra in the solid state are also recorded for complexes in which polyvinyl naphthalene and polystyrene behaved as n electron donors and silver ion was electron acceptor. In these spectra no new absorption bands appeared but a slight red shift of the long wavelength edge of the aromatic absorption band occurred, together with a considerable increase in the intensity of absorption in comparison with the parent polymeric molecule.
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