Spatial Effect of C?H Dipoles on the Electron Affinity of Diamond (100)‐2×1 Adsorbed with Organic Molecules

Cycloaddition of allyl organics on the dimer rows of a clean C(100)‐2×1 diamond surface can be used for the controlled functionalization of such a surface. Sticking probability measurements confirm that appreciable uptake of acetylene and butadiene occur on the clean diamond surface at room temperature. The change in electron affinity of the surface as a function of the coverage of the organic molecules is investigated with periodic DFT calculations. The presence of C? H dipoles on these adsorbates modify the surface charge density and gives rise to an induced dipolar layer that modifies the electrostatic potential outside the surface. There is a significant reduction of up to 2.5 eV in electron affinity following the chemisorption of ethylene. Therefore, the adsorbed molecules play the same role as surface hydrogen in inducing the NEA condition on the clean diamond. The change in electron affinity does not scale linearly with the coverage of the organic molecules, because the spatial profile of the C? H dipoles as well as the orientation of the molecules on the surface have a predominant effect on the surface charge density.     

Cauchy problem for semilinear wave equation with time-dependent metrics

We establish the existence of a weak solution u of the semilinear wave equation where a(t,x) is equal to 1 outside a compact set with respect to x and a non-linear term f_k which satisfies |f_k(u)|≤C|u|^k. For some non-trapping time-periodic perturbations a(t,x), we obtain the long time existence of a solution from little initial data.     

Non‐commutative ‐divergence functional

We introduce the non‐commutative f‐divergence functional for an operator convex function f, where and are continuous fields of Hilbert space operators and study its properties. We establish some relations between the perspective of an operator convex function f and the non‐commutative f‐divergence functional. In particular, an operator extension of Csiszár's result regarding f‐divergence functional is presented. As some applications, we establish a refinement of the Choi–Davis–Jensen operator inequality, obtain some unitarily invariant norm inequalities and give some results related to the Kullback–Leibler distance.     

Oxygenation of zinc dialkyldithiocarbamate complexes: isolation, characterization, and reactivity of the stoichiometric oxygenates

S-oxygenation of dithiocarbamate (DTC) complexes has been implicated in their function as industrial anti-oxidants, as well as in their use as pesticides and most recently in their cumulative toxicity, but little is known of the species generated. Several S-oxygenated derivatives of N,N-disubstituted DTCs have been synthesized, characterized by a variety of methods, and their structure and reactivity examined. Low-temperature reaction of bis(N,N-diethyldithiocarbamato)zinc(II), Zn(deDTC)2 1, with oxygenating reagents (hydrogen peroxide, m-chloroperbenzoic acid, urea hydrogen peroxide) yields mono-oxygenated DTC complexes (N,N-peroxydiethyldithiocarbamato)(N,N-diethyldithiocarbamato)zin(II), Zn(O-deDTC)(deDTC), 2 and bis(N,N-peroxydiethyldithiocarbamato)zinc(II), Zn(O-deDTC)2, 3. The tetraoxygenated derivative bis(N,N-diethylthiocarbamoylsulfinato)zinc(II), Zn(O(2)-deDTC)2, 4, was cleanly obtained by initial reaction of the DTC salts with stoichiometric oxidant prior to complexation with Zn(II). X-ray crystallographic analysis of 2, 3, and 4 show that the peroxydithiocarbamate ligands are S,O-bound. Similar derivatives were obtained from the homoleptic dimethyl and pyrollidine DTC Zn complexes. These oxygenated species display unique 1H and 13C NMR variable-temperature spectra, as the symmetry of DTC ligand is broken upon oxygenation; total line shape analysis (TLSA) was used to compare the energetic parameters for rotation about the C-N bond in several derivatives. Compounds 2, 3, and 4 were deoxygenated by alkyl phosphine, regenerating the parent dithiocarbamate 1. The peroxydithiocarbamate complexes were susceptible to base-catalyzed hydrolytic decomposition, giving ligand-based products indicative of S-oxidation and S-extrusion.     

Templated deposition of MoS2 nanotubules using single source precursor and studies of their optical limiting properties

We demonstrate a simple way of fabricating bulk quantities of molybdenum disulfide (MoS2) porous nanotubules (NTs) by templated deposition from a single source precursor based on tetrakis(diethylaminodithiocarbomato)molybdate(IV). Bulk quantities of crystalline MoS2 NTs that consist of agglomerates of nested nanocapsules were obtained by this one-step evaporation method. We found that MoS2 NTs show good optical limiting behavior with 532-and 1064-nm nanosecond laser pulses, and the size-effect of the NTs on optical transmission was observed.     

Dissipative soliton operation of an ytterbium-doped fiber laser mode locked with atomic multilayer graphene

Mode locking of an ytterbium-doped fiber laser with atomic multilayer graphene is, to the best of our knowledge, experimentally demonstrated for the first time. Dissipative solitons with duration of 580 ps at 1069.8 nm were generated. Since graphene can also be used to mode lock erbium-doped fiber lasers, our result shows that graphene indeed has wavelength-independent saturable absorption, which could be exploited to mode lock fiber lasers with various operating wavelengths.     

Biosensing properties of diamond and carbon nanotubes

The biochemical properties of boron-doped diamond (BDD), carbon nanofiber, fullerene, and multiwalled carbon nanotube (MWCNT) electrodes have been investigated comparatively. Physiochemical factors which affect the biosensing properties such as surface hydrophobicities, effective surface area, and intrinsic material properties are studied. Voltammetric responses of the as-grown thin film electrode and surface-modified electrode to biomolecules such as L-ascorbic acid (L-AA), dopamine (DA), and uric acid are examined. As-grown MWCNT electrodes exhibit selective voltammetric responses to the different biomolecules and faster electron-transfer kinetics compared to BDD. The selective response is due to the considerably lower anodic potential of L-AA on MWCNT (-48 mVvs Ag/AgCl compared to 575 mV on BDD). This electrocatalytic response can be replicated on a nonselective carbon nanofiber electrode by coating it with gold nanoparticles. BDD has no intrinsic selective response to L-AA, and surface modification by anodic polarization is necessary for resolving L-AA and DA.