Ultra-high-vacuum in situ electron microscopy of growth processes of epitaxial thin films

Extracts from recent results of ultra-high-vacuum in-situ electron microscopy of growth processes of epitaxial thin films are given. As a modified monolayer-by-monolayer mode, the growth process in Fe/(111)Au of the initial Frank-van der Merwe type, followed by the intrinsic γ → α transformation of Fe is mentioned. For the nucleation and growth mode, a systematic selection of epitaxial orientation according to interfacial lattice fitting, nucleation and coalescence features, the validity of Cabrera's suggestion extending Frank and van der Merwe's idea, the cluster mobility and effects of grown-in dislocations in substrate crystals are discussed on the basis of the observations.     

Quantum tautomerization in porphycene and its isotopomers: Path-integral molecular dynamics simulations

Path-integral molecular dynamics simulations have been performed for porphycene and its isotopic variants in order to understand the effect of isotopic substitution of inner protons on the double proton transfer mechanism. We have used an on-the-fly direct dynamics technique at the semiempirical PM6 level combined with specific reaction parameterization. Our quantum simulations show that double proton transfer of the unsubstituted porphycene at T = 300 K mainly occurs via a so-called concerted mechanism through the D_2h second-order saddle point. In addition, we found that both isotopic substitution and temperature significantly affect the double proton transfer mechanism. For example, the contribution of the stepwise mechanism increases with a temperature increase. We have also carried out hypothetical simulations with the porphycene configurations being completely planar. It has been found that out-of-plane vibrational motions significantly decrease the contribution of the concerted proton transfer mechanism.     

Facile synthesis of platinum nanoparticle-containing porous carbons,and their application to amperometric glucose biosensing

This study describes the facile synthesis of platinum nanoparticle-containing porous carbons (Pt/C) by carbonization of freeze-dried agarose gels containing potassium tetrachloroplatinate under a nitrogen atmosphere at 800 °C. By adjusting the ratio between agarose and platinate in the freeze-dried gels, the Pt content in the final Pt/C products could be systematically varied from 0–10 wt.%. Transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, X-ray photoelectron spectroscopy, Raman spectroscopy, and nitrogen physisorption measurements revealed that the Pt/C materials obtained by this method possess high surface areas (350–500 m² g^?1), narrow Pt nanoparticle size distributions (6 ± 3 nm) and nanocrystalline graphite –like carbon character. By immobilization of glucose oxidase on the surface of a 4 wt.% Pt/C electrocatalyst prepared by this route, a very sensitive amperometric glucose biosensor was obtained (response time <2 min, sensitivity 1.9 mA M^?1; and a linear response with glucose concentration up to 10 mM). The simplicity and versatility of the described synthetic method suggests its application to the preparation of carbon supported noble metal catalysts including palladium/C and gold/C. Figure

This study describes the facile synthesis of platinum nanoparticle-containing porous carbons (Pt/C) by carbonization of freeze-dried agarose gels containing potassium tetrachloroplatinate. The Pt/C materials exhibited excellent electrocatalytic activities, as demonstrated by their successful integration into amperometric glucose biosensor     

Holography and entanglement in flat spacetime

We propose a holographic correspondence of the flat spacetime based on the behavior of the entanglement entropy and the correlation functions. The holographic dual theory turns out to be highly nonlocal. We argue that after most part of the space is traced out, the reduced density matrix gives the maximal entropy and the correlation functions become trivial. We present a toy model for this holographic dual using a nonlocal scalar field theory that reproduces the same property of the entanglement entropy. Our conjecture is consistent with the entropy of Schwarzschild black holes in asymptotically flat spacetimes.     

Shear-Force Detection by Reusable Quartz Tuning Fork without External Vibration

Many studies have reported on the use of quartz tuning forks (a type of crystal oscillator used in wristwatches) in the detection of shear force, employed to control the distance between the probe and the sample in a scanning near-field optical microscope. This study focuses on a newly-devised shear force detection method capable of simultaneous non-external oscillation and detection, which also allows for subsequent reuse of a tuning fork. The optimum configuration and tip length for inserting a probe into the slit of a tuning fork have been elucidated. The shear force was detectable in about 5 nm decay length using such conditions.     

Preparation and properties of surface-active organocobalt complexes having long-chain alkyl groups

New types of surface-active organocobaltocenium(I) complexes, η-C_nH_2n+1X-C₅H₄(ηC₅H₅)₂Co⁺Y^? and(η-C_nH_2n+1X-C₅H₄)Co⁺Y^? (n = 6–16; X not present, NHCO or OCO; Y = Cl or PF₆) were prepared and their surface character studied. (1) The critical micelle concentrations of the cobaltocenium chlorides were much lower than those of corresponding trimethylammonium-type cationic surfactants. (2) The surface-active character of the cobaltocenium chlorides in aqueous solution (and the redox potentials of the hexafluorophosphates in acetonitrile) were affected by the substituents (X) in the cyclopentadienyl groups. (3) The surface activities of the cobaltocenium salts were lost on reduction with NaBH₄ to afford (alkyl-substituted cyclopentadiene) cyclopentadienylcobalt (0) complexes which were surface-inactive but could be re-oxidized to afford the surface-active cobaltoceium(I) salts. The cobalt complexes mentioned above may be the first examples of redoxresponsive surfactants.