Direct observation of an intermediate state for a surface photochemical reaction initiated by hot electron transfer

The photoinduced charge transfer that had been suggested to result in the dissociation of phenol on Ag(111) was investigated by two-photon photoemission spectroscopy. An unoccupied intermediate state was positively identified, which was found to be located 3.22 eV above the Fermi level. From the photoelectron energy dispersion, the effective mass of the intermediate state was determined to be (15 +/- 10)m(e) for a 1 ML coverage of phenol. This implies that the excited electron is localized mainly on the adsorbed phenol, forming a molecular resonance state. Polarization dependence of the photoelectron intensity suggested that the initial photoexcitation of the substrate produces hot electrons that scatter into the molecular resonance state, leading ultimately to the dissociation of the adsorbate. These results are the first two-photon photoemission study to characterize the transient anionic state involved in photodissociation of a molecule adsorbed on a metal surface.     

Structural and functional stabilities of artificially designed DNA ultra-thin films grown by silica Assistance

We report the structural and functional stabilities of artificially synthesized DNA ultra-thin films. Fully covered DNA ultra-thin films on a silica substrate were fabricated by the silica-assisted growth method and those samples were then incubated in various chemicals and physical conditions. The DNA ultra-thin films showed high maintainability under those harsh conditions and these results would aid to facilitate the use of artificial DNA ultra-thin films in advanced research areas such as biophotonics and bioelectronics.     

Preprocessed barley,rye, and triticale as a feedstock for an integrated fuel ethanol-feedlot plant

Rye, triticale, and barley were evaluated as starch feedstock to replace wheat for ethanol production. Preprocessing of grain by abrasion on a Satake mill reduced fiber and increased starch concentrations in feedstock for fermentations. Higher concentrations of starch in flours from preprocessed cereal grains would increase plant throughput by 8–23% since more starch is processed in the same weight of feedstock. Increased concentrations of starch for fermentation resulted in higher concentrations of ethanol in beer. Energy requirements to produce one L of ethanol from preprocessed grains were reduced, the natural gas by 3.5–11.4%, whereas power consumption was reduced by 5.2–15.6%.     

A new phenolic compound from Phedimus middendorffianus with antiproliferative activity

Abstract

A new phenolic compound (1) and together with 12 known compounds–eight flavonoids (2?～?9), two phenolic compounds (10 and 11) and two benzoic acid (12 and 13)–were isolated from Phedimus middendorffianus (Maxim.). The structures of all compound were determined on the basis of spectroscopic (MS and NMR) analyses. Compounds 4, 5, 7 and 11?～?13 were showed anti-proliferative activities against MCF-7 than PC-3 cell line. Also compound 12 and 13 showed the significant cytotoxic activities against two cancer cell lines, PC-3 and MCF-7.     

In vitro and short-term in vivo characteristics of a Kel-F thin film modified glucose sensor.

A new outer layer composition, consisting of polytetrafluoroethylene (PTFE), Kel-F oil, and Nafion, is suggested to minimize the detrimental effect of dissolved oxygen and to extend the linear response range of a glucose oxidase(GOx)-based sensor using nonconducting polymer. The morphology of Kel-F/PTFE/Kel-F/Nafion polymeric laminate was followed during fabrication by SEM. When Kel-F film was formed on the PTFE outer layer, the linear response was extended to 21 mM, at a sensitivity of 2.8 +/- 0.8 nA/mM mm2. We demonstrate that a sensor without Kel-F/PTFE/Kel-F/Nafion outer layer is relatively oxygen dependent, whereas by comparison a sensor with Kel-F/PTFE/Kel-F/Nafion outer layer is oxygen independent. The current of such a glucose sensor implanted in the subcutaneous tissue stabilized within 60 min, and the lag between blood glucose changes and sensor output was within 1 min. The in vivo characteristics of the glucose sensor described show great promise for one-point in vivo calibration.     

Coverage‐Dependent Variation of Adsorption Configurations of Methionine on Ge(100)

The adsorption configurations of methionine molecules on the Ge(100) surface have been studied by using DFT calculations, core‐level photoemission spectroscopy (CLPES), and low‐energy electron diffraction (LEED) to scrutinize the adsorption structure as a function of coverage. At first, we obtained two important and stable structures. One is the most stable structure between these structures described as an “O H dissociated‐N dative‐S dative‐bonded structure” and the other is a less stable adsorption structure of these indicating an “O H dissociated‐S dative‐bonded structure” by using DFT calculations. We also performed CLPES to clarify our DFT calculation results. Through the spectral analysis of the S 2p, C 1s, N 1s, and O 1s core‐level spectra, we acquired the reasonable results that also revealed quite different bonding configurations depending on the methionine coverage. At low coverage (ca. 0.30 ML), a single type of sulfur and charged nitrogen peaks, which indicate an “O H dissociated‐N dative‐S dative‐bonded structure”, were observed. On the other hand, two types of sulfur peaks with thiol formation and two nitrogen peaks with neutralized and charged characteristics were monitored at a higher coverage (0.60 ML and above), which can be described as an “O H dissociated‐S dative‐bonded structure”. Hence, we can clearly demonstrate that our results obtained from CLPES spectra and DFT calculations are matched well with each other. Moreover, we additionally confirmed that the relative population of the two types of thiols and amines being included in methionine in between half monolayer induces a surface reorientation in the ordering from 2×1 to 1×1 employing LEED. This interesting variation of the methionine adsorbed on the Ge(100) surface by coverage dependence will be precisely discussed by using DFT calculations, CLPES, and LEED.     

Diclofenac sodium-loaded solid lipid nanoparticles prepared by emulsion/solvent evaporation method

The preparation of solid lipid nanoparticles (SLNs) suffers from the drawback of poor incorporation of water-soluble drugs. The aim of this study was therefore to assess various formulation and process parameters to enhance the incorporation of a water-soluble drug (diclofenac sodium, DS) into SLNs prepared by the emulsion/solvent evaporation method. Results showed that the entrapment efficiency (EE) of DS was increased to approximately 100% by lowering the pH of dispersed phase. The EE of DS-loaded SLNs (DS-SLNs) had been improved by the existence of cosurfactants and increment of PVA concentration. Stabilizers and their combination with PEG 400 in the dispersed phase also resulted in higher EE and drug loading (DL). EE increased and DL decreased as the phospholipid/DS ratio became greater, while the amount of DS had an opposite effect. Ethanol turned out to be the ideal solvent making DS-SLNs. EE and DL of DS-SLNs were not affected by either the stirring speed or the viscosity of aqueous and dispersed phase. According to the investigations, drug solubility in dispersion medium played the most important role in improving EE.     

Interfacial electron dynamics and hot-electron-driven surface photochemistry of carbon tetrachloride on Ag(111)

We used time-resolved two-photon photoemission (2PPE) spectroscopy to investigate the photochemical behavior, the interfacial electronic structure, and the fate of photogenerated hot electron for carbon tetrachloride adsorbed on Ag(111). The photodissociation cross section was determined over a wide range of photon energy from 1.62 to 5.69 eV, which suggested a low-lying electron affinity level of adsorbed CCl4. A CCl4-derived unoccupied state located at 3.41 eV above the Fermi level was attributed to an image potential (IP) state based on its binding energy and effective mass. Polarization dependence of the 2PPE signal revealed that the IP state was populated by an indirect excitation process involving scattering of photoexcited hot electrons rather than direct electronic transition from a bulk band. The lifetime of the IP state was much shorter on the CCl4-covered Ag(111) surface than on the clean one, implying that the electron in the IP state is scavenged effectively by CCl4, probably through dissociative attachment to it. These results are significant in the sense that they provide dynamical evidence for a new relaxation pathway of the IP state in addition to the more common pathway involving back transfer of electron to the substrate.     

Electron solvation and solvation-induced crystallization of an ammonia film on Ag(111) studied by 2-photon photoemission

Intermolecular interaction plays a crucial role in electron solvation in the condensed phase. Here, we present a femtosecond time-resolved and angle-resolved 2-photon photoemission (2PPE) study on the dynamics of electron solvation in a 2-dimensional ammonia film on a metal substrate. While the weakly chemisorbed first monolayer (ML) supports delocalized image-potential (IP) states that resemble those of the bare Ag(111) substrate, an additional monolayer localizes the IP state with a larger binding energy obtained through a pre-solvation process. Structural disorder in the metastable ammonia films (>2 ML) leads to a prominent photoelectron peak that is attributed to the long-lived trapped electron state (e(T)) located at 1.5 eV above the Fermi level. Photoinduced crystallization of the metastable phase, verified by the recovery of a delocalized IP state, is suggested to result from inelastic scattering between interfacial electrons and disordered ammonia molecules.     

Single molecular stamping of a sub-10-nm colloidal quantum dot array

We introduce a nanoscale stamping technique of sub-10-nm colloidal quantum dot (QD) arrays to highly localized areas of three-dimensional nanostructures using a quartz tuning fork employed as the stamp pad (the "Nano Stamp"). CdSe/ZnS core-shell nanoparticles with diameters of 9.8 nm were deposited on microfabricated silicon probe tips. The number of transferred QDs, which ranged from several thousands down to single molecular order (less than 10), was precisely controlled by adjusting the stamping depths and angles. The stamping areas were varied from 1.2 microm x 1.2 microm down to 30 nm x 30 nm. Using the Nano Stamp, QDs can be transferred to a variety of protruding nanostructures. The amount of particles transferred to the tip was assessed by fluorescence intensity measurements, and the number of particles was estimated by direct transmission electron microscopy (TEM) observation. Correlation between the fluorescence intensity and the observed stamping depth and the approaching angle of the tip was found, demonstrating the efficacy of our Nano Stamp technique.