Initial growth process and surface structure of Ag on Si(111) studied by low-energy Ion-Scattering Spectroscopy (ISS) and LEED-AES

The growth process of silver on a Si(111) substrate has been studied in detail by low-energy ion-scattering spectroscopy (ISS) combined with LEED-AES. Neon ions of 500 eV were used as probe ions of ISS. The ISS experiments have revealed that the growth at room temperature and at high temperature are quite different from each other even in the submonolayer coverage range. The following growth models have been proposed for the respective temperatures. At room temperature, the deposited Ag forms a two-dimensional (2D) island at around 2/3 monolayer (ML) coverage, where the Ag atoms are packed commensurately with the Si(111)1 substrate. One third of the substrate Si surface remains uncovered there. Then it starts to develop into Ag crystal, and at a few ML coverage a 3D island of bulk Ag crystal grows directly on the substrate. An intermediate layer, which covers uniformly the whole surface before the growth of Ag crystal, does not exist. At high temperatures (>~200°C), the well-known Si(111)√3-Ag layer is formed as an intermediate layer, which consists of 2/3 ML of Ag atoms and covers the whole surface uniformly. These Ag atoms are embedded in the first double layer of the Si substrate. It is concluded that the formation of the √3 structure needs relatively high activation energy which may originate from the large displacement of Si atoms owing to the embedment of the Ag atoms, and does not proceed below about 200°C. The most stable state of the Ag atoms on the outermost Si layer is in the shape of an island, both for the Si(111) surface and for the Si(111)√3-Ag surface.     

Conductive polymer-carbon-imidazolium composite: a simple means for constructing solid-state dye-sensitized solar cells

A clay-like conductive material comprising polyaniline-loaded carbon black particles and an ethyleneoxide-substituted imidazolium iodide was prepared. The material was sandwiched between dye-coated porous TiO2 and counter-electrode to form a solid-state dye-sensitized solar cell, which works with overall conversion efficiencies of 3.48% and 4.07% for AM 1.5, 100 mW cm(-2) and 23 mW cm(-2) irradiation, respectively.     

Addition of arylboronic acids to symmetrical and unsymmetrical azo compounds

[reaction: see text] The addition of aryl- and heteroarylboronic acids to azo compounds is described. Copper salt catalysis was necessary to perform the reaction under mild conditions and high yields. Excellent regioselectivity was observed in addition to unsymmetrical azo compounds.     

New procedure to mask the 2,3-pi bond of the indole nucleus and its application to the preparation of potent opioid receptor agonists with a Corynanthe skeleton

Treatment of indole alkaloids with hypervalent iodine in the presence of ethylene glycol provides 2,3-ethylene glycol bridged adducts that could be converted into the original indoles under mild reductive conditions. This procedure, which involves masking of the reactivity of the indole nucleus at the beta-position, was utilized for the modification of the benzene ring of the indoline derivative and was applied to the preparation of potent opioid receptor agonists with the Corynanthe skeleton. [reaction: see text]     

Design of Photostable,Activatable Near‐Infrared Photoacoustic Probes Using Tautomeric Benziphthalocyanine as a Platform

Near‐infrared (NIR) imaging techniques have attracted significant attention for biological and medicinal applications due to the ability of NIR to penetrate deeply into tissues. However, there are very few stable, activatable molecular probes that can utilize NIR light in the wavelength range beyond 800 nm. Herein, we report a new activatable NIR system for photoacoustic imaging based on tautomeric benziphthalocyanines (BPcs). We found that the existence of a free hydroxyl group is crucial for NIR absorption of BPcs. Synthesized water‐soluble hydroxy BPcs exhibited high photostability and no fluorescence, which are desirable features for photoacoustic imaging. We synthesized BPcs in which the free hydroxyl group was masked by an esterase‐labile or an H₂O₂‐labile group. The photoacoustic signals of these hydroxy‐masked BPcs were increased upon NIR excitation at 880 nm in the presence of esterase or H₂O₂, respectively. These are rare examples of activatable probes utilizing NIR light at around 900 nm.     

Surface-sensitive NMR in optically pumped semiconductors

We present a scheme of surface-sensitive nuclear magnetic resonance in optically pumped semiconductors, where an NMR signal from a part of the surface of a bulk compound semiconductor is detected apart from the bulk signal. It utilizes optically oriented nuclei with a long spin-lattice relaxation time as a polarization reservoir for the second (target) nuclei to be detected. It provides a basis for the nuclear spin polarizer [IEEE Trans. Appl. Supercond. 14:1635, 2004], which is a polarization reservoir at the surface of the optically pumped semiconductor that polarizes nuclear spins in a target material in contact through the nanostructured interfaces.     

Novel N,N,P-tridentate ligands for the highly enantioselective copper-catalyzed 1,4-addition of dialkylzincs to enones

Use of 0.25 mol % of the N, N, P-tridentate ligand containing the 2-quinolyl moiety ( 1 and 2) and 0.1 mol % of Cu(OTf) 2 enabled the enantioselective 1,4-addition of dialkylzincs to cyclic enones to produce 1,4-adducts in up to 99% ee.     

Formation of an exciplex with mixed ligands in the mercury-photosensitized luminescence of alcohol-amine mixtures in the liquid phase

The liquid-phase mercury-photosensitized luminescence of tert-butyl alcohol (TL)-tert-butylamine (TM) mixtures has been investigated by a steady-state illumination method over a wide range of substrate concentrations. The emission bands from exciplexes (HgTL* and HgTM*) between an excited mercury atom and an alcohol or an amine molecule were observed at about 330 nm and 370 nm, respectively, in TL and TM solutions in cyclohexane. Two other bands appeared at 405 nm and 455 nm for TM at high concentrations. These bands were previously assigned to two types of 1:2 exciplexes (HgTM(2)* and HgTM(2)**). In TL-TM mixed solutions, a new band appeared at about 400 nm. The intensity of this band increased with increasing concentrations of TL and TM. This band was attributed to an exciplex with mixed ligands (HgTLTM*). This band was observed for the first time in this study. The energized intermediate, (HgTLTM*)(not equal), formed between HgAL* and AM can be effectively stabilized by collisions with solvent molecules in solution, while it decomposes to HgAM* and AL in the gas phase. The results for TL-TM mixtures can be explained by the proposed reaction mechanism.     

Phytochemical analysis of the essential oil of Thymus serpyllum L. growing wild in Estonia

Variations in the essential oil composition of Thymus serpyllum L., growing wild in Estonia (33 samples) and in some other countries (Russia, Latvia and Armenia, seven samples) were determined. The oil were obtained from Estonia (46 samples) in yields 0.6-4.4 and 1.9-8.2 mL kg(-1) in other countries. The T. serpyllum herb grown in Estonia usually did not confirmed to the EP standard in the aspect of the essential oil contents (3.0 mL kg(-1)). Variations in the essential oil composition of wild thyme were studied using capillary gas chromatographic methods. A total of 94 components were identified. Thymol and carvacrol, mentioned in literature as principial components, are not the main components of the essential oil of wild thyme growing in Estonia. (E)-nerolidol, caryophyllene oxide, myrcene and borneol chemotypes of wild thyme drug are distinguishable. The chemical composition of samples from Russia, Latvia and Armenia is very variable.     

Application of MCD spectroscopy and TD-DFT to nonplanar core-modified tetrabenzoporphyrins: effect of reduced symmetry on nonplanar porphyrinoids

The optical spectra of a series of core-modified tetrabenzoporphyrins were analyzed to determine the effects of core modification, ligand folding, and partial benzo substitution at the ligand periphery on the electronic structure by using magnetic circular dichroism (MCD) and NMR spectroscopy, X-ray crystallography, cyclic and differential pulse voltammetry, and TD-DFT calculations. Planar 21-carba-, 21-thia-, 21,23-dithia-, and 21-oxa-23-thiatetrabenzo[b,g,l,q]porphyrins reported previously were studied together with the previously unreported 21-oxa- and 21-carba-23-thiatetrabenzo[b,g,l,q]porphyrins. The optical properties of these compounds are compared to those of tetrabenzo[b,g,l,q]-, 5,10,15,20-tetraphenyl-, 5,10,15,20-tetraphenyltetrabenzo[b,g,l,q]-21-thia-, 5,10,15,20-tetraphenyltetrabenzodithia-, 5,10,15,20-tetraphenyldibenzo[g,q]-21,23-dithia-, 5,10,15,20-tetraphenyldibenzo[b,l]-21,23-dithia-, 5,10,15,20-tetraphenyltribenzo[g,q,l]-21-thia-, and 5,10,15,20-tetraphenylbenzo[b]-21-thiaporphyrins. Michl's perimeter model and Gouterman's four-orbital model are used to conceptualize the results and to account for red shifts commonly observed in the spectral bands of nonplanar porphyrinoids.