Interference effects on (e, 2e) electron momentum profiles of CF4

Interference effects on electron momentum profiles have been studied using binary (e, 2e) spectroscopy for the three outermost molecular orbitals of CF(4), which are composed of the F 2p nonbonding atomic orbitals. An analysis of the measured spherically averaged electron momentum densities has clearly shown the presence of oscillatory structures having direct information about the internuclear distance between the F atoms. Furthermore, it is demonstrated that the phase of the oscillatory structures depends upon the orientation in space of the constituent atomic orbitals.     

Sonochemical synthesis, photocatalytic activity and optical properties of silica coated ZnO nanoparticles

In this paper, we report the synthesis of silica coated ZnO nanoparticles by ultrasound irradiation of a mixture of dispersion of ZnO, tetraethoxysilane (TEOS), and ammonia in an ethanol-water solution medium. The silica coating layer formed at the initial TEOS/ZnO loading of 0.8 for 60 min ultrasonic irradiation was uniform and extended up to 3 nm from the ZnO surface as revealed from HR-TEM images. Silica coated ZnO nanoparticles demonstrated a significant inhibition of photocatalytic activity against photodegradation of methylene blue dye in aqueous solution. The effects of silica coating on the UV blocking property of ZnO nanoparticles were also studied.     

Energy conversion process from the photoexcited electronic states studied by the temperature lens and acoustic peak delay methods in solution

Ultrafast temperature rise after the deactivation of the electronically excited state of 2-hydroxybenzophenone in various solvents is investigated by two photothermal techniques; temperature lens and acoustic peak delay methods, and by the population grating technique. The results from these methods show that the thermalization process takes place by two phases; fast (<1 ps) and rather slow (30 ps) processes. From the solvent dependence of the thermalization rate, we suggest that these processes are related with the intermolecular interaction and the solvation structure around the photoexcited molecules.     

Synthesis of Te-alkyl carbamotelluroates from tellurium,carbon monoxide,amines, and alkyl halides

Lithium amides reacted with tellurium under atmospheric pressure of carbon monoxide to yield lithium carbamotelluroates which were trapped with alkyl halides to give Te-alkyl carbamotelluroates in good yields. Results of control experiments suggested that lithium carbamotelluroates were formed by the reaction of tellurium with carbamoyllithiums generated in situ from lithium amides and carbon monoxide. It was revealed also that yields were improved when tellurium was preliminarily treated with lithium amides prior to the introduction of carbon monoxide into the reaction media.     

Step bunching behaviour on the {0 0 0 1} surface of hexagonal SiC

Surface topography of the {0 0 0 1} facet plane of as-grown 6H- and 4H-SiC crystals was studied ex situ by Nomarski optical microscopy (NOM) and atomic force microscopy (AFM). The surface polarity and the polytype of grown crystals largely affect the growth surface morphology of SiC{0 0 0 1} via differences in several thermodynamic and kinetic parameters. NOM observations revealed giant steps of a few micrometers in height on the {0 0 0 1} growth facet, and it was found that a morphological transition of the growth facet occurred when the growth conditions were changed. AFM imaging of the stepped structure of SiC{0 0 0 1} detected steps of height equal to the unit c-lattice parameter (c=1.512 nm for 6H-SiC and 1.005 nm for 4H-SiC). They are fairly straight and very regularly arranged, giving rise to equidistant step trains. Upon nitrogen doping, these regular step trains on the 6H-SiC(0 0 0  )C and 4H-SiC(0 0 0  )C surfaces became unstable: the equidistant step trains were transformed into meandering macrosteps of height greater than 10 nm. In this paper, we discuss the mechanism of macrostep formation (step bunching) on the SiC{0 0 0 1} surfaces through the consideration of the interplay between step energetics (repulsive step interaction) and kinetics (asymmetric step kinetics) on the growing crystal surface and elucidate how they affect the growth surface morphology of the SiC{0 0 0 1} facet.     

Synergy of organic dyes for KDP crystal growth

Single potassium dihydrogen phosphate (KDP) crystals were grown in a supersaturated solution containing an organic dye (sunset yellow FCF, brilliant blue FCF, and sky blue). The growth rate, morphology, and impurity dye distribution of faces, (100) and (101) in a KDP crystal were measured as dye concentration and the supersatutation of KDP were changed. Complete expressions for the effect of dye on all aspects of the growth of KDP crystals were discussed. The growth rates of (100) and (101) faces were well correlated by the empirical equation, and resulted in good estimation of the morphology. The distribution of dye in a KDP crystal was represented by the distribution model containing the minimum growth rate for coloring. The growth rate equation and distribution equation were expressed by functions of the supersaturation and dye concentration, and they could effectively provide the operational conditions with coloring the KDP crystal. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Development of polymer‐based lithium secondary battery

Novel polymer composites based on polydisulfide compounds are developed as a high energy density cathode material for lithium rechargeable batteries. A polymer composite composed of 2,5‐dimercapto‐1,3,4‐thiadiazole (DMcT) and conducting polymer polyaniline (PAn) on a copper current collector provides high charge density exceeding 225Ah/kg‐cathode with average discharge voltage at 3.4V. The composite cathode showed excellent rate capability and cyclability (>500 cycles). Surface analysis and electrochemical studies indicate that a DMcT‐Cu complex plays an important role in the observed improvement of the battery performances with a copper current collector. Large increase in the charge density to 550Ah/kg‐cathode is achieved by adding elemental sulfur (S₈) to the DMcT/PAn composite cathode.     

Formation of 1,1,2,3,3-pentakis(arylthio)-1-propenes from tris(arylthio)cyclopropenyl cations and their conversion into 1,1,2,5,6,6-hexakis(arylthio)-(3E)-1,3,5-hexatriene

The reaction of tetrachlorocyclopropene (1) with arenethiols (2a–e), followed by treatmentwith perchloric acid, gave tris(arylthio)cyclopropenylium perchlorates (3a–c and e), 1,1,2,3,3-pentakis(arylthio)-1-propenes (4a–d), and 2,3,3-tris(arylthio)propenals (5a–d). The structures of tris(phenylthio)cyclopropenylium perchlorate (3a), 1,1,2,3,3-pentakis(phenylthio)-1-propene (4a), and 2,3,3-tris(o-tolylthio)propenal (5b) were analyzed by single-crystal X-ray diffraction studies. The yields depended significantly on the electron-withdrawing property of the substituents of the arenethiols and the molar ratio of 2 to 1. The reaction with 2,6-dimethylbenzenethiol (2e) gave only tris(2,6-dimethylphenylthio)cyclopropenylium perchlorate (3e) without the formation of 4e and 5e. Compounds 5a–d were produced by acid hydrolysis of 4a–d. Pyrolysis of 4a–d gave (3R,4S)-1,1,2,3,4,5,6,6-octakis(arylthio)-1,5-hexadienes (9a–d) and 1,1,2,5,6,6-hexakis(arylthio)-(3E)-1,3,5-hexatrienes (10a–d) together with diaryl disulfides (11a–d). Compound 10a was also produced by photolysis. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:387–397, 1998