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To measure electron diffusion coefficients (D) and electron lifetimes (τ) of dye-sensitized solar cells (DSC), we introduced stepped light-induced transient measurements of photocurrent and voltage (SLIM-PCV), which can simplify the optical setup and reduce measurement time in comparison to conventional time-of-flight and frequency-modulated measurements. The method was applied to investigate the influence of the viscosity of a thermally stable high-boiling-point solvent on the energy conversion efficiency of DSCs. By systematic study of the influence of the viscosity, the species of cations as the counter charge of I^-/I3^-, and the concentrations of electrolytes, we concluded that a lower dye cation reduction rate due to slower iodine diffusion is a limiting factor for a highly viscous electrolyte system. On the other hand, comparable values of D and increased values of τ were observed in a highly viscous electrolyte. By employing 0.5 M TBAI and 0.05 M I2 in propylene carbonate, the efficiency of the DSC became comparable to that of a DSC using conventional electrolytes consisting of LiI, imidazolium iodide, and 4-tert-butylpyridine in methoxyacetonitrile. The simultaneous evaluation of D and τ through the appropriately simple measurement realizes fast optimization of the efficient and reliable DSC composed of thermally stable but often viscous electrolytes.

Current−voltage characteristics, electron lifetimes (τ), and electron diffusion coefficients (D) of dye-sensitized TiO2 solar cells (DSCs) composed of liquid electrolytes were repeatedly measured over a period of time. It was found that the energy conversion efficiency of the DSCs using electrolytes composed of Li⁺ or tetrabutylammonium cation as the counter charges of I^-/I3^- redox couples decreased with the lapse of time. On the other hand, such a decrease was not observed for the DSC consisting of 1,2-dimethyl-3-propylimidazolium cation or of Li⁺ coupled with the addition of tert-butylpyridine. The decrease of the efficiency was in accordance with a decreased electron lifetime. The notable decrease in the presence of Li⁺ is probably caused by the excess amount of Li⁺ adsorption on the TiO2 surface.

Abstract: Nano-structured TiO2 electrodes, suitable for dye sensitized solid-state solar cells were prepared by a new simple spraying technique (SPT). Physical properties of these electrodes were compared with the electrodes prepared by the ‘doctor blade’ technique (typical sliding method, DB). Dye sensitized solid-state solar cells, comprising of CuI as the hole conductor, were fabricated with these electrodes and enhanced photo responses were obtained with SPT electrodes. The effects of additives, either to the spray solution or to the hole conductor on the photoresponses of the above devices were also studied. The cells fabricated with SPT electrodes containing Al(BuiO)3 showed ∼ 2.4% efficiency and addition of 1-ethyl-3-methyl imidazolium thiocyanate into CuI layer further enhanced the efficiency up to 2.75% under the irradiance of 100 mW cm−2 (AM 1.5).

As highly efficient organic sensitizers for dye-sensitized solar cells, a series of novel oligoene dyes which have different lengths of methine units, cyano groups and/or carboxylic groups as the electron acceptor units, and amino groups as the electron donor units was designed and synthesized. The bathochromic shift of the absorption spectrum was achieved by expansion of the π-conjugated system by increasing the number of methine units and by introduction of both electron-withdrawing and -accepting groups, which induced charge-transfer-type absorption character. Redox potential of the dyes was also controlled by the substitution of the functional groups. Dye-sensitized solar cells (DSCs) based on the oligoene dyes showed excellent response of incident photon to current conversion efficiency (>80%), leading to good photovoltaic performances up to 6.6% under 1 sun irradiation conditions. Femtosecond transient absorption spectroscopy in the mid-IR region revealed the very fast electron injection from the excited states of the oligoene dyes to the conduction band of TiO2. The molecular design of oligoene dye is reliable for developing novel organic sensitizers for use in dye-sensitized solar cells.

Conductive transparent thin films made of multilayer coatings consisting of three alternative layers (TiO2/Ag/TiO2, TAT) have been applied to dye-sensitized solar cells (DSCs). We have used sputtering deposition to prepare the transparent layers and measured the optical properties. Mesoporous TiO2 electrodes for DSCs were coated on TAT by a spin-coating and low-temperature sintering method. They were compared to well-known transparent metal oxide glasses (ITO and F-doped SnO2). These DSCs on the TAT coatings yielded a short-circuit photocurrent density of 9 mA/cm², a photocurrent of 700 mV, and an overall cell efficiency of 3.9% at one sun light intensity.

Radiation rates and emission quantum yields of Eu(III) were modified using asymmetric deuterated Eu(III) complexes doped in poly(methyl methacrylate) (PMMA) deuterated tris-(hexafluoroacetylacetonato)europium(III) with phospine oxide in order to produce lowthreshold levels for laser transmission and amplifier emissions. Geometric structures of asymmetric Eu(III) complexes were determined by single-crystal X-ray diffraction and Judd−Ofelt analysis. Luminescent polymers were fabricated by incorporating Eu(III) complexes in a PMMA matrix. Luminescent PMMA containing Eu(hfa-D)3(DPFBPO)2 exhibited the highest quantum yield and fastest radiation rate (quantum yield = 78 ± 6%, radiation rate =1.2 × 10³ s^-1) of the PMMA matrixes. Emission quantum yields of Eu(hfa-D)3 (TPPO)2 in acetone-d6 were found to be >95%. This radiation rate is of the same order as values reported for Nd:YAG. Prepared luminescent polymers including Eu(hfa-D)3(TPPO−F)2 showed promising results for applications to novel organic Eu(III) devices, such as organic liquid lasers, plastic lasers, and optical fibers.

Performances of dye-sensitized solar cells prepared from nanoporous TiO2 films with different TiO2 nanoparticle preparation methods and different annealing temperatures are studied with various film thicknesses. The results show that the solar cells prepared at higher annealing temperatures have higher energy conversion efficiencies. Regarding film thickness, thin film electrode solar cells annealed at low-temperature show comparable efficiencies with those of the cells annealed at high temperature. The difference of the efficiency between the cells with the film annealed at different temperatures increases with the film thickness. To explain the observations, the surface area of the films, the amount of the adsorbed dye, and the diffusion coefficient and lifetime of electrons are measured. The amount of adsorbed dye per unit area is found to be independent of annealing temperature, while the diffusion coefficient and lifetime increase with the temperature. With trapping models, the measured increases of the diffusion coefficient with annealing temperature are interpreted with the change of the charge-trap density and neck growth between particles, which are suggested by transmission electron microscope and surface area measurements of the films. Diffusion lengths of electrons for each solar cell estimated from the diffusion coefficient and lifetime increase with annealing temperature. From the comparison between the short circuit currents of the solar cells with the diffusion lengths, it is concluded that the higher efficiencies of the solar cells prepared from high-temperature annealed films are attributed to their longer diffusion lengths of electrons.

We present a stacking technique for making the stacked opaline films using the colloid multilayers as building blocks. The process of stacking was easily confirmed by monitoring the intensities and positions of Bragg diffraction peaks due to the ordered structures of the multilayers. The stacking of the same kind of multilayers led to the increased intensities of the peaks corresponding to the repeated cycles of stacking, while the stacking of the different kind of multilayers led to the overlapping of each diffraction peak. In the electrochemical deposition of nickel into the interstitial spaces of the opaline films thus obtained, we found the interesting current−time responses with the oscillatory behavior. The simple geometrical considerations of the ordered opaline structure could well explain that the periodic current oscillation was caused by the periodic changes of the electrodeposited area of the interstices. These electrochemical signals would be useful for the control of the positions and chemical compositions of deposited materials every layers and/or multilayers as building blocks.

Diffusion coefficients of electrons in mesoporous TiO2−electrolyte systems are determined by laser pulse induced photocurrent measurements in the presence of a wide range of concentration of Li⁺, Na⁺, Mg²⁺, tetrabutylammonium cation (TBA⁺), or dimethylhexylimidazolium cation (DMHI⁺) in electrolytes. The total amount of photocharge generated by a laser pulse increases in the order of DMHI⁺< TBA⁺ < Na⁺ < Li⁺. The diffusion coefficients (DAmb) increase with increasing the cation density. In the case of TBA⁺, the increase of the diffusion coefficients is interpreted with ambipolar diffusion mechanism. In the case of Li⁺, Na⁺, Mg²⁺, and DMHI⁺, each diffusion coefficient increases to some extent with the cation density as in the case of TBA⁺, but does not fit well with ambipolar diffusion mechanism with the assumption of constant diffusion coefficient and electrons at the high density of the cations. Electron diffusion in the systems is discussed in terms of the surface cation density arising from the adsorption of cations on the films.

Quasi-solid-state dye-sensitized solar cells were fabricated using low-molecular-weight gelators. They showed comparable photoenergy conversion efficiencies to the liquid cell at high illumination intensity up to AM 1.5 (1 sun). Conductivity measurements of the electrolyte phases revealed that the gelation does not affect the conductivity of the electrolyte and that the conductivity increased with an increase of iodine in both gel electrolytes and liquid electrolyte. The formation of polyiodide ions, such as I3^- and I5^-, caused by addition of iodine was confirmed by Raman spectroscopic measurement. The self-diffusion of iodide species in the gel electrolyte was found about a quarter of that of I^- in acetonitrile. The formation of less-mobile polyiodide ions in electrolyte increased the conductivity in the mesoporous phase, which should be rationalized as due to the Grotthuss-type electron exchange mechanism caused by rather packed polyiodide species in the electrolytes. The optimized quasi-solid-state cell showed the values of 0.67 V for open-circuit voltage, 12.8 mA cm^-2 for short-circuit photocurrent density, and 5.91% for photoenergy conversion efficiency under AM 1.5 irradiation with higher durability.

p-Terphenyl (TP) sensitizes photocatalytic reduction of water to H2 under UV irradiation of homogeneous aqueous acetonitrile solution in the presence of triethylamine (TEA) as an electron donor and Ru³⁺ as a precursor of cocatalyst, Ru metal colloid. The addition of quaternary onium salts enhances the H2 evolution, where the onium salts with longer alkyl groups become more effective. Dynamics studies of TP photosensitization reveal that the presence of the salts contributes to stabilization of the radical anion of TP (TP^•-) formed through reductive quenching of the singlet state of TP (¹TP*) and the triplet state of TP (³TP*) by TEA. The TP photosensitization accompanies competitive photo-Birch reduction via TP^-. , but the presence of onium salts enhances the lifetime of TP^•- through the specific interaction, leading to the effective TP-photosensitized H2 evolution.

Hexagonal ZnS nanocrystallites (ZnS−DMF(OAc); ca. 2 nm in diameter) prepared in N,N-dimethylformamide (DMF) using Zn(CH3COO)2·2H2O (Zn(OAc)2·2H2O) as the Zn²⁺ source and H2S as the sulfur source catalyzed selective photoreduction of CO2 to HCOO^- in the presence of triethylamine as an electron donor. When excess zinc acetate was added to the system, the efficiency increased while still keeping the product selectivity. The photocatalytic behavior of ZnS−DMF(OAc) is in contrast to that of ZnS−DMF(ClO4) prepared using Zn(ClO4)2·6H2O as the Zn²⁺ source, where both HCOO^- and CO were produced, especially when excess zinc perchlorate was added into the system. FT-IR analysis of the ZnS−DMF(OAc) system revealed the presence of SH groups on the surface, explaining the gradual growth of the size with the addition of excess zinc acetate into the system. Extended X-ray absorption fine structure analysis revealed the correlation between the photocatalysis and the microscopic surface structure change of the ZnS nanocrystallites induced by the addition of Zn²⁺ to the nanocrystallite systems. The intimately interacting acetate ions to Zn atoms should prevent the formation of sulfur vacancies as catalytic sites of CO production, contributing to the enhanced photocatalytic activity for production of HCOO^- due to the formation of the DMF-coordinated nanocrystallites.

Adsorption of N,N-dimethylformamide (DMF) molecules on the surface of ZnS nanocrystallites was investigated by in situ Fourier transform IR and NMR spectroscopy in acetonitrile (AN)/methanol mixture solution. The C&dbd;O stretching vibration (νC&dbd;O) of DMF molecule shifted to a lower wavenumber when adsorbed on ZnS nanocrystallites. Their peak wavenumbers and intensities reflect the strength of interaction in DMF−ZnS surface bonding and a number of adsorbed DMF molecules. ¹H NMR measurements of this system also revealed strong interaction of DMF molecules with the surface of ZnS nanocrystallites. The surface interaction of DMF molecules was dependent on the coexistent counteranions in solution. DMF molecules coordinate more effectively to the surface of ZnS nanocrystallites prepared from Zn(ClO4)2·6H2O than that prepared from Zn(OAc)2·2H2O. These results agree well with the characteristics of interacting structure of DMF molecule observed by in situ extended X-ray absorption fine structure analysis reported previously (Langmuir 1996, 12, 3598).

In-situ Zn K-edge extended X-ray absorption fine structure (EXAFS) analysis of colloidal ZnS nanocrystallites (ZnS−DMF, mean diameter 3 nm, hexagonal) prepared by reacting zinc perchlorate (ZnS−DMF−ClO4), zinc sulfate (ZnS−DMF−SO4), or zinc acetate (ZnS−DMF−Ac), with H2S in N,N-dimethylformamide (DMF) was performed to clarify the microscopic surface structure of the nanocrystallites. EXAFS analysis reveals that the zinc atoms on the surface of ZnS nanocrystallites in DMF are solvated by the oxygen atoms of DMF molecules. The structural parameters, such as atomic distances and coordination numbers of the Zn−S and Zn−O shell, depend on the coexistent counteranions of the starting zinc salts. The coordination numbers for the Zn−S shell of ZnS−DMF−SO4 and −Ac are greater than that of ZnS−DMF−ClO4, indicating that ZnS−DMF−ClO4 has zinc atoms which are most efficiently solvated by DMF oxygens on the surface, while ZnS−DMF−SO4 and −Ac have a S-rich surface in DMF. The S-rich surface of ZnS−DMF−SO4 and −Ac well explains the spectral behavior, i.e., the red shift of the absorption onsets by the addition of Zn²⁺ ions to the respective ZnS−DMF solutions.

A mechanistic investigation on the photocatalytic reduction of CO2 with hexagonal CdS nanocrystallites prepared in N,N-dimethylformamide (DMF) was carried out from the standpoint of surface structures of the nanocrystallites. A remarkable increase of photocatalytic activity could be achieved by addition of excess Cd²⁺ to the system. Analysis of the emission behavior depending on the amount of excess Cd²⁺ in the system suggests that the Cd²⁺ addition results in the formation of sulfur vacancies on the surface of nanocrystallites due to the adsorption of excess Cd²⁺ to the surface. The formation of the sulfur vacancies on the surface was supported by in situ Cd K-edge EXAFS analysis of the nanocrystallites in solution as changes in the coordination numbers of cadmium−sulfur and cadmium−oxygen. Theoretical MO calculations using a density functional (DF) method supported the preferential bidentate-type absorption of CO2 with the Cd atom in the vicinity of the sulfur vacancy.

To investigate the pathogenesis of acute coronary disorders and to clarify what type of plaque precedes these disorders, percutaneous transluminal coronary angioscopy, by means of a new angioscope, was carried out during catheterisation in 100 consecutive patients anatomically suitable for such investigations. The quality of the angioscopic image was good enough for analysis in 84 patients (14 with acute myocardial infarction [within 8 h of onset], 16 with recent myocardial infarction [3 days-2 months since onset], 24 with old myocardial infarctions, 10 with unstable angina, and 20 with stable angina). Thrombi were observed in most patients with acute coronary disorders (all 14 with acute myocardial infarction, 9 of 10 with unstable angina). Occlusive thrombi were more common in patients with acute myocardial infarction than in those with unstable angina (11 [79%] vs 1 [10%]; p<0·001), whereas mural (non-occlusive) thrombi were more common in the unstable angina than in the acute myocardial infarction group (8 [80%] vs 3 [21%]; p<0·001). Xanthomatous ulcerated plaques or ragged irregular surfaces were seen in patients with acute coronary disorders and in those with recent myocardial infarction. Xanthomatous plaques were more common in patients with acute coronary disorders (50%) than in those with stable angina (15%) or old myocardial infarction (8%). By contrast white and smooth plaques were seen in cases of stable angina and old myocardial infarction. Angioscopy could display the intracoronary lumen more precisely than could coronary arteriography. This angioscopic study suggested that, although a thrombus overlying a rupture in the lining of the plaque was common in both unstable angina and acute myocardial infarction, the character of the thrombus may differ between these disorders, and lipid-rich xanthomatous plaque may precede rupture.

Aromatic compounds such as naphthalene and biphenyl are reduced by alkali metals, giving armatic anion radicals which are useful as strong bases in organic synthesis,1 as initiators of polymerization2 and oligomerization,3 and also as a medium for n-type doping in organic semiconductor like (CH)X.4 Howerver, preparation of such reagents requires anhydrous and oxygen free reaction conditions, use of carefully dried solvent being requisite for the success of the reaction. In addition, long inductin time is often observedwhen alkail metal cuts are used. Thus, employment of evaporated alkali metal film or finely dispersed metal alkali was generally recommended.5.

The transport of photogenerated electrons in nanoporous TiO2 electrodes is examined in a lithium perchlorate electrolyte solution by laser-induced photocurrent transient measurements. The diffusion coefficients of the photoelectrons are found to depend not only on electron density but also on the lithium ion concentration in the solution. The behavior of diffusion coefficients depending on lithium ion concentration is interpreted with an ambipolar diffusion mechanism. Diffusion coefficients at a high photoelectron density were observed to level off at a low lithium ion concentration, which is attributed to the effect of an ambipolar diffusion mechanism.

Thionicotinamide-capped gold nanoparticles undergo fusion as well as fragmentation upon laser pulse excitation (532 nm). The aggregation effect which is induced by thionicotinamide also disappears following laser pulse excitation. The morphological changes induced by thermal and photochemical effects were found to influence the optical properties of these particles.

IN the course of work on the effects of infection with several viruses upon different kinds of tissue cells from several animal species in vitro, it was found unexpectedly that Rift Valley fever virus has a marked destructive action upon rat sarcoma cells grown in tissue culture. A number of papers have appeared on the effects of infection with viruses upon various tumours in several animal species1. A destructive effect of the viruses of eastern equine encephalomyelitis and poliomyelitis on the tumour cells grown in tissue culture has been demonstrated by Bang and Gey2and by Scherer, Syverton and Gey3respectively; but no report of an effect of infection with Rift Valley fever virus upon tumour cells either in vivo or in vitro came to our attention. It is felt, therefore, that the results so far obtained by us are sufficiently interesting to merit publication at this stage.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The α‐bromo ketones (I) are converted to the corresponding α‐azido ketones (III) which undergo enol acylation to give the (acyloxy)vinyl azides (V).

The oxovanadium(IV) and cis‐dioxomolybdenum(VI) complexes (I) and (II) are obtained by reaction of the corresponding macrocycle with V(III) chloride in refluxing DMF or with tetracarbonylbis(piperidine)‐Mo(0) in refluxing DMF/cyclohexanol.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Regiochemistry and reactivities in the thermal ring‐cleavage reactions of the diarylcyclobutanes (I), (III), (V), (VIII), and (XI) are studied.