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Thermoelectric properties of regioregular poly(3-hexylthiophene) (P3HT) were investigated in correlation with doping level measured by a potential-step chronocoulometry (PSC) method. It was found that the log–log plot of Seebeck coefficients against doping levels showed a good linearity, whose slope value was around −1. [ABSTRACT FROM AUTHOR]

D-π-Cat fluorescent dyes YM-1 and YM-2 with a diphenylamine moiety as the electron-donating group, a catechol (Cat) unit as the anchoring group and fluorene or carbazole as the p-conjugated system were designed and developed as a photosensitizer for type-II dye-sensitized solar cells (DSSCs), which have a direct electron-injection pathway from the dye to the conduction band (CB) of the TiO[sub 2] electrode by photoexcitation of the dye-to-TiO[sub 2] charge transfer (DTCT) bands. Furthermore, not only to gain insight into the influence of the molecular structure of D-π-Cat dyes on the appearance of a DTCT band and the electron-injection mechanism, but also to investigate the impacts of the DTCT characteristics of D-p-Cat dyes on the photovoltaic performances of DSSCs, a D-π-Cat fluorescent dye YM-3 with carbazole-terthiophene as the p-conjugated system was also synthesized. It was found that the D-π-Cat dyes possess a good light-harvesting efficiency (LHE) in the visible region due to a broad absorption band corresponding to DTCT upon binding to a TiO[sub 2] film. The incident photon-to-current conversion efficiency (IPCE) corresponding to the DTCT band for DSSCs based on YM-1 and YM-2 is higher than that for YM-3. This work indicates that the stabilization of the LUMO level and the expansion of the p-conjugated system by the introduction of a long p-bridge such as terthiophene on the Cat moiety can lead to an increase in the intramolecular charge transfer (ICT) excitation based on p/p* transition with a decrease in the DTCT characteristics, resulting in enhancement of an indirect electron-injection pathway from the excited dye to the CB of TiO[sub 2] by photoexcitation of the local band of the adsorbed dye on TiO[sub 2]. [ABSTRACT FROM AUTHOR]

A D–π–A dye SAT-1 with benzo[4,5]thieno[2,3-c]pyridine as the electron-withdrawing anchoring group capable of forming a hydrogen bond at Brønsted acid sites or a coordinate bond at Lewis acid sites on a TiO2 surface has been developed as a new-type of D–π–A dye sensitizer for dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

As a new class of D–π–A dye sensitizer for dye-sensitized solar cells (DSSCs), we have designed and synthesized the functionally separated D–π–A fluorescent dye YJY-1 with an aldehyde as an electron-accepting group and a carboxyl group as an anchoring group. Furthermore, not only to evaluate the usefulness of D–π–A dye sensitizers functionally separated into an electron acceptor moiety and an anchoring group, but also to gain insight into the influences of interaction between the aldehyde of the dyes and the TiO2 surface on the photovoltaic performances of DSSCs, the D–π–A fluorescent dye YJY-2 with an aldehyde as an electron-accepting group, but without a carboxyl group, was also synthesized. It was found that the functionally separated D–π–A dye YJY-1 exhibits not only high adsorption ability onto TiO2 film through the carboxyl group, but also efficient electron injection from the dye into the CB of TiO2 through the aldehyde which is located close to the TiO2 surface. This work demonstrates that the functionally separated D–π–A dyes would be expected to be one of the most promising classes of organic dye sensitizers for DSSCs. [ABSTRACT FROM AUTHOR]

D–π–A type boron dipyrromethene (BODIPY) dye YH-1, which has two pyridyl groups as electron-withdrawing-anchoring groups at the end of the 3- and 5-positions and a carbazole-diphenylamine moiety as an electron donor at the 8-position on the BODIPY core, was designed and developed as a photosensitizer for dye-sensitized solar cells (DSSCs). It was found that the dye YH-1 possesses a good light-harvesting efficiency (LHE) in the red/near-IR (NIR) region and good adsorption ability on TiO2 film. We demonstrate that the expansion of the π-conjugated system by the introduction of not only the carbazole-diphenylamine moiety and the thiophene unit at the 8-position but also two thienylpyridines at the 3- and 5-positions on the BODIPY core can lead to red-shift and broadening of the absorption band in the red/NIR region. DSSCs based on YH-1 exhibit incident photon-to-current conversion efficiency of ca. 10% over a range of 500 to 700 nm, with an onset at 800 nm. [ABSTRACT FROM AUTHOR]

Donor–π–acceptor type pyridinium dyes that have been newly synthesized showed bathochromic shift of the absorption band with decreasing dielectric constant (r) of solvent (negative solvatochromism), and the bathochromic shifts in halogenated solvents were larger than those in non-halogenated solvents of similar rvalues. The influences of halogenated solvents on the large bathochromic shifts are studied on the basis of 1H NMR measurements, semi-empirical molecular calculations (AM1 and INDO/S using the SCRF Onsager model), and absorption spectral measurements of the dyes adsorbed on nanocrystalline TiO2film immersed in solvents. [ABSTRACT FROM AUTHOR]

D–π–A fluorescent dye YNI-2 with two pyridyl groups as an electron-withdrawing–injecting anchoring group possessing a high coordinate bonding ability to Lewis acid sites on the TiO2 surface, which can lead to high dye loading on the TiO2 film and efficient electron injection, has been developed as a new type of D–π–A dye sensitizer for dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

Anthracene–boronic acid ester as a new class of fluorescence PET sensors for detection of a trace amount of water in organic solvents has been designed and developed. [ABSTRACT FROM AUTHOR]

D-π-A dyes NI-4 bearing a pyridyl group, YNI-1 bearing two pyridyl groups and YNI-2 bearing two thienylpyridyl groups as the anchoring group on the TiO 2 surface have been developed as dye sensitizers for dye-sensitized solar cells (DSSCs), where NI-4 and YNI-2 can adsorb onto the TiO 2 electrode through the formation of the coordinate bond between the pyridyl group of the dye and the Lewis acid site (exposed Ti n+ cations) on the TiO 2 surface, but YNI-1 is predominantly adsorbed on the TiO 2 electrode through the formation of the hydrogen bond between the pyridyl group of the dye and the Brønsted acid sites (surface-bound hydroxyl groups, Ti-OH) on the TiO 2 surface. The difference in the dye-adsorption mode among the three dyes on the TiO 2 surface has been investigated from the adsorption equilibrium constant (K ad ) based on the Langmuir adsorption isotherms. It was found that the K ad values of YNI-1 and YNI-2 are higher than that of NI-4, and more interestingly, the K ad value of YNI-2 is higher than that of YNI-1. This work demonstrates that that for the D-π-A dye sensitizers with the pyridyl group as the anchoring group to the TiO 2 surface the number of pyridyl groups and the dye-adsorption mode on the TiO 2 electrode as well as the molecular structure of the dye sensitizer affect the K ad value for the adsorption of the dye to the TiO 2 electrode, that is, resulting in a difference in the K ad value among the D-π-A dye sensitizers NI-4, YNI-1 and YNI-2.

Nearest-neighbor intermolecular distances of molecules adsorbed on the surface of nanocrystalline TiO(2) particles were evaluated by the electron spin resonance (ESR) technique with molecules having a nitroxide radical and a carboxyl group as a spin probe to clarify their aggregation behaviors on TiO(2) and the influence of coadsorbates.

A new class of fluorescence sensor for detection of water in organic solvents based on photo-induced electron transfer (PET) of anthracene coupled with an amino acid has been designed and developed.

Heteropolycyclic donor--acceptor (D--A) structural isomers of benzofuro[2,3-c]oxazolo[4,5-a]carbazole-type (2a-f) and benzofuro[2,3-c]oxazolo[5,4-a]carbazole-type fluorescent dyes (3a-f), which differ in the position of oxygen and nitrogen atoms of the oxazole ring, have been synthesized, and their photophysical and electrochemical properties have been investigated. The fluorescent dyes 2a-f exhibit much stronger intramolecular charge transfer (ICT) absorption and fluorescence bands than 3a-f. Both of the D-pi-A structural isomers showed bathochromic shifts of the fluorescence band and a decrease in the fluorescence quantum yields with increasing solvent polarity (i.e., positive fluorescence solvatochromism), and the bathochromic shifts for 3a-f were larger than those for 2a-f. The fluorescent dyes 2a-c and 3a-c, which have cyano and carboxyl groups, and carboxylic acid ester as electron-withdrawing substituents, exhibited significant fluorescence solvatochromic properties, compared to 2e, 2f, 3e and 3f without an electron-withdrawing substituent. The fluorescence solvatochromism of the fluorescent dyes were analyzed with the Lippert-Mataga correlation. Moreover, to elucidate the differences of photophysical properties among the fluorescent dyes, we have performed time-resolved fluorescence spectroscopic measurements, and a change of the electronic or molecular structures between the ground and excited states was evaluated by a comparison of the experimental radiative rate constant (k(r)) with the Strickler-Berg rate constant (kSB(r)). The electrochemical properties of 2a-f and 3a-f were determined by cyclic voltammetry, which demonstrated that these fluorescent dyes have similar HOMO energy levels, but different LUMO energy levels. Semi-empirical molecular orbital calculations (AM1 and INDO/S) have been carried out to elucidate the effects of the substituents and chromophore skeleton on photophysical properties of the two D-pi-A structural isomers. These studies indicated that the ICT characteristics in the excited state are different among the fluorescent dyes, which is a principal reason for the differences of the fluorescence solvatochromism and the substituent dependent fluorescence properties among the two D-pi-A structural isomers.

A simple and safe technique which is based on glow discharge is demonstrated for stable encapsulation of H atoms in cage-shaped silsesquioxanes at room temperature, leading to the encapsulation yield of ca. 10(-4) H atoms per molecule for 10-minute discharging, much faster than the conventional gamma-ray irradiation technique.

Donor-acceptor pi-conjugated benzofuro[2,3-c]oxazolo[4,5-a]carbazole-type fluorescent dyes 3a, 3b, 8a, and 8b with a carboxyl group at different positions of the chromophore skeleton have been designed and synthesized. The absorption and fluorescence spectra and cyclic voltammograms of the fluorescent dyes agree very well, showing that the position of the carboxyl group has a negligible influence on the photophysical and electrochemical properties of these dyes. When these dyes are used in dye-sensitized solar cells, however, their photovolatic performances are considerably different. The short-circuit photocurrents and energy conversion efficiencies under a simulated solar light increase in the order: 3a (2.12 mA cm(-2), 1.00%) approximately 3b (2.10 mA cm(-2), 1.06%) > 8b (1.50 mA cm(-2), 0.67%) > 8a (0.84 mA cm(-2), 0.34%). Based on semi-empirical molecular orbital calculations (AM1 and INDO/S) together with spectral analyses and their photovolatic performance, the relationships between the observed photovolatic properties and the chemical structures of the benzofuro[2,3-c]oxazolo[4,5-a]carbazole-type fluorescent dyes are discussed. It is found that strong interaction between a TiO(2) surface and the electron accepting moiety of the dye leads to a high photovoltaic performance.