Tomonobu Mizumo

Photovoltaic performance of dye-sensitized solar cells based on D–π–A type BODIPY dye with two pyridyl groups

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.

Preparation of cage-like octa(3-aminopropyl)silsesquioxane trifluoromethanesulfonate in higher yield with a shorter reaction time

Cage-like octa(3-aminopropyl)silsesquioxane trifluoromethanesulfonate (OAP-POSS-CF3SO3) was prepared in higher yield (ca. 93%) with a shorter reaction time (ca. 5–6 h), when the hydrolytic condensation of 3-aminopropyltrimethoxysilane was performed using the superacid trifluoromethanesulfonic acid as a catalyst. The structure of the resulting OAP-POSS-CF3SO3 was confirmed mainly by 29Si NMR, MALDI-TOF MS, ESI MS, and IR measurements. It is suggested that the lower pKa of the acid catalyst is an important factor leading to the improved yield for the preparation of OAP-POSS-CF3SO3.

Lithium ion conduction in an organoborate zwitterion–LiTFSI mixture

An organoborate zwitterion-lithium salt mixture, prepared via selective borate formation of N-ethylimidazolium salt, exhibited ionic conductivity of 3.0 x 10(-5) S cm(-1) at 50 degrees C and a lithium transference number of 0.69.

Depolymerization and ionic conductivity of enzymatically deproteinized natural rubber having epoxy group

Abstract Preparation of liquid epoxidized natural rubber (ENR) was made by oxidative depolymerization of ENR in latex stage without loss of epoxy group. Epoxidation of fresh natural rubber latex, which was purified by deproteinization with proteolytic enzyme and surfactant, was carried out with freshly prepared peracetic acid. The glass transition temperature ( T g ) and gel content of the rubbers increased after the epoxidation, both of which were dependent upon an amount of peracetic acid. The gel content was significantly reduced by oxidative depolymerization of the rubber with (NH 4 ) 2 S 2 O 8 in the presence of propanal. The resulting liquid epoxidized rubber ( M n ≈10 4 ) was found to have well-defined terminal groups, i.e. aldehyde groups and α-β unsaturated carbonyl groups. The novel rubber was applied to transport Li + as an ionic conducting medium, that is, solid polymer electrolyte.

Synthesis of diphenylamino-carbazole substituted BODIPY dyes and their photovoltaic performance in dye-sensitized solar cells

Non-alkylated BODIPY dye YHO-1 and hexa-alkylated BODIPY dye YHO-2, which have a diphenylamino-carbazole moiety as an electron-donating group at the 8-position on the BODIPY core and a carboxyhexyl group as an anchoring group on the carbazole ring, were designed and developed as photosensitizers for dye-sensitized solar cells (DSSCs). From the molecular structures of YHO-1 and YHO-2, when the two dyes were adsorbed on the TiO2 surface, it is assumed that the BODIPY core is located in close proximity to the TiO2 surface. The dye YHO-2 (Φf = 0.62) exhibits a significantly higher fluorescence quantum yield (Φf) than YHO-1 (Φf = 0.06). The short-circuit photocurrent density (Jsc) and solar energy-to-electricity conversion yield (η) for a DSSC based on YHO-2 are greater than those of YHO-1. This work demonstrates that fluorescent BODIPY dyes can inject electrons efficiently from the BODIPY core to the conduction band (CB) of the TiO2 electrode, but non-fluorescent BODIPY dyes result in lowering of photocurrent generation due to radiationless relaxation of the photoexcited dye.

Facile preparation of a soluble polymer containing polyhedral oligomeric silsesquioxane units in its main chain

A soluble polymer containing polyhedral oligomeric silsesquioxane (POSS) units in its main chain was successfully prepared in one-step by hydrolytic condensation of a mixture of two types of amino group-containing organotrialkoxysilanes using the aqueous trifluoromethanesulfonic acid (CF3SO3H) as a catalyst. In this CF3SO3H-catalysed synthesis, 3-(2-aminoethylamino)propyltrimethoxysilane and bis[3-(trimethoxysilyl)propyl]amine acted as a starting material of POSS and a cross-linker, respectively. The 29Si NMR spectrum of the resulting POSS polymer only showed signals in the T3 region. The IR spectrum of the hydrophobised POSS polymer indicated a single absorption peak at 1119 cm−1, attributed to the Si–O–Si stretching absorption band, but no absorption peak at ca. 3500 cm−1 for silanol groups. In addition, its weight-average molecular weight was 3.24 × 104. Overall, these results suggested the formation of a polymer composed of POSS units. The POSS polymer provided optically transparent films. This may result from the coexistence of POSS components bearing two different randomly distributed side-chain groups in the polymer, which suppresses crystallization. The POSS polymer exhibited 5% and 10% weight losses at 351 °C and 368 °C, respectively, indicative of its relatively high thermal stability.

Preparation of a sulfo-group-containing rod-like polysilsesquioxane with a hexagonally stacked structure and its proton conductivity.

A sulfo-group-containing rod-like polysilsesquioxane with a hexagonally stacked structure (PSQ-SO3H) was successfully prepared by oxidation and hydrolytic polycondensation of 3-mercaptopropyltrimethoxysilane (MPTMS) in a mixed aqueous solution of NaOH and H2O2. The X-ray diffraction pattern of the PSQ-SO3H film exhibited three diffraction peaks with a d-value ratio of 1:1/√3:1/2, indicating the formation of a hexagonally stacked structure. In addition, the transmission electron microscopy image of PSQ-SO3H exhibited a striped pattern, indicating that the rod-like PSQs were stacked in a parallel fashion. The presence of ionic side-chains composed of the sulfonate anions and sodium cations during the hydrolytic polycondensation of MPTMS was found to be essential for the formation of this regularly structured PSQ. Finally, the proton conductivity of the PSQ-SO3H film, determined by using complex impedance spectroscopy, was relatively high (>10(-2)u2005Su2009cm(-1)) at 80u2009°C and 30-90u2009% relative humidity.

Preparation of low-crystalline POSS containing two types of alkylammonium groups and its optically transparent film

In this study, a low-crystalline POSS containing two types of alkylammonium groups was successfully prepared by hydrolytic condensation of a mixture of two types of amino group-containing organotrialkoxysilanes, i.e. 3-(2-aminoethylamino)propyltrimethoxysilane and 3-aminopropyltrimethoxysilane, using aqueous trifluoromethanesulfonic acid as the catalyst and solvent. Due to the low molecular symmetry of the resulting POSS compound containing two different randomly distributed side-chain groups, its crystallization was suppressed, leading to the formation of an optically transparent film.

Preparation of imidazolium-type ionic liquids containing silsesquioxane frameworks and their thermal and ion-conductive properties

An ionic liquid containing a random-structured oligosilsesquioxane (Im-Random-SQ-IL) was successfully prepared by the hydrolytic condensation of 1-methyl-3-[3-(triethoxysilyl)propyl]imidazolium chloride (MTICl) in aqueous bis(trifluoromethanesulfonyl)imide (TFSI). Im-Random-SQ-IL exhibited a glass transition temperature (Tg) at −25 °C as indicated by an endothermic peak in the differential scanning calorimetry (DSC) curve. In addition, fluidity was visually observed at ca. 0 °C, i.e. Im-Random-SQ-IL is a room temperature ionic liquid. Conversely, when the hydrolytic condensation of MTICl was performed using a water/methanol (1:19 v/v) solution of TFSI, an ionic liquid containing a cage-like oligosilsesquioxane (Im-Cage-SQ-IL) was obtained. The Tg of Im-Cage-SQ-IL was −22 °C, and its melting temperature (Tm) was 105 °C according to the DSC analysis. In addition, fluidity was observed for this ionic liquid at ca. 100 °C. These results suggest that both the amorphous structure of Im-Random-SQ-IL and the type of substituent groups in the silsesquioxane contributed to the ionic liquid behaviour below room temperature. In addition, these ionic liquids exhibited high thermal stabilities (Im-Random-SQ-IL: Td3 = 429 °C, Td5 = 437 °C and Td10 = 447 °C, Im-Cage-SQ-IL: Td3 = 427 °C, Td5 = 436 °C and Td10 = 446 °C) and relatively high ion conductivities (10−4–10−3 S cm−1, at ∼100 °C).

Ionic conductivity of PPO‐sulfonamide salt hybrids and their network polymers

New type of polymer electrolytes containing poly(propylene oxide) (PPO)/sulfonamide (SA) lithium salt (-NLi-SO2-) unit were synthesized and the electrochemical properties were analyzed. The mono- or di-charged hybrids became amorphous salt and showed low glass transition temperature, but the bulk ionic conductivity was lower than 10−6 S/cm at room temperature. The introduction of terminal group having strong electron-withdrawing effect on the SA end improved the ionic conductivity. The maximum ionic conductivity was observed (1.7u2005×u200510−5 S/cm at 30u2009°C) when the terminal group of PPO500-SA Li salt hybrid was trifluorometyl (-CF3) group. On the other hand, two types of hybrid-networks were also synthesized. They were rubbery solids with amorphous phase. The ionic conductivity was less than 10−8 S/cm because of the relatively higher Tg. The ionic conductivity of the network was improved more than 1000 times by the addition of PPO500-SALi-CF3. The Blend of the network and oligomer gave homogeneously mixed dry polymer electrolyte without phase separation. The electrochemical characteristics was analyzed with Li ∥ PPO electrolyte ∥ Li cell under dc electric field. Copyright