Wataru Takashima

Quasi-solid dye sensitised solar cells filled with ionic liquid—increase in efficiencies by specific interaction between conductive polymers and gelators

Photo-energy conversions for quasi-solid dye sensitised solar cells increased when gel electrolytes were combined with conductive polymers as counter electrodes and the conversion surpassed that for DSSCs equipped with conventional Pt counter electrodes.

TFSI-doped polypyrrole actuator with 26% strain

A polypyrrole film, prepared electrochemically from a methyl benzoate solution of tetra-n-butylammonium bis(trifluoromethanesulfonyl)imide (TBATFSI), showed 26.5% strain and 6.7 MPa stress induced electrochemically in aqueous LiTFSI solution.

Alkyl Chain Length Dependence of Field-Effect Mobilities in Regioregular Poly(3-Alkylthiophene)Films

Carrier mobilities have been studied using the field effect in regioregular poly(3-alkylthiphene) (PAT, alkyl=butyl, hexyl, decyl, dodecyl and octadecyl) cast films at a field of around 104 V/cm. It was found that the carrier mobility of poly(3-butylthiophene) is 1.0×10-2 cm2/Vs, which is the largest one to date in the polythiophene family and three to four orders of magnitude larger than that of poly(3-octadecylthiophene). This result indicates that the substituted alkyl chain plays the role of a barrier to carrier migration between π-conjugated main chains, and primarily determines the mobility. The residual carrier densities are 1015 to 1016 cm-3 for all PATs and slightly lower for PATs with shorter alkyl chains. The field-effect mobilities are nearly the same as the values estimated by the time-of-flight method.

Langmuir–Blodgett films of poly(3-dodecyl thiophene) for application to glucose biosensor

Abstract Monolayers of poly(3-dodecyl thiophene) (P3DT) have been obtained on indium–tin-oxide (ITO) coated glass plates by dispensing mixed solution of P3DT and stearic acid (SA) prepared in chloroform onto water subphase by a microsyringe. The pressure–area isotherms of these P3DT–SA monolayers were studied as a function of temperature and pH. The monolayer stability onto the water subphase has been experimentally studied at different temperatures, pH and surface pressure. These P3DT–SA monolayers fabricated onto the ITO-coated glass plates were characterized using FTIR and cyclic voltammetry studies. The desired enzyme monolayers were fabricated by dispensing glucose oxidase mixed with P3DT/SA in chloroform and were transferred onto desired ITO-coated glass. An attempt has been made to utilize these P3DT/SA/GOX LB films for fabrication of a glucose biosensor.

Electrolyte and strain dependences of chemomechanical deformation of polyaniline film

Abstract Chemomechanical deformation of polyaniline has been studied in a variety of aqueous acids such as HCl, HI, HBF 4 , HClO 4 , H 2 SO 4 and Benzenesulfonic acid and also as the function of strain. The samples prepared from cast film and also gel form from NMP solution are tested. The elongation ratios, i.e., the increment of elongation divided by the original length, is about 3~5% depending slightly on the acids, viz., size of anions. The lifting power of load is 2~3MPa along the stretched direction.

The electrochemical actuator using electrochemically-deposited poly-aniline film

Abstract Electrochemomechanical polymer actuators were fabricated by using the electro-deposited poly -aniline film. Using LASER displacement meter, we can easily get the in-situ observation of the displacement and the cyclic voltammogram[1]. At the redox reaction from leuco-emeraldine salt to emeraldine salt(ES), PANI film showed large deformation. On the other hand, at the redox reaction from ES to pernigraniline salt, PANI film showed the slight contraction.

Regioregularity vs Regiorandomness: Effect on Photocarrier Transport in Poly(3-hexylthiophene)

The time-of-flight technique has been used to study transports of photocarriers in regioregular and regiorandom poly(3-hexylthiophene) (P3HT) films by fabricating indium-tin-oxide/P3HT/Al sandwich cell. It has been found that regularity in the coupling of monomers, head-to-tail (HT) has a marked effect on electrical properties and photocarrier transport in P3HT. Both regular and random P3HT films exhibit a dispersive photocurrent response with the positive sign of photocarrier (hole). The room temperature hole mobility of regioregular P3HT is estimated to be 1.21 ×10-3 cm2/Vs and is one order of magnitude larger than that of the random one. The mobility in regioregular P3HT is almost independent of the applied field while that of random P3HT shows a positive field dependence at the field larger than 1.0 ×105 V/cm.

Direct Measurement and Mechanism of Electro-Chemomechanical Expansion and Contraction in Polypyrrole Films

Electro-chemomechanical expansion and contraction in polypyrrole films synthesized electrochemically from pyrrole in electrolytes of p-phenolsulfonic (PPS) acid has been measured directly in various supporting electrolytes. It is found that the films maintain a high electro-chemomechanical activity and conductivity in the wide pH range from pH4 to pH10 and also at the reduced and oxidized states studied under the present conditions. The electro-chemomechanical expansion of polypyrrole films is primarily driven by the insertion of bulky ions, regardless of oxidation and reduction. This is different from the mechanism of polyaniline films, in which a conformation change of the polymer structure is involved. The mechanism of electro-chemomechanical deformation in polypyrrole film is discussed, taking the conductivity and conformation of polypyrrole into consideration.

Polymer field-effect transistors by a drawing method

We demonstrated the polymer field-effect transistors (FETs) utilizing regioregular poly(3-alkylthiophene)s (P3AT) films prepared by a drawing method. The P3AT film exhibited large optical dichroic ratio, which originated in the polymer backbones aligned to the drawing direction. In-plane anisotropy and enhancement of FET characteristics have been observed that are caused by molecular alignment. In the case of poly(3-dodecylthiophene), the hole mobility along the drawing direction was enhanced by a factor of 25 compared with that of spin-coated film.

Electrochemomechanical deformation of polyaniline films

The deformation of unstretched and stretched polyaniline (PANI) films by the electrochemical cycle has been studied. An anisotropic deformation is observed. The largest expansion and contraction upon oxidation and reduction, respectively, are observed for the direction perpendicular to the draw axis. The deformation parallel to the draw axis is the smallest for oxidation leucoemeraldine salt to emeraldine salt (ES), and shows even slight contraction upon oxidation from ES to pernigraniline salt. The expansion ratio Δl/ l0, where Δl is the increment of expansion and l0 is the original length, is found to be proportional to the degree of oxidation. In the unstretched film, Δl/ l0 is about -2% at 20% reduction from the ES state. The results are discussed in terms of intercalation of dopant ions per repeating unit between chains and the conformational change of chains.