Keiko Miyabayashi

Platinum nanoparticles modified with alkylamine derivatives as an active and stable catalyst for oxygen reduction reaction.

Platinum nanoparticles (NPs) protected with octylamine (OA) as well as partially replaced by controlled ratios of alkylamine with pyrene group (PA) were successfully synthesized by a two-phase liquid reduction method of Pt(IV). The NPs without any pretreatment to remove the introduced organic-protected agents have been well-characterized and applied as supported catalysts on carbon black for oxygen reduction reaction (ORR). The modification of the Pt NP surface with OA and PA significantly improved the electrocatalytic activity such as area specific and mass specific activities, whose values increased by an increase in PA ratios. The potential cycle test demonstrates that the PA modification of Pt NPs enhances the stability of the catalyst and sustains high area and mass specific activities of ORR.

Synthesis and properties of orientational isomers of hybridized dihexylbithiopheneoctaethylporphyrin connected with 1,3-butadiyne linkages

Abstract A new type of hybridized dihexylbithiophene-octaethylporphyrin derivative (DHBTOEP) connected with the 1,3-butadiyne linkage was synthesized by oxidative cross-coupling of the corresponding terminal acetylenes. The absorption spectra and electrochemical properties of the DHBTOEP hybrid were examined, clearly proving that the orientation of two 3-hexylthiophene rings of DHBT plays an important role in electronic communication between the two terminal OEP rings.

Quantitative capability of electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry for a complex mixture

Electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been evaluated for the quantitation of complex mixtures, by using a crude oil (Taching vacuum residue) and polyethylene glycol (PEG600) as model analytes. The crude oil is an extremely complex mixture consisting of hundreds of organic compounds, which are mostly non-polar hydrocarbons. The crude oil ESI FT-ICR mass spectrum contained approximately five hundred distinguishable peaks accompanied by plenty of isobars. These ionic species were singly charged but not protonated. Although the crude oil response line was saturated at high concentration, the linearly responding range was extended by shortening the duration of the external accumulation which was carried out in the hexapole ion guide. No improvement in the linear response was observed for the exclusively trapped crude oil ions in a narrow m/z range which was trimmed by a correlated sweep ejection event. The crude oil mass distribution pattern shifted toward higher m/z as the analyte concentration became higher. A linear relationship was observed between the analyte concentrations and the average molecular weights, in both the crude oil and PEG600 experiments. The average molecular weights increased on extending the external accumulation time. This phenomenon was attributable to a novel space charge effect taking place for externally accumulated ions. Optimizing the external accumulation period was vital to get a linear response up to a reasonably high concentration region. Basically, complexity and plurality of mixture samples need not significantly affect quantitation by means of ESI FT-ICR MS.

Synthesis and electronic properties of diacetylene- and vinylene-groups connected octaethylporphyrin tetramer

Abstract The octaethylporphyrin (OEP) tetramer connected with both diacetylene and vinylene linkages was synthesized by an oxidative homo-coupling of the terminal acetylene of the vinylene-group connected OEP dimer. The electronic spectral and electrochemical studies were performed, proving that the hybridized OEP tetramer remains the characteristic properties of the vinylene-group connected OEP dimer more intensively as compared with the diacetylene-group connected OEP dimer.

Oligomerization of cadmium chalcogenide nanocrystals into CdTe-containing superlattice chains

Hierarchically-assembled binary cadmium chalcogenide (CdX, X = S, Se, Te) oligomers were engineered. CdTe precursor injections into a solution containing seeded nanocrystals provided longer oligomers possessing alternating and phase-separated CdX and CdTe constituents in the same wire, like an alternating copolymer.

Synthesis and electronic properties of trimeric octaethylporphyrin (OEP) derivative connected with diacetylene linkage. A comparative study with vinylene-group connected OEP trimer

Abstract A new trimeric octaethylporphyrin (OEP) derivative was synthesized, in which each porphyrin ring is connected with diacetylene linkage. Its electronic absorption spectrum was examined, proving that the diacetylene linkage induces splitting of Soret band of OEP into two main bands with clear maxima at 429 and 481 nm and more bathochromic shift of Q band to appear in such a longer wavelength region atλmax=670 nm in chloroform, in contrast with that of the corresponding vinylene-group connected OEP trimer. It was shown that the spectrum of the present diacetylene-group connected OEP derivative drastically changed in pyridine, suggesting a coordination of pyridine molecule as the fifth ligand onto Ni(II) metal of the central ring. Furthermore, Vilsmeier formylation, a typical electrophilic substitution on the aromatic compounds, was examined for further oligomerization of OEP, proving that it takes place at the central ring exclusively.

Synthesis and electronic properties of dinucleic octaethylporphyrin (OEP) derivatives spaced with p-phenylene group [OEP-(p-Phen)n-OEP].: A comparative study with dihexylbithiophene (DHBTh) group-spaced OEP dimers [OEP-(DHBTh)n-OEP]

Abstract The dinucleic octaethylporphyrin (OEP) derivatives described as OEP-(p-Phen)n-OEP (n = 1–4) were synthesized, in each of which the porphyrin ring is spaced with p-phenylene group. Their electronic properties were studied, as compared with those of the corresponding dihexylbithiophene (DHBTh) derivatives with head-to-head (HH) and tail-to-tail (TT) orientations. It proves that OEP-(p-Phen)n-OEP possesses an in-between feature of OEP-(HH-DHBTh)n-OEP and OEP-(TT-DHBTh)n-OEP in electronic properties.

Aromatic Ring Size Effect of a Surface Modification Agent on Platinum Nanoparticle Electrocatalysts for Oxygen Reduction Reaction

AbstractPlatinum nanoparticles (NPs) modified with alkylamines containing various aromatic rings (benzyl, naphtyl, anthryl, and pyrenyl) were synthesized as model cathode catalysts for fuel cells to investigate the role of aromatic surface modification agents on catalytic performance. Surface modification of Pt was confirmed by nuclear magnetic resonance spectra for NPs and thermogravimetric analysis for carbon-supported catalysts. Surface modification of Pt NPs with aromatic alkylamines improved the electrocatalytic activities for the oxygen reduction reaction, whose activity values increased by increasing the number of aromatic rings. The effect of surface modification on the electronic properties of the catalyst was evaluated by X-ray photoelectron spectroscopy. A large positive shift in the Pt 4f binding energy of surface-modified catalyst, especially for anthryl and pyrenyl modifications, was observed, indicating that one of the important factors is metal–support interaction facilitated by the aromatic groups through the π–π interactions with carbon support. Graphical Abstractᅟ

Evaluation of Alkylamine Modified Pt Nanoparticles as Oxygen Reduction Reaction Electrocatalyst for Fuel Cells via Electrochemical Impedance Spectroscopy

Organically (octyl amine, OA) surface modified electrocatalyst (OA-Pt/CB) was studied for its oxygen reduction reaction (ORR) activity via dc methods and its charge and mass transfer properties were studied via electrochemical impedance spectroscopy (EIS). Comparison with a commercial catalyst (TEC10V30E) with similar Pt content was also carried out. In EIS, both the catalysts showed a single time-constant with an emerging high-frequency semicircle of very small diameter which was fitted using suitable equivalent circuits. The organically modified catalyst showed lower charge-transfer resistance and hence, low polarization resistance in high potential region as compared to the commercial catalyst. The dominance of kinetic processes was observed at 0.925-1.000 V, whereas domination of diffusion based processes was observed at lower potential region for the organic catalyst. No effect due to the presence of carbon was observed in the EIS spectra. Using the hydrodynamic method, higher current penetration depth was obtained for the organically modified catalyst at 1600 rpm. Exchange current density and Tafel slopes for both the electrocatalysts were calculated from the polarization resistance obtained from EIS which was in correlation with the results obtained from dc methods.