HYDROGEN-BONDING INTERACTION IN DBI POLYMERIZATION

We have reported that intramolecular chain-transfer reaction takes place in radical polymerization of itaconates at high temperatures and/or at low monomer concentrations. In this paper, radical polymerizations of di-n-butyl itaconate (DBI) were carried out in toluene at 60°C in the presence of amide compounds. The 13C NMR spectra of the obtained poly(DBI)s indicated that the intramolecular chain-transfer reaction was suppressed as compared with in the absence of amide compounds. The NMR analysis of DBI and N-ethylacetamide demonstrated both 1:1 complex and 1:2 complex were formed at 60°C through a hydrogen-bonding interaction. The ESR analysis of radical polymerization of diisopropyl itconate (DiPI) was conducted in addition to the NMR analysis of the obtained poly(DiPI). It was suggested that the suppression of the intramolecular chain-transfer reaction with the hydrogen-bonding interaction was achieved by controlling the conformation of the side chain at the penultimate monomeric unit of the propagating radical with an isotactic stereosequence

Voltammetric Study of Viologens Possessing Aromatic Groups on a HOPG Electrode Surface

ナノダイナミクス国際シンポジウム 平成22年1月21日(木) 於長崎大学Nagasaki Symposium on Nano-Dynamics 2010 (NSND2010), January 21, 2010, Nagasaki University, Nagasaki, Japan, Invited Lectur

Simultaneous Improvements in Performance and Durability of an Octahedral PtNix/C Electrocatalyst for Next-Generation Fuel Cells by Continuous, Compressive, and Concave Pt Skin Layers

Simultaneous improvements in oxygen reduction reaction (ORR) activity and long-term durability of Pt-based cathode catalysts are indispensable for the development of next-generation polymer electrolyte fuel cells but are still a major dilemma. We present a robust octahedral core–shell PtNix/C electrocatalyst with high ORR performance (mass activity and surface specific activity 6.8–16.9 and 20.3–24.0 times larger than those of Pt/C, respectively) and durability (negligible loss after 10000 accelerated durability test (ADT) cycles). The key factors of the robust octahedral nanostructure (core–shell Pt73Ni27/C) responsible for the remarkable activity and durability were found to be three continuous Pt skin layers with 2.0–3.6% compressive strain, concave facet arrangements (concave defects and high coordination), a symmetric Pt/Ni distribution, and a Pt67Ni33 intermetallic core, as found by STEM-EDS, in situ XAFS, XPS, etc. The robust core–shell Pt73Ni27/C was produced by the partial release of the stress, Pt/Ni rearrangement, and dimension reduction of an as-synthesized octahedral Pt50Ni50/C with 3.6–6.7% compressive Pt skin layers by Ni leaching during the activation process. The present results on the tailored synthesis of the PtNix structure and composition and the better control of the robust catalytic architecture renew the current knowledge and viewpoint for instability of octahedral PtNix/C samples to provide a new insight into the development of next-generation PEFC cathode catalysts

La5Ti2Cu1-xAgxS5O7 photocathodes operating at positive potentials during photoelectrochemical hydrogen evolution under irradiation of up to 710 nm

A photoelectrochemical (PEC) cell based on a series-connected photocathode and photoanode made of particulate semiconductors is a potentially scalable and inexpensive device for renewable solar hydrogen production via PEC water splitting without any external power supply. The realisation of such PEC devices hinges on the development of photoelectrodes that operate at a small applied voltage. In this study, solid solutions of La5Ti2CuS5O7 (LTC) and La5Ti2AgS5O7 (LTA) were synthesised, and their physical, optical, and PEC properties in the water splitting reaction were discussed. LTC and LTA formed a La5Ti2Cu1-xAgxS5O7 solid solution (LTC(1-x)A(x)) over the whole compositional range. The indirect bandgap energy of LTC(1-x)A(x) changed nonlinearly with respect to composition, attaining its minimum value (ca. 1.8 eV) at a composition of x approximate to 0.16. Photoelectrodes of Al-doped LTC(1-x)A(x) solid solution powder fabricated using the particle transfer method exhibited a photocathodic response regardless of the Ag content. 1% Al-LTC(0.9)A(0.1) photocathodes exhibited the best PEC properties in the hydrogen evolution reaction and yielded a hypothetical half-cell solar-to-hydrogen energy conversion efficiency of 0.25% at +0.6 V vs. RHE, three times higher than the previously reported 1% Sc-LTC. In addition, 1% Al-LTC(0.9)A(0.1) photocathodes were fairly stable at + 0.7 V vs. RHE without any protective modifications. Owing to the positive operational electrode potential of 1% Al-LTC(0.9)A(0.1), unassisted PEC water splitting was accomplished using series-connected photoelectrodes made of 1% Al-LTC(0.9)A(0.1) and BaTaO2N, particulate semiconductors with absorption edge wavelengths of 710 and 660 nm, respectively, at a Faradaic efficiency of unity and a solar-to-hydrogen energy conversion efficiency of approximately 0.1%.ArticleEnergy & Environmental Science.8(11):3354-3362(2015)journal articl

Sensitization of TRPV1 by EP(1 )and IP reveals peripheral nociceptive mechanism of prostaglandins

Prostaglandin E(2 )(PGE(2)) and prostaglandin I(2 )(PGI(2)) are major inflammatory mediators that play important roles in pain sensation and hyperalgesia. The role of their receptors (EP and IP, respectively) in inflammation has been well documented, although the EP receptor subtypes involved in this process and the underlying cellular mechanisms remain to be elucidated. The capsaicin receptor TRPV1 is a nonselective cation channel expressed in sensory neurons and activated by various noxious stimuli. TRPV1 has been reported to be critical for inflammatory pain mediated through PKA- and PKC-dependent pathways. PGE(2 )or PGI(2)increased or sensitized TRPV1 responses through EP(1 )or IP receptors, respectively predominantly in a PKC-dependent manner in both HEK293 cells expressing TRPV1 and mouse DRG neurons. In the presence of PGE(2 )or PGI(2), the temperature threshold for TRPV1 activation was reduced below 35°C, so that temperatures near body temperature are sufficient to activate TRPV1. A PKA-dependent pathway was also involved in the potentiation of TRPV1 through EP(4 )and IP receptors upon exposure to PGE(2 )and PGI(2), respectively. Both PGE(2)-induced thermal hyperalgesia and inflammatory nociceptive responses were diminished in TRPV1-deficient mice and EP(1)-deficient mice. IP receptor involvement was also demonstrated using TRPV1-deficient mice and IP-deficient mice. Thus, the potentiation or sensitization of TRPV1 activity through EP(1 )or IP activation might be one important mechanism underlying the peripheral nociceptive actions of PGE(2 )or PGI(2)

Key Structural Transformations and Kinetics of Pt Nanoparticles in PEFC Pt/C Electrocatalysts by a Simultaneous Operando Time-Resolved QXAFS–XRD Technique

This account article treats with the key structural transformations and kinetics of Pt nanoparticles in Pt/C cathode catalysts under transient voltage operations (0.4 VRHE→1.4 VRHE→0.4 VRHE) by simultaneous operando time-resolved QXAFS–XRD measurements, summarizing and analyzing our previous kinetic data in more detail and discussing on the key reaction steps and rate constants for the performance and durability of polymer electrolyte fuel cells (PEFC). The time-resolved QXAFS–XRD measurements were conducted at each acquisition time of 20 ms, while measuring the current/charge of the PEFC. The rate constants for the transient responses of Pt valence, CN(Pt–O) (CN: coordination number), CN(Pt–Pt), and Pt metallic-phase core size under the transient voltage operations were determined by the combined time-resolved QXAFS‒XRD technique. The relationship of the structural kinetics with the performance and durability of the PEFC Pt/C was also documented as key issues for the development of next-generation PEFCs. The present account emphasizes the time-resolved QXAFS and XRD techniques to be a powerful technique to analyze directly the structural and electronic change of metal nanoparticles inside PEFC under the operating conditions

Observation of Degradation of Pt and Carbon Support in Polymer Electrolyte Fuel Cell Using Combined Nano-X-ray Absorption Fine Structure and Transmission Electron Microscopy Techniques

It is hard to directly visualize spectroscopic and atomic–nanoscopic information on the degraded Pt/C cathode layer inside polymer electrolyte fuel cell (PEFC). However, it is mandatory to understand the preferential area, sequence, and relationship of the degradations of Pt nanoparticles and carbon support in the Pt/C cathode layer by directly observing the Pt/C cathode catalyst for the development of next-generation PEFC cathode catalysts. Here, the spectroscopic, chemical, and morphological visualization of the degradation of Pt/C cathode electrocatalysts in PEFC was performed successfully by a same-view combination technique of nano-X-ray absorption fine structure (XAFS) and transmission electron microscopy (TEM)/scanning TEM–energy-dispersive spectrometry (EDS) under a humid N2 atmosphere. The same-view nano-XAFS and TEM/STEM–EDS imaging of the Pt/C cathode of PEFC after triangular-wave 1.0–1.5 VRHE (startup/shutdown) accelerated durability test (tri-ADT) cycles elucidated the site-selective area, sequence, and relationship of the degradations of Pt nanoparticles and carbon support in the Pt/C cathode layer. The 10 tri-ADT cycles caused a carbon corrosion to reduce the carbon size preferentially in the boundary regions of the cathode layer with both electrolyte and holes/cracks, accompanied with detachment of Pt nanoparticles from the degraded carbon. After the decrease in the carbon size to less than 8 nm by the 20 tri-ADT cycles, Pt nanoparticles around the extremely corroded carbon areas were found to transform and dissolve into oxidized Pt2+–O4 species