Conformation-dependent dynamics of macromolecular ions in the gas phase under an electrostatic field: A molecular dynamics simulation

Highly charged macromolecular ions exhibit various conformations in gas. Intramolecular charge-to-charge interaction induces a transformation from a globular structure into a stretched one. The change in the molecular conformation brings a complex dynamic behavior of ions under an electrostatic field. In the present study, we visualized the movement of a monovalent and multiply charged straight chain macromolecules, polyethylene glycol (PEG), by a molecular dynamics (MD) simulation. The simulation showed that a singly charged PEG ion (899?<?M_W < 4,643) takes a globular conformation. The electrical mobilities of these ions determined from the migration distance under an electric field were compared with the experimental data and those determined by the classical Mason–Schamp theory under an assumption of spherical shape. As a result, we obtained a good agreement between the MD, theoretical, and experimental data for the monovalent ions. We also found that the MD simulation successfully predicts the electrical mobility of the multiply charged stretched PEG ions, but the classical theory fails. We were able to visualize the periodic bending and stretching motion by the MD simulation. This unique motion results from the localization of charges on the PEG molecule and may have a significant effect on the dynamic behavior of macromolecule ions in gas.

Copyright © 2019 American Association for Aerosol Research     

In Situ Time-Resolved XAFS of Transitional States of Pt/C Cathode Electrocatalyst in an MEA During PEFC Loading with Transient Voltages

The transitional states of a Pt/C cathode electrocatalyst in the membrane electrode assembly of a polymer electrolyte fuel cell during loading with transient voltages were systematically analyzed by in situ time-resolved X-ray absorption fine structure with time resolution of 100 ms. The results suggest that the local coordination of the Pt cathode electrocatalyst was unaffected by the transient voltages during both rapid and gradual loading over 0–30 s.     

Crystallization of lead zirconate titanate without passing through pyrochlore by new solution process

We report a novel low-temperature crystallization path for perovskite lead zirconate titanate (PZT) from solution. The modification of a PZT solution by monoethanolamine (MEA) resulted in a change in the crystallization behavior. MEA was strongly coordinated to the metal ions, resulting in destroy of multinuclear metal organic complexes. This led to a remarkably increased pyrolysis temperature, and Pb²⁺ was reduced into Pb⁰ because of a reducing environment at 200–300 °C. Nanoscopic separations of Pb⁰ was later transformed into uniformly distributed α-PbO nanocrystals and clusters in the amorphous Zr/Ti–O matrix, and finally the sample crystallized into perovskite at 400–500 °C. On the other hand, pyrochlore phase was observed in the conventional crystallization process. The avoidance of pyrochlore formation is the key for the low-temperature crystallization of perovskite. X-ray absorption fine structure (XAFS) analysis was performed to reveal the structures in solutions and amorphous phases.     

日本中小型办公楼的节能措施

本文以本公司某大楼为例，通过收集和分析设备运行、环境状态相关的实测数据，探索研究行之有效的节能措施，并取得成效。     

Fine tuning of frontier orbital energy levels in dithieno[3,2-b:2′,3′-d]silole-based copolymers based on the substituent effect of phenyl pendants

A series of dithieno[3,2-b:2′,3′-d]silole-based π-conjugated copolymers containing thieno[3,4-c]pyrrole-4,6-dione or thieno[3,4-b]thiophene units bearing 4-substituted phenyl pendants were synthesized and their thermal stability, optical properties and frontier orbital energy levels were systematically investigated. The introduction of electron-withdrawing substituents on the phenyl rings lowered their frontier orbital energy levels without deteriorating their thermal and optical properties. By replacing an electron-donating methoxy group with an electron-withdrawing trifluoromethyl group, both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital energy levels of the polymers were deepened by more than 0.3 eV. A relatively linear relationship was observed between the HOMO energy levels and the Hammett substituent constants.     

Cell Profiling Based on Sugar-Chain–Cell Binding Interaction and Its Application to Typing and Quality Verification of Cells

Developing methods to determine cell type and cell state has been a significant challenge in the field of cancer diagnosis as well as in typing and quality verification for cultured cells. Herein, we report a cell profiling method based on binding interactions between cell-surface sugar-chain-binding proteins and sugar-chain-immobilized fluorescent nanoparticles (SFNPs), together with a method for cell typing and cell quality verification. Binding profiles of cells against sugar chains were analyzed by performing flow cytometry analysis with SFNPs. Discrimination analysis based on binding profiles could classify cell type and evaluate the quality of cultured cells. By applying our method to differentiated cells originating from conventional cell lines and also to mouse embryotic stem cells, we could detect the cells before and after differentiation. Our method can be utilized not only for the biofunctional analysis of cells but also for diagnosis of cancer cells and quality verification of cultured cells.     

Seedless growth of zinc oxide flower-shaped structures on multilayer graphene by electrochemical deposition

A seedless growth of zinc oxide (ZnO) structures on multilayer (ML) graphene by electrochemical deposition without any pre-deposited ZnO seed layer or metal catalyst was studied. A high density of a mixture of vertically aligned/non-aligned ZnO rods and flower-shaped structures was obtained. ML graphene seems to generate the formation of flower-shaped structures due to the stacking boundaries. The nucleation of ZnO seems to be promoted at the stacking edges of ML graphene with the increase of applied current density, resulting in the formation of flower-shaped structures. The diameters of the rods/flower-shaped structures also increase with the applied current density. ZnO rods/flower-shaped structures with high aspect ratio over 5.0 and good crystallinity were obtained at the applied current densities of −0.5 and −1.0 mA/cm². The growth mechanism was proposed. The growth involves the formation of ZnO nucleation below 80°C and the enhancement of the growth of vertically non-aligned rods and flower-shaped structures at 80°C. Such ZnO/graphene hybrid structure provides several potential applications in sensing devices.     

Synthesis of novel ABA triblock and (ABA)n multiblock copolymers comprised of polyisobutylene and poly(γ-benzyl-l-glutamate) segments

The synthesis of ABA triblock copolymers comprised of polyisobutylene (PIB) and poly(γ-benzyl-l-glutamate) (PBLG) segments has been demonstrated for the first time by the polymerization of γ-benzyl-l-glutamate N-carboxyanhydride (BLG-NCA) initiated with well-defined α,ω-primary amino-functional PIBs. The ammonium-mediated polymerization of BLG-NCA provided better control of molecular weights and lower polydispersity indices (PDIs) compared to the conventional polymerization. The compositional homogeneity of the block copolymers has been confirmed by GPC-MALLS and ¹H NMR spectroscopy. Since the resulting ABA triblock copolymer possessed primary amino groups at α,ω-ends, further extension reaction with 4,4′-methylene-bis(phenyldiisocyanate) was possible to afford a novel (ABA)_n multiblock copolymer.     

All-conjugated diblock copolymer of poly(3-hexylthiophene)-block-poly(3-phenoxymethylthiophene) for field-effect transistor and photovoltaic applications

The electronic properties, morphology and optoelectronic device characteristics of conjugated diblock copolythiophene, poly(3-hexylthiophene)-block -poly(3-phenoxymethylthiophene) (P3HT-b-P3PT), are firstly reported. The polymer properties and structures were explored through different solvent mixtures of chloroform (CHCl₃), dichlorobenzene (DCB), and CHCl₃:DCB (1:1 ratio). The absorption maximum (λ_max) of P3HT-b-P3PT prepared from DCB was around 554 nm with a shoulder peak indicative for the highly crystalline structure around 604 nm while that from CHCl₃ was 516 nm without the clear shoulder peak. The field-effect hole mobility of P3HT-b-P3PT increased from ～6.0 × 10^?3, ～8.0 × 10^?3 to ～2.0 × 10^?2 cm² V^?1 s^?1 as the DCB content in the solvent mixture enhanced. The AFM images suggested that the highly volatile CHCl₃ processing solvent led to the amorphous structure, on the other hand, less volatile DCB resulted in the largely crystalline structure of the P3HT-b-P3PT. Such difference on the polymer structure and hole mobility led to the varied power conversion efficiency (PCE) of the photovoltaic cells fabricated from the blend of P3HT-b-P3PT/[6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) (1:1, w/w): 1.88 (CHCl₃), 2.13 (CHCl₃:DCB (1:1)), and 2.60% (DCB). The PCBM blend ratio also significantly affected the surface structure and the solar cell performance. The PCE of polymer/PCBM could be improved to 2.80% while the ratio of polymer to PCBM went to 1:0.7. The present study suggested that the surface structures and optoelectronic device characteristics of conjugated diblock copolymers could be easily manipulated by the processing solvent, the block segment characteristic, and blend composition.