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排序方式: 共有169条查询结果,搜索用时 15 毫秒
101.
Giovanni Maizza Renato Pero Saulius Kaciulis Eleonora Bolli Hyeonjin Eom Minsu Lee Tai Hong Yim 《Surface and interface analysis : SIA》2020,52(12):907-913
The outstanding mechanical strength of as-deposited DC-electrodeposited nanocrystalline (nc) Ni-Fe alloys has been the subject of numerous researches in view of their scientific and practical interest. However, recent studies have reported a dramatic drop in ductility upon annealing above 350°C, associated with a concomitant abnormal rapid grain growth. The inherent cause has been ascribed to the presence of a detrimental product or by product in the bath, which affects either the microstructure or causes defects in the concentration and/or distribution of the as-deposited films. The present work has been inspired by the observed abnormal behaviour of annealed electrodeposited nc Ni-Fe alloy, which has here been addressed by considering the relationship between the composition of the bath (iron-chloride, nickel-sulphate solution, saccharin and ascorbic acid) and deposition defects (e.g. grain boundary pores) in the case of an nc Ni-Fe (Fe 48 wt%) alloy. The current investigations have included X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) in both as-deposited and post-annealed conditions (300°C–400°C). XPS depth profiling with Ar ion sputtering showed a significant amount of C and O impurities entrapped in the foils during deposition. As such impurities are often overlooked in common analytical techniques, new scenarios may need to be rationalised to explain the observed drop in tensile ductility of the as-deposited Ni-Fe alloys. 相似文献
102.
Dinesh G. Dan
Patel Yu‐ya Ohnishi Yixing Yang Sang‐Hyun Eom Richard T. Farley Kenneth R. Graham Jiangeng Xue So Hirata Kirk S. Schanze John R. Reynolds 《Journal of Polymer Science.Polymer Physics》2011,49(8):557-565
We report the synthesis of a 3‐ethylhexyloxy substituted poly(meta‐phenylene), EHO‐PMP that shows absorption and solid state photoluminescence exclusively in the UV region of the electromagnetic spectrum with an emission maximum of 345 nm. Computational analysis of model oligomers by DFT methods indicates that EHO‐PMP is a wide bandgap polymer with the HOMO being localized on a dimeric (biphenyl) unit and with the LUMO being more delocalized. The energy of the LUMO, however, suggests that inefficient electron injection would occur from currently available cathode materials in standard light‐emitting device architectures, and this was observed experimentally. The computational results, coupled with experimental observation, lead us to believe that efficient electroluminescence from organic polymer UV emitters requires advances in electron transport layers and cathode materials. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献
103.
Intrinsic handedness encountered in molecular sciences plays an essential role in diverse physical, chemical and biological processes. Optical activity spectroscopy has enabled one to characterize such molecular handedness (chirality) and demonstrated its unique ability to provide stereo-specific structural insight into chiral molecular systems including biopolymers, chiral drugs, and superchiral materials. However, more extended applications including time-resolved studies have often been hindered by inherent limitations of conventional differential methods utilizing both left- and right-handed radiations. The latest methodological advance is heterodyned detection methods measuring wave interferences between signal and reference fields, which allowed direct characterizations of coherent chiroptical signals in a flash. With its ultimate sensitivity, the heterodyned chiroptical method promises to open new possibilities of transient electronic or vibrational optical activity measurements in the ultrafast time domain. 相似文献
104.
Single-molecule mechanical manipulation has enabled quantitative understanding of not only the kinetics of both bond rupture and protein unfolding, but also the free energy landscape of chemical bond and/or protein folding. Despite recent studies reporting the role of loading device in bond rupture, a loading device effect on protein unfolding mechanics has not been well studied. In this work, we have studied the effect of loading-device stiffness on the kinetics of both bond rupture and protein unfolding mechanics using Brownian dynamics simulations. It is shown that bond rupture forces are dependent on not only loading rate but also the stiffness of loading device, and that protein unfolding mechanics is highly correlated with the stiffness of loading device. Our study sheds light on the importance of loading device effect on the mechanically induced bond ruptures and protein unfolding. 相似文献
105.
Kim S Jung E Kim MJ Pyo A Palani T Eom MS Han MS Lee S 《Chemical communications (Cambridge, England)》2012,48(70):8751-8753
A paper-based colorimetric iodide sensor (PBCIS) that consists of filter paper treated with starch and an oxidant is developed. It has been employed as a protocol to obtain the extent of conversion of aryl iodides in C-C, C-N, C-O and C-S bond formations, including polymer-supported Heck reactions, by transition metal catalysts such as palladium, nickel and copper. 相似文献
106.
Eom MS Jang W Lee YS Choi G Kwon YU Han MS 《Chemical communications (Cambridge, England)》2012,48(45):5566-5568
In this study, the use of bi-ligand co-functionalized gold nanoparticles in a highly selective and sensitive colorimetric probe for Ca(2+) ions is demonstrated and this probe also determined the concentrations of Ca(2+) ions in serum samples. 相似文献
107.
Kim E Kim HC Lee SG Lee SJ Go TJ Baek CS Jeong SW 《Chemical communications (Cambridge, England)》2011,47(43):11900-11902
The complexes of C-reactive protein (CRP) with its polymerizable phosphocholine ligands adsorbed at the styrene-water interface were polymerized. The molecularly imprinted polymer (MIP) exhibited a binding affinity for CRP comparable to that of immobilized anti-CRP antibody. The determination of human serum CRP using the MIP-based sandwich immunoassay has been demonstrated. 相似文献
108.
Sang-sun Park Seon-mi Eom Dong Ho Seo Yong-gun Shul 《Research on Chemical Intermediates》2010,36(1):77-82
TiO2 nanotube arrays were grown on Ti foil in mixed electrolyte by the anodizing process. TiO2 nanotube arrays were immersed in the TiCl4 solution to improve the photocurrent by enhanced charge transfer between TiO2 and dye molecules on the activity surface. Internal resistance of dye-sensitized solar cells (DSSC) was measured by impedance spectroscopy measurements. Backside illuminated DSSC with TiCl4-treated TiO2 nanotubes exhibited a conversion efficiency of 1.45% and showed improved electron transfer. 相似文献
109.
Danim Lim Hyunjoong Kim Jintaek Gong Jae-Hoon Eom Eunyoung Yoon Prof. Russell W. Driver Prof. Mu-Hyun Baik Prof. Hee-Seung Lee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(9):2226-2233
The rational design of self-assembling organic materials is extremely challenging due to the difficulty in precisely predicting solid-state architectures from first principles, especially if synthons are conformationally flexible. A tractable model system to study self-assembly was constructed by appending cyclopropanoyl caps to the N termini of helical α/β-peptide foldamers, designed to form both N−H⋅⋅⋅O and Cα−H⋅⋅⋅O hydrogen bonds, which then rapidly self-assembled to form foldectures (foldamer architectures). Through a combined analytical and computational investigation, cyclopropanoyl capping was observed to markedly enhance self-assembly in recalcitrant substrates and direct the formation of a single intermolecular N−H⋅⋅⋅O/Cα−H⋅⋅⋅O bonding motif in single crystals, regardless of peptide sequence or foldamer conformation. In contrast to previous studies, foldamer constituents of single crystals and foldectures assumed different secondary structures and different molecular packing modes, despite a conserved N−H⋅⋅⋅O/Cα−H⋅⋅⋅O bonding motif. DFT calculations validated the experimental results by showing that the N−H⋅⋅⋅O/Cα−H⋅⋅⋅O interaction created by the cap was sufficiently attractive to influence self-assembly. This versatile strategy to harness secondary noncovalent interactions in the rational design of self-assembling organic materials will allow for the exploration of new substrates and speed up the development of novel applications within this increasingly important class of materials. 相似文献
110.
Taesik Eom Jisoo Jeon Seunghyeon Lee Kyungbae Woo Jae Eun Heo David C. Martin Jeong Jae Wie Bong Sup Shim 《Particle & Particle Systems Characterization》2019,36(10)
The development of electronic devices from naturally derived materials is of enormous scientific interest. Melanin, a dark protective pigment ubiquitous in living creatures, may be particularly valuable because of its ability to conduct charges both electronically and ionically. However, device applications are severely hindered by its relatively poor electrical properties. Here, the facile preparation of conductive melanin composites is reported in which melanin nanoparticles (MNPs), directly extracted from squid inks, form electrically continuous junctions by tight clustering in a poly(vinyl alcohol) (PVA) matrix. Prepared as freestanding films and patterned microstructures by a series of precipitation, dry casting, and post‐thermal annealing steps, the percolated composites show electrical conductivities as high as 1.17 ± 0.13 S cm?1 at room temperature, which is the best performance yet obtained with biologically‐derived nanoparticles. Furthermore, the biodegradability of the MNP/PVA composites is confirmed through appetitive ingestion by Zophobas morios larvae (superworms). This discovery for preparing versatile biocomposites suggests new opportunities in functional material selections for the emerging applications of implantable, edible, green bioelectronics. 相似文献