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131.
132.
Yan Guan Dayu Zhou Jin Xu Xiaohua Liu Fei Cao Xianlin Dong Johannes Müller Tony Schenk Uwe Schroeder 《固体物理学:研究快报》2015,9(10):589-593
A wealth of studies have confirmed that the low‐field hysteresis behaviour of ferroelectric bulk ceramics and thin films can be described using Rayleigh relations, and irreversible domain wall motion across the array of pining defects has been commonly accepted as the underlying micro‐mechanism. Recently, HfO2 thin films incorporated with various dopants were reported to show pronounced ferroelectricity, however, their microscopic domain structure remains unclear till now. In this work, the effects of the applied electric field amplitude, frequency and temperature on the sub‐coercive polarization reversal properties were investigated for 10 nm thick Si‐doped HfO2 thin films. The applicability of the Rayleigh law to ultra‐thin ferroelectric films was first confirmed, indicating the existence of a multi‐domain structure. Since the grain size is about 20–30 nm, a direct observation of domain walls within the grains is rather challenging and this indirect method is a feasible approach to resolve the domain structure. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
133.
134.
Xiande Yang Yongqian Wang Tingting Jiang Jun Yang Yinchang Li Qun Ma 《Crystal Research and Technology》2015,50(4):338-345
In this article, dendritic‐like CdS has been prepared by a hydrothermal method using thiourea as the sulfur source, and the effects of experimental conditions on the morphologies of CdS have been investigated. The performances of CdS have been analyzed by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and the fluorescence and photodegradation properties of CdS have also been investigated. The XRD result indicates that the dendritic‐like CdS are of hexagonal phase and they are highly crystallized. Also, the FESEM results show that the ratio of raw material affects the yield of CdS, the reaction time affects the morphology of CdS. The best morphology of CdS is dendritic structures and the length is about 6 μm. The fluorescence spectrum shows three peaks at 470 nm, 513 nm and 547 nm, which indicates that the dendritic‐like CdS mainly emits green and blue fluorescence. Moreover, the dendritic‐like CdS exhibits good photocatalytic activity and its photodegradation rate to methylene blue can reach 92%. The growth mechanism for the formation of CdS with dendritic structure is also described. 相似文献
135.
Xiande Yang Yongqian Wang Zhengshu Wang Qun Ma Junhan Kong Hanxiang Jia Meihua Yu 《Crystal Research and Technology》2015,50(8):658-667
In this article, flower‐like CdS structures have been prepared by a hydrothermal method with SDBS as surfactant. The influences of different experimental conditions on the morphologies, UV‐Vis and fluorescence properties of CdS have been investigated. The performances of CdS have been analyzed by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet‐visible (UV–Vis) and room‐temperature photoluminescence (PL). The XRD result indicates that the flower‐like CdS structures are of hexagonal phase. The FESEM results indicate that the main role of SDBS is to make the CdS crystals assemble together to form the flower‐like structures. The UV–Vis results show CdS has a strong absorption in the ultraviolet region and visible‐light region. The PL results show CdS has two emission peaks, respectively at 461 nm and 553 nm. The growth mechanism for the formation of flower‐like CdS structures is also described. 相似文献
136.
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138.
Zhi Zeng Ke Tang Qianmin Ma Qianming Wang 《Journal of Sol-Gel Science and Technology》2014,69(1):231-236
Magnolol and honokiol as pharmaceutical ligands have been introduced into terbium complex systems for the first time and two hybrid organic–inorganic materials were successfully prepared. Both of them can sensitize terbium characteristic green emission effectively based on intra-molecular energy transfer channel. Moreover, they selectively recognized Cu2+ and Fe3+ through luminescence quenching effects. The photophysical properties and morphological structures were extensively investigated. 相似文献
139.
An Unusual Triphenylphosphine Oxide Catalyzed Stereoselective 1,3‐Dichlorination of Unsaturated Ketoesters 下载免费PDF全文
Tian‐Yang Yu Yao Wang Peng‐Fei Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(1):98-101
An unusual Ph3PO‐catalyzed stereoselective 1,3‐dicholorination of an unsaturated ketoester has been developed. The novel activation mode involved in this cascade reaction can promote consecutively elusive transformations. The products were obtained with good yields and excellent stereoselectivities. This reaction makes important complementation to the limitations associated with the field of dichlorination. 相似文献
140.
Organocatalytic and Scalable Synthesis of the Anti‐Influenza Drugs Zanamivir,Laninamivir, and CS‐8958 下载免费PDF全文
Yunsheng Li Prof. Dr. Dawei Ma 《Angewandte Chemie (International ed. in English)》2014,53(50):13885-13888
Zanamivir, laninamivir, and CS‐8958 are three neuraminidase inhibitors that have been clinically used to combat influenza. We report herein a novel organocatalytic route for preparing these agents. Only 13 steps are needed for the assembly of zanamivir and laninamivir from inexpensive D ‐araboascorbic acid by this synthetic route, which relies heavily on a thiourea‐catalyzed enantioselective Michael addition of acetone to tert‐butyl (2‐nitrovinyl)carbamate and an anti‐selective Henry reaction of the resulting Michael adduct with an aldehyde prepared from D ‐araboascorbic acid. The synthetic procedures are scalable, as evident from the preparation of more than 3.5 g of zanamivir. 相似文献