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991.
992.
Moutusi Banerjee Abhisek Gupta Shyamal K. Saha Dipankar Chakravorty 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(28):3451-3457
Attachment of Li+ ion on graphene surface to realize Li+‐ion conductor is a real challenge because of the weak interaction between the ions and the functional groups of graphene oxide; although, a large number of theoretical results are already available in the literature. To overcome this problem, graphene oxide is functionalized by 1‐aza‐15‐crown‐5, the cage‐like structure containing four oxygens that can bind Li+ ion through electrostatic interaction. Li+ migration on graphene surface has been investigated using ac relaxation mechanism. Perfect Debye‐type relaxation behavior with β (relaxation exponent) value ≈1 resulting from single ion is observed. The activation energy of Li+ migration arising due to cation‐π interaction is found to be 0.37 eV, which agrees well with recently reported theoretical value. It is believed that this study will help to design isolated ion conductors for Li+‐ion battery. 相似文献
993.
Lihua Zhu Yingying Jiang Jinbao Zheng Nuowei Zhang Changlin Yu Yunhua Li Chih‐Wen Pao Jeng‐Lung Chen Chuanhong Jin Jyh‐Fu Lee Chuan‐Jian Zhong Bing H. Chen 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(34):4385-4393
The design of an ideal heterogeneous catalyst for hydrogenation reaction is to impart the catalyst with synergetic surface sites active cooperatively toward different reaction species. Herein a new strategy is presented for the creation of such a catalyst with dual active sites by decorating metal and metal oxide nanoparticles with ultrafine nanoclusters at atomic level. This strategy is exemplified by the design and synthesis of Ru nanoclusters supported on Ni/NiO nanoparticles. This Ru‐nanocluster/Ni/NiO‐nanoparticle catalyst is shown to exhibit ultrahigh catalytic activity for benzene hydrogenation reaction, which is 55 times higher than Ru–Ni alloy or Ru on Ni catalysts. The nanoclusters‐on‐nanoparticles are characterized by high‐resolution transmission electron microscope, Cs‐corrected high angle annular dark field‐scanning transmission electron microscopy, elemental mapping, high‐sensitivity low‐energy ion scattering, and X‐ray absorption spectra. The atomic‐scale nanocluster–nanoparticle structural characteristics constitute the basis for creating the catalytic synergy of the surface sites, where Ru provides hydrogen adsorption and dissociation site, Ni acts as a “bridge” for transferring H species to benzene adsorbed and activated at NiO site, which has significant implications to multifunctional nanocatalysts design for wide ranges of catalytic reactions. 相似文献
994.
Supramolecular Nanosubstrate‐Mediated Delivery for Reprogramming and Transdifferentiation of Mammalian Cells 下载免费PDF全文
995.
996.
Hongmei Ji Chao Liu Ting Wang Jing Chen Zhengning Mao Jin Zhao Wenhua Hou Gang Yang 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(48):6480-6490
Porous hierarchical architectures of few‐layer MoS2 nanosheets dispersed in carbon matrix are prepared by a microwave‐hydrothermal method followed by annealing treatment via using glucose as C source and structure‐directing agent and (NH4)2MoS4 as both Mo and S sources. It is found that the morphology and size of the secondary building units (SBUs), the size and layer number of MoS2 nanosheets as well as the distribution of MoS2 nanosheets in carbon matrix, can be effectively controlled by simply adjusting the molar ratio of (NH4)2MoS4 to glucose, leading to the materials with a low charge–transfer resistance, many electrochemical active sites and a robust structure for an outstanding energy storage performance including a high specific capacitance (589 F g−1 at 0.5 A g−1), a good rate capability (364 F g−1 at 20 A g−1), and an excellent cycling stability (retention 104% after 2000 cycles) for application in supercapacitors. The exceptional rate capability endows the electrode with a high energy density of 72.7 Wh kg−1 and a high power density of 12.0 kW kg−1 simultaneously. This work presents a facile and scalable approach for synthesizing novel heterostructures of MoS2‐based electrode materials with an enhanced rate capability and cyclability for potential application in supercapacitor. 相似文献
997.
An Atomistic Tomographic Study of Oxygen and Hydrogen Atoms and their Molecules in CVD Grown Graphene 下载免费PDF全文
Sung‐Il Baik Lulu Ma Yoon‐Jun Kim Bo Li Mingjie Liu Dieter Isheim Boris I. Yakobson Pulickel M. Ajayan David N. Seidman 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(44):5968-5974
The properties and growth processes of graphene are greatly influenced by the elemental distributions of impurity atoms and their functional groups within or on the hexagonal carbon lattice. Oxygen and hydrogen atoms and their functional molecules (OH, CO, and CO2) positions' and chemical identities are tomographically mapped in three dimensions in a graphene monolayer film grown on a copper substrate, at the atomic part‐per‐million (atomic ppm) detection level, employing laser assisted atom‐probe tomography. The atomistic plan and cross‐sectional views of graphene indicate that oxygen, hydrogen, and their co‐functionalities, OH, CO, and CO2, which are locally clustered under or within the graphene lattice. The experimental 3D atomistic portrait of the chemistry is combined with computational density‐functional theory (DFT) calculations to enhance the understanding of the surface state of graphene, the positions of the chemical functional groups, their interactions with the underlying Cu substrate, and their influences on the growth of graphene. 相似文献
998.
One‐Pot Synthesis of Tunable Crystalline Ni3S4@Amorphous MoS2 Core/Shell Nanospheres for High‐Performance Supercapacitors 下载免费PDF全文
Yu Zhang Wenping Sun Xianhong Rui Bing Li Hui Teng Tan Guilue Guo Srinivasan Madhavi Yun Zong Qingyu Yan 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(30):3694-3702
Transition metal sulfides gain much attention as electrode materials for supercapacitors due to their rich redox chemistry and high electrical conductivity. Designing hierarchical nanostructures is an efficient approach to fully utilize merits of each component. In this work, amorphous MoS2 is firstly demonstrated to show specific capacitance 1.6 times as that of the crystalline counterpart. Then, crystalline core@amorphous shell (Ni3S4@MoS2) is prepared by a facile one‐pot process. The diameter of the core and the thickness of the shell can be independently tuned. Taking advantages of flexible protection of amorphous shell and high capacitance of the conductive core, Ni3S4@amorphous MoS2 nanospheres are tested as supercapacitor electrodes, which exhibit high specific capacitance of 1440.9 F g?1 at 2 A g?1 and a good capacitance retention of 90.7% after 3000 cycles at 10 A g?1. This design of crystalline core@amorphous shell architecture may open up new strategies for synthesizing promising electrode materials for supercapacitors. 相似文献
999.
1000.
提出了基于双同步斩波模式的微功耗LED声控灯驱动电源设计方法。该驱动电源用一个单片机控制两个开关管分别为主电源和待机电源提供工作电流。主电源采用全波斩波工作模式为LED灯组提供工作电流;待机电源采用半波斩波工作模式,从而大幅降低了待机功耗。该驱动电源结构简单,可在50~60 Hz频率的180~250 V的宽电压范围内工作,具有恒流驱动功能和微功耗特性,且稳定可靠和较高的性价比。 相似文献