共查询到20条相似文献,搜索用时 15 毫秒
1.
Dr. Da‐Young Sung Dr. Jayavant L. Gunjakar Dr. Tae Woo Kim Dr. In Young Kim Yu Ri Lee Prof. Seong‐Ju Hwang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(22):7109-7117
A new prompt room temperature synthetic route to 2D nanostructured metal oxide–graphene‐hybrid electrode materials can be developed by the application of colloidal reduced graphene oxide (RGO) nanosheets as an efficient reaction accelerator for the synthesis of δ‐MnO2 2D nanoplates. Whereas the synthesis of the 2D nanostructured δ‐MnO2 at room temperature requires treating divalent manganese compounds with persulfate ions for at least 24 h, the addition of RGO nanosheet causes a dramatic shortening of synthesis time to 1 h, underscoring its effectiveness for the promotion of the formation of 2D nanostructured metal oxide. To the best of our knowledge, this is the first example of the accelerated synthesis of 2D nanostructured hybrid material induced by the RGO nanosheets. The observed acceleration of nanoplate formation upon the addition of RGO nanosheets is attributable to the enhancement of the oxidizing power of persulfate ions, the increase of the solubility of precursor MnCO3, and the promoted crystal growth of δ‐MnO2 2D nanoplates. The resulting hybridization between RGO nanosheets and δ‐MnO2 nanoplates is quite powerful not only in increasing the surface area of manganese oxide nanoplate but also in enhancing its electrochemical activity. Of prime importance is that the present δ‐MnO2–RGO nanocomposites show much superior electrode performance over most of 2D nanostructured manganate systems including a similar porous assembly of RGO and layered MnO2 nanosheets. This result underscores that the present RGO‐assisted solution‐based synthesis can provide a prompt and scalable method to produce nanostructured hybrid electrode materials. 相似文献
2.
The Rapid Exfoliation and Subsequent Restacking of Layered Titanates Driven by an Acid–Base Reaction
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Huiyu Yuan David Dubbink Dr. Rogier Besselink Prof. Johan E. ten Elshof 《Angewandte Chemie (International ed. in English)》2015,54(32):9239-9243
Two‐dimensional (2D) (hydro)oxide materials, that is, nanosheets, enable the preparation of advanced 2D materials and devices. The general synthesis route of nanosheets involves exfoliating layered metal (hydro)oxide crystals. This exfoliation process is considered to be time‐consuming, hindering their industrial‐scale production. Based on in situ exfoliation studies on the protonated layered titanate H1.07Ti1.73O4?H2O (HTO), it is now shown that ion intercalation‐assisted exfoliation driven by chemical reaction provides a viable and fast route to isolated nanosheets. Contrary to the general expectation, data indicate that direct exfoliation of HTO occurs within seconds after mixing of the reactants, instead of proceeding via a swollen state as previously thought. These findings reveal that ion intercalation‐assisted exfoliation driven by chemical reaction is a promising exfoliation route for large‐scale synthesis. 相似文献
3.
Jang Mee Lee In Young Kim Song Yi Han Tae Woo Kim Prof. Seong‐Ju Hwang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(43):13800-13809
Graphene nanosheets are successfully applied as an effective platform for the 2D ordering of metal oxide nanoparticles. Mesoporous 2D aggregates of anatase TiO2 nanoparticles are synthesized by the heat treatment of the uniformly hybridized nanocomposite of layered titanate–reduced graphene oxide (RGO) at elevated temperatures. The precursor layered titanate–RGO nanocomposite is prepared by self‐assembly of anionic RGO nanosheets and cationic TiO2 nanosols. The calcination of the as‐prepared layered titanate–RGO nanocomposite at 500 °C induces a structural and morphological change of layered titanate nanoplates into anatase TiO2 nanoparticles without significant modification of the RGO nanosheet. Increasing the heating temperature to 600 °C gives rise to elimination of the RGO component, leading to the formation of sheetlike porous aggregates of RGO‐free TiO2 nanoparticles. The nanocomposites calcined at 500–700 °C display promising functionality as negative electrodes for lithium ion batteries. Among the present calcined derivatives, the 2D sheet‐shaped aggregate of TiO2 nanoparticles obtained from calcination at 600 °C delivers the greatest specific discharge capacity with good capacity retention for all current density conditions applied. Such superior electrode performance of the nanocomposite calcined at 600 °C is attributable both to the improved stability of the crystal structure and crystal morphology of titania and to the enhancement of Li+ ion transport through the enlargement of mesopores. The present findings clearly demonstrate the usefulness of RGO nanosheets as a platform for 2D‐ordered superstructures of metal oxide nanoparticles with improved electrode performance. 相似文献
4.
Li L Ma R Ebina Y Fukuda K Takada K Sasaki T 《Journal of the American Chemical Society》2007,129(25):8000-8007
Exfoliated oxide nanosheets such as Ti0.91O2 and Ca2Nb3O10 and layered double hydroxide (LDH) nanosheets of Mg2/3Al1/3(OH)2 were restacked into inorganic sandwich layered materials. Sequential adsorption of these oppositely charged nanosheets from their colloidal suspensions yielded multilayer ultrathin films while their simple mixing produced lamellar flocculates. Eliminating carbonate ions from the reaction system was found to be essential for successfully achieving the sandwich structures. The flocculated materials as well as the films were characterized by atomic force microscopy (AFM), UV-visible absorption spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and chemical analysis, which all supported the formation of the ordered sandwich structures. AFM observations revealed alternate dense tiling of LDH nanosheets and oxide nanosheets onto a substrate surface. UV-visible absorption spectra exhibited progressive enhancement of optical density due to oxide nanosheets as a function of deposition cycles, providing strong evidence for regular growth of multilayer films. The combinations of Mg2/3Al1/3(OH)2/Ti0.91O2 and Mg2/3Al1/3(OH)2/Ca2Nb3O10 produced XRD Bragg peaks having multilayer spacings of 1.2 and 2.0 nm, respectively. These basal spacing values are compatible with the sum of thickness of LDH nanosheets and corresponding oxide nanosheets. TEM images of flocculated samples displayed lamellar features with two different constituent layers appearing alternately. 相似文献
5.
《化学:亚洲杂志》2017,12(19):2528-2532
A 3D highly interconnected macroporous network of reduced GO having finely dispersed few‐layered 2D MoS2 nanosheets was constructed through direct use of acidic graphite oxide (GO) for the first time. This facile and technologically scalable process can afford efficient hydrodesulfurization electrocatalysts as potential anode materials at lower cost, and can circumvent the poor thermal stability and recyclability of the material. The strategy provided here can be the basis to design and develop practical processes to address the ultimate goal of large‐scale manufacturing of hybrids composed of 2D materials for various energy and catalysis applications. 相似文献
6.
Kihong Lee Bonnie Choi Dr. Ilan Jen‐La Plante Maria V. Paley Xinjue Zhong Prof. Andrew C. Crowther Prof. Jonathan S. Owen Prof. Xiaoyang Zhu Prof. Xavier Roy 《Angewandte Chemie (International ed. in English)》2018,57(21):6125-6129
Two‐dimensional (2D) materials are commonly prepared by exfoliating bulk layered van der Waals crystals. The creation of synthetic 2D materials from bottom‐up methods is an important challenge as their structural flexibility will enable chemists to tune the materials properties. A 2D material was assembled using C60 as a polymerizable monomer. The C60 building blocks are first assembled into a layered solid using a molecular cluster as structure director. The resulting hierarchical crystal is used as a template to polymerize its C60 monolayers, which can be exfoliated down to 2D crystalline nanosheets. Derived from the parent template, the 2D structure is composed of a layer of inorganic cluster, sandwiched between two monolayers of polymerized C60. The nanosheets can be transferred onto solid substrates and depolymerized by heating. Electronic absorption spectroscopy reveals an optical gap of 0.25 eV, narrower than that of the bulk parent crystalline solid. 相似文献
7.
Wang H Wang Y Xu J Yang H Lee CS Rogach AL 《Langmuir : the ACS journal of surfaces and colloids》2012,28(28):10597-10601
Single crystalline SnO nanosheets with exposed {001} facets have been prepared by an ultrasonic aqueous synthesis in the presence of polyvinylpyrrolidone, which hinders the spontaneous formation of the truncated bipyramidal SnO microcrystals and exfoliate them into layer-by-layer hierarchical structures and further into separate SnO nanosheets. The SnO nanosheets have been used as conformal sacrificial templates converted into polycrystalline SnO(2), as well as layered SnO/SnO(2) nanostructures, by calcination in air. The concept of fabrication of two-dimensional tin oxide nanostructures demonstrated here may be relevant for the crystal design of layered materials, in general. 相似文献
8.
The dimensionality decrease from three-dimensional (3D) bulk to two-dimensional (2D) nanosheets was expected to made a significant influence on the physical-chemical properties of layered materials, which are of importance for materials design with enhanced functionalities. Here, in this work, we have demonstrated that a layered material, that has shown paramagnetic behavior at 3D bulk state, has displayed remarkable antiferromagnetic behavior with Neel temperature large to be about 140 K for the 2D nanosheets. This dramatical variation has been interpreted as the spin canting of the center metal ions as a result of enhancement in metal-to-ligand charge transfer between ligand and metal center, and d-d transition for metal ions, upon exfoliation. As a consequence, thermal and light irradiation-induced reversible spin-state switching, for both in colloidal suspension and at solid state, have been observed with 2D nanosheets. Compared with the performance enhancement in the literature, this kind of dimensionality decrease leading to subversive performance variations may open a new drive for creation of novel functions with nanomaterials. 相似文献
9.
10.
Jiahao Guo Yitao Cao Run Shi Geoffrey I. N. Waterhouse Li‐Zhu Wu Chen‐Ho Tung Tierui Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8531-8535
Synthesizing nanomaterials with anisotropic architectures, especially two‐dimensional (2D) nanosheets (NSs), is a key focus of materials science research. Metal sulfide nanosheets (MSNSs) are typically obtained involving exfoliation of bulk metal sulfides with layered structures. The synthesis of NSs of intrinsically non‐layered metal sulfides has received relatively less attention. Metal alkanethiolates with lamellar structures are now shown to serve as effective scaffolds for constructing NSs. A novel photochemical step was employed to transform 2D metal thiolates into MSNSs. By this strategy the 2D nature of metal thiolate precursors was preserved in the final products, resulting in the successful synthesis of NSs of binary PbS, CdS, and Cu9S5, as well as ternary wurtzite CuInS2, Cu2SnS3. Results encourage the wider utilization of photochemical strategies in the synthesis of anisotropic MSNSs. 相似文献
11.
A Direct Hybridization between Isocharged Nanosheets of Layered Metal Oxide and Graphene through a Surface‐Modification Assembly Process
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Kanyaporn Adpakpang Seung Mi Oh Xiaoyan Jin Prof. Dr. Seong‐Ju Hwang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15459-15466
An efficient and universal method to directly hybridize isocharged nanosheets of layered metal oxide and reduced graphene oxide (rGO) is developed on the basis of the surface modification and an electrostatically driven assembly process. On the basis of this synthetic method, the CoO2–rGO nanocomposite can be synthesized with exfoliated CoO2 and rGO nanosheets, and transformed into CoO–CoO2–rGO nanocomposites with excellent electrode performance for lithium‐ion batteries. Also, this surface‐modification assembly route is successfully applied for the synthesis of another mesoporous TiO2–rGO nanocomposite. This result provides clear evidence for the usefulness of the present method as a universal way of hybridizing isocharged anionic nanosheets of inorganic solids and graphene. 相似文献
12.
Tae Woo Kim Eun‐Jin Oh Ah‐Young Jee Seung Tae Lim Dae Hoon Park Minyung Lee Sang‐Hoon Hyun Prof. Jin‐Ho Choy Prof. Seong‐Ju Hwang Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(41):10752-10761
A colloidal suspension of exfoliated, layered cobalt oxide nanosheets has been synthesized through the intercalation of quaternary tetramethylammonium ions into protonated lithium cobalt oxide. According to atomic force microscopy, exfoliated nanosheets of layered cobalt oxide show a plateau‐like height profile with nanometer‐level height, underscoring the formation of unilamellar 2D nanosheets. The exfoliation of layered cobalt oxide was cross‐confirmed by X‐ray diffraction, UV/Vis spectroscopy, and transmission electron microscopy. The maintenance of the hexagonal in‐plane structure of the cobalt oxide lattice after the exfoliation process was evidenced by selected‐area electron diffraction and Co K‐edge X‐ray absorption near‐edge structure analysis. The zeta‐potential measurements clearly demonstrated the negative surface charge of cobalt oxide nanosheets. Adopting the nanosheets of layered cobalt oxide as a precursor, we were able to prepare the monodisperse CoO nanocrystals with a particle size of ≈10 nm as well as the heterolayered film composed of cobalt oxide monolayer and polycation. 相似文献
13.
Dr. Hewei Zhao Prof. Yujie Zhu Dr. Fengshi Li Dr. Rui Hao Dr. Shaoxiong Wang Prof. Lin Guo 《Angewandte Chemie (International ed. in English)》2017,56(30):8766-8770
Two-dimensional (2D) nanomaterials show unique electrical, mechanical, and catalytic performance owing to their ultrahigh surface-to-volume ratio and quantum confinement effects. However, ways to simply synthesize 2D metal oxide nanosheets through a general and facile method is still a big challenge. Herein, we report a generalized and facile strategy to synthesize large-size ultrathin 2D metal oxide nanosheets by using graphene oxide (GO) as a template in a wet-chemical system. Notably, the novel strategy mainly relies on accurately controlling the balance between heterogeneous growth and nucleation of metal oxides on the surface of GO, which is independent on the individual character of the metal elements. Therefore, ultrathin nanosheets of various metal oxides, including those from both main-group and transition elements, can be synthesized with large size. The ultrathin 2D metal oxide nanosheets also show controllable thickness and unique surface chemical state. 相似文献
14.
Generalized Low‐Temperature Fabrication of Scalable Multi‐Type Two‐Dimensional Nanosheets with a Green Soft Template
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Lanfang Wang Chuang Song Yi Shi Liyun Dang Ying Jin Hong Jiang Prof. Dr. Qingyi Lu Prof. Dr. Feng Gao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(16):5575-5582
Two‐dimensional nanosheets with high specific surface areas and fascinating physical and chemical properties have attracted tremendous interests because of their promising potentials in both fundamental research and practical applications. However, the problem of developing a universal strategy with a facile and cost‐effective synthesis process for multi‐type ultrathin 2 D nanostructures remains unresolved. Herein, we report a generalized low‐temperature fabrication of scalable multi‐type 2 D nanosheets including metal hydroxides (such as Ni(OH)2, Co(OH)2, Cd(OH)2, and Mg(OH)2), metal oxides (such as ZnO and Mn3O4), and layered mixed transition‐metal hydroxides (Ni‐Co LDH, Ni‐Fe LDH, Co‐Fe LDH, and Ni‐Co‐Fe layered ternary hydroxides) through the rational employment of a green soft‐template. The synthesized crystalline inorganic nanosheets possess confined thickness, resulting in ultrahigh surface atom ratios and chemically reactive facets. Upon evaluation as electrode materials for pseudocapacitors, the Ni‐Co LDH nanosheets exhibit a high specific capacitance of 1087 F g?1 at a current density of 1 A g?1, and excellent stability, with 103 % retention after 500 cycles. This strategy is facile and scalable for the production of high‐quality ultrathin crystalline inorganic nanosheets, with the possibility of extension to the preparation of other complex nanosheets. 相似文献
15.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(30):8892-8896
Two‐dimensional (2D) nanomaterials show unique electrical, mechanical, and catalytic performance owing to their ultrahigh surface‐to‐volume ratio and quantum confinement effects. However, ways to simply synthesize 2D metal oxide nanosheets through a general and facile method is still a big challenge. Herein, we report a generalized and facile strategy to synthesize large‐size ultrathin 2D metal oxide nanosheets by using graphene oxide (GO) as a template in a wet‐chemical system. Notably, the novel strategy mainly relies on accurately controlling the balance between heterogeneous growth and nucleation of metal oxides on the surface of GO, which is independent on the individual character of the metal elements. Therefore, ultrathin nanosheets of various metal oxides, including those from both main‐group and transition elements, can be synthesized with large size. The ultrathin 2D metal oxide nanosheets also show controllable thickness and unique surface chemical state. 相似文献
16.
Liping Kang Gaini Zhang Yunlong Bai Huanjing Wang Zhibin Lei Zonghuai Liu 《物理化学学报》2020,36(2):1905032-0
功率密度高、倍率性能优异和循环性能好等特性使得超级电容器在储能领域显示了巨大的应用前景。尽管二维层状材料剥离形成的纳米片层不仅可为电化学反应提供独特的纳米级反应空间,而且由其组装的层状纳米电极材料具有化学和结构上的氧化还原可逆性及纳米片层水平方向上离子或电子快速传输通道。但是,纳米片层组装电极材料在纳米片层垂直方向上离子或电子传输存在障碍,对于超级电容器功率密度和能量密度的提高及实现快速能量储存非常不利。因此,如何通过改善离子或电子的快速传输,实现超级电容器大功率密度下的高能量密度是超级电容器电极材料发展的方向之一。本文主要综述了二维层状材料剥离成纳米片层,纳米片层孔洞化策略及组装孔洞化材料在超级电容器电极材料中的应用。纳米层孔洞化技术是改善层状电极材料在纳米片层垂直方向离子或电子传输的有效手段,为实现高比电容下的高倍率性能超级电容器电极材料制备提供了方法学。最后,对开发大功率密度下的高能量密度超级电容器电极材料提出了展望。 相似文献
17.
A Molecular Pillar Approach To Grow Vertical Covalent Organic Framework Nanosheets on Graphene: Hybrid Materials for Energy Storage
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Dr. Jinhua Sun Alexey Klechikov Calin Moise Dr. Mariana Prodana Prof. Marius Enachescu Prof. Alexandr V. Talyzin 《Angewandte Chemie (International ed. in English)》2018,57(4):1034-1038
Hybrid 2D–2D materials composed of perpendicularly oriented covalent organic frameworks (COFs) and graphene were prepared and tested for energy storage applications. Diboronic acid molecules covalently attached to graphene oxide (GO) were used as nucleation sites for directing vertical growth of COF‐1 nanosheets (v‐COF‐GO). The hybrid material has a forest of COF‐1 nanosheets with a thickness of 3 to 15 nm in edge‐on orientation relative to GO. The reaction performed without molecular pillars resulted in uncontrollable growth of thick COF‐1 platelets parallel to the surface of GO. The v‐COF‐GO was converted into a conductive carbon material preserving the nanostructure of precursor with ultrathin porous carbon nanosheets grafted to graphene in edge‐on orientation. It was demonstrated as a high‐performance electrode material for supercapacitors. The molecular pillar approach can be used for preparation of many other 2D‐2D materials with control of their relative orientation. 相似文献
18.
S. Kannan 《Catalysis Surveys from Asia》2006,10(3-4):117-137
Hydrotalcite-like (HT-like) materials have been studied extensively in the last three decades. Although these materials initially perceived as potential anion exchangers, unrelenting efforts have also been attempted to use them as catalytic materials or as catalytic supports. There are varied ways by which one can use them for catalysis viz.; 1. Use them in as-synthesized form 2. Use them after calcining where the structural integrity of layered lattice is lost 3. Use the interlayer as functional spaces with moieties of catalytic interest 4. Use them after destruction or delamination and restructuring and 5. Use them as support or matrix. In this review, we are reporting the catalytic applications of HT-like materials and their derived forms carried out in our research group for the last 15 years in these various ways, covering reactions such as nitrous oxide decomposition, selective oxidation of organic compounds of industrial relevance and base-catalyzed isomerization of chemicals of perfumery interest. Although this review primarily focuses on our work, wherever applicable, related or relevant works from other groups are also presented to bestow comprehensiveness. 相似文献
19.
Two‐Dimensional Tellurium Nanosheets Exhibiting an Anomalous Switchable Photoresponse with Thickness Dependence
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Jing Peng Yu Pan Zhi Yu Jiajing Wu Junchi Wu Yuan Zhou Yuqiao Guo Prof. Xiaojun Wu Prof. Changzheng Wu Prof. Yi Xie 《Angewandte Chemie (International ed. in English)》2018,57(41):13533-13537
Two‐dimensional (2D) tellurium (Te) was recently predicted to be promising for diverse electronic and optoelectronic applications. However, the synthesis of high‐quality 2D Te structures remains challenging, which greatly hinders the exploration of its full properties. Herein, an anomalous photoresponse from negative to positive as a function of thickness in Te nanosheets is reported. Ultrathin Te layers with large size and clean interface were obtained through a topotactic transformation, in which the 2D Te structure was derived from a layered MTe2 (M=Ti, Mo, W) matrix by excessive lithiation. Prominently, the photoresponse in Te nanosheets exhibits negative behavior when the thickness is less than 5 nm, which turns positive as the thickness increases. This unusual photoresponse will shed light on the full exploration of 2D non‐layered materials with exotic properties. 相似文献
20.
Synthetic Strategies for Constructing Two‐Dimensional Metal‐Organic Layers (MOLs): A Tutorial Review
《中国化学》2018,36(8):754-764
Two‐dimensional (2D) metal‐organic layers (MOLs) are the 2D version of metal‐organic frameworks (MOFs) with nanometer thickness in one dimension. MOLs are also known as 2D‐MOFs, 2D coordination polymers, ultrathin MOF nanosheets (UMOFNs) or coordination nanosheets in literature. This new category of 2D materials has attracted a lot of interests because of the opportunity in combining molecular chemistry, surface/interface chemistry and material chemistry of low dimensional materials in these systems. Several synthetic strategies have been developed for the construction of 2D MOLs, but the general synthesis of MOLs still presents a challenge. This tutorial level review summarizes the recent progress in the fabrication of novel 2D MOLs and aims to highlight challenges in this field. 相似文献