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1.
Ultrafast Discharge/Charge Rate and Robust Cycle Life for High‐Performance Energy Storage Using Ultrafine Nanocrystals on the Binder‐Free Porous Graphene Foam 下载免费PDF全文
Gyu Heon Lee Jung Woo Lee Ji IL Choi Sang Jun Kim Yong‐Hoon Kim Jeung Ku Kang 《Advanced functional materials》2016,26(28):5139-5148
A hierarchical architecture fabricated by integrating ultrafine titanium dioxide (TiO2) nanocrystals with the binder‐free macroporous graphene (PG) network foam for high‐performance energy storage is demonstrated, where mesoporous open channels connected to the PG facilitate rapid ionic transfer during the Li‐ion insertion/extraction process. Moreover, the binder‐free conductive PG network in direct contact with a current collector provides ultrafast electronic transfer. This structure leads to unprecedented cycle stability, with the capacity preserved with nearly 100% Coulombic efficiency over 10 000 Li‐ion insertion/extraction cycles. Moreover, it is proven to be very stable while cycling 10 to 100‐fold longer compared to typical electrode structures for batteries. This facilitates ultrafast charge/discharge rate capability even at a high current rate giving a very short charge/discharge time of 40 s. Density functional theory calculations also clarify that Li ions migrate into the TiO2–PG interface then stabilizing its binder‐free interface and that the Li ion diffusion occurs via a concerted mechanism, thus resulting in the ultrafast discharge/charge rate capability of the Li ions into ultrafine nanocrystals. 相似文献
2.
S.A. Haque T. Park C. Xu S. Koops N. Schulte R.J. Potter A.B. Holmes J.R. Durrant 《Advanced functional materials》2004,14(5):435-440
The control of interfacial charge transfer is central to the design of photovoltaic devices. This charge transfer is strongly dependent upon the local chemical environment at each interface. In this paper we report a methodology for the fabrication of a novel nanostructured multicomponent film, employing a dual‐function supramolecular organic semiconductor to allow molecular‐level control of the local chemical composition at a nanostructured inorganic/organic semiconductor heterojunction. The multicomponent film comprises a lithium ion doped dual‐functional hole‐transporting material (Li+–DFHTM), sandwiched between a dye‐sensitized nanocrystalline TiO2 film and a mono‐functional organic hole‐transporting material (MFHTM). The DFHTM consists of a conjugated organic semiconductor with ion supporting side chains, designed to allow both electronic and ionic charge transport properties. The Li+–DFHTM layers provide a new and versatile way to control the interface electrostatics, and consequently the charge transfer, at a nanostructured dye‐sensitized inorganic/organic semiconductor heterojunction. 相似文献
3.
Ultrahigh Tunability of Room Temperature Electronic Transport and Ferromagnetism in Dilute Magnetic Semiconductor and PMN‐PT Single‐Crystal‐Based Field Effect Transistors via Electric Charge Mediation 下载免费PDF全文
Qiu‐Xiang Zhu Ming‐Min Yang Ming Zheng Ren‐Kui Zheng Li‐Jie Guo Yu Wang Jin‐Xing Zhang Xiao‐Min Li Hao‐Su Luo Xiao‐Guang Li 《Advanced functional materials》2015,25(7):1111-1119
Multiferroic heterostructures composed of complex oxide thin films and ferroelectric single crystals have aroused considerable interest due to the electrically switchable strain and charge elements of oxide films by the polarization reversal of ferroelectrics. Previous studies have demonstrated that the electric‐field‐control of physical properties of such heterostructures is exclusively due to the ferroelectric domain switching‐induced lattice strain effects. Here, the first successful integration of the hexagonal ZnO:Mn dilute magnetic semiconductor thin films with high performance (111)‐oriented perovskite Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT) single crystals is reported, and unprecedented charge‐mediated electric‐field control of both electronic transport and ferromagnetism at room temperature for PMN‐PT single crystal‐based oxide heterostructures is realized. A significant carrier concentration‐tunability of resistance and magnetization by ≈400% and ≈257% is achieved at room temperature. The electric‐field controlled bistable resistance and ferromagnetism switching at room temperature via interfacial electric charge presents a potential strategy for designing prototype devices for information storage. The results also disclose that the relative importance of the strain effect and interfacial charge effect in oxide film/ferroelectric crystal heterostructures can be tuned by appropriately adjusting the charge carrier density of oxide films. 相似文献
4.
Ee Taek Hwang Khizar Sheikh Katherine L. Orchard Daisuke Hojo Valentin Radu Chong‐Yong Lee Emma Ainsworth Colin Lockwood Manuela A. Gross Tadafumi Adschiri Erwin Reisner Julea N. Butt Lars J. C. Jeuken 《Advanced functional materials》2015,25(15):2308-2315
In nature, charge recombination in light‐harvesting reaction centers is minimized by efficient charge separation. Here, it is aimed to mimic this by coupling dye‐sensitized TiO2 nanocrystals to a decaheme protein, MtrC from Shewanella oneidensis MR‐1, where the 10 hemes of MtrC form a ≈7‐nm‐long molecular wire between the TiO2 and the underlying electrode. The system is assembled by forming a densely packed MtrC film on an ultra‐flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP). The step‐by‐step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz‐crystal microbalance with dissipation (QCM‐D), and atomic force microscopy (AFM). Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit. In other words, in these TiO2/MtrC hybrid photodiodes, MtrC traps the conduction‐band electrons from TiO2 before transferring them to the electrode, creating a photobioelectrochemical system in which a redox protein is used to mimic the efficient charge separation found in biological photosystems. 相似文献
5.
Vertical 2D MoO2/MoSe2 Core–Shell Nanosheet Arrays as High‐Performance Electrocatalysts for Hydrogen Evolution Reaction 下载免费PDF全文
Xiaoshuang Chen Guangbo Liu Wei Zheng Wei Feng Wenwu Cao Wenping Hu PingAn Hu 《Advanced functional materials》2016,26(46):8537-8544
Electrochemical water splitting is very attractive for green fuel energy production, but the development of active, stable, and earth‐abundant catalysts for the hydrogen evolution reaction (HER) remains a major challenge. Here, core–shell nanostructured architectures are used to design and fabricate efficient and stable HER catalysts from earth‐abundant components. Vertically oriented quasi‐2D core–shell MoO2/MoSe2 nanosheet arrays are grown onto insulating (SiO2/Si wafer) or conductive (carbon cloth) substrates. This core–shell nanostructure array architecture exhibits synergistic properties to create superior HER performance, where high density structural defects and disorders on the shell generated by a large crystalline mismatch of MoO2 and MoSe2 act as multiple active sites for HER, and the metallic MoO2 core facilitates charge transport for proton reduction while the vertical nanosheet arrays ensure fully exposed active sites toward electrolytes. As a HER catalyst, this electrode exhibits a low Tafel slope of 49.1 mV dec?1, a small onset potential of 63 mV, and an ultralow charge transfer resistance (Rct) of 16.6 Ω at an overpotential of 300 mV with a long cycling durability for up to 8 h. This work suggests that a quasi 2D core–shell nanostructure combined with a vertical array microstructure is a promising strategy for efficient water splitting electrocatalysts with scale‐up potential. 相似文献
6.
S. Zhou Y. Liu W. Qiu Y. Xu X. Huang Y. Li L. Jiang D. Zhu 《Advanced functional materials》2002,12(1):65-69
A novel asymmetrically substituted dicyano‐tri‐tert‐butylphthalocyanine ((CN)2BuPc) with rectifying behavior has been synthesized. The morphology and conductive properties of (CN)2BuPc Langmuir–Blodgett (LB) films on mica and highly ordered pyrolytic graphite (HOPG) substrates were studied by atomic force microscopy (AFM) and scanning tunneling microscopy (STM), in air at 22 °C. The average area of each (CN)2BuPc molecule obtained from the AFM topography in situ is ca. 73.6 Å2, which is in good agreement with the result of ca. 74 Å2 obtained from the π–A isotherm curve of a LB film. This indicates that the molecules are standing edge‐on, tilted by 38° against the surface normal of the substrate. The conductive properties for the 7‐layer LB films of (CN)2BuPc were studied by STM with a tungsten tip. The asymmetric I–V curve revealed a type of rectifying behavior for a negative and a positive bias. A feature model of the intramolecular and intermolecular charge transfer is presented. It not only interprets electron transfer from electron‐donor to electron‐acceptor molecules via a molecular “bridge”, but also the tunneling effect through intermolecular charge transfer. 相似文献
7.
Avalanche‐Discharge‐Induced Electrical Forming in Tantalum Oxide‐Based Metal–Insulator–Metal Structures 下载免费PDF全文
Katharina Skaja Christoph Bäumer Oliver Peters Stephan Menzel Marco Moors Hongchu Du Manuel Bornhöfft Christoph Schmitz Vitaliy Feyer Chun‐Lin Jia Claus Michael Schneider Joachim Mayer Rainer Waser Regina Dittmann 《Advanced functional materials》2015,25(46):7154-7162
Oxide‐based metal–insulator–metal structures are of special interest for future resistive random‐access memories. In such cells, redox processes on the nanoscale occur during resistive switching, which are initiated by the reversible movement of native donors, such as oxygen vacancies. The formation of these filaments is mainly attributed to an enhanced oxygen diffusion due to Joule heating in an electric field or due to electrical breakdown. Here, the development of a dendrite‐like structure, which is induced by an avalanche discharge between the top electrode and the Ta2O5‐x layer, is presented, which occurs instead of a local breakdown between top and bottom electrode. The dendrite‐like structure evolves primarily at structures with a pronounced interface adsorbate layer. Furthermore, local conductive atomic force microscopy reveals that the entire dendrite region becomes conductive. Via spectromicroscopy it is demonstrated that the subsequent switching is caused by a valence change between Ta4+ and Ta5+, which takes place over the entire former Pt/Ta2O5‐x interface of the dendrite‐like structure. 相似文献
8.
Carbon Nanotube‐Encapsulated Noble Metal Nanoparticle Hybrid as a Cathode Material for Li‐Oxygen Batteries 下载免费PDF全文
Xin Huang Hong Yu Huiteng Tan Jixin Zhu Wenyu Zhang Chengyuan Wang Jun Zhang Yuxi Wang Yunbo Lv Zhi Zeng Dayong Liu Jun Ding Qichun Zhang Madhavi Srinivasan Pulickel M. Ajayan Huey Hoon Hng Qingyu Yan 《Advanced functional materials》2014,24(41):6516-6523
Although Li‐oxygen batteries offer extremely high theoretical specific energy, their practical application still faces critical challenges. One of the main obstacles is the high charge overpotential caused by sluggish kinetics of charge transfer that is closely related to the morphology of discharge products and their distribution on the cathode. Here, a series of noble metal nanoparticles (Pd, Pt, Ru and Au) are encapsulated inside end‐opened carbon nanotubes (CNTs) by wet impregnation followed by thermal annealing. The resultant cathode materials exhibit a dramatic reduction of charge overpotentials compared to their counterparts with nanoparticles supported on CNT surface. Notably, the charge overpotential can be as low as 0.3 V when CNT‐encapsulated Pd nanoparticles are used on the cathode. The cathode also shows good stability during discharge–charge cycling. Density functional theory (DFT) calculations reveal that encapsulation of “guest” noble metal nanoparticles in “host” CNTs is able to strengthen the electron density on CNT surfaces, and to avoid the regional enrichment of electron density caused by the direct exposure of nanoparticles on CNT surface. These unique properties ensure the uniform coverage of Li2O2 nanocrystals on CNT surfaces instead of localized distribution of Li2O2 aggregation, thus providing efficient charge transfer for the decomposition of Li2O2. 相似文献
9.
Sven Herrmann Nihan Aydemir Florian Nägele Donato Fantauzzi Timo Jacob Jadranka Travas‐Sejdic Carsten Streb 《Advanced functional materials》2017,27(25)
High‐performance batteries and supercapacitors require the molecular‐level linkage of charge transport components and charge storage components. This study shows how redox‐tunable Lindqvist‐type molecular metal oxide anions [VnM 6–n O19](2+n )? (M = W(VI) or Mo(VI); n = 0, 1, 2) can be incorporated in cationic polypyrrole (PPy) conductive polymer films by means of electrochemical polymerization. Electron microscopy and (spectro‐)electrochemistry show that the electroactivity and morphology of the composites can be tuned by Lindqvist anion incorporation. Reductive electrochemical “activation” of the Lindqvist–PPy composites leads to significantly increased electrical capacitance (range: ≈25–38 F g?1, increase up to ≈25×), highlighting that this general synthetic route gives access to promising capacitive materials with suitable long‐term stability. Electrochemical, electron microscopic, and Raman spectroscopic analyses together with density functional theory (DFT) calculations provide molecular‐level insight into the effects of Lindqvist anion incorporation in PPy films and their role during reductive activation. The study therefore provides fundamental understanding of the principles governing the bottom‐up integration of molecular components into nanostructured composites for electrochemical energy storage. 相似文献
10.
Shuaipeng Ge Xinwei Guan Yutao Wang Chun‐Ho Lin Yimin Cui Yunxia Huang Xinran Zhang Ruoxuan Zhang Xiaoting Yang Tom Wu 《Advanced functional materials》2020,30(25)
3D organic–inorganic and all‐inorganic lead halide perovskites have been intensively pursued for resistive switching memories in recent years. Unfortunately, instability and lead toxicity are two foremost challenges for their large‐scale commercial applications. Dimensional reduction and composition engineering are effective means to overcome these challenges. Herein, low‐dimensional inorganic lead‐free Cs3Bi2I9 and CsBi3I10 perovskite‐like films are exploited for resistive switching memory applications. Both devices demonstrate stable switching with ultrahigh on/off ratios (≈106), ultralow operation voltages (as low as 0.12 V), and self‐compliance characteristics. 0D Cs3Bi2I9‐based device shows better retention time and larger reset voltage than the 2D CsBi3I10‐based device. Multilevel resistive switching behavior is also observed by modulating the current compliance, contributing to the device tunability. The resistive switching mechanism is hinged on the formation and rupture of conductive filaments of halide vacancies in the perovskite films, which is correlated with the formation of AgIx layers at the electrode/perovskite interface. This study enriches the library of switching materials with all‐inorganic lead‐free halide perovskites and offers new insights on tuning the operation of solution‐processed memory devices. 相似文献
11.
Nonvolatile Floating‐Gate Memories Based on Stacked Black Phosphorus–Boron Nitride–MoS2 Heterostructures 下载免费PDF全文
Dong Li Xiaojuan Wang Qichong Zhang Liping Zou Xiangfan Xu Zengxing Zhang 《Advanced functional materials》2015,25(47):7360-7365
Research on van der Waals heterostructures based on stacked 2D atomic crystals is intense due to their prominent properties and potential applications for flexible transparent electronics and optoelectronics. Here, nonvolatile memory devices based on floating‐gate field‐effect transistors that are stacked with 2D materials are reported, where few‐layer black phosphorus acts as channel layer, hexagonal boron nitride as tunnel barrier layer, and MoS2 as charge trapping layer. Because of the ambipolar behavior of black phosphorus, electrons and holes can be stored in the MoS2 charge trapping layer. The heterostructures exhibit remarkable erase/program ratio and endurance performance, and can be developed for high‐performance type‐switching memories and reconfigurable inverter logic circuits, indicating that it is promising for application in memory devices completely based on 2D atomic crystals. 相似文献
12.
Nanostructured Li2MnSiO4/C Cathodes with Hierarchical Macro‐/Mesoporosity for Lithium‐Ion Batteries 下载免费PDF全文
Li2MnSiO4/C nanocomposite with hierarchical macroporosity is prepared with poly(methyl methacrylate) (PMMA) colloidal crystals as a sacrificial hard‐template and water‐soluble phenol‐formaldehyde (PF) resin as the carbon source. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses confirm that the periodic macropores are ≈400 nm in diameter with 20–40 nm walls comprising Li2MnSiO4/C nanocrystals that produce additional large mesopores (< 30 nm) between the nanocrystals. The nanostructured Li2MnSiO4/C cathode exhibits a high reversible discharge capacity of 200 mAh g?1 at C/10 (16 mA g?1) rate at 1.5–4.8 V at 45 °C. Although the discharge capacity can be further increased on operating at 55 °C, the sample exhibits a relatively fast capacity fade at 55 °C, which can be partially solved by simply narrowing the voltage window to avoid side reactions of the electrolyte. The good performance of the Li2MnSiO4/C cathodes is attributed to the unique macro‐/mesostructure of the silicate coupled with uniform carbon coating. 相似文献
13.
A General Metal‐Organic Framework (MOF)‐Derived Selenidation Strategy for In Situ Carbon‐Encapsulated Metal Selenides as High‐Rate Anodes for Na‐Ion Batteries 下载免费PDF全文
Xijun Xu Jun Liu Jiangwen Liu Liuzhang Ouyang Renzong Hu Hui Wang Lichun Yang Min Zhu 《Advanced functional materials》2018,28(16)
On account of increasing demand for energy storage devices, sodium‐ion batteries (SIBs) with abundant reserve, low cost, and similar electrochemical properties have the potential to partly replace the commercial lithium‐ion batteries. In this study, a facile metal‐organic framework (MOF)‐derived selenidation strategy to synthesize in situ carbon‐encapsulated selenides as superior anode for SIBs is rationally designed. These selenides with particular micro‐ and nanostructured features deliver ultrastable cycling performance at high charge–discharge rate and demonstrate ultraexcellent rate capability. For example, the uniform peapod‐like Fe7Se8@C nanorods represent a high specific capacity of 218 mAh g?1 after 500 cycles at 3 A g?1 and the porous NiSe@C spheres display a high specific capacity of 160 mAh g?1 after 2000 cycles at 3 A g?1. The current simple MOF‐derived method could be a promising strategy for boosting the development of new functional inorganic materials for energy storage, catalysis, and sensors. 相似文献
14.
Nanostructured Si/Organic Heterojunction Solar Cells with High Open‐Circuit Voltage via Improving Junction Quality 下载免费PDF全文
Shan Wu Wei Cui Nabi Aghdassi Tao Song Steffen Duhm Shuit‐Tong Lee Baoquan Sun 《Advanced functional materials》2016,26(28):5035-5041
Nanostructured silicon (Si) can provide improved light harvest efficiencies in organic‐Si heterojunction solar cells due to its low light reflection ratio compared with planar one. However, the associated large surface/volume ratio of nanostructured Si suffers from serious surface recombination as well as poor adhesion with organics in organic‐Si heterojunction solar cells, which leads to an inferior open‐circuit voltage (Voc). Here, we develop a simple and effective method to suppress charge recombination as well as enhancing adhesion force between nanostructured Si and organics by incorporating a silane chemical, namely 3‐glycidoxypropyltrimethoxydsilane (GOPS). GOPS can chemically graft onto nanostructured Si and improve the aqueous organic wetting properties, suppressing surface charge recombination velocity dramatically. In addition, this chemically grafted layer can enhance adhesion force between organics and Si. In such a way, a record Voc of 640 mV associated with a power conversion efficiency of 14.1% is obtained for organic‐nanostructured Si heterojunction devices. These findings suggest a promising approach to low‐cost and simple fabrication for high‐performance organic‐Si solar cells. 相似文献
15.
Tao Chen Weihua Hu Junling Song Guan Hong Guai Chang Ming Li 《Advanced functional materials》2012,22(24):5245-5250
The microstructures of photo‐ and counter‐electrodes play critical roles in the performance of dye‐sensitized solar cells (DSSCs). In particular, various interfaces, such as fluorinated‐tin oxide (FTO)/TiO2, TiO2/TiO2, and TiO2/electrolyte, in DSSCs significantly affect the final power conversion efficiency (PCE). However, research has generally focused more on the design of various nanostructured semiconducting materials with emphasis on optimizing chemical or/and physical properties, and less on these interface functionalizations for performance improvement. This work explores a new application of graphene to modify the interface of FTO/TiO2 to suppress charge recombination. In combination with interfaces functionalization of TiO2/TiO2 for low charge‐transport resistance and high charge‐transfer rate, the final PCE of DSSC is remarkably improved from 5.80% to 8.13%, achieving the highest efficiency in comparison to reported graphene/TiO2‐based DSSCs. The method of using graphene to functionalize the surface of FTO substrate provides a better alternative method to the conventional pre‐treatment through hydrolyzing TiCl4 and an approach to reduce the adverse effect of microstructural defect of conducting glass substrate for electronic devices. 相似文献
16.
In this work, a full‐cell sodium‐ion battery (SIB) with a high specific energy approaching 300 Wh kg?1 is realized using a sodium vanadium fluorophosphate (Na3V2(PO4)2F3, NVPF) cathode and a tin phosphide (SnPx) anode, despite both electrode materials having greatly unbalanced specific capacities. The use of a cathode employing an areal loading more than eight times larger than that of the anode can be achieved by designing a nanostructured nanosized NVPF (n‐NVPF) cathode with well‐defined particle size, porosity, and conductivity. Furthermore, the high rate capability and high potential window of the full‐cell can be obtained by tuning the Sn/P ratio (4/3, 1/1, and 1/2) and the nanostructure of an SnPx/carbon composite anode. As a result, the full‐cell SIBs employing the nanostructured n‐NVPF cathode and the SnPx/carbon composite anode (Sn/P = 1/1) exhibit outstanding specific energy (≈280 Wh kg?1(cathode+anode)) and energy efficiency (≈78%); furthermore, the results are comparable to those of state‐of‐the‐art lithium‐ion batteries. 相似文献
17.
Xinyong Tao Jun Du Yong Sun Shulan Zhou Yang Xia Hui Huang Yongping Gan Wenkui Zhang Xiaodong Li 《Advanced functional materials》2013,23(37):4745-4751
The basic microstructure‐dependent charge storage mechanisms of nanostructured MnO2 are investigated via dynamic observation of the growth and in situ probing the mechanical properties by using in situ AFM in conjunction with in situ nanoindentation. The progressive nucleation followed by three‐dimensional growth yields pulsed current deposited porous nanostructured γ‐MnO2, which exhibits a high specific capacitance of 437 F/g and a remarkable cycling performance with >96% capacitance retention after 10 000 cycles. The proton intercalation induced expansion of MnO2 can be self‐accommodated by the localized compression and reduction of the porosity. More coincidentally, the proton intercalation induced softening is favorable for the elastic deformation of MnO2. This self‐adaptive capability of nanostructured MnO2 could generate high structural reliability during cycling. These discoveries offer important mechanistic insights for the design of advanced electrochemical capacitors. 相似文献
18.
2D Nanospace Confined Synthesis of Pseudocapacitance‐Dominated MoS2‐in‐Ti3C2 Superstructure for Ultrafast and Stable Li/Na‐Ion Batteries 下载免费PDF全文
Exploring a universal strategy to implement the precise control of 2D nanomaterials in size and layer number is a big challenge for achieving ultrafast and stable Li/Na‐ion batteries. Herein, the confined synthesis of 1–3 layered MoS2 nanocrystals into 2D Ti3C2 interlayer nanospace with the help of electrostatic attraction and subsequent cetyltrimethyl ammonium bromide (CTAB) directed growth is reported. The MoS2 nanocrystals are tightly anchored into the interlayer by 2D confinement effect and strong Mo? C covalent bond. Impressively, the disappearance of Li+ intercalated into MoS2 reduction peak is successfully observed for the first time in the experiment, showing in a typical surface‐controlled charge storage behavior. The pseudocapacitance‐dominated contribution guarantees a much faster and more stable Li/Na storage performance. As predicted, this electrode exhibits a very high Li+ storage capacity of 340 mAh g?1 even at 20 A g?1 and a long cycle life (>1000 times). It also shows an excellent Na+ storage capacity of 310 mAh g?1 at 1 A g?1 with a 1600 times high‐rate cycling. Such impressive confined synthesis strategy can be extended to the precise control of other 2D nanomaterials. 相似文献
19.
Meng He Peng Huang Chunlei Zhang Hengyao Hu Chenchen Bao Guo Gao Rong He Daxiang Cui 《Advanced functional materials》2011,21(23):4470-4477
A novel OA/ionic liquid two‐phase system combining the merits of thermal decomposition method, the IL‐based strategy, and the two‐phase approach is introduced to synthesize high‐quality lanthanide‐doped NaGdF4 upconversion nanocrystals with different crystal‐phases in OA‐phase and IL‐phase through a one‐step controllable reaction. Oil‐dispersible cubic‐phase NaGdF4:Yb, Er (Ho, Tm) nanocrystals with ultra‐small size (~5 nm) and monodispersity are obtained in the OA phase of the two‐phase system via an IL‐based reaction. More importantly, water‐soluble hexagonal‐phase NaGdF4:Yb, Er nanocrystals are obtained in the same system simply by adopting an extremely facile method to complete the dual phase‐transition (crystal‐phase transition and OA‐phase to IL‐phase transition) simultaneously. The synthesized lanthanide‐doped NaGdF4 upconversion nanocrystals are effective for dual‐mode UCL imaging and CT imaging in vivo. 相似文献
20.
Nanostructured Pseudocapacitors Based on Atomic Layer Deposition of V2O5 onto Conductive Nanocrystal‐based Mesoporous ITO Scaffolds 下载免费PDF全文
Iris E. Rauda Veronica Augustyn Laura C. Saldarriaga‐Lopez Laura T. Schelhas Gary W. Rubloff Bruce Dunn Sarah H. Tolbert 《Advanced functional materials》2014,24(42):6717-6728
Solution processing of colloidal nanocrystals into porous architectures using block co‐polymer templating offers a simple yet robust route to construct materials with open porosity and high surface area. These features, when realized in materials that show efficient redox activity and good conductivity, should be ideal for electrochemical energy storage because they allow for efficient electrolyte diffusion and ample surface and near‐surface redox reactions. Here, a route to synthesize nanoporous pseudocapacitors is presented using preformed ITO nanocrystals to make a conductive scaffold, coated with a conformal layer of vanadia deposited using atomic layer deposition (ALD). Two vanadia thicknesses are deposited, 2 and 7 nm, to examine the kinetics of Li+ diffusion into vanadia in a system where all other chemical and structural parameters are fixed. Porosity measurements show that the internal surface area of 2 nm vanadia samples is fully accessible; whereas for the 7 nm vanadia, there is some pore blockage that limits electrolyte diffusion. Despite this fact, composites with both thick and thin vanadia layers show high levels of pseudocapacitance, indicating fast diffusion of Li+ through even the 7 nm thick vanadia. This work thus sets a minimum accessible length‐scale of 7 nm for intercalation pseudocapacitance in orthorhombic V2O5. 相似文献