We demonstrate an easy and scalable low-temperature process to convert porous ternary complex metal oxide nanoparticles from solution-synthesized core/shell metal oxide nanoparticles by thermal annealing. The final products demonstrate superior electrochemical properties with a large capacity and high stability during fast charging/discharging cycles for potential applications as advanced lithium-ion battery (LIB) electrode materials. In addition, a new breakdown mechanism was observed on these novel electrode materials.
Yolk/shell (Y–S) hybrid nanoarchitectures, owing to the interior voids created for individualized catalyst applications, have emerged as new candidates for effectively isolating catalytic species. However, the well-defined hollow interiors with flexible core and shell compositions—such as noble-metal cores, metal-oxide cores, and widespread semiconductor shells—and a flexible anisotropic shape are far from the requirements. In particular, the introduction of catalytic noble metals or metal-oxide nanocrystals (NCs) with isotropic or anisotropic shapes into various hollow semiconductor structures with well-defined morphologies has been rarely reported but is urgently needed. Herein, we propose a strategy involving the careful sulfuration of as-prepared cavity-free core/shell NCs or metal-oxide NCs followed by phosphine-initialized cation-exchange reactions for preparing metal@semiconductor and metal oxide@semiconductor (II-VI) Y–S NCs. The geometry, size, and conformations of the core and shell are fully and independently considered. New and unprecendented metal@semiconductor and metal oxide@semiconductor (II-VI) Y–S NCs are prepared via widespread phosphine-initialized cation-exchange reactions.
A thermal emitter composed of a frequency-selective surface metamaterial layer and a hexagonal boron nitride-encapsulated graphene filament is demonstrated. The broadband thermal emission of the metamaterial (consisting of ring resonators) was tailored into two discrete bands, and the measured reflection and emission spectra agreed well with the simulation results. The high modulation frequencies that can be obtained in these devices, coupled with their operation in air, confirm their feasibility for use in applications such as gas sensing.
Identification of atomic disorders and their subsequent control has proven to be a key issue in predicting, understanding, and enhancing the properties of newly emerging topological insulator materials. Here, we demonstrate direct evidence of the cation antisites in single-crystal SnBi2Te4 nanoplates grown by chemical vapor deposition, through a combination of sub-ångström-resolution imaging, quantitative image simulations, and density functional theory calculations. The results of these combined techniques revealed a recognizable amount of cation antisites between Bi and Sn, and energetic calculations revealed that such cation antisites have a low formation energy. The impact of the cation antisites was also investigated by electronic structure calculations together with transport measurement. The topological surface properties of the nanoplates were further probed by angle-dependent magnetotransport, and from the results, we observed a two-dimensional weak antilocalization effect associated with surface carriers. Our approach provides a pathway to identify the antisite defects in ternary chalcogenides and the application potential of SnBi2Te4 nanostructures in next-generation electronic and spintronic devices.
This paper offers a comprehensive overview on the role of nanostructures in the development of advanced anode materials for application in both lithium and sodium-ion batteries. In particular, this review highlights the differences between the two chemistries, the critical effect of nanosize on the electrode performance, as well as the routes to exploit the inherent potential of nanostructures to achieve high specific energy at the anode, enhance the rate capability, and obtain a long cycle life. Furthermore, it gives an overview of nanostructured sodium- and lithium-based anode materials, and presents a critical analysis of the advantages and issues associated with the use of nanotechnology.
Mesoporous Au films consisting of a network of interconnected Au ligaments around ultra-large pores were found to exhibit a promising electrocatalytic activity towards sluggish reactions. Mesoporous Au films with pore sizes up to 25 nm were successfully fabricated using a polymeric micelle approach. A superior catalytic activity of the mesoporous Au films towards methanol oxidation was confirmed, which was thoroughly analyzed and compared with that of other Au materials. An intrinsic investigation on the high catalytic activity revealed that the superior performance of the as-prepared mesoporous Au film was related to its unique atomic structures around the mesopores with well-crystallized facets and several step/kink sites on the Au surfaces. These findings showcase a strategic and feasible design for preparing highly active Au-based catalysts that could be used as promising candidates in electrocatalytic applications.
Materials with emission over the whole visible range (400–800 nm) have been obtained through incorporating single-colored CdTe nanocrystals (NCs) into a poly(p-phenylene vinylene) (PPV) precursor [the sulfonium polyelectrolyte precursor of PPV]. Firstly, the quantum yield (QY) of the PPV precursor was improved to ～50% via heat treatment of a mixed solution of the PPV precursor and poly(vinyl alcohol) (PVA) at 100 °C for 3 min. Then, single-colored CdTe NCs were incorporated into the mixed solution. The introduction of the PVA was necessary to reduce the electrostatic interaction between the PPV precursor and CdTe NCs, which improved their compatibility. The reduced electrostatic interaction eliminated Förster resonance energy transfer (FRET) processes between NCs, as well as between NCs and the PPV precursor, which allowed the functional integration of the polymer and NCs. Consequently, polymer/NC composites with almost any Commission Internationale de L’Eclairage (CIE) coordinates can be achieved by simply changing the size and amount of the NCs. In particular, when the emission wavelength of the CdTe NCs was 559 nm, a pure white-light emitting material with CIE coordinates (0.337, 0.332) was obtained.
In this paper, we demonstrate that for colloidal CdSe/CdS nanoplatelets, a rectangular shape induces emission asymmetry, in terms of both polarization and emission patterns. Polarimetry and emission pattern analyses are combined to provide information on the orientation of the transition dipoles involved in the nanoplatelet emission. It is shown that for rectangular nanoplatelets, the emission is polarized and the emission patterns are anisotropic, whereas they remain nonpolarized and isotropic for square nanoplatelets. This can be appropriately described by the dielectric antenna effect induced by the elongated shape of the rectangular platelet.
Bismuth telluride (Bi2Te3) is one of the most important commercial thermoelectric materials. In recent years, the discovery of topologically protected surface states in Bi chalcogenides has paved the way for their application in nanoelectronics. Determination of the fracture toughness plays a crucial role for the potential application of topological insulators in flexible electronics and nanoelectromechanical devices. Using depth-sensing nanoindentation tests, we investigated for the first time the fracture toughness of bulk single crystals of Bi2Te3 topological insulators, grown using the Bridgman-Stockbarger method. Our results highlight one of the possible pitfalls of the technology based on topological insulators.
In this study, leaf-like one-dimensional InAs nanostructures were grown by the metal–organic chemical vapor deposition method. Detailed structural characterization suggests that the nanoleaves contain relatively low-energy {122} or {133} mirror twins acting as their midribs and narrow sections connecting the nanoleaves and their underlying bases as petioles. Importantly, the mirror twins lead to identical lateral growth of the twinned structures in terms of crystallography and polarity, which is essential for the formation of lateral symmetrical nanoleaves. It has been found that the formation of nanoleaves is driven by catalyst energy minimization. This study provides a biomimic of leaf found in nature by fabricating a semiconductor nanoleaf.
The recent development of synthesis processes for three-dimensional (3D) graphene-based structures has tended to focus on continuous improvement of porous nanostructures, doping modification during thin-film fabrication, and mechanisms for building 3D architectures. Here, we synthesized novel snowflake-like Si-O/Si-C nanostructures on 3D graphene/Cu foam by one-step low-pressure chemical vapor deposition (CVD). Through systematic micromorphological characterization, it was determined that the formation mechanism of the nanostructures involved the melting of the Cu foam surface and the subsequent condensation of the resulting vapor, 3D growth of graphene through catalysis in the presence of Cu, and finally, nucleation of the Si-O/Si-C nanostructure in the carbon-rich atmosphere. Thus, by tuning the growth temperature and duration, it should be possible to control the nucleation and evolution of such snowflake-like nanostructures with precision. Electrochemical measurements indicated that the snowflake-like nanostructures showed excellent performance as a material for energy storage. The highest specific capacitance of the Si-O/Si-C nanostructures was ～963.2 mF/cm2 at a scan rate of 1 mV/s. Further, even after 20,000 sequential cycles, the electrode retained 94.4% of its capacitance.
Controlling the chemistry at the interface of nanocrystalline solids has been a challenge and an important goal to realize desired properties. Integrating two different types of materials has the potential to yield new functions resulting from cooperative effects between the two constituents. Metal–organic frameworks (MOFs) are unique in that they are constructed by linking inorganic units with organic linkers where the building units can be varied nearly at will. This flexibility has made MOFs ideal materials for the design of functional entities at interfaces and hence allowing control of properties. This review highlights the strategies employed to access synergistic functionality at the interface of nanocrystalline MOFs (nMOFs) and inorganic nanocrystals (NCs).
A triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG) were hybridized to harvest the human mechanical energy. By an effective conjunction of triboelectrification and electromagnetic induction, the hybridized nanogenerator with a radius of 2 cm and height of 1.2 cm could charge a 1,000 μF capacitor to 5.09 V after 100 cycles of vibration. This mini-sized hybrid nanogenerator could then be embedded in shoes to serve as an energy cell. Typical outdoor applications—including driving with a Global Positioning System (GPS) device, charging a Li-ion battery and a cell phone—were successfully demonstrated, suggesting its potential application in smart wearable electronics and future suits of soldiers.
Sodium-ion batteries have received remarkable attention as next-generation high-performance electrochemical energy storage devices because of their cost effectiveness and the broad geographical distribution of sodium. As a critical component of sodium-ion batteries, anode materials, especially nanostructured anodes, have a significant effect on the electrochemical performance of sodium-ion batteries. Recent research indicates that phosphorus and metal phosphides show great promise as anode candidates for sodium-ion batteries because of their low cost and relatively high theoretical gravimetric and volumetric specific capacities. In this review, we systematically summarize recent research progress on state-of-the-art nanostructured phosphorus and phosphides, including the synthetic strategies, Na-storage mechanisms, and the relationship between the nanostructure and electrochemical performance. Moreover, we present an overview of future challenges and opportunities based on current developments.
Germanium-based oxide has been found to be a promising high-capacity anode material for lithium-ion batteries (LIBs). However, it exhibits poor electrochemical performance because of the drastic volume change during cycling. Herein, we designed porous Ge-Fe bimetal oxide nanowires (Ge-Fe-Ox-700 NWs) by a large-scale and facile solvothermal reaction. When used as the anode material for LIBs, these Ge-Fe-Ox-700 NWs exhibited superior electrochemical performance (～ 1,120 mAh·g?1 at a current density of 100 mA·g?1) and good cycling performance (～ 750 mAh·g?1 after 50 cycles at a current density of 100 mA·g?1). The improved performance is due to the small NW diameter, which allows for better accommodation of the drastic volume changes and zero-dimensional nanoparticles, which shorten the diffusion length of ions and electrons.
Solid polymer electrolytes are light-weight, flexible, and non-flammable and provide a feasible solution to the safety issues facing lithium-ion batteries through the replacement of organic liquid electrolytes. Substantial research efforts have been devoted to achieving the next generation of solid-state polymer lithium batteries. Herein, we provide a review of the development of solid polymer electrolytes and provide comprehensive insights into emerging developments. In particular, we discuss the different molecular structures of the solid polymer matrices, including polyether, polyester, polyacrylonitrile, and polysiloxane, and their interfacial compatibility with lithium, as well as the factors that govern the properties of the polymer electrolytes. The discussion aims to give perspective to allow the strategic design of state-of-the-art solid polymer electrolytes, and we hope it will provide clear guidance for the exploration of high-performance lithium batteries.
Understanding how small molecules interface with amyloid fibrils at the nanoscale is of importance for developing therapeutic treatments against amyloid-based diseases. Here, we show for the first time that human islet amyloid polypeptides (IAPP) in the fibrillar form are polymorphic, ambidextrous, and possess multiple periodicities. Upon interfacing with the small molecule epigallocatechin gallate (EGCG), IAPP aggregation was rendered off-pathway and assumed a form with soft and disordered clusters, while mature IAPP fibrils displayed kinks and branching but conserved the twisted fibril morphology. These nanoscale phenomena resulted from competitive interactions between EGCG and the IAPP amyloidogenic region, as well as end capping of the fibrils by the small molecule. This information is crucial in delineating IAPP toxicity implicated in type 2 diabetes and for developing new inhibitors against amyloidogenesis.
The wetting properties of an electrode surface are of significant importance to the performance of electrochemical devices because electron transfer occurs at the electrode/electrolyte interface. Described in this paper is a low-cost metal oxide electrocatalyst (CuO)-based high-performance sensing device using an enzyme electrode with a solid/liquid/air triphase interface in which the oxygen level is constant and sufficiently high. We apply the sensing device to detect glucose, a model test analyte, and demonstrate a linear dynamic range up to 50 mM, which is about 25 times higher than that obtained using a traditional enzyme electrode with a solid/liquid diphase interface. Moreover, we show that sensing devices based on a triphase assaying interface are insensitive to the significant oxygen level fluctuation in the analyte solution.
Understanding charge transfer processes between graphene and functional materials is crucial from the perspectives of fundamental sciences and potential applications, including electronic devices, photonic devices, and sensors. In this study, we present the charge transfer behavior of graphene and amine-rich polyethyleneimine (PEI) upon CO2 exposure, which was significantly improved after introduction of hygroscopic polyethylene glycol (PEG) in humid air. By blending PEI and PEG, the number of protonated amine groups in PEI was remarkably increased in the presence of water molecules, leading to a strong electron doping effect on graphene. The presence of CO2 gas resulted in a large change in the resistance of PEI/PEG-co-functionalized graphene because of the dramatic reduction of said doping effect, reaching a maximum sensitivity of 32% at 5,000 ppm CO2 and an applied bias of 0.1 V in air with 60% relative humidity at room temperature. This charge transfer correlation will facilitate the development of portable graphene-based sensors for real-time gas detection and the extension of the applications of graphene-based electronic and photonic devices.
Transparent electrodes based on copper nanowires (Cu NWs) have attracted significant attention owing to their advantages including high optical transmittance, good conductivity, and excellent mechanical flexibility. However, low-cost, high-performance, and environmental friendly solar cells with all-Cu NW electrodes have not been realized until now. Herein, top and bottom transparent electrodes based on Cu NWs with low surface roughness and homogeneous conductivity are fabricated. Then, semi-transparent polymer solar cells (PSCs) with the inverted structure of polyacrylate/Cu NWs/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (PH1000)/Y-TiO2/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid 3,4,5-tris(octyloxy)benzyl/PEDOT:PSS (4083)/Cu NWs/polyimide/polydimethylsiloxane are constructed; these could absorb light from both sides with a power conversion efficiency reaching 1.97% and 1.85%. Furthermore, the PSCs show an average transmittance of 42% in the visible region, which renders them suitable for some specialized applications such as power-generating windows and building-integrated photovoltaics. The indium tin oxide (ITO)- and noble metal-free PSCs could pave new pathways for fabricating cost-effective semi-transparent PSCs.
