Here we demonstrate that the building blocks of semiconductor WO3 nanowires can be controllably soldered together via a novel nano-soldering technique of in situ SEM-FIB thermal soldering, in which the soldering temperature can be precisely retained in an optimal range to avoid strong thermal diffusion.

The assembly of aligned porous materials from simple building blocks is of widespread interest for engineering materials with enhanced and synergistic properties. To date, however, how to develop 3D heterojunction aerogels with aligned porosity based on 2D semiconductor materials and 1D conducting polymers for solar energy conversion in the visible and near-infrared (NIR) light region remains a significant challenge. Here a new class of gram-scale 3D aligned heterojunction aerogels of polypyrrole (PPy)/C3N4 nanosheets (NSs) were designed and synthesized by directional freezing of polypyrrole (PPy)/polyvinyl alcohol (PVA) and C3N4 NS aqueous suspension. The synthesis of aligned C3N4–PPy heterojunction aerogels can be achieved on a large scale. The formed aerogel expresses stable and uniform dispersion of the two building blocks, long-range channel aligned structures along the whole monolithic sample, and additional special complementary optical properties between PPy and C3N4 NSs. Based on the above unique structure and optical properties, this novel metal-free heterojunction aerogel exhibits excellent photocatalytic activity and long-term stability for direct arylation of heteroaromatics under visible and near infrared (NIR) light irradiation at room temperature, far exceeding those of the single- and two-component systems. Our work therefore not only provides a new approach to obtain aligned heterojunction aerogels based on metal free semiconductors but also paves a way to develop gram-scale aerogels as a new type of highly efficient visible and NIR light induced heterogeneous photocatalyst.

Low-dimensional spinel ferrites have recently attracted increasing attention because their tunable magnetic properties make them attractive candidates as spin-filtering tunnel barriers in spintronic devices and as magnetic components in artificial multiferroic heterostructures. Although we know that the distribution of cations (Fe3+ and Co2+) in a spinel structure governs its magnetic properties, their distribution in the so-called ideal inverse spinel structure of a ferrite, CoFe2O4, has not yet been imaged with sub-ångstrom resolution. In this work, we fill this gap in evidence by reporting a direct observation of the distribution of cations in an ideal inverse spinel structure of CoFe2O4 nanofibres using aberration-corrected transmission electron microscopy (TEM). The ordering of Co2+ and Fe3+ at the octahedral sites imaged along either [001], [011] or [−112] orientation was identified as 1 : 1, in accordance with the ideal inverse spinel structure. The saturation magnetisation calculated based on the crystal structure as determined from the TEM image is in good agreement with that measured experimentally on the spinel CoFe2O4 nanofibres, further confirming results from TEM.

We successfully synthesized blue, green, and red CsPbX3 QDs-codoped flexible films using a one-step electrospun strategy, followed by coating a strongly hydrophobic silicone resin on the surface of the films. The codoped flexible light-emitting films are resistant to water, thereby preventing anion exchange and significantly prolonging the lifetime of light emitters under ambient air conditions.

In this work, we accurately measure the electrical properties of individual Fe30Co61Cu9/Cu multilayered nanowires using nanomanipulators in in situ scanning electron microscopy to reveal that interfacial transition layers are influential in determining their transport behaviors. We investigate the morphology, crystal structure and chemistry of the Fe30Co61Cu9/Cu multilayered nanowires to characterize them at the nanoscale. We also compare the transport properties of these multilayered nanowires to those of individual pure Cu nanowires and to those of alloy Fe30Co61Cu9 nanowires. The multilayered nanowires with a 50 nm diameter had a remarkable resistivity of approximately 5.41 × 10−7 Ω m and a failure current density of 1.54 × 1011 A m−2. Detailed analysis of the electrical data reveals that interfacial transition layers influence the electrical properties of multilayered nanowires and are likely to have a strong impact on the life of nanodevices. This work contributes to a basic understanding of the electrical parameters of individual magnetic multilayered nanowires for their application as functional building blocks and interconnecting leads in nanodevices and nanoelectronics, and also provides a clear physical picture of a single multilayered nanowire which explains its electrical resistance and its source of giant magnetoresistance.

Individual semiconductor nanowires (NWs) TiO2 were successfully welded together using novel one-dimensional (1D) Au80Sn20 (mass ratio) nanosolders at the nano-scale for the first time. The nanosolders were electrodeposited into nanoporous templates to form a 1D structure, and their morphology, crystal structure, chemistry and elemental electronic states were systematically characterized. Individual Au80Sn20 nanowires were proved to consist of mixed crystal phases, including a Au5Sn phase with a trigonal structure, a AuSn phase with a hexagonal structure and a small SnO2 phase produced the by oxidation of the surface portion. Chemical analysis indicated that the composition was Au80Sn20. The testing of the welding capability by either in situ TEM or in situ SEM by nanomanipulators and infiltration experiment revealed a good wet ability and diffusion ability between the Au80Sn20 nanosolder and the TiO2 nanowire. It is believed that our study contributes to the field a special nanosolder for future nano-scale welding techniques, which also make the bonding of titanium-based semiconductor oxide nanomaterials at the nano-scale a reality.

One dimensional metal phase change nanomaterials provide a valuable research platform for understanding nanoscale phase transformation behavior and thermal properties, which have potential applications in identification systems such as information storage, barcoding, and detection. Tin(Sn)-based nanowires fabricated using a direct current electrodeposition technique into nanoporous templates are irradiated using electron beam (e-beam) in situ transmission electron microscopy. With the assistance of an oxide shell covering on the Sn-based nanowires, periodic and non-periodic multi-layered nanostructures are precisely sculpted and the reversibility between the original homogeneous alloy phase and the precipitated phases is controllable. The formation mechanism of the phase reversibility and sculpting process also works on other phase change materials, and this was proved using individual SnPb alloy nanowires as a test material. A single Sn–Ag alloy nanowire several microns in length was proved to be easily coded into dozens of morphology/phase statuses, which can be used to produce more than 1000 barcodes. This controllable, phase tunable strategy via selective e-beam irradiation engineering technique is believed to open up a way of sculpting an individual nanowire with various phase statuses and periodicities, which it may be possible to encode into a promising micro–nano identification system with the advantages of ultrahigh capacity, sustainable utilization and good stability.

Bamboo-like CoCu/Cu multilayer nanowires have been successfully fabricated into anodic aluminium oxide templates using an electrodeposition method, and their chemistry and crystal structure have been characterised at the nanoscale. Energy-dispersive X-ray analysis indicated that the chemical composition of the regular periodic CoCu/Cu nanowires was Co81Cu19/Cu. Diffraction analysis revealed that Cu layers and Co-rich layers exhibited polycrystalline fcc structures. A twin relationship of Cu layer {111} planes stacking on Co81Cu19 layer {111} planes was observed at the lattice-resolution level. The magnetic properties analysed by experimental and theoretical simulations showed that there was a transition from a curling rotation mode to coherent rotation mode in our Co81Cu19/Cu multilayer nanowires when the angle between external field and nanowire length axis increased from 0° to 90°. This study highlights the basic morphological, chemical, structural information and magnetic reversal mechanism of CoCu/Cu nanowires, which are critical for the applications of multilayer nanowires in nanoscale sensors and electronics.

CoFe2O4/graphene oxide hybrids have been successfully fabricated via a facile one-pot polyol route, followed by chemical conversion into FeCo/graphene hybrids under H2/NH3 atmosphere. These magnetic nanocrystals were uniformly decorated on the entire graphene nanosheets without aggregation. The morphology, chemical composition and crystal structure have been characterized in detail. In particular, FeCo/graphene hybrids show significant improvement in both permeability and permittivity due to the combination of the high magnetocrystalline anisotropy of metallic FeCo and high conductivity of light-weight graphene. This leads to remarkable enhancement in microwave absorption properties. The maximum reflection loss of FeCo/graphene hybrids reaches −40.2 dB at 8.9 GHz with a matching thickness of only 2.5 mm, and the absorption bandwidth with reflection loss exceeding −10 dB is in the 3.4–18 GHz range for the absorber thickness of only 1.5–5 mm. Moreover, the experimental relationship between matching thickness and frequency is found to obey the quarter-wavelength matching model, facilitating the design of FeCo/graphene hybrid film for practical application. The results suggest that the FeCo/graphene hybrids developed here can serve as an ideal candidate for the manufacture of light-weight and high-efficiency microwave-absorbing devices.

Hydrophobic single-crystalline La(OH)3 nanowires with tunable size have been successfully fabricated by a facile one-pot liquid–solid-solution (LSS) assisted hydrothermal method without any template and their morphology, chemistry and crystal structure were characterized on the nanoscale. Their average diameter and length strongly depend on the reaction time and the selection of solvents, which is due to the Ostwald ripening and oriented attachment mechanisms. XRD patterns and SAED analysis of numerous nanowires show that the La(OH)3 nanowires have a pure hexagonal structure without any impurities. TEM image and HAADF-STEM element mapping analysis indicate that the La(OH)3 nanowires have a uniform size, smooth surface and pure chemical phase. HRTEM images and CBED patterns of individual La(OH)3 nanowires suggest that each nanowire is single crystalline. Magnetic measurements reveal that the La(OH)3 nanowires show a d0 room-temperature ferromagnetic behavior. This study highlights the basic morphological, chemical and structural information for La(OH)3 nanowires, which is critical for their applications in nanodevices and nanoelectronics.

Well-defined bimagnetic h-Co decorated wurtzite h-CoO nanotetrapods with uniform size have been successfully fabricated by a one-pot thermal decomposition method for the first time, and their three-dimensional architecture, crystal structure, chemical phase and exchange bias effect are characterized at the nanoscale. It is found that individual bimagnetic h-Co/h-CoO nanotetrapods are made of a h-CoO nanotetrapod skeleton to which multiple nanocrystals of ferromagnetic metallic h-Co are directly attached. The chemical analysis shows that the mass ratio of h-CoO and h-Co is 65:35. The detailed investigations of the crystal structure reveal that both the h-CoO nanotetrapod skeleton and h-Co nanoparticles have hexagonal structure. The four pods of individual nanotetrapods are single crystals with the same [001] orientation along with their pod axes and grow together by twinning with (110) the twin interface and the 120° spatial boundary angle. The magnetic measurements reveal that the h-Co/h-CoO nanotetrapods have a surprisingly strong room temperature ferromagnetism and there exists a weak exchange coupling between the h-CoO nanotetrapod skeleton and the decorated h-Co tiny nanoparticles. It is believed that our new structural form of the bimagnetic h-Co/h-CoO nanotetrapods provides not only a smart functional 3D nanoarchitecture as building block in nanoelectronics and nanosensors, but also an ideal specimen for a further understanding of weak antiferromagnetic-ferromagnetic interaction.

•The 3D hierarchically porous MnO2 nanocomposite electrodes are fabricated.•This is one of the highest capacitance for MnO2 in IL electrolytes ever reported.•IL hybrid supercapacitor displays high voltage, specific energy and specific power.This work reports the synthesis of novel nanocomposite electrodes based on MnO2 nanosheets, Pt, Au, or Pd nanoparticles (NPs), exfoliated carbon nanotubes (CNTs), and Ni foam (NF) substrates. The MnO2–Pd–CNT–NF electrode in 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIM-PF6)/N, N-dimethylformamide (DMF) electrolyte exhibits a high specific capacitance of 559.1 F/g based on MnO2 with a wide potential window (2.1 V). To the best of our knowledge, this is one of the highest capacitance for MnO2 in ionic liquid (IL) electrolytes ever reported. The IL hybrid supercapacitors are assembled using MnO2–Pd–CNTs–NF positive electrode, activated carbon (AC) negative electrode, and BMIM-PF6/DMF electrolyte displaying high operating voltage (3 V), high energy density (78.4 Wh/kg) and high power density (12.7 kW/kg). The superior performances of the MnO2 IL hybrid supercapacitors suggest their potential application for the future generation of electrochemical power sources.

NiFe2O4 multi-particle-chain nanofibres have been successfully fabricated using electrospinning followed by calcination, and their morphology, chemistry and crystal structure were characterized at the nanoscale. Individual NiFe2O4 nanofibres were found to consist of many nanocrystallites stacked along the nanofibre axis. Chemical analysis shows that the atomic ratio of Ni:Fe is 1:2, indicating that the composition was NiFe2O4. The crystal structure of individual NiFe2O4 multi-particle-chain nanofibres proved to be polycrystalline with a face centered cubic (fcc) structure. The nanocrystallites in the nanofibres were revealed to have a single-crystal structure with random crystallographic orientations. The magnetic measurements reveal that the NiFe2O4 multi-particle-chain nanofibres have a coercivity force of 166 Oe. A “chain of sheets” micromagentism model was proposed to interpret the observed magnetic behaviour of the NiFe2O4 multi-particle-chain nanofibres. Simulation studies of the coercivity are in good agreement with the experimental results at room temperature. It is believed that this work will significantly expand the use and application of these compounds in the field of biomagnetic nano-devices and improve understanding of the magnetic origin of spinel ferrites.

BaFe12O19 single-particle-chain nanofibers have been successfully prepared by an electrospinning method and calcination process, and their morphology, chemistry, and crystal structure have been characterized at the nanoscale. It is found that individual BaFe12O19 nanofibers consist of single nanoparticles which are found to stack along the nanofiber axis. The chemical analysis shows that the atomic ratio of Ba/Fe is 1:12, suggesting a BaFe12O19 composition. The crystal structure of the BaFe12O19 single-particle-chain nanofibers is proved to be M-type hexagonal. The single crystallites on each BaFe12O19 single-particle-chain nanofibers have random orientations. A formation mechanism is proposed based on thermogravimetry/differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and transmission electron microscopy (TEM) at six temperatures, 250, 400, 500, 600, 650, and 800 °C. The magnetic measurement of the BaFe12O19 single-particle-chain nanofibers reveals that the coercivity reaches a maximum of 5943 Oe and the saturated magnetization is 71.5 emu/g at room temperature. Theoretical analysis at the micromagnetism level is adapted to describe the magnetic behavior of the BaFe12O19 single-particle-chain nanofibers.Keywords: BaFe12O19; CBED; EDX elemental mapping; electrospinning; formation principle; high saturation magnetization; magnetic reversal mechanism; single-particle-chain nanofibers

This study presents a comprehensively and systematically structural, chemical and magnetic characterization of ~9.5 nm virtually monodispersed nickel ferrite (NiFe2O4) nanoparticles prepared using a modified liquid–solid-solution (LSS) assisted hydrothermal method. Lattice-resolution scanning transmission electron microscope (STEM) and converged beam electron diffraction pattern (CBED) techniques are adapted to characterize the detailed spatial morphology and crystal structure of individual NiFe2O4 particles at nano scale for the first time. It is found that each NiFe2O4 nanoparticle is single crystal with an fcc structure. The morphology investigation reveals that the prepared NiFe2O4 nanoparticles of which the surfaces are decorated by oleic acid are dispersed individually in hexane. The chemical composition of nickel ferrite nanoparticles is measured to be 1:2 atomic ratio of Ni:Fe, indicating a pure NiFe2O4 composition. Magnetic measurements reveal that the as-synthesized nanocrystals displayed superparamagnetic behavior at room temperature and were ferromagnetic at 10 K. The nanoscale characterization and magnetic investigation of monodispersed NiFe2O4 nanoparticles should be significant for its potential applications in the field of biomedicine and magnetic fluid using them as magnetic materials.

In this work, we accurately measure the electrical properties of individual Fe30Co61Cu9/Cu multilayered nanowires using nanomanipulators in in situ scanning electron microscopy to reveal that interfacial transition layers are influential in determining their transport behaviors. We investigate the morphology, crystal structure and chemistry of the Fe30Co61Cu9/Cu multilayered nanowires to characterize them at the nanoscale. We also compare the transport properties of these multilayered nanowires to those of individual pure Cu nanowires and to those of alloy Fe30Co61Cu9 nanowires. The multilayered nanowires with a 50 nm diameter had a remarkable resistivity of approximately 5.41 × 10−7 Ω m and a failure current density of 1.54 × 1011 A m−2. Detailed analysis of the electrical data reveals that interfacial transition layers influence the electrical properties of multilayered nanowires and are likely to have a strong impact on the life of nanodevices. This work contributes to a basic understanding of the electrical parameters of individual magnetic multilayered nanowires for their application as functional building blocks and interconnecting leads in nanodevices and nanoelectronics, and also provides a clear physical picture of a single multilayered nanowire which explains its electrical resistance and its source of giant magnetoresistance.

Individual semiconductor nanowires (NWs) TiO2 were successfully welded together using novel one-dimensional (1D) Au80Sn20 (mass ratio) nanosolders at the nano-scale for the first time. The nanosolders were electrodeposited into nanoporous templates to form a 1D structure, and their morphology, crystal structure, chemistry and elemental electronic states were systematically characterized. Individual Au80Sn20 nanowires were proved to consist of mixed crystal phases, including a Au5Sn phase with a trigonal structure, a AuSn phase with a hexagonal structure and a small SnO2 phase produced the by oxidation of the surface portion. Chemical analysis indicated that the composition was Au80Sn20. The testing of the welding capability by either in situ TEM or in situ SEM by nanomanipulators and infiltration experiment revealed a good wet ability and diffusion ability between the Au80Sn20 nanosolder and the TiO2 nanowire. It is believed that our study contributes to the field a special nanosolder for future nano-scale welding techniques, which also make the bonding of titanium-based semiconductor oxide nanomaterials at the nano-scale a reality.

CoFe2O4/graphene oxide hybrids have been successfully fabricated via a facile one-pot polyol route, followed by chemical conversion into FeCo/graphene hybrids under H2/NH3 atmosphere. These magnetic nanocrystals were uniformly decorated on the entire graphene nanosheets without aggregation. The morphology, chemical composition and crystal structure have been characterized in detail. In particular, FeCo/graphene hybrids show significant improvement in both permeability and permittivity due to the combination of the high magnetocrystalline anisotropy of metallic FeCo and high conductivity of light-weight graphene. This leads to remarkable enhancement in microwave absorption properties. The maximum reflection loss of FeCo/graphene hybrids reaches −40.2 dB at 8.9 GHz with a matching thickness of only 2.5 mm, and the absorption bandwidth with reflection loss exceeding −10 dB is in the 3.4–18 GHz range for the absorber thickness of only 1.5–5 mm. Moreover, the experimental relationship between matching thickness and frequency is found to obey the quarter-wavelength matching model, facilitating the design of FeCo/graphene hybrid film for practical application. The results suggest that the FeCo/graphene hybrids developed here can serve as an ideal candidate for the manufacture of light-weight and high-efficiency microwave-absorbing devices.

One dimensional metal phase change nanomaterials provide a valuable research platform for understanding nanoscale phase transformation behavior and thermal properties, which have potential applications in identification systems such as information storage, barcoding, and detection. Tin(Sn)-based nanowires fabricated using a direct current electrodeposition technique into nanoporous templates are irradiated using electron beam (e-beam) in situ transmission electron microscopy. With the assistance of an oxide shell covering on the Sn-based nanowires, periodic and non-periodic multi-layered nanostructures are precisely sculpted and the reversibility between the original homogeneous alloy phase and the precipitated phases is controllable. The formation mechanism of the phase reversibility and sculpting process also works on other phase change materials, and this was proved using individual SnPb alloy nanowires as a test material. A single Sn–Ag alloy nanowire several microns in length was proved to be easily coded into dozens of morphology/phase statuses, which can be used to produce more than 1000 barcodes. This controllable, phase tunable strategy via selective e-beam irradiation engineering technique is believed to open up a way of sculpting an individual nanowire with various phase statuses and periodicities, which it may be possible to encode into a promising micro–nano identification system with the advantages of ultrahigh capacity, sustainable utilization and good stability.

We successfully synthesized blue, green, and red CsPbX3 QDs-codoped flexible films using a one-step electrospun strategy, followed by coating a strongly hydrophobic silicone resin on the surface of the films. The codoped flexible light-emitting films are resistant to water, thereby preventing anion exchange and significantly prolonging the lifetime of light emitters under ambient air conditions.

Bamboo-like CoCu/Cu multilayer nanowires have been successfully fabricated into anodic aluminium oxide templates using an electrodeposition method, and their chemistry and crystal structure have been characterised at the nanoscale. Energy-dispersive X-ray analysis indicated that the chemical composition of the regular periodic CoCu/Cu nanowires was Co81Cu19/Cu. Diffraction analysis revealed that Cu layers and Co-rich layers exhibited polycrystalline fcc structures. A twin relationship of Cu layer {111} planes stacking on Co81Cu19 layer {111} planes was observed at the lattice-resolution level. The magnetic properties analysed by experimental and theoretical simulations showed that there was a transition from a curling rotation mode to coherent rotation mode in our Co81Cu19/Cu multilayer nanowires when the angle between external field and nanowire length axis increased from 0° to 90°. This study highlights the basic morphological, chemical, structural information and magnetic reversal mechanism of CoCu/Cu nanowires, which are critical for the applications of multilayer nanowires in nanoscale sensors and electronics.