Graphene Oxide Glue-Electrode for Fabrication of Vertical, Elastic, Conductive Columns

Graphene has a planar atomic structure with high flexibility and might be used as ultrathin conductive glues or adhesion layers in electronics and other applications. Here, we show that graphene oxide (GO) sheets condensed from solution can act as a pure, thin-layer, nonpenetrating glue for fabrication of vertical architectures anchored on rigid and flexible substrates. Carbon nanotube (CNT) sponges are used as a porous template to make polymer-reinforced composite columns, to achieve both high conductivity and elastic behavior. These vertical columns are fixed on a substrate by reduced GO sheets as an electrode and exhibit reversible resistance change under large-strain compression for many cycles. Similar to the CNT gecko feet, we disclose high adhesion forces at the CNT-GO and GO-SiO₂ interfaces by mechanical tests and theoretical calculation. Three-dimensional CNT, graphene, and nanowire networks with our GO glue-electrodes have potential applications as energy storage electrodes, flexible sensors, functional composites, and vertical interconnects

Highly Porous Core–Shell Structured Graphene-Chitosan Beads

Graphene oxide (GO) sheets have been assembled into various three-dimensional porous structures and composites, with potential applications in energy and environmental areas. Here, we show the combination of GO and chitosan (CTS) into inorganic–organic heterocomposites as ∼3 mm diameter core–shell beads with controlled microstructure. The spherical GO-CTS beads, made by a two-step freeze-casting method, consist of a GO core wrapped by a CTS shell with abrupt interface; both parts have high porosities (94–96%) and mesopores volume (0.246 cm³/g) yet with different pore morphologies. Incorporation of a GO core into the CTS beads significantly improved the methyl orange adsorption capacity (353 mg/g at 318 K) compared with pure CTS beads. Key factors such as the pH value, adsorbent dosage, concentration, time, and temperature have been studied in detail, whereas adsorption isotherm and kinetic studies reveal a Langmuir model following the pseudo-second order

Soluble Polymer-Based, Blown Bubble Assembly of Single- and Double-Layer Nanowires with Shape Control

We present here an efficient blown bubble method for large-scale assembly of semiconducting nanowires, with simultaneous control on the material shape. As-synthesized Te nanowires in powder form are dispersed in a poly­methyl­methacrylate (PMMA) solution, assembled in a large size bubble blown from the solution, and then transferred (repeatedly) to arbitrary substrates. By this way, we have obtained single-layer (aligned) and double-layer (crossed) Te nanowires as well as buckled Te nanosprings which are converted from initially straight nanowires <i>in situ</i> during bubble blowing. The PMMA bubble film can be removed by direct dissolution in acetone to expose nanostructures with clean surface while maintaining original configuration. After matrix removal, these clean nanowire and nanospring arrays can be fabricated into functional nanoelectronic devices such as photodetectors and gas sensors with high performance

Blown-Bubble Assembly and in Situ Fabrication of Sausage-like Graphene Nanotubes Containing Copper Nanoblocks

We use a blown-bubble method to assemble Cu nanowires and in situ fabricate graphene-based one-dimensional heterostructures, including versatile sausage-like configurations consisting of multilayer graphene nanotubes (GNTs) filled by single or periodically arranged Cu nanoblocks (CuNBs). This is done by first assembling Cu nanowires among a polymer-based blown-bubble film (BBF) and then growing graphene onto the nanowire substrate using the polymer matrix as a solid carbon source by chemical-vapor deposition. The formation of sausage-like GNT@CuNB nanostructures is due to the partial melting and breaking of embedded Cu nanowires during graphene growth, which is uniquely related to our BBF process. We show that the GNT skin significantly slows the oxidation process of CuNBs compared with that of bare Cu nanowires, and the presence of stuffed CuNBs also reduces the linear resistance along the GNTs. The large-scale assembled graphene-based heterostructures achieved by our BBF method may have potential applications in heterojunction electronic devices and high-stability transparent conductive electrodes

Comparison of Nanocarbon–Silicon Solar Cells with Nanotube–Si or Graphene–Si Contact

Nanocarbon structures such as carbon nanotubes (CNTs) and graphene (G) have been combined with crystalline silicon wafers to fabricate nanocarbon–Si solar cells. Here, we show that the contact between the nanocarbon and Si plays an important role in the solar cell performance. An asymmetrically configured CNT–G composite film was used to create either CNT–Si dominating or G–Si dominating junctions, resulting in obviously different solar cell behavior in pristine state. Typically, solar cells with direct G–Si contacts (versus CNT–Si) exhibit better characteristics due to improved junction quality and larger contact area. On the basis of the composite film, the obtained CNT–G–Si solar cells reach power conversion efficiencies of 14.88% under air mass 1.5, 88 mW/cm² illumination through established techniques such as acid doping and colloidal antireflection. Engineering the nanocarbon–Si contact is therefore a possible route for further improving the performance of this type of solar cells

Synergy of a Stabilized Antiferroelectric Phase and Domain Engineering Boosting the Energy Storage Performance of NaNbO₃‑Based Relaxor Antiferroelectric Ceramics

Relaxor antiferroelectric (AFE) ceramic capacitors have drawn growing attention in future advanced pulsed power devices for their superior energy storage performance. However, state of the art dielectric materials are restricted by desirable comprehensive energy-storage features, which have become a longstanding hurdle for actual capacitor applications. Here, we report that a large energy density Wrec of 5.52 J/cm3, high efficiency η of 83.3% at 560 kV/cm, high power density PD of 114.8 MW/cm3, ultrafast discharge rate t0.9 of 45 ns, and remarkable stability against temperature (30–140 °C)/frequency (5–200 Hz)/cycles (1–105) are simultaneously achieved in 0.7 NaNbO3-0.3 CaTiO3 relaxor AFE ceramics via the synergy of stabilized AFE R phase and domain engineering in combination with breakdown strength enhancement. The structural origin for these achievements is disclosed by probing the in situ microstructure evolution by means of the first-order reversal curve method, piezoelectric force microscopy, and Raman spectroscopy. The highly dynamic polar nanoregions and stabilized AFE R phase synergistically generate a linear-like and highly stable polarization field response over a wide temperature and field scope with concurrently improved energy density and efficiency. This work offers a new solution for designing high-performance next-generation pulsed power capacitors

Highly Stable Carbon Nanotube/Polyaniline Porous Network for Multifunctional Applications

Three-dimensional carbon nanotube (CNT) networks with high porosity and electrical conductivity have many potential applications in energy and environmental areas, but the network structure is not very stable due to weak inter-CNT interactions. Here, we coat a thin polyaniline (PANI) layer on as-synthesized CNT sponge to obtain a mechanically and electrically stable network, and enable multifunctional applications. The resulting CNT/PANI network serves as stable strain sensors, highly compressible supercapacitor electrode with enhanced volume-normalized capacitance (632 F/cm³), and reinforced nanocomposites with the PANI as intermediate layer between the CNT fillers and polymeric matrix. Our results provide a simple and controllable method for achieving high-stability porous networks composed of CNTs, graphene, or other nanostructures

Perovskite-Type LaSrMnO Electrocatalyst with Uniform Porous Structure for an Efficient Li–O₂ Battery Cathode

Perovskite is an excellent candidate as low cost catalyst for Li–O₂ cells. However, the limited porosity, which impedes molecular transport, and the inherent low electronic conductivity are the main barriers toward production of high-performance electrodes. Here, we designed a hierarchical porous flexible architecture by coating thin mesoporous yet crystalline LaSrMnO layers throughout a graphene foam to form graphene/<i>meso</i>-LaSrMnO sandwich-like nanosheets. In this well-designed system, the macropore between nanosheets facilitates O₂ and Li⁺ diffusion, the mesopore provides large surface area for electrolyte immersion and discharge products deposition, the perovskite phase catalyst decreases reactive overpotential, and the graphene serves as conductive network for electrons transport. When used as a freestanding electrode of Li–O₂ cell, it shows high specific capacity, superior rate capability, and cyclic stability. Combination of mesoporous perovskites with conductive graphene networks represents an effective strategy for developing efficient electrodes in various energy storage systems

Overtwisted, Resolvable Carbon Nanotube Yarn Entanglement as Strain Sensors and Rotational Actuators

Introducing twists into carbon nanotube yarns could produce hierarchical architectures and extend their application areas. Here, we utilized such twists to produce elastic strain sensors over large strain (up to 500%) and rotation actuators with high energy density. We show that a helical nanotube yarn can be overtwisted into highly entangled, macroscopically random but locally organized structures, consisting of mostly double-helix segments intertwined together. Pulling the yarn ends completely resolved the entanglement in an elastic and reversible way, yielding large tensile strains with linear change in electrical resistance. Resolving an entangled yarn and releasing its twists could simultaneously rotate a heavy object (30 000 times the yarn weight) for more than 1000 cycles at high speed. The rotational actuation generated from a single entangled yarn produced energy densities up to 8.3 kJ/kg, and maintained similar capacity during repeated use. Our entangled CNT yarns represent a complex self-assembled system with applications as large-range strain sensors and robust rotational actuators