Multiplexed Free-Standing Nanowire Transistor Bioprobe for Intracellular Recording: A General Fabrication Strategy

Recent advance in free-standing nanowire transistor bioprobes opens up new opportunities of accurately interfacing spatially unobstructed nanoscale sensors with live cells. However, the existing fabrication procedures face efficiency and yield limitations when working with more complex nanoscale building blocks to integrate, for example, multiplexed recordings or additional functionalities. To date, only single-kinked silicon nanowires have been successfully used in such probes. Here we establish a general fabrication strategy to mitigate such limitations with which synthetically designed complex nanoscale building blocks can be readily used without causing significant penalty in yield or fabrication time, and the geometry of the probe can be freely optimized based on the orientation and structure of the building blocks. Using this new fabrication framework, we demonstrate the first multiplexed free-standing bioprobe based on w-shaped silicon kinked nanowires that are synthetically integrated with two nanoscale field-effect transistor devices. Simultaneous recording of intracellular action potentials from both devices have been obtained of a single spontaneously beating cardiomyocyte

VO₂ Nanowires Assembled into Hollow Microspheres for High-Rate and Long-Life Lithium Batteries

Development of three-dimensional nanostructures with high surface area and excellent structural stability is an important approach for realizing high-rate and long-life battery electrodes. Here, we report VO₂ hollow microspheres showing empty spherical core with radially protruding nanowires, synthesized through a facile and controllable ion-modulating approach. In addition, by controlling the self-assembly of negatively charged C₁₂H₂₅SO₄^– spherical micelles and positively charged VO²⁺ ions, six-armed microspindles and random nanowires are also prepared. Compared with them, VO₂ hollow microspheres show better electrochemical performance. At high current density of 2 A/g, VO₂ hollow microspheres exhibit 3 times higher capacity than that of random nanowires, and 80% of the original capacity is retained after 1000 cycles. The superior performance of VO₂ hollow microspheres is because they exhibit high surface area about twice higher than that of random nanowires and also provide an efficient self-expansion and self-shrinkage buffering during lithiation/delithiation, which effectively inhibits the self-aggregation of nanowires. This research indicates that VO₂ hollow microspheres have great potential for high-rate and long-life lithium batteries

Design and Synthesis of Diverse Functional Kinked Nanowire Structures for Nanoelectronic Bioprobes

Functional kinked nanowires (KNWs) represent a new class of nanowire building blocks, in which functional devices, for example, nanoscale field-effect transistors (nanoFETs), are encoded in geometrically controlled nanowire superstructures during synthesis. The bottom-up control of both structure and function of KNWs enables construction of spatially isolated point-like nanoelectronic probes that are especially useful for monitoring biological systems where finely tuned feature size and structure are highly desired. Here we present three new types of functional KNWs including (1) the zero-degree KNW structures with two parallel heavily doped arms of U-shaped structures with a nanoFET at the tip of the “U”, (2) series multiplexed functional KNW integrating multi-nanoFETs along the arm and at the tips of V-shaped structures, and (3) parallel multiplexed KNWs integrating nanoFETs at the two tips of W-shaped structures. First, U-shaped KNWs were synthesized with separations as small as 650 nm between the parallel arms and used to fabricate three-dimensional nanoFET probes at least 3 times smaller than previous V-shaped designs. In addition, multiple nanoFETs were encoded during synthesis in one of the arms/tip of V-shaped and distinct arms/tips of W-shaped KNWs. These new multiplexed KNW structures were structurally verified by optical and electron microscopy of dopant-selective etched samples and electrically characterized using scanning gate microscopy and transport measurements. The facile design and bottom-up synthesis of these diverse functional KNWs provides a growing toolbox of building blocks for fabricating highly compact and multiplexed three-dimensional nanoprobes for applications in life sciences, including intracellular and deep tissue/cell recordings

Ultralong Sb₂Se₃ Nanowire-Based Free-Standing Membrane Anode for Lithium/Sodium Ion Batteries

Metal chalcogenides have emerged as promising anode materials for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). Herein, a free-standing membrane based on ultralong Sb₂Se₃ nanowires has been successfully fabricated via a facile hydrothermal synthesis combined with a subsequent vacuum filtration treatment. The as-achieved free-standing membrane constructed by pure Sb₂Se₃ nanowires exhibits good flexibility and integrity. Meanwhile, we investigate the lithium and sodium storage behavior of the Sb₂Se₃ nanowire-based free-standing membrane. When applied as the anode for LIBs, it delivers a reversible capacity of 614 mA h g^–1 at 100 mA g^–1, maintaining 584 mA h g^–1 after 50 cycles. When applied as the anode for SIBs, it delivers a reversible capacity of 360 mA h g^–1 at 100 mA g^–1, retaining 289 mA h g^–1 after 50 cycles. Such difference in electrochemical performance can be attributed to the more complex sodiation process relative to the corresponding lithiation process. This work may provide insight on developing Sb₂Se₃-based anode materials for high-performance LIBs or SIBs

Lipoic Acid-Assisted In Situ Integration of Ultrathin Solid-State Electrolytes

Ultrathin solid-state electrolytes (SSEs) have contributed to high-energy-density lithium-ion batteries (LIBs). However, when reducing thickness of SSEs, mechanical properties will inevitably deteriorate, even increasing the safety hazards. In this work, we developed an in-situ integration strategy to form an ultrathin SSE by combining a lipoic acid-assisted semi-interpenetrating polymer network and an ultrathin porous membrane. With this strategy, the thickness of the obtained SSE (named LA-SSE) is only 10 μm, and the LA-SSE possesses extraordinary mechanical performances to suppress the growth of lithium dendrites. Meanwhile, the flexible LA-SSE presents anionic conductivity of 0.036 mS cm–1 and promotes interfacial compatibility between the lithium anode and the electrolyte. By employing LA-SSE as the electrolyte, the assembled Li∥LA-SSE∥Li symmetric cell operated with long-term cycling (more than 3000 h), and the LiFePO4∥LA-SSE∥Li full battery worked steadily over 200 cycles at 0.5 C with a capacity retention of 84% at room temperature. This work provides a promising strategy for designing ultrathin SSEs, with satisfactory mechanical properties, excellent interfacial compatibility, and safety, for LIBs

Synergistic Effect of Hierarchical Nanostructured MoO₂/Co(OH)₂ with Largely Enhanced Pseudocapacitor Cyclability

Pseudocapacitors have demonstrated an ability to deliver high energy and power densities. The main limitation is their poor cyclability and for this reason the architectural design of electrode materials has attracted considerable attention. Here we report the synthesis of hierarchical nanostructured material by growing Co­(OH)₂ nanoflakes onto MoO₂ thin film. The electrode material exhibits a high capacitance of 800 F g^–1 at 20 A g^–1 with only 3% capacitance loss after 5000 cycles and high rate capability with increasing current density from 2 to 40 A g^–1, which are better than those of individual component. The enhanced pseudocapacitor performances benefit from the synergistic effect of the hierarchical nanostructure: (1) faster ion diffusion and electron transport at electrode/electrolyte interface, and (2) mitigation of the electrode destruction caused by ion insertion/deinsertion during charge-storage process. This facile design and rational synthesis offers an effective strategy to enhance the electrochemical performance of pseudocapacitors and shows promising potential for large-scale application in energy storage

Enhancement of Photovoltaic Performance by Utilizing Readily Accessible Hole Transporting Layer of Vanadium(V) Oxide Hydrate in a Polymer–Fullerene Blend Solar Cell

Herein, a successful application of V₂O₅·<i>n</i>H₂O film as hole transporting layer (HTL) instead of PEDOT:PSS in polymer solar cells is demonstrated. The V₂O₅·<i>n</i>H₂O layer was spin-coated from V₂O₅·<i>n</i>H₂O sol made from melting-quenching sol–gel method by directly using vanadium oxide powder, which is readily accessible and cost-effective. V₂O₅·<i>n</i>H₂O (<i>n</i> ≈ 1) HTL is found to have comparable work function and smooth surface to that of PEDOT:PSS. For the solar cell containing V₂O₅·<i>n</i>H₂O HTL and the active layer of the blend of a novel polymer donor (PBDSe-DT2PyT) and the acceptor of PC₇₁BM, the PCE was significantly improved to 5.87% with a 30% increase over 4.55% attained with PEDOT:PSS HTL. Incorporation of V₂O₅·<i>n</i>H₂O as HTL in the polymer solar cell was found to enhance the crystallinity of the active layer, electron-blocking at the anode and the light-harvest in the wavelength range of 400–550 nm in the cell. V₂O₅·<i>n</i>H₂O HTL improves the charge generation and collection and suppress the charge recombination within the PBDSe-DT2PyT:PC₇₁BM solar cell, leading to a simultaneous enhancement in <i>V</i>_oc, <i>J</i>_sc, and FF. The V₂O₅·<i>n</i>H₂O HTL proposed in this work is envisioned to be of great potential to fabricate highly efficient PSCs with low-cost and massive production

Electrostatic Assembly of Sandwich-like Ag-C@ZnO-C@Ag‑C Hybrid Hollow Microspheres with Excellent High-Rate Lithium Storage Properties

Herein, we introduce a facile electrostatic attraction approach to produce zinc–silver citrate hollow microspheres, followed by thermal heating treatment in argon to ingeniously synthesize sandwich-like Ag-C@ZnO-C@Ag-C hybrid hollow microspheres. The 3D carbon conductive framework in the hybrids derives from the <i>in situ</i> carbonation of carboxylate acid groups in zinc–silver citrate hollow microspheres during heating treatment, and the continuous and homogeneous Ag nanoparticles on the outer and inner surfaces of hybrid hollow microspheres endow the shells with the sandwiched configuration (Ag-C@ZnO-C@Ag-C). When applied as the anode materials for lithium ion batteries, the fabricated hybrid hollow microspheres with sandwich-like shells reveal a very large reversible capacity of 1670 mAh g^–1 after 200 cycles at a current density of 0.2 A g^–1. Even at the very large current densities of 1.6 and 10.0 A g^–1, the high specific capacities of about 1063 and 526 mAh g^–1 can be retained, respectively. The greatly enhanced electrochemical properties of Ag-C@ZnO-C@Ag-C hybrid microspheres are attributed to their special structural features such as the hollow structures, the sandwich-like shells, and the nanometer-sized building blocks

NiSe₂ Nanooctahedra as an Anode Material for High-Rate and Long-Life Sodium-Ion Battery

In this article, we report NiSe₂ nanooctahedra as a promising anode material for sodium-ion batteries (SIBs). They exhibit outstanding long-term cyclic stability (313 mAh/g after 4000 cycles at 5 A/g) and excellent high-rate capability (175 mAh/g at 20 A/g). Besides, the initial Coulombic efficiency of NiSe₂ is also very impressive (over 90%). Such remarkable performances are attributed to good conductivity, structural stability, and the pseudocapacitive behavior of the NiSe₂. Furthermore, the sodium ion storage mechanism of NiSe₂ is first investigated by <i>in situ</i> XRD and <i>ex situ</i> XRD. These highlights give NiSe₂ a competitive strength for rechargeable SIBs

Porous and Low-Crystalline Manganese Silicate Hollow Spheres Wired by Graphene Oxide for High-Performance Lithium and Sodium Storage

Herein, a graphene oxide (GO)-wired manganese silicate (MS) hollow sphere (MS/GO) composite is successfully synthesized. Such an architecture possesses multiple advantages in lithium and sodium storage. The hollow MS structure provides a sufficient free space for volume variation accommodation; the porous and low-crystalline features facilitate the diffusion of lithium ions; meanwhile, the flexible GO sheets enhance the electronic conductivity of the composite to a certain degree. When applied as the anode material for lithium-ion batteries (LIBs), the as-obtained MS/GO composite exhibits a high reversible capacity, ultrastable cyclability, and good rate performance. Particularly, the MS/GO composite delivers a high capacity of 699 mA h g^–1 even after 1000 cycles at 1 A g^–1. The sodium-storage performance of MS/GO has been studied for the first time, and it delivers a stable capacity of 268 mA h g^–1 after 300 cycles at 0.2 A g^–1. This study suggests that the rational design of metal silicates would render them promising anode materials for LIBs and SIBs