Toward Self-Powered Sensing and Thermal Energy Harvesting in High-Performance Composites v Self-Folded Carbon Nanotube Honeycomb Structures.

The development of high-performance self-powered sensors in advanced composites addresses the increasing demands of various fields such as aerospace, wearable electronics, healthcare devices, and the Internet-of-Things. Among different energy sources, the thermoelectric (TE) effect which converts ambient temperature gradients to electric energy is of particular interest. However, challenges remain on how to increase the power output as well as how to harvest thermal energy at the out-of-plane direction in high-performance fiber-reinforced composite laminates, greatly limiting the pace of advance in this evolving field.

Enhancing the Interfacial Shear Strength and Tensile Strength of Carbon Fibers through Chemical Grafting of Chitosan and Carbon Nanotubes.

Multi-scale "rigid-soft" material coating has been an effective strategy for enhancing the interfacial shear strength (IFSS) of carbon fibers (CFs), which is one of the key themes in composite research. In this study, a soft material, chitosan (CS), and a rigid material, carbon nanotubes (CNTs), were sequentially grafted onto the CFs surface by a two-step amination reaction. The construction of the "rigid-soft" structure significantly increased the roughness and activity of the CFs surface, which improved the mechanical interlocking and chemical bonding between the CFs and resin.

Mass Formation of α-Cyclodextrin Hexagonal Rods by the Direct Solvent Evaporation Strategy.

The self-assembly of cyclodextrins (CDs) with various guest polymers and small molecules has been intensively investigated for several decades, and it has still increasingly attracted wide attention to construct well-defined microstructures for the uses in biomedicine, sensors, environments, and nanorobotics. While most of the self-assembly of CDs involves the presence of guests, we recently discovered that α-CDs and γ-CDs could be self-assembled between themselves without the incorporation of any guests simply by elevating the temperature of their -dimethylformamide (DMF) solution. In this work, we further found that α-CDs could self-assemble or reorganize in DMF into hexagonal rods simply by directly drying out the α-CD DMF solution.

Ultrathin Two-Dimensional Metal-Organic Framework Nanosheets with Activated Ligand-Cluster Units for Enhanced SERS.

Ultrathin two-dimensional (2D) metal-organic framework (MOF) nanosheets (MOFNs) comprise an emerging family of attractive materials with excellent potential for use in different catalytic, electrochemical, and sensing applications owing to their striking features such as ultrathin thickness, a large surface area, and highly ordered network structures. However, to the best of our knowledge, the ligand-cluster units activated through exfoliation into the MOFNs have rarely been realized, which is indeed crucial for surface-enhanced Raman scattering (SERS) analysis. Herein, we emphasize that the activated ligand-cluster units are based on the accessible coordination sites at the exposed cluster nodes accompanied by a complete excitation of the ligand-cluster units under incident photons, which make MOFNs highly effective SERS substrates, significantly outperforming their bulk counterparts.

Silica Aerogels with Self-Reinforced Microstructure for Bioinspired Hydrogels.

Aerogel is a kind of high-performance lightweight open-porous solids with ultralow density, high specific surface area, and broad application in many emerging fields including biotechnology, energy, environment, aerospace, etc. A giant challenge remains in preventing of the hydrophilic aerogel framework shrinkage when replacing of solvent with air in its extremely abundant nanosized pores during its fabrication process in ambient conditions. In this work, started from a linear polymeric precursor with further condensation reaction, superhydrophilic silica aerogels with self-reinforced microstructure and the least volume shrinkage have been successfully obtained via ambient pressure drying process without use of any additives in the presence of a low surface tension solvent.

Metal-free synthesis of phosphinoylchroman-4-ones via a radical phosphinoylation-cyclization cascade mediated by KSO.

A variety of chroman-4-ones bearing phosphine oxide motifs were conveniently synthesized from readily available diphenylphosphine oxides and alkenyl aldehydes via a metal-free tandem phosphinoylation/cyclization protocol. The reaction utilizes KSO as oxidant and proceeds in DMSO/HO at environmentally benign conditions with a broad substrate scope and afforded the title compounds in moderate yields.

Rational and wide-range tuning of CNT aerogel conductors with multifunctionalities.

Different from conventional conductors, elastic 3D nanoarchitectured conductors have shown promise in developing various flexible devices. However, rational design and control of their microstructures to achieve desired physicochemical properties is challenging and lacks comprehensive and profound investigation. In this study, we report an interesting quantitative correlation between density and physical properties when highly porous CNT aerogels are densified, enabling a wide-range tuning of CNT 3D networked structures with different functions.

Multifunctional Aramid Nanofiber/Carbon Nanotube Hybrid Aerogel Films.

Lightweight, robust, and thin aerogel films with multifunctionality are highly desirable to meet the technological demands of current society. However, fabrication and application of these multifunctional aerogel films are still significantly underdeveloped. Herein, we demonstrate a multifunctional aerogel film composed of strong aramid nanofibers (ANFs), conductive carbon nanotubes (CNTs), and hydrophobic fluorocarbon (FC) resin.

Understanding the Mechanical and Conductive Properties of Carbon Nanotube Fibers for Smart Electronics.

The development of fiber-based smart electronics has provoked increasing demand for high-performance and multifunctional fiber materials. Carbon nanotube (CNT) fibers, the 1D macroassembly of CNTs, have extensively been utilized to construct wearable electronics due to their unique integration of high porosity/surface area, desirable mechanical/physical properties, and extraordinary structural flexibility, as well as their novel corrosion/oxidation resistivity. To take full advantage of CNT fibers, it is essential to understand their mechanical and conductive properties.

Electrochromic semiconductors as colorimetric SERS substrates with high reproducibility and renewability.

Electrochromic technology has been actively researched for displays, adjustable mirrors, smart windows, and other cutting-edge applications. However, it has never been proposed to overcome the critical problems in the field of surface-enhanced Raman scattering (SERS). Herein, we demonstrate a generic electrochromic strategy for ensuring the reproducibility and renewability of SERS substrates, which are both scientifically and technically important due to the great need for quantitative analysis, standardized production and low cost in SERS.

Erratum: 3D Printing Fiber Electrodes for an All-Fiber Integrated Electronic Device via Hybridization of an Asymmetric Supercapacitor and a Temperature Sensor.

[This corrects the article DOI: 10.1002/advs.201801114.

3D Printing Fiber Electrodes for an All-Fiber Integrated Electronic Device via Hybridization of an Asymmetric Supercapacitor and a Temperature Sensor.

Wearable fiber-shaped electronic devices have drawn abundant attention in scientific research fields, and tremendous efforts are dedicated to the development of various fiber-shaped devices that possess sufficient flexibility. However, most studies suffer from persistent limitations in fabrication cost, efficiency, the preparation procedure, and scalability that impede their practical application in flexible and wearable fields. In this study, a simple, low-cost 3D printing method capable of high manufacturing efficiency, scalability, and complexity capability to fabricate a fiber-shaped integrated device that combines printed fiber-shaped temperature sensors (FTSs) with printed fiber-shaped asymmetric supercapacitors (FASCs) is developed.

Growth of boron nitride nanotubes from magnesium diboride catalysts.

The difficulty in synthesizing boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace by chemical vapor deposition (CVD) may be ascribed to the failure to identify suitable catalysts and nucleation particles. This report demonstrates that magnesium diboride (MgB) can effectively catalyze the growth of BNNTs in such a tube furnace from various boron sources, including boron oxide (BO), boric acid (HBO), and a mixture of boron (B) and calcium oxide (CaO). This catalyst is more efficient than the possible magnesium oxide (MgO) or magnesium nitride (MgN) catalysts.

Ammonium-tungstate-promoted growth of boron nitride nanotubes.

Ammonium tungstate ((NH)WO · xHO) is a kind of oxygen-containing ammonium salt. The following study proves that it can be successfully used as a metal oxide alternative to produce boron oxide (BO) by oxidizing boron (B) in a traditional boron oxide chemical vapor deposition (BOCVD) process. This special oxidant promotes the simplistic fabrication of boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace, an outcome which may have resulted from its strong oxidizability.

Polyaniline-stabilized electromagnetic wave absorption composites of reduced graphene oxide on magnetic carbon nanotube film.

A multi-layered composite with exceptionally high electromagnetic wave-absorbing capacity and performance stability was fabricated via the facile electrophoresis of a reduced graphene oxide network on carbon nanotube (CNT)-FeO-polyaniline (PANI) film. Minimum reflection loss (RL) of -53.2 dB and absorbing bandwidth of 5.

Active Manipulation of NIR Plasmonics: the Case of CuSe through Electrochemistry.

Active control of nanocrystal optical and electrical properties is crucial for many of their applications. By electrochemical (de)lithiation of CuSe, a highly doped semiconductor, dynamic and reversible manipulation of its NIR plasmonics has been achieved. Spectroelectrochemistry results show that NIR plasmon red-shifted and reduced in intensity during lithiation, which can be reversed with perfect on-off switching over 100 cycles.

Semiconductor SERS enhancement enabled by oxygen incorporation.

Semiconductor-based surface-enhanced Raman spectroscopy (SERS) substrates represent a new frontier in the field of SERS. However, the application of semiconductor materials as SERS substrates is still seriously impeded by their low SERS enhancement and inferior detection sensitivity, especially for non-metal-oxide semiconductor materials. Herein, we demonstrate a general oxygen incorporation-assisted strategy to magnify the semiconductor substrate-analyte molecule interaction, leading to significant increase in SERS enhancement for non-metal-oxide semiconductor materials.

Superb electromagnetic wave-absorbing composites based on large-scale graphene and carbon nanotube films.

Graphene has sparked extensive research interest for its excellent physical properties and its unique potential for application in absorption of electromagnetic waves. However, the processing of stable large-scale graphene and magnetic particles on a micrometer-thick conductive support is a formidable challenge for achieving high reflection loss and impedance matching between the absorber and free space. Herein, a novel and simple approach for the processing of a CNT film-FeO-large scale graphene composite is studied.

Morphology-Controlled Synthesis of Hybrid Nanocrystals via a Selenium-Mediated Strategy with Ligand Shielding Effect: The Case of Dual Plasmonic Au-CuSe.

Integrating a plasmonic metal and a semiconductor at the nanoscale is of great importance for exploring their optical coupling properties. However, the synthesis and fine structural control of such nanostructures remain challenging. Herein we report the facile aqueous-phase Se-mediated overgrowth of metal selenides onto Au nanocrystals.

Wrapping Aligned Carbon Nanotube Composite Sheets around Vanadium Nitride Nanowire Arrays for Asymmetric Coaxial Fiber-Shaped Supercapacitors with Ultrahigh Energy Density.

The emergence of fiber-shaped supercapacitors (FSSs) has led to a revolution in portable and wearable electronic devices. However, obtaining high energy density FSSs for practical applications is still a key challenge. This article exhibits a facile and effective approach to directly grow well-aligned three-dimensional vanadium nitride (VN) nanowire arrays (NWAs) on carbon nanotube (CNT) fiber with an ultrahigh specific capacitance of 715 mF/cm in a three-electrode system.

Omnidirectionally Stretchable High-Performance Supercapacitor Based on Isotropic Buckled Carbon Nanotube Films.

The emergence of stretchable electronic devices has attracted intensive attention. However, most of the existing stretchable electronic devices can generally be stretched only in one specific direction and show limited specific capacitance and energy density. Here, we report a stretchable isotropic buckled carbon nanotube (CNT) film, which is used as electrodes for supercapacitors with low sheet resistance, high omnidirectional stretchability, and electro-mechanical stability under repeated stretching.

Graphene-Based Fibers: A Review.

Motivated by their unique structure and excellent properties, significant progress has been made in recent years in the development of graphene-based fibers (GBFs). Potential applications of GBFs can be found, for instance, in conducting wires, energy storage and conversion devices, actuators, field emitters, solid-phase microextraction, springs, and catalysis. In contrast to graphene-based aerogels (GBAs) and membranes (GBMs), GBFs demonstrate remarkable mechanical and electrical properties and can be bent, knotted, or woven into flexible electronic textiles.

Stretchable Wire-Shaped Asymmetric Supercapacitors Based on Pristine and MnO2 Coated Carbon Nanotube Fibers.

While the emerging wire-shaped supercapacitors (WSS) have been demonstrated as promising energy storage devices to be implemented in smart textiles, challenges in achieving the combination of both high mechanical stretchability and excellent electrochemical performance still exist. Here, an asymmetric configuration is applied to the WSS, extending the potential window from 0.8 to 1.

Dry-processable carbon nanotubes for functional devices and composites.

Assembly of carbon nanotubes (CNTs) in effective and productive ways is of vital importance to their application. Recent progress in synthesis of CNTs has inspired new strategies for utilizing the unique physiochemical properties of CNTs in macroscale materials and devices. Assembling CNTs by dry processes (e.

Microstructural evolution of carbon nanotube fibers: deformation and strength mechanism.

A comprehensive investigation of the mechanical behavior and microstructural evolution of carbon nanotube (CNT) continuous fibers under twisting and tension is conducted using coarse-grained molecular dynamics simulations. The tensile strength of CNT fibers with random CNT stacking is found to be higher than that of fibers with regular CNT stacking. The factor dominating the mechanical response of CNT fibers is identified as individual CNT stretching.