Growth, properties, and applications of branched carbon nanostructures

Nanomaterials featuring branched carbon nanotubes (b-CNTs), nanofibers (b-CNFs), or other types of carbon nanostructures (CNSs) are of great interest due to their outstanding mechanical and electronic properties. They are promising components of nanodevices for a wide variety of advanced applications spanning from batteries and fuel cells to conductive-tissue regeneration in medicine. In this concise review, we describe the methods to produce branched CNSs, with particular emphasis on the most widely used b-CNTs, the experimental and theoretical studies on their properties, and the wide range of demonstrated and proposed applications, highlighting the branching structural features that ultimately allow for enhanced performance relative to traditional, unbranched CNSs

Tubular glassy carbon microneedles with fullerene-like tips for biomedical applications

Glassy carbon, in general, is made by the pyrolysis of polymeric materials and has been the subject of research for at least fifty years. However, as understanding its microstructure is far from straightforward, it continues to be an area of active research. Glassy carbon adopts different allotropes depending on the hybridizations of the C–C bond, that is, sp, sp2, or sp3. Furthermore, a variety of short-range ordering effects can interact with each other and this, along with the effects of microporosity, grain boundaries, and defects, render this a fascinating material. Following the nanoarchitectonics concept of bottom-up creation of functional materials, we use methane rather than a polymer to form glassy carbon. Here we show that tubular glassy carbon microneedles with fullerene-like tips form when methane undergoes pyrolysis on a curved alumina surface. X-ray diffraction of these glassy carbon tubules shows long-range order with a d-spacing of 4.89 Å, which is indicative of glassy carbon. Raman spectroscopy shows the material to be graphitic in nature, and SEM shows the fullerene-like structure of the material. This work provides new insights into the structure of glassy carbons relevant to the application of glassy carbons as a biomaterial, for example, as a new form of carbon-based microneedles. Since metallic needles can introduce toxic/allergenic species into susceptible subjects, this alternative carbon-based microneedle form has great potential as a replacement biomedical material for metallic needles in the field of neural engineering and as acupuncture needles

Electron microscopy of anionic surfactant-directed synthesis of magnetite nanoparticles

Here we report new work on the synthesis and an electron microscopy study of the earliest known magnetic material, magnetite (Fe$_{3}$O$_{4}$). We have synthesized a variety of magnetite nanoparticles which appear to have biogenic signatures and could give insights into how the nanomagnetite in biological systems forms, and how they may be associated with Alzheimer’s disease. We have also synthesized mesoporous magnetite nanoparticles which have potential use in the targeted drug delivery

Conductive hydrogel composites with autonomous self-healing properties

Conventional conductive hydrogels usually lack self-healing properties, but might be favorable for smart electronic applications. Therefore, we present the fabrication of conductive self-healing hydrogels that merge the merits of electrical conductivity and self-healing properties. The conductive self-healing hydrogel composite was prepared by using single-walled carbon nanotubes (SWCNTs), poly(vinyl alcohol) (PVA), and a poly(N,N-dimethyl acrylamide) copolymer derivative modified with pyrene and borate functional moieties. While the tethered pyrene groups of the copolymer facilitated an even dispersion of the conductive components, i.e., SWCNTs, in aqueous solution via π–π stacking, the hydrogel system was formed via covalent dynamic cross-linking through tetrahedral borate ion interaction with the –OH group of PVA. The hydrogel composites exhibited bulk conductivity (1.27 S m$^{−1}$ with 8 mg mL$^{−1}$ SWCNTs) with a fast and autonomous self-healing ability that restored 95% of the original conductivity within 10 s under ambient conditions. Accordingly, due to their outstanding properties, we postulate that these composites may have potential in biomedical applications, such as tissue engineering, wound healing or electronic skins

Gel actuators based on polymeric radicals

Low-voltage electrochemical actuation of radical polymer gels has been demonstrated in an organic electrolyte. Polymer gels were prepared by post-modification of active-ester precursor gels with an amine-functionalised radical. A combination of few-layer graphene and multiwall carbon nanotubes gave high conductivity and improved actuation in the gels, with 32% linear actuation. The actuator system showed good stability over at least 10 cycles, showing its promise. The cycle time was several hours due to mass-transport limited transport of ions and solvent into the device

Fabrication and characterization of branched carbon nanostructures

Carbon nanotubes (CNTs) have atomically smooth surfaces and tend not to form covalent bonds with composite matrix materials. Thus, it is the magnitude of the CNT/fiber interfacial strength that limits the amount of nanomechanical interlocking when using conventional CNTs to improve the structural behavior of composite materials through reinforcement. This arises from two wellknown, long standing problems in this research field: (a) inhomogeneous dispersion of the filler, which can lead to aggregation and (b) insufficient reinforcement arising from bonding interactions between the filler and the matrix. These dispersion and reinforcement issues could be addressed by using branched multiwalled carbon nanotubes (b-MWCNTs) as it is known that branched fibers can greatly enhance interfacial bonding and dispersability. Therefore, the use of b-MWCNTs would lead to improved mechanical performance and, in the case of conductive composites, improved electrical performance if the CNT filler was better dispersed and connected. This will provide major benefits to the existing commercial application of CNT-reinforced composites in electrostatic discharge materials (ESD): There would be also potential usage for energy conversion, e.g., in supercapacitors, solar cells and Li-ion batteries. However, the limited availability of b-MWCNTs has, to date, restricted their use in such technological applications. Herein, we report an inexpensive and simple method to fabricate large amounts of branched-MWCNTs, which opens the door to a multitude of possible applications

Smart textiles for sportswear and wearables (WG5): State-of-the art report. CONTEXT Project

The aim of this document is to provide information on the state-of- the-art related to the topics covered by each working group within the CONTEXT project. It provides information on materials and technologies used to develop smart textiles with targeted performance, general applications of smart textiles in the field, case-studies on the use of smart textiles, opportunities for smart textiles considering the needs of each field, trends on the development of smart textiles in terms of market and technical expectations