#TeddersRecommends

The reversible conversion between 4-aminothiophenol and p,p′-dimerc­aptoazobenzene is performed with a single Ag nanoparticles/graphene oxide nanocomposite (AgNPs/GO) via the assistance of local surface plasmons. The formation of p,p′-dimercaptoazobenzene on AgNPs/GO leads to the decrease in distance between adjacent AgNPs on a GO surface, enhancing the local electromagnetic field near AgNPs. This effect is beneficial to enhancing surface Raman enhanced scattering signals of Rhodamine 6G molecules.

The direct transfer method of large area monolayer CVD graphene from Cu foil to various substrates such as PET, PDMS, and glass is developed using mechano-electro-thermal forces based on ultraconformal contact without any metal etching process or additional carrier layers in a solid-state process. Transferred graphene presents both excellent quality (with no residues, few defects, or no folding) and remarkable mechanical and electrical stability.

An efficient procedure for the fabrication of highly conductive carbon nanotube/graphene hybrid yarns has been developed. To start, arrays of vertically aligned multi-walled carbon nanotubes (MWNT) are converted into indefinitely long MWNT sheets by drawing. Graphene flakes are then deposited onto the MWNT sheets by electrospinning to form a composite structure that is transformed into yarn filaments by twisting. The process is scalable for yarn fabrication on an industrial scale. Prepared materials are characterized by electron microscopy, electrical, mechanical, and electrochemical measurements. It is found that the electrical conductivity of the composite MWNT-graphene yarns is over 900 S/cm. This value is 400% and 1250% higher than electrical conductivity of pristine MWNT yarns or graphene paper, respectively. The increase in conductivity is asssociated with the increase of the density of states near the Fermi level by a factor of 100 and a decrease in the hopping distance by an order of magnitude induced by grapene flakes. It is found also that the MWNT-graphene yarn has a strong electrochemical response with specific capacitance in excess of 111 Fg⁻¹. This value is 425% higher than the capacitance of pristine MWNT yarn. Such substantial improvements of key properties of the hybrid material can be associated with the synergy of MWNT and graphene layers in the yarn structure. Prepared hybrid yarns can benefit such applications as high-performance supercapacitors, batteries, high current capable cables, and artificial muscles.

Highly conductive hybrid multi-walled carbon nanotubes/graphene yarn are produced in a continuous, scalable process. Graphene dispersions are deposited onto the MWNT sheets by electrospinning to form a composite structure that is transformed by twist insertion into yarn filaments. The novel hybrid yarns will be useful in wearable electronic textiles applications such as batteries, high-performance supercapacitors, high current capable cables, and artificial muscles.

Unidirectional rubbing of a dry powder between two flat rubbery substrates enables quick large-area single-crystal monolayer assembly of microparticles. The rubbing process is applicable to curved surfaces, as shown here in this frontispiece. Various parameters for the rubbing conditions, such as pressure, rubbing speed, and adhesion energy of substrate, are discussed in detail by U. Jeong, J. Myoung, and co-workers on page 4633.

Chaotic advection plays an important role in microplatforms for a variety of applications. Currently used mechanisms for inducing chaotic advection in small scale, however, are limited by their complicated fabrication processes and relatively high power consumption. Here, a soft actuator is reported which utilizes a droplet of Galinstan liquid metal to induce harmonic Marangoni flow at the surface of liquid metal when activated by a sinusoidal signal. This liquid metal actuator has no rigid parts and employs continuous electrowetting effect to induce chaotic advection with exceptionally low power consumption. The theory behind the operation of this actuator is developed and validated via a series of experiments. The presented actuator can be readily integrated into other microfluidic components for a wide range of applications.

A soft actuator is developed which utilizes a droplet of Galinstan liquid metal to induce harmonic Marangoni flow at the surface of liquid metal when activated by a sinusoidal signal. This liquid metal actuator has no rigid parts and can be readily integrated into other microfluidic components for a wide range of applications.

Transition metal compounds based on conversion reactions are promising electrode materials for lithium-ion batteries due to their higher lithium storage capacity compared with currently available commercial battery electrodes. Most of the studies on these materials in the literature focus on transition metal oxides and fluorides, and not much work on transition metal sulphides has been reported, partially due to their relatively poor electrochemical performance. Here, synthesis and characterization of a series of solid solution Fe_xMn_1-xS (x = 0.2, 0.5, 0.8) monosulphide compounds is reported. Interestingly, hexagonal FeS and cubic MnS can form a solid solution of Fe_xMn_1-xS (x < 0.57). It is demonstrated that the lithium storage voltage can be tuned by changing the Fe concentration in the Fe_xMn_1-xS matrix; meanwhile, the discharge-charge coulombic efficiency and cycle stability of Fe_xMn_1-xS are greatly enhanced in comparison with that of pure MnS. A half cell using Fe_0.5Mn_0.5S as electrode material achieves a high first cycle coulombic efficiency of 78.0% and a high reversible capacity of ca. 477 mAh g⁻¹ after 35 cycles, while for pure MnS the first cycle coulombic efficiency is only 45.9% and the capacity rapidly fades to ≈200 mAh g⁻¹ after 15 cycles. Although the solid solution state of Fe_0.5Mn_0.5S cannot be retained during conversion reaction as indicated by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM), the initial discharge “polarization”, which has been considered as one of the major hurdles for conversion reaction, can be significantly reduced by this type of material design. In addition, the size and distribution of the nucleated nanophases might also be altered by the initial solid solution state of Fe_0.5Mn_0.5S, contributing to the improved electrochemical performance reported here.

A series of Fe_xMn_1-xS (x = 0.2, 0.5, 0.8) monosulphide compounds is synthesized using a simple solid state reaction method. The lithium storage voltage can be tuned by the content of Fe in Fe_xMn_1-xS, while the electrochemical performance of electrodes based on Fe_xMn_1-xS is greatly enhanced in comparison with that of MnS. The lithium storage mechanism of Fe_0.5Mn_0.5S is investigated in detail.