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As a key method to convert solar into chemical energy, photocatalytic water decomposition has garnered attention. Moreover, the development of graphene and graphene-like two-dimensional (2D) materials has brought fresh vitality in the field of photocatalysis. Here, we prepared two to four layers of GeTe nanosheets by ultrasonic-assisted liquid-phase exfoliation in argon and air, which we referred to as Ar-GeTe and O-GeTe, respectively. The photocatalytic hydrogen production potential of 2D GeTe was experimentally investigated for the first time. The results indicated that minimally layered GeTe samples are indirect-gap semiconductors with the GeTe band gap increasing after oxidation. All samples have suitable band positions that can drive photocatalytic water splitting into H2 under mild conditions, providing maximum hydrogen evolution rates of 1.13 mmol g-1 h-1 (Ar-GeTe) and 0.54 mmol g-1 h-1 (O-GeTe). With density functional theory computations, the structural stability of GeTe in air was discussed, revealing that oxygen atoms could easily combine with Ge to form a more stable structure, thus impacting the photocatalytic performance of 2D GeTe. Therefore, the light requirement and oxygen deficiency of the material give an advantage in the field of energy supply in space.

Germanene, as a cousin of graphene, has shared increasing attention in recent years. There have been abundant theoretical and experimental reports on the synthesis and physicochemical properties of germanene, but few experiments have investigated the energy storage properties. Herein, this study reports the electrochemical properties of GeCH3, a methyl terminated germanene, as anode materials for lithium-ion batteries (LIBs). First, few-layer GeCH3 nanosheets were prepared by liquid-phase exfoliation. Then to further explore the electrochemical lithium storage potential of GeCH3 nanosheets, sandwiched GeCH3/rGO nanocomposites were prepared by adding rGO as a conductive agent and stabilizer through a simple ultrasonic wet dispersion mixing process. The resulting nanocomposite exhibited a remaining capacity of 1058 mAh g−1 after 100 cycles at 0.2 A g−1, indicating that GeCH3 nanocomposite is a promising high energy density anode material. This encouraging result may shed light on the application of germanene in LIBs.

Two reported three-dimensional covalent organic frameworks (3D-COFs), COF-300 and COF-301, which have hierarchical porous structures and large pore volumes, were synthesized and employed as host materials for lithium-sulfur batteries. Owing to possessing excellent porosities as well as abundant hydroxyl groups in the pore walls, COF-301 can not only trap lithium polysulfides (PSs) via physical adsorption inside the pores, but also capture PSs by chemical interactions to relieve the shuttle effect. Interestingly, it is the first time that 3D-COFs were utilized as host materials for lithium-sulfur batteries as well as hydroxyl groups were introduced into COFs for improving the battery performance. As a result, COF-301@S as cathode material could reserve the capacity of 411.6 mA·h·g−1 after 500 cycles with only 0.081% fading per cycle at 0.5 C, exhibiting better battery performance compared with COF-300@S. This study not only expands the applications of 3D-COFs but also provides a new route for designing lithium-sulfur batteries.

The objective of present study is to determine the effects of grain size and deformation twin density on mechanical behaviors linked to microstructure evolution of AZ31 magnesium (Mg) alloy. The AZ31 Mg alloy was processed by warm sever plastic deformation method and followed by dynamic compression (strain rate ∼ 1 × 103 s−1, plastic strain ∼ 10%). Uniaxial tensile experiments at room temperature have revealed that AZ31 Mg alloy is exhibited enhanced strength with grain refinement and high deformation twin density. The improved strength of AZ31 Mg alloy is attributed to the hindering effect of increasing grain boundaries (GBs) and twin boundaries (TBs) on dislocation motion, thereby making plastic deformation more difficult. As a result, the large reduction in ductility has been found for fine grained AZ31 Mg alloy (grain size is about 2–3 μm). But with increasing deformation twin density after dynamic compression (especially in fine grained samples), the obvious ductility enhancement has been found in both coarse grained and fine grained AZ31 Mg alloy. With mechanical behaviors properly described, both strength and ductility can be simultaneously achieved in fine grained and high twin density AZ31 Mg alloy.

Deformation-controlled solar thermal storage and release are important for thermal management of dynamic systems. However, few researchers have examined cyclic solid-state solar thermal utilization...

Stress-sensitive thermally conductive elastic materials are necessary for designing flexible, thermal-sensitive devices such as sensors or skins. However, combining high thermal conductivity (k) and good cyclic resilience (elastic deformation) is challenging according to the Newton−Laplace equation. This study presents a graphite-welded carbon nanotube (w-CNT) sponges as a three-dimensional skeleton for polydimethylsiloxane (PDMS) composites. Welds of discontinuous CNT with graphite layers promote phonon and stress transfer at the junctions. The interconnected network and uniform closely packed polymers not only enable stress-sensitive heat conduction but also retain excellent cyclic elastic deformability and good resilience. The composite combines a stress-sensitive isotropic k and excellent elastic deformation. The w-CNT/PDMS composite at the content of 4.57 wt% w-CNT exhibits a high k up to 13.1 W m−1 K−1 at 29.2% compressive strain. The composite also retains high k with the loss of 2% after 100000 compression cycles. The stress-sensitive w-CNT/PDMS composite enable it to be used in a flexible thermal-sensitive strain sensor. The bending and stretching of the finger are tracked by thermochromic changes controlled by stress-enhanced heat conduction. The stress-sensitive thermally conductive w-CNT/PDMS composites can be developed for a multitude of flexible sensors by optimizing their microstructures.

The discovery of graphene and graphene-like two-dimensional materials has brought fresh vitality to the field of photocatalysis. Bandgap engineering has always been an effective way to make semiconductors more suitable for specific applications such as photocatalysis and optoelectronics. Achieving control over the bandgap helps to improve the light absorption capacity of the semiconductor materials, thereby improving the photocatalytic performance. This work reports two-dimensional −H/−OH terminal-substituted siligenes (gersiloxenes) with tunable bandgap. All gersiloxenes are direct-gap semiconductors and have wide range of light absorption and suitable band positions for light driven water reduction into H2, and CO2 reduction to CO under mild conditions. The gersiloxene with the best performance can provide a maximum CO production of 6.91 mmol g−1 h−1, and a high apparent quantum efficiency (AQE) of 5.95% at 420 nm. This work may open up new insights into the discovery, research and application of new two-dimensional materials in photocatalysis. Solar energy conversion may provide a renewable means to store energy as fuels, although there are a limited range of suitable photocatalysts. Here authors develop germanium and silicon based 2D materials with tunable bandgaps for high-performance photocatalytic water and CO2 reduction.

Large-area uniform of single-crystal tungsten disulfide (WS2) is important for advanced optoelectronics based on two-dimensional (2D) atomic crystals. However, difficulties in controlling the interrelated growth parameters restrict its development in devices. Herein, we present the synthesis of triangular monolayered WS2 flakes with good uniformity and single crystal by adjusting the introduction time of sulfur precursor and the distances between the sources and substrates to control the nucleation density. Investigation of the morphology and structure by transmission electron microscopy and Raman spectroscopy indicates that a series of triangular (side length of 233 μm) monolayered WS2 flakes shows high-quality structure and homogenous crystallinity. Field-effect transistors based on the fabricated triangular monolayered WS2 with single crystal demonstrate environmentally stable charge transport with a field-effect mobility of 50.5 cm2/V s and current modulation Ion/ Ioff of ∼107. The results of this study pave the way for the application of monolayered WS2 in a multitude of 2D-material-based devices.

We describe sonication-assisted liquid-phase exfoliation of rhombohedral germanium telluride (α-GeTe) to obtain a good dispersion of α-GeTe nanosheets in ethanol. The thickness of the α-GeTe nanosheets is dependent on the exfoliation conditions, and few-layer α-GeTe nanosheets of 2-4 layers and even monolayer α-GeTe were obtained. We use first-principles calculations to investigate the structural, electronic, and optical properties of monolayer and bulk α-GeTe and compare the optical band gap of centrifugally fractionated α-GeTe nanosheet dispersions with the computational predictions. We demonstrate that few layer α-GeTe nanosheets are purified selectively through centrifugation, and they exhibit high sensitivity to Fe3+. The scalable production of two-dimensional α-GeTe nanosheets can be used in the future optoelectronic industry.

Benzoic acid carboxymethyl ester derivatives (BACED) with different substituents and their Eu(III) complexes (Eu(BACED)(3)(H2O)(2)) were synthesized, BACED being a bidentate ligand. The as-prepared complexes showed cloud flake aggregation structures with size in the range of 50-60 nm. The luminescence spectra of the complexes indicated effective energy transfer from BACED to Eu3+. Three distinct peaks were observed in the excitation spectra of the Eu(III) complexes containing BACED and the as-prepared complexes exhibited effective emission when the wavelengths corresponding to these peaks were used as the excitation wavelengths. The longest luminescence lifetime of the as-prepared complexes was 1099.25 mu s and the best luminescent quantum efficiency was 59.21%. These results indicate that the Eu(III) complexes with BACED have excellent potential for use as luminescent materials. (C) 2015 Elsevier B.V. All rights reserved.

Lithium-sulfur batteries are considered as the next generation of energy storage systems because of their high theoretical specific capacity and energy density. Unfortunately, the sluggish reaction kinetics, weak adsorption toward to lithium polysulfides, and slow lithium ion diffusion impede the smooth electrochemical process, resulting in the lithium-sulfur batteries with the unsatisfactory cycling stability and rate performance. Since it is recognized that polar metal oxides and doped nitrogen in carbon materials have chemical interaction with lithium polysulfides, a nanostructured nitrogen-doped porous carbon/MoO2 composite is synthesized through a simple hydrothermal method by using graphene oxide nanoribbon and phosphomolybdic acid hydrate as precursors. The porous nanostructure promotes the charge and mass transport, while MoO2 nanoparticles immobilize lithium polysulfides via strong chemisorption and enhance the redox kinetics of polysulfides owing to the efficient catalytic activity in liquid-solid boundary. Consequently, the as-obtained nanostructured porous carbon/MoO2-based sulfur cathode exhibits low polarization, high initial discharge capacity (1403 mAh g-1 at 0.1 C), good rate capabilities (584 mAh g-1 at 4 C), and impressive cycling performance at 1 C (503 mAh g-1 after 500 cycles with capacity fade rate of 0.07% per cycle).

nanomicron fiber of Tb (phen)L3/poly (methyl methacrylate) (PMMA) was successfully prepared by electrospinning using ethyl acetate (EA) and N,N-dimethyl-formamide (DMF) as the solvent. The influence of collector distance, feed rate, applied voltage and the proportion of EA/DMF on the morphology of the as-prepared fibers were discussed. Based on the researched results, the nanomicron fibers with glazed surface and uniform distribution were prepared. The fluorescent spectra indicate that the nanomicron fibers have good fluorescent properties.

This study focuses on the design and synthesis, thermal energy storage properties and thermal stability of a novel thermoplastic polyurethane solid–solid phase change material (PUSSPCM) for thermal energy storage. The PUSSPCM was synthesized via the two-step condensation reaction of 4,4'-diphenylmethane diisocyanate, polyethylene glycol and a novel tetrahydroxy compound (terephthalic acid bis-(2-hydroxy-1-hydroxymethyl-ethyl) ester) and characterized by Fourier transform infrared spectroscopy and 1 H nuclear magnetic resonance techniques. Thermal energy storage properties and thermal stability of as-synthesized PUSSPCM were also measured. DSC results indicate that the phase change temperatures and latent heats of the as-synthesized PUSSPCM are in the ranges of 22.4–48.4 °C and 143.9–153.5 J/g, respectively. TGA results confirm that the initial degradation temperature of the PUSSPCM is at 323 °C, which proves that PUSSPCM has good thermal stability. More significantly, the as-synthesized PUSSPCM can be directly melted and processed, and has a wide processing temperature range. Based on these results, it can be concluded that the synthesized PUSSPCM, as a novel phase change material (PCM), has significant energy storage potential due to its suitable phase change temperatures, higher latent heats, good thermal stability and processing performances.