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Photocatalytic degradation is one of the most promising emerging technologies for environmental pollution control. However, the preparation of efficient, low-cost photocatalysts still faces many challenges. TiO2 is a widely available and inexpensive photocatalyst material, but improving its catalytic degradation performance has posed a significant challenge due to its shortcomings, such as the easy recombination of its photogenerated electron–hole pairs and its difficulty in absorbing visible light. The construction of homogeneous heterojunctions is an effective means to enhance the photocatalytic performances of photocatalysts. In this study, a TiO2(B)/TiO2(A) homogeneous heterojunction composite photocatalyst (with B and A denoting bronze and anatase phases, respectively) was successfully constructed in situ. Although the construction of homogeneous heterojunctions did not improve the light absorption performance of the material, its photocatalytic degradation performance was substantially enhanced. This was due to the suppression of the recombination of photogenerated electron–hole pairs and the enhancement of the carrier mobility. The photocatalytic ability of the TiO2(B)/TiO2(A) homogeneous heterojunction composite photocatalyst was up to three times higher than that of raw TiO2 (pure anatase TiO2). [ABSTRACT FROM AUTHOR]

Abstract: Few-layered ReS2 two-dimensional (2D) semiconductor nanosheets directly nucleated and grown on reduced graphene oxide (RGO) were synthesized through a facile hydrothermal method. Compared with bare ReS2, the ReS2/RGO hybrid delivers much better electrocatalytic activity for hydrogen evolution reaction (HER) in acidic media. It exhibits a lower Tafel slope of 107.4 mV·dec−1 and a larger current density of − 5.2 mA·cm−2 at − 250 mV (vs. RHE), compared with ReS2 (152.7 mV·dec−1, − 3.1 mA·cm−2). The ReS2/RGO hybrid has a unique architecture constructed by highly conductive and porous RGO internetworks, which guarantees easy electrolyte infiltration and efficient charge transfer and provides sufficient active edge sites, resulting in enhanced HER performance. The present synthesis approach can be extended to synthesize other 2D-semiconductor-based composites for energy storage and catalytic devices.Graphical abstract: [ABSTRACT FROM AUTHOR]

Effects of the interstitial carbon atoms on the magnetic properties, especially on the magnetic entropy change, of the LaFe[SUB11.5]Si[SUB1.5] compound, have been studied. X-ray diffraction patterns reveal a monotonous increase of the lattice constant with the concentration of carbon, while the cubic NaZn[SUB13]-type structure remains unchanged. The Curie temperatures T[SUBC] of LaFe[SUB11.5]Si[SUB1.5]C[SUBy] are ∼ 195, 225, and 241 K for y = 0, 0.2, and 0.5, respectively, increasing with the increase of carbon concentration. The maximal magnetic entropy changes ‖ΔS‖ of LaFe [SUB11.5]Si[SUB1.5]C[SUBy] at the respective T[SUBC] under a magnetic field change of 0-5 T are ∼24.6, ∼22.8, and ∼12.7 J/kg K for y50, 0.2, and 0.5, respectively, notably exceeding that of Gd (‖ΔS‖ ∼9.8 J/kg K at T[SUBC] = 293 K). The ‖ΔS‖ of LaFe[SUB11.5]Si[SUB1.5]C[SUB0.2] is nearly as giant as that of the parent alloy LaFe[SUB11.5]Si[SUB1.5] due to the first-order field-induced itinerant-electron metamagnetic transition that occurs in both compounds clearly observed for the LaFe[SUB11.5]Si[SUB1.5]C[SUB0.5] compound. With the increase of carbon concentration, the nature of magnetic transition has been changed from first order to second order, which results in the significant decrease of the magnetic entropy change. The large ‖ΔS‖, convenient adjustment of T[SUBC] and relatively low cost make the LaFe[SUB11.5]Si[SUB1.5]C[SUBy] interstitial compounds promising candidates for magnetic refrigerants in the corresponding temperature range. [ABSTRACT FROM AUTHOR]

Chemically stable LaFe[sub 11.6]Si[sub 1.4]C[sub x] (x = 0-0.6) interstitial compounds were prepared. The Curie temperatures increases from 195 to 250 K with an increase in X from 0 to 0.6 due to obvious lattice expansion. The maximal magnetic entropy changes ΔAS with a change in magnetic field of 0-5 T, are 24.8, 24.2, 18.8 and 12.1 J/kg K for x = 0, 0.2, 0.4, and 0.6, respectively, notably exceeding that of Gd (ΔS∼ 9.8 J/kg K at T[sub C] = 293 K). The magnetic transition varies from first order to second order with an increase in carbon concentration, which has a decisive influence on ΔS. The large ΔA, chemical stability, and low cost make LaFe[sub 11.4]Si[sub l.6]C[sub x] a promising candidate as a magnetic refrigerant in the corresponding temperature ranges. [ABSTRACT FROM AUTHOR]

Providing reliable communication represents one of the major barriers to wireless sensor networks. In this paper, we propose a fault-tolerant tableless routing protocol called E-cube+, inspired from e-cube routing protocol, to support intelligent rerouting. A range of fault-tolerant routing properties of E-cube+ (such as loop-freeness, failure recovery guarantees, and bounded latency) have been derived and analyzed. Experiment results also show that E-cube+ is able to route data properly without complicated and energy-intensive routing table lookup processes even when node failures occur. [ABSTRACT FROM AUTHOR]

Photoelectrical response characteristics of epitaxial graphene (EG) films on Si- and C-terminated 6H-SiC, and transferred chemical vapor deposition (CVD) graphene films on Si-terminated 6H-SiC have been investigated. The results show that upon illumination by a xenon lamp, the photocurrent of EG grown on Si-terminated SiC significantly increases by 147.6%, while the photocurrents of EG grown on C-terminated SiC, and transferred CVD graphene on Si-terminated SiC slightly decrease by 0.5% and 2.7%, respectively. The interfacial buffer layer between EG and Si-terminated 6H-SiC is responsible for the significant photoelectrical response of EG. Its strong photoelectrical response makes it promising for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Platinum nanoparticles (PtNPs)/graphene composite materials are synthesized by a controlled chemical reduction of H2PtCl6 on graphene sheets. The electrocatalytic activity of a PtNPs/graphene composite counter electrode for a dye-sensitized solar cell (DSSC) is investigated. The results demonstrate that the PtNPs/graphene composite has high electrocatalytic activity for the dye-sensitized solar cell. The cell employing PtNPs (1.6 wt%)/graphene counter electrode reaches an conversion efficiency (ŋ) of 3.89% upon the excitation of 100 mW/cm2 AM 1.5 white light, which is comparable to that of the cell with a Pt-film counter electrode (ŋ = 3:76%). It suggests that one can use only 14% Pt content of the conventional Pt-film counter electrode to obtain a comparable conversion efficiency. It may be possible to obtain a high performance DSSC using the PtNPs/graphene composite with a very low Pt content as a counter electrode due to its simplicity, low cost, and large scalability. [ABSTRACT FROM AUTHOR]

Epitaxial graphene is synthesized by silicon sublimation from the Si-terminated 6H-SiC substrate. The effects of graphitization temperature on the thickness and surface morphology of epitaxial graphene are investigated. X-ray photoelectron spectroscopy spectra and atomic force microscopy images reveal that the epitaxial graphene thickness increases and the epitaxial graphene roughness decreases with the increase in graphitization temperature. This means that the thickness and roughness of epitaxial graphene films can be modulated by varying the graphitization temperature. In addition, the electrical properties of epitaxial graphene film are also investigated by Hall effect measurement. [ABSTRACT FROM AUTHOR]

The effects of 60Co γ-ray irradiation on the DC characteristics of AlGaN/GaN enhancement-mode high-electronmobility transistors (E-mode HEMTs) are investigated. The results show that having been irradiated by 60Co γ-rays at a dose of 3 Mrad (Si), the E-mode HEMT reduces its saturation drain current and maximal transconductance by 6% and 5%, respectively, and significantly increases both forward and reverse gate currents, while its threshold voltage is affected only slightly. The obvious performance degradation of E-mode AlGaN/GaN HEMTs is consistent with the creation of electronegative surface state charges in the source-gate spacer and gate-drain spacer after being irradiated. [ABSTRACT FROM AUTHOR]

The morphology, crystalline structure of epitaxial heterostructures of Pb(Zr0.52Ti0.48)O3/La0.7Sr0.3MnO3 (PZT/LSMO) grown on single crystalline SrTiO3 substrates by pulse laser deposition (PLD), have been investigated. The morphology results show that the LSMO layers and PZT layers are smooth and homogenous. The crystalline structure measurements indicate that good epitaxial relationships between LSMO and PZT and STO were obtained. The effects of applied electric and magnetic fields on the physical properties of epitaxial perovskite ferroelectric/ferromagnetic heterostructures were investigated. The results show that the polarized electric field has a very significant influence on the transport properties of LSMO layers while has little influence on the magnetization, and the magnetic field has an obvious influence on the ferroelectric behavior of the PZT layer. [ABSTRACT FROM AUTHOR]

Graphene is a new promising candidate for application in radio-frequency (RF) electronics due to its excellent electronic properties such as ultrahigh carrier mobility, large threshold current density, and high saturation velocity. Recently, much progress has been made in the graphene-based RF field-effect transistors (RF-FETs). Here we present for the first time the high-performance top-gated RF transistors using millimeter-scale single graphene domain on a SiO2/Si substrate through a conventional microfabrication process. A maximum cut-off frequency of 178 GHz and a peak maximum oscillation frequency of 35 GHz are achieved in the graphene-domain-based FET with a gate length of 50 nm and 150 nm, respectively. This work shows that the millimeter-scale single graphene domain has great potential applications in RF devices and circuits. [ABSTRACT FROM AUTHOR]

Although there are already many efforts to investigate the electronic structures of twisted bilayer graphene, a definitive conclusion has not yet been reached. In particular, it is still a controversial issue whether a tunable electrical (or transport) bandgap exists in twisted bilayer graphene film until now. Herein, for the first time, it has been demonstrated that a tunable electrical bandgap can be opened in the twisted bilayer graphene by the combination effect of twist and vertical electrical fields. In addition, we have also developed a facile chemical vapor deposition method to synthesize large-area twisted bilayer graphene by introducing decaborane as the cocatalyst for decomposing methane molecules. The growth mechanism is demonstrated to be a defined-seeding and self-limiting process. This work is expected to be beneficial to the fundamental understanding of both the growth mechanism for bilayer graphene on Cu foil and more significantly, the electronic structures of twisted bilayer graphene.

For the first time, large-area CVD-grown graphene films transferred onto flexible PET substrates were used as transparent conductive electrodes in alternating current electroluminescence (ACEL) devices. The flexible ACEL device based on a single-layer graphene electrode has a turn-on voltage of 80 V; at 480 V (16 kHz), the luminance and luminous efficiency are 1140 cd/m(2) and 5.0 lm/W, respectively. The turn-on voltage increases and the luminance decreases with increasing stacked layers of graphene, which means the single-layer graphene is the best optimal choice as the transparent conductive electrode. Furthermore, it demonstrates that the graphene-based ACEL device is highly flexible and can work very well even under a very large strain of 5.4%, suggesting great potential applications in flexible optoelectronics., (© 2011 American Chemical Society)

Ultrathin AlN/GaN crystalline porous freestanding nanomembranes are fabricated on Si(111) by selective silicon etching, and self-assembled into various geometries such as tubes, spirals, and curved sheets. Nanopores with sizes from several to tens of nanometers are produced in nanomembranes of 20-35 nm nominal thickness, caused by the island growth of AlN on Si(111). No crystal-orientation dependence is observed while releasing the AlN/GaN nanomembranes from the Si substrate indicating that the driving stress mainly originates from the zipping effect among islands during growth. Competition between different relaxation mechanisms is experimentally revealed for different nanomembrane geometries and well-described by numerical calculations. The cathodoluminescence emission from GaN nanomembranes reveals a weak peak close to the GaN bandgap, which is dramatically enhanced by electron irradiation.