Brown Planthopper (N. lugens Stal) Feeding Behaviour on Rice Germplasm as an Indicator of Resistance

BACKGROUND: The brown planthopper (BPH) Nilaparvata lugens (Stal) is a serious pest of rice in Asia. Development of novel control strategies can be facilitated by comparison of BPH feeding behaviour on varieties exhibiting natural genetic variation, and then elucidation of the underlying mechanisms of resistance. METHODOLOGY/PRINCIPAL FINDINGS: BPH feeding behaviour was compared on 12 rice varieties over a 12 h period using the electrical penetration graph (EPG) and honeydew clocks. Seven feeding behaviours (waveforms) were identified and could be classified into two phases. The first phase involved patterns of sieve element location including non penetration (NP), pathway (N1+N2+N3), xylem (N5) [21] and two new feeding waveforms, derailed stylet mechanics (N6) and cell penetration (N7). The second feeding phase consisted of salivation into the sieve element (N4-a) and sieve element sap ingestion (N4-b). Production of honeydew drops correlated with N4-b waveform patterns providing independent confirmation of this feeding behaviour. CONCLUSIONS/SIGNIFICANCE: Overall variation in feeding behaviour was highly correlated with previously published field resistance or susceptibility of the different rice varieties: BPH produced lower numbers of honeydew drops and had a shorter period of phloem feeding on resistant rice varieties, but there was no significant difference in the time to the first salivation (N4-b). These qualitative differences in behaviour suggest that resistance is caused by differences in sustained phloem ingestion, not by phloem location. Cluster analysis of the feeding and honeydew data split the 12 rice varieties into three groups: susceptible, moderately resistant and highly resistant. The screening methods that we have described uncover novel aspects of the resistance mechanism (or mechanisms) of rice to BPH and will in combination with molecular approaches allow identification and development of new control strategies

A Highly Effective, Stable Oxygen Evolution Catalyst Derived from Transition Metal Selenides and Phosphides

Recently, transition metal chalcogenides and phosphides have been increasingly reported as efficient and stable oxygen evolution reaction (OER) catalysts in alkaline medium, despite the fact that they are thermodynamically unstable under highly oxidative potentials. Here the active forms of these materials are elucidated by synthesizing a hybrid catalyst, which has a metal chalcogenide in the form of CoSe2 and metal phosphide in the form of CoP—CoSe2|CoP. Both CoSe2 and CoP in the as-prepared catalyst are completely transformed into their respective oxyhydroxides and hydroxides, which are, in fact, the true OER-active species in alkaline medium and not the selenide and phosphide themselves. The derived oxides from the hybrid catalyst deliver an excellent OER activity by reaching a current density of 10 mA cm−2 at a low overpotential of 240 mV (vs reversible hydrogen electrode (RHE)) and a Tafel slope of 46.6 mV dec−1. The stability of the derived oxyhydroxide/hydroxide catalyst shows no appreciable deactivation during 120 h of continuous electrolysis, displaying an extraordinary operational stability

Electrodeposition of Unary Oxide on a Bimetallic Hydroxide as a Highly Active and Stable Catalyst for Water Oxidation

For industrial-scale water electrolysis, development of a highly stable and active oxygen evolution reaction (OER) electrocatalyst is highly demanded. In this study, we report an efficient OER electrocatalyst of CeOx (unary oxide) and NiFe-OH (bimetallic hydroxide) electrochemically deposited on a macroporous nickel foam substrate. The synthesized electrocatalyst exhibits remarkably improved OER performance by reaching a current density of 100 mA cm-2 at a low overpotential of 280 mV, which is quite superior to that of most of the previously reported non-noble-metal-based OER electrocatalysts. Furthermore, the developed catalyst demonstrated a minor Tafel slope of 43.2 mV dec-1 with good stability under a large current at a continuous operation of 80 000 s in a strong alkaline electrolyte. Experimental observations revealed that the combination of CeOx and NiFe-OH accelerates the electroadsorption energies between the electrocatalyst surface and oxygen intermediates, considerably contributing to the OER enhancement. These results undoubtedly represent an important milestone toward the development of efficient OER electrocatalysts for applications as industrial water electrolyzers

2D Organic–Inorganic Hybrid Thin Films for Flexible UV–Visible Photodetectors

Flexible 2D inorganic MoS2 and organic g-C3N4 hybrid thin film photodetectors with tunable composition and photodetection properties are developed using simple solution processing. The hybrid films fabricated on paper substrate show broadband photodetection suitable for both UV and visible light with good responsivity, detectivity, and reliable and rapid photoswitching characteristics comparable to monolayer devices. This excellent performance is retained even after the films are severely deformed at a bending radius of ≈2 mm for hundreds of cycles. The detailed charge transfer and separation processes at the interface between the 2D materials in the hybrid films are confirmed by femtosecond transient absorption spectroscopy with broadband capability

High throughput modification of chemically reduced graphene oxides by a conjugated block copolymer in non-polar medium

We present a simple, but robust route to efficiently disperse very high rGO concentrations of chemically reduced graphene oxides (rGOs) in various non-polar solvents and polymers. Our method is based on the noncovalent, nondestructive modification of rGOs with a conjugated block copolymer, poly(styrene-block-paraphenylene) (PS-b-PPP). The dispersion of rGOs occurred because PPP blocks strongly adhered to basal planes of rGOs by π-π interactions, while PS blocks provided good solubility in a variety of non-polar environments. The resulting PS-b-PPP modified rGOs (PMrGOs) showed excellent solubility and dispersion stability that was dependent on the quality of the solvent with respect to the PS blocks. In particular, extremely high solubility of the rGOs, as high as 1.5 mg mL-1, was achieved in THF. Our PMrGOs and their solution blends with other non-polymer polymers such as PS, poly(methylmethacrylate) and poly(isoprene-block-styrene) were conveniently spin-coated on various substrates, giving rise to ultra-thin nanohybrid films where the amount of rGO can be systematically controlled. The scalable and simple strategy employed for fabricating rGO nanohybrid films allowed us to assemble a high performance non-volatile resistive polymer memory device in which the bias-dependent trapping and de-trapping of injected charges were efficiently manipulated on the surface of highly dispersed rGO sheets in the nanohybrid. © 2012 The Royal Society of Chemistry

Metal Halide Perovskite and Phosphorus Doped g-C<inf>3</inf>N<inf>4</inf> Bulk Heterojunctions for Air-Stable Photodetectors

In this work, we fabricate photodetectors made of methylammonium lead trihalide perovskite (MLHP) and phosphorus-doped graphitic carbon nitride nanosheets (PCN-S). Using thermal polymerization, PCN-S with a reduced band gap, are synthesized from low-cost precursors, making it feasible to form type-II bulk heterojunctions with perovskites. Owing to the bulk heterojunctions between PCN-S and MLHP, the dark current of the photodetectors significantly decreases from ∼10-9 A for perovskite-only devices to ∼10-11 A for heterojunction devices. As a result, not only does the on/off ratio of the hybrid devices increase from 103 to 105 but also the photodetectivity is enhanced by more than 1 order of magnitude (up to 1013 Jones) and the responsivity reaches a value of 14 A W-1. Moreover, the hybridization of MLHP with PCN-S significantly modifies the hydrophilicity and morphology of the perovskite films, which dramatically increases their stability under ambient conditions. The hybrid photodetectors, described here, present a promising new direction toward stable and efficient optoelectronic applications

High performance, 3D-hierarchical CoS<inf>2</inf>/CoSe@C nanohybrid as an efficient electrocatalyst for hydrogen evolution reaction

Electrolysis, driven by renewables, is ideally a direct and clean route to generate the hydrogen. However, for the efficient H2 generation designing active, stable and low cost electrocatalyst system to replace expensive Pt is of paramount importance. Here, a hetero-structured system composed of CoS2 and CoSe nanostructures on carbon matrix (CoS2/CoSe@C) is proposed as an active electrocatalyst for hydrogen evolution reaction (HER) in acid medium. The composition of sulfur and selenium in the derived CoS2/CoSe@C electrocatalyst is analytically controlled for the enhanced HER performance. The prepared electrocatalyst offers the low overpotential of 164 mV at the current density of 10 mA cm−2 with a small Tafel slope of 42 mV dec−1 as a result of proper synergy between the active components CoS2 and CoSe. Moreover, the interconnected network in the carbon matrix of CoS2/CoSe@C provides better conductivity ensured by adequate contact area between the electrocatalyst and electrolyte. Besides the convincing electrochemical activity, catalyst demonstrates the good stability for at least 10 h. This work highlights importance of composite materials for HER via synchronizing catalytically active materials (Ni, Co, Mo) and highly conductive supports (CNT, C, rGO)

Thin reduced graphene oxide interlayer with a conjugated block copolymer for high performance non-volatile ferroelectric polymer memory

Polymer ferroelectric-gate field effect transistors (Fe-FETs) employing ferroelectric polymer thin films as gate insulators are highly attractive as a next-generation non-volatile memory. For minimizing gate leakage current of a device which arises from electrically defective ferroelectric polymer layer in particular at low operation voltage, the materials design of interlayers between the ferroelectric insulator and gate electrode is essential. Here, we introduce a new solution-processed interlayer of conductive reduced graphene oxides (rGOs) modified with a conjugated block copolymer, poly(styrene-block- paraphenylene) (PS-b-PPP). A FeFET with a solution-processed p-type oligomeric semiconducting channel and ferroelectric poly(vinylidene fluoride-co- trifluoroethylene) (PVDF-TrFE) insulator exhibited characteristic source-drain current hysteresis arising from ferroelectric polarization switching of a PVDF-TrFE insulator. Our PS-b-PPP modified rGOs (PMrGOs) with conductive moieties embedded in insulating polymer matrix not only significantly reduced the gate leakage current but also efficiently lowered operation voltage of the device. In consequence, the device showed large memory gate voltage window and high ON/OFF source-drain current ratio with excellent data retention and read/write cycle endurance. Furthermore, our PMrGOs interlayers were successfully employed to FeFETs fabricated on mechanically flexible substrates with promising non-volatile memory performance under repetitive bending deformation. © 2014 Elsevier B.V. All rights reserved