Beyond MoS2 as the first transition metal dichalcogenide (TMD) to have gained recognition as an efficient catalyst for the hydrogen evolution reaction (HER), interest in other TMD nanomaterials is steadily beginning to proliferate. This is particularly true in the field of electrochemistry, with a myriad of emerging applications ranging from catalysis to supercapacitors and solar cells. Despite this rise, current understanding of their electrochemical characteristics is especially lacking. We therefore examine the inherent electroactivities of various chemically exfoliated TMDs (MoSe2, WS2, WSe2) and their implications for sensing and catalysis of the hydrogen evolution and oxygen reduction reactions (ORR). The TMDs studied are found to possess distinctive inherent electroactivities and together with their catalytic effects for the HER are revealed to strongly depend on the chemical exfoliation route and metal-to-chalcogen composition particularly in MoSe2. Despite its inherent activity exhibiting large variations depending on the exfoliation procedure, it is also the most efficient HER catalyst with a low overpotential of -0.36 V vs RHE (at 10 mA cm(-2) current density) and fairly low Tafel slope of ∼65 mV/dec after BuLi exfoliation. In addition, it demonstrates a fast heterogeneous electron transfer rate with a k0obs of 9.17×10(-4) cm s(-1) toward ferrocyanide, better than that seen for conventional glassy carbon electrodes. Knowledge of TMD electrochemistry is essential for the rational development of future applications; inherent TMD activity may potentially limit certain purposes, but intended objectives can nonetheless be achieved by careful selection of TMD compositions and exfoliation methods.

Doping of graphene with heteroatoms is an effective way to tailor its properties. Here we describe a simple and scalable method of doping graphene lattice with sulfur atoms during the thermal exfoliation process of graphite oxides. The graphite oxides were first prepared by Staudenmaier, Hofmann, and Hummers methods followed by treatments in hydrogen sulfide, sulfur dioxide, or carbon disulfide. The doped materials were characterized by scanning electron microscopy, high-resolution X-ray photoelectron spectroscopy, combustible elemental analysis, and Raman spectroscopy. The ζ-potential and conductivity of sulfur-doped graphenes were also investigated in this paper. It was found that the level of doping is more dramatically influenced by the type of graphite oxide used rather than the type of sulfur-containing gas used during exfoliation. Resulting sulfur-doped graphenes act as metal-free electrocatalysts for an oxygen reduction reaction.

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Graphene quantum dots is a class of graphene nanomaterials with exceptional luminescence properties. Precise dimension control of graphene quantum dots produced by chemical synthesis methods is currently difficult to achieve and usually provides a range of sizes from 3 to 25 nm. In this work, fullerene C60 is used as starting material, due to its well-defined dimension, to produce very small graphene quantum dots (∼2-3 nm). Treatment of fullerene C60 with a mixture of strong acid and chemical oxidant induced the oxidation, cage-opening, and fragmentation processes of fullerene C60. The synthesized quantum dots were characterized and supported by LDI-TOF MS, TEM, XRD, XPS, AFM, STM, FTIR, DLS, Raman spectroscopy, and luminescence analyses. The quantum dots remained fully dispersed in aqueous suspension and exhibited strong luminescence properties, with the highest intensity at 460 nm under a 340 nm excitation wavelength. Further chemical treatments with hydrazine hydrate and hydroxylamine resulted in red- and blue-shift of the luminescence, respectively.

Nanoarchitectonics on graphene implicates a specific and exact anchoring of molecules or nanoparticles onto the surface of graphene. One such example of an effective anchoring group that is highly reactive is the halogen moiety. Herein we describe a simple and scalable method for the introduction of halogen (chlorine, bromine, and iodine) moieties onto the surface of graphene by thermal exfoliation/reduction of graphite oxide in the corresponding gaseous halogen atmosphere. We characterized the halogenated graphene by using various techniques, including scanning and transmission electron microscopy, Raman spectroscopy, high-resolution X-ray photoelectron spectroscopy, and electrochemistry. The halogen atoms that have successfully been attached to the graphene surfaces will serve as basic building blocks for further graphene nanoarchitectonics.

Background Drosophila melanogaster is a chill-susceptible insect. Previous studies on this fly focused on acute direct chilling injury during cold shock and showed that lower lethal temperature (LLT, approximately −5°C) exhibits relatively low plasticity and that acclimations, both rapid cold hardening (RCH) and long-term cold acclimation, shift the LLT by only a few degrees at the maximum.Principal FindingsWe found that long-term cold acclimation considerably improved cold tolerance in fully grown third-instar larvae of D. melanogaster. A comparison of the larvae acclimated at constant 25°C with those acclimated at constant 15°C followed by constant 6°C for 2 d (15°C→6°C) showed that long-term cold acclimation extended the lethal time for 50% of the population (Lt50) during exposure to constant 0°C as much as 630-fold (from 0.137 h to 86.658 h). Such marked physiological plasticity in Lt50 (in contrast to LLT) suggested that chronic indirect chilling injury at 0°C differs from that caused by cold shock. Long-term cold acclimation modified the metabolomic profiles of the larvae. Accumulations of proline (up to 17.7 mM) and trehalose (up to 36.5 mM) were the two most prominent responses. In addition, restructuring of the glycerophospholipid composition of biological membranes was observed. The relative proportion of glycerophosphoethanolamines (especially those with linoleic acid at the sn-2 position) increased at the expense of glycerophosphocholines.ConclusionThird-instar larvae of D. melanogaster improved their cold tolerance in response to long-term cold acclimation and showed metabolic potential for the accumulation of proline and trehalose and for membrane restructuring.

Escalation (macroevolutionary increase) or divergence (disparity between relatives) in trait values are two frequent outcomes of the plant-herbivore arms race. We studied the defences and caterpillars associated with 21 sympatric New Guinean figs. Herbivore generalists were concentrated on hosts with low protease and oxidative activity. The distribution of specialists correlated with phylogeny, protease and trichomes. Additionally, highly specialised Asota moths used alkaloid rich plants. The evolution of proteases was conserved, alkaloid diversity has escalated across the studied species, oxidative activity has escalated within one clade, and trichomes have diverged across the phylogeny. Herbivore specificity correlated with their response to host defences: escalating traits largely affected generalists and divergent traits specialists; but the effect of escalating traits on extreme specialists was positive. In turn, the evolution of defences in Ficus can be driven towards both escalation and divergence in individual traits, in combination providing protection against a broad spectrum of herbivores.

SummaryTarget metabolic and large-scale transcriptomic analyses of tobacco (Nicotiana tabacum L.) Bright Yellow-2 (BY-2) cells were employed to identify novel gene(s) involved in methyl jasmonate (MJ)-dependent function in plants. At the metabolic level, we describe the specific accumulation of several phenylpropanoid-polyamine conjugates in MJ-treated BY-2 cells. Furthermore, global gene expression analysis of MJ-treated cells using a 16K cDNA microarray containing expressed sequence tags (ESTs) from BY-2 cells revealed 828 genes that were upregulated by MJ treatment within 48 h. Using time-course expression data we identified a novel MJinducible R2R3 MYB-type transcription factor (NtMYBJS1) that was co-expressed in a close temporal pattern with the core phenylpropanoid genes phenylalanine ammonia-lyase (PAL) and 4-coumarate:CoA ligase (4CL). Overexpression of NtMYBJS1 in tobacco BY-2 cells caused accumulation of specific phenylpropanoid conjugates in the cells. Subsequent microarray analysis of NtMYBJS1 transgenic lines revealed that a limited number of genes, including PAL and 4CL, were specifically induced in the presence of the NtMYBJS1 transgene. These results, together with results of both antisense expression analysis and of gel mobility shift assays, strongly indicate that the NtMYBJS1 protein functions in tobacco MJ signal transduction, inducing phenylpropanoid biosynthetic genes and the accumulation of phenylpropanoid-polyamine conjugates during stress.