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Chemical evolution

Shasha Tao, Florent Yang, Jona Schuch, Wolfram Jaegermann, Bernhard Kaiser
Ni Nanoparticles (NPs) consisting of Ni, NiO and Ni(OH)2 have been formed on Ti substrates by electrodeposition as electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solution. The deposition parameters including the potential range and the scan rate were varied, and the resulting NPs were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. Additionally, the chemical composition of the NPs changes using different conditions, and it was found that the catalytic activity increases with an increasing amount of NiO...
December 11, 2017: ChemSusChem
Ol'ha O Brovarets', Ivan S Voiteshenko, Dmytro M Hovorun
This study is intended to clarify in detail the tautomeric transformations of the wobble (w) G*·2AP(w) and A·2AP(w) nucleobase mispairs involving 2-aminopurine (2AP) into the Watson-Crick (WC) G·2AP(WC) and A*·2AP(WC) base mispairs (asterisks denote mutagenic tautomers of the DNA bases), respectively, by quantum-mechanical methods and Bader's Quantum Theory of Atoms in Molecules. Our previously reported methodology has been used, which allows the evolution of the physico-chemical parameters to be tracked along the entire internal reaction coordinate (IRC), not exclusively in the stationary states of these reactions...
December 11, 2017: Physical Chemistry Chemical Physics: PCCP
Ruiqin Gao, Guangtao Yu, Wei Chen, Guo-Dong Li, Shuang Gao, Zengsong Zhang, Xiaopeng Shen, Xuri Huang, Xiaoxin Zou
The hydrogen evolution reaction (HER) is involved in energy-intensive water- and chlor-alkali electrolyzers, and thus, highly active and stable HER electrocatalysts in alkaline media are needed. Titanates, a family of representative two-dimensional materials with negatively charged main layers, are chemically and structurally stable under strongly basic conditions, but they have never been shown to have electrocatalytic activity for HER. Herein, we report that intercalating 3d metal cations, including Fe3+, Co2+, Ni2+ and Cu2+ ions, into the interlayer regions of titanates yields efficient and robust electrocatalysts for the alkaline HER...
December 11, 2017: ACS Applied Materials & Interfaces
Cheng Tang, Ling Zhong, Bingsen Zhang, Hao-Fan Wang, Qiang Zhang
The emergence of van der Waals (vdW) heterostructures of 2D materials has opened new avenues for fundamental scientific research and technological applications. However, the current concepts and strategies of material engineering lack feasibilities to comprehensively regulate the as-obtained extrinsic physicochemical characters together with intrinsic properties and activities for optimal performances. A 3D mesoporous vdW heterostructure of graphene and nitrogen-doped MoS2 via a two-step sequential chemical vapor deposition method is constructed...
December 11, 2017: Advanced Materials
Matthias Erb
Many morphological and chemical features of plants are classified as plant defenses against herbivores. By definition, plant defenses should increase a plant's fitness (i.e., its contribution to the gene pool of the next generation) as a function of herbivory. Over the past years, substantial progress has been made in understanding and manipulating the mechanistic basis of many putative plant defense traits. However, most plant defenses are still characterized by proximate variables such as herbivore performance or plant damage rather than actual fitness...
December 6, 2017: Trends in Plant Science
Kenneth R Olson, Yan Gao, Faihaan Arif, Kanika Arora, Shivali Patel, Eric R DeLeon, Thomas R Sutton, Martin Feelisch, Miriam M Cortese-Krott, Karl D Straub
Reactive sulfur species (RSS) such as H2S, HS•, H2Sn, (n = 2-7) and HS2•- are chemically similar to H2O and the reactive oxygen species (ROS) HO•, H2O2, O2•- and act on common biological effectors. RSS were present in evolution long before ROS, and because both are metabolized by catalase it has been suggested that "antioxidant" enzymes originally evolved to regulate RSS and may continue to do so today. Here we examined RSS metabolism by Cu/Zn superoxide dismutase (SOD) using amperometric electrodes for dissolved H2S, a polysulfide-specific fluorescent probe (SSP4), and mass spectrometry to identify specific polysulfides (H2S2-H2S5)...
November 20, 2017: Redox Biology
Hao Xu, Dongsheng Dai, Songsong Li, Lei Ge, Yangqin Gao
Semiconductor-based photocatalytic hydrogen evolution from water with earth-abundant and low cost co-catalysts has attracted much attention. Herein, novel Cu2(OH)2CO3 decorated 2D TiO2 nanosheets for photocatalytic water splitting were synthesized by a facile in situ synthetic method. The chemical and photophysical properties of Cu2(OH)2CO3/TiO2 nanosheets were investigated by X-ray diffractometry (XRD), transmission electron microscopy (TEM), UV-vis diffusion reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) analysis...
December 7, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Jheng-Yi Li, Chia-Hsiang Hung, Chia-Yun Chen
Metal-assisted chemical etching (MaCE) has been widely employed for the fabrication of regular silicon (Si) nanowire arrays. These features were originated from the directional etching of Si preferentially along <100> orientations through the catalytic assistance of metals, which could be gold, silver, platinum or palladium. In this study, the dramatic modulation of etching profiles toward pyramidal architectures was undertaken by utilizing copper as catalysts through a facile one-step etching process, which paved the exceptional way on the texturization of Si for advanced photovoltaic applications...
December 7, 2017: Scientific Reports
Sayoko Ito-Harashima, Takashi Yagi
The high-fidelity transmission of genetic information is crucial for the survival of organisms, the cells of which have the ability to protect DNA against endogenous and environmental agents, including reactive oxygen species (ROS), ionizing radiation, and various chemical compounds. The basis of protection mechanisms has been evolutionarily conserved from yeast to humans; however, each organism often has a specialized mode of regulation that uses different sets of machineries, particularly in lower eukaryotes...
2017: Genes and Environment: the Official Journal of the Japanese Environmental Mutagen Society
Biao Chen, Yuhuan Meng, Junwei Sha, Cheng Zhong, Wenbin Hu, Naiqin Zhao
The rapidly increasing severity of the energy crisis and environmental degradation are stimulating the rapid development of photocatalysts and rechargeable lithium/sodium ion batteries. In particular, MoS2/TiO2 based nanocomposites show great potential and have been widely studied in the areas of both photocatalysis and rechargeable lithium/sodium ion batteries due to their superior combination properties. In addition to the low-cost, abundance, and high chemical stability of both MoS2 and TiO2, MoS2/TiO2 composites also show complementary advantages...
December 6, 2017: Nanoscale
Jiratheep Pruchyathamkorn, Minjun Yang, Hatem M A Amin, Christopher Batchelor-McAuley, Richard G Compton
By varying the total and the relative concentrations of a strong acid (HClO4) and a pH sensitive fluorescent dye (8-hydroxypyrene-1,3,6-trisulfonate), this work demonstrates that both the hydrogen evolution reaction (HER) or the oxygen reduction reaction (ORR) can be selectively and optically studied at an electrochemical interface. The local pH shift driven by the redox reaction can be visualised through fluorescence imaging of the interface. The use of finite strong acid concentrations further serves to constrain the pH change to a thin-layer adjacent to the surface...
December 6, 2017: Journal of Physical Chemistry Letters
Surya Vamsi Devaguptapu, Sooyeon Hwang, Stavros Karakalos, Shuai Zhao, Shiva Gupta, Dong Su, Hui Xu, Gang Wu
Spinel NiCo2O4 is considered a promising precious metal-free catalyst that is also carbon-free for oxygen electrocatalysis. Current efforts mainly focus on optimal chemical doping and substituent to tune its electronic structures for enhanced activity. Here, we study its morphology control and elucidate the morphology-dependent catalyst performance for bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Three types of NiCo2O4 catalysts with significantly distinct morphologies were prepared using temple-free, Pluronic-123 (P-123) soft, and SiO2 hard templates, respectively, via hydrothermal methods following by a calcination...
December 6, 2017: ACS Applied Materials & Interfaces
Anselme F E Borgeaud, Kenji Kawai, Kensuke Konishi, Robert J Geller
D″ (Dee double prime), the lowermost layer of the Earth's mantle, is the thermal boundary layer (TBL) of mantle convection immediately above the Earth's liquid outer core. As the origin of upwelling of hot material and the destination of paleoslabs (downwelling cold slab remnants), D″ plays a major role in the Earth's evolution. D″ beneath Central America and the Caribbean is of particular geodynamical interest, because the paleo- and present Pacific plates have been subducting beneath the western margin of Pangaea since ~250 million years ago, which implies that paleoslabs could have reached the lowermost mantle...
November 2017: Science Advances
J Miot, S Bernard, M Bourreau, F Guyot, A Kish
Burial is generally detrimental to the preservation of biological signals. It has often been assumed that (bio)mineral-encrusted microorganisms are more resistant to burial-induced degradation than non-encrusted ones over geological timescales. For the present study, we submitted Sulfolobus acidocaldarius experimentally encrusted by amorphous Fe phosphates to constrained temperature conditions (150 °C) under pressure for 1 to 5 days, thereby simulating burial-induced processes. We document the molecular and mineralogical evolution of these assemblages down to the sub-micrometer scale using X-ray diffraction, scanning and transmission electron microscopies and synchrotron-based X-ray absorption near edge structure spectroscopy at the carbon K-edge...
December 5, 2017: Scientific Reports
Sandra Steiger, Johannes Stökl
Effective parental care requires recognition and communication processes. Whereas chemical communication has been studied intensively in eusocial organisms, in which the workers (siblings) predominantly provide brood care, insect groups in which parents engage in care have been largely neglected. However, the study of communication in insect families might complement and enhance our understanding not only of the evolution of signaling process involved in social insects, but also of those involved in vertebrate families...
December 2017: Current Opinion in Insect Science
Jessica Henneken, Therésa M Jones
Insects utilise chemical cues for a range of different purposes and the complexity and degree of specificity of these signals is arguably unparalleled in the animal kingdom. Chemical signals are particularly important for insect reproduction and the selective pressures driving their evolution and maintenance have been the subject of previous reviews. However, the world in which chemical cues evolved and are maintained is changing at an unprecedented rate. How (or indeed whether) chemical signals used in sexual selection will respond is largely unknown...
December 2017: Current Opinion in Insect Science
Johannes Stökl, Sandra Steiger
Communication via chemical signals, that is, pheromones, is of pivotal importance for most insects. According to current evolutionary theory, insect pheromones originated either from extant precursor compounds being selected for information transfer or by the pheromone components exploiting a pre-existing sensory bias in the receiver. Here, we review the available experimental evidence for both hypotheses. Existing data indicate that most insect pheromones evolved from precursor compounds that were emitted as metabolic by-products or that previously had other non-communicative functions...
December 2017: Current Opinion in Insect Science
Matilda S Newton, Vickery L Arcus, Monica L Gerth, Wayne M Patrick
Enzymes have been evolving to catalyze new chemical reactions for billions of years, and will continue to do so for billions more. Here, we review examples in which evolutionary biochemists have used big data and high-throughput experimental tools to shed new light on the enormous functional diversity of extant enzymes, and the evolutionary processes that gave rise to it. We discuss the role that gene loss has played in enzyme evolution, as well as the more familiar processes of gene duplication and divergence...
December 2, 2017: Current Opinion in Structural Biology
Han Ye, Jiadong Zhou, Dequan Er, Chris Price, Zhongyuan Yu, Yumin Liu, John S Lowengrub, Jun Lou, Zheng Liu, Vivek B Shenoy
Vertical stacking of monolayers via van der Waals (vdW) interaction opens promising routes toward engineering physical properties of two-dimensional (2D) materials and designing atomically thin devices. However, due to the lack of mechanistic understanding, challenges remain in the controlled fabrication of these structures via scalable methods such as chemical vapor deposition (CVD) onto substrates. In this paper, we develop a general multiscale model to describe the size evolution of 2D layers and predict the necessary growth conditions for vertical (initial + subsequent layers) versus in-plane lateral (monolayer) growth...
December 5, 2017: ACS Nano
Victor A Lorenz-Fonfria, Mattia Saita, Tzvetana Lazarova, Ramona Schlesinger, Joachim Heberle
Infrared spectroscopy has been used in the past to probe the dynamics of internal proton transfer reactions taking place during the functional mechanism of proteins but has remained mostly silent to protonation changes in the aqueous medium. Here, by selectively monitoring vibrational changes of buffer molecules with a temporal resolution of 6 µs, we have traced proton release and uptake events in the light-driven proton-pump bacteriorhodopsin and correlate these to other molecular processes within the protein...
December 4, 2017: Proceedings of the National Academy of Sciences of the United States of America
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