All‐Surface‐Atomic‐Metal Chalcogenide Sheets for High‐Efficiency Visible‐Light Photoelectrochemical Water Splitting

Artificial all‐surface‐atomic 2D sheets can trigger breakthroughs in tailoring the physical and chemical properties of advanced functional materials. Here, the conceptually new all‐surface‐atomic semiconductors of SnS and SnSe freestanding sheets are realized using a scalable strategy. As an example, all‐surface‐atomic SnS sheets undergo surface atomic elongation and structural disordering, which is revealed by X‐ray absorption fine structure spectroscopy and first‐principles calculations, endowing them with high structural stability and an increased density of states at the valence band edge. These exotic atomic and electronic structures make the all‐surface‐atomic SnS sheet‐based photoelectrode exhibit an incident photon‐to‐current conversion efficiency of 67.1% at 490 nm, much higher than the efficiencies of other visible‐light‐driven water splitting. A photocurrent density of 5.27 mA cm^‐2, which is two orders of magnitude higher than that of the bulk counterpart, is also achieved for the all‐surface‐atomic SnS sheets‐based photoelectrode. This will allow the manipulation of the basic properties of advanced materials on the atomic scale, thus paving the way for innovative applications.     

Developments and Perspectives in 3d Transition‐Metal‐Based Electrocatalysts for Neutral and Near‐Neutral Water Electrolysis

Technology for producing highly pure hydrogen (99.999%) by water electrolysis is a field of importance in terms of the planets' current energy scenario. A much needed transition from a carbon economy to a hydrogen economy further adds importance to the field of hydrogen generation from water for a sustainable future. To avoid energy losses in the production process, the use of highly acidic (Proton Exchange Membrane (PEM) water electrolyzer) and alkaline (alkaline water electrolyzer) electrolytes is conventional practice in this field. Unfortunately, there are several other issues associated with the use of acidic and alkaline electrolytes such as the requirement of specific ion exchanging membranes with good stability, acid or alkali stable catalysts and corrosive environment withstanding cell stacks, etc. To overcome these issues, researchers have shown interest in the field of electrochemical water splitting in neutral and near‐neutral conditions. In this review, the chronological development of 3d transition‐metal‐based electrocatalysts for neutral and near‐neutral water splitting is extensively discussed with emphases on screening methodologies, mechanisms, structure‐activity correlations, and detailed catalyst specific evolution. In addition, catalysts reported so far, are also benchmarked based on their performance separately for different electrolytes used.     

Water for small‐scale biogas digesters in sub‐Saharan Africa

Biogas could provide a more sustainable energy source than wood fuels for rural households in sub‐Saharan African. However, functioning of biogas digesters can be limited in areas of low water availability. The water required is approximately 50 dm³ day^?1 for each cow and 10 dm³ day^?1 for each pig providing manure to the digester, or 25 (±6) dm³ day^?1 for each person in the household, using a digester volume of 1.3 (±0.3) m³ capita^?1. Here, we consider the potential of domestic water recycling, rainwater harvesting, and aquaculture to supply the water needed for digestion in different countries of sub‐Saharan Africa. Domestic water recycling was found to be important in every country but was usually insufficient to meet the requirements of the digester, with households in 72% of countries need to collect additional water. Rooftop rainwater harvesting also has an important role, iron roofs being more effective than thatched roofs at collecting water. However, even with an iron roof, the size of roof commonly found in sub‐Saharan Africa (15 to 40 m²) is too small to collect sufficient water, requiring an extra area (in m²) for each person of (R/100) (where R is the rainfall in mm). If there is a local market for fish, stocking a pond with tilapia, fed on plankton growing on bioslurry from the digester, could provide an important source of additional income and hold the water required by the digester. In areas where rainfall is low and seasonal, the fishpond might be stocked only in the rainy season, allowing the pond to be covered during the dry period to reduce evaporation. If evaporative losses (E in mm) exceed rainfall, an extra catchment area is needed to maintain the water level in the pond, equivalent to approximately (1.5 × ((E?R)/R)) m² for each person in the household.     

Determination of manganese‐ and manganese‐containing fungicides with lucigenin–Tween‐20‐enhanced chemiluminescence detection

A flow‐injection (FI) method is reported for the determination of Mn(II), maneb and mancozeb fungicides based on the catalytic effect of Mn(II) on the oxidation of lucigenin and dissolved oxygen in a basic solution. The Tween‐20 surfactant has been reported for first time to enhance lucigenin chemiluminescence (CL) intensity in the presence of Mn(II) (53%) and maneb and mancozeb (89%). The calibration graphs were linear in the concentration range of 0.001–1.5 mg L^–1 (R² = 0.9982 (n = 11) with a limit of detection (S/N = 3) of 0.1 µg L^–1 for Mn(II) and 0.01–3.0 mg L^–1 [R² = 0.9989 and R² = 0.9992 (n = 6)] with a limit of detection (S/N =3) of 1.0 µg L^–1 for maneb and mancozeb respectively. Injection throughputs of 90 and 120 h^–1 for Mn(II) and maneb and mancozeb respectively, and relative standard deviations of 1.0–3.4% were obtained in the concentration range studied. The experimental variables, e.g., reagents concentrations, flow rates, sample volume, and photomultiplier tube voltage, were optimized and potential interferences were investigated. The analysis of Mn(II) in river water reference materials (SLRS‐4 and SLRS‐5) showed good agreement with the certified values incorporating an on‐line 8‐hydroxyquinoline chelating column in the manifold for removing interfering metal ions. Recoveries for maneb and mancozeb were in the range of 92 ± 5 to 104 ± 3% and 91 ± 2 to 100 ± 4% (n = 3) respectively. The effect of 30 other pesticides (fungicides, herbicides and insecticides) was also examined in the lucigenin–Tween‐20 CL system. Copyright © 2015 John Wiley & Sons, Ltd.     

Whole‐field macro‐ and micro‐deformation characteristic of unbound water‐loss in dentin hard tissue

High‐resolution deformation measurements in a functionally graded hard tissue such as human dentin are essential to understand the unbound water‐loss mediated changes and their role in its mechanical integrity. Yet a whole‐field, 3‐dimensional (3D) measurement and characterization of fully hydrated dentin in both macro‐ and micro‐scales remain to be a challenge. This study was conducted in 2 stages. In stage‐1, a stereo‐digital image correlation approach was utilized to determine the water‐loss and load‐induced 3D deformations of teeth in a sagittal section over consecutively acquired frames, from a fully hydrated state to nonhydrated conditions for a period up to 2 hours. The macroscale analysis revealed concentrated residual deformations at the dentin‐enamel‐junction and the apical regions of root in the direction perpendicular to the dentinal tubules. Significant difference in the localized deformation characteristics was observed between the inner and outer aspects of the root dentin. During quasi‐static loadings, further increase in the residual deformation was observed in the dentin. In stage‐2, dentin microstructural variations induced by dynamic water‐loss were assessed with environmental scanning electron microscopy and atomic force microscopy (AFM), showing that the dynamic water‐loss induced distention of dentinal tubules with concave tubular edges, and concurrent contraction of intertubular dentin with convex profile. The findings from the current macro‐ and micro‐scale analysis provided insight on the free‐water‐loss induced regional deformations and ultrastructural changes in human dentin.      

From water‐in‐oil to oil‐in‐water emulsions to optimize the production of fatty acids using ionic liquids in micellar systems

Biocatalysis is nowadays considered as one of the most important tools in green chemistry. The elimination of multiple steps involved in some of the most complex chemical synthesis, reducing the amounts of wastes and hazards, thus increasing the reaction yields and decreasing the intrinsic costs, are the major advantages of biocatalysis. This work aims at improving the enzymatic hydrolysis of olive oil to produce valuable fatty acids through emulsion systems formed by long alkyl chain ionic liquids (ILs). The optimization of the emulsion and the best conditions to maximize the production of fatty acids were investigated. The stability of the emulsion was characterized considering the effect of several parameters, namely, the IL and its concentration and different water/olive oil volumetric ratios. ILs from the imidazolium and phosphonium families were evaluated. The results suggest that the ILs effect on the hydrolysis performance varies with the water concentration and the emulsion system formed, that is, water‐in‐oil or oil‐in‐water emulsion. Although at low water concentrations, the presence of ILs does not present any advantages for the hydrolysis reaction, at high water contents (in oil‐in‐water emulsions), the imidazolium‐based IL acts as an enhancer of the lipase catalytic capacity, super‐activating 1.8 times the enzyme, and consequently promoting the complete hydrolysis of the olive oil for the highest water contents [85% (v/v)]. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1473–1480, 2015     

Taxonomy‐free molecular diatom index for high‐throughput eDNA biomonitoring

Current biodiversity assessment and biomonitoring are largely based on the morphological identification of selected bioindicator taxa. Recently, several attempts have been made to use eDNA metabarcoding as an alternative tool. However, until now, most applied metabarcoding studies have been based on the taxonomic assignment of sequences that provides reference to morphospecies ecology. Usually, only a small portion of metabarcoding data can be used due to a limited reference database and a lack of phylogenetic resolution. Here, we investigate the possibility to overcome these limitations using a taxonomy‐free approach that allows the computing of a molecular index directly from eDNA data without any reference to morphotaxonomy. As a case study, we use the benthic diatoms index, commonly used for monitoring the biological quality of rivers and streams. We analysed 87 epilithic samples from Swiss rivers, the ecological status of which was established based on the microscopic identification of diatom species. We compared the diatom index derived from eDNA data obtained with or without taxonomic assignment. Our taxonomy‐free approach yields promising results by providing a correct assessment for 77% of examined sites. The main advantage of this method is that almost 95% of OTUs could be used for index calculation, compared to 35% in the case of the taxonomic assignment approach. Its main limitations are under‐sampling and the need to calibrate the index based on the microscopic assessment of diatoms communities. However, once calibrated, the taxonomy‐free molecular index can be easily standardized and applied in routine biomonitoring, as a complementary tool allowing fast and cost‐effective assessment of the biological quality of watercourses.     

Trade‐offs between land and water requirements for large‐scale bioenergy production

Bioenergy is expected to play an important role in the future energy mix as it can substitute fossil fuels and contribute to climate change mitigation. However, large‐scale bioenergy cultivation may put substantial pressure on land and water resources. While irrigated bioenergy production can reduce the pressure on land due to higher yields, associated irrigation water requirements may lead to degradation of freshwater ecosystems and to conflicts with other potential users. In this article, we investigate the trade‐offs between land and water requirements of large‐scale bioenergy production. To this end, we adopt an exogenous demand trajectory for bioenergy from dedicated energy crops, targeted at limiting greenhouse gas emissions in the energy sector to 1100 Gt carbon dioxide equivalent until 2095. We then use the spatially explicit global land‐ and water‐use allocation model MAgPIE to project the implications of this bioenergy target for global land and water resources. We find that producing 300 EJ yr^?1 of bioenergy in 2095 from dedicated bioenergy crops is likely to double agricultural water withdrawals if no explicit water protection policies are implemented. Since current human water withdrawals are dominated by agriculture and already lead to ecosystem degradation and biodiversity loss, such a doubling will pose a severe threat to freshwater ecosystems. If irrigated bioenergy production is prohibited to prevent negative impacts of bioenergy cultivation on water resources, bioenergy land requirements for meeting a 300 EJ yr^?1 bioenergy target increase substantially (+ 41%) – mainly at the expense of pasture areas and tropical forests. Thus, avoiding negative environmental impacts of large‐scale bioenergy production will require policies that balance associated water and land requirements.     

Nanodiamond‐Embedded p‐Type Copper(I) Oxide Nanocrystals for Broad‐Spectrum Photocatalytic Hydrogen Evolution

Copper(I) oxide (Cu₂O) is an attractive photocatalyst because of its abundance, low toxicity, environmental compatibility, and narrow direct band gap, which allows efficient light harvesting. However, Cu₂O exhibits poor photocatalytic performance and photostability because of its short electron diffusion length and low hole mobility. Here, it is demonstrated that nanodiamond (ND) can greatly improve the photocatalytic hydrogen evolution reaction (HER) of the p‐type photocatalyst Cu₂O nanocrystals by nanocomposition. Compared with pure Cu₂O nanocrystals, this composite shows a tremendous improvement in HER performance and photostability. HER rates of 100.0 mg NDs‐Cu₂O nanocrystals are 1597 and 824 under the simulated solar light irradiation (AM 1.5, 100 mW cm^?2) and visible light irradiation (420–760 nm, 77.5 mW cm^?2), respectively. The solar‐to‐hydrogen conversion efficiency of this composite is 0.85%, which is nearly ten times higher than that of pure Cu₂O. The quantum efficiency of the composite is high, with values of 0.17% at and 0.23% at . The broad spectral response of ND provides numerous carriers for the subsequent reactions. The electron‐donating ability of ND and suitable band structures of the two components promote electron injection from ND to Cu₂O. These results suggest the broad applicability of ND to ameliorate the photoelectric properties of semiconductors.     

Climate‐related genetic variation in drought‐resistance of Douglas‐fir (Pseudotsuga menziesii)

There is a general assumption that intraspecific populations originating from relatively arid climates will be better adapted to cope with the expected increase in drought from climate change. For ecologically and economically important species, more comprehensive, genecological studies that utilize large distributions of populations and direct measures of traits associated with drought‐resistance are needed to empirically support this assumption because of the implications for the natural or assisted regeneration of species. We conducted a space‐for‐time substitution, common garden experiment with 35 populations of coast Douglas‐fir (Pseudotsuga menziesii var. menziesii) growing at three test sites with distinct summer temperature and precipitation (referred to as ‘cool/moist’, ‘moderate’, or ‘warm/dry’) to test the hypotheses that (i) there is large genetic variation among populations and regions in traits associated with drought‐resistance, (ii) the patterns of genetic variation are related to the native source‐climate of each population, in particular with summer temperature and precipitation, (iii) the differences among populations and relationships with climate are stronger at the warm/dry test site owing to greater expression of drought‐resistance traits (i.e., a genotype × environment interaction). During midsummer 2012, we measured the rate of water loss after stomatal closure (transpiration_min), water deficit (% below turgid saturation), and specific leaf area (SLA, cm² g^?1) on new growth of sapling branches. There was significant genetic variation in all plant traits, with populations originating from warmer and drier climates having greater drought‐resistance (i.e., lower transpiration_min, water deficit and SLA), but these trends were most clearly expressed only at the warm/dry test site. Contrary to expectations, populations from cooler climates also had greater drought‐resistance across all test sites. Multiple regression analysis indicated that Douglas‐fir populations from regions with relatively cool winters and arid summers may be most adapted to cope with drought conditions that are expected in the future.     

Large‐scale,long‐term trends in British river macroinvertebrates

Rivers are among the world's most modified ecosystems, with poor water quality representing a prominent problem for over 200 years, especially in urban areas. In Western Europe, however, industrial decline, tighter regulation and improved wastewater treatment have combined over recent decades to create conditions conducive to extensive restoration and positive biological change. Here, we evaluate the river macroinvertebrate fauna of England and Wales in relation to water quality, physical habitat and climate over almost two decades. We predicted that biological recovery would be characterized by: (i) greater taxon richness and prevalence of pollution‐sensitive taxa, (ii) larger changes in more heavily urbanized catchments, and (iii) temporal trends in assemblage structure that correlated with improving water quality. Family level richness increased on average by nearly 20% during 1991–2008, accompanied by a widespread shift towards taxa characteristic of well‐oxygenated and less polluted waters. Changes were largest in the most urbanized catchments. A combination of natural gradients and anthropogenic pressures explained the variation among sites, whereas temporal changes correlated with improving water quality and variations in discharge. Positive trends were not universal, however, and there was localized deterioration in some streams draining upland areas and in the lowland south east. Our results are consistent with a large‐scale ecological recovery of English and Welsh rivers since 1990, probably continuing a trend from the mid‐20th century. Based on these results, we suggest: (i) freshwater communities are resilient to long‐term anthropogenic pressures, (ii) biodiversity benefits can arise from investment and long‐term restoration intended largely to enhance ecosystem services such as drinking water and sanitary concerns, and (iii) long‐term monitoring data collected for statutory purposes–based in this case on nearly 50 000 samples–can address scientific questions at spatial and temporal extents seldom achieved in research programmes.     

TriboPump: A Low‐Cost,Hand‐Powered Water Disinfection System

Water disinfection at the point of use (POU) has enormous social and economic significance, especially for rural areas or catastrophes. To tackle the requirements of power independence and cost control in such applications, the concept of TriboPump is proposed, which is a low‐cost, hand‐powered water disinfection system. The system consists of three functional parts: a tubular coaxial‐electrode copper ionization cell (CECIC) as the disinfection device, a disk triboelectric nanogenerator (D‐TENG) as the power source, and a coaxial mechanical structure including the water pump. The adoption of D‐TENG can make the system adaptive to varying system resistances without additional power management circuits. Moreover, the integration of CECIC and TENG can successfully turn their intrinsic limitations into advantages and a synergic effect is achieved. With the integrated design, the system can effectively disinfect the water while pumping it solely by hand power. The cost estimate of the whole system can be as low as $10 for a 2‐year service. It is believed that the whole system design provides a feasible one‐stop and cost‐efficient solution for POU water pumping and disinfection, which will ideally be suitable the rural areas or sudden‐onset catastrophes.     

Methodological Challenges in Volumetric and Impact‐Oriented Water Footprints

This work identifies shortcomings in water footprinting and discusses whether the water footprint should be a volumetric or impact‐oriented index. A key challenge is the current definition of water consumption according to which evaporated water is regarded as lost for the originating watershed per se. Continental evaporation recycling rates of up to 100% within short time and length scales show that this definition is not generally valid. Also, the inclusion of land use effects on the hydrological balance is questionable, as land transformation often leads to higher water availability due to locally increased runoff. Unless potentially negative consequences, such as flooding or waterlogging, and adverse effects on the global water cycle are considered, water credits from land transformation seem unjustified. Most impact assessment methods use ratios of annual withdrawal or consumption to renewability rates to denote local water scarcity. As these ratios are influenced by two metrics—withdrawal and availability—arid regions can be regarded as uncritical if only small fractions of the limited renewable supplies are used. Besides neglecting sensitivities to additional water uses, such indicators consider neither ground nor surface water stocks, which can buffer water shortages temporally. Authors favoring volumetric indicators claim that global freshwater appropriation is more important than local impacts, easier to determine, and less error prone than putting complex ecological interaction into mathematical models. As shown in an example, volumetric water footprints can be misleading without additional interpretation because numerically smaller footprints can cause higher impacts.     

Wearable All‐Fabric‐Based Triboelectric Generator for Water Energy Harvesting

Realizing energy harvesting from water flow using triboelectric generators (TEGs) based on our daily wearable fabric or textile has practical significance. Challenges remain on methods to fabricate conformable TEGs that can be easily incorporated into waterproof textile, or directly harvest energy from water using hydrophobic textile. Herein, a wearable all‐fabric‐based TEG for water energy harvesting, with additional self‐cleaning and antifouling properties is reported for the first time. Hydrophobic cellulose oleoyl ester nanoparticles (HCOENPs) are prepared from microcrystalline cellulose, as a low‐cost and nontoxic coating material to achieve superhydrophobic coating on fabrics, including cotton, silk, flax, polyethylene terephthalate (PET), polyamide (nylon), and polyurethane. The resultant PET fabric‐based water‐TEG can generate an instantaneous output power density of 0.14 W m^?2 at a load resistance of 100 MΩ. An all‐fabric‐based dual‐mode TEG is further realized to harvest both the electrostatic energy and mechanical energy of water, achieving the maximum instantaneous output power density of 0.30 W m^?2. The HCOENPs‐coated fabric provides excellent breathability, washability, and environmentally friendly fabric‐based TEGs, making it a promising wearable self‐powered system.     

Interface Concentrated‐Confinement Suppressing Cathode Dissolution in Water‐in‐Salt Electrolyte

Mass dissolution is one main problems for cathodes in aqueous electrolytes due to the strong polarity of water molecules. In principle, mass dissolution is a thermodynamically favorable process as determined by the Gibbs free energy. However, in real situations, dissolution kinetics, which include viscosity, dissolving mass mobility, and interface properties, are also a critical factor influencing the dissolution rate. Both thermodynamic and kinetic dissolving factors can be regulated by the ratio of salt to solvent in the electrolyte. In this study, concentration‐controlled cathode dissolution is investigated in a susceptible Na₃V₂(PO₄)₃ cathode whose time‐, cycle‐, and state‐of‐charge‐dependent dissolubility are evaluated by multiple electrochemical and chemical methods. It is verified that the super‐highly concentrated water‐in‐salt electrolyte has a high viscosity, low vanadium ion diffusion, low polarity of solvated water, and scarce solute?water dissolving surfaces. These factors significantly lower the thermodynamic‐controlled solubility and the dissolving kinetics via time and physical space local mass interfacial confinement, thereby inducing a new mechanism of interface concentrated‐confinement which improves the cycling stability in real aqueous rechargeable sodium‐ion batteries.     

Enhancement of the antimicrobial properties of bacteriophage‐K via stabilization using oil‐in‐water nano‐emulsions

Bacteriophage therapy is a promising new treatment that may help overcome the threat posed by antibiotic‐resistant pathogenic bacteria, which are increasingly identified in hospitalized patients. The development of biocompatible and sustainable vehicles for incorporation of viable bacterial viruses into a wound dressing is a promising alternative. This article evaluates the antimicrobial efficacy of Bacteriophage K against Staphylococcus aureus over time, when stabilized and delivered via an oil‐in‐water nano‐emulsion. Nano‐emulsions were formulated via thermal phase inversion emulsification, and then bacterial growth was challenged with either native emulsion, or emulsion combined with Bacteriophage K. Bacteriophage infectivity, and the influence of storage time of the preparation, were assessed by turbidity measurements of bacterial samples. Newly prepared Bacteriophage K/nano‐emulsion formulations have greater antimicrobial activity than freely suspended bacteriophage. The phage‐loaded emulsions caused rapid and complete bacterial death of three different strains of S. aureus. The same effect was observed for preparations that were either stored at room temperature (18–20°C), or chilled at 4°C, for up to 10 days of storage. A response surface design of experiments was used to gain insight on the relative effects of the emulsion formulation on bacterial growth and phage lytic activity. More diluted emulsions had a less significant effect on bacterial growth, and diluted bacteriophage‐emulsion preparations yielded greater antibacterial activity. The enhancement of bacteriophage activity when delivered via nano‐emulsions is yet to be reported. This prompts further investigation into the use of these formulations for the development of novel anti‐microbial wound management strategies. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:932–944, 2014     

Solar‐to‐Hydrogen Energy Conversion Based on Water Splitting

Artificial photosynthesis provides a blueprint to harvest solar energy to sustain the future energy demands. Solar‐driven water splitting, converting solar energy into hydrogen energy, is the prototype of photosynthesis. Various systems have been designed and evaluated to understand the reaction pathways and/or to meet the requirements of potential applications. In solar‐to‐hydrogen conversion, electrocatalytic hydrogen and oxygen evolution reactions are key research areas that are meaningful both theoretically and practically. To utilize hydrogen energy, fuel cell technology has been extensively investigated because of its high efficiency in releasing chemical energy. In this review, general concepts of the photosynthesis in green plants are discussed, different strategies for the light‐driven water splitting proposed in laboratories are introduced, the progress of electrocatalytic hydrogen and oxygen evolution reactions are reviewed, and finally, the reactions in hydrogen fuel cells are briefly discussed. Overall, the mass and energy circulation in the solar‐hydrogen‐electricity circle are delineated. The authors conclude that attention from scientists and engineers of relevant research areas is still highly needed to eliminate the wide disparity between the aspirations and realities of artificial photosynthesis.