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Solid-state sensing platforms are desirable for the development of reusable sensors to promote public health measures such as testing for drinking water contamination. A bioinspired metal-organic framework (MOF)-based material has been developed by imitating metal-protein interactions in biological systems to attain high sensitivity and selectivity to Pb

The electrochemical synthesis of ammonia using nanolayered catalyst of RuO2 and CeO2 on a 3D-Graphene support at an ambient condition, demonstrates excellent NRR activity with long-term stability.

A novel material, designated Ru/ZrO2@C(MIL), was prepared by thermal transformation of metal organic framework (MOF), MIL-140C-10, in which 10 % of the conventional biphenyl-dicarboxylate linkers had been substituted with bipyridyl-dicarboxylate linkers, thereby providing sites for Ru coordination with the framework. This MOF precursor was compositionally and morphologically transformed when heated, at 500 °C, in a mixture of H2 and CO2 (3:1). The transformation afforded a high surface area product (114 m2/g) with exceptional stability and high Ru metal dispersion which was very effective as catalyst for the hydrogenation of CO2 to CH4, giving a CH4 production of 53 mol/g Ru/h (at 350 °C, 40 bar and WHSV 344 L/h/g cat.). TEM results show that the active form of the catalyst was a partially degraded (‘unzipped’) MOF structure where Ru° and ZrO2 nanoparticles (2−5 and 10−20 nm diameter, respectively) were dispersed upon carbonaceous ribbons.

The understanding of recombination of photogenerated electron/hole pairs at defect sites is a key enabler to develop bismuth vanadate (BiVO4) photoanodes at scale and low cost for photoelectrochemi...

Summary Transition metal-based nanomaterials represent an emerging class of highly active and low-cost precatalysts for the oxygen evolution reaction (OER) in alkaline electrolyzers. However, most OER precatalysts undergo slow or incomplete self-reconstructions to generate real active sites, which is a time-consuming process for achieving high OER performance. Thus, we report a new class of OER precatalysts that can achieve highly active OER species by a rapid and deep self-reconstruction (denoted by SELF-RECON). The precatalysts with a core-shell structure comprising NiMoO4 (core) and NiFe/NiFeOx nanoparticles in N-doped amorphous carbons (shell) (denoted by NiMoFeO@NC), can realize rapid MoO42− dissolution and fast formation of NiOOH with Fe incorporation simultaneously. In situ Raman spectroscopy together with electron microscopy, X-ray photoelectron spectroscopy, and electrochemical tests indicate that the obtained NiFeOOH/NiFe-LDH after SELF-RECON behave as the real active species that outperform NiMoFeO@NC, with ultralow overpotentials and extraordinary long-term stability.

The electrochemical synthesis of ammonia at ambient temperature and pressure has the potential to replace the conventional process for the production of ammonia. However, the low ammonia yield and poor long-term stability of catalysts for the synthesis of ammonia hinders the application of this technology. Herein, we endeavored to tackle this challenge by synthesizing 3-D vertical graphene (VG) on Ni foam

The synthesis of hydrogen peroxide (H2O2) from H2O and O2 by metal-free photocatalysts (e.g., graphitic carbon nitride, C3N4) is a potentially promising approach to generate H2O2. However, the phot...

Caesium silver bismuth halide double perovskites, in the first instance Cs2AgBiBr6, were recently introduced to the field of emerging photovoltaics as environmentally friendly, non-toxic and thermodynamically stable photoabsorber materials. However, the wide indirect bandgaps of these materials indicate the need for bandgap engineering and enhancing the light absorption to improve the photovoltaic performance. The present work demonstrates that this can be achieved via modification of the double perovskite with sulphide to obtain caesium silver bismuth sulphobromide materials, Cs2AgBiBr6−2xSx, which have been synthesised as pin-hole-free uniform films and systematically investigated herein. Notable enhancements in the intrinsic light absorption for 0 ≤ x ≤ 0.2 are demonstrated, as are the improvements by up to 50% in the photocurrent density of the corresponding thin-film solar cells. The devices based on the films with the nominal composition Cs2AgBiBr5.8S0.1 delivered a short-circuit current density of 3.0 ± 0.3 mA cm−2 and a power conversion efficiency of 1.9 ± 0.1% (cf. 2.1 ± 0.2 mA cm−2 and 1.3 ± 0.1%, respectively, for the control cells based on the sulphide-free Cs2AgBiBr6). Equally important, caesium silver bismuth sulphobromides demonstrate excellent stability against all common environmental stimuli, viz. heat, light, and humidity.

Cu is a catalyst that can electrochemically reduce CO2 to a variety of industrially important carbon products, but often with poor selectivity and low current density. Alloying Cu with other metals...

Electrochemical water splitting in acidic conditions offers important advantages over that in alkaline systems, but the technological progress is limited by the lack of inexpensive and efficient anode catalysts that can stably operate at a low pH and elevated temperature. Here we demonstrate oxygen evolution catalysts that are based on non-noble metals, are formed in situ during electrooxidation of acidic water and exhibit a high stability in operation due to a self-healing mechanism. The highly disordered mixed metal oxides generated from dissolved cobalt, lead and iron precursors sustain high water oxidation rates at reasonable overpotentials. Moreover, utilizing a sufficiently robust electrode substrate allows for a continuous water oxidation at temperatures up to 80 °C and rates up to 500 mA cm−2 at overpotentials below 0.7 V with an essentially flat support and with no loss in activity. This robust operation of the catalysts is provided by the thermodynamically stable lead oxide matrix that accommodates homogeneously distributed catalytic dopants. Electrochemical water splitting in acidic conditions is limited by the lack of inexpensive and stable anode catalysts. Now, Simonov and colleagues report a non-noble metal-based oxygen evolution catalyst formed in situ that exhibits high stability for acidic water oxidation due to a self-healing mechanism.

This paper examines the effect on interfacial shear strength (IFSS) when grafting polyethyleneoxide (PEO) polymers of various molecular weights to a carbon fiber surface. Using copper-azide-alkyne cycloaddition click chemistry, PEO polymers of 1 kDa, 2 kDa, 5 kDa, and 10 kDa were tethered to the fiber surface without causing degradation of the fiber surface. The resulting IFSS increases were maximised (130% and 160%) for the 1 kDa and 10 kDa surface modified fibers, respectively. These data suggest that increases in IFSS are the result of an interplay between the density of surface modification versus the penetration of the grafted polymer into the matrix interphase. The trade-off between interphase penetration and surface grafting density is highlighted for the 2 and 5 kDa PEO chains on the fiber surface which display smaller IFSS increases (85% and 117%, respectively). Measuring the mobility of the PEO polymers by 1H NMR found an order of magnitude decrease in diffusion coefficient for each successive increase in molecular weight, supporting the hypothesis that grafting density decreases with molecular weight. Molecular dynamics simulations of the carbon fiber-matrix interface further supports these observations. These results will inform the design of complementary interfaces for various materials in a range of supporting media.

Previous theoretical work has predicted vanadium and niobium nitrides to be catalytically active toward the electrochemical reduction of dinitrogen to ammonia and inactive for the hydrogen evolutio...

Nanogels were prepared by ionotropic gelation of chitosan (CS) with tripolyphosphate (TPP). The use of such nanogels to prepare coatings by layer-by-layer deposition (LbL) was studied. The nanogels were characterized in terms of particle size, zeta-potential and stability. Nanogel suspensions were used to build polyelectrolyte multilayers on silicon wafers and on PCL fiber mats by LbL-deposition. Three different polysaccharides were used as polyanions, namely chondroitin sulfate, alginate and hyaluronic acid. The ellipsometric thickness was demonstrated to depend significantly on the type of polyanion. XPS analysis with depth profiling further substantiated the differences in the chemical composition of the films with the different polyanions. Furthermore, XPS data clearly indicated a strong penetration of the polyanions into the CS-TPP layer, resulting in a complete exchange and release of the TPP ions. The LbL-deposition also was studied with PCL fiber mats, which were modified with a chitosan-PCL-graft polymer and alginate. The possibility to create graded coatings on the fiber mats was shown employing fluorescently labelled CS-TPP nanoparticles. The potential of the coatings as drug delivery system for therapeutic proteins was exemplified with the release of Transforming Growth Factor β3 (TGF-β3). The CS-TPP nanogels were shown to encapsulate and release therapeutic proteins. In combination with the layer-by-layer deposition they will allow the creation of PCL fiber mat implants having with drug gradients for applications at tissue transitions.

Although electrochemical oxidation (ECO) has shown excellent potential for disinfecting wastewater and surface waters, its application on urban stormwater has been rarely tested. In order to improve stormwater ECO design, this paper explores the major inactivation processes using Boron Doped Diamond (BDD) and titanium Dimensional Stable Anodes (DSA). Both BDD and DSA showed comparable disinfection rates. The mechanism study suggested that BDD relied on hydroxyl radical and the presence of chloride ions, while DSA disinfected stormwater mainly via the production of free‑chlorine. A deterioration study carried out at a catchment in Melbourne, showed a steady performance for BDD and revealed that DSA's performance degraded with time, likely linked to the high operational voltage required for specific chemistry of stormwater. Scanning Electron Microscopes and an Energy Dispersive X-ray Detector tests confirmed elemental losses occurred on the DSA surface, together with an aluminium/silicon coating layer potentially sourced from the stormwater clayish sediments. Furthermore, disinfection by-products in electrochemical disinfected stormwater using either BDD or DSA were at least one order of magnitude lower than the Australia Drinking Water Guidelines limits. The mechanism and long-term study demonstrated that careful anode selection is required as some anodes will deteriorate in stormwater matrices faster than others.

The organic matter (kerogen, defined as including the organic material soluble and insoluble in organic solvents at room temperature) from two marine oil shales, El-Lajjun (Jordan) and Julia Creek (Queensland, Australia), has been extracted by the commonly used HCl-HF method and the resulting products compared with those obtained using the NaOH-HCl method, i.e. with initial strong alkali extraction. The elemental analyses on a dry ash-free basis of the solids obtained by the two methods were similar to each other and to that of the original oil shale. The pyrolysis-gas chromatography–total ion chromatograms were also similar for the kerogens obtained by the two methods and for the original oil shale, showing regular n-alkene/alkane series, as would be expected from the high atomic H/C ratio, and series of alkyl substituted thiophenes and benzothiophenes. The solid state 13C NMR spectra showed similar trends. The Fe contents of the solids obtained by the HCl-HF treatment were much higher than for the solids from NaOH-HCl treatment, which could have implications for reactivity studies. XPS showed depletion of the sulfur and oxidation near the surface and confirmed that some aliphatic sulfur was present. However, in general, both methods gave organic products with similar characteristics, allowing isolation of organic matter by a method not involving HF, whose use is restricted in many countries.

It is widely acknowledged that the integrity of the fiber-to-matrix interface inherent to carbon fiber reinforced composites has scope for improvement. One promising and highly-researched strategy is the use of surface manipulation of carbon fibers to enhance their mechanical performance under shear. The complexity of commonly used surface treatments, such as plasma and oxidative etching, Requires modification of existing manufacturing infrastructure and thus their broad adoption in a manufacturing context has been limited. Herein we show that simply impregnating the carbon fibers with aryl diazonium salts and subjecting them to external stimuli, such as mild heating (100 °C), can induce surface modification which can deliver improvements of up to 150% in interfacial shear strength (IFSS) in epoxy resins. Interrogation of the fiber-to-matrix interface using molecular dynamics simulations suggests that the surface grafted molecules imparts a ‘dragging effect’ though the polymer phase and that the surface concentration of these compounds is critical to enhancing IFSS. This process obviates the practical limitations of current functionalization procedures for carbon fibers and requires infrastructure that is already routinely available on fiber manufacturing lines.

This paper investigates fifteen fiber types against two epoxy resin systems and the effects of altering electrochemical oxidization conditions and sizing deposition ratio on interfacial shear strength (IFSS). Oxidization current was altered between 0, 2, and 3.4 A while sizing deposition ratio was altered between unsized, 1:10, 1:15 and 1:20 parts sizing to water. Desized fibers were also compared against pristine unsized fibers. Results show, a correlation between increasing current and IFSS, however sizing has an optimal ratio for best performance. Improvements through oxidization are attributed to the introduction of oxygenated functional groups on the fiber surface while improvements due to sizing are attributed to the promotion of a chemically active intermediate layer between the fiber and resin. Fiber roughness was seen to play no effect on IFSS. Desized fibers and unsized fibers had similar IFSS results however characterisation shows chemical composition of the fiber surfaces to be very different.

Silicon-based impurities are ubiquitous in natural graphite. However, their role as a contaminant in exfoliated graphene and their influence on devices have been overlooked. Herein atomic resolution microscopy is used to highlight the existence of silicon-based contamination on various solution-processed graphene. We found these impurities are extremely persistent and thus utilising high purity graphite as a precursor is the only route to produce silicon-free graphene. These impurities are found to hamper the effective utilisation of graphene in whereby surface area is of paramount importance. When non-contaminated graphene is used to fabricate supercapacitor microelectrodes, a capacitance value closest to the predicted theoretical capacitance for graphene is obtained. We also demonstrate a versatile humidity sensor made from pure graphene oxide which achieves the highest sensitivity and the lowest limit of detection ever reported. Our findings constitute a vital milestone to achieve commercially viable and high performance graphene-based devices., Silicon-based contaminants are ubiquitous in natural graphite, and they are thus expected to be present in exfoliated graphene. Here, the authors show that such impurities play a non-negligible role in graphene-based devices, and use high-purity parent graphite to boost the performance of graphene sensors and supercapacitor microelectrodes.

The native surface oxide upon a single phase low-density compositionally complex alloy (CCA), AlTiVCr, was studied herein—owing to its exceptionally high aqueous corrosion resistance. The nature of the native surface oxide/surface film was elaborated in the context of corrosion resistance, based on results from electrochemical testing, secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy. Selective oxidation and unoxidized metal in the surface film were observed. Such features are comparatively unique and posited to be relevant to CCAs and high entropy alloys more generally.

International audience; While peak fitting of spectra/data is frequently performed in science, recent reports suggest that the quality of peak fitting in the scientific literature is often inadequate. Here, we describe a new statistical tool for determining the quality of fitting protocols, illustrating this capability with X-ray photoelectron spectroscopy (XPS) data. This tool, box plots of random starting conditions and their results, helps identify local minima in the multidimensional fit space of the fit parameters. Ideally, there should be a single global minimum for a fitting protocol such that different, reasonable starting conditions lead to the same result. To determine whether a fit space contains multiple local minima, a series of reasonable starting conditions is randomly chosen for the fit. If the boxes in the box plot of the peak areas of these multiple fits are narrow, the different possibilities converge to a single global minimum. Conversely, if the boxes are wide, multiple local minima are present. This method is related to the mathematical concept of ‘disproof by contradiction’. Our approach is demonstrated with four- and ten-component fits to a moderately complex C 1s XPS narrow scan. The results from our analysis compare favorably to those of traditional Monte Carlo analyses and uniqueness plots, where box plots are also applied to the Monte Carlo results, and each of these statistical tools performs a different function/probes a fit space/protocol differently.

Desorption/ionization on porous silicon mass spectrometry (DIOS-MS) is shown to be a powerful technique for the sensing of low-molecular-weight compounds, including drugs and their metabolites. Surface modification of DIOS surfaces is required to increase analytical performance and ensure stability. However, common wet chemical modification techniques use fluorosilanes, which are less suitable for high-throughput manufacturing and analytical repeatability. Here, we report an alternative, rapid functionalization technique for DIOS surfaces using plasma polymerization (ppDIOS). We demonstrate the detection of drugs, metabolites, pesticides, and doping agents, directly from biological matrices, with molecular confirmation performed using the fragmentation capabilities of a tandem MS instrument. Furthermore, the ppDIOS surfaces were found to be stable over a 162 day period with no loss of reproducibility and sensitivity. This alternative functionalization technique is cost-effective and amenable to upscaling, ensuring avenues for the high-throughput manufacture and detection of hundreds of analytes across various applications while still maintaining the gold-standard clinical technique using mass spectrometry.

The real-time dissolution of the single-phase compositionally complex alloy (CCA), Al1.5TiVCr, was studied using an inline inductively coupled plasma method. Compositionally complex alloys (CCAs), a term encompassing high entropy alloys (HEAs) or multi-principal element alloys (MPEAs), are—in general—noted for their inherently high corrosion resistance. In order to gain an insight into the dissolution of Al1.5TiVCr alloy, atomic emission spectroelectrochemistry was utilised in order to measure the ion dissolution of the alloy during anodic polarisation. It was revealed that incongruent dissolution occurred, with preferential dissolution of Al, and essentially no dissolution of Ti, until the point of alloy breakdown. Results were correlated with X-ray photoelectron spectroscopy, which revealed a complex surface oxide inclusive of unoxidised metal, and metal oxides in disproportion to the bulk alloying element ratio.

3D/2D hybrid perovskite systems have been intensively investigated to improve the stability of perovskite solar cells (PSCs), whereas undesired crystallization of 2D perovskite during the film formation process could undermine the structural stability of 2D perovskite materials, which causes serious hysteresis of PSCs after aging. This issue is, however, rarely studied. The stability study for 3D/2D hybrid systems to date is all under the one-direction scan, and the lack of detailed information on the hysteresis after aging compromises the credibility of the stability results. In this work, by correlating the hysteresis of the hybrid PSCs with the 2D crystal structure, we find that the prompt 2D perovskite formation process easily induces numerous crystal imperfections and structural defects. These defects are susceptible to humidity attack and decompose the 2D perovskite to insulating long-chain cations and 3D perovskite, which hinder charge transfer or generate charge accumulation. Therefore, a large hysteresis is exhibited after aging the 3D/2D hybrid PSCs in an ambient environment, even though the reverse-scan power conversion efficiency (PCE) is found to be well-preserved. To address this issue, alkali cations, K

As a group of subject-matter experts in X-ray photoelectron spectroscopy (XPS) and other material characterization techniques from different countries and institutions, we write this document to raise awareness of an epidemic of poor and incorrect materials data analysis in the literature. This issue is a growing problem with many causes and very undesirable consequences. It contributes to what has been called a "reproducibility crisis", which is a recent concern of the U.S. National Academies of Science (Baker,2016; Harris, 2017; NASE&M, 2019).

Summary Effective design of bifunctional catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is important but remains challenging. Herein, we report a three-dimensional (3D) hierarchical structure composed of homogeneously distributed Ni-Fe-P nanoparticles embedded in N-doped carbons on nickel foams (denoted as Ni-Fe-P@NC/NF) as an excellent bifunctional catalyst. This catalyst was fabricated by an anion exchange method and a low-temperature phosphidation of nanotubular Prussian blue analogue (PBA). The Ni-Fe-P@NC/NF displayed exceptional catalytic activity toward both HER and OER and delivered an ultralow cell voltage of 1.47 V to obtain 10 mA cm−2 with extremely excellent durability for 100 h when assembled as a practical electrolyser. The extraordinary performance of Ni-Fe-P@NC/NF is attributed to the abundance of unsaturated active sites, the well-defined hierarchical porous structure, and the synergistic effect between multiple components. Our work will inspire more rational designs of highly active non-noble electrocatalysts for industrial energy applications., Graphical Abstract, Highlights • Nanotubular Prussian blue analogue as a precursor is synthesized by anion exchange • The catalyst exhibits excellent catalytic activity for hydrogen and oxygen production • The catalyst-based electrolyser has a low cell voltage of 1.47 V to obtain 10 mA cm−2 • The electrolyser shows an extremely excellent durability for 100 h at 50 mA cm−2, Catalysis; Materials Chemistry; Nanomaterials; Energy Materials

Efficient storage of solar and wind power is one of the most challenging tasks still limiting the utilization of the prime but intermittent renewable energy sources. The direct storage of concentrated solar power in renewable fuels via thermochemical splitting of water and carbon dioxide on a redox material is a scalable approach with up to 54% solar-to-fuel conversion efficiency. Despite progress, the search for earth-abundant materials that can provide and maintain high H2 and CO production rates over long period of high-temperature cycles continues. Here, we report a strategy to unlock the use of manganese, the 12th most abundant element in the Earth's crust, for thermochemical synthesis of solar fuels, achieving superior thermochemical stability, oxygen exchange capacity, and up to seven times higher mass-specific H2 and CO yield than cerium dioxide. We observe that incorporation of a small fraction of cerium ions in the manganese (II,III) oxide crystal lattice drastically increases its oxygen ion mobility, allowing its reduction from oxide to carbide during methane partial oxidation with simultaneous Ce exsolution. High CO2 and H2O splitting rates are achieved by re-oxidation of the carbide to manganese (II) oxide with simultaneous reincorporation of the cerium ions. We demonstrate that the oxide to carbide reaction is highly reversible achieving remarkable CO2 splitting rates over 100 thermochemical cycles of methane partial oxidation and CO2 splitting, and preserving the initial oxygen exchange capacity of 0.65 molO m o l M n − 1 and 89% of the fuel production rates. Due to this extraordinarily high reversible oxygen exchange capacity, the 3% Ce-doped manganese oxide achieves an average mass-specific CO yield for CO2 splitting of 17.72 mmolCO g−1, which is significantly higher than that previously achieved in thermochemical redox cycles. More generally, these findings suggest that incorporation of small soluble amounts of cerium in earth-abundant transition metal oxides like manganese oxide is a powerful approach to enable solar thermochemical fuel synthesis.

The development of hole transporting layers that optimize charge extraction and minimize interfacial recombination losses offer an important route for further enhancement in the performance of inverted perovskite solar cells (PSCs). NiO is a widely adopted hole transporting material in such devices, possessing a reasonably high hole mobility and suitable energy level positions to provide high efficiency solar cells. However, its use in inverted PSCs has typically resulted in relatively low fill factors, which arises from underlying contact issues between the perovskite and NiO layers. In this work, we address this issue by employing a thin mesoporous NiO scaffold formed via chemical bath deposition as the hole transporting layer. This hole transporting material is found to dramatically improve the performance of inverted mixed cation and anion PSCs by enhancing their light harvesting and charge transporting efficiencies. Optimized devices achieve efficiencies of up to 16.7% and fill factors as high as 85%. These values are significantly higher than PSCs using conventionally spray-deposited planar NiO hole transport layers, which exhibit efficiencies of up to 14.5% and fill factors of only 73%.

International audience; Colored and color-changing materials are central to perception and interaction in nature and have been exploited in an array of modern technologies such as sensors, visual displays and smart materials. Attempts to introduce color into carbon fiber materials have been limited by deleterious impacts on fiber properties, and the extension of colored fibers towards 'smart composites' remains in its infancy. We present carbon fibers incorporating structural color, similar to that observed on the surface of soap bubbles and various insects and birds, by modifying the fiber surface through in situ polymerization grafting. When dry, the treated fibers exhibit a striking blue color, but when exposed to a volatile solvent, a cascade of colors across the visible region is observed as the film first swells and then shrinks as the solvent evaporates. The treated fibers not only possess a unique color and color-changing ability, but can also be reversibly formed into complex shapes and bear significant loads even without being encased in a supporting polymer. The tensile strength of treated fibers shows a statistically significant increase (+12%) and evaluation of the fiber-to-matrix adhesion of these polymers to an epoxy resin shows more than 300% improvement over control fibers. This approach creates a new platform for the multifaceted advance of smart composites.

This study reports for the first time the use of water soluble sulfonated octa-phenyl POSS nanowhiskers for the surface treatment for carbon fibres using simple dip-coating method. The water soluble nature of the functionalized POSS makes it appealing from a formulation perspective as it can be applied simply using an aqueous media. The synthesis of the water soluble SOP-POSS was achieved via one-step aromatic electrophilic sulfonation of octaphenyl POSS. Collective results from NMR, XPS and FTIR analysis confirmed the meta mono-substitution of all phenyl rings in the starting material with a sulfonic group, leading to its water solubility. Surface treatment of commercially oxidized and unsized carbon fibres was achieved via simple dip-coating of the fibres in an aqueous media solution containing the synthesized SOP-POSS product. After the dip-coating process, the carbon fibres are homogeneously covered with surface adsorbed SOP-POSS nanowhiskers. Physico-chemical characterization of the fibres investigated by Inverse Gas Chromatography (IGC) revealed an improvement in surface chemical homogeneity associated with a significant increase in surface oxygen contents and an overall level of surface polarity comparable to commercially sized fibres. The interfacial adhesion properties between the treated carbon fibres and an epoxy matrix were investigated by single fibre fragmentation technique. The results of the tests revealed that significant enhancement of interfacial properties was achieved as a result of a combination of physical inter-molecular interactions at the fibre-matrix interface and localized nano-mechanical strengthening of the epoxy. The outcomes of this research lay the path forward for a potential simple surface treatment of commercial carbon fibres for Interfacial property improvement in composites.

Metal halide perovskite solar cells (PSC) exhibit outstanding power conversion efficiencies when fabricated as mm-sized devices, but creation of high-performing large-area PSCs that are stable under operating conditions on a sufficiently long timescale still presents a significant challenge. We demonstrate herein that modification of the interface between the perovskite and a spiro-OMeTAD hole-transporting material with commercially available para-substituted benzenethiol molecules facilitates fabrication of cm-sized PSCs with both improved efficiency and stability. Comprehensive analysis using specialised and conventional physical characterisation techniques has been undertaken to demonstrate that band alignment at the perovskite surface can be tuned to improve the solar cell efficiency via adsorption of benzenethiols with a significant dipole moment. Moreover, modification of the perovskite with cyano-substituted benzenethiol enhances charge extraction and reduces charge recombination in the devices. These effects enable improvements in the power conversion efficiency of PSCs from 19.0 to 20.2% and from 18.5 to 19.6% under 1 sun AM 1.5G irradiation with 0.16 and 1.00 cm2 apertures, respectively. Most importantly, benzenethiol-modified perovskite solar cells retain more than 80% of the initial performance after 185 h of continuous operation at 50% relative humidity and 50 °C device temperature under 1 sun irradiation, while devices with no interfacial modification undergo continuous deterioration down to 35% of the initial efficiency. These significant improvements are provided by a very simple and highly reproducibile modification procedure that can be readily adopted in other types of PSCs.

Spray pyrolysis of bismuth(III) tris(4-methylbenzodithioate) toluene solutions containing either silver(I) acetate and 1-octanethiol, or copper(I) acetate and 1,2-ethanedithiol is introduced as a low-temperature solution-based method to produce sub-100 nm thick coatings of α cubic rock salt AgBiS2 or orthorhombic Cu3BiS3, respectively. The structure, morphology and optoelectronic properties of the materials thus obtained have been comprehensively characterised using conventional techniques. Extensive optimisation of the deposition conditions has been undertaken to achieve the formation of uniform, 60–70 nm thick films of densely packed AgBiS2 and Cu3BiS3 crystallites with a typical size of 10–20 nm. Planar photovoltaic devices based on spray-deposited AgBiS2 as a light harvester, ZnO as an electron transporting layer, and spiro-OMeTAD as a hole transporting material produce short-circuit current densities as high as 18.1 ± 0.6 mA cm−2 under 1 sun AM 1.5 G irradiation. The devices are stable without encapsulation under ambient conditions for at least 1 month.

The present work introduces a rapid low-temperature microwave-assisted synthesis of nickel(iron) layered hydroxides and sulphides that exhibit robust catalytic activity for electrooxidation of alkaline water – the most feasible source of electrons for any renewable fuel synthesis. The procedures require not more than an hour to complete at 120–150 °C with quantitative yields of: (i) few-atomic-layers thick porous sheets of Ni0.75Fe0.25(OH)2+x with surface area ABET = 149 m2 g−1, and (ii) interconnected Ni0.75Fe0.25S2+y particles of few nanometers in size covered with a thin oxide/hydroxide layer having ABET = 87 m2 g−1. These and other morphological and structural features of the materials were inferred from XRD, XPS, Ni- and Fe-edge EXAFS/XANES, TEM/SAED, EDX mapping, SEM, N2 adsorption–desorption, and electrochemical techniques. At lower loadings on the electrode surface (≤0.01 mg cm−2), the specific activity for water (1 M KOH) electrooxidation at 0.3 V overpotential is 210 A g−1 for Ni0.75Fe0.25(OH)2+x, and 384 A g−1 for Ni0.75Fe0.25S2+y, which excels the performance of the best-performing analogues. The enhanced electrocatalytic activity of sulphides over hydroxides is defined by the better electrical conductivity and different nature of the electrochemically active surface species. At higher loadings, the activity of the microwave-synthesised NiFe catalysts is found to be partially limited by agglomeration, though still high enough to enable the water oxidation rate of 10 mA cmgeom−2 at overpotentials of only 0.270 ± 0.005 (flat support) and 0.21 V (foam support) with Ni0.75Fe0.25S2+y. The developed methods offer a new facile strategy for the creation of high-performing multicomponent catalysts.

Hydrogen at present is mainly produced from fossil fuels for use in ammonia synthesis, the petrochemical industry, and chemical production. In the future, hydrogen will be increasingly used as an energy vector. Although water electrolysis to produce hydrogen with renewable electricity offers a clean process, the approach is energy intensive, requiring a large renewable resource footprint. Methanol-water co-electrolysis can reduce the energy input by > 50%; its electrochemical oxidation poses complex issues such as poisoning of the catalyst, sluggish oxidation kinetics, and degradation over time. The addition of nano-sized SnO2 to PtRu/C catalyst, to reduce noble metal loading, has been shown here to reduce catalyst leaching and increase the chemical, micro-structural, and performance stability of the methanol-water co-electrolysis process during extended periods of testing. The electrochemical characterization, analysis of the methanol solution, and exit gases, post-cell testing, revealed complete oxidation of methanol with little performance degradation. This is further supported by the stability of the catalyst composition and structure as revealed by the post-mortem XRD and XPS analysis of the cell. The energy balance calculations show that methanol-water co-electrolysis can significantly reduce the renewable energy footprint, and the process can become carbon neutral if bio-methanol is used with renewable electricity.

Coupling TiO2 with WO3 to develop photocatalytic heterojunctions is one of the most widely used strategies to realize their superior photoactivity. However, the interfacial charge transfer in these heterojunctions is not efficient to achieve an optimized activity. For the first time, the present study reports a facile hydrolysis-hydrothermal approach, whereby ultradispersed TiO2 nanocrystals and WO3 nanorods are concurrently anchored onto reduced graphene oxide (rGO) and formed a novel Z-scheme heterojunction photocatalyst TiO2/rGO/WO3 (TRW). Transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence spectra (PL) are employed to characterize TRW. Control experiments indicate that, in the synthesis process, glucose and the by-product sodium chloride from the hydrolysis reactions are critical for forming highly dispersed and uniform-sized TiO2 nanocrystals and WO3 nanorods. Compared with TiO2/WO3 nanocomposites, TRW shows enhanced activity for bacterial inactivation under simulated solar light. As confirmed by electrochemical characterizations and the reactive oxygen species, rGO in TRW suppresses the recombination of electron-hole pairs and boosts the O2 reduction reactions during photocatalytic process. Z-scheme electron transfer in TRW is proposed based on surface redox reactions and XPS analysis after light irradiation. This study could provide a new clue for designing graphene-based heterojunction photocatalysts for environmental applications.

The appearance of surface fat during the atomization process in spray drying of milk particles often impairs the functional powder properties. To investigate a possible approach that could minimise the surface fat formation, the interaction between a whole milk model emulsion and λ-carrageenan at various concentrations was studied, as well as how it influences the atomization behaviour and the resulting particle characteristics. Carrageenan can stabilize emulsions in the presence of milk protein by adsorption on the milk fat globule membranes. If too little or too much of the polysaccharide was added, bridging flocculation or depletion flocculation, respectively, occurred inside the emulsions. The best stability and minimal fat globule size were obtained for a carrageenan content of 0.3% w/w. Rheological investigation indicated that the extensional viscosity can be an important factor influencing the emulsion disintegration behaviour during atomization. The λ-carrageenan stabilized emulsions featured a significantly increased extensional viscosity and a better fat encapsulation in the corresponding spray-dried particles, promoting solubility and oxidative stability. Surface fat extraction showed that the most stable emulsion lead to particles with the least amount of surface fat. Though the surface of these particles was still covered by fat according to spectroscopic analysis, this surface fat layer was very thin in comparison to carrageenan-free powder as observed by confocal microscopy. Yet, the addition of carrageenan was also found to have one adverse effect on the intended powder properties, as the strengthened emulsion network translated into denser particles and thus a deterioration of the powder's reconstitution behaviour.

The aim of this study was to investigate the ability of L-leucine (LL) in preventing moisture-induced deterioration in the in vitro aerosolization performance of spray-dried (SD) salbutamol sulfate (SS). Increasing mass fraction of LL (5-80%) were co-spray dried with SS, and the physicochemical properties of the powders were characterized by laser diffraction, X-ray powder diffraction (XRD) and dynamic vapour sorption (DVS). Furthermore, the surface morphology and chemistry of fine particles was analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The in vitro aerosolization performance of powders stored at different relative humidity (RH) was evaluated by a next generation impactor (NGI). The SD SS powders were moderately hygroscopic and amorphous, of which the uptake of moisture upon storage caused a drop in the aerosolization performance. The results showed that 40% (w/w) LL was sufficient to eliminate the effect of moisture on the aerosolization performance at 60% RH. The formulation containing 40% (w/w) LL also maximized the aerosolization performance of SD SS powders (stored in desiccator) with the emitted fraction being 90.0±1.8%, and the fine particle fraction based on the recovered dose (FPFrecovered) and emitted dose (FPFemitted) being 78.0±3.7% and 86.6±2.9%, respectively. The underlying mechanisms were that the crystalline LL increased the degree of particle surface corrugation, and reduced particle fusion and cohesiveness to facilitate dispersion. However, there is still a great challenge to prevent the moisture-induced deterioration in the aerosolization performance at 75% RH due to the recrystallization of SD SS. In conclusion, LL is a potential excipient for reducing moisture-induced deterioration in the aerosolization performance of SD amorphous powders, but still has drawbacks in preventing the recrystallization-induced deterioration.

Influence of the conditions for aerobic oxidation of Mn2+(aq) catalysed by the MnxEFG protein complex on the morphology, structure and reactivity of the resulting biogenic manganese oxides (MnOx ) is explored. Physical characterisation of MnOx includes scanning and transmission electron microscopy, and X-ray photoelectron and K-edge Mn, Fe X-ray absorption spectroscopy. This characterisation reveals that the MnOx materials share the structural features of birnessite, yet differ in the degree of structural disorder. Importantly, these biogenic products exhibit strikingly different morphologies that can be easily controlled. Changing the substrate-to-protein ratio produces MnOx either as nm-thin sheets, or rods with diameters below 20 nm, or a combination of the two. Mineralisation in solutions that contain Fe2+(aq) makes solids with significant disorder in the structure, while the presence of Ca2+(aq) facilitates formation of more ordered materials. The (photo)oxidation and (photo)electrocatalytic capacity of the MnOx minerals is examined and correlated with their structural properties.

The surface of carbon fibre was rapidly modified by reductive electrochemical deposition employing a range of diazonium salts. Three sets of fibre were generated possessing pendant amine, carboxylic acid, and lipophilic amide (N-hexyl amide) groups and the effect of these surface chemistries on interfacial shear strength (IFSS) was examined in epoxy resins. Surface grafting of the fibres was studied by X-ray photoelectron spectroscopy, and physical characterisation of the modified fibres showed that our treatments had no detrimental effects on Young's modulus and tensile strength. IFSS increases of 172% and 30% (relative to control fibres) were observed for the amine and lipophilic amide functionalised, respectively. Molecular dynamics simulations of the lipophilic amide suggests IFSS enhancement via soft-soft interactions. Surprisingly, the IFSS of fibres that exhibited carboxylic acid groups at the surface were indistinguishable from that of the untreated control fibres. When applied to polypropylene grafted with maleic anhydride, the amine grafted fibres showed a 67% increase relative to control fibres, attributed to covalent cross-linking between the fibre and maleic anhydride co-monomer.

Thiol groups can undergo a large variety of chemical reactions and are used in solution phase to conjugate many bioactive molecules. Previous research on solid substrates with continuous phase glow discharge polymerization of thiol-containing monomers may have been compromised by oxidation. Thiol surface functionalization via glow discharge polymerization has been reported as requiring pulsing. Herein, continuous phase glow discharge polymerization of allyl mercaptan (2-propene-1-thiol) was used to generate significant densities of thiol groups on a mixed macrodiol polyurethane and tantalum. Three general classes of chemistry are used to conjugate proteins to thiol groups, with maleimide linkers being used most commonly. Here the pH specificity of maleimide reactions was used effectively to conjugate surface-bound thiol groups to amine groups in collagen. XPS demonstrated surface-bound thiol groups without evidence of oxidation, along with the subsequent presence of maleimide and collagen. Glow discharge reactor parameters were optimized by testing the resistance of bound collagen to degradation by 8 M urea. The nature of the chemical bonding of collagen to surface thiol groups was effectively assessed by colorimetric assay (ELISA) of residual collagen after incubation in 8 M urea over 8 days and after incubation with keratinocytes over 15 days. The facile creation of useable solid-supported thiol groups via continuous phase glow discharge polymerization of allyl mercaptan opens a route for attaching a vast array of bioactive molecules. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1940-1948, 2017.

This work describes the facile microwave synthesis of interlayer expanded, nanosized MoS2 sheets that are vertically aligned on a well-conducting reduced graphene (rGO) support, as confirmed by X-ray diffraction, Raman and X-ray photoelectron spectroscopy, scanning electron microscopy with energy dispersive X-ray analysis, and high-resolution transmission electron microscopy. Such structure has been predicted to be highly favorable for efficient electrocatalysis of hydrogen evolution by MoS2 but could not be achieved until now. Films deposited from the microwave-synthesized MoS2-rGO composites demonstrate outstanding and stable hydrogen evolution performance in acidic solution. These catalysts exhibit an exchange current density as high as 1.0 ± 0.2 A g–1MoS2-rGO, sustain a current density of 10 mA cm–2 (36 A g–1MoS2-rGO) at an overvoltage of 0.104 ± 0.002 V, and maintain steady performance for many hours. Importantly, our simple synthesis affords several advantages over more sophisticated methods used pr...

We have found demonstrated that the use of tetrahydrofuran (THF) as a solvent to produce dispersed, water soluble fullerenes results in significant oxidation and degradation of the fullerene cage, which has not been reported previously. We also report a new finding that the use of N, N-dimethylformamide (DMF) can also generate stabilised fullerene (C60) nanoparticle dispersions in aqueous solutions including water and phosphate buffered saline (PBS) buffer. We compare this new DMF method with the well-known THF method following an extensive chemical and physical analysis of the resulting nanoparticles. The exact mechanism of action behind this oxidation and degradation is unknown, however, the role of peroxides is likely. The method of solvent exchange based on the use of DMF results in the formation of fullerene nanoparticle agglomerates that are highly stable in PBS and water, while the THF agglomerates are only stable in water. However, caution should be applied when using these approaches due to the significant degradation of the fullerene cage observed when using various techniques such as dynamic light scattering (DLS), matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR) and cryo transmission electron microscopy (cryo-TEM). Our results show that the solvent exchange technique using THF results in partial oxidation and degradation of C60, interestingly, the DMF evaporative method results in greater oxidation and degradation of C60 but significantly enhanced colloidal stability in buffer.

Reproducible and in-depth studies of the electrochemical graphite intercalation and oxidation processes were carried out with the use of an electrochemical Tee-cell setup. The electrochemical method allowed simpler and greater controllability over the level of oxidation/functionalization, relative to the commonly employed chemical oxidation approach (e.g. the modified Hummers method). Extensive characterization was carried out to understand the properties of the electrochemically-derived graphite oxide (EGrO), and it was found that the abundance of each functionality was highly dependent on the electrochemical reaction time or the concentration of the electrolyte (perchloric acid) employed. Notably, the amount of oxygen functional groups on EGrO could be as high as 30 wt%, but the degree of oxidation did not proceed beyond the generation of carbonyl species. The controllable oxidation level of the EGrO makes it an attractive precursor for many applications, such as electronics and nanocomposites.

We successfully synthesized a novel electro-catalyst with a unique structure of Ni2P nanoparticles decorating the surface of MoO2@MoS2 sub-microwires on titanium foil (denote as NiMoO-SP/Ti) via a facile temperature-programmed sulfuration-phosphorization from its nickel molybdate precursor. The metallic MoO2 core facilitates electron transfer, and the interfaces between MoS2 nanosheets and Ni2P nanoparticles enhance catalytic activity both for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Due to this unique structure, the obtained NiMoO-SP/Ti showed an enhanced OER performance in alkaline solution with a small Tafel slope of 85 mV dec−1 and a low overpotential of 280 and 360 mV to achieve 10 and 100 mA cm−2 in 1.0 M KOH, respectively. The catalyst also exhibited an excellent stability in 1.0 M KOH, with just 12 mV shift after electrolysis at 10 mA cm−2 for 16 h and 27 mV shift after electrolysis at 20 mA cm−2 for another 24 h. In addition, the NiMoO-SP/Ti also displayed high catalytic properties towards HER with a small Tafel slope of 77 mV dec−1 and a low overpotential of 159 mV to obtain 10 mA cm−2 in 1.0 M KOH. After electrolysis at −10 mA cm−2 for 40 h, the overpotential increased by just 25 mV, which demonstrated its high stability for HER in 1.0 M KOH. This work provides an effective route to designing a high-performance catalyst with a favorable structure for the development of electro-catalysts for water splitting.

A convenient and effective strategy to control the surface chemistry of carbon fibres is presented, comprising electro-chemical reduction of aryl diazonium salts onto the surface, followed by ‘click chemistry’ to tether the desired surface characteristic of choice. The power of this approach was demonstrated by engineering a small-molecule interface between carbon fibre and an epoxy matrix improving interfacial shear strength by up to 220%, relative to unmodified control fibres. The techniques used in this work do not impede the fibre performance in tensile strength or Young's modulus. This work provides a platform upon which any carbon fibre-to-resin interface can be easily and rapidly designed and implemented.

The functional properties of multi-component particles are strongly affected by their chemical surface composition, for instance in pharmaceutical and food applications. The powders are often produced from emulsions and solutions by convective drying, such as spray drying. A detailed understanding of the drying and shrinkage kinetics of the material is hereby crucial to optimise process design and product characteristics. In this study, a modified analysis technique was implemented into filament single droplet drying to observe the changes in component distribution of two milk model emulsions with drying time as well as the impact thereof on the water evaporation resistance and shrinkage behaviour. The drying droplets were cryogenically flash-frozen at discrete drying times and, subsequent to freeze-drying, investigated in terms of their chemical surface composition and internal fat and protein distribution. The droplets of a high-fat milk model emulsion were covered by a continuous fat film throughout the whole drying process, whereas the droplets of a low-fat model emulsion featured a surface overrepresentation of protein in comparison to the bulk concentration. The protein further enriched near the surface with increasing drying time. In the high-fat system, the lipid surface film reduced the extent of particle shrinkage and impeded the drying process.

We report the first method to introduce differential functionalities in the interior pore walls and exterior surface of highly stable thermally hydrocarbonised porous silicon (THCpSi) films. The approach exploits the hydrophobicity of the hydrosilylated THCpSi to, first, selectively functionalise the external surface, and subsequently derivatise the hydrophobic internal pore walls Refereed/Peer-reviewed