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Recent work has demonstrated that, for bimetallic Au–Pd systems, the rate of catalytic alcohol and formyl dehydrogenation (DH) is intrinsically linked to the rate of oxygen reduction (ORR) within the same system.

If hydrogen evolution photocatalysis are to be deployed at industrial scale, the synthesis of these photocatalytic materials must be both economically and environmentally scalable.

The development of high quality, non-toxic (i.e., heavy-metal-free), and functional quantum dots (QDs) via ‘green’ and scalable synthesis routes is critical for realizing truly sustainable QD-based solutions to diverse technological challenges. Herein, we demonstrate the low-temperature all-aqueous-phase synthesis of silver indium sulfide/zinc (AIS/Zn) QDs with a process initiated by the biomineralization of highly crystalline indium sulfide nanocrystals, and followed by the sequential staging of Ag(+) cation exchange and Zn(2+) addition directly within the biomineralization media without any intermediate product purification. Therein, we exploit solution phase cation concentration, the duration of incubation in the presence of In(2)S(3) precursor nanocrystals, and the subsequent addition of Zn(2+) as facile handles under biomineralization conditions for controlling QD composition, tuning optical properties, and improving the photoluminescence quantum yield of the AIS/Zn product. We demonstrate how engineering biomineralization for the synthesis of intrinsically hydrophilic and thus readily functionalizable AIS/Zn QDs with a quantum yield of 18% offers a ‘green’ and non-toxic materials platform for targeted bioimaging in sensitive cellular systems. Ultimately, the decoupling of synthetic steps helps unravel the complexities of ion exchange-based synthesis within the biomineralization platform, enabling its adaptation for the sustainable synthesis of ‘green’, compositionally diverse QDs.

In oxidation reactions catalysed by supported metal nanoparticles with oxygen as the terminal oxidant, the rate of the oxygen reduction can be a limiting factor. This is exemplified by the oxidative dehydrogenation of alcohols, an important class of reactions with modern commercial applications1–3. Supported gold nanoparticles are highly active for the dehydrogenation of the alcohol to an aldehyde4 but are less effective for oxygen reduction5,6. In contrast, supported palladium nanoparticles are less active than gold for dehydrogenation but offer high efficacy for oxygen reduction5,6. This imbalance can be overcome by alloying gold with palladium which gives enhanced activity to both reactions7,8; however, the electrochemical potential of the alloy is a compromise between that of the two metals meaning that although the oxygen reduction is improved in the alloy, the dehydrogenation activity is poorer. Here we show that by separating the gold and palladium components in bimetallic carbon-supported catalysts we can almost double the reaction rate beyond that achieved with a corresponding alloy catalyst. We demonstrate this using physical mixtures of carbon-supported monometallic gold and palladium and a bimetallic catalyst comprising separated gold and palladium regions. Furthermore, we demonstrate electrochemically that this enhancement is attributable to the coupling of separate redox processes occurring at isolated gold and palladium sites. The discovery of this novel catalytic effect, a cooperative redox enhancement (CORE), offers a new approach to the design of multi-component heterogeneous catalysts.

Choreographing nanocrystal biomineralization, cation exchange, and low-temperature annealing enables synthesis of ‘green’ functionalizable quantum dots suitable for bioimaging.

This paper investigates the determinants of participation and performance in post-compulsory education, controlling for the selection into post-compulsory education and prior attainment, using a unique primary dataset on pupils studying in the post-compulsory grade in 2011-2012 from one district of the Punjab province of Pakistan. The main findings of the paper show that participation and performance in post-compulsory education are two different processes, with participation being driven by availability of post-compulsory institutions within travel distance, while performance, once in post-compulsory education, is determined by ability. The results further highlight that distance reduces participation most for those living in rural areas.

We use longitudinal panel data from the EU-SILC for the period 2005-2011 to examine the micro and macro determinants, persistence and dynamics of overeducation. The key contribution in terms of the determinants of over-education is the inclusion of macro-level explanatory variables to control for both aggregate supply and\ud aggregate demand labour market conditions. Their effects are found to be strongly significant and to have the expected sign. The article also disentangles the effect of past over-education experience on the likelihood of current over-education. Results demonstrate that over-education is not only a long-run phenomenon for many workers\ud but also that current over-education is largely due to past circumstances of the individual with this state dependence present at all career stages.

The development of scalable, green, aqueous phase, nanomaterial synthesis routes that do not sacrifice the functional performance of the materials remains a persistent challenge. Bioinspired method...

The international community has developed a series of conventions on civil liability for nuclear damage, which aim to ensure compensation is available for damage, including transboundary damage, caused by a nuclear incident. Those conventions have struggled to gain universal adherence, and the “global regime” called for in 2011 is at best a patchwork quilt, with a number of treaties with differing memberships, and many States (including States with large and growing nuclear sectors) not party to any convention. However, the principles of the conventions are reflected in national laws in most States which operate nuclear power reactors and associated facilities. This chapter assesses the current global nuclear liability regime and discusses a series of recommendations made by the International Expert Group on Nuclear Liability (INLEX) to allow the international community to respond to the continued evolution of the nuclear industry.

We use UK Labour Force Survey data to estimate wage differentials associated with the attainment of vocational qualifications, relative to comparison groups qualified to at best one level below. Our main aim is to show the variation in the size of such differentials, according to the unobserved characteristics of the individual, via quantile regression and also according to the characteristics of the qualifications themselves, in terms of the level, type and subject area. With respect to subject area, the key reason for variation in differentials across subjects is the differences in occupations to which qualifications lead.

CuZnSnS (CZTS) quantum dots (QDs) have potential application in quantum dot sensitized solar cells (QDSSCs); however, traditional synthesis approaches typically require elevated temperatures, expensive precursors, and organic solvents that can hinder large-scale application. Herein we develop and utilize an enzymatic, aqueous-phase, ambient temperature route to prepare CZTS nanocrystals with good compositional control. Nanoparticle synthesis occurs in a minimal buffered solution containing only the enzyme, metal chloride and acetate salts, and l-cysteine as a capping agent and sulfur source. Beyond isolated nanocrystal synthesis, we further demonstrate biomineralization of these particles within a preformed mesoporous TiO2 anode template where the formed nanocrystals bind to the TiO2 surface. This in situ biomineralization approach facilitates enhanced distribution of the nanocrystals in the anode and, through this, enhanced QDSSC performance.

CaTiO3-supported Pt is sometimes referred to as an “Intelligent” catalyst because Pt can reversibly leave or enter the perovskite lattice following high-temperature reduction or oxidation; however,...

In oxidation reactions catalysed by supported metal nanoparticles with oxygen as the terminal oxidant, the rate of the oxygen reduction can be a limiting factor. This is exemplified by the oxidative dehydrogenation of alcohols, an important class of reactions with modern commercial applications

Nanocomposite photocatalysts offer a promising route to efficient and clean hydrogen production. However, the multistep, high-temperature, solvent-based syntheses typically utilized to prepare these photocatalysts can limit their scalability and sustainability. Biosynthetic routes to produce functional nanomaterials occur at room temperature and in aqueous conditions, but typically do not produce high-performance materials. We have developed a method to produce a highly efficient hydrogen evolution photocatalyst consisting of CdS quantum dots (QDs) supported on reduced graphene oxide (rGO) via enzyme-based syntheses combined with tuned ligand exchange-mediated self-assembly. All preparation steps are carried out in an aqueous environment at ambient temperature. Size-controlled CdS QDs and rGO are prepared through enzyme-mediated turnover of l-cysteine to HS

Photocatalysis is an attractive, sustainable, and potentially low-cost route to capture solar energy as fuel. However, current photocatalytic materials synthesis routes are not easily scaled-up to the magnitude required to impact our energy consumption due to both economic and environmental concerns. While the elements utilized are often earth abundant, typical synthetic routes utilize organic solvents at elevated temperatures with relatively expensive precursors. Herein, we demonstrate the fully biomineralized synthesis of a quantum confined CdS/reduced graphene oxide (CdS/rGO) photocatalyst catalyzed by the single enzyme cystathionine γ-lyase (CSE). The synthesis is performed at pH 9 in a buffered aqueous solution, under ambient conditions, and utilizes the low-cost precursors Cd acetate, L-cysteine, graphene oxide, and a poly-L-lysine linker molecule. CSE actively decomposes L-cysteine to generate reactive HS− in aqueous solution at pH 9. Careful selection and control of the synthesis conditions enable both reduction of graphene oxide to rGO, and control over the mean CdS nanocrystal size. The CdS is conjugated to the rGO via a poly-L-lysine crosslinker molecule introduced during rGO formation. The completed CdS/rGO photocatalyst is capable of producing H2, without the aid of a noble metal co-catalyst, at a rate of 550 μmol h−1 g−1 for an optimized CdS/rGO ratio. This rate is double that measured for unsupported CdS and is comparable to CdS/rGO photocatalysts produced using more typical chemical synthesis routes. Single enzyme biomineralization by CSE can produce a range of metal chalcogenides without altering the enzyme or benign approach, making this an easily adaptable procedure for the sustainable production of a wide variety of important photocatalyst systems.

CuZnSnS (CZTS) quantum dots (QDs) have potential application in quantum dot sensitized solar cells (QDSSCs); however, traditional synthesis approaches typically require elevated temperatures, expensive precursors, and organic solvents that can hinder large-scale application. Herein we develop and utilize an enzymatic, aqueous-phase, ambient temperature route to prepare CZTS nanocrystals with good compositional control. Nanoparticle synthesis occurs in a minimal buffered solution containing only the enzyme, metal chloride and acetate salts, and l-cysteine as a capping agent and sulfur source. Beyond isolated nanocrystal synthesis, we further demonstrate biomineralization of these particles within a preformed mesoporous TiO

We analyse the effect of geographic competition between schools on academic performance in Chile. The analysis controls for prior pupil performance, and a range of school and municipality characteristics. We allow for the endogeneity of voucher school location, using the number of local Catholic churches as an instrument. We find that a larger number of public schools positively affects the quality of education of other schools located in the same area, particularly amongst middle-class families and in middle-ranking schools. However, the number of voucher schools is associated with lower performance in neighbouring schools, which we attribute to pupil sorting.

Solid Oxide Fuel Cells (SOFC) with La0.3Sr0.7TiO3 (LST)–yttria-stabilized ZrO2 (YSZ) anodes were prepared by impregnation of LST into porous YSZ scaffolds and then modified by Atomic Layer Deposition (ALD) of Ni, Pt, Pd, Fe, Co. and CeO2. Weight loadings as low as 0.01% of Pt, Ni, and Pd were sufficient to decrease anode impedances by orders of magnitude for operation in humidified H2 at 973 K. The effects of CeO2, Co, and Fe were less but still significant. Sintering at higher temperatures was important. Possible ways of stabilizing the metal particles and implications for developing ceramic anodes are discussed.

The effect of catalyst addition on H2 evolution from composite electrodes of La0.7Sr0.3TiO3 (LST) and BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) was studied. Starting with symmetric cells (LST∣∣BZCYYb∣∣LST), Pt was added to one or both electrodes, after which i–V polarization measurements were performed in humidified H2 at 723 and 773 K. The base cells showed very high impedances but these decreased dramatically upon addition of Pt to both electrodes. When Pt was added to only one electrode, the cells performed as diodes, showing that Pt was necessary for H2 dissociation but not for H recombination. The effects of adding Ru, W, Re and Fe were also studied. DFT calculations helped confirm that H recombination on BaZrO3 is expected to be barrierless. The implications of these results for potential application to electrochemical synthesis of ammonia are discussed.

This work demonstrates a bioenabled fully aqueous phase and room temperature route to the synthesis of CuInS2/ZnS core/shell quantum confined nanocrystals conjugated to IgG antibodies and used for fluorescent tagging of THP-1 leukemia cells. This elegant, straightforward and green approach avoids the use of solvents, high temperatures and the necessity to phase transfer the nanocrystals prior to application. Non-toxic CuInS2, (CuInZn)S2, and CuInS2/ZnS core/shell quantum confined nanocrystals are synthesized via a biomineralization process based on a single recombinant cystathionine γ-lyase (CSE) enzyme. First, soluble In-S complexes are formed from indium acetate and H2S generated by CSE, which are then stabilized by l-cysteine in solution. The subsequent addition of copper, or both copper and zinc, precursors then results in the immediate formation of CuInS2 or (CuInZn)S2 quantum dots. Shell growth is realized through subsequent introduction of Zn acetate to the preformed core nanocrystals. The size and optical properties of the nanocrystals are tuned by adjusting the indium precursor concentration and initial incubation period. CuInS2/ZnS core/shell particles are conjugated to IgG antibodies using EDC/NHS cross-linkers and then applied in the bioimaging of THP-1 cells. Cytotoxicity tests confirm that CuInS2/ZnS core/shell quantum dots do not cause cell death during bioimaging. Thus, this biomineralization enabled approach provides a facile, low temperature route for the fully aqueous synthesis of non-toxic CuInS2/ZnS quantum dots, which are ideal for use in bioimaging applications.

Biomineralization is an intriguing route towards the low temperature, aqueous phase, green synthesis of inorganic functional nanomaterials. Herein we describe the biomineralization and optical properties of ZnxCd1−xS and ZnxCd1−xS–ZnS quantum confined nanocrystals that have potential application in optoelectronics. The reported biomineralization process is reduced to perhaps its simplest form wherein a single recombinant cystathionine γ-lyase (CSE) enzyme is responsible for catalyzing mineralization within an otherwise inert solution and plays a role in controlling the alloy composition. The biomineralized nanocrystals are sphalerite structured with average diameter below 3 nm. Biomineralization of a passivating ZnS shell on Zn0.73Cd0.27S core nanocrystals is achieved through subsequent addition of Zn precursor. This shell growth increases the photoluminescence quantum yield to 7% and increases the radiative decay time to 97.6 ns compared with 40.9 ns for the core materials.

An engineered strain of Stenotrophomonas maltophilia (SMCD1) is capable of the direct extracellular biomineralization of CdS quantum dot nanocrystals from buffered aqueous solution of cadmium acetate and l-cysteine without the addition of a chemically reactive precursor. Nanocrystal synthesis is strongly influenced by both the l-cysteine/cadmium acetate ratio and pH of the solution. The observed trends are consistent with l-cysteine acting as both a sulfur source and nanocrystal capping agent. Enzymatic turnover of l-cysteine by a putative cystathionine γ-lyase forms reactive sulfur in solution, removing the requirement for addition of reactive sodium sulfide typical of most other biomineralization approaches. The utility of the biomineralized quantum dots is demonstrated by phase transfer from the aqueous to the organic phase and subsequent incorporation into a quantum dot sensitized solar cell and chemical growth of a ZnS shell onto the biomineralized CdS core.

The crystal structure and oxygen stoichiometry of the proposed double perovskite solid oxide fuel cell (SOFC) anode material PrBaMn2O5+δ were determined under SOFC anode conditions via in-situ neutron diffraction. Measurements were performed in reducing atmospheres between 692 K and 984 K. The structure was fit to a tetragonal (space group P4/mmm) layered double perovskite structure with alternating Pr and Ba A-site cation layers. Under all conditions examined, the oxygen sites in the Ba and Mn layers were fully occupied, while the sites in the Pr layer were close to completely vacant. The results of the neutron diffraction experiments are compared to previous thermogravimetric analysis experiments to verify the accuracy of both experiments. PrBaMn2O5+δ was shown to be stable over a wide range of reducing atmospheres similar to anode operating conditions in solid oxide fuel cells without significant structural changes.

Traditional quantum dot synthesis techniques rely on the separation of nucleation and growth to control nanocrystal size. However, the same goal can be achieved through slow and continuous introduction of reactive precursors to keep the growth mechanism in the size focusing regime throughout synthesis. In this work, we demonstrate the efficacy of this approach within the framework of functional material biomineralization where, despite simultaneous nucleation and growth of particles, this growth mechanism enables size-controlled nanocrystal synthesis. Herein, the single enzyme cystathionine γ-lyase (CSE) is utilized to biomineralize CdS nanocrystals via the slow, but continuous turnover of the amino acid l-cysteine to produce H2S. Nanocrystal nucleation and growth theories confirm that consistent addition of monomers will result in a high supersaturation term, driving the nanocrystal growth mechanism into the size focusing regime. We further confirm this theory by mimicking biomineralization via chemical routes and demonstrate the influence of varying supersaturation, to further control the average nanocrystal size. Finally, altering the chelation strength of the capping agent l-cysteine is found to play a key role in balancing nanocrystal growth in solution and long-term stability.

Biomineralization utilizes biological systems to synthesize functional inorganic materials for application in diverse fields. In the current work, we enable biomineralization of quantum confined PbS and PbS–CdS core–shell nanocrystals and demonstrate their application in quantum dot sensitized solar cells (QDSSCs). An engineered strain of Stenotrophomonas maltophilia is utilized to generate a cystathionine γ-lyase that is active for the biomineralization of metal sulfide nanocrystals from a buffered aqueous solution of metal salts and L-cysteine. In the presence of lead acetate, this enzymatic route generates rock salt structured PbS nanocrystals. Controlling the growth conditions yields ∼4 nm PbS crystals with absorption and photoluminescence peaks at 910 nm and 1080 nm, respectively, consistent with the expected strong quantum confinement of PbS at this size. Quantum yields (QY) of the biomineralized PbS quantum dots, determined after phase transfer to the organic phase, range between 16 and 45%. These are the highest reported QY values for any biomineralized quantum dot materials to date and are comparable with QYs reported for chemically synthesized materials. Subsequent exposure to cadmium acetate results in the biomineralization of a thin CdS shell on the PbS core with a resultant blue-shift in optical properties. The photoluminescence peak shifts to 980 nm, consistent with the expected decrease in band gap energy of a PbS–CdS core–shell heterostructured quantum dot. HAADF-STEM imaging confirms the crystalline structure and size of the particles with complimentary XEDS analysis confirming the presence of Cd, Pb, and S in individual nanocrystals. Integration of these QDs into QDSSCs yields open circuit potentials of 0.43 V and 0.59 V for PbS and PbS–CdS, respectively, consistent with expectations for these materials and previously reported values for chemically synthesized QDs.

© 2015 The Authors. Active labour market policies are popular tools used by governments to help get unemployed people back into work. It is a common problem that interventions of this type are often established with no equivalent control group on which to base an evaluation of programme effectiveness. This study uses propensity score matching to evaluate the success of an active labour market policy (the Welsh Assembly's 'Want2Work' programme) that cannot otherwise be evaluated using standard parametric techniques. Using a range of matching and estimation methods, sub-samples and types of job, the scheme was successful. Our most conservative estimate indicates that participants were 7 percentage points more likely to find employment than a control group of non-treated job-seekers. The method adopted here is a useful addition to the real world policy evaluation tool kit, where programme effectiveness needs to be judged in the absence of an established control group. Our results provide evidence that even those who are currently out of the labour market and on health related benefits can find work with the help of appropriately designed support.

This paper uses microdata for 19 African countries to examine the gender difference in maths test scores amongst primary school children. There is a significant difference in maths test scores in favour of boys, similar to that previously observed in developed countries. This difference cannot be explained by gender differences in school quality, home environment, or within-school gender discrimination in access to schooling inputs. However, the gender gap varies widely with characteristics of the regions in which the pupils live, and these regional characteristics are more predictive of the gender gap than parental education and school characteristics, including teacher gender. At the cross-country level, differences in fertility rates account for nearly half the variation in the gender gap, and this relationship is not due to the correlation between fertility and GDP nor to gender (in)equality as measured by the Gender Gap Index.

Ceria substitutionally doped with copper is a promising heterogeneous catalyst for a range of oxidation reactions. Herein we describe the aqueous phase, scalable, and direct precipitation of CuxCe1−xO2−δ (x = 0–0.35) solid solution oxide nanocrystals at room temperature without the need for calcination at elevated temperatures. This direct precipitation of the crystalline oxide is enabled through ligand exchange prior to pH adjustment to prevent the precipitation of the hydroxide phase. By producing particles at room temperature, dopant exsolution and particle growth by sintering can be minimized and/or controlled. Using our methodology, copper dopant concentrations of up to 35 mol% could be produced in 1.7 nm diameter ceria nanocrystals. The resulting materials showed high catalytic activity towards both the water gas shift reaction (WGS) and CO oxidation, with improved performance following the trend of increasing copper content. In comparison to pure ceria nanocrystals, the WGS activation energy decreased from 89.0 to 49.2 kJ mol−1 and the CO oxidation light-off temperature decreased from 262 to 159 °C at a space velocity of 25 000 h−1 upon doping with 35 mol% copper.

Nature provides powerful but as-yet largely unharnessed methods for low-cost, green synthesis of inorganic functional materials such as quantum dots. These materials have diverse applications from medicine to renewable energy. Harnessing nature's unique ability to achieve cost effective and scalable manufacturing solutions with reduced environmental impact is integral to realizing a future biomanufacturing economy. To address this challenge, a bacterial strain has been engineered to enable biosynthesis of CdS nanocrystals with extrinsic crystallite size control in the quantum confinement range. This strain yields extracellular, water-soluble quantum dots from low-cost precursors at ambient temperatures and pressure. The biomanufacturing approach demonstrated here produces CdS semiconductor nanocrystals with associated size-dependent band gap and photoluminescent properties.

Ruddlesden–Popper structured oxides, general form An+1BnO3n+1, consist of n-layers of the perovskite structure stacked in between rock-salt layers, and have potential application in solid oxide electrochemical cells and ion transport membrane reactors. Three materials with constant Co/Fe ratio, LaSrCo0.5Fe0.5O4−δ (n = 1), La0.3Sr2.7CoFeO7−δ (n = 2), and LaSr3Co1.5Fe1.5O10−δ (n = 3) were synthesized and studied via in situ neutron powder diffraction between 765 K and 1070 K at a pO2 of 10−1 atm. The structures were fit to a tetragonal I4/mmm space group, and were found to have increased total oxygen vacancy concentration in the order La0.3Sr2.7CoFeO7−δ > LaSr3Co1.5Fe1.5O10−δ > LaSrCo0.5Fe0.5O4−δ, following the trend predicted for charge compensation upon increasing Sr2+/La3+ ratio. The oxygen vacancies within the material were almost exclusively located within the perovskite layers for all of the crystal structures with only minimal vacancy formation in the rock-salt layer. Analysis of the concentration of these vacancies at each distinct crystallographic site and the anisotropic atomic displacement parameters for the oxygen sites reveals potential preferred oxygen transport pathways through the perovskite layers.

Labour market polarisation involves a decline in the share of intermediate-skilled jobs in the labour market, with a corresponding growth in the share of both low-skill and high-skill jobs. This phenomenon has been observed in a range of countries and time periods. This chapter summarises currently available evidence on the existence of polarisation, and then provides a discussion of why polarisation has occurred. This discussion focusses on technological change, offshoring, international trade and provision of ‘home production’ services as potential explanations, and the evidence for each. Technological change that is ‘task-biased’, in the sense that it is replacing labour in jobs involving routine, repetitive tasks, emerges as a key explanation for polarisation, given that routine tasks are typically found in intermediate-level jobs, for example, administrative and skilled manual work. Given this, the chapter concludes with a discussion of the implications of such polarisation for education. It is argued that despite the declining share of jobs originally classified as intermediate, it is still important for countries to provide, and young people to acquire, intermediate-level qualifications, primarily via vocational and technical education. Although older intermediate-level jobs are disappearing, new ones are emerging, involving tasks complementary to, rather than substituted by, the new technology. Furthermore, education remains one of the primary determinants of progression to higher-level jobs.

Given the UK finance sector is one of the largest in the world, it provides the perfect setting for a study into the nature of the finance sector wage premium. We reveal the pervasiveness of this premium, across all sub-sectors of finance, and across all occupations within finance, and with the very highest rewards going to 40-49 year old men working in London. Moreover, the UK premium has continued to rise despite the recent financial crisis. Consequently, this study uses rich data from the UK to investigate potential explanations. We find that the financial sector is more skill intensive but also that financial sector workers have higher childhood test scores vis-à-vis non-finance workers. So we investigate to what extent these higher qualifications and higher cognitive skills can explain the financial pay differential. We then go on to consider whether the financial premium is a consequence of differences in job characteristics and thus whether technological change can explain the growth in the premium. While each of these factors has some role to play, we find that none can fully explain the wage premium found in the financial sector, which we find to be pervasive across 17 OECD countries, including the US. We therefore attribute to this to rent-sharing.

This work demonstrates a bioenabled fully aqueous phase and room temperature route to the synthesis of CuInS

Biomineralization is the process by which biological systems synthesize inorganic materials. Herein, we demonstrate an engineered cystathionine γ-lyase enzyme, smCSE that is active for the direct aqueous phase biomineralization of CdSe and CdSe-CdS core-shell nanocrystals. The nanocrystals are formed in an otherwise unreactive buffered solution of Cd acetate and selenocystine through enzymatic turnover of the selenocystine to form a reactive precursor, likely H2Se. The particle size of the CdSe core nanocrystals can be tuned by varying the incubation time to generated particle sizes between 2.74 ± 0.63 nm and 4.78 ± 1.16 nm formed after 20 min and 24 h of incubation, respectively. Subsequent purification and introduction of l-cysteine as a sulfur source facilitates the biomineralization of a CdS shell onto the CdSe cores. The quantum yield of the resulting CdSe-CdS core-shell particles is up to 12% in the aqueous phase; comparable to that reported for more traditional chemical synthesis routes for core-shell particles of similar size with similar shell coverage. This single-enzyme route to functional nanocrystals synthesis reveals the powerful potential of biomineralization processes.

Proton-conducting oxides, BaZrO3 (BZ) and BaCeO3 (BC), were investigated as potential support materials for Cr catalyst (0.2–0.6 wt % Cr, Cr/BZ or BC) in ethane dehydrogenation at short contact times. The catalytic activity, selectivity in ethane dehydrogenation, and carbon formation were determined. A higher ethylene formation rate was obtained on Cr/BZ in comparison to Cr/BC: 1.4 × 10–7 and 6.2 × 10–8 mol/m2 s at 575 °C at 1 min on stream for 1 g of 0.2 Cr/BZ and 0.2 Cr/BC, respectively. The selectivity was maintained above 94% over all samples in the temperature range 475–575 °C. The catalytic activity toward ethane dehydrogenation was more than 1 order of magnitude higher for the proton-conducting supports when in comparison to a Cr/γ-Al2O3 catalyst with similar surface Cr coverage. X-ray photoelectron spectroscopy (XPS) revealed an initially higher concentration of Cr6+ on Cr/BC in comparison to Cr/BZ, corresponding to a plateau of relatively high activity at short times on stream. This plateau is at...

The surface oxygen exchange rates for NdBaCo 2 O 5 + d (NBCO), PrBaCo 2 O 5 + d (PBCO), and GdBaCo 2 O 5 + d (GBCO) were measured between 573 K and 973 K using an isotopic pulse exchange technique. Impedance spectroscopy was utilized to compare these surface rates with electrode performance. Both experiments showed NBCO to be the most active material, with both PBCO and GBCO approximately equal but with lower surface exchange rates and higher electrode area specific resistance. A discontinuity in both data sets was linked to a crystal phase transition in GBCO. It is proposed that the electrode performance is limited by the oxygen exchange rate.

The effect of adding transition-metal catalysts to the surfaces of Solid-Oxide-Fuel-Cell (SOFC) cathodes was examined. Monolayer amounts of Pd, Ni, and Co were deposited by atomic layer deposition (ALD) to cathodes prepared by impregnation of La0.8Sr0.2FeO3 (LSF), La0.8Sr0.2CoO3 (LSCo), and La0.6Sr0.4 Co0.2Fe0.8O3 (LSCF) into YSZ scaffolds. Incorporating the catalysts by ALD allowed modification of the surface composition without changing the cathode surface area or structure. X-ray Photoelectron Spectroscopy and High Sensitivity-Low Energy Ion Scattering were used to confirm ALD growth rates that were measured gravimetrically. Electrochemical impedance spectroscopy indicated that the addition of Pd had a small negative effect on all of the cathodes. Ni and Co exhibited only a small effect on LSCo and LSCF cathodes but both decreased the cathode impedance for LSF. It is suggested that an essential feature in cathode promotion by Co and Ni is that these cations are incorporated into the perovskite surface and thereby increase the concentration of oxygen vacancies, while Pd only blocked adsorption sites.

Functional nanomaterials are at the core of many innovations in renewable energy generation and catalysis. However, many of these materials are currently synthesized through high temperature, multi-step processes that utilize organic solvents and expensive precursors. These factors increase the complexity and economic and environmental costs of manufacturing scale-up. In contrast, biomineralization, the process by which biological systems produce structural nanomaterials, occurs under ambient conditions in aqueous media utilizing readily available precursors. We have developed a novel single enzyme route for the direct, scalable and controlled synthesis of a variety of pure and hetero-structured metal chalcogenide quantum dots. This approach represents perhaps the simplest biosynthesis system for these materials, consisting of only the single enzyme, a metal precursor, and amino acid sulfur source, and capping agent in an ambient temperature, buffered, aqueous solution. However, tight control of the growth parameters yields size and composition controlled crystalline materials and heterostructures with functional properties comparable to materials synthesized by traditional chemical routes. We demonstrate the application of this approach to direct biomineralization of quantum dots within solar cell photoanodes, and in fully biomineralized quantum dot/reduced graphene oxide photocatalysts.