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Abstract: Photoelectrochemical (PEC) hydrogen production, using sunlight to directly split water, is one of the key enabling technologies for a future where hydrogen is widely deployed as an energy carrier. However, the “traditional” semiconductor-based PEC material systems studied to date, including simple metal oxides such as TiO2, WO3 and Fe2O3, have not been successful in meeting all the performance, durability and cost requirements for practical hydrogen production. Technology-enabling advances in the development of new, advanced PEC materials and systems have been needed. Toward this end, the International Energy Agency''s Hydrogen Implementation Agreement (IEA-HIA) Task-26, working in close conjunction with “Working Group on PEC Hydrogen Production” in the Fuel Cell Technology Program at the U.S. Department of Energy, has brought together experts in materials theory, synthesis, characterization and analysis from research sectors across the world. This endeavor has resulted in exciting recent progress over a broad range of PEC materials classes, including high efficiency crystalline semiconductors (e.g., III-V materials), promising thin-film semiconductors (including Fe2O3-,WO3-, and CuGaSe2- based films), novel photocatalyst powders (such as Cs-Modified WO3) and innovative photocatalyst nano-particles (e.g., MoS2). The research and development progress in these important PEC materials classes will be summarized, and key implications discussed. [Copyright &y& Elsevier]

Abstract: In the context of photoelectrochemical water-splitting, tungsten oxide films have been fabricated at low processing temperatures ) by reactive sputtering from tungsten targets in an argon/oxygen ambient. The films have a dense, compact morphology and show columnar growth. Amorphous and highly polycrystalline films can be produced depending on the deposition conditions; polycrystalline phases appear only at higher temperatures and under certain sputter target conditions. Large crystallites proved beneficial to photoelectrochemical performance. A maximum photocurrent of (at 1.6V vs SCE) was observed in under AM 1.5 Global illumination, exceeding published results for material fabricated at higher temperatures (in the range). Doping of sputtered tungsten oxide films with nitrogen results in a red-shifted absorption edge, but so far not in increased photocurrents. The maximum photocurrent of a nitrogen-doped sample was measured at (at 1.6V vs SCE). A multi-junction photoanode based on the best available sputtered film and an amorphous silicon photovoltaic device is projected to operate at 2.2% solar-to-hydrogen efficiency. [Copyright &y& Elsevier]

The development of a low-temperature reactive-sputtering process for producing high-quality hematite films was explored. Iron oxide thin films were sputter-deposited under different conditions of oxygen partial pressure and at substrate temperatures up to 200 °C, and characterized for comparison. Although all sample films exhibited structural and compositional characteristics consistent with polycrystalline rhombohedral Fe2O3 (hematite), it was found that the detailed grain features and morphology, as well as the optical and electrical properties, were significantly altered by process parameter variations. Average grain size increased with deposition temperature and decreased with oxygen partial pressure. Measured film conductivities ranged from 10-9 S/cm in 100 °C samples up to 5×10-4 S/cm in the 200 °C samples. Highest conductivities were found in the sample films exhibiting the largest grains, which is attributed to the effects of mobility enhancement through reduced inter-grain scattering. [Copyright &y& Elsevier]

A multijunction photoelectrode for hydrogen production is being developed at the University of Hawaii (UH) which incorporates an Fe2O3/electrolyte photoelectrochemical top junction with two underlying amorphous silicon/germanium (a-Si:Ge) solid-state junctions. The device structure is fabricated onto stainless-steel foil, which is coated on the back surface with a thin film of nickel–molybdenum hydrogen catalyst, also developed at UH. The Fe2O3 films for this photoelectrode were initially based on a pyrolytically deposited material developed at Duquesne University which has demonstrated rectifying behavior in alkaline electrolyte with a broad absorption spectra in the 300–500 nm range, and photo-generated currents exceeding 8 mA/cm2 for 1 sun illumination. An investigation into the use of reactively sputtered films, which can be synthesized at lower temperatures than the spray-pyrolytic material, has also been initiated. The a-Si:Ge tandem “nipnip” structure for the initial photoelectrode design is based on the bottom and middle layers of the high-efficiency triple junction photovoltaic devices developed by the University of Toledo. These monolithically stacked solid-state structures, which absorb strongly in the 500–700 and 600–900 nm ranges provide the supplementary voltage bias needed to sustain the hydrogen and oxygen evolution reactions, respectively, occurring simultaneously at the catalyzed back surface and the Fe2O3 front surface, respectively. Performance and stability results from initial tests of fabricated prototype photoelectrodes in potassium hydroxide under simulated AM1.5 illumination are presented. Also, efforts to optimize the device design using bandgap and thickness tailoring for improved optics and current matching are described. [Copyright &y& Elsevier]

Consumer perception of poor hygiene of fresh milk products is a major barrier to promotion of milk consumption as an intervention to alleviate the burden of malnutrition in Ghana. Fresh milk is retailed raw, boiled, or processed into unfermented cheese and spontaneously fermented products in unlicensed outlets. In this study, we have determined microbiological quality of informally retailed fresh milk products and characterized the genomic diversity and antimicrobial resistance (AMR) patterns of non-typhoidal Salmonella (NTS) in implicated products. A total of 159 common dairy products were purchased from five traditional milk markets in Accra. Samples were analysed for concentrations of aerobic bacteria, total and fecal coliforms, Escherichia coli , staphylococci, lactic acid bacteria and yeast and moulds. The presence of Salmonella , E . coli O157:H7, Listeria monocytogenes and Staphylococcus aureus were determined. AMR of Salmonella against 18 antibiotics was experimentally determined. Genome sequencing of 19 Salmonella isolates allowed determination of serovars, antigenic profiles, prediction of AMR genes in silico and inference of phylogenetic relatedness between strains. Raw and heat-treated milk did not differ significantly in overall bacterial quality ( P  = 0.851). E . coli O157:H7 and Staphylococcus aureus were present in 34.3% and 12.9% of dairy products respectively. Multidrug resistant (MDR) Salmonella enterica serovars Muenster and Legon were identified in 11.8% and 5.9% of unfermented cheese samples respectively. Pan genome analysis revealed a total of 3712 core genes. All Salmonella strains were resistant to Trimethoprim/Sulfamethoxazole, Cefoxitin, Cefuroxime Axetil and Cefuroxime. Resistance to Chloramphenicol (18%) and Ciprofloxacin (100%), which are first line antibiotics used in treatment of NTS bacteremia in Ghana, was evident. AMR was attributed to presence and/or mutations in the following genes: golS , sdiA for cephalosporins, aac(6′)-Iy , ant(9) for aminoglycosides, mdtK , gyrA , gyrB , parC , parE for quinolones and cat1 , cat4 for phenicols. Phylogenetic analysis based on accessory genes clustered S . Legon strains separately from the S . Muenster strains. These strains were from different markets suggesting local circulation of related strains. Our study justifies consumer resistance to consumption of unripened soft cheese without further lethal heat treatment, and provides evidence that supports the Ghana Health Service recommendation for use of 3rd generation cephalosporins for the treatment of MDR NTS infections. [ABSTRACT FROM AUTHOR]

To simultaneously overcome the challenges imposed by the nature of optical imaging characterized by a range of artifacts including space-varying signal to noise ratio (SNR), scattered light, and non-uniform illumination, we developed a novel method that segments the 3-D vasculature directly from original fluorescence microscopy images eliminating the need for employing pre- and post-processing steps such as noise removal and segmentation refinement as used with the majority of segmentation techniques. Our method comprises two initialization and constrained recovery and enhancement stages. The initialization approach is fully automated using features derived from bi-scale statistical measures and produces seed points robust to non-uniform illumination, low SNR, and local structural variations. This algorithm achieves the goal of segmentation via design of an iterative approach that extracts the structure through voting of feature vectors formed by distance, local intensity gradient, and median measures. Qualitative and quantitative analysis of the experimental results obtained from synthetic and real data prove the efficacy of this method in comparison to the state-of-the-art enhancing-segmenting methods. The algorithmic simplicity, freedom from having a priori probabilistic information about the noise, and structural definition gives this algorithm a wide potential range of applications where i.e. structural complexity significantly complicates the segmentation problem. [ABSTRACT FROM AUTHOR]

Abstract: For optimal performance, the intermediate window layer in multijunction photovoltaics should transmit as much light as possible to guarantee maximum device efficiency. In this work, we demonstrate that indium molybdenum oxide (IMO) is a more suitable intermediate layer, compared to indium tin oxide (ITO), as it would absorb significantly less infrared light with comparable electrical conductivity once integrated into a multijunction solar cell. In fact, we show that IMO optoelectronic properties are virtually unchanged by the typical thermal budgets used in solar absorber deposition processes used in low-cost high-performance multijunction photovoltaics (e.g. CuInGaSe2). Specifically, IMO and ITO thin films were reactively sputtered onto glass substrates at 150°C, then subjected to a vacuum annealing process (550°C, 2h) identical to that of co-evaporated copper gallium diselenide (CGSe), a candidate material for the top absorber in multijunction cells. We found that annealing substantially reduces the infrared transmittance of ITO starting at 900nm, reducing by 2.5% per 100nm, while IMO only started experiencing a reduction at 1400nm and decaying more slowly at 1.6% per 100nm. Furthermore, the resistivity of IMO was comparable to that of ITO after annealing. The resilience of IMO to such high temperature processes show that it has potential to enhance the performance of multijunction devices. [Copyright &y& Elsevier]