Low power hydrogen gas sensors using electrodeposited PdNi-Si Schottky diodes

The use of electrodeposited PdNi-Si Schottky barriers as low power Hydrogen sensors is investigated. The Palladium content of the film causes the Hydrogen molecules to dissociate and be absorbed by the film, changing the metal work function and Schottky barrier current. In this work we show that electrodeposited Pd(Ni)-Si Schottky barriers exhibit very low reverse bias currents compared to evaporated Schottky diodes. The Schottky diodes were fabricated on 0.5-1.5 ohmcm 100 n-type Si by electrodeposition of PdNi followed by evaporation of Aluminium contact pads. Electrical measurements at different Hydrogen pressures were performed on back to back Schottky diodes in a vacuum chamber using pure Nitrogen and a 5% Hydrogen-Nitrogen mixture. Very low currents of 1nA were measured in the absence of Hydrogen. Large increases in the currents, upto a factor of 100, were observed upon exposure to different Hydrogen partial pressures. A back to back configuration forms a device that draws extremely low power when idle. The low idle current, simplicity of the fabrication process and ability to easily integrate with conventional electronics proves the suitability of electrodeposited PdNi-Si Schottky barriers as low power Hydrogen sensors

Sensing Dissolved Methane in Aquatic Environments: An Experiment in the Central Baltic Sea Using Surface Plasmon Resonance

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Genetic susceptibility to alcoholic liver disease

A new method for in-situ detection and measurement of dissolved methane in aqueous media/environments with a limit of detection of 0.2 nM (3?, and t90~110s) and range (1-300 nM) is presented. The detection method is based on refractive index (RI) modulation of a modified PolyDiMethylSiloxane (PDMS) layer incorporating molecules of cryptophane-A [1] which have a selective and reversible affinity for methane [2]. The refractive index is accurately determined using surface plasmon resonance (SPR) [3]. A prototype sensor has been repeatedly tested, using a dissolved gas calibration system under a range of temperature and salinity regimes. Laboratory-based results show that the technique is specific, sensitive, and reversible. The method is suitable for miniaturization and incorporation into in situ sensor technology

The chemistry of hyperalkaline springs in serpentinizing environments: 1. the composition of free gases in New Caledonia compared to other springs worldwide

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Freshwater lake to salt-water sea causing widespread hydrate dissociation in the Black Sea

Gas hydrates are maintained via a balance of temperature and pressure, if this changes then destabilization may occur. Here, the authors show instead that due to recent changes in the salinity of the sea water of the Black Sea, gas hydrates may become destabilized with widespread methane seepage

Impact of shallow hydrothermalism on lithium content and lithium isotope composition of marine plankton

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Active hydrothermal vents in the Woodlark Basin may act as dispersing centres for hydrothermal fauna

peer reviewedHere we report the discovery of a high-temperature hydrothermal vent field on the Woodlark Ridge, using ship-born multibeam echosounding and Remotely Operated Vehicle (ROV) exploration. La Scala Vent Field comprises two main active areas and several inactive zones dominated by variably altered basaltic rocks, indicating that an active and stable hydrothermal circulation has been maintained over a long period of time. The Pandora Site, at a depth of 3,380 m, is mainly composed of diffuse vents. The Corto site, at a depth of 3,360 m, is characterized by vigorous black smokers (temperature above 360°C). The striking features of this new vent field are the profusion of stalked barnacles Vulcanolepas sp. nov., the absence of mussels and the scarcity of the gastropod symbiotic fauna. We suggest that La Scala Vent Field may act as a dispersing centre 37 for hydrothermal fauna towards the nearby North Fiji, Lau and Manus basins

Prokaryote Communities at Active Chimney and In-Situ Colonization Devices after a Magmatic Degassing Event (37°N MAR, EMSO-Azores Deep-Sea Observatory)

International audienceThe mixing zone between high temperature hydrothermal fluids and seawater produces redox gradients, promoting the development of unique ecosystems based on chemotrophy. The structure of microbial communities depends on their environment, which can vary according to space and time. Hydrothermal circulation within the oceanic crust determines the chemical composition and flow of fluids, depending on underground events (earthquakes, volcanic episodes....), and impacts the development of microbial communities. This link between hydrothermal vent communities and deep geological events is the focus of the present study, the first of its kind for slow-spreading ridge. In this study, we present a unique set of multidisciplinary data collected from 2008 to 2011 on the Eiffel Tower hydrothermal site (Lucky Strike vent field, Mid-Atlantic Ridge). We benefit from continuous geophysical monitoring (temperature, seismicity) of the site, annual sampling of hydrothermal fluids (hot and diffuse) for geochemistry analyses, sampling of hydrothermal chimneys and an in situ microbial colonization experiments over a year for microbial study. The high CO2 content and concentrations of major elements (Cl, Ca, Si) and SO4 in the end-member fluids collected in 2010, indicate that a magmatic degassing occurred between 2009 and 2010 under the Lucky Strike hydrothermal field. This is supported by the large temperature variations observed in March-April 2010. These magmatic CO2 inputs seem to have affected microbial communities' colonizing the high temperature chimney, as well as the basalts in the more diffuse and mixed zone, promoting the development of thermophilic/ anaerobic Archaea and Bacteria (Archaeoglobales, Nautiliales, Nitratiruptoraceae)

Natural iron fertilization by shallow hydrothermal sources fuels diazotroph blooms in the ocean

International audienceIron is an essential nutrient that regulates productivity in ~30% of the ocean. Compared with deep (>2000 meter) hydrothermal activity at mid-ocean ridges that provide iron to the ocean’s interior, shallow (<500 meter) hydrothermal fluids are likely to influence the surface’s ecosystem. However, their effect is unknown. In this work, we show that fluids emitted along the Tonga volcanic arc (South Pacific) have a substantial impact on iron concentrations in the photic layer through vertical diffusion. This enrichment stimulates biological activity, resulting in an extensive patch of chlorophyll (360,000 square kilometers). Diazotroph activity is two to eight times higher and carbon export fluxes are two to three times higher in iron-enriched waters than in adjacent unfertilized waters. Such findings reveal a previously undescribed mechanism of natural iron fertilization in the ocean that fuels regional hotspot sinks for atmospheric CO 2