Fabrication and test of sol–gel based planar oxygen optodes for use in aquatic sediments |
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Authors: | Bettina Knig Oliver Kohls Gerhard Holst Ronnie N Glud Michael Kühl |
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Institution: | aMax-Planck-Institute for Marine Microbiology, Celsiusstr. 1, D-28359 Bremen, Germany;bMarine Biological Laboratory, Institute of Biology, University of Copenhagen, Strandpromenaden 5, DK-3000 Helsingør, Denmark |
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Abstract: | We describe the fabrication of organically modified sol–gel (ORMOSIL) planar optodes for mapping the two-dimensional oxygen distribution in sediments. All sensor foils were based on the use of ruthenium(II)-tris-(4,7-diphenyl-1,10-phenantrolin)-perchlorate, which is a fluorescent dye quenched dynamically by oxygen. Sensors made with different sol–gel immobilisation matrices, different concentrations of precursors and indicator dye, as well as different types of scattering particles co-immobilised in the sensor foil were investigated systematically. Optimal sensor performance was obtained with dye concentrations of 2–10 mmol/kg in an immobilisation matrix made of diphenyldiethoxy-silan and phenyltriethoxy-silan precursors with addition of organically coated TiO2 particles. The sensors exhibited a good mechanical stability and a high sensitivity from 0% to 100% oxygen, which remained constant over at least 36 days. The planar optodes were used with a fluorescent lifetime imaging system for direct mapping of the spatio-temporal variation in oxygen distribution within marine sediment inhabited by the polychaete Hediste diversicolor. The measurements demonstrated the spatio-temporal heterogeneity of the oxygen distribution in bioturbated sediments due to burrow structures and non-constant irrigation activity of the polychaete, which is difficult to resolve with microsensors or with traditional biogeochemical techniques. |
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Keywords: | ORMOSIL Planar oxygen optodes 2D O2 distribution Bioturbation Sediment Polychaete Worm burrow Hediste diversicolor |
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