Luminescent dual sensor for time-resolved imaging of pCO2 and pO2 in aquatic systems

An optical dual sensor for the two-dimensional detection of pCO(2) and pO(2) is described. Tris(tetraoctylammonium)-8-hydroxypyrene-1,3,6-trisulfonate ((TOA)(3)HPTS) acting together with the lipophilic buffer tetraoctylammonium hydrogen carbonate ((TOA)HCO3) as pCO(2)-sensing system along with the oxygen indicator tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) bis(3-(trimethylsilyl)-1-propanesulfonate) (Ru(dpp)(3)TMS2) are incorporated into a single layer ethyl cellulose matrix. A second layer of black silicone rubber served as an optical isolation. The two indicators were simultaneously excited with a 460-nm LED, and a fast-gateable CCD camera was used as the detector. The time-gated imaging scheme enables the mapping of pCO(2) and pO(2) within one measurement, where images in three different time windows during and after a series of square-shaped excitation pulses are recorded. A numerical evaluation method for the resolution of the single parameter maps from these three overall images is described. The response of the sensor has been optimized for use in aquatic systems.