Due to the MOdular Luminescence Lifetime Imaging system (MOLLI)that has been developed within the last few years it is possible to use oxygen sensors that are not optically isolated. Transparent planar optodes and dispersed nano-optodes for the first time enable a direct optical link between the chemical parameter to be measured (oxygen as an example) and the structure that is responsible for the distribution of the chemical parameter (ascidian and corals as an example). Since the transparency as a principal quality of the optode allows to record structural images. The spatial resolution of the MOLLI imaging system is determined by a)the area size of the view field that is imaged onto the amount of pixels of the CCD-chip (640x480 in our case)and b)by the spatial limitations of the sensing layer. The latter means in case of the planar optode the thickness of the sensing layer and in case of dispersed nano-optodes the thickness of the excitation light field. We present biological applications of transparent planar optodes (thickness approximately equals 5-10 micrometers ) at two areal resolutions,a)50 micrometers /pixel and b)6 micrometers /pixel and one application of nano-optodes at 80 micrometers /pixel. The first application shows the oxygen production of endolithic cells that live in the skeleton of massive corals measured in a cut coral sample that was illuminated through the planar oxygen optode with defined light energy levels to follow the oxygen production of these coral symbionts. Finally the oxygen production and consumption of coral symbionts are shown by dispersed oxygen nano-optodes in the medium. The specific set-up for the latter experiment will be discussed with the future implication of possible 3D measurements. Although the results all come from biological applications from coral reef environments obviously the measuring system and the transparent sensors can be applied to a variety of environmental topics. At the moment similar optodes are under development for parameters like pH,CO₂ and temperature.

Date Published: 22 February 2002
PDF: 11 pages
Proc. SPIE 4576, Advanced Environmental Sensing Technology II, (22 February 2002); doi: 10.1117/12.456961

Published in SPIE Proceedings Vol. 4576:
Advanced Environmental Sensing Technology II
Tuan Vo-Dinh; Stephanus Buettgenbach, Editor(s)