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The luminophore will then transfer parts of its excitation energy to the colliding molecule, with the result
that less photons (giving a shorter life time) are emitted from the luminophore. This effect is called
dynamic luminescence quenching, and in the Oxygen Optode the colliding molecules are O
The luminophore used in the Oxygen Optode is a special molecule called platinum porphyrine. These
luminophores are embedded in a polymer layer, called the indicator layer (coated on a thin film of
polyester support).
To avoid potential influence from fluorescent material surrounding the sensor or direct incoming sunlight
when measuring in the photic zone, the normal monitoring foil is also equipped with a black gas
permeable coating.
The coating gives optical isolation between the indicator layer and the surroundings. For faster response
time foils also exist without the optical isolation layer, transparent foils, through which the blinking blue
and red light can be seen. The transparent foils are only available for 4330 and 4831 optodes.
O
O
O
O
2
2
2
2
O
O
2
2
O
O
2
2
O
O
O
O
2
2
2
2
Figure A 2 Sensing Foil
Luminescence Decay Time
Due to its fluorescent behaviour the sensing foil will return a red light when it is excited with a blue-green
light (505 nm). If there is O
The amount of returned light will therefore depend on the O
The intensity of the returned light is however not the optimal property to measure since it depends on
many other factors as i.e. optical coupling or bleaching of the foil.
Since the returned light is delayed with respect to the excitation light, the presence of O
influence the delay.
This property is called luminescence decay time (or lifetime) and it will decrease with increasing
O
concentrations.
2
O
O
2
2
O
O
2
2
O
O
2
2
Optical Isolation Layer
Optical Isolation Layer
O
O
O
O
Indicator Layer
Indicator Layer
2
2
2
2
Support Layer
Support Layer
present this fluorescent effect will be quenched.
2
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TD 269 OPERATING MANUAL
OXYGEN OPTODE 4330, 4831, 4835
June 2017
concentration in the foil.
2
.
2
will also
2
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