SUBMILLISECOND RESPONSE-TIMES OF OXYGEN-QUENCHED LUMINESCENT COATINGS

An apparatus and data analysis methodology is described which allows determination of response time to oxygen concentration changes of luminescent oxygen sensor coatings. Utilizing a solenoid valve, a sample chamber creates a pressure jump from 0.1 to 700 Torr in 600 mus that is followed by 15 ms of ringing. An optical detection system measures the response of porphyrin-based luminescent oxygen sensors to the pressure jump. The pressure in the chamber is measured simultaneously and independently with a piezoresistive pressure transducer. Data analysis techniques using nonlinear least-squares and numerical convolution of the luminescent response to the pressure rise allow determination of response times of the oxygen sensor. The response to pressure jumps of several luminescent oxygen sensitive coatings designed for video luminescent barometry are measured with this computer-controlled instrument. Several coatings were studied with response times of approximately 2.5 s, approximately 400 ms, 11 ms, 1.5 ms, and <25 mus. Studies of the system suggest that we can determine response times down to about 10 mus.