Preparation and calibration of pressure-sensitive and temperature-sensitive paints for fluorescence lifetime imaging applications

This thesis describes various methods for time-resolved luminescence lifetime determination, and their applications to imaging barometric pressure and temperature. These approaches are superior to luminescence intensity imaging in that they are less influenced by sources of errors like light scattering, inhomogeneous indicator distribution, photobleaching, or background fluorescence because they are intrinsically referenced. The data obtained are precise and unambiguous. Novel sensor materials and methods for time-resolved imaging are described, characterized, and applied. A novel dual pressure-sensitive paint (PSP) and temperature-sensitive paint (TSP) system for time resolved luminescence imaging is introduced, consisting of a platinum porpholactone and a ruthenium-diimine complex,. The dual paint was applied to an aircraft model for wind tunnel testing. The dual paint has proven to be applicable for aerodynamic research. Temperature can be determined with an accuracy of 0.5 K and the surface pressure topology coincides with theory and with the data from conventional pressure measurements. Furthermore, a novel kind of an optical dual sensor is introduced, allowing for signal separation due to different luminescence lifetimes without the need of additional spectral separation. This technique expands the possible spectrum of combination of probes applicable to optical dual sensing. The new sensor system consists of a platinum porphyrin and a europium chelate complex, capable of determining oxygen and temperature simultaneously, without the need for different optical filters. A novel general approach for imaging is presented. It makes use of the fundamental setup of digital cameras and enables to monitor the spectrally resolved luminescence of up to three signals with one single image. The new materials and methods developed during this dissertation led to the fabrication of the first optical triple sensor systems. Two kinds of sensors are reported. They are capable of simultaneously determining the three important analytes pH, T, and O2. The first system consisted of HPTS as the pH-indicator, a Eu-chelate complex as the temperature probe, and a Pt-porpholactone as the probe for oxygen, all encapsulated in appropriate polymer particles. The three signals are separated using optical filters. In the second triple sensor system, the O2 probe of the first system was replaced by a Pt-porphyrin, enabling for time-resolved separation of the temperature signal from the O2 signal. With these new kinds of sensors, it is possible to monitor the three clinically relevant parameters pH, T, and O2 non-invasively, online, and in surpassing spatial resolution. By omitting the oxygen probe, the first temperature compensated optical pH sensor ever described in literature is obtained.