Ultrasensitive Detection Allows For Singlet Oxygen Phosphorescence Detection, An Important Prerequisite For Photodynamic Therapy

Detection sensitivity from the ultraviolet to the near infrared spectral region is a key parameter to meet todayu0027s demand for handling smallest analyte amounts and short measurement times in the optical evaluation of miscellaneous samples. The introduction of single photon counting based data acquisition has proven to yield a major sensitivity increase and very high dynamic range - it is the ideal method for measuring weak luminescence.We present the hardware and handling optimization of a state of the art spectrometer for steady-state and time-resolved fluorescence measurements. The high sensitivity of the spectrometer was shown by measurements of popular fluorescent dyes as well as the Raman spectrum of water under well defined and reproducible conditions. The achieved sensitivity allows us to quantify singlet oxygen generation and to characterize the singlet oxygen phosphorescence decay, a prerequisite when studying photosensitisers like porphyrins and phthalocyanines used for example in photodynamic therapy (PDT). Moreover, with the help of an integrating sphere fluorescence quantum yields of low fluorescent samples like Ru(bpy)3 in water can be determined very precisely.The fibre connection of the spectrometer to a time-resolved fluorescence microscope (MicroTime100/200) was also realized. The combination of the advantages of both setups makes it e.g. possible to perform 2D-lifetime imaging with a freely tunable detection window for low luminescent samples even far into the near infrared region. The measurements with such a combination give not only the spectral and lifetime information of a luminescent sample but also the spatial information which is especially important for hetergeneous samples.