Lifetime enhancement of ultrasmall fluorescent liquid polymeric film based optodes by diffusion-induced self-recovery after photobleaching

The major concern with optodes, especially miniaturized ones, has been their photobleaching limited lifetime, Liquid polymer [highly plasticized poly(vinyl chloride)] films are commonly used to prepare fluorescent optical fiber sensors. A major advantage is the ease of their fabrication. It is demonstrated here that, with proper choice of excitation power and illumination time, the sensor will completely recover itself from photobleaching after each measurement. This self-recovery is demonstrated on single-mode optical fibers with 80 mu m diameter (3.1 mu m active region) and on near-field scanning optical microscope pulled fiber tips with submicrometer diameter (250 mn active region). The single-mode optode can be used for 30 000 measurements with only a 5% signal loss at a signal/noise of >66. This opens the way for prolonged ratiometric application of such optodes.