Development of a Spectral Measurement System for the Determination of the Fluorescence Efficiency of Dissolved Oxygen Membrane

Fluorescence quenching technology is one of the advanced technologies for rapid measurement of oxygen content in sewage, surface water and aquaculture water. Oxygen sensitive membrane is the core of fluorescence quenching detection technology. Oxygen sensitive membrane with high fluorescence emission efficiency owns high sensitivity, strong specificity and high signal-to-noise ratio, which makes the detection results more accurate. High efficiency is not the basis of selecting oxygen sensitive film and the key to the optimization design of dissolved oxygen detection components, detection circuit and detection optical path. There is no standard method for evaluating the quality of oxygen-sensitive membranes in existing dissolved oxygen fluorescence detection devices. Based on the research on the optical path and circuit of existing sensor probes, this paper proposes a method to evaluate the quality of oxygen-sensitive membranes using the fluorescence emission efficiency of the whole wavelength range. In this method, the high-power xenon lamp was selected as the excitation light source, and the monochromatic spectroscopy was performed based on the continuous single-wavelength scanning method. Then of oxygensensitive membranes were determined by scanning the excitation light spectrum and fluorescence spectrum, and the fluorescence emission efficiency calculation method was put forward and established. The method could objectively evaluate the fluorescence emission ability and find the optimum excitation wavelength accurately. In order to verify the feasibility of this method, this article conducted experimental measurement on a number of oxygen-sensitive film samples from home and abroad. The test results showed that : the fluorescence emission efficiency of a single oxygen-sensitive film varied with wavelength and exhibits a multimodal distribution. The fluorescence efficiency curves of the samples of the same type were similar, but there were significant differences in the fluorescence emission efficiency. The fluorescence emission efficiency of the samples with the largest excitation wavelength was 14. 5% higher than that of the ones with the smallest excitation wavelength. The wavelength of the highest peak of the given three films were located differently, respectively lying at 401, 543 and 435 nm, meanwhile, all emission peaks were at 650 nm. it is great different of magnitude from 10 to 100 times of the maximum fluorescence emission efficiency for every oxygen sensor membrane. In practice, the observed fluorescence efficiency is only half of the highest, because the exit light wavelength used is not the best one with highest fluorescence, which indicates that it is necessary to optimize the wavelength selection of exit light in order to obtain the highest efficiency. In conclusion, this paper established a dissolved oxygen-sensitive membrane fluorescence emission efficiency detection system, proposed a method to effectively evaluate the quality of oxygen-sensitive membranes based on fluorescence emission efficiency, and carried out the experimental determination of oxygen-sensitive membrane samples. The work in this paper is expected to be used in the research of new oxygen-sensitive membrane materials and processes and the optimal design and manufacture of sensors.