溶胶—凝胶法制备基于荧光猝灭原理的光纤氧传感器在线监测水中溶解氧

Sol-gel-derived membrane for fiber optical oxygen sensor based on fluorescence quenching

利用氧分子对金属钌化合物的荧光具有猝灭作用的特性,构造出基于荧光猝灭原理的光纤氧传感器。就用于水中溶解氧在线监测的光纤光谱仪的搭建、传感器探头的设制及传感膜的制作过程进行探索,并对传感器的响应性能进行考察。结果表明以联吡啶钌等作为荧光指示剂以溶胶-凝胶法制备的传感膜对溶解氧的响应具有良好的可逆性,稳定性,较快的响应时间和较长的使用寿命。与标准法相对照,用本仪器系统测定了不同盐度的人工海水中的溶解氧浓度,两种方法在不同浓度水平下的溶解氧测定值均无显著性差异。本法的日内和日间RSD在1.7％～5.0％之间。

Oxygen sensor based on fluorescence quenching by oxygen have been developed and wide applied. The oxygen quenching process is described by the Stern-Volmer equation. Ruthenium complex are chosen as fluorescence indicator because they are particularly attractive for oxygen sensing, exhibit high luminescent quantum yield, long excited-state lifetime, large Stokes shift, and strong absorption in the blue-green spectral region. The sensor involves immobilizing the ruthenium complex within a porous sol-gel-processed membrane. Sol-gel process has many advantages as a method of immobilization. At ambient temperature, it allows the fabrication of a tough, inert, porous glass material with a high surface area. Sol-gel-derived silica membrane has a low optical absorption in the visible and UV region of the spectrum and is relatively inexpensive to produce. ^The optode with photosensitive reagent added Ru(phen)_3Cl_2 as fluorescence indicator immobilized in sol-gel-derived membrane shows a satisfactory linear response for the dissolved oxygen in water (r = 0. 9992, n=6). The relative standard deviations were 1. 7%～5. 0%, the detection limit was 0. 03μg/mL (S/N = 3). The exposure time and recovery time of the fluorescence signal was evaluated by alternate measurements in oxygen-saturated water and nitrogen—purged water. The relative standard deviation (n = 6) was found to be 0.6%. The fluorescence intensity of the membrane in contact with flowing water was recorded over a period of 96h. From fluorescence intensity values taken every 4h (n = 24) a relative standard deviation of 6% was obtained. After 3 months, the fluorescence signal of the membrane had decreased by 16%. The decrease may be due to washing out of fluoroprobe, but this was not an obstacle to its further use; the quantitative information (F_0/F) did not change significantly, where F_0 and F are the fluorescence intensities in the absence and in the presence of oxygen, respectively. The sensor has good reproducibility and long-term stability. The interference was investigated and the selectivity of method in seawater was affirmed by a conventional method.