Fiber Optic pH Sensor Using Optimized Layer-by-Layer Coating Approach
Fiber Optic pH Sensor Using Optimized Layer-by-Layer Coating Approach
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DOI：
10.1109/jsen.2013.2280283
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发表时间：
2014
影响因子：
4.3
通讯作者：
N. Raoufi;F. Surre;M. Rajarajan;T. Sun;K. Grattan
中科院分区：
文献类型：
--
作者：
N. Raoufi;F. Surre;M. Rajarajan;T. Sun;K. Grattan
在本文中，设计和表征的高分辨率的波长依赖pH值的光学传感器的制作使用逐层技术进行。在这种方法中，作为pH指示剂的亮黄（BY）和作为交联剂的聚（烯丙胺盐酸盐）（PAH）已被沉积在未包覆的二氧化硅纤维上。一些关键参数，如双层的数量，BY溶液的浓度，纤维的形状，以及其芯直径已经改变，以优化pH传感器的设计和性能。从一系列的评估结果表明，灵敏度提高，通过降低使用的指示剂溶液的浓度，并通过设计一个U形弯曲配置传感器探头与急剧弯曲的光纤。然而，当进行总体比较时，与使用大半径弯曲相比，直（未弯曲）光纤探头导致更灵敏的探头。此外，使用小芯直径的光纤允许测量宽的pH范围并且具有高灵敏度。此外，使用具有较大芯直径的光纤，在较窄的pH范围内进行测量的性能有所改善。考虑到层数的影响，所进行的工作表明，具有5-6个双层的探针表现出最佳性能。当使用双层时，灵敏度已被证明会降低，并且感测范围向更高的pH值偏移。当监测时，薄膜的pKa值（解离常数）显示出所考虑的任何设计因素的最小变化。总之，使用较大的芯直径、采用较大的曲线半径、较高的双层数目、较高浓度的指示剂溶液以及应用PAH作为外层，都导致较高的pKa值，因此探针灵敏度向碱性区域移动。
In this paper, the design and characterization of a high resolution wavelength dependent pH optical sensor fabricated using the layer-by-layer technique was undertaken. In this approach, brilliant yellow (BY) as a pH indicator and poly (allylamine hydrochloride) (PAH) as a cross-linker have been deposited on an uncladded silica fiber. A number of key parameters such as the number of bilayers, the concentration of the BY solution, the shape of the fiber, as well as its core diameter have been varied with a view to optimizing the design and performance of the pH sensor. The results obtained from a series of evaluations show that the sensitivity was enhanced by reducing the concentration of the indicator solution used and by designing a U-bend configuration sensor probe with a sharply bent fiber. However, when making an overall comparison, the straight (unbent) fiber probe resulted in a more sensitive probe when compared to the use of a high radius bend. Further, using a small core diameter of the fiber allows a wide pH range to be measured and with high sensitivity. In addition, the performance was shown to be improved for measurements over a narrower range of pH, using a fiber with a larger core diameter. Considering the effect of the number of layers, work carried out has shown that probes with 5-6 bilayers presented the best performance. The sensitivity has been shown to diminish when bilayers were used and the sensing range shifts toward higher pH values. When monitored, the value of pKa (the dissociation constant) of the thin film showed the smallest change of any of the design factors considered. In summary, using a larger core diameter, employing a larger curve radius, a higher number of bilayers, a higher concentration of the indicator solution, and applying PAH as an outer layer, all cause a higher pKa value and consequently the probe sensitivity moves toward alkaline region.