基于银-丝蛋白-银结构的柚子型三芯光纤痕量水传感器

Grapefruit-type three-core fiber sensor for trace water based onsilver-silk protein-silver structure

有机溶剂中的水杂质强烈影响化学反应的进程。然而,目前检测痕量水的方法仍存在操作复杂、实验试剂毒性高、检测灵敏度低、无法实时监测等不足。为了克服这些缺点,提出了一种在可见光波长范围内银和丝蛋白结合的D型光纤传感器。该传感器利用金属银和丝蛋白作为主要材料,利用二者出色的传感特性,设计了一种可见光波长的光纤传感器,用于高灵敏度有机化合物中的痕量水检测。研究结果总结如下:首先,提出了在可见光波长范围内银和丝蛋白结合的三明治结构,银被用作外部夹层来诱导表面等离子体共振效应。通过理论分析,观察到所提出的D型光纤传感器表面的双层银结构与单层银结构相比,可以诱导强光局部化。在接下来的尺寸选择过程中,对丝蛋白初始厚度、空气孔大小、银光栅的高度、数量、间距和下层银厚度进行了优化,得到了最佳传感结构,对有机物中痕量水的检测灵敏度高达1.39 nm/ppt (1 ppt=10-12),与同类型的痕量水传感器相比具有较大的优势。另外,拟合线的R^(2)大于0.999,达到了预期的效果。

Objective Water impurity in organic solvent strongly affects the process of chemical reaction.However,current methods for detecting trace water still suffer from disadvantages such as complex operation,high toxicity of experimental reagents,low detection sensitivity,and the inability to monitor in real-time.In order to overcome these challenges,a D-type fiber sensor which combines silver and silk protein in the visible wavelength range is designed.It is designed for high-sensitivity detection of trace water in organic compounds,and the performance of the sensor is optimized and analyzed.Methods First of all,the circular air hole in the middle of the fiber is replaced by the grapefruit type,which increases its size by about ten times(Fig.1),which can reduce the difficulty of the sensor in the actual production process with high efficiency.In addition,the lower metal silver film on the side profile of D-type fiber can form an energy channel with the nearby large air hole of grapefruit type,which promotes the energy leakage of the fiber core into the plasma and enhance the SPR effect.Secondly,a certain number of silver grating structures are added to the lower part of the top silver film,which can make the incident bright part confined to the slit cavity.Through reasonable structural design and size optimization,the local surface plasmon resonance(SPR)wave and surface plasmon wave can further resonate,thus realizing the enhancement of SPR phenomenon.Results and Discussions Theoretical analysis shows that compared to a single-layer silver structure,the double-layer silver structure on the surface of the D-type fiber sensor can induce strong localized light.In the subsequent size selection process,the initial thickness of the silk protein and the height of the air hole(Tab.1),the height of the silver gratings(Tab.2),the amount of the silver gratings(Tab.3),the spacing of the silver gratings(Tab.4)and the thicknesses of the underlayer silver film(Tab.5)are optimized to obtain the optimal sensing structure. Through the above optimization, the optimal structural parameters of the sensor are as follows: theheight of the fiber air hole is 4.5 μm, the height of the silver grating is 10 nm, the number of the silver grating is58, the spacing of the silver grating is 50 nm, and the thickness of the underlying silver film is 31 nm. Comparedwith other structures or methods of trace water detection equipment in sensitivity or detection limit performance,the results show that the detection performance of the grapefruit-type three-core fiber sensor for trace water basedon silver-silk protein-silver structure is much better than the previous design.Conclusions Based on metal insulator metal structure and SPR principle, D-type fiber sensor is designed todetect trace water in organic matter. The sensing materials mainly use silver metal and silk protein, and thesandwich structure composed of silver metal can significantly enhance the local electric field, thus improving thesensitivity of the sensor. Silk protein has good optical properties and can quickly and accurately make reversiblevolume changes in response to external stimuli. Therefore, water absorption of silk protein can be calculated by itsexpanded volume combined with Darcy's law, and the water content in organic matter can be further obtained.The high sensitivity measurement of trace water in organic matter is realized, and the sensitivity can reach1.39 nm/ppt (1 ppt=10−12). Moreover, the fitted line has an R2 value greater than 0.999, achieving the expectedperformance. And the sensor is designed to have a long service life, and is not affected by temperature.