Ultrasensitive detection of heavy metal ion concentrations in drinking water is highly relevant for protecting human health and environmental monitoring. In this study, we propose and experimentally validate a long-period fiber grating (LPFG) chemical sensor for detecting nickel (Ni) and zinc (Zn) ions. A sensitive film composed of chitosan (CS) and polyacrylic acid (PAA) was used and assembled on the surface of a phase-shifted long-period fiber grating (PS-LPFG) using a layer-by-layer self-assembly technique. Experimental results show that the sensor exhibits high sensitivity for detecting Ni ions, with a detection sensitivity of 24.6 nm/ppm in the concentration range of 1-500 ppb and 0.4 nm/ppm in the range of 500–10000 ppb. The limit of detection (LOD) obtained from fitting the Langmuir isothermal adsorption model was 2.014 ppb. For Zn ions, the sensor demonstrated a sensitivity of −6.84 nm/ppm in the concentration range of 1–1000 ppb, with a low LOD of 1.38 ppb. The specificity of the PS-LPFG sensor was verified using various heavy metal ions, confirming its high selectivity for Ni and Zn. Furthermore, the sensor's regeneration characteristics were evaluated through three repetitive adsorption–desorption cycle experiments, demonstrating its good stability. The sensor was also successfully applied to the real detection of Ni and Zn in tap water samples, showcasing its potential for practical applications. The proposed sensor offers multifunctional sensing, easy fabrication, fast detection, good repeatability, versatility, and high sensitivity. It holds great potential for practical multi-sensing applications.

中文翻译：

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聚丙烯酸和壳聚糖功能化相移长周期光纤光栅检测水溶液中的镍和锌离子

饮用水中重金属离子浓度的超灵敏检测对于保护人类健康和环境监测具有重要意义。在这项研究中，我们提出并通过实验验证了一种用于检测镍 (Ni) 和锌 (Zn) 离子的长周期光纤光栅 (LPFG) 化学传感器。使用由壳聚糖（CS）和聚丙烯酸（PAA）组成的敏感薄膜，并采用逐层自组装技术将其组装在相移长周期光纤光栅（PS-LPFG）的表面上。实验结果表明，该传感器对Ni离子的检测具有较高的灵敏度，在1-500 ppb浓度范围内检测灵敏度为24.6 nm/ppm，在500-10000 ppb浓度范围内检测灵敏度为0.4 nm/ppm。通过拟合 Langmuir 等温吸附模型获得的检测限 (LOD) 为 2.014 ppb。对于 Zn 离子，该传感器在 1–1000 ppb 浓度范围内表现出 -6.84 nm/ppm 的灵敏度，LOD 低至 1.38 ppb。使用各种重金属离子验证了 PS-LPFG 传感器的特异性，证实了其对 Ni 和 Zn 的高选择性。此外，通过三次重复吸附-解吸循环实验评估了传感器的再生特性，证明了其良好的稳定性。该传感器还成功应用于自来水样品中Ni和Zn的实际检测，展示了其实际应用潜力。所提出的传感器具有多功能传感、易于制造、快速检测、良好的重复性、多功能性和高灵敏度。它在实际的多传感应用中具有巨大的潜力。