In this article, a hetero-core optical fiber sensor structure is developed for the diagnosis of L-Cysteine content in human urine. The hetero-core structure is created by sequentially cascading the single mode-multimode-single mode fibers using thermal fusion splicing. The multimode section of fiber probe is etched out and coated with synthesized gold nanoparticles (AuNPs), polyvinyl alcohol stabilized silver nanoparticles (PVA-AgNPs) and graphene oxide (GO). The AuNPs and PVA-AgNPs are used to initiate the localized surface plasmon resonance (LSPR) phenomenon on the application of exponentially decaying evanescent waves. The layer of GO is used to provide the larger surface area and binding sites for the L-Cysteine (L-Cys) molecules. Based on the combination of NPs, two different configurations of sensor probes are developed. In first one, a layer of AuNPs is deposited over fiber surface and further followed by the coating of GO, and named Probe I. In the second one, a layer of PVA-AgNPs is sandwiched between the fiber surface and GO layer and termed as Probe II. The characterization of synthesized NPs and GO solutions, and developed sensor probes are done by using UV-Vis spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). To authenticate the biocompatibility of developed sensor probes, the artificial aqueous samples of L-Cys ranges from 0 μM to 1 mM are tested. To determine the stability of L-Cys, a pH level based study is also carried out to ensure the good stability of analyte in aqueous samples. From the results, it was ascertained that the response of Probe II is better in terms of attained limit of detection and sensitivity that is 126.6 μM and 0.0009 nm/μM, respectively.

中文翻译：

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基于局部表面等离子体共振的异芯光纤传感器结构用于检测 L-半胱氨酸

在本文中，开发了一种异芯光纤传感器结构，用于诊断人尿中的 L-半胱氨酸含量。异纤芯结构是通过使用热熔接顺序级联单模-多模-单模光纤来创建的。光纤探针的多模部分被蚀刻并涂上合成的金纳米粒子 (AuNPs)、聚乙烯醇稳定的银纳米粒子 (PVA-AgNPs) 和氧化石墨烯 (GO)。AuNPs 和 PVA-AgNPs 用于在指数衰减渐逝波的应用中引发局部表面等离子体共振 (LSPR) 现象。GO 层用于为 L-半胱氨酸 (L-Cys) 分子提供更大的表面积和结合位点。基于 NP 的组合，开发了两种不同配置的传感器探头。在第一个，一层AuNPs沉积在纤维表面，然后是GO涂层，称为探针I。在第二个中，一层PVA-AgNPs夹在纤维表面和GO层之间，称为探针II。合成 NPs 和 GO 溶液的表征以及开发的传感器探针是通过使用紫外-可见分光光度法、透射电子显微镜 (TEM)、扫描电子显微镜 (SEM) 和原子力显微镜 (AFM) 来完成的。为了验证开发的传感器探针的生物相容性，测试了 L-Cys 的人工水性样品，范围从 0 μM 到 1 mM。为了确定 L-Cys 的稳定性，还进行了基于 pH 水平的研究，以确保水样中分析物的良好稳定性。从结果来看，