摘要
铅离子(Pb2+)是日常生活中常接触的有毒重金属污染物之一.本研究开发了一种新型反射式光纤干涉传感器,用于检测痕量铅离子.该传感器结构由单模光纤、无芯光纤和细芯光纤(TCF)依次拼接而成.TCF的包层被氢氟酸部分腐蚀并涂覆功能化的水凝胶传感膜.该传感膜选用甲基丙烯酸2-羟基乙酯(2-HEMA)作为识别单体.2-HEMA中的氧原子能与Pb2+发生配体-受体相互作用,形成"-O-Pb-O-"交联结构,从而改变TCF的新包层有效折射率.因此,可以通过观察反射光谱中光信号的变化来检测水溶液中Pb2+的浓度.所提出的传感器具有很高的检测灵敏度(1.926×109 nm∙mol-1∙L),其检测极限为4.14 ppt(1 ng∙L-1 = 1 ppt),比世界卫生组织(WHO)规定的饮用水中Pb2+(10 ppb,1 µg∙L-1 = 1 ppb)浓度低1000倍.此外,利用一个方程组实现了该传感器的温度自校准功能,成功地消除了环境温度的干扰.由于该传感器良好的特异性、稳定性以及反射式结构,非常便于实时远程检测,为环境和人类健康监测提供了广阔的前景.
Abstract
Lead ions(Pb2+)are among the most prevalent toxic heavy-metal pollutants in daily human life,particularly in children and pregnant women.Although atomic absorption spectroscopy is the most commonly used method owing to its accuracy and reliability,it requires complex sample preparation and expensive equipment.Therefore,efficient detection of Pb2+ is currently the focus of optical sensing research.In this study,we develop a reflective fiber-optic interferometric sensor to detect trace levels of lead ions.The sensor is composed of a single-mode fiber,no-core fiber(NCF),and thin-core fiber(TCF).When light from the broadband light source is transmitted to the sensor via ports 1 and 2 of the fiber optic circulator,the light diverges and propagates forward in the NCF.Owing to the fiber-core mismatch of different optical fibers,the beams can excite the core and cladding modes in the TCF.When the beams are reflected back into the NCF,the core and cladding modes can effectively interfere in the NCF due to their optical path differences.Subsequently,the light signal is recorded by an optical spectrum analyzer through port 3 of the circulator.The TCF's cladding is partially etched and coated with a functionalized hydrogel-sensing film made of 2-hydroxyethyl methacrylate(2-HEMA)as the recognition monomer.The oxygen atoms in the 2-HEMA are specifically matched with Pb2+ to form"-O-Pb-O-"cross-linked structures.Therefore,the absorption of Pb2+ by the hydrogel can change the effective refractive index of a new cladding of the TCF,formed by the sensing film and the TCF's original cladding,thereby the Pb2+ concentration is detected by the change of the optical signal.Owing to the trace levels of the detected Pb2+ in aqueous solutions(in the ppt range),we employ an equation system to eliminate temperature interference and ensure accurate detection results under environmental temperature fluctuations.Additionally,for the same sensing length,the concentration sensitivity of fiber-optic sensors with reflective structures is twice that of the transmission structures,and the reflective structure is convenient for real-time remote detection.The experimental results show that the optimal sensitivity of the sensor is 1.926×109 nm∙mol-1∙L,and its detection limit can reach 2.0×10-11 mol∙L-1(4.14 ppt,1 ng∙L-1 = 1 ppt),which is far lower than the standard(10 ppb,1 µg∙L-1 = 1 ppb)set by the World Health Organization.Moreover,the sensor exhibits good stability,specificity,and a wide detection range.Consequently,the designed reflective fiber optic sensor can provide broad prospects for environmental and human health monitoring.
基金项目
深圳-香港-澳门科技计划(C类)(SGDX2020110309520303)
国家重点研发计划(2021YFB2900900)
国家自然科学基金(62105379)
国家科技期刊平台
NSTL
万方数据