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全氟烷基化合物(PFASs)是指化合物分子中与碳原子链接的氢原子全部被氟原子所取代的一类新型有机化合物. PFASs分子中的C—F键十分稳定,因此在天然环境中往往具有较高的稳定性和持久性[1 − 2]. 全氟辛烷磺酸(PFOS)是一种典型的PFASs,在过去的几十年中,曾广泛应用于商业产品和工业过程中[2 − 3]. 由于PFOS的大量使用,已在全球不同地区的人类、鱼类、鸟类和哺乳动物中检测到其存在[4 − 6]. 研究表明,PFOS具有生物累积性,并且具有神经毒性、生殖发育毒性和内分泌干扰性等,对人体和其他生物造成了严重危害[7 − 11]. 2009年《关于持久性有机污染物的斯德哥尔摩公约》第四次缔约方大会将PFOS及其盐类作为限制性化学品列入公约附件B[12]. 我国作为公约缔约方,也已于2014年禁止PFOS及其盐类除特定豁免和可接受用途外的生产、流通、使用和进出口. 可见,PFOS的调查和监控是一项全球性的重要环境课题,发展PFOS的快速筛查方法十分必要.
水体是PFOS在环境中重要的汇. 以我国为例,我国辽河流域、长江三角洲地区和珠江三角洲等地区均不同程度地受到了PFOS污染[13 − 16]. 目前水体PFOS的检测主要依赖于液相色谱-质谱技术[17],存在样品前处理复杂,设备价格高昂,操作繁琐、耗时等局限性,限制了其广泛应用. 荧光传感技术是一种灵敏度高、操作简便、可实时检测的化学物质分析技术,近年来已被成功用于快速筛查PFOS、全氟辛烷羧酸(PFOA)等多种PFASs[18 − 29],显示了优异的应用潜能. 目前可用于检测PFOS的荧光传感器以染料和碳量子点为主[18 − 23,27 − 29],不但种类有限、传感方式单一(以荧光猝灭为主),还存在PFOS响应时间长、检出限高等问题.
发光金属-有机骨架材料(LMOFs)是一类新型发光材料,具有理化性质稳定、比表面积高、结构多样可调等特点,近年来引起了荧光传感领域的广泛关注,在诸如挥发性有机化合物、生物分子、爆炸物、重金属等化学物质的传感中显示了出色的灵敏度、速度和选择性[30 − 31]. 本论文制备了锆基LMOFs(UiO-66-NH2),研究了其对PFOS的荧光传感性能,建立了水体PFOS的快速筛查方法,并在实际水体中验证了方法的可应用性.
基于锆基荧光金属-有机骨架材料的水体全氟辛烷磺酸的快速筛查
Rapid fluorescent sensing of perfluorooctane sulfonate in water using a zirconium-based luminescent metal-organic framework
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摘要: 本文以锆基荧光金属-有机骨架材料UiO-66-NH2为传感器,建立了水体全氟辛烷磺酸(PFOS)的快速荧光筛查方法. 利用扫描电子显微镜、X射线衍射、傅里叶变换红外光谱和荧光光谱等手段对UiO-66-NH2的结构和光学性质进行了分析,并且考察了UiO-66-NH2传感器对PFOS的传感灵敏度、速度和稳定性,及其在实际水体中的可应用性. 研究结果显示,UiO-66-NH2与其配体(2-氨基对苯二甲酸/BDC-NH2)具有相似的荧光性质,均可在光激发下产生稳定的蓝色荧光,但发光强度明显弱于BDC-NH2. 这是因为UiO-66-NH2中锆与BDC-NH2间的配体-金属电荷转移(LMCT)抑制了BDC-NH2的荧光发光. 而PFOS可与UiO-66-NH2锆金属节点发生作用,影响锆与BDC-NH2间的LMCT过程,进而恢复BDC-NH2的荧光,产生荧光“开启”响应. 在0.1—4.0 mg·L−1浓度范围内,PFOS浓度与UiO-66-NH2的荧光增强程度呈现良好线性正相关(R2 = 0.993). UiO-66-NH2对PFOS的检出限为3.46 μg·L−1(即
0.0069 μmol·L−1),低于文献中报道的多数PFOS荧光传感器. UiO-66-NH2还具有较快的PFOS响应速度,在与PFOS作用400 s之内即可达到荧光响应平衡. 此外,UiO-66-NH2对PFOS的传感过程基本不受水体常见阴、阳离子的影响,具有良好的可重复利用性,在实际水体筛查中也显示了高加标回收率(95.0%—106.5%),表明基于UiO-66-NH2的荧光法在水体PFOS的快速筛查中具有良好的应用潜能.-
关键词:
- 全氟辛烷磺酸 /
- 荧光传感 /
- 荧光金属-有机骨架材料 /
- 荧光开启.
Abstract: In this study, a fluorescent method was established for the rapid sensing of perfluorooctane sulfonate (PFOS) in water using a zirconium-based luminescent metal-organic framework, UiO-66-NH2. The structural and optical spectral properties of the UiO-66-NH2 were characterized by combined techniques including scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and fluorescence spectroscopy. The sensing sensitivity, speed and stability of the UiO-66-NH2 sensor for PFOS, and its applicability in real water samples were investigated. The results showed that UiO-66-NH2 exhibited stable blue emission in water under light excitation, mainly originating from the 2-aminoterephthalic acid (BDC-NH2) ligand. The fluorescence emission of BDC-NH2 was weakened upon its integration into the framework of UiO-66-NH2 due to the ligand-to-metal charge transfer (LMCT). The competitive coordination of PFOS with the zirconium node would interrupt the LMCT process and thus recover the emission of BDC-NH2, resulting in a fluorescent “turn-on” response. In the concentration range of 0.1—4.0 mg·L−1, the enhancement of UiO-66-NH2 fluorescence intensity (at excitation wavelength of 330 nm and emission wavelength of 438 nm) showed a good linear positive correlation with the concentration of PFOS (R2 = 0.993). The detection limit of PFOS by the fluorescence method based on UiO-66-NH2 was 3.46 μg·L−1 (i.e.,0.0069 μmol·L−1), lower than that of most reported PFOS fluorescence sensors. Moreover, UiO-66-NH2 afforded a rapid response speed towards PFOS, with a response equilibrium time within 400 s. The sensing performances of UiO-66-NH2 was scarcely affected by common interfering ions in water. The UiO-66-NH2-based sensing method also exhibited good reusability and high PFOS recoveries (95.0%—106.5%) in real water samples, suggesting its good applicability for PFOS screening in waters. -
图 3 (a)PFOS存在下UiO-66-NH2的二维荧光光谱(Ex= 330 nm);(b)BDC-NH2单体的二维荧光光谱(Ex= 330 nm);(c)PFOS浓度与UiO-66-NH2荧光增强的相关关系;(d)UiO-66-NH2对PFOS的荧光响应动力学
Figure 3. Fluorescence spectra at Ex 330 nm of (a) UiO-66-NH2 solution upon the addition of PFOS and (b) BDC-NH2 linker; (c) relationship between fluorescence enhancement of UiO-66-NH2 and PFOS concentration; (d) fluorescence response of UiO-66-NH2 to PFOS as function of interaction time
表 1 文献已报道PFOS荧光传感器的检测性能
Table 1. Analytical performances of reported fluorescence methods for PFOS sensing
探针
Sensor检出限/(μmol·L−1)
LOD线性范围/(μmol·L−1)
Linear Range响应时间/s
Response time文献
References黄色曙红/聚乙烯亚胺 0.0150 0—2.0 600 [18] 赤藓红B/十六烷基三甲基溴化铵 0.0128 0.05—10 600 [19] 赤藓红B/硅氧烷 2.7000 0—40 150 [20] 耐尔蓝A 0.0032 0.05—4.0 1200 [21] 丙烯酰丹/肝型脂肪酸结合蛋白 0.6898 0.1—10 300 [22] 异硫氰酸荧光素/分子印迹材料/SiO2纳米颗粒 0.0111 0.01—0.09 300 [23] Guanidinocalix[5]arenes超分子 0.0214 0—0.70 N.A.a [24] BowtieCyclophane超分子大环 0.0473 0—0.60 30 [25] 苝二酰亚胺衍生物 0.0280 0.1—1.5 600 [26] 碳量子点 0.0183 0—12.0 1200 [27] 碳量子点/盐酸小檗碱 0.0217 0.22—50 600 [28] 氮掺杂碳量子点/溴化乙锭 0.0278 0—2.0 1200 [29] UiO-66-NH2 0.0069 0.1—8.0 400 本论文 注:a “N.A.” 文中未提及. a “N.A.” Not available. 表 2 UiO-66-NH2对实际水样中PFOS的检测结果
Table 2. Analytical results for the determination of PFOS by UiO-66-NH2 in real water samples
加标浓度/(mg·L−1)
Spiked concentration自来水样 九乡河水样 检出浓度/(mg·L−1)
Detected concentration回收率/%
Recovery检出浓度/(mg·L−1)
Detected concentration回收率/%
Recovery1.0 0.98 98.1 1.04 104.3 2.0 1.88 96.0 2.13 106.5 4.0 4.10 102.6 3.82 95.5 -
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