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苦味酸(picric acid, PA),学名2, 4, 6-三硝基苯酚(2, 4, 6-trinitrophenol, TNP),因具有很强的酸性和强烈的苦味而得名, 俗称黄色炸药. 苦味酸稳定性不如2, 4, 6-三硝基甲苯(2, 4, 6-trinitrotoluene, TNT),其应用不及TNT广泛,但其爆炸效能强于TNT[1 − 2]. 作为一种重要的化工原料和有机合成中间体,苦味酸被广泛应用于医药、军事、染料、农药和皮革等工业,主要用作合成炸药、农药、染料、杀菌剂、收敛剂、火箭燃料和药物前体等[3 − 4]. 苦味酸具有很强的刺激性,可经过呼吸道、消化道,甚至皮肤被人体吸收,对呼吸系统、消化系统、皮肤系统和视觉系统产生较大危害[5 − 6]. 人体长期接触可引起发热、头痛、头晕、食欲减退、恶心、呕吐和腹泻等症状,甚至可导致末梢神经炎,肝脏损伤、出血性肾炎等,严重危害人类健康,现被认为是一种可能的致癌物[7 − 8]. 由于苦味酸不易被生物降解和良好的水溶性,导致苦味酸在环境中急剧增长,对环境特别是土壤和地下水造成严重的污染[9 − 10]. 因此,发展一种新方法对环境中苦味酸的分析检测具有十分重要的意义.
碳量子点(carbon nanodots, C-dots),简称碳点,是一种尺寸低于10 nm的新型碳基零维纳米材料,首次报道是在电弧放电制备碳纳米管的烟灰中意外发现[11]. 从那以后,科研工作者们努力尝试了各种合成高效碳量子点的方法. 目前,合成碳量子点的方法主要分为两类:自上而下和自下而上的合成方法[12 − 13]. 自上而下的合成方法,包括电弧放电[14]、激光烧蚀[15]和电化学氧化[16]法等,适合将碳基块状材料分解成纳米级碳. 自下而上的合成方法,包括微波辅助[17]、高温热解[18]和水热法[19]等,通常适合于小分子前驱体. 其中,水热法已被证明是一种简单、廉价且可靠的获得碳量子点的方法. 与半导体量子点相比,碳量子点被认为是一种具有生物相容性和无毒的荧光纳米材料[20 − 21]. 噻唑蓝(MTT)法测定细胞活性表明,碳量子点对细胞没有显著毒性,而CdSe半导体量子点导致细胞生存能力减少76%[22]. 除了具有相似的荧光性能外,碳量子点在水溶性、生物相容性、低毒性和化学惰性方面具有许多优越的性能[23]. 因此,设计制备一种高性能荧光碳量子点具有十分重要的意义.
苦味酸是我国《地表水环境质量标准》(GB
3838 —2002)中常规监测指标,为集中式生活饮用水源地特定检测项目,其标准限值为0.5 mg·L−1. 目前的国标方法采用衍生化-气相色谱法检测水体中的苦味酸,现已报道苦味酸的检测方法主要有拉曼光谱法[24]、X射线衍射法[25]、分光光度法[26]、液相色谱法[27]、气相色谱法[28]色谱-质谱法[29]和电化学法[30]等,但这些测定方法由于存在仪器设备昂贵、前期处理复杂、检测周期长、可移植性差和成本较高等问题,不利于现场快速检测. 近年来,基于荧光和比色法的碳量子点荧光探针因其特殊的光学性能而受到许多研究人员的关注,它为医学诊断、食品检测、环境监测和生化测定等领域提供了一种简单、快速和可见的分析方法[31 − 32]. 本研究以中药材川木香原药为前驱体,通过简便的水热反应一步合成荧光碳量子点,根据荧光共振能量转移(FRET),碳量子点的荧光可被苦味酸猝灭,而其它结构类似有机物无此现象,据此构建了苦味酸荧光探针,发展了一种高选择性和高灵敏度检测苦味酸的新方法,原理示意图如图1所示.
基于碳量子点共振能量转移荧光猝灭法检测苦味酸
Detection of picric acid by fluorescence resonance energy transfer quenching method on carbon nanodots
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摘要: 苦味酸(PA)作为一种高爆物和环境污染物,近年来引起了广泛的关注. 本研究提出了一种新型荧光碳量子点(C-dots)探针,可用于快速、高选择性和高灵敏度的PA检测. 探针采用中药材川木香为碳源,通过水热法一步合成. 在荧光碳量子点溶液中加入PA,通过荧光共振能量转移机理,碳量子点的荧光被有效猝灭. 结果表明,碳量子点最大激发波长为360 nm,最大荧光发射波长为415 nm,荧光量子产率为28.4%. 方法检测PA响应时间2 min,线性范围0.2—800 μmol·L−1,检测限(LOD)63 nmol·L−1,实际水样中加标回收实验,回收率为98.8%—101.7%,相对标准偏差(RSD)为1.2%—2.7%.
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关键词:
- 中药材川木香 /
- 荧光共振能量转移(FRET) /
- 碳量子点(C-dots) /
- 苦味酸(PA).
Abstract: Picric acid (PA), as a kind of high explosive and environmental pollutant, has attracted wide attention in recent years. This study presents a novel fluorescent carbon nanodots (C-dots) probe that can be used for rapid, high selectivity and high sensitivity PA detection. The probe is synthesized by hydrothermal method in one step with the carbon source of the traditional Chinese medicinal material Radix Vladimiriae. When PA is added to the fluorescent C-dots solution, the fluorescence of C-dots is effectively quenched by the fluorescence resonance energy transfer (FRET) mechanism. The experimental results show that the maximum excitation wavelength of C-dots is 360 nm, the maximum fluorescence emission wavelength is 415 nm, and the fluorescence quantum yield is 28.4%. This method detects the response time of PA is 2 min, the linear range is 0.2—800 μmol·L−1, the detection limit (LOD) is 63 nmol·L−1, the spike-and-recovery experiments in actual water samples, the recovery rate is 98.8%—101.7%, and the relative standard deviation (RSD) is 1.2%—2.7%. -
图 2 (A)碳量子点TEM图;(B)碳量子点粒径分布直方图;(C) 碳量子点XPS图;(D)碳量子点XPS高分辨C1s谱;(E)碳量子点发射光谱;(F)PA吸收光谱和碳量子点荧光光谱及吸收光谱
Figure 2. (A) TEM image of C-dots; (B)Histogram of the particle size distribution of C-dots; (C) XPS image of C-dots; (D)The XPS high-resolved C1s spectra of C-dots; (E) Emission spectra of C-dots; (F) Absorption spectra of C-dots and TNP and fluorescence spectra of C-dots
表 1 不同浓度干扰实验
Table 1. Interference experiments at different concentrations
干扰物
Interferent浓度/(μmol·L−1 )
Concentration猝灭率/%
(I0-I)/I0相对标准偏差/%
RSD干扰物
Interferent浓度/(μmol·L−1 )
Concentration猝灭率/%
(I0-I)/I0相对标准偏差/%
RSDF− 400 63.6 0.8 Phenol 1000 62.8 1.8 Br− 400 63.0 1.6 2-NP 1000 62.5 0.9 I− 400 62.7 2.4 4-NP 2000 62.9 2.2 Ag+ 400 61.1 1.4 2,4-DNP 2000 62.3 1.2 Cu2+ 1000 62.4 0.7 2,6-DNP 2000 62.3 2.6 Pb2+ 1000 62.5 2.5 TNB 2000 62.5 1.6 Cr3+ 1000 63.0 1.2 TNT 2000 62.7 2.0 表 2 实际水样PA检测及加标回收实验
Table 2. Detection of PA in the Real water samples and add standard recovery experiment
样品
Sample检出浓度/(μmol·L−1)
Found添加浓度/(μmol·L−1)
Added加标测定值/(μmol·L−1)
Total found相对标准偏差/%
RSD回收率/%
Recovery1 — 5 5.2, 4.9, 5.1, 4.9, 5.0 2.6 100.4 20 20.3, 20.5, 20.1, 19.8, 19.6 1.8 100.2 50 51.2, 51.5, 49.9, 50.4, 50.9 1.3 101.6 2 0.6 5 5.6, 5.5, 5.4, 5.8, 5.6 2.7 99.6 20 21.0, 21.3, 20.8, 20.3, 20.4 2.0 100.8 50 51.7, 50.1, 50.3, 51.1, 51.4 1.4 100.6 3 1.5 5 6.3, 6.2, 5.9, 6.2, 6.1 2.5 98.8 20 21.3, 21.4, 21.9, 22.3, 21.8 1.9 101.2 50 52.9, 51.5, 52.4, 53.0, 52.0 1.2 101.7 -
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