硫杂杯[4]芳烃基胶束自组装荧光探针的结构性质及检测性能的研究
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摘要
水体中重金属污染因威胁生态环境和人类健康而被受广泛关注。荧光探针由于具有快速高效检测重金属的特性,一直是该领域的研究热点。通常,荧光探针在结构上包括对待测物质起识别作用的受体和能产生信号响应的荧光体,并逐步形成了内在型、共轭型、系综型和模板辅助自组装型等四种结构类型。近年来,基于受体和荧光体在表面活性剂胶束内自组装而形成的胶束自组装型荧光探针因结构简单、易于制备、能直接应用于水环境等特点逐渐受到重视。以对铜离子具有优异结合性能的对叔丁基硫杂杯[4]芳烃(TCA)为受体,以芘、荧蒽、蒽、菲、苝等分子为荧光体,通过表面活性剂胶束自组装制备针对Cu~(2+)检测的胶束自组装型荧光探针,采用参比法测定了胶束自组装荧光探针的荧光量子产率,采用稳态荧光法测定了胶束聚集数,同时通过计算荧光猝灭率分别考察了荧光体种类、复配表面活性剂等因素对该探针的Cu~(2+)检测性能的影响情况。实验结果显示,采用十二烷基硫酸钠(SDS)、曲拉通100(TX-100)、聚氧乙烯月桂醚(Brij35)等三种不同的表面活性剂对探针荧光体的荧光量子产率产生了明显影响,测得的荧光探针荧光量子产率介于0.25～0.47,且三者逐渐增大,说明表面活性剂改变了胶束内荧光分子芘所处微环境的极性,且不同类型表面活性剂对微环境极性的影响程度有所差异,微环境极性的增强对极性更大的激发态芘具有更强的稳定作用。而受体TCA的加入对荧光体所处微环境极性影响较小,未对荧光量子产率产生较大影响。但TCA的加入使探针的胶束聚集数明显减少,这归因于具有两亲性的受体TCA分子通过胶束自组装进入并分散在表面活性剂分子层中,形成共胶束结构,从而改变了表面活性剂分子的聚集状态。荧光体变更对荧光探针的Cu~(2+)检测性能有显著影响,在同样条件下,以荧蒽、蒽、菲作为荧光体的探针检测Cu~(2+)所得到的荧光猝灭率远高于芘、苝,这主要是因为不同荧光体在从激发态返回基态时辐射跃迁所释放能量不同,其能量与受体TCA识别Cu~(2+)所需能量之间的匹配度越高,荧光猝灭率越大。不同类型的表面活性剂之间的复配能明显提升荧光探针检测性能,当非离子/阴离子、非离子/阳离子型复配表面活性剂之间的复配比例分别为7∶3和1∶1时荧光猝灭率达到最大值,且均高于单一表面活性剂时的荧光猝灭率。这说明不同类型表面活性剂复配的最佳比例存在较大差异,但均有效地增强了受体与荧光体的分散性及自组装性能,提高了对Cu~(2+)的检测性能。研究结果将为新型胶束自组装荧光探针的设计和应用提供数据参考。
Heavy metal pollution in water is widely concerned because it threatens the ecological environment and human health. The fluorescent probe has been a research focus in this field due to the rapid and efficient detection for heavy metals. Generally, the fluorescent probe structurally includes a receptor recognizing a desired analyte and a fluorophore generating a signal response. It gradually has formed four kinds of structures, which are intrinsic, conjugate, ensembling and template-assisted self-assembled types. In recent years, micellar self-assembled fluorescent probes based on the self-assembly of acceptor and fluorophore in surfactant micelles have attracted attentions. This is due to their simple structure, easy preparation and direct application to water environment. In this paper, the micellar self-assembled fluorescent probes for the detection of Cu~(2+) ions were prepared through self-assembly of surfactant micelles. The p-tert-butylthiacalix[4]arene(TCA) was used as acceptor with excellent bonding property to copper ions. And pyrene, fluoranthene, anthracene, phenanthrene, perylene were used as fluorophore. The fluorescence quantum yields of the micellar self-assembled fluorescent probes were measured by the reference method. The micelle aggregation numbers were determined by the steady-state fluorescence method. At the same time, the influences of fluorophore species and compound surfactants were investigated on detection performances of the probes for Cu~(2+) ions by calculating the fluorescence quenching rate. The experimental results showed that the three surfactants, which are sodium dodecyl sulfate(SDS), Triton X-100(TX-100) and polyoxyethylene lauryl ether(Brij35), had significant effects on fluorescence quantum yields of the probes. Their fluorescence quantum yields were in the range of 0.25～0.47. And they gradually increased. These indicated that the polarities of the microenvironment inside the micelles were changed by surfactant micelles. And the influences of different types of surfactants on the microenvironment polarity were different. The enhancement of the microenvironment polarity made excited pyrene more stable. The addition of acceptor TCA had little effect on the polarity of the microenvironment in which the fluorophore was located. And it didn't have a significant influence on the fluorescence quantum yield. However, the micellar aggregation numbers of the probe markedly decreased after the addition of TCA. They were attributed to the fact that the amphiphilic receptor TCA molecules dispersed into the surfactant molecular layer through micelle self-assembly forming co-micelle structure. Thus, the aggregation state of the surfactant molecules was changed. The fluorophore had a significant effect on the detection performance of the probe for Cu~(2+) ions. Under the same conditions, the fluorescence quenching rates of the probes to detect Cu~(2+) ions respectively using fluoranthene, anthracene and phenanthrene as fluorophores were much higher than those of pyrene and perylene. This was mainly due to the different energies released by fluorophore radiative transitions from the excited state to the ground state. And the higher the matching degree with the energy required by the acceptor TCA to recognize Cu~(2+) ions, the greater the fluorescence quenching rate. The compound surfactants could obviously improve the detection performance of the fluorescent probe. When the mole ratios of non-ionic/anionic and non-ionic/cationic surfactants were 7∶3 and 1∶1 respectively, the fluorescence quenching rates were maximum. And the fluorescence quenching rates of the compound surfactants both were higher than those of single surfactant. These showed that the optimal compound ratios of different types of surfactant were quite different. But they both effectively enhanced the dispersibility and self-assembled performance of receptor and fluorophore. Moreover, they improved the detection performance of the probe for Cu~(2+) ions. The results of the thesis will provide a reference for the design and application of novel micellar self-assembled fluorescent probes.
Heavy metal pollution in water is widely concerned because it threatens the ecological environment and human health. The fluorescent probe has been a research focus in this field due to the rapid and efficient detection for heavy metals. Generally, the fluorescent probe structurally includes a receptor recognizing a desired analyte and a fluorophore generating a signal response. It gradually has formed four kinds of structures, which are intrinsic, conjugate, ensembling and template-assisted self-assembled types. In recent years, micellar self-assembled fluorescent probes based on the self-assembly of acceptor and fluorophore in surfactant micelles have attracted attentions. This is due to their simple structure, easy preparation and direct application to water environment. In this paper, the micellar self-assembled fluorescent probes for the detection of Cu~(2+) ions were prepared through self-assembly of surfactant micelles. The p-tert-butylthiacalix[4]arene(TCA) was used as acceptor with excellent bonding property to copper ions. And pyrene, fluoranthene, anthracene, phenanthrene, perylene were used as fluorophore. The fluorescence quantum yields of the micellar self-assembled fluorescent probes were measured by the reference method. The micelle aggregation numbers were determined by the steady-state fluorescence method. At the same time, the influences of fluorophore species and compound surfactants were investigated on detection performances of the probes for Cu~(2+) ions by calculating the fluorescence quenching rate. The experimental results showed that the three surfactants, which are sodium dodecyl sulfate(SDS), Triton X-100(TX-100) and polyoxyethylene lauryl ether(Brij35), had significant effects on fluorescence quantum yields of the probes. Their fluorescence quantum yields were in the range of 0.25～0.47. And they gradually increased. These indicated that the polarities of the microenvironment inside the micelles were changed by surfactant micelles. And the influences of different types of surfactants on the microenvironment polarity were different. The enhancement of the microenvironment polarity made excited pyrene more stable. The addition of acceptor TCA had little effect on the polarity of the microenvironment in which the fluorophore was located. And it didn't have a significant influence on the fluorescence quantum yield. However, the micellar aggregation numbers of the probe markedly decreased after the addition of TCA. They were attributed to the fact that the amphiphilic receptor TCA molecules dispersed into the surfactant molecular layer through micelle self-assembly forming co-micelle structure. Thus, the aggregation state of the surfactant molecules was changed. The fluorophore had a significant effect on the detection performance of the probe for Cu~(2+) ions. Under the same conditions, the fluorescence quenching rates of the probes to detect Cu~(2+) ions respectively using fluoranthene, anthracene and phenanthrene as fluorophores were much higher than those of pyrene and perylene. This was mainly due to the different energies released by fluorophore radiative transitions from the excited state to the ground state. And the higher the matching degree with the energy required by the acceptor TCA to recognize Cu~(2+) ions, the greater the fluorescence quenching rate. The compound surfactants could obviously improve the detection performance of the fluorescent probe. When the mole ratios of non-ionic/anionic and non-ionic/cationic surfactants were 7∶3 and 1∶1 respectively, the fluorescence quenching rates were maximum. And the fluorescence quenching rates of the compound surfactants both were higher than those of single surfactant. These showed that the optimal compound ratios of different types of surfactant were quite different. But they both effectively enhanced the dispersibility and self-assembled performance of receptor and fluorophore. Moreover, they improved the detection performance of the probe for Cu~(2+) ions. The results of the thesis will provide a reference for the design and application of novel micellar self-assembled fluorescent probes.
引文
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[2] Wu Weina, Mao Pandong, Wang Yuan, et al. Sensors and Actuators B, 2018, 258: 393.
[3] Nilanjan D, Santanu B. The Chemical Record, 2016, 16(4): 1934.
[4] HU Xiao-jun, ZHANG Zhi(胡晓钧, 张智). Journal of Shenyang University (沈阳大学学报), 2015, 27(2): 87.
[5] Tiziana D G, Raimondo G, Federico P, et al. Journal of Photochemistry and Photobiology A, 2017, 345: 74.
[6] Jugun P, Chinta B R, Chebrolu P R. Coordination Chemistry Reviews, 2012, 256(23-24): 2762.
[7] Rajesh K, Yeon O L, Vandana B, et al. Chemical Society Reviews, 2014, 43(13): 4824.
[8] Hu Xiaojun, Li Congming, Song Xueying, et al. Inorganic Chemistry Communications, 2011, 14: 1632.
[9] Burilov V A, Mironova D A, Ibragimova R R, et al. Colloids and Surfaces A, 2017, 515: 41.
[10] Shinya T, Takafumi U, Satoru N, et al. The Journal of Organic Chemistry, 2015, 80(2): 1070.
[11] Gao Zhihao, Lin Zhengzhong, Chen Xiaomei, et al. Sensors and Actuators B, 2016, 222: 965.
[12] Pablo F G, Pilar B, Alfredo A, et al. Langmuir, 2016, 32(16): 3917.
[13] Yan Hui, Cui Peng, Liu Chengbu, et al. Langmuir, 2012, 28(11): 4931.