【作者】 何瑜；

【导师】 严秀平；

【作者基本信息】 南开大学 ， 分析化学， 2009， 博士

【摘要】 量子点（Quantum Dots,QDs）在传感器领域的应用引起了国内外学者的广泛关注,成为当前科学研究的一大热点。量子点表面化学或物理性质的微小变化将会改变量子点的光学性质。据此,量子点已广泛应用于各种分析物的检测。虽然量子点的荧光性质在分析化学中的应用已经十分广泛,但是量子点的室温磷光（Room-Temperature Phosphorescence,RTP）性质及其在分析检测中的应用得到的关注仍然较少。当量子点和其它分子形成纳米复合材料时,该纳米复合物会呈现出新的光、电或磁特性。量子点的纳米复合材料是获取材料新特性的一种有效手段,对于改善现有量子点的光学性能以及促进量子点传感器的发展具有十分重要的意义。本论文旨在探索掺杂量子点和其纳米复合材料的RTP性质及其在化学/生物传感中的应用,主要研究内容和创新点如下:（1）基于水溶性L-半胱氨酸包覆的Mn掺杂ZnS量子点的RTP性质,发展了一种简单、快速、经济、灵敏和高选择性的检测生物体液中依诺沙星的方法。该方法能有效避免生物体液的自体荧光和散射光的干扰,并且在检测生物体液中的依诺沙星时不需要加入任何除氧剂和诱导剂。同时,避免了生物体液中的金属离子、生物分子和其它抗生素的干扰。实验测定依诺沙星的线性范围为0.2～7.2μM,检出限（3σ）为58.6 nM,对不含依诺沙星和含0.4μM依诺沙星体系的磷光强度差值连续11次平行测定的相对标准偏差为1.8%。在尿样和血清样品中加标依诺沙星的回收率为94%～104%。将基于Mn掺杂ZnS量子点的室温磷光法用于测定依诺沙星在人体中的代谢曲线,得到的结果和通过其它方法研究的依诺沙星代谢曲线的结果基本一致。研究结果表明掺杂量子点的RTP性质将会促进量子点传感器的进一步发展。（2）基于Mn掺杂ZnS量子点和甲基紫（Methyl Viologen,MV）的光诱导电子转移（Photoinduced Electron Transfer,PIET）效应,建立了一种灵敏的定量检测生物体液中DNA的新方法。该方法有效的利用了量子点自身的物理和光学特性,当MV吸附到Mn掺杂ZnS量子点表面时,通过PIET过程,储存了Mn掺杂ZnS量子点的磷光。当DNA加入体系后,DNA和MV结合,MV从Mn掺杂ZnS量子点表面脱附,引起Mn掺杂ZnS量子点的RTP的增强。该方法检测DNA的检出限（3σ）为33.6μg L^-1,线性范围在0.08～12mg L^-1,对不含DNA体系的磷光强度连续11次平行测定的相对标准偏差为3.7%。由于该方法是基于量子点磷光性质的检测,所以有效的消除了来自样品自体荧光和散射光的干扰。同时,这种方法能够灵敏、快速的检测生物体液中的DNA,避免了化学修饰和固定化的过程。（3）利用静电自组装构建了Mn掺杂Zn量子点/八（γ-氨丙基）倍半硅氧烷（Mn掺杂ZnS QDs/OA-POSS）纳米复合材料,并发展了基于此纳米复合材料的定量检测生物体液中DNA的新方法。带八个氨基的OA-POSS作为立方结构的交联剂通过静电作用将MPA包覆的Mn掺杂ZnS量子点聚集起来,所形成的Mn掺杂ZnS QDs/OA-POSS纳米复合物的RTP强度是Mn掺杂ZnS量子点的RTP强度的7.5倍。带负电荷的DNA能够与带负电荷的3-巯基丙酸（MPA）包覆的Mn掺杂ZnS量子点产生竞争作用,形成了更稳定的DNA/OA-POSS复合物,导致OA-POSS和量子点分开,引起Mn掺杂ZnS量子点/OA-POSS纳米复合物的RTP强度随着DNA浓度的增高而下降。据此,我们建立了定量测定DNA的新方法。该方法的检出限（3σ）为54.9nM,其检出限低于其它纳米粒子非特异性定量测定DNA的方法,但高于序列特异性测定DNA的方法。若能将合适的官能团修饰在Mn掺杂ZnS量子点或POSS上,该方法可拓展用于检测其它的分析物。更多还原

【Abstract】 The exploration of systems capable of sensing and recognizing based on quantum dots （QDs） is a topic of considerable interest. Subtle change of the surface property of QDs can result in a dramatic change in their optical properties. This feature of QDs offers many opportunities for detecting various specific analytes. While most research works focus on the development of QDs based fluorescence sensors, much less attentions are paid to the room-temperature phosphorescence （RTP） properties of QDs and their potential for phosphorescence detection. When the nanohybrids formed between quantum dots and other molecules, the nanohybrids offer unique optical, electrical or magnetic properties that are not found in the individual components. The controlled nanohybrids based on QDs are high of interest for their fundamental importance as well as the application of sensors. The purpose of this dissertation is to explore the RTP properties of Mn-doped ZnS QDs and their nanohybrids for bio/chemosensing. The main contents are summarized as follows:（1） The RTP property of Mn-doped ZnS QDs was explored to develop a novel method for facile, rapid, cost-effective, sensitive and selective detection of enoxacin in biological fluids. The Mn-doped ZnS QDs based RTP method did not need the use of deoxidants and other inducers, and allowed detecting enoxacin in biological fluids without interference from autofluorescence and scattering light of matrix. The Mn-doped ZnS QDs offered excellent selectivity for detecting enoxacin in the presence of main relevant metal ions in biological fluids, biomolecules and other kinds of antibiotics. The precision for eleven replicate detections of 0.4μM enoxacin was 1.8% （RSD）. The detection limit （3σ） for enoxacin was 58.6nM. The recovery of spiked enoxacin in human urine and serum samples ranged from 94% to 104%. The developed Mn-doped ZnS QDs based RTP method was employed to monitor the time-dependent concentration of enoxacin in the urine from a healthy volunteer after oral medication of enoxacin. The investigation provides evidences that doped QDs are promising for RTP detection for further applications.（2） A sensing system based on the photoinduced electron transfer （PIET） between Mn-doped ZnS QDs and methyl viologen （MV） was established for quantitative detection of DNA in biological fluids. The RTP intensity of Mn-doped ZnS QDs was quenched by MV adsorbed onto the surface of the QDs due to the photoinduced electron-transfer process. Addition of DNA restored the RTP signal of Mn-doped ZnS QDs due to the competitive binding of DNA with MV from the surface of Mn-doped ZnS QDs. Sensitive detection of DNA with the detection limit （3σ） of 33.6μg L^-1 and a linear detection range of 0.08-12 mg L^-1 was achieved. The precision for eleven replicate detections of 0.5μM hsDNA was 3.7% （RSD）. The interference from autofluorescence and scattering light was avoided due to the phosphorescence nature of the Mn-doped ZnS QDs. The sensitive and rapid detection of DNA as well as the avoidance of modification or immobilization process makes this system suitable and promising for DNA detection.（3） We present a simple method to build nanohybrids from the 3-mercaptopropionic acid-capped Mn-doped ZnS QDs （MPA-capped Mn-doped ZnS QDs） and octa（3-aminopropyl）octasilsequioxane octahydrochloride （OA-POSS） via electrostatic self-assembly and to provide a convenient strategy to develop a novel RTP sensor for detecting DNA in biological fluids. OA-POSS with eight amine groups on each comer acting as cubic linkers organized MPA-capped Mn-doped ZnS QDs into well-defined aggregates, which gave the RTP intensity 7.5 times higher than that of the MPA-capped Mn-doped ZnS QDs. High density of negatively charged phosphate groups of the double helix provided the ability of DNA to compete with negatively charged MPA-capped Mn-doped ZnS QDs and to form rather stable complexes with OA-POSS, leading to the decrease of the RTP of the Mn-doped ZnS QDs/OA-POSS nanohybrids with increase of the concentration of DNA. The precision for eleven replicate detections of 0.5μM hsDNA was 4.8% （RSD）. The detection limit （3σ） of the present sensor for DNA was 54.9 nM, comparable to or lower than those of some nanocrystal based non-sequence specific methods for quantitative determination of DNA, but much higher than those of some sequence-specific methods. This methodology can be in principle applied to other biological molecules by modifying Mn-doped ZnS QDs and POSS with suitable functional groups that selectively bind target analytes.更多还原