基于水溶性CdTe纳米晶功能荧光探针的设计、合成及分析应用

【作者】 薛梅；

【导师】 唐波；

【作者基本信息】 山东师范大学 ， 物理化学， 2012， 博士

【摘要】 半导体纳米晶也称为量子点，是过去十年中出现的一种新的荧光材料。与传统的有机染料相比，具有优良的光学性质。比如激发光谱宽、发射光谱窄且对称、发射波长可通过控制它的大小和组成来调节、不易光解、同一个激发光可以获得波长不同的发射光等优点。因此，半导体纳米材料的合成及分析应用研究受到了人们的广泛关注。最早人们是用有机溶剂、高温来合成量子点的。这样得到的量子点只能溶于有机溶剂中，这就限制了它们在分析检测中的实际应用。近年来，水溶性量子点在生物和化学领域中有了越来越多地应用，合成高品质的水溶性量子点，实现它们在化学、生物研究中的实际应用成为人们研究的前沿与热点。论文第一部分，我们用“一步”法合成了β-环糊精修饰的CdTe量子点。我们用Cd（Ac）₂、NaHTe、油酸和β-环糊精作为前驱体，在油水两相体系中一步合成。与有机溶剂高温合成量子点相比，这个新方法简单、高效、成本低、合成温度低，而且只需要一步就可以合成；和水相用巯基配体合成量子点相比，这个新方法也很简便，而且不需要合成复杂的巯基配体。此外，这种新配体修饰的纳米晶溶胶在常温下非常稳定。我们所发展的合成方法也为合成其它配体修饰的半导体纳米材料提供了新途径。论文第二部分，我们选择谷胱甘肽（GSH）做为配体水相合成了高品质的CdTe量子点。并没有经过光照等预处理，谷胱甘肽修饰的量子点达到了42%的量子产率。这种量子点具有宽范围的光致发光光谱，可以在510～670nm之间荧光光谱可调，而且产品具有很好的光学稳定性。细胞生存实验表明这种量子点有很好的生物相容性。此外，我们将叶酸连接在量子点表面并进行了癌细胞成像。证明了GSH/CdTe量子点是一个有潜在应用价值的荧光纳米材料。论文第三部分，我们研究了水溶液中巯基乙酸修饰的CdTe量子点和柠檬酸修饰的Au纳米粒子之间的相互作用。由于两者之间形成的氢键，它们互相吸引，产生了有效地荧光共振能量转移，导致量子点的荧光被淬灭。而F-离子，一个具有强烈亲核能力的阴离子，与连接CdTe和纳米金的桥氢反应，致使纳米金远离1量子点，量子点的荧光恢复。这样，我们在水相中，构建了一个新的、依靠调节氢键强度组装的荧光共振能量转移探针。论文最后一部分，我们用氨基二醇修饰CdTe量子点，用巯基苯硼酸修饰纳米金，构建了QDs-diol-MPBA-AuNPs纳米探针。由于苯基硼酸和二醇之间可以形成可逆的硼酸酯键，使得纳米金有效地靠近量子点，共振能量转移发生，量子点的荧光被淬灭。同时，F^-离子﹑作为硬碱，与硬酸硼原子有效地配位，使中心原子硼的杂化态和复合体的构型都发生了变化，又使纳米金远离了量子点，共振能量转移被打断，量子点的荧光恢复。其它阴离子对探针的检测没有干扰。此外这个探针具有较好的生物相容性，并成功地用于活细胞中氟离子的检测。更多还原

【Abstract】 Semiconductor nanocrystals, or quantum dots (QDs), have emerged as an importantnew class of materials over the past decade. Compared with organic fluorophores,QDs possess many advantages, such as size-tunable fluorescence emission, largeabsorption across a wide spectral range, narrow emission spectra, high brightness,long-term photostability and single-light source excitation for multi-colored QDs.Traditionally, these QDs are synthesized in organic solvents using organometallicprecursors at high temperature. In recent years, water-soluble QDs have gainedincreasing attention because QDs have to be water-soluble for biological and mostlychemical applications. So it is necessary to synthesis high quality water soluble QDs.Here, the direct synthesisβ-cyclodextrin (CD) coated water-soluble CdTe QDs byusing a new‘one pot’method is reported. At the artificially designed water-oilinterface using Cd(Ac)2, NaHTe, oleic acid andβ-cyclodextrin as precursors, theobtained CdTe QDs were stabilized byβ-CD, which is different from many previousreports. Compared to the organometallic route to obtain water-soluble QDs, the newstrategy is simple, cost-effective, and only need‘one step’. Compared to the aqueoussynthesis route to obtain water-soluble QDs with thiols as stabilizers, our method isalso simple and requires no necessary to synthesize complicated thiols ligands. Thenew synthetic pathway which is easily handled can probably be expanded tosynthesize other receptor modified QDs.In this paper, different sizes of glutathione-capped CdTe (GSH/CdTe) QDs havebeen prepared derectly in aqueous solution. The biocompatible QDs have tunablefluorescence in the range of 510～670nm, and they also have high photoluminescencequantum yield (PLQY) without any post preparative treatment. In addition, folic acidwas covalently conjugated to the GSH/CdTe QDs for imaging of cancer cells,demonstrating their potentially broad application as biolabels.In a simple mixture solution of thioglycolic acid modified CdTe QDs and citrate-capped gold nanoparticles (AuNPs), fluorescence resonance energy transfer(FRET) was observed and studied. The steady state photoluminescence of CdTe QDsis quenched in the presence of AuNPs. The results suggest that it was hydrogen bondthat connected CdTe QDs and AuNPs together. More interestingly, the formed FRETcan be specificly broken by fluoride anion (F-) due to its unique and strongnucleophilic character. The results present here construct the hydrogen bond basednano-assemblies for the direct determination of F-in aqueous solution, which is highlysimple and practical.Since the affinity of boronic acid for diol is well known, a new FRET nanoprobe ofQDs-diol-MPBA-AuNPs was reported in aqueous solution. 3-amino-1,2-propanediol(diol) is selected to bind carboxyl on the surface of CdTe QDs.Mercaptophenyl-boronic acid(MPBA) is selected to modify AuNPs. The highextinction coefficient of AuNPs and the active boronate esters formed betweenphenylborinic acid and diol facilitate the efficient FRET. Meanwhile, F-anion, astrongly hard lewis base, specificly reacts with boron center and disassembles theAuNPs segment, resulting in the fluorescence recovery of the quenched QDs. Thenew nanoprobe responds well to aqueous F-with high selectivity and sensitivity in thepresence of a higher amount of other anions. In addition, the nanoprobe is low toxicityand effective for the highly selective detection of F~-in live cell.更多还原