Turn-on and selective luminescence sensing of copper ions by a water-soluble Cd10S16 molecular cluster.
Turn-on and selective luminescence sensing of copper ions by a water-soluble Cd10S16 molecular cluster.
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DOI：
10.1002/anie.200601491
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发表时间：
2006-08
影响因子：
--
通讯作者：
K. Konishi;Takayuki Hiratani
中科院分区：
文献类型：
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作者：
K. Konishi;Takayuki Hiratani
痕量铜（I）离子的检测由于其环境和生物医学意义而变得越来越重要。一种方便的检测工具是发光化学传感器，其中主要的挑战是构建在水中表现出高选择性和灵敏度的正响应的传感系统。[1]通过结合有机荧光团和金属结合螯合物已经设计了各种荧光传感器，[2]但是很少有在水溶液中起作用的“开启”传感器的例子被报道。最近，镉硫族化物纳米材料由于其不寻常的光致发光性质而成为一类新型的发光探针。[3]这些材料对于金属离子感测是潜在有用的，因为预期金属离子（包括铜离子）与表面杂原子（S、Se、Te）相互作用以影响材料的光学性质。虽然金属离子对几种纳米团簇和纳米棒的光致发光性能的影响已经研究，只有淬灭效应已被报道的铜离子。[4，5]在本文中，我们证明了水溶性CdS簇分子2对铜离子的独特开启响应，并强调了其选择性和灵敏度。我们在本研究中使用的CdS簇是一种具有通式[Cd 10 S4（SR）12]的定义和中性分子，其具有截短的四面体Cd 10 S16核心和12个连接到硫原子的表面取代基（R）。[6]我们最近报道了由亲脂性基团（R=简单的烷基或芳基，如1）封端的簇在室温下在有机溶剂中在约600 nm处显示表面介导的发射。[7]为了探索这种分子簇在水溶液中的性质，我们附加低聚（乙二醇）（OEG，-（OC 2 H 4）nOCH 3，n% 6）单元的表面苯基基团的苯基封端的前体1的硫醇盐交换反应，得到2。与1相比，经OEG修饰的簇2在水和有机溶剂如乙腈和氯仿中显示出高溶解度。在HEPES缓冲液（100 mm，pH7.0）中，258 ℃，6.7 μm的团簇在350 nm激发下，在600 nm处有一发射带。用[CuI-（CH 3CN）4] PF 6滴定该溶液导致光致发光的显著增强，沿着，发射最大值略微红移至620 nm（图1a）。[8，9]例如，当2与1摩尔当量的CuI离子混合时，620 nm处的强度和积分带面积分别增加了9.1倍和7.4倍。如图1b所示，加入CuI后，620 nm处的发射强度增加，在[CuI] 0/[2] 0% 2.0处达到平台，I/I0% 12.5。[10]在[CuI] 0/[2] 0= 1.0时观察到的接近线性的相关性允许在纳摩尔至微摩尔浓度下容易地检测CuI。在此条件下，动态范围可达10 μm，检出限约为0.07 μm（% 4ppb）。发现观察到的这种尖锐的阳性反应对CuI具有高度特异性。如图2a所示，
The detection of trace amounts of copper (I) ion is of increasing importance in light of its environmental and biomedical implications. One convenient detection tool is the luminescent chemosensor, whereby the major challenge is to construct sensing systems that exhibit positive responses with high selectivity and sensitivity in water.[1] A variety of fluorescence sensors have been designed by combining an organic fluorophore and a metal-binding chelate,[2] but few examples of “turn-on” sensors that function in aqueous solutions have been reported. Recently, cadmium chalcogenide nanomaterials have emerged as a novel class of luminescent probes as a result of their unusual photoluminescence properties.[3] These materials are potentially useful for metal-ion sensing, as metal ions, including copper ions, are expected to interact with surface heteroatoms (S, Se, Te) to affect the optical properties of the material. Although the effects of metal ions on photoluminescence properties have been investigated for several nanoclusters and nanorods, only quenching effects have been reported for copper ions.[4, 5] Herein, we demonstrate a unique turn-on response of the water-soluble CdS cluster molecule 2 towards copper ions, and highlight its selectivity and sensitivity.The CdS cluster that we used in this study is a defined and neutral molecule with the general formula [Cd10S4 (SR) 12] which has a truncated tetrahedral Cd10S16 core and twelve surface substituents (R) attached to the sulfur atoms.[6] We reported recently that clusters capped by lipophilic groups (R= simple alkyl or aryl, such as 1) show surface-mediated emission at around 600 nm in organic solvents at ambient temperature.[7] To explore the properties of such molecular clusters in aqueous systems, we appended oligo (ethylene glycol)(OEG,-(OC2H4) nOCH3, n% 6) units to the surface phenyl groups of the phenyl-capped precursor 1 by the thiolate exchange reaction to give 2. In contrast to 1, the OEG-modified cluster 2 showed high solubility in water and in organic solvents such as acetonitrile and chloroform. In HEPES buffer (100 mm, pH 7.0) at 258C, 2 (6.7 μm) showed an emission band at 600 nm upon excitation of the cluster at 350 nm. The titration of this solution with [CuI-(CH3CN) 4] PF6 resulted in a notable enhancement of photoluminescence along with a slight red shift of the emission maximum to 620 nm (Figure 1 a).[8, 9] For example, when 2 was mixed with one molar equivalent of CuI ion, the intensity at 620 nm and the integrated band area increased by factors of 9.1 and 7.4, respectively. As shown in Figure 1b, the emission intensities at 620 nm increased upon the addition of CuI to reach a plateau at [CuI] 0/[2] 0% 2.0 with I/I0% 12.5.[10] The nearly linear correlation observed up to [CuI] 0/[2] 0= 1.0 allowed easy detection of CuI at nanomolar to micromolar concentrations. Under these conditions the dynamic range and the detection limit were estimated to reach 10 μm and approximately 0.07 μm (% 4 ppb), respectively. This sharp positive response that was observed was found to be highly specific to CuI. As summarized in Figure 2a, no