原子级结构精确Cu_(13)团簇的光致发光和电化学传感研究

Photoluminescence and Electrochemical Sensing of Atomically Precise Cu_(13) Cluster

铜基纳米材料在发光和(生物)化学传感领域展现出广阔的应用前景.铜纳米团簇作为一种新型的纳米材料,由于其具有原子级精确的结构而引起了研究人员的广泛关注,但是合成稳定并且具有优异性能的铜簇仍然具有挑战性.本工作通过引入还原剂(NaBH_(4))成功地制备出一种新型的巯基咪唑配体保护的一价铜纳米团簇[Cu_(13)(SR)_(12)]NO_(3)(Cu_(13) NC,其中RSH=2-巯基苯并咪唑),并通过单晶X射线衍射分析和电喷雾电离质谱(ESI-MS)对其结构和组成进行了表征.Cu_(13) NC的金属骨架可以看成是三个三角双锥共享一个或两个顶点构成,并通过简单的桥联模式被12个巯基配体保护.固态Cu_(13) NC具有良好的稳定性及亮红色的发光(λ_(em)=627 nm).同时,结构的两端有两个裸露的铜原子,这使其在电化学检测H_(2)O_(2)的实验中表现出良好的电化学活性.本工作为更好地研究纳米铜簇的结构和其光、电性能之间的联系提供了机会.

Copper-based nanomaterials show widespread applications in the fields of luminescence and(bio)chemical sensing.Copper nanoclusters as a new class of nanomaterials have attracted extensive attention due to their atomic-level structure,but the syntheses of stable atom-precise copper clusters with good properties are still challenging.In this work,we have successfully prepared a novel mercaptoimidazole-stabilized copper(Ⅰ)nanocluster:[Cu_(13)(SR)_(12)]NO_(3)(Cu_(13) NC,where RSH=2-mercaptobenzimidazole)by introducing the reducing agent(NaBH_(4))in an acetonitrile-methanol solution of copper nitrate and RSH.The presence of NaBH_(4) not only reduced Cu(Ⅱ)to Cu(Ⅰ)but also provided a reducing system to avoid the reversed oxidation.The structure and composition of Cu_(13) NC have been collectively elucidated by X-ray crystallography and electrospray ionization mass spectrometry(ESI-MS).The metal framework of Cu_(13) NC can be seen as three triangular bipyramids sharing one or two vertices,which are surrounded by 12 thiolate ligands as protecting agents through a simple bridging mode.Since the counterions in the crystal lattice are highly disordered and could not be located,the existence of NO_(3)-has been confirmed by infrared spectroscopy and ESI-MS.Cu_(13) NC exhibits good stability under ambient conditions and shows bright-red emission in the solid state(λ_(em)=627 nm).The long-life emission in the order of microseconds and large Stokes shift(≈280 nm)indicate that the luminescence of Cu_(13) NC is a spin-forbidden triplet phosphorescence.The absolute quantum yield of the solid-state Cu_(13) NC was calculated to be 1.36%.Meanwhile,there are two exposed copper atoms at each end of the structure,endowing Cu_(13) with good electrochemical activity.The test confirmed that Cu_(13) NC shows prompt response,and great selectivity in electrochemical detection of H2 O2,making it a low-cost advanced H_(2)O_(2) sensing material.This work provides an opportunity to investigate the structure-optical and electrochemical property relationship of copper clusters.