Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Nat Mater. 2012 Nov;11(11):978-85. doi: 10.1038/nmat3406. Epub 2012 Sep 9.
Although multiple methods have been developed to detect metal cations, only a few offer sensitivities below 1 pM, and many require complicated procedures and sophisticated equipment. Here, we describe a class of simple solid-state sensors for the ultrasensitive detection of heavy-metal cations (notably, an unprecedented attomolar limit for the detection of CH(3)Hg(+) in both standardized solutions and environmental samples) through changes in the tunnelling current across films of nanoparticles (NPs) protected with striped monolayers of organic ligands. The sensors are also highly selective because of the ligand-shell organization of the NPs. On binding of metal cations, the electronic structure of the molecular bridges between proximal NPs changes, the tunnelling current increases and highly conductive paths ultimately percolate the entire film. The nanoscale heterogeneity of the structure of the film broadens the range of the cation-binding constants, which leads to wide sensitivity ranges (remarkably, over 18 orders of magnitude in CH(3)Hg(+) concentration).
虽然已经开发出多种方法来检测金属阳离子，但只有少数几种方法的灵敏度低于 1 pM，而且许多方法需要复杂的程序和复杂的设备。在这里，我们描述了一类简单的固态传感器，用于通过保护有机配体条纹单层的纳米颗粒（NPs）薄膜中隧穿电流的变化来超灵敏地检测重金属阳离子（特别是，在标准溶液和环境样品中对 CH(3)Hg(+)的检测具有前所未有的亚皮摩尔极限）。由于 NPs 的配体壳组织，传感器也具有高度选择性。在与金属阳离子结合时，相邻 NPs 之间的分子桥的电子结构发生变化，隧穿电流增加，最终高导电性路径渗透整个薄膜。薄膜结构的纳米尺度异质性拓宽了阳离子结合常数的范围，从而导致宽的灵敏度范围（值得注意的是，在 CH(3)Hg(+)浓度方面超过 18 个数量级）。
