A molecular-gap nanodevice for selective determination of mercury ions has been demonstrated by the research group led by Prof. Jinhuai Liu and Prof. Xingjiu Huang  who is a member of Hundred Talents Program, from Hefei Institutes of Physical Science, Chinese Academy of Sciences. The result has been accepted for publication in Scientific Reports （Sci. Rep. 3, 3115; DOI: 10.1038 / srep 03115 (2013)）.

　　Through assembling Au nanoparticles functionalized with glutathione (GSH) monolayer between the interdigitated microelectrodes, a molecular-gap device has been indirectly developed. The fabricated device exhibits a high selectivity and can be effectively employed for the determination of Hg²⁺. The limit of detection (LOD) is down to 1 nM. For other metal ions including Zn²⁺, Cd²⁺, Pb²⁺ etc, no change in resistance/conductivity was observed. To illuminate its specific sensing mechanism, theoretical calculations have been further performed. Generally, the selectivity of conventional sensing devices mainly depends on the complexing ability between the analyte and sensing materials. However, researchers found that the selectivity of the fabricated molecular-gap device does not depend on the binding affinity between the modifier (GSH) and the heavy metal ions. The key factor contributing to its sensing mechanism is that the frontier molecular orbital of the glutathione dimer bridged by heavy metal ions between Au nanoparticles are responsible for the electron transport of the molecular-gap device. Undoubtedly, this finding will expectedly mark a new route to develop future nanodevices with the sensing specificity.

　　This works is financially supported by the National Key Scientific Program-Nanoscience and Nanotechnology (2011CB933700) and the National Natural Science Foundation of China (Grant Nos. 61106012, 61102013, and 21073197).