Regulating the molecule and electrode interface of a single-molecule junction via the side chain.

Here, we report that the molecule-electrode interface of a single-molecule junction can be regulated by a side chain. Based on this regulation, a single-molecule junction probe, PyCHO, was developed, which could distinguish cysteine (Cys) and homocysteine (Hcy) with high selectivity and sensitivity. PyCHO reacts with Cys/Hcy at ambient conditions to form thiazolidine/thiazinane products PyCHO+Cys/PyCHO+Hcy. Single molecular conductance measurement shows PyCHO+Cys and PyCHO+Hcy have different conductance. Control experiments and theoretical results reveal that the side thiazolidine/thiazinane rings have a distinct effect on the Au-π interaction of the pyridine anchor, resulting in their different conductances.