The binding sites of carboxylic acid group contacting to Cu electrode

•ECSTM-BJ method was used to measure single molecular conductance with Cu electrode.•Conductance of molecules with carboxylic acid, carbonyl and methanol was measured.•Carbonyl group can be used as an effective anchoring group binding to Cu.•Carboxylic acid can bind to the electrode through carbonyl and carboxylate groups.•It's difficult to form single molecular junction through methanol anchoring group.

In this work, the binding sites of carboxylic acid binding to Cu electrode are explored by electrochemical jump-to-contact STM break junction. Single molecular conductance of benzene-based molecules with ending groups of carboxylic acid, carbonyl and hydroxyl are measured and compared. The conductance values of 1,4-benzenedicarboxaldehyde can be found in those of 1,4-benzenedicarboxylic acid, which shows that carboxylic acid can bind to Cu electrode through carbonyl group. Carboxylic acid can also bind to the electrode through carboxylate group, and gives out larger conductance values than those of carbonyl group. However, molecule with hydroxyl group is difficult to form single molecular junction with Cu. The current work demonstrates that the carboxylic acid can bind to the electrode through carbonyl and carboxylate groups, and a new anchoring group of carbonyl group can be used to form effective single molecular junction.

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