Formation of Molecular Wires by Nanospace Polymerization of a Diacetylene Derivative Induced with a Scanning Tunneling Microscope at a Solid-Liquid Interface

Abstract

A nanospace polymerization reaction was initiated using a scanning tunneling microscope in a monolayer of a diacetylene derivative, 10, 12-nonacosadiynoic acid (NCDA), at a solid-liquid interface to obtain molecular wires. The polymerization threshold with respect to the applied voltage was 2 V, which was 1 V lower than that observed at a solid-air interface. The presence of ionic species considerably enhanced the reaction probability. At more than ±2 V, the addition of N(CH3)4ClO4 resulted in the expansion of the reaction region and the increase in reaction probability regardless of the sign of the bias voltage applied. Different from the case at the solid-air interface, polymerization at the solid-liquid interface was probably induced through the multiple vibrational excitation of NCDA by repetitive collisions with charged carriers activated by the strong electric field involved in electron avalanche.