Voltammetric, EQCM, spectroscopic, and microscopic studies on the electrocrystallization of semiconducting, phase I, CuTCNQ on carbon, gold, and platinum electrodes by a nucleation-growth process

Cu 7,7,8,8-tetracyanoquinodimethane (CuTCNQ) may be chemically synthesized in two phases, one of which is significantly more conductive (phase I) than the other (phase II). Because CuTCNQ is sparingly soluble in acetonitrile, reduction of TCNQ to TCNQ(center dot-) in the presence of Cu-(MeCN)(+) under conditions where the solubility is exceeded in this solvent allows CuTCNQ nucleation-growth processes to occur at defect sites on carbon, gold, and platinum macro- and microdisk electrode surfaces. Rapid growth of large branched needle-shaped phase I crystals occurs on the time scale of cyclic voltammetry at semiconducting CuTCNQ nucleation sites. Infrared spectra and the crystal morphology detected by electron microscopy of electrocrystallized solid, are all consistent with growth of purely phase I CuTCNQ solid. The smaller crystals formed on the electrode surface, but not larger ones, may be stripped from the electrode surface by application of positive potentials. Mechanistic aspects of the electrocrystallization and stripping processes are considered. (c) 2005 The Electrochemical Society.