Organometallic gold nanoparticles and thin films from cis- and trans-tetrazonium gold(III) salts for electrochemical and photothermal mirror properties

Tetrazonium gold(III) salts of syn-(cis) and anti-(trans) geometry of 4,4′-(1,3-phenylenediisopropylidene)bisaniline and 4,4′-(1,4-phenylenediisopropylidene)bisaniline were synthesized. HAuCl₄ was used as a metal-based counter anion precursor. The gold-carbon nanoparticles (AuNPs) were constructed using the mild reducing agent organoborane 9-borabicyclo[3.3.1]nonane (9-BBN). The nanoparticles dispersed in acetonitrile showed a plasmon peak at 540 nm. Dynamic light scattering measurements showed the size of cis-AuNPs is smaller than the trans-AuNPs. Transmission electron microscopy images showed the formation of spherical shaped AuNPs. X-ray diffraction, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy results supported the presence of metallic gold in both the cis and trans AuNPs. Electrochemical studies of the tetrazonium salts showed the facile reduction and the blocking effect of the films formed on glassy carbon electrodes. The photothermal mirror method was used to study the thermal diffusivity of gold thin films deposited over a glassy carbon substrate. The values of the thermal diffusivity coefficient were determined for the cis and trans isomers of the film.