Spectroscopic investigation and characterization of polypyrrole film doped with [MeN 4] 2[Ni(dmit) 2] complex salt

Abstract

Polypyrrole doped with bis(1,3-dithiole-2-thione-4,5-dithiolate) nickellate (II) (PPy/[Ni(dmit) 2] 2−) was electropolymerized in acetonitrile solution and characterized by Fourier transform infrared (FTIR), ultraviolet–visible (UV–vis), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopies, as well as cyclic voltammetry (CV), conductivity, and scanning electron microscopy (SEM) measurements. Ionic desorption studies conducted by photon stimulated ion desorption (PSID) were also performed using synchrotron radiation at the S K-edge and time-of-flight mass spectrometry (ToF-MS) for ion analysis. The spectroscopic techniques indicated that the [Ni(dmit) 2] 2− was inserted onto the PPy backbone without modification during the electropolymerization process. Loss of electroactivity during the oxi-reduction processes indicated that the [Ni(dmit) 2] 2− leaves the film, undergoing anion exchange during the redox cycle. PPy/[Ni(dmit) 2] 2− exhibited higher intrinsic conductivity value than other PPy/M-dmit films studied previously. SEM measurements showed an irregular and heterogeneous surface with steps formation. PSID results showed that the species desorb through the X-ray induced electron stimulated desorption (XESD) mechanism while atomic sulfur species are mainly formed by Auger stimulated ion desorption (ASID). These results confirmed the presence of [Ni(dmit) 2] 2− at the topmost layers of the hybrid film.