Synthesis, characterization and optical–electrical properties of the thin film deposited nano-Co(II)-8-hydroxy-5-nitrosoquinolate complex via the layer-by-layer chemical deposition technique

Abstract

Cobalt(II)-8-hydroxy-5-nitrosoquinolate [ Co(II)-(HNOQ) 2 ] was synthesized and deposited as a thin film in the form of a nano-aggregate metal complex via a direct, simple and efficient layer-by-layer (LBL) chemical deposition technique. Structural characterization and stoichiometric identification were confirmed using elemental analysis, electron impact mass spectrometry (EI-MS) and Fourier Transform infrared spectroscopy (FT-IR). The surface morphology was studied using scanning electron microscopy (SEM). Thermal gravimetric analysis (TGA) was used to confirm the thermal stability characteristics of the synthesized nano [ Co(II)-(HNOQ) 2 ] complex. This was interpreted on the basis of the presence of a nitroso-group as a substituent compared to cobalt(II)-8-hydroxyquinolate [ Co(II)-(HQ) 2 ]. The absorption spectra recorded in the UV–Vis region showed a single well-defined absorption band of the cobalt(II)-8-hydroxy-5-nitrosoquinolate molecule, namely the Q-band. According to the analysis of the absorption curves, the optical absorption coefficient ( α), molar extinction coefficient ( ε molar), oscillator strength ( f), and electric dipole strength ( q 2) were evaluated. The analysis of the spectral behavior of the absorption coefficient ( α) revealed two direct allowed transitions with energies of 1.48 and 2.33 eV. The temperature dependence of the electrical resistance yields two distinct linear parts, indicating the existence of two activation energies Δ E 1 and Δ E 2 of 0.19 and 0.70 eV, respectively. These activation energies are related the extrinsic and intrinsic conduction, respectively.