Spectral–optical–electrical–thermal properties of deposited thin films of nano-sized calcium(II)-8-hydroxy-5,7-dinitroquinolate complex

Spectral–optical–electrical–thermal properties of deposited thin films of nano-sized calcium(II)-8-hydroxy-5,7-dinitroquinolate complex, Ca[((NO2)2-8HQ)2], were explored, studied and evaluated in this work. Thin films of Ca[((NO2)2-8HQ)2] were assembled by using a direct, simple and efficient layer-by-layer (LBL) chemical deposition technique. The optical properties of thin films were investigated by using spectrophotometric measurements of transmittance and reflectance at normal incidence in the wavelength range 200–2500 nm. The refractive index, n, and the absorption index, k, of Ca[((NO2)2-8HQ)2] films were determined from the measured transmittance and reflectance. The real and imaginary dielectric constants were also determined. The analysis of the spectral behavior of the absorption coefficient in the intrinsic absorption region reveals a direct allowed transition with band gaps of 1.1 eV and 2.4 eV for the optical and transport energy gaps, respectively. The current–voltage characteristics of Ca[((NO2)2-8HQ)2] showed a trap-charge limited conduction in determining the current at the intermediate and high bias regimes. Graphical representation of the current–voltage characteristics yields three distinct linear parts indicating the existence of three conduction mechanisms. Structural characterization and identification were confirmed by using Fourier transform infrared spectroscopy (FT-IR). Scanning electron microscopy (SEM) was also used to image the surface morphology of the deposited nano-sized metal complex and such study revealed a high homogeneity in surface spherical particle distribution with average particles size in the range 20–40 nm. Thermal gravimetric analysis (TGA) was also studied for [(NO2)2-8HQ] and Ca[((NO2)2-8HQ)2] to evaluate and confirm the thermal stability characteristics incorporated into the synthesized nano-sized Ca[((NO2)2-8HQ)2] complex.

Graphical abstractNano-sized thin films of Ca[((NO2)2-8HQ)2] complex, were prepared by using a direct, simple and efficient layer-by-layer (LBL) chemical deposition technique. Structural characterization was identified by FT-IR, SEM, TGA and elemental analysis. The spectral, optical, electrical and thermal properties of the complex was studied, explored and discussed.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A simple, direct and efficient synthesis of nano-sized metal complex by LBL. ► Structural characterization by FT-IR, SEM and elemental analysis. ► Spectral and optical properties was studied and evaluated. ► Semi-conducting properties was identified for Ca(II)-8-hydroxy-5,7-dinitroquinolate. ► Thermal analysis and stability was explored.