[Co(NH3)5(NO3)](NO3)2 as an energetic coordination precursor for the preparation of Co3O4 nanoparticles at low temperature

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In this paper, an energetic coordination compound namely pentamminenitratocobalt(III) nitrate, [Co(NH3)5(NO3)](NO3)2, was used as a new precursor for the preparation of Co3O4 nanoparticles. The results showed that the complex is easily decomposed into the Co3O4 nanoparticles at low temperature (200 °C) without employing a surfactant or solvent and any complicated equipment. The product was characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). Optical and magnetic properties of the product were studied by UV-visible (UV-vis) spectroscopy and a vibrating sample magnetometer (VSM), respectively. FT-IR, XRD and EDS analyses confirmed the formation of highly pure spinel-type Co3O4 phase with cubic structure. TEM images showed that the Co3O4 nanoparticles are approximately in the range of 10 to 24 nm with a mean size of around 17 nm. The optical spectrum of the Co3O4 nanoparticles revealed the presence of two band gaps at 3.45 and 2.20 eV which are blue-shifted relative to reported values for the bulk sample. The magnetic measurement of the product showed a weak ferromagnetic order at room temperature.