Highly dispersed copper oxide (CuO) nanoparticles with an average size of 6 nm have been successfully prepared by a novel quick-precipitation method. The as-prepared CuO nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–Visible absorption spectroscopy and BET nitrogen adsorption. The results show that the as-prepared CuO nanoparticles have high dispersion and narrow size distribution. The influence of reaction conditions on morphology of CuO nanocrystals was discussed. Spherical, ellipsoidal and needle-shaped CuO nanocrystals can be obtained simply by varying the reaction temperature and controlling the addition of NaOH.

Highly dispersed CuO nanoparticles prepared by a novel quick-precipitation method

Recent advances and prospect of cobalt based microwave absorbing materials

Magnetic properties of Co3O4 polycrystal powder

In the present investigation, pristine nickel oxide (NiO) and cobalt oxide (Co3O4) nanoparticles have been synthesised by well pronounced sol-gel auto combustion route. A series of Co3O4-NiO nanocomposite with varying NiO concentration from 10% to 40% by weight to Co3O4, has been synthesised using sonochemical route. A qualitative study of structural, optical and magnetic properties of the nanocomposite series of Co3O4-NiO was performed by analysing X-Ray Diffraction, Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Ultra violet Diffuse Reflectance Spectroscopy (UV-DRS), Transmission Electron Microscopy (TEM), X-Ray Photoelectron Spectroscopy (XPS) and Vibrating Sample Magnetometer (VSM) as well as electron paramagnetic resonance (EPR). From XRD measurements, crystalline phases of pure NiO, Co3O4 and their composites have been confirmed. The crystallite sizes determined by Debye Scherer and Williamson Hall methods were found in good agreement. The interplanar spacing has been calculated using HRTEM images for the synthesised samples. Raman analysis confirms the presence of bands and witnesses the formation of the pure and composite samples. From VSM measurements at room temperature M-H curves witnessed the weak ferromagnetism along antiferromagnetic portion in the samples of NiO & Co3O4-NiO nanocomposites whereas Co3O4 is purely antiferromagnetic. Moreover, EPR measurements confirm the presence of unpaired electrons and field resonance decreases with increase in g value with increasing NiO concentration in the composite samples as compared to NiO sample.

Interfacial exchange coupling and defects driven magnetic and optical properties of Co3O4-NiO nanocomposites

In this study, synthesis and characterization of cobalt oxide nanoparticles (Co3O4 NPs) using green tea leaf (Camellia sinensis) and its utilization as high-performance supercapacitors has been studied. Co3O4 NPs were fabricated utilizing aquatic extract of Camellia sinensis as a reduction agent, and it was annealed at various annealing temperatures, such as 200 °C, 400 °C, 600 °C, and 800 °C for 2 h. The synthesized Co3O4 NPs were analyzed using XRD, FESEM, EDX, HRTEM, PL, FTIR, UV–visible techniques. The higher concentration of phenolic compounds with antioxidant potential, amino acids, proteins and lipids in Camellia sinensis act as the reducing as well as the stabilizing agents for the growth of NPs. The XRD analysis confirms that the crystalline behavior of the annealed samples increases with increasing annealing temperature. The electrochemical performance of green synthesized nanostructured Co3O4 NPs shows an excellent supercapacitance performance with quick dispersing of electrolyte ions into the Co3O4 electrode owing to their rapid charging and discharging performances. This affirms that the bio-synthesized Co3O4 nanomaterial is the appropriate material for high performance supercapacitor applications.

Facile synthesis and characterization of Co 3 O 4 nanoparticles for high-performance supercapacitors using Camellia sinensis

Quick precipitation method is simple and efficient to obtain cobalt oxide (Co3O4) nanoparticles. The prepared cobalt oxide was characterized by powder X-ray diffraction pattern confirmed the formation of single phase Co3O4. Scanning electron microscope image indicates the sphere like morphology and its grain size will be in the range of 50–100 nm. UV-DRS optical property of Co3O4 shows a band gap in the energy range of 3.50 eV. A vibrating sample magnetometer for the analysis of Co3O4 sample showed it to behave as a soft ferromagnetic material.

A. Rubankumar

Papers

Synthesis, Characterization, Optical, and Magnetic Properties of Co3O4 Nanoparticles by Quick Precipitation