In this work CoFe2O4 spinel ferrite nanoparticles were synthesized by honey mediated sol-gel combustion method and further annealed at higher temperature 500 °C, 700 °C, 900 °C and 1100 °C. The synthesized spinel ferrite nanoparticles is investigated by x-ray diffraction, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), field emission scanning electron microscopy, x-ray photoelectron spectroscopy and vibrating sample magnetometer. The x-ray diffraction study reveals face-centered cubic spinel cobalt ferrite crystal phase formation. The crystallite size and lattice parameter are increased with annealing temperature. Raman and Fourier transform infrared spectra also confirm spinel ferrite crystal structure of synthesized nanoparticles. The existence of cation at octahedral and tetrahedral site in cobalt ferrite nanoparticles is confirmed by x-ray photoelectron spectroscopy. Magnetic measurement shows increased saturation magnetization 74.4 emu g−1 at higher annealing temperature 1100 °C, high coercivity 1347.3 Oe at lower annealing temperature 500 °C, and high remanent magnetization 32.3 emu g−1 at 900 °C annealing temperature. The magnetic properties of synthesized ferrite nanoparticles can be tuned by adjusting sizes through annealing temperature. Furthermore, the dielectric constant and ac conductivity shows variation with frequency (1–107 Hz), grain size and cation redistribution. The modulus spectroscopy study reveals the role of bulk grain and grain boundary towards the resistance and capacitance. The cole-cole plots in modulus formalism also well support the electrical response of nanoparticles originated from both grain and grain boundaries. The dielectric, electrical, magnetic, impedance and modulus spectroscopic characteristics of synthesized CoFe2O4 spinel ferrite nanoparticles demonstrate the applicability of these nanoparticles for magnetic recording, memory devices and for microwave applications.
Versatile approaches to nanoparticle synthesis offer unprecedented opportunities for the development of optoelectronics, photonics, as well as bio sciences. With the current advancement of hybrid organic-inorganic metal halide perovskites, the next step is to expand their field of applications via utilization of functional and modifiable ligand chemistry. Here, we present a ligand assisted reprecipitation approach for highly luminescent perovskite nanoparticle synthesis using for the first time L-lysine and L-arginine for surface passivation. These nanoparticles exhibit emission within a narrow bandwidth of the visible spectrum and photoluminescence quantum yield close to 100%. Additionally, preferential ligand orientation is achieved via amino acids α-amino group blocking which results in blueshifted emission as well as smaller and more uniform particle size. These experimental results demonstrate the effectiveness of naturally occurring proteinogenic amino acids as surface ligands and offer possibilities for versatile modification of perovskite nanoparticle properties via well-studied amino acid chemistry.
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