Solvent dependent morphology and 59Co internal field NMR study of Co-aggregates synthesized by a wet chemical method.

Different shapes of Co-aggregates were synthesized via reduction of a Co salt (CoCl2·6H2O) by chemical precipitation using glycerol, ethylene glycol and ethanol as solvents. The effect of solvent on the morphology, fcc or hcp phase-content and the magnetic properties of the synthesized samples were investigated. The Co-aggregates synthesized using glycerol have a dense spherical shape and high saturation magnetization (MS), whereas ethylene glycol leads to formation of flower-shaped spherical aggregates through loose packing of smaller plate-like particles which have a moderate MS value. When ethanol was used as a solvent, a dendritic (leaf like)-shape of the aggregates with the lowest MS value was obtained. The formation of the obtained morphology of the aggregates was explained based on the size of the solvent molecule, the viscosity of the solvent and the number of polar groups (-OH) present in the solvent molecules. The magnetic domain state and domain wall dynamics of all the Co-samples were investigated using 59Co Internal Field Nuclear Magnetic Resonance (IFNMR) spectroscopy at RT and at 77 K. Through the IFNMR spectroscopy, the presence of gain boundaries, single domain particles and multi-domain particles/aggregates with domain walls associated with fcc and hcp phases were identified and quantified. We observed that the use of ethanol facilitates formation of a higher amount of hcp phase in the sample than the use of glycerol or ethylene glycol.

Synthesis, characterization and optical properties of ligand-protected indium nanoparticles.

Unlike silver and gold, indium has material properties that enable strong resonances extended up to the ultraviolet. This extended response, combined with low cost, and ease of synthesis process, makes indium a highly promising material for applications. In this work, we have synthesized ligand-protected indium nanoparticles by a metal reduction method. Powder X-ray diffraction and EDX analyses are consistent with the presence of metallic indium in the nanoparticles. Ligand binding was proven by IR spectroscopy and TGA experiments. TEM analyses reveal that the particle size ranges from 6.3 to 4.8 nm. Optical measurements show that the absorption maximum is red shifted as the particle size decreases.