Microwave-Assisted Synthesis of Magnetic Ni Wire from a Metal−Organic Precursor Containing Ni(II) and Triethanolamine

Abstract

A novel approach is proposed to synthesize Ni wire by microwave (MW) heating of the preorganized rod microstructure of crystal consisting of Ni2+ ions and triethanolamine (TEA). Field emission scanning electron microscopy (FESEM) studies of the Ni-TEA crystal reveal that TEA molecules lead to the formation of sub-micrometer-sized needle bundles that appear as a sheaf of straw tied in the middle. The organized structure stems from the hydrogen bonding, which is evident from single crystal X-ray diffraction and infrared spectroscopic (IR) studies. Microscopic studies using scanning electron microscopy, transmission electron microscopy, and atomic force microscopy show that nanoparticles of ∼12 nm are connected to each other and build the equilibrium wire structure. Thermogravimetric analysis-differential thermal analysis experiments in association with X-ray diffraction studies provide direct evidence that microwave irradiation plays a crucial role in stabilizing the pure Ni phase. The high blocking temperature, TB ∼ 300 K, with a remnant magnetic moment (MR) of 12 emu/g of the Ni wire is observed, allowing for room temperature magnetic applications. The observation of high blocking temperature is due to the interparticle interaction and high magnetocrystalline anisotropic constant, K = 19.2 × 105 erg cm−3 of the Ni nanoparticles. The advantages of the proposed method are, no need to use external template and reducing agent, and second sample can be prepared in air and aqueous medium