High Coercivity of Oleic Acid Capped CoFe₂O₄ Nanoparticles at Room Temperature

Abstract

High coercivity (9.47 kOe) has been obtained for oleic acid capped chemically synthesized CoFe(2)O(4) nanoparticles of crystallite size approximately 20 nm. X-ray diffraction analysis confirms the formation of spinel phase in these nanoparticles. Thermal annealing at various temperatures increases the particle size and ultimately shows bulk like properties at particle size approximately 56 nm. The nature of bonding of oleic acid with CoFe(2)O(4) nanoparticles and amount of oleic acid in the sample is determined by Fourier transform infrared spectroscopy and thermogrvimetric analysis, respectively. The Raman analysis suggests that the samples are under strain due to capping molecules. Cation distribution in the sample is studied using Mossbauer spectroscopy. Oleic acid concentration dependent studies show that the amount of capping molecules plays an important role in achieving such a high coercivity. On the basis of above observations, it has been proposed that very high coercivity (9.47 kOe) is the result of the magnetic anisotropy, strain, and disorder of the surface spins developed by covalently bonded oleic acid to the surface of CoFe(2)O(4) nanoparticles.

Controlled Synthesis of CdSe Quantum Dots by a Microwave‐Enhanced Process: A Green Approach for Mass Production

“…[21] When oleic acid is chemisorbed on the surface of CdSe QDs, the asymmetric and symmetric CH 2 stretching bands shifted to 2919 and 2851 cm À1 , respectively. [21,22] The FTIR spectrum of pure oleic acid shows an intense peak at 1710 cm À1 and a band at 1285 cm À1 due to C=O and C À O stretching, respectively, as well as the in-plane and out-of-plane OH bands at 1463 and 934 cm À1 , respectively. [21,22] However, these bands disappeared in CdSe QDs, and two new bands appeared at 1540 and 1430 cm À1 that are characteristic of asymmetric n as (COO À ) and symmetric n s A C H T U N G T R E N N U N G (COO À ) stretching.…”

“…[21,22] The FTIR spectrum of pure oleic acid shows an intense peak at 1710 cm À1 and a band at 1285 cm À1 due to C=O and C À O stretching, respectively, as well as the in-plane and out-of-plane OH bands at 1463 and 934 cm À1 , respectively. [21,22] However, these bands disappeared in CdSe QDs, and two new bands appeared at 1540 and 1430 cm À1 that are characteristic of asymmetric n as (COO À ) and symmetric n s A C H T U N G T R E N N U N G (COO À ) stretching. [21,22] This reveals that oleic acid is chemisorbed as a carboxylate onto the surface of CdSe QDs.…”

Effect of Surface Functionalization on the Adsorption of Arsenic Using Magnetite Nanocrystals

“…The weight loss associated with the second step was higher in the case of the DMSA-magnetite sample, 29.49%, which was attributed to the thermal decomposition of adsorbed DMSA. These decreases in the sample weight were used to estimate the number of adsorbed SO and DMSA molecules per particle, using the relation described by equation (4) (Limaye et al 2009). In this equation, N is the number of ligands per particle, w is the weight loss percent, N A is the Avogadro number, ρ is the density of magnetite (about 5.18 g/cm 3 ), R is the average radius of the nanocrystals (10.9 nm for SO-magnetite and 9.7 for DMSA-magnetite based on the XRD analysis) and M is the molecular weight of SO (304.44 g/mol) or DMSA (182.22 g/mol).…”

Simple Non-aqueous Fabrication Route for Oleic Acid Capped Luminescent Cadmium Sulphide Quantum Dots at Relatively Low Temperature

“…Among the various capping agents, oleic acid (OA) is one of the well-known capping agents for various QDs. The nature of binding of OA depends on the synthesis route used and in the most of these routes, OA is chemisorbed as carboxylate onto QDs surface leading to good stability and better size control [22].…”