Block copolymer mediated stabilization of sub-5 nm superparamagnetic nickel nanoparticles in an aqueous medium

Abstract

The paper presents a facile method for decreasing the size of water dispersible Ni nanoparticles from 30 nm to 3 nm by the incorporation of a passivating surfactant combination of pluronic triblock copolymer and oleic acid into a wet chemical reduction synthesis. A detailed study revealed that the size of the Ni nanoparticles is critically governed not only by the concentration of the tri block copolymers but also dependent on the hydrophobic nature of the micelle-core formed. The synthesized Ni nanoparticles were thoroughly characterized by TEM, XRD, XPS and temperature and field dependent magnetic measurements along with a comprehensive FTIR analysis to predict a possible mechanism of formation. Mirkin and co-workers demonstrated the efficient and selective separation of His-tagged proteins using Ni-based nanorods with a diameter of about 300 nm [15]. Hyeon and co-workers have successfully proved that superparamagnetic Ni with NiO shells have a high affinity for poly histidine and can be utilized for separating and purifying His-tagged proteins from a multicomponent solution [16]. Introduction.Ni nanoparticles can be synthesised in both organic and aqueous media. The high temperature decomposition of nickel carbonyl compounds [17] or Ni(acac) 2 compounds [18] in the presence of oleylamine, tri octyl phosphine oxide (TOPO) and tri octyl phosphine (TOP) [19] are common organic routes. While these methods are capable of producing monodispersed Ni with sub 5 nm size range, partial oxidation on the surface of the particles occurs readily even with the use of more than one capping agent [19]. Furthermore, the complexity involved in the above synthetic procedures is quite evident, requiring many steps, higher temperature, inert atmosphere and the use of non-regular, toxic chemicals. Microemulsion based methods using mixtures of polar and non polar solvents have also

Size dependence of the magnetic properties of Ni nanoparticles prepared by thermal decomposition method

“…For the fabrication of Ni nanoparticles, methods such as sputtering [ 13 , 14 ], solution glow discharge [ 15 ], pulsed laser ablation [ 6 ], reversed micelles [ 16 ], thermal decomposition [ 17 - 20 ], and wet chemical reduction [ 7 , 21 , 22 ] are used. Among them, the ones based on thermal decomposition are preferred.…”

Pharmacokinetics and Applications of Magnetic Nanoparticles

“…He et al used the Stable Ni nanoparticles of 24-200 nm in size pre-pared by a thermal decomposition method and their result showed that with the increase of particle size, the saturation magnetization increases monotonically, and the coercivity decreases at first and then increases. These results provided evidence for the existence of size effect and shape anisotropy in Ni nanoparticles [40,[41][42][43].…”

Magnetic Properties of Cluster Glassy Ni/NiO Core–Shell Nanoparticles: an Investigation of Their Static and Dynamic Magnetization

“…This anomalous enhancement of the effective anisotropy indicates that the maximum in the ZFC magnetization does not correspond to the typical blocking temperature of the noninteracting particles, where inter-particle interaction, including dipole–dipole and exchange, plays a significant role in the temperature dependence of the magnetization. An enhancement of the effective magneto-crystalline nanoscale anisotropy is also observed, such as K eff = 1.46 × 10 6 erg/cm 3 in < d > = 11 nm and K eff = 7.03 × 10 6 erg/cm 3 in < d > = 3.71 nm, for Ni nanoparticles fabricated by the chemical reduction synthesis method [ 27 ]. Similar behaviors are also observed in Co nanoparticles [ 28 ].…”