Magnetite nanoparticles procedure

Nanoparticle Synthesis and Immobilization Procedures 2.7.1 Synthesis of Functionalized Magnetite Nanoparticles... 

Figure 2.12 The procedure for monodisperse magnetite nanoparticles via chitosan-poly(acrylic acid) template [22].

The formation of uniform nanoparticles with high amounts of magnetite can be obtained most successfully by the three-step process involving the co-sonication procedure (see Fig. 14) [135,136]. In the first step, magnetite (10 nm) nanoparticles are formed by precipitation from a ferrous and ferric chloride solution... 

A dielectric oxide layer such as silica is useful as shell material because of the stability it lends to the core and its optical transparency. The thickness and porosity of the shell are readily controlled. A dense shell also permits encapsulation of toxic luminescent semiconductor nanoparticles. The classic methods of Stober and Her for solution deposition of silica are adaptable for coating of nanocrystals with silica shells [864,865]. These methods rely on the pH and the concentration of the solution to control the rate of deposition. The natural affinity of silica to oxidic layers has been exploited to obtain silica coating on a family of iron oxide nanoparticles including hematite and magnetite [866-870]. The procedures are mostly adaptations of the Stober process. Oxide particles such as boehmite can also be coated with silica [871]. Such a deposition process is not readily extendable to grow shell layers on metals. The most successful method for silica encapsulation of metal nanoparticles is that due to Mulvaney and coworkers [872—875]. In this method, the smface of the nanoparticles is functionalized with aminopropyltrimethylsilane, a bifunctional molecule with a pendant silane group which is available for condensation of silica. The next step involves the slow deposition of silica in water followed by the fast deposition of silica in ethanol. Changes in the optical properties of metal nanoparticles with silica shells of different thicknesses were studied systematically [873 75]. This procedure was also extended to coat CdS and other luminescent semiconductor nanocrystals [542,876-879]. 

---