Ferromagnetic Nanomaterials

Farah Salim

2014-2015

Content:▶ Introduction to magnetic nanomaterials.▶Magnetic properties.▶Ferromagnetic materials.▶Effects of temperature and the magnetic field on

ferromagnetic materials.▶Basic properties of ferromagnetic materials.▶Methods of Preparation.▶Applications.

Introduction• Magnetic nanoparticles are a class of nanoparticle

which can be manipulated using magnetic field.

• Such particles commonly consist of magneticelements such as ferromagnetic metals (iron,nickel and cobalt), alloys and oxides.

• Require size control and narrow size distribution.

• Perform best in the size range 10-20 nm invarious applications.

Magnetic Properties

Material

Magnetic (with unpaired electron).

Non-magnetic or diamagnetic (electrons allpaired up).

A material is considered ferromagnetic if it can bemagnetized. Materials with a significant Iron, nickel orcobalt content are generally ferromagnetic.Ferromagnetic materials are made up of many regions inwhich the magnetic fields of atoms are aligned. Theseregions are call magnetic domains.Magnetic domains point randomly in demagnetized material,but can be aligned using electrical current or an externalmagnetic field to magnetize the material.

Ferromagnetic Materials

observable magnetic properties that are commonlyassociated with ferromagnetic materials are:1. Magnetic saturation.2. Magnetic remanance.3. Coercivity.These observable properties are characterized bymeasuring the magnetic moment of a material as afunction of an applied magnetic field. A samplemagnetization vs. applied magnetic field curve can beseen in next figure.

Basic properties of ferromagnetic materials

Figure (1): Representative plot of magnetization measuredas a function of applied magnetic field for a ferromagneticmaterial.

Effect of Temperature

Figure (2): Effect of temperature on magnetic materials.

Effect of the applied magnetic field

Figure (3): Ferromagnetic particles under the influence of an external magnetic field.

Figure (4): Ferromagnetic particles in absence of an external magnetic field.

Methods of preparation:1. Co-precipitation:This method may be the most promising one because of itssimplicity and productivity. It is widely used forbiomedical applications because of ease of implementationand need for less hazardous materials and procedures.Co-precipitation is specifically the precipitation of anunbound "antigen along with an antigen-antibodycomplex" in terms of medicine. The reaction principle issimply as:

2. Thermal decomposition.The decomposition of iron precursors in the presence of hot organicsurfactants has yielded markedly improved samples with good sizecontrol, narrow size distribution and good crystallinity of individualand dispersible magnetic iron oxide nanoparticles.

Figure (4):Synthesis of iron oxide by thermal decompositionmethod.

3. Micro emulsion ( reverse micelle method).Water-in-oil (W/O) micro emulsions systems, a fine microdroplets of the aqueous phase trapped within assemblies ofsurfactant molecules dispersed in a continuous oil phase.The surfactant-stabilized micro cavities (typically in therange of 10 nm) provide a confinement effect that limitsparticle nucleation, growth, and agglomeration.

Figure (5): Reverse micelle

Applications1. Nanomagnetism.

Figure (6): The general trend for most ferromagneticmaterials of coercivity as a function of particle size.

Figure (7): The balance of energies at hand indetermining the formation of single domain or multi-domain ferromagnetic particles.

1. Nanomagnetism.

1. Nanomagnetism.

Figure (8): (a)The coercivity of various anisotropic particleshapes as a function of aspect ratio, (b) A pictorialrepresentation of each anisotropic particle shape.

2. Targeted drug delivery.

Figure (9): Principle of targeted drug delivery system .

Because of their small sizes, nanoparticles are taken by cells wherelarge particles would be excluded or cleared from the body

1. A nanoparticle carries the pharmaceutical agent inside its core, while its shell is functionalized with a ‘binding’ agent.

2. Through the ‘binding’ agent, the ‘targeted’ nanoparticle recognizes the target cell. The functionalized nanoparticle shell interacts with the cell membrane.

3. The nanoparticle is ingested inside the cell, and interacts with the biomolecules inside the cell.

4. The nanoparticle particles breaks, and the pharmaceutical agent is released.

Figure (10): Targeteddrug delivery.

Healthy tissue Sick tissue treatedwith non-targeted

nanoparticles

Sick tissue treated with targeted nanoparticlesFigure (11): Example of a tissue treated by targeted drug delivery

system.

Laboratory research has established that nanoscale metalliciron is very effective in destroying a wide variety ofcommon contaminants. The basis for the reaction is thecorrosion of zero valent iron in the environment:

3. Zero valent iron for ground water remediation.

The use of nZVI for groundwater remediation represents, the most widely investigated environmental nanotechnological technique.

Two approaches to application of ZVI forGround water remediation:1. Granular ZVI in the form of reactive barriers has beenused for many years at numerous sites all over the worldfor the remediation of organic and inorganiccontaminants in groundwater as shown in figure a.

Figure (12):Conventional reactive barrier using granular ZVI.

2. With nZVI, two possible techniques are used:

A. Immobile nZVI is injected to form a zone of ironparticles adsorbed on the aquifer solids as shown infigure b.

Figure (13):Injection of nZVI to form an immobileReaction zone.

B. Mobile nZVI is injected to form a plume of reactive Fe particles that destroy any organic contaminants that dissolve from a DNAPL (dense non-aqueous phase liquid)source in the aquifer as shown in figure c.

Figure (14):Injection of mobile nZVI .

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