Magnetic Iron Oxide (Magnetite) Nanoparticles

Magnetic Iron Oxide Nanoparticle Properties

nanoComposix magnetic iron oxide nanoparticles are approximately 20 nm in diameter. Current materials are designed as discrete, well-controlled particles rather than large agglomerates, helping preserve nanoscale surface area and consistent dispersion behavior.

Superparamagnetic Behavior

At sufficiently small particle dimensions, magnetite nanoparticles can exhibit superparamagnetic behavior. The particles respond strongly to an applied magnetic field but have little persistent magnetization after the external field is removed. This behavior is useful when particles need to be magnetically manipulated or concentrated while remaining dispersible after magnetic exposure.

Observed magnetic responsiveness depends on more than nominal particle diameter. Core composition, magnetic domain structure, particle concentration, aggregation state, applied field strength, and field gradient can all affect how rapidly a material responds in a particular workflow.

Surface Chemistry & Formulation

Current 20 nm iron oxide materials are available with different surfaces depending on the intended application:

• Carboxyl: Provides a reactive surface for covalent conjugation of antibodies, proteins, peptides, oligonucleotides, and other amine-containing molecules.
• Streptavidin: Supports high-affinity attachment of biotin-labeled biomolecules.
• Oleic acid: Provides compatibility with nonpolar organic solvents and is currently supplied in toluene.

Because each surface chemistry requires a different stabilization strategy, solvent and buffer composition vary by product. Refer to the current Magnetic Particles collection and individual product pages for formulation-specific details.

Applications of Magnetic Iron Oxide Nanoparticles

Magnetic Separation & Biosensing

Magnetic nanoparticles can be manipulated using an external magnetic field, providing a way to concentrate, capture, or separate particle-bound targets from a sample. Surface-functionalized particles can combine this magnetic response with antibodies, proteins, oligonucleotides, or other recognition molecules.

These properties make magnetic iron oxide useful for biosensing, biomolecular capture, enrichment, and other separation-based research workflows. For diagnostic applications and conjugation strategies, see Nanoparticles for Precision Diagnostics.

Biomedical & Magnetic-Responsive Research

Iron oxide nanoparticles have been extensively studied in areas including MRI contrast research, magnetically responsive delivery systems, magnetic hyperthermia, and multimodal nanoparticle platforms. Performance in these applications depends strongly on particle size, magnetic properties, surface chemistry, dose, and the surrounding biological environment.

For nanoparticle formulation and translational development programs, see Nanomedicine CDMO Services.

Ferrofluids, Catalysis & Materials Research

Well-dispersed magnetic nanocrystals can also be incorporated into ferrofluids, polymer systems, composite materials, and catalytic platforms. Surface chemistry and solvent compatibility become especially important when transferring particles between aqueous and organic environments or integrating them into a bulk material.

Nanotoxicology & Comparative Studies

Precisely characterized iron oxide nanoparticles can support studies investigating how particle size, surface chemistry, aggregation state, concentration, and magnetic properties affect biological or environmental behavior.

Biological response should be evaluated for the specific particle formulation and exposure conditions rather than assuming magnetite is universally non-toxic. See Nanotoxicology: Particle Selection for additional experimental considerations.

Frequently Asked Questions

Custom Magnetic Nanomaterials

nanoComposix has developed magnetic nanomaterials with a range of compositions, sizes, morphologies, surface chemistries, and composite architectures. Custom development can combine magnetic response with optical, fluorescent, catalytic, or biomolecular functionality based on application requirements.

Magnetic-Plasmonic Gold Nanoshells

Magnetic gold nanoshells combine a superparamagnetic core with a dielectric spacer and an outer gold shell. This architecture provides both magnetic responsiveness and the tunable plasmonic optical properties of a gold nanoshell.

Particle dimensions and gold-shell thickness can be adjusted to modify the optical response, while the gold surface provides a useful interface for further functionalization with biomolecules or other ligands. Custom reaction conditions have been used to produce magnetic nanoshell structures with overall dimensions ranging from approximately 100–300 nm.

A 200 nm carboxyl-functionalized magnetic gold nanoshell is also part of the current conjugation portfolio, combining a superparamagnetic core with a plasmonic gold surface for magnetic manipulation and optical detection. :contentReference[oaicite:1]{index=1}

Magnetic-Fluorescent Nanoparticles

nanoComposix has also fabricated magnetic-fluorescent composite particles consisting of a magnetic iron oxide core, a silica spacer, and fluorescent quantum dots covalently attached to the silica surface. The quantum-dot surface can be further modified to support attachment of biomolecules or other functional molecules.

In one example, approximately 60 nm iron oxide particles were coated with uniform silica shells and functionalized with quantum dots to produce a final particle diameter of approximately 100 nm. Core size, shell thickness, and fluorescent component can be adjusted to modify the resulting magnetic and optical properties.

Custom Iron Oxide Nanoparticles

Highly monodisperse magnetic nanocrystals can be produced through thermal decomposition of organometallic precursors in organic solvents. This approach supports precise control over nanocrystal size and produces particles compatible with nonpolar organic environments.

Oleic-acid-coated iron oxide particles have been produced from approximately 4–20 nm in diameter by adjusting reaction conditions. Surface modification or growth of a silica shell can subsequently be used to transfer these materials into aqueous-compatible environments or introduce additional functionality.

Iron-Platinum Nanoparticles

Magnetic alloy nanoparticles provide another route to tune magnetic, catalytic, and materials properties through composition as well as particle size. nanoComposix has fabricated iron-platinum (FePt) nanoparticles with adjustable iron-to-platinum ratios and particle dimensions.

The example below shows monodisperse FePt nanoparticles with diameters of approximately 3 nm.