Iron nanoparticle
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Nanoscale iron particles are sub-micrometer particles of iron metal. Due to their high catalytic activity, permanent magnetic properties, low toxicity, and strong adsorption capacity, iron-based nanoparticles are widely utilized in drug delivery, production of magnetic tapes (e.g., camcorders and backup tapes of computers), gene therapy, and environmental remediation.
Synthesis
Iron nanoparticles can be synthesized using two primary approaches: top-down and bottom-up methods.
Top-down Methods
Top-down approaches create nanoparticles by breaking down larger bulk materials into smaller particles, including laser ablation and mechanical grinding.
Bottom-up Methods
Bottom-up approaches involve the chemical and biological synthesis of iron nanoparticles from metal precursors (e.g., Fe(II) and Fe(III)). This method is widely regarded as the most effective and commonly used strategy for nanoparticle preparation. For example, iron nanoparticles can be chemically prepared by reducing Fe(II) or Fe(III) salts with sodium borohydride in an aqueous medium. This process can be described by the following equations:
- 4 Fe3+ + 3 BH4− + 9 H2O → 4 Fe0↓ + 12 H+ + 6 H2 + 3 H2BO− (1)
- 4 Fe2+ + 3 BH4− + 9 H2O → 4 Fe0↓ + 8 H+ + 8 H2 + 3 H2BO− (2)
Properties
Iron nanoparticles are prone to oxidation when exposed to air and water. This redox process can occur under both acidic and neutral/basic conditions:
- 2 Fe0 + 4 H+ + O2 → 2 Fe2+ + 2 H2O (3)
- Fe0 + 2 H2O → Fe2+ + H2 + 2 OH− (4)
Application in Environmental Remediation
Research has shown that nanoscale iron particles can be effectively used to treat several forms of ground contamination, including grounds contaminated by polychlorinated biphenyls (PCBs), chlorinated organic solvents, and organochlorine pesticides. Nanoscale iron particles are easily transportable through ground water, allowing for in situ treatment. Additionally, the nanoparticle-water slurry can be injected into the contaminated area and stay there for long periods of time. These factors combine to make this method cheaper than the most currently used alternative.
Researchers have found that although metallic iron nanoparticles remediate contaminants well, they tend to agglomerate on the soil surfaces. In response, carbon nanoparticles and water-soluble polyelectrolytes have been used as supports for the metallic iron nanoparticles. The hydrophobic contaminants adsorb to these supports, improving permeability in sand and soil.
In field tests have generally confirmed lab findings. However, research is still ongoing and nanoscale iron particles are not yet commonly used for treating ground contamination.
Application in Biomedicine
Iron oxide nanoparticles (IONPs) have widespread applications in biomedicine, including their use in magnetic resonance imaging and cancer therapy via magnetic hyperthermia
In addition to these applications, IONPs exhibit strong antibacterial activity and have been explored for drug and viral vector delivery to target cells. Known microorganisms susceptible to the toxic effects of IONPs include Gram-negative bacteria (e.g., Escherichia coli and Klebsiella sp.) and Gram-positive bacteria (e.g., Bacillus sp. and Corynebacterium sp.) .
The antibacterial activity of IONPs is primarily attributed to the generation of reactive oxygen species (ROS), a mechanism similar to the Fenton reaction. Specifically, Fe2+ ions react with hydrogen peroxide (H2O2), producing Fe3+ ions and hydroxyl radicals. These highly reactive species induce oxidative damage to bacterial DNA, ultimately leading to cell death.