Experimental and first-principles characterization of functionalized magnetic nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Magnetic iron oxide nanoparticles (IONPs) are crucial in various applications.
• Controlling nanoparticle size and surface chemistry is vital for their performance.
• Understanding the interaction between IONPs and surfactants is essential for tailored applications.

Purpose of the Study:

• To synthesize and characterize magnetic IONPs using coprecipitation and thermal decomposition methods.
• To investigate the surface coating of oleic acid (OA) on these nanoparticles.
• To elucidate the bonding mechanisms and stability of OA on IONPs using computational methods.

Main Methods:

• Synthesis of IONPs via coprecipitation and thermal decomposition.
• Characterization using X-ray diffraction (XRD) and transmission electron microscopy (TEM) for size and structure.
• Fourier transform infrared (FTIR) spectroscopy to analyze OA coating.
• Differential thermal analysis (DTA) to study thermal decomposition of OA.
• Density functional theory (DFT) calculations for bonding analysis.

Main Results:

• Monodisperse IONPs with sizes 8-15 nm were produced.
• Coprecipitated particles were magnetite-rich, thermally decomposed particles were maghemite-rich, with both methods yielding mixtures.
• FTIR confirmed at least two layers of OA, with evidence of chemical and physical adsorption.
• DTA showed distinct weight loss steps attributed to OA condensation.
• DFT calculations revealed varying strengths of OA bonding to iron atoms, with ferric/ferric complexes showing higher stability.

Conclusions:

• Both coprecipitation and thermal decomposition are effective for synthesizing size-controlled magnetic IONPs.
• Oleic acid forms a multi-layered coating on IONPs, involving both chemisorption and physisorption.
• Computational analysis provides a deeper understanding of the OA-IONP interface, crucial for applications in catalysis, drug delivery, and magnetic storage.