Simple Ligand Exchange Reactions Enabling Excellent Dispersibility and Stability of Magnetic Nanoparticles in Polar Organic, Aromatic, and Protic Solvents

详细信息    查看全文

• 作者：Xinyu Wang ; Richard D. Tilley ; James J. Watkins
• 刊名：Langmuir
• 出版年：2014
• 出版时间：February 18, 2014
• 年：2014
• 卷：30
• 期：6
• 页码：1514-1521
• 全文大小：447K
• ISSN：1520-5827

文摘

The use of magnetic nanoparticles (MNPs) in real-world applications is often limited by the lack of stable solutions of monodisperse NPs in appropriate solvents. We report a facile one-pot ligand exchange reaction that is fast, efficient, and thorough for the synthesis of hydrophilic MNPs that are readily dispersed in polar organic and protic solvents (polarity index = 3.9鈥?.2) including alcohols, THF, DMF, and DMSO for years without precipitation. We emphasize the rational selection of small-molecule ligands such as 4-hydroxybenzoic acid (HBA), 3-(4-hydroxyphenyl)propionic acid (HPP), and gallic acid (GAL) that provide strong bonding with the MNP (FePt and FeO_x) surfaces, hydrophilic termini to match the polarity of target solvents, and offer the potential for hydrogen-bonding interactions to facilitate incorporation into polymers and other media. Areal ligand densities (危) calculated based on the NP core size from transmission electron microscopy (TEM) images, and the inorganic fractions of NPs derived from thermogravimetric analysis (TGA) indicated a significant (2鈥? times) increase in the ligand coverage after the exchange reactions. Fourier transform infrared spectrometry (FTIR) and ¹H nuclear magnetic resonance (NMR) studies also confirmed anchoring of carboxyl groups on NP surfaces. In addition, we demonstrate a facile one-step in situ synthesis of FePt NPs with aromatic ligands for better dispersibility in solvents of intermediate polarity (polarity index = 1.0鈥?.5) such as toluene, chlorobenzene, and dichloromethane. The creation of stable dispersions of NPs in solvents across the polarity spectrum opens up new applications and new processing widows for creating NP composites in a variety of host materials.