Surface modification of hydrophobic nanocrystals using short-chain carboxylic acids

Acrylic, acetic and methacrylic acids which are short-chain carboxylic acids have been applied to modify the surface of oleic acid-coated TiO2 nanorods (NRs) and oleic acid/oleylamine-coated Fe3O4 nanoparticles (NPs). The short-chain carboxylic acids not only acted as modifying ligands but also as anti-solvents during the ligand exchange processes. The prepared products have been characterized using TEM, HRTEM and FTIR spectroscopy. The results Show that the acrylic acid-exchanged TiO2 and Fe3O4 Solution remain stable even after six months, showing no agglomeration. Such acrylic acid-exchanged nanocrystals (NCs) prepared in this work could also be well-dispersed in other polar solvents Such as ethanol and ethanol/water Mixtures. On the contrary acetic acid and methacrylic acid-exchanged TiO2 solutions were not stable due to the presence of remaining oleic acid on the TiO2 surface. This approach has been shown to be effective in making hydrophilic TiO2 NRs and Fe3O4 NPs and can also be applied to other NCs covered by different hydrophobic ligands. (C) 2009 Elsevier Inc. All rights reserved.