Hexanedioic acid mediated surface―ligand-exchange process for transferring NaYF4:Yb/Er (or Yb/Tm) up-converting nanoparticles from hydrophobic to hydrophilic

• Published in: Journal of colloid and interface science 2009-08, Vol.336 (1), p.171-175
• Main Authors: Zhang, Qingbin, Song, Kai, Zhao, Junwei, Kong, Xianggui, Sun, Yajuan, Liu, Xiaomin, Zhang, Youlin, Zeng, Qinghui, Zhang, Hong
• Format: Article
• Language: English
• Subjects: Adipates - chemistry; Avidin - chemistry; Avidin - metabolism; Chemistry; Colloidal state and disperse state; Erbium - chemistry; Ethylene Glycols - chemistry; Exact sciences and technology; Fluorides - chemistry; General and physical chemistry; Hydrophobic and Hydrophilic Interactions; Ligands; Microscopy, Fluorescence; Nanoparticles - chemistry; Nanoparticles - ultrastructure; Nanotechnology - methods; Particle Size; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Protein Binding; Surface physical chemistry; Surface Properties; Thulium - chemistry; Water - chemistry; Ytterbium - chemistry; Yttrium - chemistry
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2009.04.024

Water-soluble and carboxyl-functionalized up-converting rare-earth nanoparticles (UCNPs) are obtained via an efficient surface-ligand-exchange procedure. Hexanedioic acid molecules are employed to replace the original hydrophobic ligands in diethylene glycol solvent at high temperature. Various characterizations indicate the ligand-exchange process has negligible adverse effect on the quality of the UCNPs. The resulting hydrophilic UCNPs show small size, strong up-converting emission and high water stability. The specific molecular recognition capacity of avidin-modified hydrophilic UCNPs confirms that hydrophilic UCNPs are suitable for potential biological labeling.