A General Strategy for Ligand Exchange on Upconversion Nanoparticles

Abstract

Lanthanide-doped upconversion nanoparticles with a suitable surface coating are appealing for biomedical applications. Because high-quality upconversion nanoparticles are typically prepared in an organic solvent and passivated by hydrophobic oleate ligands, a convenient and reliable method for the surface modification of upconversion nanoparticles is thus highly desired to satisfy downstream biological investigations. In this work, we describe a facile and versatile strategy for displacing native oleate ligands on upconversion nanoparticles with a diversity of hydrophilic molecules. The ligand-exchange procedure involves the removal of original oleate ligands followed by the attachment of new ligands in a separate step. The successful coating of relevant ligands was confirmed by Fourier transform infrared spectroscopy, thermogravimetry analysis, and ζ-potential measurement. The surface-modified nanoparticles display high stability and good biocompatibility, as revealed by electron microscopy, photoluminescence spectroscopy, and cytotoxicity assessment. Our study demonstrates that functional biomolecules such as biotin can be directly immobilized on the nanoparticle surface using this approach for the quick and effective detection of streptavidin.

Long‐Term Colloidal and Chemical Stability in Aqueous Media of NaYF4‐Type Upconversion Nanoparticles Modified by Ligand‐Exchange

“…The oleate can also be stripped off by an alternative method, where the particle dispersion is treated by an acid, most likely HCl . Thereby the hydrophobic oleate capped UCNPs need to be dispersed in an acidic aqueous system for 2 h (Figure S9, Supporting Information).…”

An All-Nanocrystal Biosensing System for In Vitro Detection of STAT3 Oligonucleotides

“…To functionalize the lanthanide-doped nanocrystals, oleyamine/oleate ligands capped on the as-synthesized nanocrystals were first exchanged with poly (acrylic acid) (PAA) molecules using a general strategy developed by our group [ 24 ]. In brief, this ligand exchange procedure comprises two steps; i.e., removal of origin hydrophobic ligands by ultra-sonication in hydrochloric acid solution and anchoring of PAA molecules onto the surface of the ligand-free nanocrystals through solvothermal treatment in diethylene glycol ( Figure 4 a).…”

Controllable Synthesis of Upconversion Nanophosphors toward Scale‐Up Productions

“…Generally, ion exchange is used in nanoparticle surface ligand modification of UCNPs for a hydrophilic surface [ 95,96 ] and in the epitaxial shell growth process. [ 97 ] However, recently this method was found to be used in the synthesis of UCNPs core particles such as NaYF 4 , NaGdF 4 , NaErF 4 , and Na 3 ZrF 7 .…”