Luminescence of Rare-Earth-Doped Nanoparticles with Aromatic Linker Molecules

Rare-earth-doped vanadate glasses retain their luminescence when formed as shells around magnetic cores [1]. This property has prompted speculation that composite magneto-photoluminescent (CMPL) structures can be used in biological applications. For example, CMPL nanoparticles can be magnetically tuned to separate cells, proteins and nucleic acids [2]. A crucial step in realizing this goal is to attach organic linkers (between the rare-earth-doped shell and bio-probes), which do not affect the luminescence. We demonstrate with IR spectroscopy that Eu:YVO$_{4}$ nanoparticles treated with benzoic acid, 3-nitro 4-chloro-benzoic acid and 3,4-dimethoxy benzoic acid all result in the modification of the surface states, replacing the native metal-hydroxyl bond with a longer chain aromatic linker, which can be later functionalized. Photoluminescence spectra under UV-excitation show that the dominant $^{5}$D$_{0} \quad \to $ $^{7}$F$_{2}$ transition at $\sim $620 nm is unaffected by the chemical treatment. The result provides a platform to facilitate the attachment of bio-probes to Eu:YVO$_{4}$ nanoparticles and related CMPL nanostructures with Fe$_{2}$O$_{4}$ cores. \newline [1] N. B. McDowell et al, J. Appl. Phys. 107, 09B327 (2010). \newline [2] T. R. Sathe et al, Anal. Chem. 78, 5627 (2006).