title: In-situ polymerization approach for preparation of rare earth fluoride phosphors coated with PAA.
abstract: Up-conversion nanoparticles (UCNPs), which can convert a radiation from a longer wavelength to a shorter wavelength, have great potential uses as bio-labels in biological detection. However, these NPs usually cannot be used directly unless their surfaces are further modified. In this paper, NaYF4:Yb, Er nanoparticles (NPs) were coated with poly(acrylic acid) (PAA) by in situ polymerization for the first time. Accordingly, NaYF4:Yb, Er/NaYF4 NPs were synthesized before PAA coating to avoid the decay of optical intensity. The resulting UCNPs were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and up-conversion photoluminescence spectrometry. The XRD results indicated that the resultant UCNPs exhibited a pure hexagonal phase. The FT-IR spectra and TGA curves revealed that these NPs were coated successfully with PAA. Meanwhile, the TEM results showed that well-dispersed UCNPs with the best morphology and an average size of about 90 nm were obtained with 8.0 wt% acrylic acid content (the content percentage in the whole reaction system) at 0 degrees C within 130 min. Fluorescence tests showed that the UCNPs had a strong UC fluorescence intensity. Settlement tests revealed that PAA-coated NaYF4 UCNPs had more favorable dispersion stability than uncoated UCNPs in an aqueous system. These functionalized nanocomposites could be used for further bio-conjugation.
authors.affiliation: College of Material Science and Engineering, Donghua University, Shanghai 201620, P. R. China.
authors.forename: Xie
authors.initials: X
authors.lastname: Li
authors.forename: Xingping
authors.initials: X
authors.lastname: Zhou
authors.forename: Xiaqin
authors.initials: X
authors.lastname: Wang
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D004871:Erbium / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008674:Metals, Rare Earth / Q000737:chemistry*; D010316:Particle Size; D017550:Spectroscopy, Fourier Transform Infrared; D013818:Thermogravimetry; D014961:X-Ray Diffraction; D015018:Ytterbium / Q000737:chemistry; D015019:Yttrium / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D005456:Fluorescent Dyes; D008674:Metals, Rare Earth; C525362:sodium yttriumtetrafluoride; C006903:carbopol 940; D015019:Yttrium; D004871:Erbium; D015018:Ytterbium; D005459:Fluorides