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Abstract: Polyethyleneimine (PEI) functionalized multicolor luminescent LaF3 nanoparticles were synthesized via a novel microwave-assisted method, which can achieve fast and uniform heating under eco-friendly and energy efficient conditions. The as-prepared nanoparticles possess a pure hexagonal structure with an average size of about 12nm. When doped with different ions (Tb3+ and Eu3+), the morphology and structure of the nanoparticles were not changed, whereas the optical properties varied with doped ions and their molar ratio, and as a result emission of four different colors (green, yellow, orange and red) were achieved by simply switching the types of doping ions (Eu3+ versus Tb3 +) and the molar ratio of the two doping ions. [Copyright &y& Elsevier]

Abstract: Up-conversion nanoparticles (UCNPs), which can convert a longer wavelength radiation to a shorter wavelength radiation, have great potential use as bio-labels in biological detection. However, these NPs usually cannot be used directly unless their surface is further modified. Herein, we developed a novel and straightforward method for the synthesis of monodisperse NaYF4:Yb,Er/Polymer UCNPs. The resultant UCNPs exhibited a pure hexagonal phase, strong UC fluorescent intensity, and a uniform size of about 40nm, which were characterized by XRD, luminescence spectroscopy and TEM, respectively. FT-IR spectra revealed that these NPs were coated with a layer of hydrophilic polymers (including PVP, PEG, PAA and PEI), thus the NPs could be dispersed in water easily. More importantly, the PAA and PEI coated NPs were functionalized by –COOH and –NH2 groups, respectively, which were expected to be used for further bio-conjugation. [Copyright &y& Elsevier]