title: Enhanced upconversion luminescence in NaGdF4:Yb,Er nanocrystals by Fe3+ doping and their application in bioimaging.
abstract: The visible green and red upconversion emissions in Er(3+)/Yb(3+) doped β-NaGdF4 nanoparticles were enhanced by tridoping with Fe(3+) ions (0-40 mol%). XRD, XPS, ICP-AES and EDS data demonstrated successful incorporation of Fe(3+) ions in NaGdF4:Yb(3+)/Er(3+) nanoparticles. The effect of Fe(3+) tridoping on the upconversion luminescence in NaGdF4:Yb(3+)/Er(3+) NPs was investigated in detail. The green and red emission intensities were enhanced by 34 and 30 times, respectively. The maximum emission was observed in a sample containing 30 mol% Fe(3+) ions. A possible mechanism for the enhanced upconversion emission is proposed. In addition, a layer of silica was coated onto the surface of UCNPs to improve the biocompatibility. Folic acid was covalently linked to the silica coated UCNPs to form UCNP@SiO2-FA nanoprobes, which have been successfully applied to the fluorescent imaging HeLa cells.
authors.affiliation: Department of Chemistry and GETRC, Kongju National University, 182, Shinkwondong, Kongju, 314-701, Chungnam-do, Republic of Korea.
authors.forename: Parthiban
authors.initials: P
authors.lastname: Ramasamy
authors.forename: Prakash
authors.initials: P
authors.lastname: Chandra
authors.forename: Seog Woo
authors.initials: SW
authors.lastname: Rhee
authors.forename: Jinkwon
authors.initials: J
authors.lastname: Kim
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D004871:Erbium / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry; D005459:Fluorides / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000633:toxicity; D018613:Microscopy, Confocal; D015018:Ytterbium / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D005456:Fluorescent Dyes; D004871:Erbium; D005682:Gadolinium; D015018:Ytterbium; D005459:Fluorides