| Rare earth luminescent nanomaterials have the fluorescence properties of sharp emission profiles, long fluorescence lifetime, high photochemical stability, large effective stokes shifts, and can emit lights with various colors by an appropriate choice of the doping ions or the host-activator systems under single-wavelength excitation. They have great potential applications in the fields of high performance luminescent devices, solar cells and laser materials, especially in protein or DNA assays, biolabeling and optical imaging, diagnostics, etc. In this paper, the luminescent nanometerials with different properties were synthesized through choosing orthophosphates, fluorides and molybdates as host, using Eu3+, Tb3+, Sm3+, Dy3+as the doped ions. X-ray diffraction (XRD), scan electronic microscope (SEM), transmission electronic microscope (TEM), photoluminescence spectroscopy (PL), flourier transforms infrared spectroscopy (FT-IR) and thermal gravimetric-differential scanning calorimetry (TG-DSC) were used to characterize the sysnthsized nanomaterial samples and then the as prepared La2(MoO4)3:Eu3+nanocrystals were used in immuno-imagings of HeLa cells. The main contents are outlined as below:1. GdPO4:Eu3+ and GdPO4:Ce3+, Tb3+ nanocrystals were synthesized via the polyol method in glycol media. The obtained nanocrystals were of pure monoclinic phases (monazite type) orthophosphates and the morphology was nanospindles with long axis size of 600～700 nm and the short axis size of 50～200nm. The as-prepared nanocrystals could be well-dispersed in water to form a clear colloidal solution. The colloidal solution of GdPO4:Eu3+ showed the characteristic emission of Eu3+, with the magnetic-dipole transition 5D0-7F1 (592 nm) being the most prominent peak. The excitation spectrum of GdPO4:Ce3+,Tb3+ showed a broad band ranging from 240～300 nm with a maximum at 262 nm, which was ascribed to 4f-5d transition of Ce3+, meanwhile the emission spectrum exhibited characteristic green emission of Tb3+ with the strongest peak locate at 544 nm. The sensitizing mechanism for the luminescence of GdPO4:Ce3+,Tb3+ was discussed and the energy transfer from Ce3+ via Gd3+ to Tb3+ ions was observed in the nanocrystals. The structure and morphology of (Y1-xGdx)PO4:Eu3+0.05 nanocrystals can be adjusted through changing the molar ratios of Gd3+ and Y3+ ions in the host, so that multicolor nanocrystals can be obtained.2. By doping of Ce3+ ion which is the most efficient sensitizer of Tb3+, CePO4:Tb3+ nanospindles were synthesized via a polyol method in glycol media. The results showed that the as-prepared CePO4:Tb3+ was monoclinic orthophosphate with a size of 70-100 nm in length and 30-40 nm in width. The excitation spectra of CePO4:Tb3+ exhibited a broad band around 263.5 nm and two narrow bands at about 371.5 and 485.5 nm. Under 263.5 or 371.5 nm excitation, the prepared CePO4:Tb3+ nanospindles showed the characteristic emission of Tb3+ 5D4-7FJ (J=6-3) transitions, with 5D4-7F5 green emission at 544 nm as the strongest one. Furthermore, these nancrystals were coated with SiO2 by a modified Stober process, for making it to be biocompatible,3. YF3:Eu3+and YF3:Tb3+ nanocrystals were synthesized by an improved polyol method using PVP as stabilizer in glycol media. The as-prepared nanocrystals consists of well crystallized orthorhombic phase and have a short rod-like shape with 40-60 nm in longth and 20-30 nm in width. Under near UV excitation, these nancrystals showed characteristic emissions of Eu3+ or Tb3+ ions. The luminescence of YF3:Eu3+ was dominated by 5Do-7F1 transition. In addition, spherical YF3:Eu3+ nanoparticles were synthesized using a simple and effective room-temperature co-precipitation process assisted by a chelating agent, citric acid (Cit). The nanocrystals with controllable diameters from 50 to 150 nm can be obtained by adjusting the molar ratio of Cit3-/Y3+ Under 391 nm excitation, YF3:Eu3+(5mol %) exhibited strong characteristic 5D0-7F1 and 5D0-7F2 transitions emission of Eu3+, with 5D0-7F2 transition is the strongest. It was found that the sizes of the nanoparticles were markedly affected by the molar ratio of Cit3-/Y3+. Both the two kinds of nanocrystals have good water solubility, leading them could be used as potential effective probes in biological detection.4. Lanthanide ion-pairs (Eu3+/Tb3+, Dy3+/Tb3+, Sm3+/Tb3+, and Eu3+/Dy3+) codoped NaGdF4 nanocrystals were prepared via polyol method using Ce3+ as the sensitizer. The nanocrystals with different codoped lanthanide ion-pairs retain their individual optical properties and can be detected complex spectra using single-wavelength excitation at about 251 nm. The intensity ratios in complex spectra can be adjusted through control of the doping ions molar ratios. Excited with UV lamp at 254 nm, the as-prepared nanocrystals in aqueous solution emit intense visible emissions of different colors. The nanocrystals were coated with SiO2 through a modified Stobe process, for making it convenient to conjugate with biomolecules, which provide a new chance in simultaneous multicolor detection in bioassay.5. To fulfil the demand of live cells labeling or biologic body, europium doped nanoparicles by using of molybdate as host ware studied. ZnMoO4:Eu3+ nanocrystals were synthesized by a hydrothermal method using EDTA as chelating agent. The obtained nanocrystals are the quasi-quadrangular nanoflakes in shape with a size of about 300-500 nm in length and 100 nm in width. Under 392.5 nm excitation, asprepared ZnMoO4: Eu3+ nanocrystals showed the characteristic emission of Eu3+, with 5Do-7F2 red emission at 615 nm as the strongest. A solvthemal strategy for the synthesis of La2(MoO4)3:Eu3+ nanocrystals is presented using rare-earth stearate as precursor, oleic acid/oleylamine and tetraoctylammonium bromide as stabilizer in isopropanol and water media. Spherical La2(MoO4)3:Eu3+ nanocrystals with a diameter of about 25 nm was obtained, with the same luminescencet properties. After coating with SiO2, the La2(MoO4)3:Eu3+ nanocrystals were successfully used to label HeLa cells through the immunoreaction between antibody and CEA antigens, expressed on HeLa cells membrane. |
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