Lam Thi Kieu Giang

Luminescence, energy transfer, and upconversion mechanisms of Y 2 O 3 nanomaterials doped with Eu 3+ , Tb 3+ , Tm 3+ , Er 3+ , and Yb 3+ Ions

Luminescence, energy transfer, and upconversion mechanisms of nanophosphors (Y2O3:Eu3+, Tb3+, Y2O3:Tm3+, Y2O3:Er3+, Yb3+) both in particle and colloidal forms were studied. The structure, phase, and morphology of the nanopowders and nanocolloidal media were determined by high-resolution TEM and X-ray diffraction. It was shown that the obtained nanoparticles have a round-spherical shape with average size in the range of 4 to 20nm. Energy transfer was observed for Y2O3:Eu3+, Tb3+ colloidal and powders, upconversion transitions were observed for both Y2O3:Er3+ and Y2O3:Er3+, Yb3+ nanophosphors. The dependence of photoluminescence (PL) spectra and decay times on doping concentration has been investigated. The infrared to visible conversion of emission in Y2O3:Er3+, Yb3+ system was analyzed and discussed aiming to be applied in the photonic technology.

Surface modification of iron oxide nanoparticles and their conjuntion with water soluble polymers for biomedical application

Superparamagnetic iron oxide nanoparticles (SPION) coated with suitable bio-compatible substances have been used in biomedicine, particularly in magnetic resonance imaging (MRI), tissue engineering, and hyperthermia and drug delivery. In this study, we describe the synthesis of SPION and its surface modification for in-vitro experiments. The particle diameter and structure were estimated by FESEM, TEM, XRD analyses. The saturation magnetization was characterized. SPION with a mean size of 12 nm have been prepared under N2 atmosphere, with support of natural polymeric starch, by controlling chemical coprecipitation of magnetite phase from aqueous solutions containing suitable salts ratios of Fe2+ and Fe3+. The surface of SPION-nanoparticles was treated with a coordinatable agent for higher dispersion ability in water and remaining the superparamagnetic behavior. The prepared iron oxide nanoparticles were coated with starch, dextran, PEG or MPEG to extend the application potential in the quite different engineering field of nano biomedicine.

Fabrication and upconversion emission processes in nanoluminophores NaYF4: Er, Yb and NaYF4: Tm, Yb

In this paper we present the new results of fabrication, characterisation and upconversion emission process of NaYF4 nanoparticles doped with Er3+ or Tm3+and Yb3+ as sensitiser. In order to fabricate α–, β–NaYF4:2%Er3+, 19%Yb3+and α–, β–NaYF4:2%Tm3+, 19%Yb3+ nanoparticles the soft template method in isopropylamine at 140C and diethylene glycol (DEG) at 180C has been used. The morphology, structures and emission properties were studied by X–ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and luminescence spectroscopy. The upconversion luminescence (UCL) spectra of α and β crystalline forms of NaYF4:2%Er3+, 19%Yb3+and NaYF4:2%Tm3+, 19%Yb3+ nanoparticles were investigated upon diode laser excitation at 976 nm. The strong emissions in the green and red spectral regions were observed upon this excitation. The spectral lines of the UCL could be assigned to the upconversion radiative transitions of the Er3+ or Tm3+ ions with Yb3+ sensitiser. The upconversion emission spectra dependent on laser excitation powers have been investigated in order to elucidate the upconversion emission paths which could take place. We found the significant influence of the type of nanocrystalline structure on the upconverting radiative transition mechanisms in NaYF4:2%Er3+, 19%Yb3+and NaYF4:2%Tm3+, 19%Yb3+ nanoparticles.

Study on preparation and properties of a novel photo–catalytic material based on copper–centred metal–organic frameworks (Cu–MOF) and titanium dioxide

A Cu3BTC2 metal–organic framework (MOF) with large specific surface area of 1350 m2/g, where BTC = benzene–1,3,5–tricarboxylate, was synthesised by hydrothermal method. It was then used as a starting material for the preparation of a novel MOF based photocatalyst containing titanium dioxide. This photocatalyst, namely, TiO2@Cu3BTC2, has been prepared by hydrolysis of titanium (IV) isopropoxide under hydrothermal condition. The synthesised materials were then characterised by X–ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) techniques. The photocatalytic discolouration of methylene blue dye (MB) in aqueous solution was investigated under UV–VIS light irradiation at different illumination times using the photocatalyst TiO2@Cu3BTC2 metal–organic frameworks and a control sample of commercial TiO2 nano powder (Degussa P25). It is interesting to note that TiO2@Cu3BTC2 exhibits very strong photocatalytic activity for MB discolouration, much better than lone TiO2 nano–particles P25. Thus, this novel photocatalytic material based on copper–centred MOFs may serve as an excellent class of photocatalytic materials for different environmental applications.

Preparation and optical properties of one dimensional nano hydroxides and oxides

The Yttrium hydroxide nanotubes and nanorods as well as the ZnO nanorods and nanowires were prepared by different methods. Y(OH)3 nanotubes and nanorods were synthesized by polyol — mediation via the metastable precursor YCl3, PEG and were studied by FE SEM and XRD. The influence of the polymer molecular weights of PEG and the temperature were studied in detail. These results show that the first stage is nanorods, then it is followed by the formation of nanotubes. The outer diameter of the tubes is about 150 nm to 600 nm and interior hollow is in the range between 100 nm to 300 nm. The length of the rods and the tubes is up to several micrometers. We have found that the synthesis temperature, reaction rate and molecular weight of PEG induce the change in shape of obtained nanotubes from a cylindrical to a hexagonal appearance. The growth process of the nanotubes may be performed through three stages: first complexing the PEG polymer with Y(NO3)3, then hydrolysis for formating Y(OH)3 nanorods and finally diffusion-controlled developing of Y(OH)3 nanotubes. The ZnO nanorods were prepared by Chemical Vapor Deposition (CVD) and Metal Organic Chemical Vapor Deposition (MOCVD) method, respectively. Aligned growth of ZnO nanorods has been successfully prepared. The nanorods have the diameters of about 50 nm and the length of about 1.12 micrometers. The influence of the temperature is investigated. The luminescent spectra (excited by Cd-He laser at 325 nm) of ZnO nanorods at 10 K- 300 K was measured and investigated. The sharp peak is assigned to an exciton bound to a neutral donor.

Preparation, optical properties of ZnO, ZnO:Al nanorods and Y(OH)3:Eu nanotube

ZnO, ZnO:Al nanorods and Y(OH)3 nanotubes have been prepared by the chemical vapor deposition and liquid phase synthesis. ZnO nanorods with diameter of 50 ? 100 nm and length of 5 ?m have been obtained by the CVD method. ZnO:Al nanorods were synthesized by the hydrothermal method from ZnSO4. and Al2(SO4)3. Nanorods and nanotubes of Y(OH)3 with diameter of 200 nm and length of several micrometers were prepared by the soft template method. The crystal structure and morphology of rods and tubes were analyzed by the X-Ray diffraction and FE-SEM. The influence of fabrication conditions and Al, Eu concentration have been discussed.

Nanosciences and Nanotechnology of Vietnamese Women: Fabrication, Characterization, and Application of Rare Earth Nanocompounds for Photonics

Nanorods Y(OH)3:Eu, nanotubes Tb (OH)3, and nanocomposites silica‐titania‐ and silica‐zirconia‐doped erbium and ytterbium were prepared by liquid‐phase methods. Structures and photonic properties such as long decay time (7.4 ms) and waveguide loss were studied in detail in the concentration and temperature dependence. The application of the nanocomposites for planar waveguide systems is presented.

Preparation, characterization and optical properties of ZrO2:Er3+, Yb3+ nanomaterials

Luminescent nanomaterials from lanthanide are one of most promising materials for applications in medical diagnostics. In this paper, we present for the first time the ZrO2 nanomaterials with capsule like nanostructure with the sizes of 150 nm in length and 50 nm in width. These nanocapsule like ZrO2 doped with Er3+, Yb3+ ions were prepared by soft template methods. Morphological characterization of nano – ZrO2:Er3+, Yb3+ was performed by using FESEM, X-ray diffraction, micro Raman. Up conversion luminescence and photoluminescence have been also studied with IR-laser excitation at 940 nm and UV excitation at 365 nm.