Ramzi Maalej

Thermal stability and UV–Vis-NIR spectroscopy of a new erbium-doped fluorotellurite glass

A new transparent bulk glass from the system 76TeO2 · 10ZnO · 9.0PbO · 1.0PbF2 · 3.0Na2O doped with Er3+ (TZPPN doped with Er3+) has been prepared using the conventional melt-quenching method. Results of differential thermal analysis (DTA) measurements indicate good thermal stability of this glass. The refractive indices at different wavelengths, the optical energy gap, the Sellmeier gap energy and the dispersion energy have been estimated. The Judd–Ofelt parameters, Ω t (t = 2, 4, 6) of Er3+ were evaluated from optical absorption spectra. Electric dipole, magnetic dipole type transition probabilities, spectroscopic quality factors, branching ratio and radiative lifetimes of several excited states of Er3+ have been predicted using intensity Judd–Ofelt parameters. The spectroscopic properties indicate that TZPPN glass doped with Er3+ is a promising candidate for laser applications and may be suitable for upconversion fibre optical devices.

Synthesis of Gd2O3:Eu nanoplatelets for MRI and fluorescence imaging.

We synthesized Gd2O3 and Gd2O3 doped by europium (Eu) (2% to 10%) nanoplatelets using the polyol chemical method. The synthesized nanoplatelets were characterized by X-ray diffraction (XRD), FESEM, TEM, and EDX techniques. The optical properties of the synthesized nanoplatelets were investigated by photoluminescence spectroscopy. We also studied the magnetic resonance imaging (MRI) contrast enhancement of T1 relaxivity using 3 T MRI. The XRD for Gd2O3 revealed a cubic crystalline structure. The XRD of Gd2O3:Eu3+ nanoplatelets were highly consistent with Gd2O3 indicating the total incorporation of the Eu3+ ions in the Gd2O3 matrix. The Eu doping of Gd2O3 produced red luminescence around 612 nm corresponding to the radiative transitions from the Eu-excited state 5D0 to the 7F2. The photoluminescence was maximal at 5% Eu doping concentration. The stimulated CIE chromaticity coordinates were also calculated. Judd-Ofelt analysis was used to obtain the radiative properties of the sample from the emission spectra. The MRI contrast enhancement due to Gd2O3 was compared to DOTAREM commercial contrast agent at similar concentration of gadolinium oxide and provided similar contrast enhancement. The incorporation of Eu, however, decreased the MRI contrast due to replacement of gadolinium by Eu.

Highly efficient NIR to visible upconversion in a ZnO:Er,Yb thin film deposited by a AACVD atmospheric pressure process

ZnO:Er3+,Yb3+ thin films with a hexagonal wurtzite structure were successfully deposited on Si (111) substrates at 430 °C by an aerosol-assisted chemical vapor deposition (AACVD) atmospheric pressure process. The films were deposited with fixed 3 mol% erbium concentration and various ytterbium concentrations of 6, 8, 9 and 10 mol%. The annealing treatment at 1000 °C was found to enhance the crystallinity and the upconversion (UC) emission of the films. UC emissions were investigated under 980 nm excitation, and the ZnO:Er3+,Yb3+ films exhibited the intense red 665 nm upconverted emissions of Er3+ ions originating from an efficient Yb–Er energy transfer process. The absolute upconversion Quantum Yield (UC-QY) of each film was measured for the UC emissions centered at 410, 540 and 665 nm at varying excitation power densities. UC-QY analysis has revealed that the ZnO:3 mol% Er,9 mol% Yb thin film possesses the highest total quantum yield of 5.59 ± 0.1% with a power density of 19.3 ± 3 W cm−2. These results show that this film is promising as an efficient upconversion layer suitable for many photonic applications.