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The Effect of Ionic Defect Interactions on the Hydration of Yttrium-Doped Barium Zirconate, Phys
(2021)
Kinetic Monte Carlo Simulations for Solid State Ionics: Case Studies with the MOCASSIN Program, Diff
(2021)
On the Opportunities of the Use of Luminescence Standards for Cuvette Spectrometer, WODIL 2021
(2021)
Phenanthroline chromophore as efficient antenna for Tb3+ green luminescence: A theoretical study
(2021)
The quaternary tungstates Li3Ba2RE3(WO4)8 (RE = La-Nd, Sm-Ho) were obtained by a ceramic synthesis route and were characterized by powder and single crystal X-ray diffraction. The structures of Li3Ba2Pr3(WO4)8 and Li3Ba2Tb3(WO4)8 were refined from single crystal diffractometer data: RbLiBi2(MoO4)4 type, space group C2/c, a = 528.57(2), b = 1292.39(6), c = 1934.80(10) pm, b = 91.522(4)°, 2151 F2 values, 108 parameters for Li3Ba2Pr3(WO4)8 and a = 520.54(2), b = 1272.03(6), c = 1918.85(10) pm, b = 91.948(4)°, 2020 F2 values, 108 variables for Li3Ba2Tb3(WO4)8. Striking polyhedral building units in these tungstates are WO4 tetrahedra and LiO6 octahedra, while the mixed occupied site and the barium atoms have higher coordination numbers, i.e. RE/Li@O8 and Ba@O10. In addition to the powder quality assessment by means of reflection spectroscopy, the synthesized samples were studied for their suitability as a scintillator material. Therefore, X-ray excited luminescence measurements where performed. Apart from Li3Ba2Ce3(WO4)8 and Li3Ba2Nd3(WO4)8, all compounds show strong emission under X-ray irradiation. Li3Ba2La3(WO4)8 and Li3Ba2Gd3(WO4)8 show blue CT luminescence caused by tungstate units, while the other samples show typical and multiple lines due to well known [Xe]4fn → [Xe]4fn transitions.
We report on a watt-level highly efficient europium laser operating at the 5D0→7F4 transition. It is based on the stoichiometric KEu(WO4)2 crystal. Under pumping by a green laser at 532.1 nm, the KEu(WO4)2 laser generated a maximum peak output power of 1.11 W at ∼703nm with a slope efficiency of 43.2% and a linear polarization (????‖????????). A laser threshold as low as 64 mW was achieved. True continuous-wave operation was demonstrated. The polarized emission properties of monoclinic KEu(WO4)2 were determined.
Different from negatively charged CuInS2 (CIS) based quantum dots (QDs), positively charged QDs are difficult to obtain in good optical quality, but are desirable for certain applications. We herein present a general synthesis strategy that allows for a universal surface modification of ternary CIS based QDs with thiol containing ligands.
The idea behind the synthesis design is, to apply a ZnS shell first for passivating and protecting the core QDs, and then add a second ZnS shell for the functionalization via ligand exchange. Whereby easy ligand exchange with thiolated molecules is systematically set up, by using a weak bonding amine ligand for the second shell. Molecules with various terminal groups were used to functionalize the nanoparticles and stabilize them in different media making any surface charge and polarity accessible. Surface defect chemistry seemed to play an important role in our synthesis strategy, therefore to gain a deeper understanding how these defect sites can alter the electronic structure of core/shell nanoparticles theoretical calculations based on density functional theory were performed, whilst structural, colloidal and optical properties were characterized experimentally (by dynamic light scattering, x-ray diffraction, infrared spectroscopy, zeta potential, absorption- and (time resolved) photoluminescence
measurements).
This work deals with the spectroscopic properties of praseodymium doped single crystalline lutetium aluminum garnet (LuAG:Pr3+). A special focus was set on temperature- and time-dependent spectroscopy. Beyond the well-known down-conversion luminescence of LuAG:Pr3+, also UV-A/B up-conversion luminescence under excitation with a 488 nm laser was thoroughly investigated. Furthermore, the results of the spectroscopic investigations on the single crystalline material were supplemented and compared with measurements on a microscale powder sample.
In addition, to the spectroscopic investigations, mechanistic considerations are presented to obtain a closer look at the up-conversion process in LuAG:Pr3+. We promote the thesis of a temperature-dependent energy transfer up-conversion mechanism.