D. Rau

Photoluminescence and decay profiles of undoped and Fe3+, Eu3+-doped PLZT ceramics at low temperatures down to 10 K

Luminescence, time-resolved luminescence, excitation spectra and lifetimes of nominally pure and Eu, Fe-doped PLZT ceramics with perovskite A (Pb, La) B (Zr, Ti) O3 structure are investigated as a function of temperatures down to 10 K in order to elucidate luminescence centers in hot-/cold-pressed PLZT (9/65/35) and cold-pressed PLZT (8/70/30). At 10 K, the luminescence band of PLZT is considered to consist of two bands centered at 18 100 cm−1 (center 1) and 15 600 cm−1(center 2) with lifetimes of about τ1=1 ms and τ2=60 μs, respectively. Comparing luminescence, lifetimes and excitation spectral properties of various PLZT samples, center 1 can be assigned to octahedral [Ti(IV)O6] structures which are present in the cold-pressed, polycrystalline samples. Center 2 is identified as being due to oxo-coordinated octahedral Fe3+ ions associated with oxygen and lead-deficient octahedral [BO6−δ] (B=Ti4+, Zr4+) complexes in defect domains in the hot-pressed ceramics. Blue shift to 19 500 cm−1 and an abrupt shortening of lifetimes to 0.1 ms were observed at around 160 K due to the phase transition.

Surface effects in luminescence and decay profiles of Cr6+-V5+ and Cr6+-Ag+ codoped nanostructured sol-gel SiO2 glass

Abstract Luminescence and decay profiles of codopant (Cr6+. V5+) and (Cr6+, Ag + ) ions in sol- gel silica glasses are investigated at temperatures between 10 and 300 K. The closed-shell electronic structures of these ions reveal luminescence and decay profiles affected sensitively by energy migration processes, surface effects and preparation methods of the nano-structured matrices.

Luminescence and circularly polarized luminescence of macrocyclic Eu(III) and Tb(III) complexes embedded in xerogel and sol-gel SiO2 glasses

Abstract Luminescence, time-resolved luminescence, circularly polarized luminescence (CPL) and decay profiles of Ln(III)(15-crownether-5) ( Ln = Ce, Sm, Eu, Tb ) and Tb(III)-(R),(S)-cyclen derivative complexes doped in xerogel and sol–gel silica glasses are measured at temperatures down to 10 K to characterize luminescence properties and the electronic structure in the excited states. Luminescence spectral profiles and calculation of crystal field parameters ( B 0 (2) , B 2 (2) ) in the 5 D 0 → 7 F J (J=1,2) transition give evidence of the fact that the pentagonal and planar structure of Eu(III) (15-crownether-5) does hold in xerogel and sol–gel glasses prepared at temperatures below 100°C. As annealing temperatures are increased from 80°C to 750°C, Eu(III) complexes in sol–gel glasses are found to decompose gradually to SiO 2 :Eu 3+ . Tb(III)-(R) and (S)-cyclen derivative complexes in xerogel reveal at room temperature and 10 K sharp CPL spectra with luminescence dissymmetry factors g lum =−0.1 and 0.1, respectively. These complexes doped in sol–gel glasses represent luminescence characteristics of rare earth ions encapsulated in the nano-porous host.

Luminescence and circularly polarized luminescence of excited-state chiral structures in one-dimensional PIC-J dye aggregates

Abstract Luminescence (TL) and circularly polarized luminescence (CPL) spectra of polymeric pseudoisocyanine dye J-aggregates (PIC-J) are investigated to clarify the molecular arrangements generating a one-dimensional excitonic J-band in the excited state. In the presence of l - and d -phenylalaninol (PAOL), the PIC-J aggregates are found to reveal CPL spectra at room temperature with luminescence dissymmetry factors g lum for J-bands of −0.05, which are comparable in magnitude with the corresponding Kuhn g -factors in the ground state derived by comparison of J-bands in circular dichroism and absorption spectra. Chiroptical and helical structures along with one-dimensional chains are considered to generate Pfeiffer effects through intermolecular interactions between PIC-J dye and chiral PAOL. CPL and TL spectra of PIC-J dyes in the presence of DNA and phenylethylamine are further considered.