Search results for "luminescence."
showing 10 items of 1568 documents
Synthesis, crystallographic and electrochemical study of ethynyl[2.2]paracyclophane derived cobalt metallatetrahedranes
2012
Abstract A series of alkynyl cobalt complexes [Co2(μ-η2-HCC–PCP)(CO)6−nLn] [n = 0 (2); n = 2, L2 = dppa (3), dppm (4), dcpm (6), 2 P(OPh)3 (7)] and [Co2(CO)4L2]2(μ-η2:μ-η2-HCC–PCP–CCH)] (L2 = dppm (8), dcpm (9); (PCP = [2.2]paracyclophane) has been prepared and characterized. The molecular structures of 3 and 4, as well as that of [Co2(CO)4(μ-CO)2(μ2-dcpm)] (5), have been determined by X-ray diffraction. Electrochemical studies (Cyclic Voltammetry, Rotating Disk Electrode) and luminescence spectroscopy have been used to evaluate the extent of the electronic communication through the PCP motif using the “Co2C2” centres as a probe. No electronic coupling between the Co2(CO)n centres via the b…
Through-bond versus through-space T1 energy transfers in organometallic compound-metalloporphyrin pigments
2009
The preparation and characterization of two d9−d9 M2-bonded Pt2(dppm)2(C≡CC6H4-M(P))2 complexes (where M = Zn or Pd, and P = diethylhexamethylporphyrin) were achieved. The central [Pt2(dppm)2(C≡CC6H4)2] organometallic unit appears to be an independent chromophore and is suspected to be luminescent at 77 K (in 2MeTHF) in the porphyrin-containing complexes, as this is the case for the unfunctionalized Pt2(dppm)2(C≡CPh)2 parent compound. However, when this spacer is connected (by a single C−C bond) to either M(P) (M = Zn, Pd), even in the absence of conjugation (as the computed dihedral angle between the C6H4 and porphyrin planes is ∼84.5°), total quenching of the luminescence of the [Pt2(dppm…
Green-Light Activation of Push-Pull Ruthenium(II) Complexes.
2020
Abstract Synthesis, characterization, electrochemistry, and photophysics of homo‐ and heteroleptic ruthenium(II) complexes [Ru(cpmp)2]2+ (22+) and [Ru(cpmp)(ddpd)]2+ (32+) bearing the tridentate ligands 6,2’’‐carboxypyridyl‐2,2’‐methylamine‐pyridyl‐pyridine (cpmp) and N,N’‐dimethyl‐N,N’‐dipyridin‐2‐ylpyridine‐2,6‐diamine (ddpd) are reported. The complexes possess one (32+) or two (22+) electron‐deficient dipyridyl ketone fragments as electron‐accepting sites enabling intraligand charge transfer (ILCT), ligand‐to‐ligand charge transfer (LL'CT) and low‐energy metal‐to‐ligand charge transfer (MLCT) absorptions. The latter peak around 544 nm (green light). Complex 22+ shows 3MLCT phosphorescenc…
Polyamines : études et applications
2008
International audience
Studies on the interaction of C1q,a subcomponent of the first component of complement, with porins fromSalmonella minnesotaincorporated into artifici…
1990
AbstractPurified outer membrane proteins (OMP) of Salmonella minnesota, Re-form, were incorporated into liposomes. These induced in macrophages a chemiluminescence signal identical to that of the intact Re-form. This signal was abolished by preincubation of porin-containing liposomes with purified C1q. Incorporation of isolated OMP into black lipid membranes (BLM) resulted in channel-formation which could not be inhibited by isolated C1q. Additionally, incubation of OMP-containing liposomes with BLM resulted in pore-formation within the BLM. This was amplified when lipid A was present within the liposomes. Preincubation of OMP-containing liposomes with purified C1q abolished pore-formation …
Exciton and multiexciton optical properties of single InAs/GaAs site-controlled quantum dots
2013
We have studied the optical properties of InAs site-controlled quantum dots (SCQDs) grown on pre-patterned GaAs substrates. Since InAs nucleates preferentially on the lithography motifs, the location of the resulting QDs is determined by the pattern, which is fabricated by local oxidation nanolithography. Optical characterization has been performed on such SCQDs to study the fundamental and excited states. At the ground state different exciton complex transitions of about 500 μeV linewidth have been identified and the fine structure splitting of the neutral exciton has been determined (≈65 μeV). The observed electronic structure covers the demands of future quantum information technologies.…
Enhancing the luminescence efficiency of silicon-nanocrystals by interaction with H+ions
2018
The emission of silicon nanocrystals (Si-NCs), synthesized by pulsed laser ablation in water, was investigated on varying the pH of the solution. These samples emit μs decaying orange photoluminescence (PL) associated with radiative recombination of quantum-confined excitons. Time-resolved spectra reveal that both the PL intensity and the lifetime increase by a factor of ∼20 when the pH decreases from 10 to 1 thus indicating that the emission quantum efficiency increases by inhibiting nonradiative decay rates. Infrared (IR) absorption and electron paramagnetic resonance (EPR) experiments allow addressing the origin of defects on which the excitons nonradiatively recombine. The linear correl…
Dendrimēri kā luciferāzi saturošas plazmīdas transfekcijas vektori, in vitro un in vivo pētījumi
2018
Gēnu terapija ir nozīmīga dažādu ģenētisku slimību ārstēšanai, kā arī DNS vakcīnu attīstībai, taču vēljoprojām limitējošais faktors gēnu terapijas pielietošanai klīnikā ir drošas un efektīvas metodes trūkums, lai DNS ievadītu šūnās. Ir izveidoti dažādi sintētiski vektori, kas ir drošāki par rekombinanto vīrusu metodi, taču tie nav pietiekami efektīvi. Dendrimēri ir viens no sintētiskajiem DNS ievades vektoru veidiem, kam piemīt vairākas priekšrocības salīdzinot ar citām metodēm, un šīs nanodaļiņas pēdējo gadu laikā pastiprināti pētītas gēnu ievadei in vitro un in vivo. Šajā pētījumā tika pārbaudīta četru dažādu dendrimēru – ceturtās paaudzes poli(amidoamīna) PAMAM G4, ceturtās paaudzes katj…
Origin of the large spectral shift in electroluminescence in a blue light emitting cationic iridium(III) complex
2007
A new, but archetypal compound [ Ir( ppy- F-2) (2)Me(4)phen] PF6, where ppy- F2 is 2-(2',4'- fluorophenyl) pyridine and Me(4)phen is 3,4,7,8- tetramethyl- 1,10- phenanthroline, was synthesized and used to prepare a solid-state light-emitting electrochemical cell (LEEC). This complex emits blue light with a maximum at 476 nm when photoexcited in a thin film, with a photoluminescence quantum yield of 52%. It yields an efficient single-component solid-state electroluminescence device with a current efficiency reaching 5.5 cd A(-1) and a maximum power efficiency of 5.8 Lm Watt(-1). However, the electroluminescence spectrum is shifted with respect to the photoluminescence spectrum by 80 nm resul…
Two‐Dimensional Electron Gas Effects on the Photoluminescence from a Nonintentionally Doped AlGaN/GaN Heterojunction
2002
Photoluminescence measurements on an AlGaN/GaN single heterojunction (SH), where piezoelectric and spontaneous polarization effects confine a two-dimensional electron gas (2DEG), are presented. Well-defined emissions between the bulk excitonic transitions and their LO-phonon replica are attributed to spatially indirect excitons located close to the interface. The strong interfacial electric field separates photogenerated holes and electrons, weakening their Coulomb interaction and causing a blueshift with increasing excitation intensity due to carrier population effects. In addition, direct experimental proof is obtained by applying an electric field normal to the interface. An energy shift…