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We have prepared NaYF4:Er3+/Yb3+/Ca2+ phosphors using the solvothermal method and discussed the influence of annealing on the crystal structure, morphology, and photoluminescence characteristics in this work. The results show that, with the increase of annealing temperature, the crystallization phase changes from a single cubic structure to a mixed phase of cubic and hexagonal phases and the morphology is also condensed from spherical particles to sheets. In particular, the PL intensity of the annealed phosphor becomes much stronger than that of the unannealed phosphor. An annealed NaYF4:Yb3+, Er3+/Ca2+ phosphor is selected as an example to investigate the performance of high temperature sensor based on the fluorescence intensity ratio between two green emissions. The measurement range and the maximum absolute sensitivity SA of the annealed sensor material are superior to the corresponding parameters of the same phosphor without annealing. The curve of relative sensitivity curve SR decreases as the ambient temperature increases, but that of the revolution δT presents an opposite trend. All the results show that the NaYF4:Er3+/Yb3+/Ca2+ phosphor is more suitable for application on the high temperature sensor after annealing. [ABSTRACT FROM AUTHOR]

[Display omitted] • Complexes 1a , 1b , 2a , 2b , 3a and 3b contain a stable four-membered chelating ring. • The modulation of the luminescence color from green to blue-green and red was achieved. • The OLEDs based on 1a , 1b , 2a , 2b , 3a and 3b exhibit low efficiency roll-off. Six dpppy (P,P-diphenyl-N-(pyridin-2-yl)phosphinic amide)- and dppq (P,P-diphenyl-N-(quinolin-2-yl)phosphinic amide)-based iridium(III) complexes 1a , 1b , 2a , 2b , 3a and 3b containing four-membered chelate architecture were synthetized. Their crystal structure and photophysical properties were investigated. The crystal structure shows that two coordinating N atoms from the ancillary ligand dpppy and dppq form a four-membered chelate architecture with the centered iridium(III). By changing the substituent groups and conjugation of the cyclometalated ligand, the control of the luminescent color of the complexes was achieved. In CH 2 Cl 2 solution, complexes 1a , 1b , 2a , 2b , 3a and 3b emitted phosphorescence peaked at 509, 506, 479, 478, 620 and 618 nm with CIE color coordinates of (0.29, 0.60), (0.27, 0.61), (0.13, 0.37), (0.14, 0.35), (0.67, 0.33) and (0.67, 0.33), respectively. The quantum chemical calculation shows that their emitting light is primarily from 3LC π−π* states of the cyclometalated ligand. Electroluminescent devices with dual light-emitting layers were fabricated and exhibited mild efficiency roll-off. [ABSTRACT FROM AUTHOR]

• Two ionic cuprous complexes with thermally activated delayed fluorescence were synthesized. • Both complexes exhibit high contributions of TADF (83 and 80%, respectively) and PLQYs (47.5 and 60.5%, respectively) in the solid state at ambient temperature. • The small exchange energy caused by the pronounced spatial separation between HOMOs and LUMOs leads to a small Δ E ST and TADF at ambient temperature. • The OLEDs based on both complexes exhibit good performance and very mild efficiency roll-off. Herein two novel ionic cuprous complexes [Cu(POP)(Pytzb)]BF 4 (Cu1 , POP = bis(2-diphenylphosphinophenyl)ether, Pytzb = 2-(1-(benzyl)-1H-1,2,3-triazol-4-yl)pyridine) and [Cu(Xantphos)(Pytzb)]BF 4 (Cu2 , Xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) have been synthesized in reasonable yields, and their crystal structure, UV absorption and photoluminescent properties, as well as electrochemical behaviors were investigated. At 300 K, both Cu1 and Cu2 in solid state exhibit outstanding green luminescence peaked at 533 and 526 nm, respectively, with significantly high photoluminescent quantum yields (PLQYs, 47.5 and 60.5%, respectively). Detailed exploration of emission decay times for Cu1 and Cu2 in dependence of temperature demonstrates that the two complexes are typical thermally activated delayed fluorescence (TADF) materials at ambient temperature with TADF proportions of 83 and 80%, respectively. The two complexes were employed as dopants in solution-processed electroluminescent devices. Thermally activated delayed fluorescence (TADF) of two new ionic cuprous complexes bearing 1,2,3-triazole ligand has been realized. Especially, both complexes exhibit high contributions of TADF (83 and 80%, respectively) and PLQYs (47.5 and 60.5%, respectively) in the solid state at ambient temperature. [Display omitted] [ABSTRACT FROM AUTHOR]

A cationic iridium complex [Ir(dfpmpy) 2 (pzpy)](PF 6 ) with 2-(1H-pyrazol-1-yl)pyridine as ancillary ligand has been prepared, and its crystal structure, photophysical and electrochemical properties have been investigated. In degassed CH 3 CN solution, this complex exhibits blue emission with a peak wavelength of 451 nm. Photophysical property indicates that photoluminescence of complex [Ir(dfpmpy) 2 (pzpy)](PF 6 ) originates mainly from ligand-centered 3 π → π ∗ states. In addition, solution-processed organic light-emitting diodes based on [Ir(dfpmpy) 2 (pzpy)](PF 6 ) have been fabricated. A blue light electroluminescence (484 nm) was observed and a maximum current efficiency of 1.56 cd A −1 corresponding to a maximum power efficiency of 0.33 lm W −1 , has been achieved. This demonstrates that this complex is a promising phosphor for achieving efficient electrophosphorescence in the blue light region. [ABSTRACT FROM AUTHOR]

Four transition metal complexes with Schiff base and 1,10-phenanthroline, [Cu(L)(phen)]2·C2H5OH (1), [Zn(L)(phen)]2·C2H5OH (2), [Ni(L)(phen)]2·C2H5OH (3), and [Co(L)(phen)]2·C2H5OH (4) (H2L = 1-((2-hydroxynaphthalen-1-yl)methylene)thiosemicarbazide; phen = 1,10-phenanthroline) were synthesized and characterized by physico-chemical methods. The crystal structure of1was determined by X-ray single-crystal diffraction analysis.1crystallizes in the orthorhombic space groupPbcawitha = 15.008(9),b = 16.100(10),c = 37.54(2) Å,V = 9070(10) Å3,Z = 8,GOOF = 1.002,R1 = 0.0626, andwR2 = 0.0912. The fluorescence and urease inhibitory activities of the compounds were tested. The enzymatic activity study indicated that3possessed potent inhibition againstjack beanurease, with IC50 = 1.2 ± 0.1 μM, and about 35 times more than 42.1 ± 0.4 acetohydroxamic acid as positive reference. This suggests that inhibitory efficiency of these complexes can be strongly influenced by different transition metal ions. [ABSTRACT FROM AUTHOR]

Abstract: Recently, the stabilities of light-emitting electrochemical cells (LECs) based on cationic iridium(III) complexes with controlled intramolecular π–π stacking interactions by adopting pendant phenyl rings have been dramatically enhanced compared with those of the complexes without π–π stacking interactions within the molecule. Herein, a novel cationic iridium complex [Ir(ppy)2(pyphmi)]PF6[ppy=2-phenylpyridine, pyphmi=1-pyridyl-3-phenylimidazolin-2-ylidene-C,C2′] which exhibits intramolecular π-stacking interaction has been prepared and its X-ray crystal structure has been investigated. Unexpectedly, however, the corresponding LECs based on [Ir(ppy)2(pyphmi)]PF6 do not show significantly enhanced stabilities compared to the LECs based on [Ir(ppy)2(pymi)]PF6 [pymi=1-pyridyl-3-methylimidazolin-2-ylidene-C,C2′] without pendant phenyl rings within the molecule. This phenomenon is attributed to the very long centroid–centroid distance between the π-stacked phenyl rings, which results from the larger tension of substituted five-membered ring moiety (imidazolin-2-ylidene). In addition, irreversible oxidation and reduction processes would also decrease the electrochemical stability of [Ir(ppy)2(pyphmi)]PF6. Thus, intramolecular π–π stacking interaction using pendant phenyl rings is not always effective to improve the stability of LECs. [Copyright &y& Elsevier]

Abstract: Two new blue emitting cationic iridium complexes with N-heterocyclic carbene–pyridine as the ancillary ligand, namely, [Ir(ppy)2(pymi)]PF6 and [Ir(dfppy)2(pymi)]PF6 (pymi is 1-pyridyl-3-methylimidazolin-2-ylidene-C,C2′, ppy is 2-phenylpyridine, dfppy is 2-(2,4-difluorophenyl)pyridine and is hexafluorophosphate), have been prepared, and the photophysical and electrochemical properties together with X-ray crystal structures have been investigated. In CH3CN solutions, [Ir(ppy)2(pymi)]PF6 and [Ir(dfppy)2(pymi)]PF6 exhibit blue light emission with the peaks at 472 and 451nm, respectively. Both photophysical properties and quantum chemical calculations indicate that photoluminescences of these complexes are mainly from ppy- or dfppy-based 3 π → π ∗ states. Solution-processed organic light-emitting diodes (OLEDs) based on [Ir(ppy)2(pymi)]PF6 and [Ir(dfppy)2(pymi)]PF6 give blue–green electroluminescence (506 and 482nm, respectively). At a doping concentration of 5wt.%, the device based on [Ir(ppy)2(pymi)]PF6 reaches a maximum efficiency of 5.2cdA−1, which indicates that this complex is a promising phosphor for achieving efficient electrophosphorescence in the blue–green region. [Copyright &y& Elsevier]

In this work, we report three deep-blue emitting cationic iridium complexes Ir1–Ir3 with 2ʹ,6ʹ-difluoro-2,3ʹ-bipyridine cyclometalated ligand and pyrazole-type ancillary ligands. Synthesis, crystal structure, photophysical and electrochemical properties of Ir1–Ir3 are studied in detail. Ir1–Ir3 exhibit efficient phosphorescence emissions at 439, 438 and 437 nm with CIE 1931 coordinates of (0.14, 0.12), (0.14, 0.12) and (0.14, 0.13), and luminescence quantum yields of 0.35, 0.27 and 0.50 in CH 2 Cl 2 solutions, respectively, which are among the highest levels of ever reported cationic iridium(III) complexes emitting deep-blue light. High luminescence quantum yields, excellent color purity and short lifetimes demonstrates the great potential of Ir1–Ir3 for light-emitting electrochemical cells (LECs) and solution-processable organic light-emitting diodes (OLEDs) as efficient blue emitters. Image 1 • Deep-blue emitting cationic iridium complexes. • Ir1−Ir3 are synthesized. • Ir1−Ir3 exhibit high photoluminescence quantum yields in CH 2 Cl 2 solutions. [ABSTRACT FROM AUTHOR]

Structural and optical properties of 1% Al-doped Zn 1− x Mg x O ( x =0–8%) nanoparticles prepared by autocombustion method were systematically investigated by means of X-ray diffraction, scanning electron microscopy, ultraviolet–visible absorbance measurement and photoluminescence spectra. All the nanoparticles retained hexagonal wurtzite structure of ZnO, and the average sizes of the nanoparticles were about 80 nm. The band gap and near band emission energies determined from absorbance and photoluminescence spectra both increased linearly with increasing Mg content, which implied that the Mg worked effectively on ZnO band gap engineering, irrespective of Al codoping. The Stokes shift remained nearly unchanged, which demonstrated that the carrier concentration and resistivity of Al-doped ZnO nanoparticles changed slightly after Mg codoping, i.e. the Al doping efficiency was not heavily destroyed in band gap engineering. Meanwhile, there is no obvious difference in structural and optical properties between unannealed and annealed samples, which indicated that annealing was not necessary for combustion synthesis processing. [ABSTRACT FROM AUTHOR]