Rhenium complex as emitting material in highly efficient phosphorescent organic light-emitting diodes

Interest in luminescent materials able to efficiently emit in the solid state is continuously growing, because in most applications the dyes are used as solid films. This is the case of the Organic Light Emitting Diodes (OLEDs), where electroluminescent metal complexes have been widely investigated as dopants, able to increase their performances [1]. We present here a dinuclear Re(I) complexes (1, see Scheme 1) whose emission is higher in solid state and in PMMA matrix than in solution and is used as dopant in OLEDs. This complex belong to the family of neutral Re(I) complexes with general formula [Re2(CO)6(\u3bc-1,2-diazine)(\u3bc-X)2], where X is halogen. Some of them have recently gained interest for their intense yellow/green emission, occurring from triplet metal-to-ligand charge transfer (3MLCT) states [2], showing a modulation effect of the diazine substituents on wavelengths, lifetimes and quantum yields of the emission. \u3a6 up to 0.53 has been measured for the di-chloro complexes containing diazines bearing alkyl groups in both the \u3b2 positions [3]. At variance with the chloro derivatives, the bromo analogue 1 is almost not-emitting in solution (\u3a6em 0.002 in deareated toluene). We have now found that in the solid state 1 shows intense yellow-orange emission (\u3a6em 0.50 in neat powder), blue shifted with respect to the solution (560 nm vs. 620 nm). The emission is intense also in PMMA matrix (\u3a6em 0.19 in PMMA at 10% w/w, 556 nm). This very high aggregated emission here is discussed in terms of the restriction of the intramolecular roto-vibrational motions of the \u201cRe2(CO)6(\u3bc-Br)2\u201d scaffold imposed by the rigid environment, as evidenced by the strong decrease of the knr. Moreover a parallel increase of kr is noticed, which clearly shows the influence of the halides in determining not only the energy of the excited state, but also the nature of the lowest (emitting) state. These properties allowed its successful use as a phosphorescent dopant in OLEDs and here we report the performances of OLED devices prepared both by solution- and vacuumprocessing. The values of the external quantum efficiency are 1.7% (4.3 cd/A and 1.7 lm/W) and 10% (29.1 cd/A and 22.1 lm/W) respectively and are the highest ever reported for rhenium-based devices, comparable to state-of-the-art devices employing Ir(III)- and Pt(II)- based metal complexes. The combination of synthetic strategy and encouraging results in potential OLEDs applications should make these dinuclear Re(I) complexes highly attractive to a broad spectrum of research fields. 1. \u201cHighly efficient OLEDs with Phosphorescent Materials\u201d H. Yersin Ed. Wiley-VCH, (2008). 2. D. Donghi, G. D\u2019Alfonso, M. Mauro, M. Panigati, P. Mercandelli, A. Sironi, P. Mussini, L. D\u2019Alfonso, Inorg. Chem. 28 (2008) 4243-4255. 3. M. Mauro, E. Quartapelle Procopio, Y. Sun, C. H. Chien, D. Donghi, M. Panigati, P. Mercandelli, P. Mussini, G. D\u2019Alfonso, L. De Cola, Adv. Funct. Mater. 19 (2009) 2607-2614

Grainyhead-like 2 (GRHL2) knockout abolishes oral cancer development through reciprocal regulation of the MAP kinase and TGF-β signaling pathways

Grainyhead-Like 2 (GRHL2) is an epithelial-specific transcription factor that regulates epithelial morphogenesis and differentiation. Prior studies suggested inverse regulation between GRHL2 and TGF-β in epithelial plasticity and potential carcinogenesis. Here, we report the role of GRHL2 in oral carcinogenesis in vivo using a novel Grhl2 knockout (KO) mouse model and the underlying mechanism involving its functional interaction with TGF-β signaling. We developed epithelial-specific Grhl2 conditional KO mice by crossing Grhl2 floxed mice with those expressing CreER driven by the K14 promoter. After induction of Grhl2 KO, we confirmed the loss of GRHL2 and its target proteins, while Grhl2 KO strongly induced TGF-β signaling molecules. When exposed to 4-nitroquinoline 1-oxide (4-NQO), a strong chemical carcinogen, Grhl2 wild-type (WT) mice developed rampant oral tongue tumors, while Grhl2 KO mice completely abolished tumor development. In cultured oral squamous cell carcinoma (OSCC) cell lines, TGF-β signaling was notably induced by GRHL2 knockdown while being suppressed by GRHL2 overexpression. GRHL2 knockdown or KO in vitro and in vivo, respectively, led to loss of active p-Erk1/2 and p-JNK MAP kinase levels; moreover, ectopic overexpression of GRHL2 strongly induced the MAP kinase activation. Furthermore, the suppressive effect of GRHL2 on TGF-β signaling was diminished in cells exposed to Erk and JNK inhibitors. These data indicate that GRHL2 activates the Erk and JNK MAP kinases, which in turn suppresses the TGF -β signaling. This novel signaling represents an alternative pathway by which GRHL2 regulates carcinogenesis, and is distinct from the direct transcriptional regulation by GRHL2 binding at its target gene promoters, e.g., E-cadherin, hTERT, p63, and miR-200 family genes. Taken together, the current study provides the first genetic evidence to support the role of GRHL2 in carcinogenesis and the underlying novel mechanism that involves the functional interaction between GRHL2 and TGF-β signaling through the MAPK pathways

Implication of Genetic Variants Near TCF7L2, SLC30A8, HHEX, CDKAL1, CDKN2A/B, IGF2BP2, and FTO in Type 2 Diabetes and Obesity in 6,719 Asians

OBJECTIVE— Recent genome-wide association studies have identified six novel genes for type 2 diabetes and obesity and confirmed TCF7L2 as the major type 2 diabetes gene to date in Europeans. However, the implications of these genes in Asians are unclear

Microwave and terahertz dielectric properties of MgTiO3–CaTiO3 ceramics

The THz dielectric properties of MgTiO3–CaTiO3 ceramics are reported. The ceramics were prepared via a solid-state reaction route and the sintering conditions were optimized to obtain ceramics with high permittivity and low loss in the terahertz frequency domain. The amount of impurities (MgTi2O5) and grain size increased with increasing sintering temperature. The dielectric properties improved with increasing density, and the best terahertz dielectric performance was obtained at 1260 °C, with a permittivity of 17.73 and loss of 3.07×10−3. Ceramics sintered above 1260 °C showed a sharp increase in loss, which is ascribed to an increase in the impurity content

Proximity effect at superconducting Sn-Bi2Se3 interface

We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions down to 250 mK and in different magnetic fields. A number of conductance anomalies were observed below the superconducting transition temperature of Sn, including a small gap different from that of Sn, and a zero-bias conductance peak growing up at lower temperatures. We discussed the possible origins of the smaller gap and the zero-bias conductance peak. These phenomena support that a proximity-effect-induced chiral superconducting phase is formed at the interface between the superconducting Sn and the strong spin-orbit coupling material Bi2Se3.Comment: 7 pages, 8 figure

Centrality Dependence of the High p_T Charged Hadron Suppression in Au+Au collisions at sqrt(s_NN) = 130 GeV

PHENIX has measured the centrality dependence of charged hadron p_T spectra from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction of the contribution from hard scattering to high p_T hadron production. For central collisions the yield at high p_T is shown to be suppressed compared to binary nucleon-nucleon collision scaling of p+p data. This suppression is monotonically increasing with centrality, but most of the change occurs below 30% centrality, i.e. for collisions with less than about 140 participating nucleons. The observed p_T and centrality dependence is consistent with the particle production predicted by models including hard scattering and subsequent energy loss of the scattered partons in the dense matter created in the collisions.Comment: 7 pages text, LaTeX, 6 figures, 2 tables, 307 authors, resubmitted to Phys. Lett. B. Revised to address referee concerns. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are publicly available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm

Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration

Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (p_T), elliptic flow, two-particle correlations, non-statistical fluctuations, and suppression of particle production at high p_T. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted to Nuclear Physics A as a regular article; v3 has minor changes in response to referee comments. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm