Evolution of emission manners of organic light-emitting diodes: From emission of singlet exciton to emission of doublet exciton

The emission manners of organic light-emitting diodes(OLEDs) have experienced almost three-decade evolution.In this review,we briefly summarized the emission manners of OLEDs including:(ⅰ) emission from singlet exciton;(ⅱ) emission from triplet exciton;(ⅲ) emission from singlet exciton converted from triplet exciton.Then we introduced a new type of OLEDs with the emission from doublet exciton,wherein organic neutral radicals are used as emitters.Due to the spin-allowed transition of doublet excitons,using neutral radicals as emitters is believed to be a new way to break the 25%upper limit of internal quantum efficiency of OLEDs.The progress of emissive stable neutral radicals is also shortly reviewed.     

Organic Light‐Emitting Diodes Using a Neutral π Radical as Emitter: The Emission from a Doublet

Triplet harvesting is a main challenge in organic light‐emitting devices (OLEDs), because the radiative decay of the triplet is spin‐forbidden. Here, we propose a new kind of OLED, in which an organic open‐shell molecule, (4‐N‐carbazolyl‐2,6‐dichlorophenyl)bis(2,4,6‐trichlorophenyl)methyl (TTM‐1Cz) radical, is used as an emitter, to circumvent the transition problem of triplet. For TTM‐1Cz, there is only one unpaired electron in the highest singly occupied molecular orbital (SOMO). When this electron is excited to the lowest singly unoccupied molecular orbital (SUMO), the SOMO is empty. Thus, transition back of the excited electron to the SOMO is totally spin‐allowed. Spectral analysis showed that electroluminescence of the OLED originated from the electron transition between SUMO and SOMO. The magneto‐electroluminescence measurements revealed that the spin configuration of the excited state of TTM‐1Cz is a doublet. Our results pave a new way to obtain 100 % internal quantum efficiency of OLEDs.     

Effect of Gamma Radiation on the IR Spectra of Some Divalent and Trivalent 8-Hydroxyquinoline Complexes

The I R spectra of ten elements chelated with 8-hydroxyquinoline were measured before and after gamma irradiation with different doses (7–518 Mrd) and discussed. It was found that the rate of decrease, K, of the absorbancy of M—O and (C—O)-M stretching vibration bands depends on the chelated cation. Moreover, the Cu 8-hydroxyquinoline complex is suggested as gamma dosimeter for doses ranging from 4.8 to 160 Mrd.     

A novel tetraoxime and its dinuclear and tetranuclear transition metal complexes

A new bis(dioxime) ligand (H₄L) containing the diphenyl ether moiety has been prepared by reacting 3,3,4,4-tetraaminodiphenyl ether (1) with 2,3-butanedione monoxime (2). Dinuclear copper(II) and cobalt(III) complexes of H₄L exhibit a metal–ligand ratio of 2:1 and the ligand coordinates through the 4 nitrogen atoms, as do most bis(dioximes). The [Cu₂(H₂L)](ClO₄)₂ molecule coordinates to the other two copper(II) ions through the deprotonated oximate oxygens to yield a tetranuclear structure, doubly-bridged by the oximate groups in a cis arrangement. The structure of bis(dioxime) and its complexes were identified by elemental analyses, ¹H-, ¹³C-n.m.r, i.r and m.s. spectral data.     

Surface Chemistry Studies of Quantum Dots (QDs) Modified with Surfactants

Since luminescent CdSe quantum dots (QDs) have shown great potential in biological labeling, the surface chemistry behavior of QDs at interfaces is of great research interest. In the present study, CdSe QDs with green luminescence were modified with hydrophobic chains of varying lengths [from C6 to C18]. These modified QDs can be utilized to form stable monolayers at the air/water interface. Surface pressure-area isotherms of modified QDs have been measured and limiting molecular areas have also been extrapolated in order to analyze the size of the QDs. UV absorption spectra of modified QDs at various surface pressures were also determined. Surface chemistry, as well as the topographic properties, of modified QDs in Langmuir and L-B films was discussed.     

Aromatic Character of All Possible C_(36)H_2 Isomers

1 INTRODUCTION Hydrogenated fullerenes have become one of the most intense studies of fullerene chemistry. Most researches are mainly focused on C60 and C70 cages, and C36 has received much attention in recent years. In 1998, Piscoti et al.[1] reported a solid-state nuclear magnetic resonance (NMR) measurement on a C36 solid and suggested that the C36 molecule has D6h symmetry. In 2000, Koshio etc.[2, 3] reported the syntheses of a number of compounds of C36, i.e., C36H4, C36H6, C3…     

Next-to-leading order QCD and electroweak corrections to Higgs-strahlung processes at the LHC

In this paper we calculate the total and fiducial cross sections as well as differential distributions for the Higgs-strahlung or VH process pp→VH→lv1/1~-1~++H,(V = W or Z, 1=e, μ) including QCD and electro-weak corrections up to next-to-leading order before and after reweighting photon PDFs of NNPDF2.3 qed, NNPDF3.0 qed,MRST2004 qed, CT14 QEDinc, and LUXqed at the LHC with 13 TeV and Higgs boson mass MH = 125 GeV. The predictions from the various photon PDFs before and after reweighting against each other are in good agreement.The photon PDF uncertainties of the photon-induced cross sections decrease significantly with the reweighting PDFs.     

Aromaticity of Heterofullerenes C18BxNy (x+y=2) and Their Molecular Ions

采用拓扑共振能(TRE)和百分拓扑共振能(%TRE)方法研究了从富勒烯C20(Ih)产生的异质富勒烯C18N2、C18B2和C18BN的所有可能的异构体和分子离子的芳香性．讨论了C18BxNy异构体的芳香性和杂原子在C20(Ih)中取代位置间的关系．结果表明,中性状态和阳离子状态时各异构体的TRE都为负值,具有反芳香性．但它们高价阴离子的TRE都为正值,具有芳香性．C18N2、C18B2 和C18BN中都是杂原子在1,11-取代的异构体最稳定．异质富勒烯都比C20的芳香性高．在中性状态下的稳定性顺序为C18N2>C18BN>C18B2>C20．在形成闭壳层结构时的稳定性顺序为C18B28->C206->C18BN6->C18N24-．理论上预测C22BxNy的高价阴离子具有很高的芳香性．     

DNA Hydrolysis by Homo- and Heteronuclear Cu(II)–Ni(II) Complexes of Two Diester-type Ligands

Summary. Nucleolytic activities of novel mononuclear Cu(II), homo- and heterodinuclear Cu(II)–Ni(II) complexes with two diester-type ligands were investigated on pCYTEXP by neutral agarose gel electrophoresis. The analyses of the cleavage products obtained electrophoretically indicate that the examined complexes induce very similar conformational changes on supercoiled DNA by converting supercoiled form to nicked form. At concentrations greater than 100M, the complexes possessed effective nucleolytic activities for 10min of incubation time. However, their nucleolytic activities did not increase significantly with longer periods of incubation. The pH-nucleolytic activity profiles of the complexes differed significantly. Metal complex induced DNA cleavage was also tested for inhibition by various radical scavengers. It could be proposed from the data that diffusible intermediate oxidants are not involved in these reactions or they are not necessary for DNA cleavage since none of antioxidants inhibited DNA cleaving activities of the complexes.