Ce:YVO4晶体的生长及其电荷迁移发光

为探索新型的白光LED荧光粉材料,采用提拉法生长了Ce2(CO3)3掺杂的Ce3+∶YVO4晶体,并对生长晶体的结构和光谱性能进行了表征。通过XRD测试,确定了由提拉法生长的Ce3+∶YVO4晶体的晶相没有发生变化。Ce3+∶YVO4晶体在450 nm处有一个较宽的发射带,在620 nm处有一个明显的发射峰。分析表明,在Ce3+掺杂的YVO4晶体中,铈离子主要以三价离子的形式存在,但在激发光照射下出现的620 nm发射表明有Ce4+存在,并且Ce4+与配位O2-形成了电荷迁移态(CTS)。     

螺芴类空穴传输材料的电荷传输性质研究

螺芴类空穴传输材料因优异的光电性能而备受关注。为了探究其电荷传输机制,本文采用密度泛函理论研究了三种螺芴类小分子空穴传输材料的电子结构、重组能和电子耦合。结合Marcus电荷转移理论,精确计算了所有小分子的载流子迁移率,并与实验数据进行了比较。结果表明,X60和HT2分子的空穴迁移率与实验数据吻合良好,处于同一数量级,说明利用该理论模型精确计算分子的空穴迁移率具有一定的可行性。此外,ST2的空穴迁移率为1.82×10^-4 cm²·V^-1·s^-1,且具有良好的稳定性,说明对螺核杂原子的修饰可进一步提升空穴传输材料的性能。这为开发高效的空穴传输材料提供了重要策略。     

Charge Transfer in Misfit Layer Chalcogenides, [(MX)n]1+x(TX2)m: a Key for Understanding their Stability and Properties

Abstract

Stability of misfit layer chalcogenides (M.L.C.) is always governed by a charge transfer (C.T.) mechanism. A comparison between M.L.C. and parent intercalated layered binary systems shows comparable characteristics, which illustrate the role of electron donor for the MX part (or its corresponding A-intercalant species) towards the TX² acceptor part. In that way, intercalation chemistry within the vdW gap of multilayered TX² misfit derivatives is also considered. The donor character of the MX part, easy to understand when trivalent M cations are present, can be also assumed if a divalent M cation is partly substituted for a trivalent one, as revealed from precise electron microprobe analysis. Examples of M.L.C. with enlarged MX part (with mixed M^+II, M^+III) emphasize the reality of the C.T. This M-to-T donor effect necessarily controls the transport and intercalation properties.     

Efficient Charge Balance of Green Organic Light Emitting Diodes Using Mixed Charge Transporting Materials as the Host

The mixed layer for an emitting layer (EML) consists of two materials 4,4′,4′′-tris(N-carbazolyl)-triphenylamine (TCTA) and 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) without host material. A series of EML structures were fabricated with three types of single mixed layers (mixing ratio 2:1, 1:2) and double mixed layers (mixing ratio 2:1/1:2), and the EML of using double mixed layer was optimized. The maximum luminous efficiency (LE) and quantum efficiency (QE) were 62.07 cd/A, 18.92%, respectively. Moreover, the roll-off ratio of LE was 20.42% at 20,000 cd/m². Interestingly, this result shows the roll-off ratio was reduced roughly 50% compared to the reference device.     

不同位置Mg掺杂ZnO电荷转移和光学性质的第一性原理研究

基于密度泛函理论计算了本征氧化锌、6.25％Mg以及同位、邻位、间位12.5％Mg原子掺杂氧化锌晶体的几何结构、原子轨道电子布居、静电势和电子结构特征;探究了Mg原子掺杂对氧化锌能带结构、态密度以及对应的光学性质和电学性质的影响.结果表明Mg掺杂会导致氧化锌晶体的晶格体积变大,载流子迁移率降低和吸收边蓝移;邻位双原子掺...     

Spectroscopic properties of Zn‐naphtholimines‐TCNQ charge transfer complexes with variable ligand radicals

Over the last decades, many different types of charge transfer complexes have been discussed as organic metals. The design and synthesis of the required efficient p‐electron donors constitutes an active area of modern materials chemistry. An important family with these properties is based on naphtholimines, which are known to form electrically conductive salts with a variety of organic acceptor molecules such as tetracyano‐pquinodimethane (TCNQ). Since the reduction potential of transition metal complexes can be readily modified by the selection of proper ligands and ligand substitution, such complexes are favored candidates for designed syntheses. The present work is aimed toward the study of Zn‐Naphtholimines‐TCNQ charge transfer complexes with fractional electron transfer per formula unit. The electron transfer is an essential factor in the control of electrical conductivity. Of particular interest was the effect of ligand volume variations on the degree of charge transfer. Both IR‐ spectroscopy and electron paramagnetic resonance (EPR) spectroscopy were used as analytic tools. We found, that Zn[RNAFIN]₂‐2TCNQ molecules are partially ionized, and that the electron delocalization is strongly affected by the chosen ligand volume.     

The Geometry of Tetrathiotetracene as a Donor in Charge Transfer Complexes: an ab Initio Theoretical Investigation

Ab initio STO-3G calculations are performed on both tetracene (T) and tetrathiotetracene (TTT), and their respective radical-cations. Mulliken populations indices and nodal structure of the HOMO explain the geometry changes of these compounds upon ionization. The strong relaxation energy calculated for tetrathiotetracene, and its low first ionization potential, are related to the grafting of the two disulfide bridges and largely justify the peculiar behavior of TTT upon charge transfer     

Square-Planar trans-Bis-(1-p-n-octylphenylbutane-1,3-dionato) copper (II), a New Compound Exhibiting Three Kinds of ‘Double Melting’ Behaviour

The new compound, bis-(1-p-n-octylphenylbutane-1,3-dionato) copper(II) has four polymorphs, C¹ (m.p. 96°C), all having the same squareplanar trans structure. C¹, C^a, and C^m exhibit ‘double melting’ behaviour, i.e., they melt at their was observed only on very rapid heating, while that of C^a and C^m only on slow heating. Slow solid-solid phase transition from C¹ to C^h was observed at ca 50°C. Each polymorph could be obtained as a stable form at room temperature and gave a quite different X-ray diffraction powder pattern. The interrelationships of the four forms have been clarified by differential scanning calorimetric and micriscopic measurements. When the melt of the complex is rapidly cooled, it converts into a glassy state, which is stable at room temperature. The glass transition temperature T₈ and the crystallizing temperature T_e are very close to each other at 52.5°C and 58.0°C, respectively.     

纳米薄膜材料的蓝光发射特性及其研究进展

蓝光发射是纳米半导体材料发光特性的一个重要研究方向.本文首先简要介绍了蓝光发射的物理机制,接着重点评述了几种主要纳米薄膜材料,如ZnO、GaN、CdS和Si纳米结构等,近3～5年内在蓝发光射特性方面所取得的最新研究进展.最后,对存在问题和发展前景进行了讨论与展望.     

Benzo-1,3,2-Dithiazol-2-YL and its Derivatives: A New Class of Donor Molecules for Highly Conducting Charge Transfer Complexes

Abstract

Benzo-1,3,2-dithiazol-2-yl and its derivatives form charge transfer complexes with tetracyanoquinodimethane; their powder conductivities are as high as 3 Ω^?1 cm^?1.     

Studies of Image Processing and Refractive Index in Blue Phase

The isotropic - blue phases - cholesteric phase transitions are studied in a thermotropic (COC) by image processing and refractive index measurements. Textures of blue phases are optically characterized as well as their transition points. The experimental investigation employed here is sensitive to detect changes in the structural configuration of blue phases as a consequence of our refractive index data. In this context the experimental results are presented and discussed.     

Mesomorphic Complexes of the Lanthanide Elements

Abstract

Mesomorphic lanthanide(III) complexes of salicylaldimine ligands have been synthesised. The effect upon the mesomorphic behaviour is discussed with variation of the counter-anion, number of alkoxy chains and the nature of the ligand framework. Complexes displaying either smectic or columnar mesophases have been realised.     

Spectroscopic Determination of Charge Formation Efficiency of Organic Photovoltaic Cells

The internal quantum efficiency (Φ_IQ) of an organic photovoltaic (OPV) cell is governed by plural processes, i.e., the carrier formation process at the D/A interface and the carrier transfer process toward the collector electrode. Then, Φ_IQ can be decomposed into the carrier formation (Φ_CF) and carrier transfer efficiencies (Φ_CT). By combination of femtosecond time-resolved and electrochemical spectroscopies, we determined absolute values of Φ_CF of F8T2/PC₇₁BM, P3HT/PCBM, and PTB7/PC₇₁BM solar cells. We found that Φ_CF at 400 nm of the F8T2/PC₇₁BM cell is higher than those of the P3HT/PCBM, and PTB7/PC₇₁BM cells, although Φ_IQ at 400 nm is the lowest.     

Uniform Alignment of Liquid Crystalline Cubic Blue Phase II via Rubbing Treatment

The uniform alignment of liquid crystalline cubic blue phase II (BPII) has been achieved using a conventional surface rubbing treatment. Through comparison of thick and thin cells of assembled rubbed glass, which were covered with commercially available polyimide (PI), we confirmed that rubbed surfaces play an important role in the fabrication of monodomain PBII. These well-aligned cubic BPII materials can be promising for photonics devices.     

蓝色聚苯乙烯胶体晶体膜的制备及其呈色机理研究

以粒径为340±10 nm的单分散聚苯乙烯微球为原料,采用垂直沉积法制备了蓝色聚苯乙烯胶体晶体膜.通过研究不同组装容积对聚苯乙烯胶体晶体膜的微观形貌和宏观呈色性能的影响规律,探索制备大面积蓝色聚苯乙烯胶体晶体膜的方法.结果表明,当聚苯乙烯乳液浓度为0.1wt;,干燥温度为40℃,自组装容积为50 mL时,所得聚苯乙烯胶体晶体膜呈现高质量的密排六方结构,宏观上呈现均匀明亮的蓝色,该蓝色具有一定的角度依赖性.研究发现,采用该方法制备聚苯乙烯胶体晶体膜时,在基片上和玻璃器皿壁上同时进行着垂直自组装.同时,在玻璃器皿底部也进行着蒸发自组装,形成了较大面积的蓝色聚苯乙烯胶体晶体膜,有望为制备大面积聚苯乙烯胶体晶体膜提供新的方法.     

Crystal Structures of Hexameric and Dimeric Complexes of Lithioisobutyrophenone

Abstract The crystal structures of two unsolvated hexameric complexes and one N,N,N′,N′-tetramethyl-1,2-ethanediamine (TMEDA)-solvated dimeric complex of the lithium enolate of 2-methyl-1-phenyl-1-propanone (lithioisobutyrophenone, LiIBP) are reported. The unsolvated LiIBP complexes crystallize from benzene-d ₆ to yield two different types of crystals that have similar structures: one in the triclinic space group P-1 with a = 10.7944(7), b = 11.9350(8), c = 12.0956(8) ?; α = 117.5560(10), β = 100.8090(10), γ = 92.3030(10)° and Z = 1 and a second in the monoclinic space group C2/c with a = 17.6011(11), b = 14.7389(9), c = 21.0943(13) ?; β = 105.2510(10)° and Z = 4. The two LiIBP hexamers differ slightly in the conformations of the enolate moieties around the Li₆O₆ core. The hexamer in both the triclinic as well as the monoclinic polymorph is located on a crystallographic inversion center that each generates the other half of the cluster. The TMEDA-solvated LiIBP dimer crystallizes from hexanes in the monoclinic space group C2/c with a = 11.8472(6), b = 14.8268(7), c = 19.2719(9) ?; β = 98.8480(10)° and Z = 4. The center of the dimer is located on a crystallographic C2 axis. These complexes represent only the second reported crystal structures of either an unsolvated hexamer or a solvated dimer of a lithium enolate of a simple monocarbonyl ketone. Graphical Abstract The X-ray crystal structures of two unsolvated hexameric and one N,N,N′,N′-tetramethyl-1,2-ethanediamine (TMEDA)-solvated complexes of the lithium enolate of 2-methyl-1-phenyl-1-propanone (lithioisobutyrophenone, LiIBP) are reported. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Structural Studies of 1:1 Quinone-Hydroquinone Complexes

The structures of the 1:1 quinone-hydroquinone complexes of 2-phenyl and of 2-(4′-chloro) phenylbenzoquinone have been studied by X-ray methods. A superficial study would indicate that the quinhydrones are centrosymmetric and belong to the space group P2₁/c. However, other evidence indicates that the true crystal structure may belong to either the space group P2₁ or to Pc, or that the crystal may contain regions that would coresspond to each of these two non-centrosymmetric space groups. Some possible consequences of such a structural arrangement are briefly discussed.     

8-羟基喹啉金属配合物的制备与提纯

对以8-羟基喹啉为配位体的金属配合物合成过程中几个重要的影响因素进行研究,发现反应溶液的浓度、合成反应的时间、反应体系的pH值、反应温度等因素对8-羟基喹啉金属配合物的产率以及发光性能有很大的影响.结果表明:当8-羟基喹啉乙醇溶液浓度为80 g/L,反应体系pH值为7.14,温度为70 ℃,反应时间为3 h时,Alq3的产率最高;反应体系pH值为10,温度为50 ℃,反应时间为1 h,Liq的产率最高;pH值为8,温度为70 ℃,反应时间为1 h,Znq2的产率最高.     

Optical Rotatory Dispersion Measurements of the Liquid Crystalline Blue Phases in Thick Layers

The results of optical rotatory dispersion (ORD) measurements in liquid crystalline blue phases (BP) are reported for pure compounds and mixtures. They have been performed on polycrystalline samples (thick layers). Two features distinguish their spectra from those obtained from liquid single crystals:

(1) The magnitude of the rotation is much smaller, and

(2) no sharp anomalous ORD region is present.

The spectra possess a weak, broad anomalous region. Their sign and wavelength dependence follows the sense and pitch of the cholesteric helix. ORD experiments with mixtures of the same cholesteric esters with a nematic substance yield results typical of well oriented samples. The spectra exhibit larger rotation angles and a significantly smaller anomalous region.     

Sm2O3/TiO2对亚甲基蓝染料的光催化降解行为研究

采用浸渍法制备Sm2O3掺杂TiO2的负载型光催化剂Sm2O3/TiO2,考察其在紫外可见光区对亚甲基蓝的光降解行为.利用XRD、N2吸附、SEM、TEM、XPS和ICP-OES等手段表征Sm2O3/TiO2样品,考察Sm2 O3掺杂量和亚甲基蓝浓度对亚甲基蓝紫外光降解活性的影响和催化剂Sm2O3/TiO2的催化稳定性.结果表明,Sm2O3/TiO2对亚甲基蓝的紫外光降解活性高于TiO2,这归因子掺杂Sm2O3引起TiO2的晶体缺陷.这种晶体缺陷作为光生电子和空穴的陷阱实现光生电子-空穴对的有效分离,从而提高Sm2O3/TiO2的光催化活性.Sm2O3/TiO2对亚甲基蓝的光降解活性随着Sm2O3掺杂量的增加先增大后减小,随着亚甲基蓝浓度的增大而减小.Sm2 O3掺杂量5.0wt;的Sm2O3/TiO2对亚甲基蓝紫外光降解的7次循环实验未出现明显失活.