Synthesis, crystal structure and optoelectronic properties of a new unsymmetrical photochromic diarylethene

A new unsymmetrical photochromic diarylethene, 1-(2-methyl-5-phenyl-3-thienyl)-2-[2-methyl-5-(3-trifluoromethylphenyl)-3-thienyl]perfluorocyclopentene (1a), was synthesized and its structure was determined by single-crystal X-ray diffraction analysis. Its optical and electrochemical properties, including photochromic reactivity both in solution and in the solid state (PMMA film and the single-crystalline phase), fluorescence and electrochemical properties were investigated in detail. The compound showed excellent photochromism even in the single-crystalline phase by photo-irradiation. In acetonitrile, the open-ring isomer of diarylethene 1 exhibited relatively strong fluorescence at 470nm when excited at 300nm, and its emission intensity decreased along with the photochromism upon irradiation with 313nm light. Its closed-ring isomer showed almost no fluorescence. The electrochemical properties of diarylethene were investigated by performing cyclic voltammetry experiment and its HOMO and LUMO energy level were calculated.     

仙茅素A的全合成

首次报道了仙茅素A[2,5-双(3,4-二羟基苯基)呋喃-3-甲醛]的全合成。以3,4-二甲氧基苯乙酮为起始原料,经Paal-Knorr反应,选择性溴代及还原等反应合成了仙茅素A,其结构经1H NMR,13C NMR和ESI-MS表征。     

基于铝离子掺杂二氧化钛薄膜的染料敏化太阳能电池的光电性能

采用水热法制备出Al3+掺杂二氧化钛薄膜,通过玻璃棒涂于导电玻璃上,在450°C的温度下烧结并将其用N3染料敏化制成染料敏化太阳能电池(DSSCs).通过X射线光电子能谱(XPS)、X射线衍射(XRD)、扫描电镜(SEM)及DSSCs测试系统对其进行了测试表征,研究了Al3+掺杂对TiO2晶型及染料敏化太阳能电池的光电性能影响.XPS数据显示Al3+成功掺杂到了TiO2晶格内,由于Al3+的存在,对半导体内电子和空穴的捕获及阻止电子/空穴对的复合发挥重要作用.莫特-肖特基曲线显示掺杂Al3+后二氧化钛平带电位发生正移,并导致电子从染料注入到TiO2的驱动力提高.DSSCs系统测试结果表明,Al3+掺杂的TiO2薄膜光电效率达到6.48%,相对于无掺杂的纯二氧化钛薄膜光电效率(5.58%),其光电效率提高了16.1%,短路光电流密度从16.5mA·cm-2提高到18.2mA·cm-2.     

小球与均质定轴杆的碰撞(续)

从碰撞过程中形变与能量的转换关系出发,采用弹性度的概念,提供了解决小球与定轴杆一般非弹性碰撞问题的一种解法.     

New photochromic diarylethenes bearing a pyridine moiety

A new class of diarylethenes bearing a pyridine unit has been firstly developed and their properties such as photochromism, fatigue resistance, and fluorescence have been discussed. The pyridine unit was connected directly to the central cyclopentene ring as one aryl moiety and availably participated in the photoinduced cyclization reaction even in the crystalline phase. All of these diarylethenes exhibited excellent photochromism, remarkable fatigue resistance, and notable fluorescence photoswitches both in solution and in poly(methylmethacrylate) films. Moreover, the different substituents had a significant effect on their properties. The results indicated that the electron-donating substituent could significantly enhance the cyclization quantum yield and depress the cycloreversion quantum yield while the electron-withdrawing group had a notable contribution to the cycloreversion quantum yield and fluorescence quantum yield for these diarylethenes.     

A proton and optic dual-control molecular switch based on photochromic diarylethene bearing a rhodamine unit

A novel fluorescent switch based on rhodamine B and photochromic diarylethene, 1-[2-methyl-5-(4-methoxylphenyl)-3-thienyl]-2-[2-methyl-5-(4-rhodamine B hydrazine-Schiff base-phenyl)-3-thienyl]perfluorocyclopentene (1), has been successfully synthesized through the condensation of rhodamine B hydrazine and 1-[2-methyl-5-(4-methoxylphenyl)-3-thienyl]-2-[2-methyl-5-(4-formylphenyl)-3-thienyl]perfluorocyclopentene. UV and FL measurements reveal that the compound exhibits good photochromic properties responsive to proton and optic dual inputs. Upon irradiation with 297 nm light, the colorless solution of compound 1 turns blue, while the blue solution becomes colorless after irradiated with visible light (λ>450 nm). Furthermore, upon an addition of H⁺, the fluorescence resonance energy transfers from the rhodamine unit (FRET donor) to the closed-ring diarylethene unit (FRET acceptor), although no energy transfer occurs when the diarylethene is in the open-ring form. The emission intensity of the rhodamine can be modulated with proton and UV/vis light and molecular-level signal communication has been constructed, indicating high potentials of the compound in molecular switches or naked eye recognition systems.     

Growth,Structure,and Spectroscopic Characteristics of the Nd^3＋：LiGd（WO4）2 Crystal

The Nd3+:LiGd(WO4) 2 crystal with dimensions of 25mm×28mm×16mm was grown by the top-seeded solution growth method from the 60 mol% Li2W2O7 flux. LiGd(WO4) 2 crystallizes in the tetragonal system with space group I41/a(C4h6) and cell parameters: a = 5.1986 and c = 11.2652 . The hardness is about 5.0 Mohs' scale. The specific heat is 0.40 J·g-1·K-1 at 50 oC. The thermal expansion coefficients for a-and c-axes are 1.314×10-5 and 2.052×10-5 K-1,respectively. The room-temperature polarized absorption and emission spectra and the fluorescence decay curve was measured. The parameters of oscillator strengths,the spontaneous transition probabilities,the fluorescence branching ratios,the radiative lifetimes,and the emission cross sections have been investigated based on Judd-Ofelt theory and Füchtbauer-Ladenburg method. The absorption cross-section is 5.19×10-20 cm2 at 805 nm for π-polarization and its line width is 15 nm;the emission cross section is 1.726×10-19 cm2 at 1060.5 nm for π-polarization. The fluorescence and radiative lifetimes are 86 and 158 μs,respectively. The fluorescence quantum efficiency is 54.43%.     

Neutral desorption extractive electrospray ionization mass spectrometry for fast screening sunscreen agents in cream cosmetic products

High throughput analysis of sunscreen agents present in cream cosmetic has been demonstrated, typically 2 samples per minute, using neutral desorption extractive electrospray ionization mass spectrometry (ND-EESI-MS) without sample pretreatment. For the targeted compounds such as 4-Aminobenzoic acid and oxybenzone, ND-EESI-MS method provided linear signal responses in the range of 1-100 ppb. Limits of detection (LOD) of the method were estimated at sub-ppb levels for the analytes tested. Reasonable relative standard deviation (RSD = 8.4-16.0%) was obtained as a result of 10 independent measurements for commercial cosmetics samples spiked with each individual sunscreen agents at 1-10 ppb. Acceptable recoveries were achieved in the range of 87-116% for direct analysis of commercial cream cosmetic samples. The experimental data demonstrate that ND-EESI-MS is a useful tool for high throughput screening of sunscreen agents in highly viscous cream cosmetic products, with the capability to obtain quantitative information of the analytes.