Fast Optical Switching Using Oriented Cyanine Dye-Doped Nematic Liquid Crystal

A cyanine dye, 2-[7-（1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene）-1,3,5-heptatrienyl]-1,3,3-trimethyl-3H-indolium iodide （NK-125）, is doped in 4-cyano-4＇-pentylbiphenyl （5 CB）, and the mixture is sandwiched between two pieces of rubbed glass plates. The third-order nonlinear optical properties of the oriented NK-125-SCB layers are measured by the resonant femtosecond degenerate four-wave mixing （DFWM） technique at 760 nm. The third-order nonlinear optical susceptibility of one of the present samples is 5.5×10^-8 esu. The slow DFWM response of the NK-125-SCB layers due to a population grating is accelerated by the increasing laser power because of amplified spontaneous emission （ASE）. On the other hand, we do not observe a similar phenomenon for NK-125- polyethylene glycol （PEG-400）. Oriented NK-125 molecules in nematic liquid crystals must have very high ASE efficiency. Hence the population grating in a DFWM signal disappears within about 4 ps. It is expected that NK-125-SCB can be used as a material for very fast all-optical switching.     

Super-Resolution Recording by an Organic Photochromic Mask Layer

By using the super-resolution near-field structure （super-RENS） method, the super-resolution recording marks are obtained practically by an organic photochromic diarylethene mask layer, under much lower recording laser power of 0.45roW. The size of recording marks is decreased by 60% （from 1.6μm to 0.7μm） for a diarylethene （photo-mode） recording layer by the optical detection method （limited by optical diffraction）, or decreased by 97% （from 160Onto to 5Onto） for a heptaoxyl copper phthalocyanine （thermo-optical） recording layer, the latter is much smaller than the limitation of optical diffraction. In order to obtain a desirable result, a proper extent of photochemistry reaction in the mask layer is needed. Thus, the super-resolution recording marks can be obtained by adjusting the concentration of diarylethene in the mask layer, the recording laser power, and the moving speed of the sample disc.     

PBL教学法在大学有机化学实验教学中的研究与实践

以苯甲酸正丁酯的合成为案例,将以问题为基础的教学法(problem-based learning,PBL)应用于大学有机化学实验教学。实践表明,PBL教学法能够显著增强学生的实验兴趣,培养学生的综合实验能力,提高实验教学质量。     

电子转移途径中芳香族氨基酸的引入提高了细胞色素P450s的催化性能（英文）

细胞色素P450s是用于生物合成的多功能催化剂.在P450催化循环中,需要两个电子来还原血红素铁,并通过电子转移途径(eTPs)激活随后的还原,该步骤是反应的限速步骤.本文重新设计了巨大芽孢杆菌P450 BM3的e TPs,大幅提高了其催化性能.通过在P450 BM3的e TP中引入芳香族氨基酸,“最佳”变体P2H02(A399Y/Q403F)的催化效率比P450 BM3野生型催化效率提高了12.9倍(k_cat/K_M从65.8 L mol^-1 s^-1提高到913.5 L mol^-1 s^-1).分子动力学模拟和电子传递分析表明,在辅因子FMN和血红素之间引入的芳香族氨基酸可以显著提高电子转移速率和酶催化性能.同时,在电子传递途径中引入酪氨酸可以保护P450的催化中心,使其避免被氧化性中间产物所破坏,从而提高其催化效率.此外,引入芳香族氨基酸的策略被证明对其他P450(如CYP116B3)同样有效,改造后的酶表现出显著提高的催化效率.综上,本文策略有望拓展到其...     

Large Third-Order Optical Nonlinearity of a Novel Copper Phthalocyanine--Ferrocene Dyad

Third-order optical nonlinearity of a novel copper phthalocyanine-ferrocene dyad is measured by femtosecond forward degenerate four-wave mixing （DFWM） technique at 800 nm. The second-order hyperpolarizability of the novel copper phthalocyanine-ferrocene dyad is measured to be 1.74 ×10^-30 esu. This large and ultrafast thirdorder optical nonlinear response is mainly enhanced by the formation of intramolecular charge-transfer which can enhance the delocalized movements of the large π-electrons in the molecules.     

Large Third-Order Optical Nonlinearity and Fast Response of a Squarylium Dye

The third-order optical nonlinearities and responses of a squarylium dye, 2,4-di-3-guaiazulenyl-1,3-dihydroxycyclobutenediylium dihydroxide, in tetrahydrofuran （THF） solution and in polystyrene （PS） coating films are measured by the femtosecond degenerate four-wave mixing technique under resonant conditions. The molecular hyperpolarizability γ of the squarylium dye in the THF solution is determined to be 3.0 × 10^-29 esu at 764 nm, and its electronic component γe is determined to be 1.1 × 10^-29 esu. The third-order nonlinear susceptibility X^（3） of one of the present PS coating films containing the squarylium dye is as high as 3.1 × 10^-8 esu at 80Ohm, and its electronic component Xe^（3） is 1.3 × 10^-8 esu.     

以偶氮苯基团为周边取代基的锌酞菁的合成及光物理性质

合成了两种带有偶氮苯周边取代基的锌酞菁化合物,并对其进行了结构表征.与一般酞菁的吸收光谱相比,偶氮苯酞菁的UV-Vis光谱的B带吸收峰强度明显强于Q带.该类化合物在光照条件下表现出重复性较好的顺反异构化性质.Z-扫描结果表明,这类化合物的三阶非线性光学性能主要来源于酞菁的非线性折射率,且β位取代的酞菁的三阶非线性效应大于α位取代的,顺反异构对酞菁的三阶非线性光学性能的影响不大.     

有机化学实验“四位一体”教学模式的实践与探讨

以苯甲酸正丁酯的合成为例,介绍了有机化学实验"学、教、做、评"四位一体的教学模式。以导学、助学、促学、先学后教等方式促进学生自主学习的积极性;采用以问题为中心的教学方法,确立了以教师为主导、学生为主体的师生关系,充分发挥了学生的主观能动性;以开放性实验代替传统实验,充分培养了学生的实验技能和科学素养;对实验成绩进行综合立体评价,体现了评价的客观性和真实性。实践表明"四位一体"的教学模式不仅能够充分调动学生的主观能动性,培养学生的实验技能和兴趣,而且能有效地提高实验教学质量。     

Resonant Third-Order Optical Nonlinearities of Poly（methyl methacrylate） Films Containing J-Like Aggregates of a Thiadicarbocyanine Dye

The third-order optical nonlinearities and responses of poly（methyl methacrylate） （PMMA） coating films containing J-like aggregates of a thiadicarbocyanine dye, 3,3＇-diethyl-2,2＇-thiadicarbocyanine iodide （DTDC1）, are measured by degenerate four-wave mixing （DFWM） technique under resonant conditions. The temporal profiles of the DFWM signal of PMMA coating films containing J-like aggregates of DTDC1 are found to consist of three components： i.e., the coherent instantaneous nonlinear response （electronic response） and the two slow responses uqth decay time constants of about 0.8ps and about 7.0ps. The electronic component of the effective third-order nonlinear susceptibility, χc^（3）, of one of the present films is as high as about 2.1×10^-8 esu, and the figure of merit of third-order nonlinearity F （F=χ^（3）/α） is evaluated to be about 1.9 ×10^-13 esu cm at 850nm.     

鲁米诺偶联酞菁的合成及其光谱性质的研究

本文通过重氮化反应设计、合成了鲁米诺偶联的氨基锌酞菁,对其电子吸收光谱和荧光光谱性质进行了研究,结果表明该分子激发单重态可能以振动驰豫的方式使大部分能量耗散,鲁米诺偶联前后,氨基取代锌酞菁的荧光光谱有明显差别,为进一步开发酞菁类荧光光存储材料提供了理论依据.