Supramolecular Assemblies of Thioflavin T with Cucurbiturils: Prospects of Cooperative and Competitive Metal Ion Binding

Of late, molecular-recognition-guided supramolecular assembly and its relevance in the development of highly stable and active photofunctional materials have drawn much attention. In this review, the non-covalent interaction of a biologically important dye, thioflavin T (ThT), with cucurbituril macrocycles, especially, cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8), and the response of the resulting molecular assemblies towards the metal ions have been discussed. The interaction of ThT with CB7 leads to significant enhancement in the fluorescence yield, lifetime and modifications in the spectral features of ThT. These changes are assigned to the formation of 1 : 1 and 2 : 1 (CB7⋅ThT) complexes. However, with CB8 a distinct evolution of a hitherto unexplored strong excimer emission band having maximum at 570 nm is observed. The strong ion–dipole interactions provided by the carbonyl portals of the CB8 adequately support the stabilization of two π-stacked ThTs, both in 1 : 2 (CB8⋅ThT) and 2 : 2 stoichiometric ratio. In case of the 1 : 1 (CB7⋅ThT) system, the metal ion addition leads to the usual competitive binding interaction and decreases the fluorescence intensity. However, the addition of the same metal ion to the 2 : 1 (CB7⋅ThT) complex results in a novel cooperative metal ion binding to the complex, leading to the formation of a highly fluorescent supramolecular capsule. Further addition of amantadine hydrochloride induces rupture of the capsular complex, projecting potential application in targeted drug delivery. The 2 : 2 (CB8⋅ThT) complex responds to the metal ion presence in a competitive way, which allows demonstration of a fluorescence on–off mechanism.     

CNTs in Optoelectronic Devices: New Structural and Photophysical Insights on Porphyrin‐DWCNTs Hybrid Materials

The preparation and physical characterization of diverse porphyrin‐derived double‐walled carbon nanotubes (DWCNTs) conjugates are described. A porphyrin molecule is covalently linked and physically adsorbed to COOH‐derived DWCNTs. The photophysical properties of all porphyrin‐CNTs derivatives are studied in solution and in polymeric matrices. Definitive experimental evidence for photoinduced electron and/or energy transfer processes involving the porphyrin chromophores and the CNT wall is not obtained, but solid‐state UV‐vis absorption profiles display electronic transitions fingerprinting J‐ and H‐ type aggregates, where porphyrin molecules intermolecularly interact “head‐to‐tail” and “face‐to‐face”, respectively. In parallel, molecular modeling based on force‐field simulations is performed to understand the structure of the porphyrin‐CNTs interface and the nature of the interactions between the porphyrins and the DWCNTs. Finally, multilayered ‐ type devices are fabricated with the aim of investigating the interaction of the porphyrin‐derived DWCNTs with poly(3‐hexylthiophene)‐pyrene matrices containing small amounts of 1‐[3‐(methoxycarbonyl)propyl]‐1‐phenyl‐[6.6]C₆₁.     

Synthesis,electroluminescence, and photovoltaic cells of new vinylene‐copolymers with 4‐(anthracene‐10‐yl)‐2,6‐diphenylpyridine segments

Three new soluble vinylene‐copolymers F , C, and P that contain 4‐(anthracene‐10‐yl)‐2,6‐diphenylpyridine as common segment and fluorene, carbazole, or phenylene, respectively, as alternating segment were prepared by Heck coupling. The glass transition temperature was high for F and C (110 and 117°C), whereas was lower than 25°C for P . The polymers were stable up to ～ 300°C. They emitted blue–green light with maximum located at wavelength of 456–550 nm, which was of the order F < C < P . The photoluminescence quantum efficiency in THF solution was ～ 30% for F and P and only 5% for C . All three copolymers were used as active layers for polymer light emitting diodes (PLEDs) and organic photovoltaic cells. The double PLEDs with configuration of indium‐tin oxide (ITO)/poly(ethylenedioxythiophene (PEDOT) : poly(styrenesulfonate)(PSS)/Copolymer F , C , or P /TPBI(1,3,5‐tris(2‐N‐phenylbenzimidazolyl)benzene)/Ca/Al were fabricated. Copolymer P emitted green light with maximum brightness of 28 cd/m² and a current yield of 0.85 cd/A. Organic photovoltaics with the configuration of ITO/PEDOT : PSS/Copolymer and [6,6]‐phenyl‐C61‐butyric acid methyl ester blend (1 : 1) /Ca/Al were also fabricated. Copolymer P showed the highest power conversion efficiency of 0.034%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Tunable near‐infrared optical properties based on poly(methyl methacrylate)–oxide waveguide materials

In this study, two classes of low‐loss optical planar waveguides were prepared from trialkoxysilane‐capped poly(methyl methacrylate) (PMMA)–silica and PMMA–titania hybrid materials, respectively. The prepared hybrid films had very uniform structure and surface planarity. The incorporation of the silica or titania segments into the acrylic polymer matrix reduced the intermolecular interaction and thus induced an increase in anharmonicity of the C‐H bond in the acrylic segment. Therefore, the third harmonic stretching vibration absorption of the C‐H bond was red‐shifted and resulted in a tuning of near‐infrared (NIR) optical absorption. The optical loss of the studied waveguides was reduced from 0.65 dB/cm of the PMMA waveguide to 0.26 and 0.28 dB/cm with increasing the silica and titania content in the hybrid materials, respectively. The reduction of the C‐H number density and shifting of the NIR absorption spectra accounted for the relationship between the optical loss and the inorganic oxide content. The increased anharmonicity through the incorporation of the inorganic moiety in the hybrid materials provides another approach for tuning the NIR optical properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1224–1228, 2005     

卟啉类第二代光敏剂的发展

本文对目前用于光动力治疗的以卟啉为基础的第二代光敏剂进行了综述，这些光敏剂中的大部分已进入临床或临床前试验，光物理性质研究表明它们是很有前途的光动力药物。本文同样介绍了连接生物分子和硼烷的卟啉衍生物，作为光序剂，它们具有非常光明的前途。     

咔唑与N-烷基咔唑光物理行为的差异

已知甲基、乙基咔唑等咔唑的衍生物与对位苯二甲酸二甲酯(DMTP)和邻位苯二甲酸二甲酯(DMP)可以形成激基复合物,但是咔唑与DMTP或DMP相互作用时观察不到激基复合物的荧光。众所周知,DMTP和DMP都是比较弱的电子受体,所以我们采用接受电子比较强的二氰基苯(DCB)作为受体,以便观察咔唑和咔唑衍生物之间的     

9-甲基蒽单体、二聚体和夹心面包对在硅胶上的光物理和光化学性质研究

研究了在硅胶表面上的9-甲基蒽和它的二聚体及其低温光解产物(夹心面包对)的荧光光谱,激发光谱和荧光寿命。发现了一个由二聚9-甲基蒽、三氯甲烷和真空下700℃活化硅胶形成的复合物。该复合物具有与单体和二聚体不同的特征激发光谱和发射光谱,低温下光照容易分解。当分解产物缓缓加热到室温,则复合物几乎完全可以再现。二聚体低温光解产物,夹心面包对,当其缓缓加热到室温,则完全变为单体蒽。     

Glycidyl methacrylate as a new host material for laser dyes

This article reports on the laser action of pyrromethene 597 and pyrromethene 567 doped in the novel solid polymeric matrix glycidyl methacrylate. Mirrorless lasing was observed when samples with diameters of 10 mm and lengths of 20 mm, with different dyes concentrations, were transversely pumped at 532 nm. The influence of the dye concentration on the laser measurements included the peak wavelengths, output energies, conversion efficiencies, and laser gains. Relatively high lasing efficiencies (up to ～ 60%) were obtained from these new polymeric materials with very good photostability, where a decrease of only 65% in the initial laser output energy was observed after pumping by 60,000 shots of 15 mJ at 10 Hz. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 59–63, 2007     

Micropatterning of polydiacetylene based on a photoinduced chromatic transition and mechanism study

A photoinduced chromatic transition from blue to red for the polydiacetylene 10,12‐pentacosadiynoic acid has been studied. This transition produces an obvious change in the ultraviolet–visible absorption and fluorescence emission spectra. A two‐dimensional micropattern has been realized on the basis of this change and imaged with a confocal fluorescence microscope. Detailed information on the mechanism of the chromatic transition has been obtained by the application of resonance Raman and Fourier transform infrared methods. The results indicate that the conformational change of alkyl side chains constricted by hydrogen‐bonded head groups imposes strain on the polymer backbone and finally leads to a drastic decrease in the π‐electron‐conjugation length. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 942–946, 2007