Optical and electroluminescent properties of conjugated polyrotaxanes

Conjugated polyrotaxanes are conjugated polymeric semiconductors engineered at a supramolecular level by threading the conjugated moiety into molecular macrocycles, such as cyclodextrins (CD). CD-threaded rotaxanes thus provide a class of model compounds with reduced interchain interactions which enable us to explore the influence of such interactions on the fundamental photophysics of conjugated semiconductors. CD rotaxination also endows these materials with additional sites for functionalization, thus resulting in extremely versatile structures. Our current understanding of the photophysics of these materials is reviewed, both in solid/liquid solutions and in neat films, as a function of the relevant parameters, such as the threading ratio and the concentration, and with the help of rotaxanes incorporating a variety of different backbones.     

Highly Phototoxic Transplatin-Modified Distyryl-BODIPY Photosensitizers for Photodynamic Therapy

We report the synthesis of the first transplatin-BODIPY conjugates for application in photodynamic therapy (PDT). The distyryl BODIPYs containing two iodine atoms were designed to absorb in the red region, easily undergo intersystem crossing for efficient singlet oxygen generation, and additionally offer the possibility for coordination with mono-activated transplatin. We were able to demonstrate that coordination of the BODIPYs with a mono-activated transplatin increases the phototoxic index of the photosensitizers significantly, giving rise to highly phototoxic distyryl BODIPY derivatives, of which one was shown to have the highest ever reported phototoxic index against any cell line. Furthermore, the photophysical mechanism of singlet oxygen generation in distyryl BODIPYs undergoing intramolecular charge transfer was studied experimentally and using time-dependent density functional theory.     

Characterization of Fluorescent Proteins with Intramolecular Photostabilization**

Genetically encodable fluorescent proteins have revolutionized biological imaging in vivo and in vitro. Despite their importance, their photophysical properties, i. e., brightness, count-rate and photostability, are relatively poor compared to synthetic organic fluorophores or quantum dots. Intramolecular photostabilizers were recently rediscovered as an effective approach to improve photophysical properties of organic fluorophores. Here, direct conjugation of triplet-state quenchers or redox-active substances creates high local concentrations of photostabilizer around the fluorophore. In this paper, we screen for effects of covalently linked photostabilizers on fluorescent proteins. We produced a double cysteine mutant (A206C/L221C) of α-GFP for attachment of photostabilizer-maleimides on the β-barrel near the chromophore. Whereas labelling with photostabilizers such as trolox, a nitrophenyl group, and cyclooctatetraene, which are often used for organic fluorophores, had no effect on α-GFP-photostability, a substantial increase of photostability was found upon conjugation to azobenzene. Although the mechanism of the photostabilizing effects remains to be elucidated, we speculate that the higher triplet-energy of azobenzene might be crucial for triplet-quenching of fluorophores in the blue spectral range. Our study paves the way for the development of fluorescent proteins with photostabilizers in the protein barrel by methods such as unnatural amino acid incorporation.     

Photochemistry and photophysics of poly(organophosphazenes) and related compounds: A review. III. Applicative aspects

In the third part of this review we report some applicative aspects of poly(organophosphazenes) in photochemical fields. In particular, the possible application of phosphazene polymers that contain azobenzene or spiropyran residues as photochromic macromolecules is outlined; the light-induced grafting of organic, carbon-backboned polymers onto polyphosphazene matrices, as a method of modifying both surface and bulk properties of these materials, is highlighted; and the potential application of cyclophosphazenes as photo-stabilizers for commercial organic polymers or as photoinitiators for radical polymerization of vinyl monomers is described.Parts I and II in this series appeared in this journal, Volume 4, Numbers 1 and 2, 1994, respectively.     

取代二（苯乙烯基）吡嗪类化合物发光行为的研究

本工作合成了三种具有不同取代基的二（苯乙烯基）吡嗪类化物，对它们在不同极性溶剂中的光物理及发光行为进行了研究，对带推电子基的二种含氮芪类化合物（Ⅰ），（Ⅱ）所以具有较强荧光发光行为以及对带硝基的该类化合物（Ⅲ）仅有很弱的萤光发光提出了看法，认为化合物（Ⅰ），（Ⅱ）存在着很弱的邻近效应和化合物（Ⅲ）因硝基的引入大大地促进了不同态间的邻近相互作用是导至本工作结果的主要原因。     

The Effect of H‐ and J‐Aggregation on the Photophysical and Photovoltaic Properties of Small Thiophene–Pyridine–DPP Molecules for Bulk‐Heterojunction Solar Cells

The performance of organic semiconductors in optoelectronic devices depends on the functional properties of the individual molecules and their mutual orientations when they are in the solid state. The effect of H‐ and J‐aggregation on the photophysical properties and photovoltaic behavior of four electronically identical but structurally different thiophene–pyridine–diketopyrrolopyrrole molecules is studied. By introducing and changing the position of two hexyl side chains on the two peripheral thiophene units of these molecules, their aggregation in thin films between H‐type and J‐type is effectively tuned, as evidenced from the characteristics of optical absorption, fluorescence, and excited state lifetime. The two derivatives that assemble into J‐type aggregates exhibit a significantly enhanced photovoltaic performance, up to an order of magnitude, compared to the two molecules that form H‐type aggregates. The reasons for this remarkably different behavior are discussed.     

新型含富勒烯的功能材料的研制和光物理研究（上）

本研究取得了一批有重要的基础科学意义和应用基础性的先进的创新性研究成果：（１）首次提出“以聚合物碳负离子为合成前体物质合成可溶性Ｃ_（６０）有机高分子衍生物”的合成路线和“用热失重分析确定含富勒烯的聚合物中Ｃ_（６０）含量”的方法;（２）首次合成了可溶性Ｃ_（６０）化学修饰的ＰＶＫ高分子光电导材料,从根本上解决了含Ｃ６０的共混高分子材料的相分离问题。同时发现该材料的光电导性能显著优于Ｃ６０掺杂的ＰＶＫ共混物;制备了第一个Ｃ６０高分子锂电池。在非均相体系中使用阴离子共聚方法合成含Ｃ６０的共聚高分子衍生物方面亦处于领先水平;（３）采用溶胶、凝胶法制成Ｃ６０／ＳｉＯ２全凝胶,观察到增强的宽带蓝移发光;（４）首次用物理喷束淀积制备富勒烯衍生物及富勒烯／高分子组合薄膜,观察到光电和超快光物理性能的明显优化,ＰＰＶ／Ｃ６０多层膜的光电导可提高４个量级以上,皮秒及飞秒非线性光学响应可优化一个量级;（５）首次在激光烧蚀质谱负离子通道中观测到“开笼”等新现象。从１９９４年至今,已在国内外学术期刊和国际会议上发表论文１２０余篇,其中国际ＳＣＩ核心期刊论文５０余篇     

New fluorescent monomers and polymers displaying an intramolecular proton‐transfer mechanism in the electronically excited state (ESIPT). IV. Synthesis of acryloylamide and diallylamino benzazole dyes and its copolymerization with MMA

Six new fluorescent monomers were synthesized by reaction of 2‐(5′‐amino‐2′‐hydroxyphenyl)benzazole derivatives with acryloyl chloride and allyl bromide. UV–vis and steady‐state fluorescence in solution were used to characterize its photophysical behavior. The monomers are fluorescent in the blue, green, yellow, and red region, with a large Stokes shift between 92 and 226 nm. A dual fluorescence ascribed to a conformational equilibrium in solution in the ground state dependent on the solvent polarity could be observed in the fluorescence emission spectra of the monomers. The radical polymerization of the monomers with methyl(methacrylate) allowed the production of fluorescent polymers in the blue–green region, with good optical and thermal properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

The Photophysics of Polythiophene Nanoparticles for Biological Applications

In this work the photophysics of poly(3-hexylthiophene) nanoparticles (NPs) is investigated in the context of their biological applications. The NPs, made as colloidal suspensions in aqueous buffers, present a distinct absorption band in the low-energy region. On the basis of systematic analysis of absorption and transient absorption (TA) spectra taken under different pH conditions, this band is associated with charge-transfer states generated by the polarization of loosely bound polymer chains and originating from complexes formed with electron-withdrawing species. Importantly, the ground-state depletion of these states upon photoexcitation is active even on microsecond timescales, thus suggesting that they act as precursor states for long-living polarons; this could be beneficial for cellular stimulation. Preliminary transient absorption microscopy results for NPs internalized within the cells reveal the presence of long-living species, further substantiating their relevance in biointerfaces.