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首页> 外文期刊>Chemistry: A European journal >Efficient charge injection from the S-2 photoexcited state of special-pair mimic porphyrin assemblies anchored on a titanium-modified ITO anode
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Efficient charge injection from the S-2 photoexcited state of special-pair mimic porphyrin assemblies anchored on a titanium-modified ITO anode

机译：从锚定在钛修饰的ITO阳极上的特殊对模拟卟啉组件的S-2光激发态有效注入电荷

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摘要

A novel surface fabrication methodology has been accomplished, aimed at efficient anodic pbotocurrent generation by a photoexcited porphyrin on an ITO (indium-tin oxide) electrode. The ITO electrode was submitted to a surface sol-gel process with titanium n-butoxide in order to deposit a titanium monolayer. Subsequently, porphyrins were assembled as monolayers on the titanium-treated ITO surface via phosphonate, isophthalate, and thiolate groups. Slipped-cofacial porphyrin dimers, the so-called artificial special pair at the photoreaction center, were organized through imidazolyl-to-zinc complementary coordination of imidazolylporphyrinatozinc(II) units, which were covalently immobilized by ring-closing olefin metathesis of allyl side chains. The modified surfaces were analyzed by means of X-ray photoelectron spectroscopy. Photoirradiation of the porphyrin dimer generated a large anodic photocurrent in aqueous electrolyte solution containing hydroquinone as an electron sacrificer, due to the small reorganization energy of the dimer. ne use of different linker groups led to significant differences in the efficiencies of anodic photocurrent generation. The apparent flat-band potentials evaluated from the photocurrent properties at various pH values and under biased conditions imply that the band structure of the ITO electrode is modified by the anchoring species. The quantum yield for the anodic photocurrent generation by photoexcitation at the Soret band is increased to 15%, a surprisingly high value without a redox cascade structure on the ITO electrode surface, while excitation at the Q band is not so significant. Extensive exploration of the photocurrent properties has revealed that hot injection of the photoexcited electron from the S-2 level into the conduction band of the ITO electrode takes place before internal conversion to the S-1(*) state, through the strong electronic communication of the phosphonyl anchor with the sol-gel-modified ITO surface.
机译：已经完成了一种新颖的表面制造方法，该方法旨在通过在ITO（铟锡氧化物）电极上的光激发卟啉来有效地产生阳极电流。 ITO电极用正丁醇钛进行表面溶胶-凝胶工艺，以沉积钛单层。随后，卟啉通过膦酸酯基，间苯二甲酸酯基和硫醇酸酯基团组装成钛处理过的ITO表面上的单层。滑面卟啉二聚体，即光反应中心的所谓人工特殊对，是通过咪唑基卟啉酮锌（II）单元的咪唑基与锌的互补配位而组织的，后者通过烯丙基侧链的闭环烯烃复分解共价固定。借助于X射线光电子能谱分析改性的表面。卟啉二聚体的光辐照由于二聚体的重组能小，在含有氢醌作为电子牺牲剂的电解质水溶液中产生了较大的阳极光电流。使用不同的连接基团会导致阳极光电流产生效率的显着差异。根据在各种pH值和偏置条件下的光电流特性评估的表观平坦带电势暗示着ITO电极的能带结构被锚固物质所修饰。在Soret能带上通过光激发产生的阳极光电流的量子产率提高到15％，这是一个令人惊讶的高值，在ITO电极表面上没有氧化还原级联结构，而在Q能带上的激发并不那么重要。对光电流特性的广泛研究表明，通过内部的强电子通信，在内部转换为S-1（*）状态之前，将光激发电子从S-2能级热注入到ITO电极的导带中。膦酰基锚固剂具有溶胶-凝胶改性的ITO表面。

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