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首页> 外文期刊>Journal of Imaging Science and Technology >Spectral Properties and STM Imaging of Monolayer Cyanine Dye Aggregates Self-Assembled on Ag(111) Film
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Spectral Properties and STM Imaging of Monolayer Cyanine Dye Aggregates Self-Assembled on Ag(111) Film

机译：自组装在Ag（111）膜上的单层花菁染料聚集体的光谱性质和STM成像

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摘要

By using a two-stage Ar-ion sputter deposition of Ag/Au on mica, a highly oriented Ag(111) film with high planarity has been prepared. On this film surface, we have observed the occurrence of self-assembled, two-dimensional dye aggregates of cationic cyanine dyes with halide counter ions. Reported as typical examples in this article are 1,1′-diethyl-2,2′-cyanine, which forms a J-aggregate with a spectrally well-defined aggregate structure, and 1,1′-diethyl-2,2′-carbocyanine assembled predominantly as H-aggregates. Substitutional conversion of a native oxide monolayer, associated with the as-grown but air-exposed Ag(111) film, by halide counter anions produces a pseudo-silver-halide monolayer that both chemically and structurally resembles the silver halide (111) surface, thus providing the major driving force for the self-assembly of monolayer dye aggregates. Scanning tunneling microscopy (STM) images of these dye aggregates have been obtained at negative sample biases of around - 300 mV or more, suggesting that the tunneling process likely involves the occupied π-electrons of dye molecules. In accordance with the molecular exciton theory, the image of the H-aggregate exhibits a parallel column structure, with each column consisting of planar dye molecules stacked plane-to-plane at a slip angle no less than 60°. The J-aggregate is imaged as a unique ring-like structure, which is reasonably associated with an intricate two-dimensional network of dye molecules, with small slip angles of around 20°. The halide-covered Ag(111) film thus offers a simple, convenient system for modeling various dye adsorptions on silver halides, compatible with both STM and conventional spectroscopy methods.
机译：通过在云母上进行两阶段的Ar / Au离子溅射Ag / Au沉积，制备了具有高平面度的高取向Ag（111）膜。在此薄膜表面上，我们观察到了带有卤化物抗衡离子的阳离子花青染料的自组装二维染料聚集体的出现。在本文中报道的典型例子是1,1'-二乙基-2,2'-花菁，它形成具有光谱清晰定义的聚集体结构的J聚集体，以及1,1'-二乙基-2,2'-碳花青素主要以H聚集体的形式组装。与自然生长的但暴露于空气中的Ag（111）膜相关联的天然氧化物单层被卤化物抗衡阴离子取代转化后，生成的假卤化银单层在化学和结构上均类似于卤化银（111）表面，因此为单层染料聚集体的自组装提供了主要驱动力。这些染料聚集体的扫描隧道显微镜（STM）图像已在约-300 mV或更高的负样品偏压下获得，表明隧道过程可能涉及染料分子的π电子占据。根据分子激子理论，H聚集体的图像显示出平行的列结构，每列由平面染料分子以不小于60°的滑角面对面堆叠而成。 J聚集体被成像为独特的环状结构，该结构合理地与复杂的二维二维染料分子网络相关联，并具有约20°的小滑移角。因此，覆盖有卤化物的Ag（111）膜提供了一种简单，方便的系统，用于模拟各种染料在卤化银上的吸附，与STM和常规光谱法兼容。

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