Amphiphilic cyanine dyes in aqueous solution self-assemble into J-aggregates with diverse structures. In particular, the dye 3,3′-bis(3-sulfopropyl)-5,5′,6,6′-tetrachloro-1,1′-dioctylbenzimida-carbo-cyanine (C8S3) forms micrometer long double walled tubular J-aggregates with a uniform outer diameter of 13 ± 0.5 nm. Interestingly, these J-aggregates exhibit strong exciton delocalization and migration, similar to natural light harvesting systems. However, their structural integrity and hence their optical properties are very sensitive to their chemical environment as well as to mechanical deformation, rendering detailed studies on individual tubular J-aggregates difficult. We addressed this issue and examined a previously published route for their chemical and mechanical stabilization by in situ synthesis of a silica coating that leaves their absorbance and emission unaltered in solution. Here, we demonstrate that the silica shell with a thickness of a few nanometers is able to stabilize the tubular J-aggregates of C8S3 against changes of pH of solutions down to values where pure aggregates are oxidized, against drying under ambient conditions, and even against the vacuum conditions within an electron microscope. Dried silica–covered aggregates are brittle, as demonstrated by manipulation with a scanning force microscope on a surface. Transmission electron microscope images confirm that the thickness of the coatings is homogeneous and uniform with a thickness of less than 5 nm; scanning TEM energy dispersive X-ray spectroscopy confirms the chemical composition of the shell as SiO 2 ; and electron energy loss spectra could be recorded across a single freely suspended aggregate. Such a silica shell may not only serve for stabilization but also could be the base for further functionalization of the aggregates by either chemical attachment of other units on top of the shell or by inclusion during the synthesis.

中文翻译：

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单个管状 J 骨料通过二氧化硅封装稳定和硬化

水溶液中的两亲性花青染料自组装成具有不同结构的 J-聚集体。特别地，染料 3,3'-双(3-磺丙基)-5,5',6,6'-四氯-1,1'-二辛基苯并咪唑 (C8S3) 形成微米长的双壁管状 J-外径均匀为 13 ± 0.5 nm 的聚集体。有趣的是，这些 J 聚集体表现出强烈的激子离域和迁移，类似于自然光收集系统。然而，它们的结构完整性及其光学特性对其化学环境和机械变形非常敏感，这使得对单个管状 J 聚集体的详细研究变得困难。我们解决了这个问题，并通过原位合成二氧化硅涂层，使它们在溶液中的吸光度和发射保持不变，检查了之前公布的化学和机械稳定性路线。在这里，我们证明了厚度为几纳米的二氧化硅壳能够稳定 C8S3 的管状 J 聚集体，以防止溶液 pH 值变化降至纯聚集体被氧化的值，防止在环境条件下干燥，甚至抵抗电子显微镜内的真空条件。干燥的二氧化硅覆盖的聚集体是脆的，正如在表面上用扫描力显微镜操作所证明的那样。透射电镜图像证实涂层厚度均匀、均匀，厚度小于5纳米；扫描 TEM 能量色散 X 射线光谱证实壳的化学成分为 SiO 2 ；并且可以在单个自由悬浮的聚集体上记录电子能量损失谱。这种二氧化硅壳不仅可以起到稳定作用，而且还可以作为通过在壳顶部化学连接其他单元或在合成过程中包含来进一步功能化聚集体的基础。