Organic nanodots based on the gathering of an exponentially increasing number of two-photon fluorophores on a dendritic platform of controlled size and symmetry represent a promising non-toxic alternative to quantum dots for (bio)imaging purposes. This modular route offers a number of advantages in terms of versatility but also raise a number of questions to be addressed. In particular, possible interactions between fluorophores, due to confinement effects, have to be taken into account. With this aim in mind we have investigated and compared the photophysical and two-photon absorption (TPA) properties of two series of organic nanodots of different geometries: spherical-like organic nanodots derived from a dendritic scaffold built from a cyclotriphosphazene core and dumbbell-like organic nanodots derived from a dendritic scaffold built from an elongated rod-like chromophore. The study provides evidence that the different topology and nature of the dendritic architecture lead to significant changes in photoluminescence characteristics as well as to subtle variations of the TPA efficiency. As a result, the dumbbell-like nanodots although less promising in terms of two-photon induced fluorescence (due to partial quenching of fluorescence efficiency) also demonstrate that improvement of the TPA efficiency can be achieved by playing on the nature and topology of the dendritic scaffold of the nanodots.
基于在尺寸和对称性受控的树突平台上聚集指数级增加的双光子荧光团的有机纳米点代表了用于(
生物)成像目的的量子点的一种有前途的无毒替代品。这种模块化路线在多功能性方面提供了许多优势,但也提出了许多需要解决的问题。特别是,必须考虑由于限制效应而导致荧光团之间可能发生的相互作用。考虑到这一目标,我们研究并比较了两种不同几何形状的有机纳米点的光物理和双光子吸收(
TPA)特性:由环三
磷腈核心构建的树枝状支架衍生的球形有机纳米点和哑铃状有机纳米点。有机纳米点源自由细长棒状发色团构建的树突支架。该研究提供的证据表明,树突结构的不同拓扑和性质会导致光致发光特性的显着变化以及
TPA 效率的细微变化。因此,哑铃状纳米点虽然在双光子诱导荧光方面前景不太乐观(由于荧光效率的部分猝灭),但也表明可以通过利用树突的性质和拓扑来提高
TPA 效率纳米点的支架。