Institute for Crystallography and Structural Physics , Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Staudtstr. 3 , 91058 Erlangen , Germany.
Center for Nanoanalysis and Electron Microscopy (CENEM) and Interdisciplinary Center for Nanostructured Films (IZNF) , Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) , Cauerstr. 3 , 91058 Erlangen , Germany.
Langmuir. 2019 Oct 22;35(42):13578-13587. doi: 10.1021/acs.langmuir.9b00944. Epub 2019 Oct 7.
Antisolvent precipitation (AP) is a low-cost and less-invasive preparation alternative for organic nanoparticles compared to top-down methods such as high-pressure homogenization or milling. Here we report on particularly small organic nanoparticles (NPs) prepared by AP. It has been found for various materials that these NPs in their liquid state exhibit a significant degree of molecular order at their interface toward the dispersion medium including ubiquinones (coenzyme Q10), triglycerides (trimyristin, tripalmitin), and alkanes (tetracosane). This finding is independent of the use of a stabilizer in the formulation. While this is obviously a quite general interfacial structuring effect, the respective structural details of specific NPs systems might differ. Here, a detailed structural characterization of very small liquid coenzyme Q10 (Q10) NPs is presented as a particular example for this phenomenon. The Q10 NPs have been prepared by AP in the presence of two different stabilizers, sodium dodecyl sulfate (SDS) and pentaethylene glycol monododecyl ether (CE), respectively, and without any stabilizer. The NPs' size is initially analyzed by photon correlation spectroscopy (PCS). The SDS-stabilized Q10 NPs have been studied further by differential scanning calorimetry (DSC), small-angle X-ray and neutron scattering (SAXS, SANS), wide-angle X-ray scattering (WAXS), and cryogenic transmission electron microscopy (CryoTEM). A simultaneous analysis of SAXS and contrast variation SANS studies revealed the molecular arrangement within the interface between the NPs and the dispersion medium. The Q10 NPs stabilized by SDS and CE, respectively, are small (down to 19.9 nm) and stable (for at least 16 months) even when no stabilizer is used. The SDS-stabilized Q10 NPs reported here, are therewith, to the best of our knowledge, the smallest organic NPs which have been reported to be prepared by AP so far. In particular, these NPs exhibit a core-shell structure consisting of an amorphous Q10 core and a surrounding shell, which is mainly composed of oriented Q10 molecules and aligned SDS molecules. This structure suggests a significant amphiphilic behavior and a rather unexpected stabilizing role of Q10 molecules.
抗溶剂沉淀（AP）是一种低成本、低侵入性的制备方法，与高压均质化或研磨等自上而下的方法相比，可以制备有机纳米颗粒。在这里，我们报告了通过 AP 制备的特别小的有机纳米颗粒（NPs）。已经发现，对于各种材料，这些在其液体状态下的 NPs 在其与分散介质的界面处表现出显著程度的分子有序性，包括泛醌（辅酶 Q10）、甘油三酯（肉豆蔻酸三酯、棕榈酸三酯）和烷烃（二十四烷）。这一发现与配方中使用稳定剂无关。虽然这显然是一种相当普遍的界面结构效应，但特定 NPs 系统的各自结构细节可能不同。在这里，作为这种现象的一个特定示例，详细介绍了非常小的液体辅酶 Q10（Q10）NPs 的结构特征。通过 AP 在两种不同稳定剂（十二烷基硫酸钠（SDS）和五乙二醇单十二烷基醚（CE））的存在下以及没有任何稳定剂的情况下分别制备了 Q10 NPs。通过光子相关光谱（PCS）最初分析 NPs 的尺寸。进一步研究了 SDS 稳定的 Q10 NPs 的差示扫描量热法（DSC）、小角 X 射线和中子散射（SAXS、SANS）、广角 X 射线散射（WAXS）和低温透射电子显微镜（CryoTEM）。同时分析 SAXS 和对比变化 SANS 研究揭示了 NPs 与分散介质之间界面内的分子排列。分别由 SDS 和 CE 稳定的 Q10 NPs 很小（小至 19.9nm）且稳定（至少 16 个月），即使没有使用稳定剂。据我们所知，这里报道的 SDS 稳定的 Q10 NPs 是迄今为止通过 AP 制备的最小的有机 NPs。特别是，这些 NPs 表现出核壳结构，由无定形的 Q10 核和周围的壳组成，壳主要由取向的 Q10 分子和排列的 SDS 分子组成。这种结构表明了显著的两亲性行为和 Q10 分子出人意料的稳定作用。
