Guignard Florian, Lattuada Marco
Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700 Fribourg, Switzerland.
Langmuir. 2015 Apr 28;31(16):4635-43. doi: 10.1021/acs.langmuir.5b00727. Epub 2015 Apr 15.
The preparation of anisotropic nanoparticles has drawn much attention in the literature, with most of the efforts being dedicated to convex particles. In this work, instead, we present a reliable method to synthesis silica nanobowls with one well-defined opening, covering a broad range of sizes. The nanobowls have been obtained from asymmetrically functionalized silica-polymer Janus nanodumbbells, used as templates, by removing of the polymer. Polystyrene seeds having different sizes as well as surface chemistry have been used as starting material in a two-step seeded emulsion polymerization, which leads to polymer nanodumbbells. These dumbbells are also asymmetrically functionalized due to the presence of silane groups on only one of their two hemispheres. This allows us to selectively coat the silane-bearing hemisphere of the dumbbells with a silica layer by means of a Stoeber process. The silica nanobowls are eventually obtained after either calcination or dissolution of the polymeric template. Depending on the route followed to remove the polymer, nanobowls made of pure silica (from calcination) or hybrid Janus nanobowls with a silica outer shell and a covalently bound hydrophobic polymer layer inside the cavity (from dissolution) could be prepared. The difference between the two types of nanobowls has been proved by electrostatically binding oppositely charged silica nanoparticles, which adhere selectively only on the outer silica part of the nanobowls prepared by polymer dissolution, while they attach both inside and outside of nanobowls prepared by calcination. We also show that selective functionalization of the outer surface of the Janus nanobowls from dissolution is possible. This work is one of the first examples of concave objects bearing different functionalities in the inner and outer parts of their surface.
各向异性纳米颗粒的制备在文献中备受关注，其中大部分工作都致力于制备凸形颗粒。相反，在本工作中，我们提出了一种可靠的方法来合成具有一个明确开口、尺寸范围广泛的二氧化硅纳米碗。这些纳米碗是通过去除聚合物，由不对称功能化的二氧化硅-聚合物双面神纳米哑铃作为模板制备而成。具有不同尺寸以及表面化学性质的聚苯乙烯种子被用作两步种子乳液聚合的起始材料，该聚合反应生成聚合物纳米哑铃。由于在其两个半球中只有一个存在硅烷基团，这些哑铃也被不对称功能化。这使我们能够通过斯托伯法选择性地用二氧化硅层包覆哑铃带有硅烷的半球。最终，通过煅烧或溶解聚合物模板获得二氧化硅纳米碗。根据去除聚合物所采用的途径，可以制备由纯二氧化硅制成的纳米碗（通过煅烧）或具有二氧化硅外壳且在腔内有共价键合的疏水聚合物层的混合双面神纳米碗（通过溶解）。通过静电结合带相反电荷的二氧化硅纳米颗粒证明了这两种纳米碗之间的差异，这些纳米颗粒仅选择性地附着在通过聚合物溶解制备的纳米碗的外部二氧化硅部分，而它们在通过煅烧制备的纳米碗的内部和外部均有附着。我们还表明，对通过溶解得到的双面神纳米碗的外表面进行选择性功能化是可行的。这项工作是首批在表面内部和外部分别具有不同功能的凹形物体的实例之一。
