Template-Assisted Synthesis of Janus Silica Nanobowls

Abstract

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.

Clustering of asymmetric dumbbell-shaped silica/polystyrene nanoparticles by solvent-induced self-assembly

“…removing the pure PS component and leading to silica nanobowls with a regular thickness (See Supplementary material, Fig. S4) as previously reported [22]. According to the same strategy, several batches of asymmetric dumbbells were prepared with different geometrical features (Table 1), in particular with a patchto-particle diameter ratio varying from 0.32 to 1.00.…”

“…the patch, would have been much larger than the silica lobe and not easily down sizable. So we prepared them according to a protocol previously reported by Guignard and Lattuada [22] (Fig. 1) and took advantage of this synthesis pathway to vary the size of the PS lobe, i.e.…”

Core–Shell Interface-Oriented Synthesis of Bowl-Structured Hollow Silica Nanospheres Using Self-Assembled ABC Triblock Copolymeric Micelles

“…From the available literature, similar phenomenon was observed for different nanoparticles containing large through holes on shell. [54][55][56] The mesoporous shell can also be proved by the nitrogen adsorption-desorption isotherm (see Supporting Information Figure S3a), which exhibits typical type-IV hysteresis loop. Additionally, the Barrett-Joyner-Halenda (BJH) pore size distribution plot (see Supporting Information Figure S3b) indicates the presence of various size mesopores.…”

Thermally-Induced Actuations of Stimuli-Responsive, Bicompartmental Nanofibers for Decoupled Drug Release

“…A number of original platform technologies for synthesis of multi-compartmentalized structures at micro- or nanoscale have been devised based on composition and surface anisotropy: electrohydrodynamic (EHD) co-jetting, microfluidics, flow-focusing lithography, template-assisted polymerization, differential solvent evaporation, spinning disks, selective crystallization, and deposition, partial masking, Pickering emulsion, and self-assembly (Paunov, 2003; Bong et al, 2009; Pardhy and Budhlall, 2010; Du and O'reilly, 2011; Jung et al, 2014; Guignard and Lattuada, 2015; Nisisako, 2016). In particular, EHD co-jetting enables different polymer solutions in miscible aqueous or organic solvent with side-by-side needle geometry to have equilibrated laminar flow and ejection from the vertex of the multi-phasic Taylor cone in a thin-jet stream, induced by charge-charge repulsion under high electrical potential (Barrero et al, 1998; Hogan Jr et al, 2007).…”