Formation pathways of mesoporous silica nanoparticles with dodecagonal tiling

Abstract

Considerable progress in the fabrication of quasicrystals demonstrates that they can be realized in a broad range of materials. However, the development of chemistries enabling direct experimental observation of early quasicrystal growth pathways remains challenging. Here, we report the synthesis of four surfactant-directed mesoporous silica nanoparticle structures, including dodecagonal quasicrystalline nanoparticles, as a function of micelle pore expander concentration or stirring rate. We demonstrate that the early formation stages of dodecagonal quasicrystalline mesoporous silica nanoparticles can be preserved, where precise control of mesoporous silica nanoparticle size down to <30 nm facilitates comparison between mesoporous silica nanoparticles and simulated single-particle growth trajectories beginning with a single tiling unit. Our results reveal details of the building block size distributions during early growth and how they promote quasicrystal formation. This work identifies simple synthetic parameters, such as stirring rate, that may be exploited to design other quasicrystal-forming self-assembly chemistries and processes.

Two‐Dimensional Superstructures of Silica Cages

“…We recently demonstrated that increased size dispersion in surfactant micelle systems with added pore expander (i.e., oil phase) favors the formation of cage‐like mesoporous silica with nonuniform cage structures rationalizing the appearance of the clathrate IV structure at twice the ammonium hydroxide concentration (vide supra). [ 9 ] In order to increase the micelle size dispersion and further bias the system toward such structures, we mixed two surfactants of different chain lengths (C 16 TAB and C 8 TAB, see Experimental Section). In conjunction with a 1.5‐fold increase of the amount of ammonium hydroxide relative to single‐layer conditions to promote multilayer growth, this indeed resulted in superstructures showing exclusively the clathrate IV structure (Figure 3d−f).…”

“…Since the early reports on directed silica self‐assembly, [ 1 ] these materials and their derivatives in the bulk, [ 2,3 ] as films, [ 4 ] and as nanoparticles [ 5,6 ] have been the subject of extensive research efforts. Benign synthesis conditions, often in aqueous solutions at room temperature, concomitant low toxicity and favorable biocompatibility, [ 7 ] continuous structure discovery, [ 8–10 ] as well as their application potential across different areas, e.g. in catalysis, [ 11 ] energy, [ 12 ] and nanomedicine, [ 6,13 ] maintain high academic and industrial interest levels.…”

“…[ 16 ] In the presence of cationic surfactants such as cetyltrimethylammonium bromide (CTAB), negatively charged clusters self‐assemble into micelle‐templated mesoporous silica, [ 1 ] with sizes controllable down to single pore nanoparticles. [ 17 ] The addition of a pore expander increases micelle size, size dispersity, and deformability, [ 9,18 ] enabling cage‐like mesoporous structures. Numerous studies have identified bulk mesoporous materials formed from such cages as basic building blocks, [ 3,8,19 ] including 5 12 , 5 12 6 2 , or 5 12 6 3 cages, where 5 x 6 y refers to a cage made of x pentagonal and y hexagonal faces.…”

Spatially localized quasicrystalline structures

“…(vi)Other authors speak of spatially localized grains. For example, in [56] such grains are fabricated by manipulating nanoparticles, e.g. by stirring.…”

Aperiodic metal–organic frameworks

“…By taking advantage of accessible quasicrystalline phases in somatter systems (surfactant micelles in particular), it is possible to template the formation of mesoporous silica with similar order. [44][45][46] These methods offer an accessible approach to porous quasicrystals, on the one hand enabling studies of the interactions of guest molecules with porous quasicrystalline hosts, on the other hand providing, perhaps, an alternative pathway towards quasicrystalline MOFs.…”