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.
Highlights
Considerable progress in the fabrication of quasicrystals demonstrates that they can be realized in a broad range of materials
Our results suggest that the incorporation of building blocks with asymmetric size distributions at early times in the growth process promotes quasicrystal formation and that simple synthesis parameters like stirring rate can be used for their control
We have discovered a series of four different structures in mesoporous silica nanoparticles (MSNs), including dodecagonal tiling, as a function of either pore expander concentration or stirring rate
Summary
As [TMB] is further increased, subsequently single phase Pm3n cubic MSNs (Fig. 1l) and MSNs with dodecagonal symmetry are formed, the latter incorporating even larger micelles (red) (Fig. 1m) These observations are supported by pore size analysis of nitrogen sorption measurements on TEOS/AEAPTMS particles after CTAB removal that show marked pore size increase and broadening of the pore size distribution with increasing [TMB] (Supplementary Fig. 2). As [TMB] is increased to 47 and 116 mM (cubic and quasicrystalline MSNs), the increasingly broadened pore size distributions can no longer be described by unimodal log-normal fits, suggesting that additional micelle populations may be involved in the formation processes of these more complex structures. Analysis of simulated single-particle growth trajectories (Fig. 5a) shows the relationship between quasicrystallinity (Rg⊥ vs Rg//) and the size of the particle or the number of square tiles present (plotted along the z-axis) when the first triangle is added. Similarities between tilings from TEM images of particles synthesized at intermediate [TMB] and tilings of simulated particles at various stages of growth support the assumption that the formation of MSNs with dodecagonal tilings can be described using our model (Fig. 6)
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