The artificial stacking of atomically thin crystals suffers from intrinsic limitations in terms of control and reproducibility of the relative orientation of exfoliated flakes. This drawback is ...particularly severe when the properties of the system critically depends on the twist angle, as in the case of the dodecagonal quasicrystal formed by two graphene layers rotated by 30°. Here we show that large-area 30°-rotated bilayer graphene can be grown deterministically by chemical vapor deposition on Cu, eliminating the need of artificial assembly. The quasicrystals are easily transferred to arbitrary substrates and integrated in high-quality hexagonal boron nitride-encapsulated heterostructures, which we process into dual-gated devices exhibiting carrier mobility up to 105 cm2/(V s). From low-temperature magnetotransport, we find that the graphene quasicrystals effectively behave as uncoupled graphene layers, showing 8-fold degenerate quantum Hall states. This result indicates that the Dirac cones replica detected by previous photoemission experiments do not contribute to the electrical transport.
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IJS, KILJ, NUK, PNG, UL, UM
Personalized Healthcare
In article 2202173 by Jun‐ho Jeong and co‐workers, the dodecagonal quasicrystal patterned (DQP) lens for 2D focusing of the ultrasound is developed, and integrated into the ...mobile ultrasound 2D focusing (MU2F) system for improved high intensity focused ultrasound (HIFU) system. The developed system proved its advanced applicability by being utilized in personalized healthcare based on microneedle‐based drug delivery system.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Anisotropic patchy particles with molecular precision are exquisite building blocks for constructing diverse meso-structures of high complexity. In this research, a library of molecular patchy ...clusters consisting of a collection of functional polyhedral oligomeric silsesquioxane cages with exact regio-configuration and composition were prepared through a robust and modular approach. By meticulously tuning the composition, molecular symmetry, and other parameters, these patchy clusters could assemble into diverse nanostructures, including unconventional complex spherical phases (i.e., Frank–Kasper σ phase and dodecagonal quasicrystalline phase). As the size of the hydrophilic patch expands, a transition sequence from disorder to hexagonally packed cylinders and then to double gyroids was recorded, corresponding to a progressive decrease of interfacial curvature. On the other hand, regioisomers with the same composition but different regio-configuration adopt similar molecular packing but varied phase stability, as a result of the local self-sorting process to alleviate excess unfavorable interfacial contact. These precisely defined molecular patchy clusters provide a model system for a general understanding of the hierarchical structure formation and evolution based on anisotropic spherical building blocks at the nanoscale.
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IJS, KILJ, NUK, PNG, UL, UM
Ultrasound technology is widely utilized in applications, including tumor treatments, drug delivery, and skin care. However, improvements are required to prevent unwanted damage to non‐targeted ...tissues. The ultrasound focusing technology, represented by the highly intensive focused ultrasound (HIFU) technology, is actively researched to handle this problem. However, current technology is primarily limited in the point focusing of the ultrasound. Some applications, such as drug delivery and skin care, require 2D‐focusing of the ultrasound for effective utilization. Based on this necessity, this research proposes the rationally designed dodecagonal quasicrystal patterned (DQP) planar lens, which enables ultrasound focusing in 2D. The custom‐built ultrasound scanning setup confirms the 2D focusing behavior of the DQP lens. Furthermore, the developed DQP lens is integrated into the mobile ultrasound 2D focusing (MU2F) system and solved the bulkiness limitation of the HIFU system. The proposed MU2F system is applied in microneedle‐mediated drug delivery. The dramatic enhancement in the dissolution efficiency of the drug‐containing microneedle (≈2.5×) compared with the case without the MU2F system is confirmed. Through the proposed MU2F system, ultrasound‐based medical devices may widen their approachability from the clinic to the home.
This research proposes the dodecagonal quasicrystal patterned (DQP) planar lens for 2D‐focusing of the ultrasound. The developed DQP lens is integrated into the mobile ultrasound 2D focusing (MU2F) system to solve the bulkiness issue of the conventional system, and utilized to microneedle‐mediated drug delivery. The system increases the dissolution efficiency of microneedles by about 2.5 times.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
One of the essential components of molecular electronic circuits are switching elements that are stable in two different states and can ideally be switched on and off many times. Here, distinct ...buckminsterfullerenes within a self‐assembled monolayer, forming a two‐dimensional dodecagonal quasicrystal on a Pt‐terminated Pt3Ti(111) surface, are identified to form well separated molecular rotational switching elements. Employing scanning tunneling microscopy, the molecular‐orbital appearance of the fullerenes in the quasicrystalline monolayer is resolved. Thus, fullerenes adsorbed on the 36 vertex configuration are identified to exhibit a distinctly increased mobility. In addition, this finding is verified by differential conductance measurements. The rotation of these mobile fullerenes can be triggered frequently by applied voltage pulses, while keeping the neighboring molecules immobile. An extensive analysis reveals that crystallographic and energetic constraints at the molecule/metal interface induce an inequality of the local potentials for the 36 and 32.4.3.4 vertex sites and this accounts for the switching ability of fullerenes on the 36 vertex sites. Consequently, a local area of the 8/3 approximant in the two‐dimensional fullerene quasicrystal consists of single rotational switching fullerenes embedded in a matrix of inert molecules. Furthermore, it is deduced that optimization of the intermolecular interactions between neighboring fullerenes hinders the realization of translational periodicity in the fullerene monolayer on the Pt‐terminated Pt3Ti(111) surface.
Local potential differences between the 36 and 32.4.3.4 vertex configurations are identified within a two‐dimensional dodecagonal fullerene monolayer. In a local area of the 8/3 approximant, rotational switching fullerenes on 36 vertex sites are revealed by scanning tunneling microscopy.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In this paper, two kinds of contact problems in 2-D dodecagonal quasicrystals were discussed using the complex variable function method: one is the finite frictional contact problem, the other is the ...adhesive contact problem. The analytic expressions of contact stresses in the phonon and phason fields were obtained for a flat rigid punch, which showed that: (1) for the finite frictional contact problem, the contact stress exhibited power-type singularities at the edge of the contact zone; (2) for the adhesive contact problem, the contact stress exhibited oscillatory singularities at the edge of the contact zone. The distribution regulation of contact stress under punch was illustrated; and the low friction property of quasicrystals was verified graphically.
Is quasicrystal structure analysis a never-ending story? Why is still not a single quasicrystal structure known with the same precision and reliability as structures of regular periodic crystals? ...What is the state-of-the-art of structure analysis of axial quasicrystals? The present comprehensive review summarizes the results of almost twenty years of structure analysis of axial quasicrystals and tries to answer these questions as far as possible. More than 2000 references have been screened for the most reliable structural models of pentagonal, octagonal, decagonal and dodecagonal quasicrystals. These models, mainly based on diffraction data and/or on bulk and surface microscopic images are critically discussed together with the limits and potentialities of the respective methods employed.
A two-dimensional dodecagonal quasicrystal was previously reported by Dotera et al (2014 Nature 506 208) in a system of particles interacting with a hard core of diameter σ and a repulsive square ...shoulder of diameter δ=1.40σ. In the current work, we examine the formation of this quasicrystal using bond orientational order parameters, correlation functions and tiling distributions. We find that this dodecagonal quasicrystal forms from a fluid phase. We further study the effect of the width of the repulsive shoulder by simulating the system over a range of values of δ. For the range of densities and temperatures considered, we observe the formation of the dodecagonal quasicrystal between δ=1.30σ and 1.44σ. We also study the effect of shape of the interaction potential by simulating the system using three other interaction potentials with two length scales, namely hard-core plus a linear ramp, modified exponential, or Buckingham (exp-6) potential. We observe the presence of the quasicrystal in all three systems. However, depending on the shape of the potential, the formation of the quasicrystal takes place at lower temperatures (or higher interaction strengths). Using free-energy calculations, we demonstrate that the quasicrystal is thermodynamically stable in the square-shoulder and linear-ramp system.
Quasicrystals are one kind of space-filling structures. The traditional crystalline approximant method utilizes periodic structures to approximate quasicrystals. The errors of this approach come from ...two parts: the numerical discretization, and the approximate error of Simultaneous Diophantine Approximation which also determines the size of the domain necessary for accurate solution. As the approximate error decreases, the computational complexity grows rapidly, and moreover, the approximate error always exits unless the computational region is the full space. In this work we focus on the development of numerical method to compute quasicrystals with high accuracy. With the help of higher-dimensional reciprocal space, a new projection method is developed to compute quasicrystals. The approach enables us to calculate quasicrystals rather than crystalline approximants. Compared with the crystalline approximant method, the projection method overcomes the restrictions of the Simultaneous Diophantine Approximation, and can also use periodic boundary conditions conveniently. Meanwhile, the proposed method efficiently reduces the computational complexity through implementing in a unit cell and using pseudospectral method. For illustrative purpose we work with the Lifshitz–Petrich model, though our present algorithm will apply to more general systems including quasicrystals. We find that the projection method can maintain the rotational symmetry accurately. More significantly, the algorithm can calculate the free energy density to high precision.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Multimodal cage-type mesoporous silicas (MCMSs) with Frank-Kasper type square-triangle tiling show a unique defect structure, so-called three-fold symmetric hexagons, or shields, which are caused by ...phason fluctuations in dodecagonal quasicrystals. We observed and characterized three types of configurations inside shields in both quasiperiodic and periodic 32.4.3.4 tiling of MCMSs by transmission electron microscopy (TEM). The high-resolution TEM images of the shields were well explained by polyhedral models, which are the constituents of the Frank-Kasper type tetrahedrally close-packed structures of MCMSs. Shield defects invariably formed because of mismatch in periodic and/or aperiodic square-triangle tiling, and they were also catalyzed by other defects. Multiple shields overlapped with sharing of 30° rhombus units and showed characteristic motifs in the tiling, such as defect-mediated 12-fold wheel and stripe bundle arrangements. Hence, MCMSs with square-triangle tiling would be governed by a random-tiling-like structure stabilized by entropy rather than energy, which results in defect-free tiling.
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