Colloidal annular sectors are a broad class of shapes that offer the interesting possibility of dimerization when osmotically compressed to high densities while undergoing Brownian motion in two dimensions (2D). Here, we lithographically create and form a stable aqueous dispersion of many microscale prismatic 270° annular sectors, and we explore their near-equilibrium behavior in a tilted 2D gravitational column. Near the top of the column where the 2D gravitational osmotic pressure Π(2D) is low, we observe a gas-like phase composed almost entirely of monomers. However, below the surface and deeper into the column where Π(2D) is higher, we observe a reaction zone where monomers and dimers coexist, followed by an arrested region containing a very high percentage of interpenetrating, lock-and-key dimers that are a racemic mixture of positive and negative chiralities. We determine particle area fractions of monomers and dimers as a function of depth and use these to obtain the system's 2D osmotic equation of state. In the reaction zone, where dimers transiently form and break up, we also use these to calculate the equilibrium constant K associated with the monomer-dimer reaction, which increases exponentially with Π(2D). This dependence can be attributed the reduction in number of accessible microstates for dimers as they become more tightly compressed.

Penrose's pentagonal P2 quasi-crystal is a beautiful, hierarchically organized multiscale structure in which kite- and dart-shaped tiles are arranged into local motifs, such as pentagonal stars, which are in turn arranged into various close-packed superstructural patterns that become increasingly complex at larger length scales. Although certain types of quasi-periodic structure have been observed in hard and soft matter, such structures are difficult to engineer, especially over large areas, because generating the necessary, highly specific interactions between constituent building blocks is challenging. Previously reported soft-matter quasi-crystals of dendrimers, triblock copolymers, nanoparticles and polymeric micelles have been limited to 12- or 18-fold symmetries. Because routes for self-assembling complex colloidal building blocks into low-defect dynamic superstructures remain limited, alternative methods, such as using optical and directed assembly, are being explored. Holographic laser tweezers and optical standing waves have been used to hold microspheres in local quasi-crystalline arrangements, and magnetic microspheres of two different sizes have been assembled into local five-fold-symmetric quasi-crystalline arrangements in two dimensions. But a Penrose quasi-crystal of mobile colloidal tiles has hitherto not been fabricated over large areas. Here we report such a quasi-crystal in two dimensions, created using a highly parallelizable method of lithographic printing and subsequent release of pre-assembled kite- and dart-shaped tiles into a solution-dispersion containing a depletion agent. After release, the positions and orientations of the tiles within the quasi-crystal can fluctuate, and these tiles undergo random, Brownian motion in the monolayer owing to frequent collisions between neighbouring tiles, even after the system reaches equilibrium. Using optical microscopy, we study both the equilibrium fluctuations of the system at high tile densities and also the 'melting' of the pattern as the tile density is lowered. At high tile densities we find signatures of a five-fold pentatic liquid quasi-crystalline phase, analogous to a six-fold hexatic liquid crystal. Our fabrication approach is applicable to tiles of different sizes and shapes, and with different initial positions and orientations, enabling the creation of two-dimensional quasi-crystalline systems (and other systems that possess multiscale complexity at high tile densities) beyond those of current self- or directed-assembly methods. We anticipate that our approach for generating lithographically pre-assembled monolayers could be extended to create three-dimensional Brownian systems of fluctuating particles with custom-designed shapes through holographic lithography or stereolithography.

Due to the expeditious expansion of wearable electronics, all-solid-state flexible supercapacitors are being contemplated as promising energy-storage devices. Through the successful preparation of large quantities of high-quality semiconducting-type thin molybdenum disulfide (MoS 2 ) sheets suspended in water, the authors have developed an environmentally friendly and simple method to fabricate ternary flexible electrodes with MoS 2 , polyaniline (PANI), and carbon nanotubes (CNTs). The resulting MoS 2 /PANI/CNT all-solid-state supercapacitor can be easily integrated in series to power commercial light-emitting diodes without an external bias voltage. In addition, such a supercapacitor exhibits remarkable energy density (0.013 Wh cm −3 ) and power density (1.000 W cm −3 ), thus making it superior to commercially available lithium thinfilm batteries (4 V/500 μA h) and 2.75 V/44 mF activated carbon electrochemical capacitors. These results demonstrate that the exfoliated MoS 2 -based composite is a promising material for the development of high-performance and low-cost energystorage devices.

Vacancy sites, e.g., S-vacancies, are essential for the performance of MoS2 catalysts. As earlier studies have revealed that the size and shape of the S-vacancies may affect the catalytic activity,...

This paper reports a simple and scalable colloidal templating technology for fabricating wafer-scale periodic plasmonic nanodimple arrays with tunable nanostructures. A double-layer, non-close-packed colloidal crystal−polymer nanocomposite created by a spin-coating technique is used as structural template in a simple oxygen plasma etching process to fabricate periodic arrays of nanodimples. The resulting plasmonic arrays can sense a small dielectric refractive index change of ∼0.008, and they exhibit high SPR sensitivity of up to ∼520 nm per refractive index unit. The experimental plasmonic performance of the nanodimple arrays matches with the numerical simulations using a finite-difference time-domain model.