Megahertz-wave-transmitting conducting polymer electrode for device-to-device integration

The ideal combination of high optical transparency and high electrical conductivity, especially at very low frequencies of less than the gigahertz (GHz) order, such as the radiofrequencies at which electronic devices operate (tens of kHz to hundreds of GHz), is fundamental incompatibility, which creates a barrier to the realization of enhanced user interfaces and ‘device-to-device integration.’ Herein, we present a design strategy for preparing a megahertz (MHz)-transparent conductor, based on a plasma frequency controlled by the electrical conductivity, with the ultimate goal of device-to-device integration through electromagnetic wave transmittance. This approach is verified experimentally using a conducting polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), the microstructure of which is manipulated by employing a solution process. The use of a transparent conducting polymer as an electrode enables the fabrication of a fully functional touch-controlled display device and magnetic resonance imaging (MRI)-compatible biomedical monitoring device, which would open up a new paradigm for transparent conductors. © 2019, The Author(s

Chirality control of inorganic materials and metals by peptides or amino acids

Chirality exists everywhere in nature and may be one of the most important features in biological systems. The chirality of amino acid molecules is transferred to the peptide sequences, determining the secondary and further three-dimensional structures. As a result, even the macroscopic chirality observed in many living features can be controlled by the peptide sequence. Interestingly, recent studies have shown that achiral inorganic materials and metals, according to the crystallographic point group, can develop chiral morphologies that are precisely controlled by the amino acids and peptides. As a result, strong chiral optical responses can be generated even at visible wavelengths. In this review, we have highlighted recent pioneering examples to show the enantioselective interactions between inorganic materials/metals and amino acids/peptides and discussed the underlying mechanisms.Y

Wave-Tunable Lattice Equivalents toward Micro- and Nanomanipulation

The assembly of micro- and nanomaterials is a key issue in the development of potential bottom-up construction of building blocks, but creating periodic arrays of such materials in an efficient and scalable manner still remains challenging. Here, we show that a cymatic assembly approach in which micro- and nanomaterials in a liquid medium that resonate at low-frequency standing waves can be used for the assembly in a spatially periodic and temporally stationary fashion that emerges from the wave displacement antinodes of the standing wave. We also show that employing a two-dimensional liquid, rather than a droplet, with a coffee-ring effect yields a result that exhibits distinct lattice equivalents comprising the materials. The crystallographic parameters, such as the lattice parameters, can be adjusted, where the parameters along the <i>x</i>- and <i>y</i>-axes are controlled by the applied wave frequencies, and the one along <i>z</i>-axis is controlled by a transparent layer as a spacer to create three-dimensional crystal equivalents. This work represents an advancement in assembling micro- and nanomaterials into macroscale architectures on the centimeter-length scale, thus establishing that a standing wave can direct micro- and nanomaterial assembly to mimic plane and space lattices

Random Lasing with a High Degree of Circular Dichroism by Chiral Plasmonic Gold Nanoparticles

Random lasers have distinct advantages to be the next-generation light sources owing to their simple fabrication process, high flexibility in shape and size, and unique optical characteristics, such as low spatial coherence, high intensity, and multi-directionality. In this paper, we discuss how to realize random lasing with a high degree of circular dichroism with the aid of chiral plasmonic gold nanoparticles. The extinction dissymmetry factor of the chemically synthesized chiral plasmonic gold nanoparticles is measured to be -0.11 at its peak wavelength of 575 nm. The lasing properties and luminescence dissymmetry factor of the emission of the random laser are measured and characterized. An optimal inclusion of the chiral plasmonic gold nanoparticles to an ethylene glycol solution of rhodamine 6G laser dye molecules mixed with dielectric titanium dioxide nanoparticles eventually results in the laser emission having a considerably high level of asymmetry between the right- and left-handed circularly polarized light, yielding a luminescence dissymmetry factor of 0.20-0.23. This study paves the way for the development of a random laser of a high degree of circular dichroism in a highly flexible compact form through a simple, mass-productive fabrication process, inviting numerous potential applications in nano-photonics.N

Chiral Surface and Geometry of Metal Nanocrystals

Chirality is a basic property of nature and has great importance in photonics, biochemistry, medicine, and catalysis. This importance has led to the emergence of the chiral inorganic nanostructure field in the last two decades, providing opportunities to control the chirality of light and biochemical reactions. While the facile production of 3D nanostructures has remained a major challenge, recent advances in nanocrystal synthesis have provided a new pathway for efficient control of chirality at the nanoscale by transferring molecular chirality to the geometry of nanocrystals. Interestingly, this discovery stems from a purely crystallographic outcome: chirality can be generated on high-Miller-index surfaces, even for highly symmetric metal crystals. This is the starting point herein, with an overview of the scientific history and a summary of the crystallographic definition. With the advance of nanomaterial synthesis technology, high-Miller-index planes can be selectively exposed on metallic nanoparticles. The enantioselective interaction of chiral molecules and high-Miller-index facets can break the mirror symmetry of the metal nanocrystals. Herein, the fundamental principle of chirality evolution is emphasized and it is shown how chiral surfaces can be directly correlated with chiral morphologies, thus serving as a guide for researchers in chiral catalysts, chiral plasmonics, chiral metamaterials, and photonic devices. © 2019 WILEY-VCH Verlag GmbH &amp; Co. KGaA, WeinheimN

gamma-Glutamylcysteine- and Cysteinylglycine-Directed Growth of Chiral Gold Nanoparticles and their Crystallographic Analysis

Chiral optical metamaterials with delicate structures are in high demand in various fields because of their strong light–matter interactions. Recently, a scalable strategy for the synthesis of chiral plasmonic nanoparticles (NPs) using amino acids and peptides has been reported. Reported herein, 3D chiral gold NPs were synthesized using dipeptide γ-Glu-Cys and Cys-Gly and analyzed crystallographically. The γ-Glu-Cys-directed NPs present a cube-like outline with a protruding chiral wing. In comparison, the NPs synthesized with Cys-Gly exhibited a rhombic dodecahedron-like outline with curved edges and elliptical cavities on each face. Morphology analysis of intermediates indicated that γ-Glu-Cys generated an intermediate concave hexoctahedron morphology, while Cys-Gly formed a concave rhombic dodecahedron. NPs synthesized with Cys-Gly are named 432 helicoid V because of their unique morphology and growth pathway.N

Magnetic Control of the Plasmonic Chirality in Gold Helicoids

Chiral plasmonic nanostructures have facilitated a promising method for manipulating the polarization state of light. While a precise structural modification at the nanometer-scale-level could offer chiroptic responses at various wavelength ranges, a system that allows fast response control of a given structure has been required. In this study, we constructed uniformly arranged chiral gold helicoids with cobalt thin-film deposition that exhibited a strong chiroptic response with magnetic controllability. Tunable circular dichroism (CD) values from 0.9° to 1.5° at 550 nm wavelength were achieved by reversing the magnetic field direction. In addition, a magnetic circular dichroism (MCD) study revealed that the gap structure and size-related surface plasmon resonance induced MCD peaks. We demonstrated the transmitted color modulation, where the color dynamically changed from green-to-red, by controlling the field strength and polarizer axis. We believe current work broadens our understanding of magnetoplasmonic nanostructure and expands its potential applicability in optoelectronics or optical-communications

Uniform Chiral Gap Synthesis for High Dissymmetry Factor in Single Plasmonic Gold Nanoparticle

Synthesis of chiral plasmonic materials has been highlighted for the last decades with their optical properties and versatile potential applications. Recently reported aqueous-based amino acid- and peptide-directed synthesis of chiral plasmonic gold nanoparticles with 432 point-group symmetry shows exceptionally high chiroptic response within 100 nm scales. Despite its already excellent chiroptic response, a single-nanoparticle dark field scattering study revealed that full chiroptic potential of chiral gold nanoparticle is limited with its overall synthetic uniformity. Based on this knowledge, we present a multi-chirality-evolution step synthesis method for the enhancement of chiroptic response through an increase in particle uniformity. Detailed time variant study and interrelationship study of reaction parameters allowed the systematic construction of design principles for chiral nanoparticles with exceptional chiroptic response. With the application of precisely controlled growth kinetic to two distinct growth regimes, modified chiral gold nanoparticles showed significantly improved uniformity, achieving an improved dissymmetry factor of g = 0.31. We expect that our strategy will aid in precise morphology and property control for chiral nanomaterials, which can be used in various plasmonic metamaterial applications.N