Size-controlled gold nano-tetradecapods with tunable optical and electromagnetic properties

The optical properties of canted antiferromagnets are discussed from the perspective of magnetic polaritons and field tunable electromagnetic (EM) properties. Canted antiferromagnets have a weak magnetization. Their EM properties can be affected by externally applied magnetic fields as well as electric fields, if the material is multiferroic. A theoretical approach that is useful for describing the THz frequency EM response and properties of a large variety of canted spin systems is outlined here. The properties of two example systems are discussed: an antiferromagnet in which spin canting is induced through an externally applied magnetic field; and an antiferromagnetic multiferroic wherein the magnetic sublattices are canted through an internal coupling to a spontaneous dielectric polarization.

(SiC-Si3N4)w/SiBCN composite ceramics with tunable electromagnetic properties

The synthesis of noble metal nanostructures with adjustable optical properties is essential due to their potential applications in various fields such as imaging, (bio) sensors, and catalysis. In this study, Au@Ag core-shell nanorods were synthesized with tunable optical properties. The synthesis process includes a two-stage approach: first, gold nanorods were synthesized through seed-mediated growth, and in the second stage, these gold nanorods were used as seeds to synthesize Au@Ag core-shell nanorods through the silver deposition process. Tunable core-shell nanorods were produced by changing the concentration of silver ions, reducing agent, stabilizing agent, seeds, and buffer as well as pH and the reaction time. Transmission electron microscopy images demonstrated the formation of the Au@Ag core-shell nanorod structure. In addition, UV-visible spectroscopy revealed the peak height and its shift towards shorter wavelengths, demonstrating the tunable optical properties of the synthesized nanorods. Overall, in this study, we demonstrated the synthesis of Au@Ag core-shell nanorods with adjustable plasmonic optical properties that could be changed by precisely controlling the thickness of the silver shell on the surface of the gold core.

Thin films with tunable optical properties from yellow to metallic were prepared from a monolayer coating of silver nanoparticles (AgNP) onto a polyelectrolyte multilayer (PEM) thin film. The AgNP were synthesized using various concentrations of stabilizing polyelectrolytes leading to a competitive adsorption concept in which AgNP compete with excess polyelectrolytes to coat the cationic PEM top layer. The AgNP were synthesized by chemical reduction of Ag salts using poly(styrene 4-sulfonic acid-co-maleic acid) (PSS-co-MA) as stabilizing agent to produce nanoparticles coated with both a strong acid (sulfonic) and a weak acid (carboxylic) moiety. Although all the nanoparticle solutions displayed a characteristic bright yellow due to the localized surface plasmon band around 420 nm, the monolayer films of nanoparticles obtained after dipping displayed striking different optical properties. When using a high PSS-co-MA content in the solution, a pale-yellow film was obtained which color shifted to orange and metallic when the capping concentration was decreased from 0.25 to 0.001 mM. The optical properties of the AgNP film could be further changed by galvanic replacement of the Ag with gold ions to produce a gold monolayer. These results are interesting to produce surface with tunable catalytic properties, tunable optical properties, or to be used as primer for the metallization of polymeric surfaces.

Carbon nanosheets are mechanically stable, free‐standing two‐dimensional materials with a thickness of ≈1 nm and well defined physical and chemical properties. They are made by radiation‐induced cross‐linking of aromatic self‐assembled monolayers. Herein, a route is presented to the scalable fabrication of multilayer nanosheets with tunable electrical, optical, and chemical properties on insulating substrates. Stacks of up to five nanosheets with sizes of ≈1 cm2 on oxidized silicon are studied. Their optical characteristics are investigated by visual inspection, optical microscopy, UV–vis reflection spectroscopy, and model calculations. Their chemical composition is studied by X‐ray photoelectron spectroscopy. The multilayer samples are then annealed in an ultrahigh vacuum at various temperatures up to 1100 K. A subsequent investigation by Raman, X‐ray photoelectron, and UV–vis reflection spectroscopy, as well as by electrical four‐point probe measurements, demonstrates that the layered nanosheets transform into nanocrystalline graphene. This structural and chemical transformation is accompanied by changes in the optical properties and electrical conductivity and opens up a new path for the fabrication of ultrathin functional conductive coatings.

Optical properties, which determine the application of optical devices in different fields, are the most significant properties of optical thin films. In recent years, Metal-organic framework (MOF)-based optical thin films have attracted increasing attention because of their novel optical properties and important potential applications in optical and photoelectric devices, especially optical thin films with tunable optical properties. This study reports the first example of tuning the optical properties of a MOF-based optical thin film via post-modification. The MOF-based optical thin film was composed of NH2-MIL-53(Al) nanorods (NRs) (MIL: Materials from Institute Lavoisier), and was constructed via a spin-coating method. Three aldehydes with different lengths of carbon chains were chosen to modify the MOF optical thin film to tune their optical properties. After post-modification, the structural color of the NH2-MIL-53(Al) thin film showed an obvious change from purple to bluish violet and cyan. The reflection spectrum and the reflectivity also altered in different degrees. The effective refractive index (neff) of MOFs thin film can also be tuned from 1.292 to 1.424 at a wavelength of 750 nm. The success of tuning of the optical properties of MOFs thin films through post-modification will make MOFs optical thin films meet different needs of optical properties in various optical and optoelectronic devices.

Stimuli-responsive diradicaloid systems often display fascinating and tunable electrochemical, optical, and magnetic properties. Herein, we present the design and synthesis of a series of nitrogen-containing Thiele’s hydrocarbon derivatives (2Ph, 2Py, and 2Pz), based on phenyl, pyridinyl, and pyrazinyl spacers, with tunable electrochemical, electronic, and optical properties. By systematically increasing the number of nitrogen atoms in the molecular backbone, we observed consistent trends in both their absorption and their redox properties. A detailed investigation on the different oxidation states of 2Ph, which displays potential inversion, was also performed, including the intermediate radical cationic state (2PhRC). This intermediate represents an intriguing example of a mixed-valent species whose thermodynamic stability, as calculated by the comproportionation constant (Kc), is diminishingly small, whereas the electronic coupling is strong, making it a borderline class II–III mixed-valence compound. External modulation through coordination with Brønsted and Lewis acids reversibly altered the optical responses of 2Py and 2Pz. This work highlights both structural and stimuli-responsive strategies for tuning organic diradicaloid systems, thereby opening new avenues for their applications in functional materials and coordination chemistry.

Ionogels, with wide applications in tissue engineering, soft robotics, and flexible iontronic devices, require tunable optical, mechanical, and electrical properties for advanced functionality applications. Here, a facile strategy is reported to tune a set of properties of ionogels via tuning the redox states of the added polyoxometalate (POM) clusters. Upon external electrical stimuli, the POM clusters in the ionogels can be reversibly tuned from a transparent, oxidized state to a blue, reduced state. The redox states of the POM anions influence the POM‐polymer interactions, which promotes the in situ modulation of the ionogel properties reversibly over a large window: optical transparency from 91% to 7%, dissipated energy from 0.9 to 3.1 MJ m−3, elastic modulus from 1.5 to 2 MPa, conductivity from 1.6 × 10−4 to 2.2 × 10−4 S cm−1. Meanwhile, the sensory properties of the ionogels can be modulated simultaneously. For strain sensing and pressure sensing, the GF can be tuned from 2.3 to 7.2, and the sensitivity can be tuned from 0.8 to 1.2 kPa−1. Such an ionogel with tunable optical, mechanical, and electrical properties may find a variety of applications meeting specific demands. The POM functionalization strategy may also bring new insights into the design of the stimuli‐responsive ionogels.

In this work, we propose a multiscale hierarchical assembly process to realize the nacre-like layered structural arrangement of functional nanoparticles in a polymer matrix aiming to simultaneously achieve tensile strength enhancement and tunable optical properties in the hybrid materials. Through the designed fabrication route, functional nanoparticles (NPs) were firstly attached onto the surface of brick-like silicate-1 zeolite microcrystals as functional building blocks. Then, NP–zeolite functional microbricks were feasibly assembled with polyvinylalcohol (PVA) to form layered, functional hybrid films. Finally, a 50–100% tensile stress enhancement in the hybrid film is observed when compared to that of pure PVA film. Beside the tensile strength enhancement, the optical properties of the hybrid film can also be tuned by the incorporation of different functional nanoparticles. Our fabrication approach is an example of an alternative strategy to prepare strong hybrid materials with flexible tailoring of functionalities.

Depositing CNTs on the interface and surface of C/PyC/SiCs for tunable mechanical and electromagnetic properties

A general and straightforward synthesis of a series of solution‐processable carbon nitride polymers is described with excellent and tunable optical and electronic properties. The high dispersibility of carbon nitride polymers functionalized with polycyclic aromatic hydrocarbons (PAH‐CNs) in common solvents permits their facile processing into thin films utilizing routine methods such as spin‐coating and drop‐casting. Moreover, altering the PAH group within the CN scaffold enables great tunability of their optical and electronic properties as well as a range of functionalities. This is illustrated by a variety of photoelectrochemical properties, electropolymerization ability, and photoswitching properties for the different PAH‐CNs. The easy processing and tunable properties allow the construction of advanced electronic structures, such as a heterojunction, which significantly improves the photoelectrochemical performance. The versatility of this solution‐processable platform holds promise for the applicability of CNs in new photoelectronic devices.

Thin film transistors fabricated using ZnSe thin films synthesized using chemical bath deposition.

Doping induced effect on optical and band structure properties of Sr2Si5N8 based phosphors: DFT approach

Photonic band gap tunability is crucial in designing optoelectronic devices. Nanostructure semiconductors with tunable band gaps which depend on the dimensionality, have become the potential candidate for tunable nano optoelectronic devices. However, it has a lot of challenges in their fabrication such as the limited number of homogenous particles and high-cost production. As an alternative, sub-micrometer particles with the order of hundred nanometers are more easily fabricated and exhibit tunable optoelectronic properties. In this study, sub-micrometer WS2 was fabricated using low-cost electrochemical methods. Two clusters of particles with the average size of 100 nm and 600 nm are observed. The number of sub-micrometer particles increases with the increasing of fabrication time. The photoluminescence spectra show wide peak centered around 800 nm suggesting the possible application in visible light emitting devices. The peak position varies with the time variation showing that the optical properties might be tuned during fabrication. This study points out that simple solution processed fabrication method can produce sub micrometer particles with tunable optical properties.

Ionic solution-processable Ag nanostructures with tunable optical and electrical properties and strong adhesion to general substrates