Manganese oxide (MnO2) nanostructures (NSs) were synthesized via a coprecipitation method using MnCl2·4H2O and KMnO4 precursors. The effects of precursor concentration, calcination temperature, and reaction time were systematically optimized using Response Surface Methodology (RSM) based on a Box-Behnken design (BBD). Analysis of variance (ANOVA) identified calcination temperature and reaction time as a key factor governing the electrochemical response. Structural characterization (XRD and FTIR) confirmed the formation of ε-MnO2 (akhtenskite) as the dominant phase, while SEM and EDX verified the morphology and elemental composition. BET analysis revealed a high surface area for the optimized TB2 sample (ε-MnO2, 156.82 m2 g-1). Electrochemical measurements (CV, GCD, and EIS) demonstrated superior performance for the optimized TB2 electrode, synthesized with 2 g KMnO4, and calcined at 200 °C for 3 h. It delivered a specific capacitance of 113.996 F/g at 10 mV s-1 and an areal capacitance of 317.84 mF cm-2 at 0.5 A g-1. A maximum energy density of 2.4 W h kg-1 (11.04 mW h cm-2) was achieved at a power density of 372.40 W kg-1 (1787.5 mW cm-2). After 200 cycles, it retained 78.3% capacitance retention and 112% Coulombic efficiency were maintained, highlighting the potential of ε-MnO2 NSs for advanced energy storage applications.

Lithium-metal anodes offer exceptional theoretical capacity and the lowest electrochemical potential, but their practical use is limited by dendrite growth, unstable SEI formation, and large volume fluctuations. Carbon nanofibers (CNFs), with their low weight, high conductivity, and tunable structures, serve as effective hosts for regulating lithium deposition. Heteroatom doping further enhances lithiophilicity and interfacial stability: nitrogen creates abundant nucleation sites, oxygen and sulfur increase surface polarity and strengthen the SEI, and fluorine facilitates LiF-rich interphases for dendrite-free growth. Multi-element doping can also provide synergistic improvements in Coulombic efficiency and cycling stability. Despite these advances, challenges remain, including electrolyte consumption in high-surface-area structures, nonuniform dopant distribution, and potential degradation of CNF properties at high doping levels. This article summarizes recent progress in heteroatom-doped CNFs for lithium-metal anodes and outlines key limitations and future directions toward scalable, high-performance lithium-metal batteries.

Hierarchically chiral structures exhibit multiscale chirality across multiple length scales, ranging from the atomic to the micrometer scale. Recent studies have investigated their pronounced circular dichroism (CD) signals, chemical stability, and new properties, demonstrating their potential for diverse applications. This review focuses on the characteristics of semiconductor and polysaccharide nanocrystals that exhibit hierarchical architectures with two or more levels, with structural features ranging from 0.1 nm to 10 nm, 1 μm, and up to 10 μm. Particular attention is paid to small nanoparticles such as Cu2S and CdTe in the category of semiconductors, and to cellulose and chitin nanocrystals among organic nanocrystals. Chiral semiconducting nanocrystals exhibit distinctive characteristics, including remarkable self-assembly capabilities into hierarchical structures and corresponding optical activities. Polysaccharide nanocrystals such as cellulose nanocrystals can be self-assembled into a chiral nematic liquid crystal phase, exhibiting strong chiral light reflection. This review provides a brief overview of recent studies of hierarchically chiral nanomaterials and their potential applications in optoelectronic devices, tunable color films, and optical sensors. This will facilitate a deeper understanding of underlying mechanisms and functional properties of hierarchically self-assembled chiral nanomaterials.

Optoelectronic devices using circularly polarized light (CPL) offer enhanced sensitivity and specificity for efficient data processing. There is a growing demand for CPL sensing mediums with strong optical activity, stability and sensitivity, multiple transition bands, and environmental compatibility. Here, defect-engineered chiroferromagnetic quantum dots (CFQDs) are used as a new type of CPL sensing material. By inducing amorphization defects through chiral molecules, CFQDs with high unpaired electron density, atomic structural chirality, amplified chiroptical activity, and multiple exciton transition bands are developed. CFQDs enable nonlinear, long-term plastic behavior with linear optical input, acting as in situ noise filters that reduce noise by over 20%. Additionally, CFQDs provide over nine times higher integration for photon polarization and wavelength distinctions, paving the way for next-generation processors with improved energy efficiency, integration, and reduced retention time.

Chiroptoelectronic devices are crucial for applications in quantum computing, spin optical communications, and magnetic recording. However, the limited efficiency and low stability of conventional circularly polarized light (CPL)-sensing materials have restricted their broader use. Here, we introduce atomic chiral Se nanorod (NRs) films as broadband CPL detectors, leveraging the intrinsic chirality and stability of Se nanocrystals. We also perform incident circular polarization (ICP)-Raman optical activity (ROA) to explore the chiroptical activity of the large-area films. The Se NRs thin films detected CPL across a broad range from ultraviolet (UV) to short-wavelength infrared (SWIR), with a responsivity dissymmetry factor of up to 0.4, maintaining high stability under ambient conditions for longer than 13 months. CPL-sensitive Se NRs with intrinsic chirality have potential applications in chiral photonic synapses, chiral spin devices, and CPL-sensitive photocatalysts. ICP-ROA mapping also advances the analysis of 2D chiral materials.

AbstractThis study presents visible‐light chiral photonic synaptic devices based on 2D chiral hybrid organic‐inorganic perovskites (HOIPs), composed of Si/SiO₂/chiral HOIPs/poly(methyl methacrylate)/pentacene/Au, designed for circularly polarized light (CPL)‐active peripheral nervous system (PNS) applications. In the heterostructure of 2D chiral HOIPs and pentacene, chiral HOIPs effectively distinguish the direction of CPL and the pentacene layer extracts photoinduced charge carriers to achieve synaptic properties, as confirmed by circular dichroism and photoluminescence analyses. The devices exhibit a photocurrent dissymmetry factor of up to 0.3 and a photoresponsivity of 130 mA W−1. Logic operations using a 3 × 4 pixel array of chiral HOIP‐based heterostructures are demonstrated, achieving pattern recognition based on the direction of CPL and pulse interval time. Notably, the efficiency to discriminate CPL direction increases with longer pulse intervals. This improvement enhances the learning capability by amplifying CPL direction discrimination ratios. Leveraging these properties, neural network simulations for neuromorphic applications are conducted, and artificial neural networks are trained for image recognition using the devices as CPL filters, achieving a 92% recognition accuracy. These results signify the beginning of chiral PNS devices communicating with visible CPL based on 2D chiral HOIPs.

Chirality-induced spin selectivity (CISS) allows for the generation of spin currents without the need for ferromagnets or external magnetic fields, enabling innovative spintronic device designs. One example is a chiral spin valve composed of ferromagnetic and chiral materials, in which the resistance depends on both the magnetization direction of the ferromagnet and the chirality of the chiral material. So far, chiral spin valves have predominately employed chiral organic molecules, which have limited device applications. Chiral perovskites, which combine the properties of inorganic perovskites with chiral organic molecules, provide an excellent platform for exploring CISS-based devices. However, previous chiral perovskite-based spin valves exhibited magnetoresistance (MR) only at low temperatures. Here, we report room temperature MR in a chiral spin valve consisting of chiral perovskites/AlOx/perpendicular ferromagnet structures. It is observed that the chiral MR increases with rising temperature, suggesting the crucial role of phonon-induced enhancement of spin–orbit coupling in CISS in our device. Furthermore, we enhanced the chiral MR by introducing chiral molecules with amplified chirality. This highlights the potential of chirality engineering to improve CISS and the associated chiral MR, thereby opening possibilities for chiral spin valves tailored for cutting-edge spintronic applications.

Abstract Circularly polarized light (CPL)-sensitive detector enables various techniques such as quantum computing, spin optical communications, and magnetic recording. However, limited responsive wavelength range and low stability of the common CPL detecting materials have hindered explosive applications of CPL detectors. Here, we introduce atomic chiral Se nanorods films as a broadband CPL detector, taking advantage of the intrinsic atomic chirality and the stability of inorganic Se nanocrystals. An incident circular polarization (ICP)-Raman optical activity (ROA) mapping technique is also performed to examine the chiroptical activity of the large-area CPL detecting films. This ROA mapping technique is firstly presented with our knowledge as a new analytic method for chirality of 2D materials. The monolayered Se NRs detect circularly polarized light in broad wavelengths from UV to SWIR with the responsivity dissymmetry factor (gres) up to 0.4 with high stability at ambient conditions for longer than 1 year. The CPL-sensitive Se NRs will also be employed in various applications, such as chiral photonic synapses, chiral spin devices, and CPL-sensitive photocatalysts. Furthermore, our ICP-ROA mapping technique will open a new door to the development and analysis of 2D chiral materials.

As the demand for environmental purification and energy harvesting continues to grow, research on maximizing the efficiency of catalysts is attracting great attention. The piezo-phototronic effect has emerged as an effective strategy to enhance the photocatalytic activity of semiconductors. While p-type semiconductors exhibit high photoresponsivity across a wide spectral range, their potential as piezo-photocatalysts has been limited due to their low carrier concentration and inferior carrier migration behavior. Therefore, it is hypothesized that overcoming these limitations would allow p-type semiconductors to achieve catalytic performance comparable to, or even surpassing, that of n-type systems. Here, we introduce two effective strategies into p-type trigonal selenium nanowires (Se NWs): electron-proton co-doping and localized surface plasmon resonance effect. These approaches improve the light absorption capacity, charge transport ability, and piezoelectricity, thereby significantly enhancing the piezo-photocatalytic performance. Under the influence of the piezo-phototronic effect, the post-treated Se NWs exhibit markedly enhanced evolution rates of reactive oxygen species compared to pure Se NWs. Consequently, the degradation efficiency of organic contaminants is increased up to 4-fold. This breakthrough opens up a new pathway for the development of p-type piezoelectric materials, which can potentially replace their n-type counterparts in catalytic applications.

High‐index dielectric nanostructures offer strong magnetic and electric resonances in the visible range and low optical losses, stimulating research interest in their use for light manipulation technologies. Lithographic fabrication of dielectric nanostructures, while providing precise control over the pattern dimensions, limits the scalability of this approach for practical applications due to an inefficient fabrication process and limited production quantity. Here, the colloidal synthesis of high‐index chiral dielectric nanostructures with a broom‐like geometry made from trigonal Se is demonstrated. The anisotropic morphology and crystal structure of Se nanobrooms enable both linearly and circularly polarized scattering, as well as spectrum variation along the particle axis, which is, to the authors’ knowledge, the first observation of such behavior from dielectric colloidal nanostructures. To show the versatility of the highly scattering Se NB suspensions, 2D and 3D printing of Se NB inks are demonstrated as a proof of concept. This approach provides a way to manipulate light using aqueous dispersions of high‐index dielectric nanostructures, unlocking their potential to fit in various morphologies and dimensions in 2D and 3D for broad applications.

Chiroptical activity over a broad range is expected to enable numerous applications including bioimaging and nanothermometers. However, understanding the chemical mechanism behind producing multiscale chirality for broad range chiroptical activities remains challenging. Here, we present a simple multiscale chiral synthesis and elucidate the underlying chemical mechanism for the self-assembly of achiral copper sulfide nanoparticles (NPs). The initially achiral NPs assemble into anisotropically twisted structures with a distinct handedness depending on the chirality of the molecules in the solution. Importantly, we reveal for the first time, to our knowledge, that metal ions act as messengers that transfer chirality information from small molecules to microstructures. The resulting multiscale chiral structures exhibit strong and broad chiroptical activities ranging from the ultraviolet to the infrared. This study not only enhances the understanding of the mechanism of chiral self-assembly but also offers effective approaches to producing chiral inorganic materials with strong chiroptical activities for next-generation chiral material-based applications.

Two-dimensional (2D) iron oxide-hydroxide (FeOOH) nanomaterials as low-cost and environmental-friendly composites are promising materials for application in heavy metal elimination. However, developing 2D FeOOH adsorbents with high adsorption capacity and excellent durability toward Cr (VI) removal is still a challenge due to the intrinsically non-layered structure. Here, a novel polyethyleneimine (PEI) functionalized 2D single-layer nano-raft-like α-FeOOH (α-FeOOH NF) consisted of parallel-aligned ultrathin nanowires was obtained via a facile one-pot hydrothermal approach. It was found that the 2D α-FeOOH NF nanostructure was formed by an in-plane iterative self-assembly mechanism, where α-FeOOH nanoparticles acted as intermediates and iterative seeds with anisotropic growth. The as-prepared 2D α-FeOOH NF possessed porous structure and high surface area, which provided a strong ability to capture the Cr (VI) ions in water. Benefiting from the unique structure and PEI modification, it exhibited fast adsorption kinetic rate, high reusability, and high adsorption capacity toward Cr(VI) removal. The removal mechanism involved adsorption and reduction process. Besides, the molecular dynamic simulations disclosed a facet-dependent Cr(VI) adsorption behavior of α-FeOOH. The maximum adsorption capacity was 67.1 mg/g and the removal efficiency still maintained 83.9 % in the fifth cycle. This work demonstrated that 2D α-FeOOH NF could be a promising adsorbent for Cr(VI) removal.

ConspectusChirality is ubiquitous in the universe and in living creatures over detectable length scales from the subatomic to the galactic, as exemplified in the two extremes by subatomic particles (neutrinos) and spiral galaxies. Between them are living creatures that display multiple levels of chirality emerging from hierarchically assembled asymmetric building blocks. Not too far from the bottom of this pyramid are the foundational building blocks with chiral atomic centers on sp3 carbon atoms exemplified by l-amino acids and d-sugars that are self-assembled into higher-order structures with increasing dimensions forming highly complex, amazingly functional, and energy-efficient living systems. The organization and materials employed in their construction inspired scientists to replicate complex living systems via the self-assembly of chiral components. Multiple studies pointed to unexpected and unique electromagnetic properties of chiral structures with nanoscale and microscale dimensions, including giant circular dichroism and collective circularly polarized scattering that their constituent units did not possess.To address the wide variety of chiral geometries observed in continuous materials, singular particles, and their complex systems, multiple analytic techniques are needed. Simultaneously, their spectroscopic properties create a pathway to multiple applications. For example, mirror-asymmetric vibrations at chiral centers formed by sp3 carbon atoms lead to optical activity for the infrared (IR) wavelength regions. At the same time, understanding the optical activity in, for example, the IR region enables biomedical applications because multiple modalities of biomedical imaging and vibrational optical activity (VOA) of biomolecules are known for IR range. In turn, VOA can be realized in both absorption and emission modalities due to large magnetic transition moments, as vibrational circular dichroism (VCD) or Raman optical activity (ROA) spectroscopy. In addition to the VOA, in the range of longer wavelengths, lattice vibrational mode or phononic behavior occurs in chiral crystals and nanoassemblies, which can be readily detected by terahertz circular dichroism (TCD) spectroscopy. Meanwhile, chiral self-assembly can induce circularly polarized light emission (CPLE) regardless of the existence of chirality in coassembled fluorophores. The CPLE from self-assembled chiral materials is particularly interesting because the CPLE can originate from both circularly polarized luminescence and circularly polarized scattering (CPS). Furthermore, because self-assembled nanostructures often exhibit stronger optical activity than their building blocks owing to dimension and resonance effects, the optical activity of single assembled nanostructures can be investigated by using microscopic technology combined with chiral optics. Here, we describe the state of the art for spectroscopic methods for the comprehensive analysis of chiral nanomaterials at various photon wavelengths, addressed with special attention given to new tools emerging both for materials with self-organized hierarchical chirality and single-particle spectroscopy.

A typical layered transition metal chalcogenide nanostructure, FeSe quantum dots (QDs) have recently begun to attract for their unique optical properties, i.e., multicolored excitation dependent emission (MEDE) property that breaks conventional Kasha -Vavilov rule as well as their potential applications in biological, and optical/electronic sensing and imaging. In this article, we present robust and optimized protocols for the scalable synthesis of FeSe QDs either in aqueous or organic syntheses. The synthesis conditions were carefully compared to obtain insistent synthesis parameters, e.g., solvents, precursors, stabilizers, pH, temperature, concentration, and reaction time after reproduction experiments. Furthermore, post-treatment procedures, i.e., phase transition and PEGylation are also optimized for further potential environmental and biological applications. In the scale-up experiments, a 5-liter reactor was utilized to produce approximately 55 g of QDs per batch, showing a robust optical MEDE property. The most optimized experimental condition reached quantum yield (QY) up to 60 % at the typical synthesis conditions of pH 9.0, 95degree celsius for 4 h of reflux, and the production yield of ca. 20%. These high fluorescent QDs can be potentially applied for biological fluorophores as well as next-generation QD displays.

Layered transition metal chalcogenide nanostructures reveal unprecedented electronic and optical properties due to the unusual arrangement of interlayers and electronic interactions between them. Here, we report layered FeSe nanoparticles (NPs) coupled by L- or D-cysteine as a chiral stabilizer to show multi-colored excitation dependent emission (MEDE) for both single-and two-photon photoluminescence breaking conventional Kasha and Vavilov rules of luminescence, which is the first report in inorganic nanostructure system. Structural analysis shows the chiral stabilizer-induced interlayer spacing expansion in a FeSe NP. The MEDE in FeSe NPs is revealed to originate from the impurity coupled to the Mott insulator character of FeSe and chiral interlayer expansion through the first-principles electronic structure calculations and the classical molecular dynamics. Taking advantage of biocompatibility and multiphoton excitation in FeSe NPs, MEDE was utilized for bio-imaging of neuron cells and tissues altering excitation wavelength from visible to near-infrared range expanding the capabilities of multi-color bio-labeling. (c) 2022 Elsevier Ltd. All rights reserved.

The second-harmonic generation (SHG) phenomenon, which readily supports the characteristic advantages of promising laser-based display systems, brings a new concept to advanced displays. Here, we demonstrate a laser projection display that utilizes the fabrication and design principles in individual micron-scale pixel arrays by depositing colloidal Se nanowires, a nonlinear optical nanomaterial for full-color light emission. Our system reveals the manufacturing process of planar light-emitting elements without the use of complex color segments, and the layout represents a full-color laser display with high-resolution pixels extracted from the combination of a pulsed femtosecond laser scanning process to access the frequency up-conversion technique based on a wavelength-tunable manner. The work presents attractive features for newly emerging multifunctional optical components composed of unique nanomaterials that can be applied for displays, bioimaging, and other optoelectronic devices.

Research on chiral nanomaterials (NMs) has grown radically with a rapid increase in the number of publications over the past decade. It has attracted a large number of scientists in various fields predominantly because of the emergence of unprecedented electric, optical, and magnetic properties when chirality arises in NMs. For applications, it is particularly informative and fascinating to investigate how chiral NMs interact with electromagnetic waves and magnetic fields, depending on their intrinsic composition properties, atomic distortions, and assembled structures. This review provides an overview of recent advances in chiral NMs, such as semiconducting, metallic, and magnetic nanostructures.

Chirality, the property whereby an object or a system cannot be superimposed on its mirror image, prevails amongst nature over various scales. Especially in biology, numerous chiral building blocks and chiral-specific interactions are involved in many essential biological activities. Despite the prevalence of chirality in nature, it has been no longer than 70 years since the mechanisms of chiral-specific interactions drew scientific attention and began to be studied. Owing to the advent of chiral-sensitive equipment such as circular dichroism spectrometers or chiral liquid columns for chromatography, it has recently been possible to achieve a deeper understanding of the chiral-specific interactions and consequential impacts on the functionality and efficiency of nanomedicine. From this point of view, it is worthwhile to examine previously reported chiral biomaterials with their compositions and possible applications to achieve new paradigms of biomaterials. This review discusses chiral materials on various scales and their biological applications.

Chiral nanomaterials provide a rich platform for versatile applications. Tuning the wavelength of polarization rotation maxima in the broad range including short-wave infrared (SWIR) is a promising candidate for infrared neural stimulation, imaging, and nanothermometry. However, the majority of previously developed chiral nanomaterials reveal the optical activity in a relatively shorter wavelength range (ultraviolet-visible, UV-vis), not in SWIR. Here, we demonstrate a versatile method to synthesize chiral copper sulfides using cysteine, as the stabilizer, and transferring the chirality from molecular- to the microscale through self-assembly. The assembled structures show broad chiroptical activity in the UV-vis-NIR-SWIR region (200-2500 nm). Importantly, we can tune the chiroptical activity by simply changing the reaction conditions. This approach can be extended to materials platforms for developing next-generation optical devices, metamaterials, telecommunications, and asymmetric catalysts.