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Plasmonic chiral nanostructures provide a novel route for extraordinary optical properties, such as light polarization control and enhancing chiroptical signals of molecules. The symmetry of chiral nanostructures, such as helices, gyroids, and irregular tetrahedrons, is strongly correlated to chiroptical responses; therefore, it is an important design parameter. In a previous study, a synthetic strategy is demonstrated for 432‐symmetric chiral gold nanoparticles by breaking the mirror symmetry of a 4/m3¯$\overline 3 $ 2/m‐symmetric crystal structure on a high‐index surface. Herein, the aim is to extend the chiral symmetry of gold nanoparticles and their chiroptical responses. The symmetry of gold nanoparticles can be modulated by inducing single or multiple twin planes in seed nanoparticles. The 32‐symmetric chiral gold nanoplates, referred to as 32 helicoids, are successfully synthesized using 3 2/m‐symmetric triangular and hexagonal plates. The growth mechanism of the 32 helicoids, which results in two different characteristic morphologies, is analyzed. The 32 helicoids are significantly important owing to their optical activity over a wide range from the visible to the near‐infrared region. This investigation provides an insight that symmetry control of the nanomorphology can represent an important research direction in chiral plasmonic applications. [ABSTRACT FROM AUTHOR]

Chiral nanophotonic platforms provide a means of creating near fields with both enhanced asymmetric properties and intensities. They can be exploited for optical measurements that allow enantiomeric discrimination at detection levels > 6 orders of magnitude than is achieved with conventional chirally sensitive spectroscopic methods based on circularly polarized light. Here it is shown that surface enhanced Raman spectroscopy (SERS) is such a local probe of the near field environment. It is used to achieve enantiomeric discrimination of chiral helicoid nanoparticles deposited on left‐ and right‐handed enantiomorphs of a chiral metafilm using an achiral molecule as a probe. "Hotter" electromagnetic (EM) hotspots are created for matched combinations of helicoid and metafilms (left‐left and right‐right), while mismatched combinations leads to significantly "cooler" electromagnetic hotspots. This large enantiomeric dependency on hotspot intensity is readily detected using SERS with the aid of an achiral Raman reporter molecule. In effect SERS is used to distinguish between the different EM environments of the plasmonic diastereomers produced by mixing chiral nanoparticles and metafilms. The work demonstrates that by combining chiral nanophotonic platforms with established SERS strategies new avenues in ultrasensitive chiral detection can be opened. [ABSTRACT FROM AUTHOR]

In manufacturing C−N bond‐containing compounds, it is an important challenge to alternate the conventional methodologies that utilize reactive substrates, toxic reagents, and organic solvents. In this study, we developed an electrochemical method to synthesize a C−N bond‐containing molecule avoiding the use of cyanides and amines by harnessing nitrate (NO3−) as a nitrogen source in an aqueous electrolyte. In addition, we utilized oxalic acid as a carbon source, which can be obtained from electrochemical conversion of CO2. Thus, our approach can provide a route for the utilization of anthropogenic CO2 and nitrate wastes, which cause serious environmental problems including global warming and eutrophication. Interestingly, the coreduction of oxalic acid and nitrate generated reactive intermediates, which led to C−N bond formation followed by further reduction to an amino acid, namely, glycine. By carefully controlling this multireduction process with a fabricated Cu–Hg electrode, we demonstrated the efficient production of glycine with a faradaic efficiency (F.E.) of up to 43.1 % at −1.4 V vs. Ag/AgCl (current density≈90 mA cm−2). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Scalable and facile synthesis of highly active alkaline hydrogen evolution reaction catalysts was demonstrated by controlling the microstructures of Al–Ni alloys and making porous foam and powder. The microstructures were carefully controlled in the binary alloys and the subsequent selective etching resulted in highly active catalysts, which are comparable to conventional Pt-based catalysts. Large-scale coating of a dealloyed Al–Ni alloy powder was also demonstrated, showing the practical applicability of this method. [ABSTRACT FROM AUTHOR]

Finding a novel method to generate a chiral plasmonic material has been highlighted in the last decades for its unique light‐matter interactions. Recently, an aqueous based peptide directed synthesis of chiral plasmonic gold nanoparticle with exceptional chiroptic response has been reported. Especially, the facile and precise control of chirality using biomolecules allows potential expansion of chiral metamaterial synthesis. In this work, we show a significant enhancement of chiroptic response by simultaneous introduction of multiple bio‐molecular chiral modifiers, glutathione and homooligonucleotide containing thymine. Compared to previously synthesized single chiral plasmonic nanoparticles using only glutathione molecules, further addition of an oligonucleotide into the growth solution induces a two‐fold increase of dissymmetric factor. We believe that the presented synthetic method proposes an effective route of chiral metamaterial morphology and property control for versatile applications. [ABSTRACT FROM AUTHOR]

An electrokinetic analysis of electrochemical CO2 reduction reactions provides information about the decoupled involvement of electron–proton transfer from the Tafel slope and reaction order analyses. Conventionally, a one-electron transfer to CO2 and a chemical proton transfer from HCO3− have been considered to be typical rate-limiting steps. These suggested reaction mechanisms are justified under several assumptions: (1) the bicarbonate ion is a major proton donor, (2) the gaseous CO2 is a carbon source, (3) the reaction mechanism is unaffected by the applied potentials outside the Tafel region, etc. However, recent electrokinetic studies combined with in situ and isotopic experiments raise a question that the above conventional assumptions may not always be valid. Furthermore, there are unresolved issues between the mechanisms suggested by electrokinetic studies. In this review, reported reaction mechanisms of the CO2 reduction reaction are summarized with CO and HCOO− formation as model reaction systems. The reaction pathways are also discussed with a theoretical consideration. A deep investigation into the mechanisms reveals the complex feature of reaction pathways and the difficulty in suggesting the mechanism solely from an electrokinetic analysis. [ABSTRACT FROM AUTHOR]

New morphology of palladium nanoparticles is demonstrated by utilizing the interaction of amino acid and palladium metallic surface. Chiral cysteine molecules induce chiral spiral structure evolution. The resulting spiral palladium nanoparticles show rotational direction preference with respect to the handedness of the added cysteine molecule. The strong correlation of the resulting morphologies with surfactant and cysteine concentration exists for effective generation of chirality. Synthesized chiral palladium nanoparticles are around 100 nm sized cubic based nanoparticles with each face of the cube containing a spiral structure. Generation of nanoparticle morphology is studied through growth of time‐dependent morphology evolution with statistical analysis of spiral structure formation. The reported synthesis method can provide a new route to nanomaterial design for enantioselective catalysis and sensing. [ABSTRACT FROM AUTHOR]

Ultrasensitive, rapid, and reliable biomolecular sensing is essential for biomedical diagnostics, requiring real-time monitoring and detection of trace samples. Optical sensing, particularly plasmonic biosensing, meets these demands through noninvasive, high-sensitivity detection based on the interaction between light and molecules. Here, we present novel plasmonic metamaterial-based sensing strategy, utilizing the circular dichroism (CD) response of grating-coupled surface plasmon resonance (SPR) from chiral nanoparticle grating structure (i.e., 2D helicoid crystal) on gold substrate. Strong chiroptic response of helicoids has been effectively expanded to produce a remarkable CD/ g reflection response in the SPR mode, achieved by spectral coupling of SPR with localized surface plasmon resonance (LSPR) in helicoids. This CD response, derived from the differential of left and right circularly polarized light, corrects optical fluctuations, enhancing sensitivity and reliability. Our SPR-CD-based approach achieves a sensitivity of 379.2 nm/RIU and detection limit of a few mM for d-glucose, offering a new paradigm for high-performance optical biosensors.

Chiral inorganic nanomaterials hold significant promise for various applications, including enantioselective catalysis, polarization-controlling optical devices, metamaterials, and enantioselective molecular sensors. In our previous work, we presented a method for synthesizing chiral Au 432 helicoid III (Au helicoids) from peptides and amino acids, where helical gaps are intricately arranged with 432 symmetry within single cubic nanoparticles. In this study, we have achieved the fabrication of chiral silica molds through Au etching subsequent to the silica coating of Au helicoids. We demonstrate that these molds serve as geometrically confined reactors capable of producing chiral Ag, Pd, and Pt 432 helicoid III (Ag, Pd, and Pt helicoids). The morphology of the synthesized Ag, Pd, and Pt helicoids closely resembles that of the Au helicoids, exhibiting a superior g-factor compared to other reported chiral structures of each material. Notably, the Ag and Pd helicoids are found to be single-crystalline, with high-index planes exposed within the gaps. We believe that this silica mold-based approach can be generalized to synthesize chiral nanomaterials of various metal and even oxide materials.

The water oxidation reaction, the most important reaction for hydrogen production and other sustainable chemistry, is efficiently catalyzed by the Mn 4 CaO 5 cluster in biological photosystem II. However, synthetic Mn-based heterogeneous electrocatalysts exhibit inferior catalytic activity at neutral pH under mild conditions. Symmetry-broken Mn atoms and their cooperative mechanism through efficient oxidative charge accumulation in biological clusters are important lessons but synthesis strategies for heterogeneous electrocatalysts have not been successfully developed. Here, we report a crystallographically distorted Mn-oxide nanocatalyst, in which Ir atoms break the space group symmetry from I 4 1 / amd to P1. Tetrahedral Mn(II) in spinel is partially replaced by Ir, surprisingly resulting in an unprecedented crystal structure. We analyzed the distorted crystal structure of manganese oxide using TEM and investigated how the charge accumulation of Mn atoms is facilitated by the presence of a small amount of Ir.

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 & Co. KGaA, Weinheim.)

The electrochemical reduction of carbon dioxide (CO 2 ) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO 2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO 2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO 2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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.

While Cu electrodes are a versatile material in the electrochemical production of desired hydrocarbon fuels, Cu binary alloy electrodes are recently proposed to further tune reaction directionality and, more importantly, overcome the intrinsic limitation of scaling relations. Despite encouraging empirical demonstrations of various Cu-based metal alloy systems, the underlying principles of their outstanding performance are not fully addressed. In particular, possible phase segregation with concurrent composition changes, which is widely observed in the field of metallurgy, is not at all considered. Moreover, surface-exposed metals can easily form oxide species, which is another pivotal factor that determines overall catalytic properties. Here, the understanding of Cu binary alloy catalysts for CO 2 reduction and recent progress in this field are discussed. From the viewpoint of the thermodynamic stability of the alloy system and elemental mixing, possible microstructures and naturally generated surface oxide species are proposed. These basic principles of material science can help to predict and understand metal alloy structure and, moreover, act as an inspiration for the development of new binary alloy catalysts to further improve CO 2 conversion and, ultimately, achieve a carbon-neutral cycle., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Electrocatalytic conversion of CO 2 into a long-chain hydrocarbon represents an important research direction in adding value to CO 2 -based chemicals and realizing its practical application. Long-chain hydrocarbons may change the current fossil fuel-based industry in that those chemicals have a similar energy density as gasoline, high compatibility with the current infrastructure, and low hydroscopicity for pipeline distribution. However, most of the electrocatalysts produce C 1 , C 2 , and C 3 chemicals, and methods for producing long-chain hydrocarbons are not available thus far. Interestingly, nature utilizes many enzymes to generate long-chain hydrocarbons using C 2 building blocks and suggests key mechanisms, inspiring new perspective in the design of electrocatalysts. In this Perspective, we present case studies to demonstrate how CO 2 and its reductive derivatives interact with the electrode surface during C-C bond formation and introduce how these issues are addressed in biological systems. We end this Perspective by outlining possible strategies to translate the natural mechanism into a heterogeneous electrode.