Cu2+-Dominated Chirality Transfer from Chiral Molecules to Concave Chiral Au Nanoparticles.

Foreign ions as additives are of great significance for realizing excellent control over the morphology of noble metal nanostructures in the state-of-the-art seed-mediated growth method; however, they remain largely unexplored in chiral synthesis. Here, we report on a Cu2+-dominated chiral growth strategy that can direct the growth of concave chiral Au nanoparticles with C3-dominant chiral centers. The introduction of trace amounts of Cu2+ ions in the seed-mediated chiral growth process is found to dominate the chirality transfer from chiral molecules to chiral nanoparticles, leading to the formation of chiral nanoparticles with a concave VC geometry. Both experimental and theoretical results further demonstrate the correlation between the nanoparticle structure and optical chirality for the concave chiral nanoparticle. The Cu2+ ion is found to dominate the chiral growth by selectively activating the deposition of Au atoms along the [110] and [111] directions, facilitating the formation of the concave VC. We further demonstrate that the Cu2+-dominated chiral growth strategy can be employed to generate a variety of concave chiral nanoparticles with enriched geometric chirality and desired chiroptical properties. Concave chiral nanoparticles also exhibit appealing catalytic activity and selectivity toward electrocatalytic oxidation of enantiomers in comparison to helicoidal nanoparticles. The ability to tune the geometric chirality in a controlled manner by simply manipulating the Cu2+ ions as additives opens up a promising strategy for creating chiral nanomaterials with increasing architectural diversity for chirality-dependent optical and catalytic applications.

Multicomponent chiral plasmonic hybrid nanomaterials: recent advances in synthesis and applications.

Chiral hybrid nanomaterials with multiple components provide a highly promising approach for the integration of desired chirality with other functionalities into one single nanoscale entity. However, precise control over multicomponent chiral plasmonic hybrid nanomaterials to enable their application in diverse and complex scenarios remains a significant challenge. In this review, our focus lies on the recent advances in the preparation and application of multicomponent chiral plasmonic hybrid nanomaterials, with an emphasis on synthetic strategies and emerging applications. We first systematically elucidate preparation methods for multicomponent chiral plasmonic hybrid nanomaterials encompassing the following approaches: physical deposition approach, galvanic replacement reaction, chiral molecule-mediated, chiral heterostructure, circularly polarized light-mediated, magnetically induced, and chiral assembly. Furthermore, we highlight emerging applications of multicomponent chiral plasmonic hybrid nanomaterials in chirality sensing, enantioselective catalysis, and biomedicine. Finally, we provide an outlook on the challenges and opportunities in the field of multicomponent chiral plasmonic hybrid nanomaterials. In-depth investigations of these multicomponent chiral hybrid nanomaterials will pave the way for the rational design of chiral hybrid nanostructures with desirable functionalities for emerging technological applications.

Tuning the Plexcitonic Optical Chirality Using Discrete Structurally Chiral Plasmonic Nanoparticles.

Constructing chiral plexcitonic systems with tunable plasmon-exciton coupling may advance the scientific exploitation of strong light-matter interactions. Because of their intriguing chiroptical properties, chiral plasmonic materials have shown promising applications in photonics, sensing, and biomedicine. However, the strong coupling of chiral plasmonic nanoparticles with excitons remains largely unexplored. Here we demonstrate the construction of a chiral plasmon-exciton system using chiral AuAg nanorods and J aggregates for tuning the plexcitonic optical chirality. Circular dichroism spectroscopy was employed to characterize chiral plasmon-exciton coupling, in which Rabi splitting and anticrossing behaviors were observed, whereas the extinction spectra exhibited less prominent phenomena. By controlling the number of molecular excitons and the energy detuning between plasmons and excitons, we have been able to fine-tune the plexcitonic optical chirality. The ability to fine-tune the plexcitonic optical chirality opens up unique opportunities for exploring chiral light-matter interactions and boosting the development of emerging chiroptical devices.

Chiral Au-Pd Alloy Nanorods with Tunable Optical Chirality and Catalytically Active Surfaces.

Integrating the plasmonic chirality with excellent catalytic activities in plasmonic hybrid nanostructures provides a promising strategy to realize the chiral nanocatalysis toward many chemical reactions. However, the controllable synthesis of catalytically active chiral plasmonic nanoparticles with tailored geometries and compositions remains a significant challenge. Here it is demonstrated that chiral Au-Pd alloy nanorods with tunable optical chirality and catalytically active surfaces can be achieved by a seed-mediated coreduction growth method. Through manipulating the chiral inducers, Au nanorods selectively transform into two different intrinsically chiral Au-Pd alloy nanorods with distinct geometric chirality and tunable optical chirality. By further adjusting several key synthetic parameters, the optical chirality, composition, and geometry of the chiral Au-Pd nanorods are fine-tailored. More importantly, the chiral Au-Pd alloy nanorods exhibit appealing chiral catalytic activities as well as polarization-dependent plasmon-enhanced nanozyme catalytic activity, which has great potential for chiral nanocatalysis and plasmon-induced chiral photochemistry.

Geometric Control and Optical Properties of Intrinsically Chiral Plasmonic Nanomaterials.

Intrinsically chiral plasmonic nanomaterials exhibit intriguing geometry-dependent chiroptical properties, which is due to the combination of plasmonic features with geometric chirality. Thus, chiral plasmonic nanomaterials have become promising candidates for applications in biosensing, asymmetric catalysis, biomedicine, photonics, etc. Recent advances in geometric control and optical tuning of intrinsically chiral plasmonic nanomaterials have further opened up a unique opportunity for their widespread applications in many emerging technological areas. Here, the recent developments in the geometric control of chiral plasmonic nanomaterials are reviewed with special attention given to the quantitative understanding of the chiroptical structure-property relationship. Several important optical spectroscopic tools for characterizing the optical chirality of plasmonic nanomaterials at both ensemble and single-particle levels are also discussed. Three emerging applications of chiral plasmonic nanomaterials, including enantioselective sensing, enantioselective catalysis, and biomedicine, are further highlighted. It is envisioned that these advanced studies in chiral plasmonic nanomaterials will pave the way toward the rational design of chiral nanomaterials with desired optical properties for diverse emerging technological applications.

Site-Selective Chiral Growth of Anisotropic Au Triangular Nanoplates for Tuning the Optical Chirality.

Site-selective chiral growth of anisotropic nanoparticles is of great importance to realize the plasmonic nanostructures with delicate geometry and desired optical chirality; however, it remains largely unexplored. This work demonstrates a controlled site-selective chiral growth system based on the seed-mediated growth of anisotropic Au triangular nanoplates. The site-selective chiral growth involves two distinct underlying pathways, faceted growth and island growth, which are interswitchable upon maneuvering the interplay of chiral molecules, surfactants, and reducing agents. The pathway switch governs the geometric and chirality evolution of Au triangular nanoplates, giving rise to tailorable circular dichroism spectra. The ability to tune the optical chirality in a controlled manner by manipulating the site-selective chiral growth pathway opens up a promising strategy for exploiting chiral metamaterials with increasing architectural complexity in chiroptical applications.

Tunable Reversal of Circular Dichroism in the Seed-Mediated Growth of Bichiral Plasmonic Nanoparticles.

Plasmonic nanoparticles with an intrinsic chiral structure have emerged as a promising chiral platform for applications in biosensing, medicine, catalysis, separation, and photonics. Quantitative understanding of the correlation between nanoparticle structure and optical chirality becomes increasingly important but still represents a significantly challenging task. Here we demonstrate that tunable signal reversal of circular dichroism in the seed-mediated chiral growth of plasmonic nanoparticles can be achieved through the hybridization of bichiral centers without inverting the geometric chirality. Both experimental and theoretical results demonstrated the opposite sign of circular dichroism of two different bichiral geometries. Chiral molecules were found to not only contribute to the chirality transfer from molecules to nanoparticles but also manipulate the structural evolution of nanoparticles that synergistically drive the formation of two different chiral centers. By deliberately adjusting the concentration of chiral molecules and other synthetic parameters, such as the reducing agent concentration, the capping surfactant concentration, and the amount of Au precursor, we have been able to fine-tune the circular dichroism reversal of bichiral Au nanoparticles. We further demonstrate that the structure of chiral molecules and the crystal structure of Au seeds play crucial roles in the formation of Au nanoparticles with bichiral centers. The insights gained from this work not only shed light on the underlying mechanisms dictating the intriguing geometric and chirality evolution of bichiral plasmonic nanoparticles but also provide an important knowledge framework that guides the rational design of bichiral plasmonic nanostructures toward chiroptical applications.

Copper fumarate with high-bifunctional nanozyme activities at different pH values for glucose and epinephrine colorimetric detection in human serum.

Metal-organic frameworks (MOFs) have attracted extensive attention for the development of colorimetric detection methods due to their ease of modification and high density of active sites. However, most of the reported colorimetric sensors based on MOFs show only a single nanozyme activity. Herein, the bifunctional enzyme activities of a hexagonal prism Cu MOF with fumaric acid as the ligand (Cu FMA), namely laccase-like activity under alkaline conditions (pH = 8) and peroxidase-like activity under acidic conditions (pH = 4), were verified. The specificity of Cu FMA at different pH values may be due to the presence of the Cu+ active center introduced by the weak reducibility of FMA. At pH = 8, Cu+ active centers are beneficial for dissociating the H-O bonds of phenolic compounds for the laccase system. In contrast, the dissociation of H-O is weakened at pH = 4, which prompts the breaking of the O-O bonds of H2O2 as a Fenton-like reaction for the peroxidase system. Based on the dual enzyme activities, Cu FMA sensors exhibit outstanding detectability for epinephrine and glucose with linear ranges of 2.7-54.6 µM and 0.01-0.8 mM and detection limits of 1.1 µM and 2.28 × 10-7 M, respectively. The Cu FMA colorimetric sensor can be applied for detecting and measuring glucose and epinephrine in human serum samples. This work paves the way for Cu MOFs to be used as the basis for rational regulation of the activity of dual nanozymes and for multifunctional applications under completely independent conditions.

Spinel Zn3V3O8 nanosheets via a one-step hydrothermal synthesis with peroxidase-like activity for high sensitivity glucose colorimetric detection in synthetic perspiration.

Due to their specific spinel structure, ternary oxides with multi-catalytic sites on a highly active exposed surface are recommended as alternative bio-catalysts. Spinel zinc vanadate with two-dimensional nanosheets (Zn3V3O8 NSs) was synthesised using a one-step hydrothermal route with CTAB and glycine as a bi-surfactant, where each NS has a thin thickness (25 nm) and wide cross section (2 µm). As a key parameter for peroxidase-like activity, the Michaelis-Menten constant (Km) for Zn3V3O8 NSs was calculated to be 0.271 mM with TMB and 1.317 mM with H2O2 at optimum conditions, indicating a higher affinity for the exposed (011) facet towards horseradish peroxidases. This affinity is related to the geometric matching between V4+ active sites and the terminal amino groups of TMB. The V4+ ions on the (011) facet act as dangling bonds and readily react with H2O2 in a Fenton-like reaction. The peroxidase-like activity for Zn3V3O8 NSs is verified by the formation of [V(IV)-OO˙] by the ˙O2- and V5+ near V4+ sites, but oxidase activity for Zn3V3O8 NSs. Based on the peroxidase-like activity, Zn3V3O8 NSs were used as a colorimetric glucose sensor with a wide linear range from 0.01 to 0.5 mM and a detection limit (LOD = 3σ/S) of 2.81 × 10-7 M. The colorimetric sensor also exhibited high accuracy and selectivity in synthetic perspiration samples.