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Nonresonant Polarized Raman Spectra Calculations of Nitrogen-Doped Single-Walled Carbon Nanotubes: Diameter, Chirality, and Doping Concentration Effects
摘要： Raman spectra of nitrogen-doped single-walled carbon nanotubes are calculated using the spectral moment’s method combined with the bond polarizability model. The influence of the nanotube diameter and chirality is investigated. We also address the important question of the effect of the N-doping concentration, and we propose an equation to estimate the doping concentration from the knowledge of the tube diameter and the frequency of the radial breathing mode.
关键词： spectral moment’s method,Raman spectra,N-doping concentration,nanotube diameter,nitrogen-doped single-walled carbon nanotubes,bond polarizability model,chirality
更新于2025-09-23 15:21:01
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Plasmonic Manipulation-Controlled Chiral Crystallization of Sodium Chlorate
摘要： Plasmonic manipulation using well-designed triangular trimeric gold nanostructures achieves giant crystal enantiomeric excess (CEE), more than 50%, of sodium chlorate (NaClO3). Stronger asymmetric interaction between molecule and light are pursued to reach high enantiomeric excess. The well-designed gold nanostructures immersed in a saturated NaClO3 D2O solution was irradiated with linear, left-hand, and right-hand circular polarizations of a 1064 nm continuous-wave laser. Within seconds of the start of the irradiation, an achiral metastable crystal was formed at the laser focus, and further irradiation induced a subsequent polymorphic transition to the chiral crystal. The crystal chirality is sensitive to the using handedness circular polarization, allowing for efficient enantioselectivity. The mechanisms to achieve this giant CEE are proposed based on the results of electromagnetic field analysis generated near the nanostructure by the Finite Element Method.
关键词： Plasmonic trapping,Crystal chirality,Crystal enantiomeric excess,Angular momentum,Gold nanostructure
更新于2025-09-23 15:21:01
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Vibrational Properties of Thiolate-Protected Gold Nanoclusters
摘要： Over recent years, the field of thiolate-protected gold nanoclusters has made remarkable progress. The successful determination of the structure of some of these clusters by X-ray crystallography was a milestone in this field. X-ray crystallography is arguably the most important technique in the field up to now, and it enabled the study of structure evolution as a function of cluster size. It also shed light on the structure of the Au?S interface. Recently, it has been realized that thiolate-protected gold clusters are very dynamic systems. Metal atoms and ligands can exchange easily between clusters. Furthermore, the adsorbed ligands bear conformational dynamics. Such dynamic effects call for experimental methods that can cope with it. Future efforts in this field will be directed toward applications of thiolate-protected clusters, and many of them will rely on dissolved clusters. Therefore, structure determination in solution is an important issue, though it is very challenging. The structure of the metal core and the Au?S interface is not expected to change in solution with respect to the crystal. However, the structure of the adsorbed ligand itself is sensitive to the environment and may be different in the solid state and in solution, as has been shown in fact in the past. It is this (dynamic) structure of the ligand that determines the interaction between the cluster and its environment, which is crucial, for example, for sensing applications. Vibrational spectroscopy is a promising technique to characterize thiolate-protected clusters in different environments. A vibrational spectrum is sensitive to structure (conformation) although this information is often 'hidden' in the spectrum, requiring detailed analysis and support from theory to be deciphered. Compared to other techniques like UV?vis spectroscopy and mass spectrometry, vibrational spectroscopy was not extensively used in the field of thiolate-protected clusters, but we believe that the technique will be very valuable for the future developments in the field.
关键词： vibrational spectroscopy,ligand conformation,thiolate-protected gold nanoclusters,Au?S interface,chirality transfer
更新于2025-09-23 15:21:01
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Central-to-Helical-to-Axial-to-Central Transfer of Chirality with a Photoresponsive Catalyst
摘要： Recent advances in molecular design have displayed striking examples of dynamic chirality transfer between various elements of chirality, e.g. from central to either helical or axial chirality and vice versa. While considerable progress in atroposelective synthesis has been made, it is intriguing to design chiral molecular switches able to provide selective and dynamic control of axial chirality with an external stimulus to modulate stereochemical functions. Here, we report the synthesis and characterization of a photoresponsive bis(2-phenol)-substituted molecular switch 1. The unique design exhibits a dynamic hybrid central-helical-axial transfer of chirality. The change of preferential axial chirality in the biaryl motif is coupled to the reversible switching of helicity of the overcrowded alkene core, dictated by the fixed stereogenic center. The potential for dynamic control of axial chirality was demonstrated by using (R)-1 as switchable catalyst to direct the stereochemical outcome of the catalytic enantioselective addition of diethylzinc to aromatic aldehydes, with successful reversal of enantioselectivity for several substrates.
关键词： atropisomers,photoresponsive catalyst,chirality transfer,photoisomerization,dynamic selectivity control,molecular switches
更新于2025-09-23 15:21:01
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Planar Chiral [2.2]Paracyclophanes: Optical Resolution and Transformation to Optically Active π-Stacked Molecules
摘要： In this article, recent our results on practical optical resolution methods of disubstituted and tetrasubstituted [2.2]paracyclophane compounds and their transformations are described. The obtained enantiopure [2.2]paracyclophane compounds have been used as chiral building blocks to prepare optically active π-stacked molecules. π-Stacked molecules construct optically active second-ordered structures, such as V-, N-, M-, X-, triangle-shaped, and one-handed double helical structures, due to the orientation of stacked π-electron systems. They emit circularly polarized luminescence (CPL) by photo-excitation. [2.2]Paracyclophane-based chiral π-stacked molecules in this article emit brightly owing to good photoluminescence (PL) quantum efficiencies as well as large molar extinction coefficients. In particular, emission is of course CPL with the large disymmetry factor (glum value). It is basically difficult to achieve CPL with high brightness, high PL efficiency, and large glum value by using other chiral scaffolds; therefore, planar chiral [2.2]paracyclophane is the ideal scaffold to be an excellent CPL emitters.
关键词： [2.2]Paracyclophane,Planar chirality,Circularly polarized luminescence
更新于2025-09-23 15:21:01
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Optical Chirality Sensing with an Auxiliary-free Earth-abundant Cobalt Probe
摘要： Broadly useful chiroptical ee sensing remains challenging and typically involves carefully designed molecular receptors or supramolecular assemblies. Herein, we describe enantioselective sensing of 35 amino acids, amino phosphonic acids, hydroxy acids, amino alcohols and diamines with an auxiliary-free cobalt probe. Chiroptical analysis of the enantiomeric composition and concentration of minute sample amounts is achieved with high accuracy using earth-abundant cobalt salts and hydrogen peroxide as oxidant. Despite the absence of an auxiliary ligand, the cobalt assay is applicable to aromatic and aliphatic compounds and yields strong CD signals at high wavelengths. This method eliminates the general prerequisite for chromophoric metal ligands to generate chiroptical signals via ECCD effects or through analyte-to-ligand chirality induction, and it offers operational simplicity, cost-efficiency, waste reduction and speed.
关键词： ee determination,concentration analysis,Werner complexes,Chirality sensing,chiroptical spectroscopy
更新于2025-09-23 15:21:01
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Chiral effects in low-cost plasmonic arrays of elliptic nanoholes
摘要： In this work we present an approach to induce chiral effects in well-known plasmonic nanohole arrays with triangular unit cell. Arrays with circular nanoholes in metals can exhibit interesting light-matter interaction mechanisms such as surface plasmon polaritons and extraordinary optical transmission. Moving from circular to elliptical shape and tilting the ellipse away from the lattice symmetry lines, a symmetry breaking induces a different absorption of the circularly polarized light of opposite handedness, i.e. circular dichroism. We numerically investigate circular dichroism at normal incidence in elliptic nanoholes in Au in the spectral range 400–1000 nm. We focus on its dependence on the elliptic nanohole tilt, and further proceed with the ellipse radii optimization. The optimized circular dichroism reaches 84%, and we report on the near field absorption distribution at the wavelengths of this maximum value.
关键词： Nanohole arrays,Enantiomers,Plasmonics,Chirality
更新于2025-09-23 15:19:57
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Gap plasmons inducing strong plasmonic chirality in planar metallic nanostructures
摘要： In this paper, an observation of chiral gap plasmons that induce strong optical chirality, spectroscopic circular dichroism (CD), and near-field enhancement in a planar metallic nanostructure is reported. The resulting chiral nanostructure consists of artificial gold nanoscale elements which are periodically fabricated on a glass substrate. The measured extinctions of the structure under linearly polarized light illumination are in good agreement with numerical calculations of extinction cross-sections. The dissymmetry of the extinctions under left- and right-handed circular polarization is correlated to the far-field CD of the chiral nanostructure that yields a strong CD of up to 0.02. Near-field enhancement of up to 20 times and a large local optical chirality is numerically found at a plane 5 nm above the chiral nanostructure. The finding of chiral gap plasmons that induce strong optical chirality is experimentally demonstrated to enhance interaction between achiral dye molecule and chiral gap plasmon, emitting circularly polarized luminescence with a dissymmetry factor of up to 0.15.
关键词： optical chirality,chiral nanostructures,circularly polarized luminescence,circular dichroism,gap plasmon
更新于2025-09-23 15:19:57
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Reconfigurable Plasmonic Chirality: Fundamentals and Applications
摘要： Molecular chirality is a geometric property that is of great importance in chemistry, biology, and medicine. Recently, plasmonic nanostructures that exhibit distinct chiroptical responses have attracted tremendous interest, given their ability to emulate the properties of chiral molecules with tailored and pronounced optical characteristics. However, the optical chirality of such human-made structures is in general static and cannot be manipulated postfabrication. Herein, different concepts to reconfigure the chiroptical responses of plasmonic nano- and micro-objects are outlined. Depending on the utilized strategies and stimuli, the chiroptical signature, the 3D structural conformation, or both can be reconfigured. Optical devices based on plasmonic nanostructures with reconfigurable chirality possess great potential in practical applications, ranging from polarization conversion elements to enantioselective analysis, chiral sensing, and catalysis.
关键词： plasmonics,optical spectroscopy,chirality,DNA origami,circular dichroism
更新于2025-09-23 15:19:57
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Helical Magnetic Field-Induced Real-Time Plasmonic Chirality Modulation
摘要： Astrophysical phenomenon mimetic helical magnetic field (hB)-assisted self-assembly is herein introduced to build helical superstructures that display chiroptical properties. As a building block, magnetoplasmonic (MagPlas) Ag@Fe3O4 core-shell nanoparticles are used to guide plasmonic Ag nanoparticles onto a helical magnetic flux. The chirality of the assembled helical structures and tailored circular dichroism are successfully tuned in real-time, and the handedness of the assembled structures is dynamically switched by the hB at the millisecond level, which is at least 6,000-fold faster than other template-assisted methods. The peak position of circular dichroism can be reconfigured by altering the plasmonic resonance or coupling by controlling the size of the Ag core and magnetic flux density. The hB-induced chirality modulation represents a method to control the polarization state of light at the nexus of plasmonics, magnetic self-assembly, colloidal science, liquid crystals, and chirality. It presents active and dynamic chiral assemblies of magnetoplasmonic nanomaterials, enabling further practical applications in optical devices.
关键词： magnetoplasmonic nanoparticles,helical magnetic field (hB),self-assembly,dynamic chirality,real-time modulation
更新于2025-09-23 15:19:57