Optically Active Research Articles

Exploring the dual role of BiVO4 nanoparticles: unveiling enhanced antimicrobial efficacy and photocatalytic performance

Abstract This study was focused on enhancing the structural, optical, antimicrobial, and photocatalytic activities of bismuth vanadate (BiVO4) nanoparticles. The current study utilized a simple hydrothermal technique to fabricate BiVO4 nanoparticles. Several techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, Field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and ultraviolet-visible (UV-Vis), were used to examine BiVO4. The monoclinic structure of BiVO4 was confirmed through XRD, XPS, and Raman analysis, validating its high purity and the absence of secondary phases with a size of 31 nm. The decahedral structure and purity of BiVO4 were revealed through FESEM-EDS microstructure and surface morphology examination. A band gap of 2.36 eV was exhibited by the synthesized BiVO4 nanoparticles. The conduction band minimum and valence band maximum edge potentials were found to be 2.715 eV and 0.355 eV, respectively. The antimicrobial properties of BiVO4 NPs were evaluated using the disc diffusion method on a broad spectrum of pathogens. Various bacterial and fungal pathogens showed broad-spectrum antimicrobial activity against BiVO4, indicating that BiVO4 nanoparticles (NPs) could be effective antimicrobial agents. In addition, the photocatalytic performance of BiVO4 and its degradation efficiency were investigated with Oxytetracycline (OTC), tetracycline (TC), and doxycycline (DC) antibiotics under visible light. The photocatalytic degradation results demonstrated that BiVO4 successfully degraded the antibiotic residuals. The results showed that the hydrothermally synthesized BiVO4 nanoparticles have great potential for use in biological and environmental applications. Graphical Abstract

Growth, Characterization and Nonlinear Optical Activities of some Chalcones Derivatives

Growth, Characterization and Nonlinear Optical Activities of some Chalcones Derivatives

Angle‐Tolerant Circular Eigenpolarizations Enabled by Orientational Disorder in Dielectric Metasurfaces

AbstractTailored structural disorder in photonic metasurfaces enables advanced light shaping. Specifically, an orientational disorder in chiral nanostructures leads to circular eigenpolarizations with a heavily suppressed linear birefringence. The orientational disorder is, therefore, vital to observing purely chiroptical effects such as circular dichroism and optical activity. Here, it is experimentally and numerically demonstrated that all‐dielectric orientationally disordered chiral bilayer square array metasurfaces preserve highly circular eigenpolarizations for a wide range of incidence angles. The angle‐dependent performance of disordered chiral metasurfaces is compared with that of their C2 and C4 symmetric periodic counterparts, demonstrating that the disordered structures provide nearly pure circular eigenpolarizations across a larger range of angles and wavelengths, whereas the periodic ones do not. These findings underscore the ability of tailored disorder to enhance the robustness of engineered chiroptical responses of all‐dielectric metasurfaces and highlight its potential for flat, integrable, and highly efficient optical components, such as circular polarizers and beam splitters.

Photo-induced chirality in a nonchiral crystal.

Chirality, a pervasive form of symmetry, is intimately connected to the physical properties of solids, as well as the chemical and biological activity of molecular systems. However, inducing chirality in a nonchiral material is challenging because this requires that all mirrors and all roto-inversions be simultaneously broken. Here, we show that chirality of either handedness can be induced in the nonchiral piezoelectric material boron phosphate (BPO4) by irradiation with terahertz pulses. Resonant excitation of either one of two orthogonal, degenerate vibrational modes determines the sign of the induced chiral order parameter. The optical activity of the photo-induced phases is comparable to the static value of prototypical chiral α-quartz. Our findings offer new prospects for the control of out-of-equilibrium quantum phenomena in complex materials.

Synergistic Control of Ferroelectric and Optical Properties in Molecular Ferroelectric for Multiplexing Nonvolatile Memory.

Utilizing the correlation among diverse physical properties to facilitate multiplexing and multistate memory is anticipated to emerge as an efficient strategy to enhance memory capacity, achieve device miniaturization, and ensure information security. As an important functional material, ferroelectrics have long been considered as a potential candidate in multistate memory devices. Furthermore, the integration of optical response offers an alternative path to realizing multiplexing features, further enhancing the versatility and efficiency of these devices. However, combining ferroelectricity and optical activity is always challenging because ferroelectricity is very sensitive to the crystal structure. In this study, on the correlation between ferroelectric polarization (FP) and optical properties in molecular ferroelectric material, trimethylchloromethyl ammonium trichloromanganese (TMCM-MnCl3) is reported. This research demonstrated that the FP can modulate the photoluminescence (PL) emission, while optical illumination can trigger FP reversal. Based on these, both electric-writing optical-reading (EWOR) and optical-writing electrical-reading (OWER) modes have been conclusively established, and the seamless transition between these two modes can be achieved by adjusting the excitation light intensity. These findings reveal an intriguing physical interconnection and imply the viability of implementing multiplexing and multistate memory functionalities in systems based on ferroelectrics.

Chiral correlated-plasmons enhanced Raman optical activity from spin-polarized, correlated s band in highly oriented single-crystalline gold quantum-dots

Chiral correlated-plasmons enhanced Raman optical activity from spin-polarized, correlated <i>s</i> band in highly oriented single-crystalline gold quantum-dots

First-Principles Calculations of Group-IV Carbide Quantum Dots and Single-Layer Heterojunctions with Optical Activity and Short-Wave Infrared Emission for Efficient Gas Sensing

First-Principles Calculations of Group-IV Carbide Quantum Dots and Single-Layer Heterojunctions with Optical Activity and Short-Wave Infrared Emission for Efficient Gas Sensing

Unprecedented Ultraviolet Circularly Polarized Light-Dependent Anomalous Photovoltaics in Chiral Hybrid Perovskites.

Circularly Polarized Light (CPL)-dependent anomalous photovoltaic effect (APVE), characterized by light helicity-manipulated steady photocurrent and above-bandgap photovoltage, has demonstrated significant potential in the fields of photoelectronic and photovoltaics. However, exploiting CPL-dependent APVE in chiral hybrid perovskites, a promising family with intrinsic chiroptical activity and non-centrosymmetric structure, remains challenging. Here, leveraging the flexible structural design of chiral alternating cations intercalation-type perovskites, CPL-dependent APV, for the first time, is achieved in chiral perovskites. Specifically, by introducing lone pair electrons into the organic layers to greatly amplify the polarization, [(R)-PPA](MOPA)PbBr4 (2-R) (PPA = 1-phenylpropylammonium, MOPA = 3-methoxypropylammonium) exhibit intrinsic APVE with an above-bandgap photovoltage of 6.50V (Eg = 3.01eV) under ultraviolet (UV) light illumination. Strikingly, profiting from the natural chiral optical activity of chiral perovskites, unprecedented UV CPL-dependent APV is realized in 2-R, driving the high distinguishability between right-hand and left-hand CPLs with a large anisotropy factor (gIph) of 0.33. This study pioneers the realization of CPL-dependent APV within chiral perovskite, promising significant advancements in optoelectronic device technologies.

Alkali-Cation-Selective Arylation Promoted by Ion Recognition of Foldamers.

To explore alkali-cation selectivity at the chemical reaction level, in this work, we for the first time focused on the different behaviors of potassium and sodium ions in intra- and intermolecular arylation. We prepared a series of aromatic foldamers based on pyridine/oxadiazole alternating sequences as the catalysts for the arylation. Our studies revealed that foldamers can selectively recognize K+ over Na+ and the interactions between foldamers and K+ drive the arylation with a significant yield. In contrast, no trace of the product can be found with Na+. Furthermore, foldamers, with biased handedness, can afford products with optical activity. The balance between two enantiomers of products can be freely controlled by the different conformations of foldamers.

Resolving Artifacts and Improving the Detection Limit in Circular Differential Scattering Measurement of Chiral and Achiral Gold Nanorods.

Circular differential scattering (CDS) spectroscopy has been developed as a powerful method for the characterization of the optical activity of individual plasmonic nanostructures and their complexes with chiral molecules. However, standard measurement setups often result in artifacts that have long raised concerns on the interpretation of spectral data. In fact, the detection limit of CDS setups is constrained by the high level of artifacts, to ±10%. We address this issue by means of a detailed theoretical description of changes in the polarization state when circularly polarized light is reflected at a dark-field condenser. As a result, we propose a modified CDS configuration based on sequentially placing the quarter-wave plate and linear polarizer within the detection optical path, to analyze the circular polarization state of the light scattered by individual particles. Extensive analysis demonstrates a detection limit of ±1.5% for the modified configuration, which is significantly lower than that for the conventional setup. As a standard system for CDS measurements, both achiral and chiral gold nanorods (AuNRs) were characterized using both setups. With achiral AuNRs, linear dichroism (LD) artifacts in the conventional setup are found to originate from LD present in the excitation light and are only present if anisotropic excitation is produced as a result of the misalignment of the excitation light to the condenser. With chiral AuNRs, CDS spectra recorded with the conventional setup depend on the orientation of the chiral AuNRs with respect to the x-axis of the microscope and are reversed compared to those on the colloid and measured in the modified configuration. The results are in good agreement with theoretical simulations for both configurations.

Unveiling the Racemization in Ferroelectrics with Coupled Ferroelectricity and Optical Activity.

The most distinctive features of ferroelectrics are spontaneous polarization and depolarization. Ferroelectricity was first observed in Rochelle salt, a compound with a chiral component in which the molecular chirality is not affected by depolarization. For structurally chiral ferroelectrics (SCFs), such as triglycine sulfate, which lacks chiral components, the depolarization effect on chirality presents an intriguing and unexplored topic. In this study, we focus on a newly proposed chiral optical topic in optically active ferroelectrics with coupled ferroelectricity and optical activity. We examined the depolarization effect on the optical activity in these ferroelectric materials and employed chiral-environment crystallization and solid-state circular dichroism (CD) techniques to elucidate the racemization-depolarization mechanism in an SCF for the first time. For polar and nonchiral optically active ferroelectrics, optical activity is averaged out in the powder state, resulting in no CD signal. Additionally, we experimentally validated the consistency between CD measurements and optical activity theory across the four optically active point groups (m, mm2, 4̅, 4̅2m). These findings could advance the development of chiral spintronic devices by leveraging coupled ferroelectricity and optical activity to tune the spin selectivity.

Breaking Performance Barriers in KBe2BO3F2 (KBBF) Analogs by Functional Group Self‐Polymerization

AbstractEnhancing the conversion efficiency of all‐solid‐state lasers through the rational design of crystal materials with superior linear and nonlinear optical (NLO) properties remains a formidable challenge. Herein, we present a novel approach to optimizing these properties in KBe2BO3F2 (KBBF)‐analog crystals via functional group self‐polymerization. This strategy led to the synthesis of two new optical crystals: noncentrosymmetric CsAs2O3Br and centrosymmetric CsAs4O6Br. By incorporating highly optically active [AsO3]3− units into the classical 2D [Be2BO3F]∞− framework, we facilitated the self‐assembly of [As2O3]∞ layers, forming a densely packed and highly ordered structure that enhances macroscopic optical activity. CsAs2O3Br exhibited an extraordinary second‐harmonic generation (SHG) response, 20.5 times stronger than KH2PO4 (KDP), while CsAs4O6Br demonstrated exceptional birefringence (0.26 at 546 nm), setting new performance benchmarks among KBBF analogs. Theoretical analyses reveal that these superior properties arise from the efficient alignment and high density of self‐polymerized functional units. This work represents a significant advancement in the design of high‐performance UV NLO materials, particularly for fourth‐harmonic generation, and paves the way for future innovations in photonic technologies, including solar‐blind UV laser systems and advanced photonic devices.

Optical Activity of Chiral Excitons.

Recent activity in the area of chiroptical phenomena has been focused on the connection between structural asymmetry, electron spin configuration and light/matter interactions in chiral semiconductors. In these systems, spin-splitting phenomena emerge due to inversion symmetry breaking and the presence of extended electronic states, yet the connection to chiroptical phenomena is lacking. Here, we develop an analytical effective mass model of chiral excitons, parameterized by density functional theory. The model accounts for parity mixing of the band edge Bloch functions resulting from polar distortions, resulting in allowed magnetic dipole transitions. Through the study of a prototypical chiral 2D hybrid perovskite semiconductor, we show that circular dichroism of the chiral exciton and its interband continuum emerges from spin-splitting via cross-coupling of Rashba-like and chiral/helical spin-texture components. To demonstrate the generality of our approach, and as a counterpoint, we apply our model to describe chiroptical properties of three-dimensionally confined excitons in perovskite nanocrystals that occur without chiral lattice distortions.

Monitoring of the Local Extracellular Environment Using Chiral Gold Nanoparticles.

In three-dimensional (3D)-printed tissue models, sensitive, noninvasive techniques are required to detect in situ changes in hydrogel structure caused by cellular remodeling. We demonstrate herein that circular dichroism (CD) spectroscopy provides a reliable method for detecting hydrogel structural variations. We probe directly the plasmonic optical activity of chiral gold nanorods (c-AuNRs) embedded within the hydrogel matrix, in response to variations in the local environment. Unlike extinction spectroscopy, we found that CD features such as zero-point crossings do not get masked by the strong scattering due to the porous hydrogel structure and are therefore sensitive to changes in the refractive index of the medium, reversible swelling and deswelling of the hydrogel, and other interactions between the hydrogel and the c-AuNR surface. By culturing metastatic breast cancer cells within the 3D hydrogel nanocomposite, we demonstrate that CD can noninvasively probe the restructuring of the hydrogel. This study highlights the potential of CD spectroscopy in combination with c-AuNRs to investigate complex changes in biological or polymeric systems.

Intrinsically chiral thermoresponsive assemblies from achiral clusters: enhanced luminescence and optical activity through tailor-made chiral additives.

Chiral metal clusters, due to their intriguing optical properties and unique resemblance in size to biomolecules, have attracted a lot of attention in recent times as potential candidates for application in bio-detection and therapy. While several strategies are reported for the synthesis of optically active clusters, a facile approach that enhances a multitude of properties has remained a challenge. Herein, we report a simple strategy wherein the use of a chiral cationic surfactant, during the synthesis of achiral clusters, leads to the fabrication of chiral assemblies possessing enhanced luminescence and optical activity. The structural resemblance of the capping ligand, mercaptoundecanoic acid (MUA) to the co-surfactant, (+/-)-N-dodecyl-N-methylephedrinium bromide (DMEB), assisted specific interactions that led to the formation of chiral assemblies exhibiting unique thermoresponsive behavior and tunable optical activity. The symmetry breaking in the aggregates driven by the electrostatic interaction between the positively charged chiral surfactant and negatively charged clusters led to enhanced luminescence through aggregation induced enhanced emission (AIEE). The work highlighting the generation and tuning of cluster chirality provides newer insights into the fundamental understanding of nanocluster optical activity thereby opening newer avenues for the development of materials for application in the field of chiral biosensing and enantioselective catalysis.

Chiral properties of zinc complexes with bi- and tridentate ligands of L- and D-amino acids

Previous research demonstrated the dependence of the optical properties of aqueous L-methionine solutions on the concentration of zinc cations. Given that this phenomenon may offer a potential method for controlling the metabolism of active pharmaceutical ingredients, this article presents a detailed study of the optical activity of zinc complexes with L- and D-amino acids (AAs). In this study, we used automated polarimetry with automatic temperature correction via a Peltier system, dynamic laser light scattering, X-ray diffraction analysis, and biotesting on a cellular biosensor. Our results showed a dramatic difference in the dependence of optical activity on pH value for the aqueous solution of a zinc-chelate compound with L-aspartate compared to the free AA. X-ray diffraction analysis of tridentate dicarboxylic AA with Zn2+ revealed the formation of a crystallized polymer compound at pH values higher than 5.6. Zn2+ affects the chirality of aqueous solutions of bidentate monocarboxylic L- and D-AA: the rotation angle of the solutions increases for D-Val and decreases for L-Val ranging from –0.2 to +0.2 degrees, respectively. For tridentate tricarboxylic L- and D-AA, the effect of zinc on the chirality of the aqueous solution is just the opposite. The cellular biosensor of Spirostomum ambiguum is not sensitive to free AA but responds significantly to zinc complexes with L- and D-Asp. We hypothesize that chelation of L- and D-AA with zinc at pH 5.5–6.0 leads to the formation of complexes with a specific optical activity, which aligns well with the theory of predetermined chirality.

Giant and flexible toroidal circular dichroism from planar chiral metasurface

Chirality, a fundamental concept describing an object cannot superpose with its mirror image, is crucial in optics and photonics and leads to various exotic phenomena, such as circular dichroism and optical activity. Recent findings reveal that besides electric and magnetic dipoles, toroidal dipoles, an elusive part of dynamic multipoles, can also significantly contribute to chirality. However, as toroidal dipoles are typically represented by solenoidal currents circulating on a three-dimensional (3D) torus, toroidal circular dichroism is usually observed in 3D intricate microstructures. Facing corresponding challenges in fabrication, integration, and application, it is generally difficult to employ toroidal circular dichroism in compact metasurfaces for flexible modulation of chiral interactions between electromagnetic waves and matter. To overcome these stringent challenges, we propose and experimentally demonstrate the giant toroidal circular dichroism in a bilayer metasurface that is comprised of only planar layers, effectively bypassing various restrictions imposed by 3D microstructures. With the introduction of a displacement, or bilayer offset, between the opposite layers, we experimentally achieve giant chiral responses with the intrinsic circular dichroism (CD) reaching 0.69 in measurements, and the CD can be quantitatively manipulated in a simple manner. The giant intrinsic chirality primarily originates from distinct excitations of in-plane toroidal dipole moments under circular polarized incidences, and the toroidal chiral response is quantitatively controlled by the bilayer offset. Therefore, our work provides a straightforward and versatile approach for the development of giant and flexible intrinsic chirality through toroidal dipoles with inherently planar layers, important for applications in communications, sensing, and chiroptical devices.

Symmetrical and asymmetrical surface structure expansions of silver nanoclusters with atomic precision.

Controlling symmetrical or asymmetrical growth has allowed a series of novel nanomaterials with prominent physicochemical properties to be produced. However, precise and continuous size growth based on a preserved template has long been a challenging pursuit, yet little has been achieved in terms of manipulation at the atomic level. Here, a correlated silver cluster series has been established, enabling atomically precise manipulation of symmetrical and asymmetrical surface structure expansions of metal nanoclusters. Specifically, the C 3-axisymmetric Ag29(BDTA)12(PPh3)4 nanocluster underwent symmetrical and asymmetrical surface structure expansions via an acid-mediated synthetic procedure, giving rise to C 3-axisymmetric Ag32(BDTA)12(PPh3)10 and C 1-axisymmetric Ag33(BDTA)12(PPh3)11, respectively. In addition, structural transformations, including structural degradation from Ag32 to Ag29 and asymmetrical structural expansion from Ag32 to Ag33, were rationalized theoretically. More importantly, the asymmetrically structured Ag33 nanoclusters followed a chiral crystallization mode, and their crystals displayed high optical activity, derived from CD and CPL characterization. This work not only provides an important model for unlocking the symmetrical/asymmetrical size growth mechanism at the atomic level but also pioneers a promising approach to activate the optical activity of cluster-based nanomaterials.

Structural modification of hydroxyborates by adjusting the number of shared oxygen atoms and hydroxyl groups for further performance enhancement.

In recent years, hydroxyborates with excellent properties have attracted much attention. Through dedicated efforts, three new hydroxyborates-K2B5O8(OH), CsB5O6(OH)4, and CsB5O7(OH)2-have been successfully synthesized in a closed system. The ultraviolet (UV) cut-off edges of both K2B5O8(OH) and CsB5O7(OH)2 are below 200 nm, indicating their potential as candidates for deep-ultraviolet (DUV) materials. Furthermore, K2B5O8(OH) exhibits nonlinear optical (NLO) activity and demonstrates significant second harmonic generation (SHG) effects, approximately 2 × KH2PO4 (KDP). Interestingly, although all three compounds are alkali metal borates containing five boron atoms, the calculated birefringence is 0.025 at 1064 nm for K2B5O8(OH), whereas it is 0.067 and 0.070 at 1064 nm for CsB5O6(OH)4 and CsB5O7(OH)2, respectively, which are about three times that of K2B5O8(OH). The reason for the nearly threefold difference in birefringence is analyzed from the view of the structure-property relationship. Furthermore, the effect of the number of hydroxyl groups and shared oxygen atoms on the structural dimensions, birefringence, and band gaps in all alkali and alkaline-earth metal hydroxyborates with five boron atoms has been studied and analyzed. A solid foundation for the use of hydroxyl groups to tune and design structures has been provided.

Synthesis of P‐Doped g‐C3N4/Cu2O Nanocomposite and Investigation of Its Photocatalytic Characteristics in Reduction of Nitroaromatic Compounds to Corresponding Amines Under Visible Light

ABSTRACTIn this research, as a new heterogenous nanocomposite, P‐doped g‐C3N4/Cu2O was successfully synthesized by simultaneous reduction of copper salts and the resultant precipitation. The phosphor was doped onto the graphitic carbon nitrite by the calcination method. The various spectroscopic and imaging methods (XPS, X‐ray diffraction [XRD], FTIR, Pl, BET, DRS, Map Scanning, EDS (EDAX), TEM, FESEM, and EIS) were devised to characterize the structural properties, morphology, and optical and photocatalytic activities of the synthesized nanocomposite. The synthesized nanocomposite was then used as photocatalysts in the reduction of nitroaromatic compounds to the corresponding amino aromatic species, with the results being highly promising. Indeed, the conversion of nitrobenzene to aniline was 100% accomplished within 30 min. In these reactions, hydrazine compounds were used as hydrogen suppliers. The proposed photocatalyst exhibits great recyclability and reusability so that no significant change in the catalytic activity of the nanocomposite and the resultant conversion efficiency was observed after six rounds of reuse.