Octahedral Configuration Research Articles

Dyeing ability of C. longa L. and T. stans (L.) Juss. Ex Kunth on unmordanted and mordanted silk and cotton fabrics

The work was on the extraction of both the C. longa rhizomes and the petals of T. stans using four different solvents (ethanol, ethyl acetate, water, and n-hexane). The dyeing potential of the C. longa and T. stans extracts was evaluated on cotton and silk fabrics without or with mordants using potash alum, phosphomolybdic acid, iron (II) sulphate, and tartaric acid at varied temperatures and tested for colour fastness properties (wash and light fastness). The pH and absorbance of the dye bath before and after dyeing were studied. However, cotton, which is cellulosic, was better dyed than silk, which is proteinous, which showed a better choice for fabrics dyeing at 80 °C; hence, it had a good colour efficiency. Iron (II) sulphate exhibited complexes in the octahedral configuration of the coordination six with CH2O- of cotton and NH3+ and COO- of silk fabric. In addition, it was also observed that the higher the dyeing temperature, the greater the dyeing intensity. The spectroscopic characterization of the extracts was determined with the help of UV-Vis and FTIR. The UV-Vis and FTIR spectral analyses revealed the chromophore, auxochrome groups, and functional groups, respectively, within the extracts. Curcumin and rutin were identified as being responsible for the dyeing of the fabric.

The 4-Octahedra model

This work comprises a generalization of a simple geometric model originally developed to describe coupled rotations of corner-sharing octahedra in the surface layer of Sr2RuO4 under uniaxial compression. The main objective of the model is to establish a link between the experimental global strain configuration and the possible microscopic mechanisms and compatible geometries by which the octahedra accommodate the applied strain. In achieving this, a useful and intuitive parametrization of four-site two-dimensional systems of corner-sharing octahedra has been established, which can be readily extended to three dimensions and N>4 inequivalent sites or directly employed to analyze the octahedral configuration of many perovskites, transition metal oxides (TMOs), and layered compounds.

Structural Rigidification Strategy Based on Self-Assembly Enabled Reversible Excited-State Conversion of Iridium(III) Complexes for Multiple-Stimulus-Responsive Data Encryption.

Stimulus-responsive chromic materials exhibit color-switching properties under specific external stimuli and have been widely used in various fields. Transition-metal complexes show great potential applications as promising candidates for stimulus-responsive chromic materials, as their excited states not only depend on the chemical composition but are also affected by the intermolecular stacking modes. Owing to the intrinsic difficulty in the ordered stacking of the octahedral configuration, changing the stacking modes of iridium(III) complexes for multiple-stimulus responsiveness remains a significant challenge. In this work, we propose a structural rigidification strategy based on self-assembly to reversibly regulate the excited states of iridium(III) complexes, therefore achieving color switch under different stimulus conditions. We prepare cationic iridium(III) complexes by using tetrakis(perfluorophenyl)-borate ([B(PhF5)4]-) as the counterion, whose matching tetrahedral configuration and electron-deficient aromaticity enables polar-π interaction with the octahedral iridium(III) cations, inducing self-assembly to form structural rigidification. The structural rigidity restricts the large conformational changes of the metal-to-ligand charge transfer (3MLCT) excited state, and facilitates the conversion from the 3MLCT to the ligand-center (3LC) excited state in aggregated states. The excited-state conversion results in a 54 nm blue shift (from yellow to sky blue) in the photoluminescence spectra. As a result, we report a series of cationic iridium(III) complexes with different responses to low temperature, vapor fuming, and mechanical force, therefore achieving multiple-stimulus-responsive data encryption. Our work provides a novel strategy to achieve ordered stacking of octahedral complexes, shows a deeper understanding of the photophysical processes of transition-metal complexes, and offers a new perspective to develop multiple-stimulus-responsive chromic materials.

Designing of some VO(II), Co(II) and Hg(II) Schiff base complexes: Synthesis, structure elucidation, anticancer and biopesticidal activities, DFT and docking approaches

New VO(II), Co(II) and Hg(II) chelates of bi- or tetradentate isatin based ligand i.e.:-2-(((E)-2-oxo-1,4-dihydrocyclohepta [b]pyrrol-3(2H)-ylidene)amino)-N-(8-((1-(2-((E)-2-oxoindolin-3-phenyl)vinyl) amino) naphthalen-1-yl) benzamide (H2L) were synthesized and well characterized. The reaction between N,N′-(naphthalene-1,8-diyl)bis(2-aminobenzamide) and di-oxazine-2,4 dione (isatin) yielded the Schiff base (H2L). The compounds have been identified by different physicochemical and spectroscopic approaches and DFT as well. From all measurements square pyramidal, distorted octahedral or square planar configurations have been suggested for the chelates 1, 2 and 3, respectively. The Coats-Redfern equations were used to calculate and define the dynamics properties of decomposition stages from TGA (Ea, A, ΔH*, ΔS*, and ΔG*). The in vitro anticancer property of the obtained compounds towards human hepato (HepG2) and human breast (MCF-7) carcinoma cell lines has been screened. Also, the biopesticidal effect of these compounds against spodoptera littoralis has been examined. Data showed that, the tested [Hg(H2L)(L)] complex (3) possesses the most anticancer efficacy against both HepG2 and MCF-7 cells, with half inhibitory concentration (IC50) = 5.78 ± 0.029, 11.24 ± 0.58 μg/mL, respectively also, this complex considered as good an insecticide with the concentration lethal to 50 percent of test organisms (LC50) = 27585.45 ppm after 72 h. The insecticide and tumor inhibition properties were compared with the theoretical molecular docking findings with the specification of the active species in the designated proteins.

MB38(M=Be and Zn): A Quasi-Planar Structure Rather Than a Core-Shell Octahedral Borospherene Structure.

In a recent paper (ChemPhysChem, 2023, 24, e202200947), based on the results computed using DFT method, the perfect core-shell octahedral configuration Be@B38 and Zn@B38 was reported to be the global minima of the MB38(M=Be and Zn) clusters. However, this paper presents the lower energy structures of MB38(M=Be and Zn) clusters as a quasi-planar configuration, the Be atom is found to reside on the convex surface of the quasi-planar B38 isomer, while the Zn atom tends to be attached to the top three B atoms of the quasi-planar B38 isomer. Our results show that quasi-planar MB38(M=Be and Zn) at DFT method have lower energy than core-shell octahedral configuration M@B38(M=Be and Zn). Natural atomic charges, valence electron density, electron localization function (ELF) analyses identify the MB38(M=Be and Zn) to be charge transfer complexes (Be2+B38 2-and Zn1+B38 1-) and suggest primarily the electrostatic interactions between doped atom and B38 fragment. The photoelectron spectra of the corresponding anionic structures were simulated, providing theoretical basis for future structural identification.

Homoleptic Co(II) and Ni(II) complexes with promising anticancer and antimicrobial activities; Synthesis, X-ray structure, and DFT studies

The antimicrobial and anticancer potentials of the newly synthesized homoleptic [M(BPPT)2](ClO4)2 complexes, where M = Co or Ni, were reported. Their molecular structure aspects were investigated with the aid of elemental analysis, FTIR spectra, and X-ray crystallography. The s-triazine functional ligand (BPPT) worked as a tridentate N-chelate. With two BPPT molecules in the coordination sphere, the Co(II) and Ni(II) are hexa-coordinated with distorted octahedral configuration. The important supramolecular structural aspects were investigated using Hirshfeld topology analysis. The red spots in the dnorm map are related to the short O···H, N···H, C···H, and C···O contacts. 1 and 2 have promising antibacterial and antifungal activities against P.vulgaris (MIC = 2.5 μg/mL) and A. fumigatus (2.5 μg/mL), respectively exceeding the medications gentamycin (MIC= 5.0 μg/mL) and ketoconazole (5 μg/mL) as positive controls, respectively. In addition, 1 is better anticancer agent against HCT-116 (IC50 = 2.44±0.32 µg/mL) and A-549 (3.88±0.38 µg/mL) cell lines compared to the Ni(II) analogue (3.54±0.39 and 6.37±0.54 µg/mL, respectively). Their cytotoxic activity exceeded the efficiency of cis-platin versus both carcinoma cells (HCT-116; 8.4 ± 0.8 and A-549; 19.3 ± 0.8 µg/mL). The selectivity indices of 1 and 2 are exceeding unity indicating their availability for use as anticancer therapeutic agents.

A novel chemical probe based on the salamo-Co(II) complex for the highly selective fluorescence detection of tyrosine

A new and rare Salamo-Co(II) complex probe L-Co2+ was designed and synthesised. The structure of the [Co3(L)2(μ-OAc)2(MeOH)2]⋅2H2O complex was obtained by X-ray diffraction experiments. Three Co(II) atoms are in a line in the complex, and all Co(II) atoms form a 6-coordinated octahedral configuration. The probe L-Co2+ selectively recognises tyrosine in DMF/H2O (8:2, v/v). Upon addition of tyrosine, the fluorescence intensity of L-Co2+ was enhanced in a short time. The probe showed high selectivity and sensitivity for tyrosine, detection limit is 4.27 × 10−8 M. The recognition mechanism of probe L-Co2+ for Tyr was inferred by FT-IR spectra, UV spectroscopy, ESI mass spectra and DFT calculations. Finally, due to the simplicity and specificity of the identification process, the probe was also subjected to a test paper experiment and a milk assay.

Design, Characterization, and DFT exploration of new mononuclear Fe(III) and Co(II) complexes based on Isatin-hydrazone derivative: Anti-inflammatory profiling and molecular docking insights

This research focuses on the synthesis and detailed analysis of novel compounds encompassing Fe(III) (C1) and Co(II) (C2) ions, featuring 4-(2-oxo-1,2-dihydro-3H-indol-3-ylidene)hydrazono]methylphenyl 4-methylbenzenesulfonate ligand. The structural elucidation of these freshly prepared compounds was meticulously pursued employing a battery of spectroscopic techniques including NMR, UV–vis, IR, mass spectroscopy, magnetic susceptibility, conductivity, and thermal analysis (TG, DTA). Furthermore, the determination of complex stoichiometry and identification of their octahedral structural configuration were facilitated through the application of Job's techniques and molar ratio analysis. Complementing the experimental analyses, computational investigations via Density Functional Theory (DFT) were conducted to garner deeper insights into the structural, orbital, and electronic attributes of the compounds. Moreover, the anti-inflammatory properties of these synthetic compounds were scrutinized through in vitro assays, notably highlighting the superior efficacy of the C1 complex among the examined compounds. To validate their therapeutic potential, a comparative assessment was made against established anti-inflammatory agents. The hierarchy of anti-inflammatory activity among the metal complexes is established as follows: C1 > C2 > L, with the C1 exhibiting the highest potency. Additionally, a molecular docking study was executed to elucidate the compounds' interaction with the cyclooxygenase-2 (COX-2) enzyme (PDB ID: 5IKT), further corroborating their potential pharmacological relevance.

650 ps SET speed in Ge2Sb2Te5 phase change memory induced by TiO2 dielectric crystal plane

AbstractCrystallization speed of phase change material is one of the main obstacles for the application of phase change memory (PCM) as storage class memory in computing systems, which requires the combination of nonvolatility with ultra‐fast operation speed in nanoseconds. Here, we propose a novel approach to speed up crystallization process of the only commercial phase change chalcogenide Ge2Sb2Te5 (GST). By employing TiO2 as the dielectric layer in phase change device, operation speed of 650 ps has been achieved, which is the fastest among existing representative PCM, and is comparable to the programing speed of commercial dynamic random access memory (DRAM). Because of its octahedral atomic configuration, TiO2 can provide nucleation interfaces for GST, thus facilitating the crystal growth at the determinate interface area. Ti–O–Ti–O four‐fold rings on the (110) plane of tetragonal TiO2 is critical for the fast‐atomic rearrangement in the amorphous matrix of GST that enables ultra‐fast operation speed. The significant improvement of operation speed in PCM through incorporating standard dielectric material TiO2 in DRAM paves the way for the application of phase change memory in high performance cache‐type data storage.image

Molecular recognition on the surface of concentrated hydrochloric acid: Hydration configuration-driven preferential recognition of Rh (III) anions with inner-coordinated water molecules

Comprehension of selective recognition of anions is confined to a phenomenological list of solvents, hardly surpassing Pedersen’s empirical observations of cationic-crown ether binding. In this work, a novel strategy employing thin-layer oil membrane extraction (TOMX) on the surface of concentrated hydrochloric acid is proposed for controllable recognition and separation of anions with different hydration configurations. Four typical chloric-complexing anions, RhCl63−, PdCl42−, PtCl62− and FeCl4−, usually coexisting in the concentrated hydrochloric acid leaching solutions of precious metal concentrates were focused. A surprising phenomenon was noticed that the octahedral RhCl5(H2O)2− anions with inner-coordinated water molecules were preferentially recognized by 18C6 macrocyclic molecule. However, the planar quadrilateral Pd (II) chloric-complexing anions with a hydration configuration via water molecules attacking the central Pd (II) atoms along the Z-axis direction can be separated subsequently. The Pt (IV) and Fe (III) chloric-complexing anions respectively with an octahedral and tetrahedral outer-coordinated hydration shell configuration were the last to be recognized. Such an order in extracting Rh (III) > Pd (II) > Pt (IV) > Fe (III) anions depends on their hydration capacity and the preferential affinity towards the interface, which is almost impossible during the conventional stirring and oil droplet dispersed extraction. Because of a lower concentration of dissociated hydrogen ions on the surface of concentrated hydrochloric acid compared to its bulk concentrations, the hydration of those chloric-complexing anions was enhanced. The Rh (III) anions with inner-coordinated water molecules exhibit a higher interfacial affinity than other anions. The water molecules entering the inner coordination layer of Rh (III) chloric-complexing anions, cooperating with its outer-coordinated hydration shell, act as a hydrogen bond “water bridge” to interact with 18C6 molecules, which makes it easier to feel the influence from the aqueous laminar shear flow under the thin-layer oil membrane, thereby driving the preferential recognition of easily hydrated Rh (III) anions at the interface. The controllable “water bridge” interactions driven by shear flow can be activated or deactivated on the surface of concentrated hydrochloric acid by adjusting the shear flow rate. This work lays a foundation for the future development of a controllable flexible molecular recognition technology at liquid–liquid interfaces.

Disentangling the effects of structure and lone-pair electrons in the lattice dynamics of halide perovskites

Halide perovskites show great optoelectronic performance, but their favorable properties are paired with unusually strong anharmonicity. It was proposed that this combination derives from the ns2 electron configuration of octahedral cations and associated pseudo-Jahn–Teller effect. We show that such cations are not a prerequisite for the strong anharmonicity and low-energy lattice dynamics encountered in these materials. We combine X-ray diffraction, infrared and Raman spectroscopies, and molecular dynamics to contrast the lattice dynamics of CsSrBr3 with those of CsPbBr3, two compounds that are structurally similar but with the former lacking ns2 cations with the propensity to form electron lone pairs. We exploit low-frequency diffusive Raman scattering, nominally symmetry-forbidden in the cubic phase, as a fingerprint of anharmonicity and reveal that low-frequency tilting occurs irrespective of octahedral cation electron configuration. This highlights the role of structure in perovskite lattice dynamics, providing design rules for the emerging class of soft perovskite semiconductors.

Sulfanilamide and 2‐hydroxy acetophenone driven Schiff base metal complex synthesizing, identification, and promising bioactivity

It has been possible to create complexes of metals from the Schiff base ((E)‐4‐(2‐hydroxy‐1‐phenylethylideneamino) benzenesulfonamide) (Sn.HA), which is generated from sulfanilamide and 2‐hydroxy acetophenone. These substances have been identified using various physicochemical methods, featuring mass spectral analysis, melting point, (inductively coupled plasma mass spectrometry [ICP‐MS]), Proton nuclear magnetic resonance (1H NMR), Fourier transform infrared (FTIR) spectroscopy, ultraviolet (UV) spectroscopy, elemental analysis, conductance measurements, electron spin resonance (ESR), and magnetic susceptibility. Most complexes are non‐electrolytes, according to the determined molar conductance values. Spectroscopic analyses indicate coordination of the majority of complexes by 2 C=N groups and 2 (OH) phenolic groups of ligand in a 2 L:1 M molar ratio in a consistent octahedral configuration [L2‐M‐(H2O)2], (L) Schiff base ligand (Sn.HA) and (M) metal, bacteria Gram‐negative (Pseudomonas aeruginosa and Escherichia coli), bacteria Gram‐positive (Streptococcus pneumonia and Bacillus subtilis), and antifungal (Candida albicans and Aspergillus fumigatus) have all been tested on complexes to check the activity of antibacterial and antifungal, with the metal complexes showing promising activity, where the unbound ligand is less active than the metal complexes.

Perovskitizer Tuning Pb2+ 6s2 Lone Pair Effects in Hybrid Perovskite Halide Enables Multiaxial Self‐Powered X‐Ray Detection

AbstractThe stereochemical expression of the ns2 lone pair significantly impacts symmetry breaking and corresponding photoelectric properties. However, hindered by the symmetric octahedral configuration, the Pb2+ 6s2 lone pair in the well‐conductive lead halide hybrid perovskites (LHHP) are normally stereo‐inactive, new approaches to activate the 6s2 lone pair are still greatly desired. Herein, by exploiting a perovskitizer tuning Pb2+ lone pair method, the study successfully obtains a stereo‐active 6s2 in the polar perovskite PA2MHy2Pb3Br10 (PMPB, PA = n‐propylamine, MHy = methylhydrazine), and unprecedentedly performs a multiaxial self‐powered X‐ray detection. In detail, the stereo‐active 6s2 lone pair is caused by the coordination bond between the perovskitizer MHy and Pb atom. Emphatically, the N‐Pb bond induces a large angular distortion parameter (≈45 times larger than other LHHP) and the lowest‐symmetric space group (P1) crystallization. Therefore, PMPB natively contains multiaxial polarization, which acts as the driving force to separate and transport the X‐ray‐generated carriers, thus enabling multiaxial self‐powered X‐ray detection with a low detection limit (129 nGy s−1). This work reveals the relationship between stereo‐active lone pair and polarization and sheds light on future X‐ray detection.

Pressure Induces Six-fold Coordination for the Lighter Pnictides Phosphorus and Arsenic Triiodide.

In this study, we employ an evolutionary algorithm in conjunction with first-principles density functional theory (DFT) calculations to comprehensively investigate the structural transitions, electronic properties, and chemical bonding behaviors of XI3 compounds, where X denotes phosphorus (P) and arsenic (As), across a range of elevated pressures. Our computational analyses reveal a distinctive phenomenon occurring under compression, wherein the initially trigonal structures of PI3 (P 63) and AsI3 (R-3) undergo an intriguing transformation, leading to the emergence of six-coordinated monoclinic phases (C2/m) at 6 GPa and 2 GPa for PI3 and AsI3, respectively. These high-pressure phases exhibit their stability up to 10 GPa for PI3 and 12 GPa for AsI3. Notably, the resulting structures at elevated pressures bear striking resemblance to the widely recognized six-coordinated octahedral BiI3 crystal configuration observed at ambient conditions. Our investigation further underscores the pivotal role of pressure-induced reactivity of the lone-pair electrons in PI3 and AsI3, facilitating their enhanced stereochemical reactivity and thereby enabling higher six-fold coordination. Complementary analyses employing electron localization function (ELF) and density of states (DOS) effectively delineate the progression towards augmented coordination in PI3 and AsI3 with increasing pressure. While the phenomenon of heightened coordination is conventionally associated with heavier pnictide iodides such as SbI3 and BiI3 under ambient conditions due to heightened ionic character and relativistic effects in bismuth (Bi) and antimony (Sb), our findings accentuate that analogous structural transformations can also be induced in lighter elements like phosphorus (P) and arsenic (As) under the influence of pressure.

Comprehensive insights of a Salamo-like Oligo(N,O-donor) ligand and its self-assembled di-nuclear Mn(III) and tetra-nuclear Cd(II) complexes

The self-assembled di-nuclear Mn(III) & tetra-nuclear Cd(II) salamo-like oligo(N,O-donor) complexes, [Mn2(L)2(CH3OH)2]·4CH3OH (1) and [Cd4(L)2(η-OAc)2(CH3OH)2] (2) have been constructed successfully applying the measure of solvent evaporation and characterized structurally by X-ray diffraction analyses of single crystal, IR & UV visible analyses. The single crystals of the salamo-like oligo(N,O-donor) compound H3L have been obtained by wet-chemical technique, its established structure is H3L∙CH3OH. The structure of complex 1 is centrally symmetrical, and both Mn(III) atoms are hexa-coordination and have slightly distorted octahedral geometries. There are two sets of intermolecular H-bonding interactions which are connected with adjacent units of the Mn(III) complexes and form a two-dimensional network structure. For the complex 2, all of the Cd(II) atoms are also hexa-coordination and possess slightly twisted octahedral configurations. And five groups of intermolecular H-bonding interactions form a honeycomb shaped three-dimensional supramolecular structure. Additionally, the intermolecular interactions of H3L, complexes 1 and 2 have been quantified by Hirshfeld surface analysis for further study. Fluorescence emission spectra of H3L, complexes 1 and 2 were also investigated.

Probing the structural and optical properties of Eu-doped LiAl5O8 using X-ray absorption and hard X-ray excited optical luminescence

X-ray absorption and hard X-ray excited optical luminescence were used to probe the structural and optical properties of LiAl5O8 doped with different Eu concentrations produced by the modified sol-gel method. X-ray diffraction studies revealed that all samples produced have a cubic spinel unit cell of LiAl5O8 and that some impurities of the EuAlO3 phase were observed at concentration limits of 4 and 5 %. Based on the XAS results, they show the stabilization of europium in both the trivalent and bivalent states and reveal that Eu3+ ion can stabilize both in distorted octahedral configurations (non-centrosymmetric) and in the form of pentagonal bipyramid sites. The XEOL spectra were excited at Eu LIII-edge is composed of typical emission peaks attributed to the emission of Eu3+ ions and contaminating ions (Cr3+ and Fe3+). An XEOL luminescence mechanism was also discussed based on the XEOL emission spectra.

Synthesis and characterization of CuAl2O4 nanoparticles: Application for the removal of Eriochrome Black T under solar light irradiation

This work focuses on the use of the spinel CuAl2O4 as photocatalyst for the degradation of Eriochrome Black T (EBT), a potentially hazardous dye. CuAl2O4 is synthetized by co-precipitation and studied by physic-chemical and electrochemical properties. X-ray diffraction revealed the formation of a single phase with cubic symmetry with a homogeneous morphology. X-ray Photoelectron Spectroscopy (XPS) and FTIR spectroscopy provide a better understanding of the chemical composition and surface structure of CuAl2O4. Diffuse reflectance (DR) gave a band gap of 1.94 eV, attributed to Al3+ in octahedral configuration. The BET analysis led to a specific surface area of 37 m2/g with the availability of an appreciable surface for photochemical reactions. Chrono-amperometry indicated n-type conductivity of CuAl2O4, with electrons as dominant charges and an activation energy (Ea) of 0.17 eV. A flat band potential of 0.26 VSCE (Volt vs. Saturated Calomel Electrode) was calculated from the interfacial capacitance in Na2SO4 solution. The photoactivity of EBT degradation was assessed by using chemical oxygen demand (COD). A quasi-complete degradation of EBT was observed within 180 min under sunlight. The mineralization was carried out with an initial EBT concentration of 10 mg/L, a dose of 1 g/L at pH ∼ 8, similar to that of an aquatic environment. These experimental conditions are important to assess the applicability of this method in a real environment.

Structurally driven ferromagnetism in CaRuO3/Sr2RuO4 superlattices

Ruthenate thin films with a strong coupling between O 2p and Ru 4d are suitable platform for exploring emergent properties by tuning crystal structure and stacking order. The novel structured [(CaRuO3)1|(Sr2RuO4)m] superlattices (SLs) consisting of CaRuO3 and Sr2RuO4 layers were investigated to reveal the correlation between crystal structure and physical properties. All SLs with intrinsic crystal symmetry of Sr2RuO4 layer showed paramagnetic properties. Based on the structural modeling of [1|0.5] SL, the double perovskite structure consisting of Ca–O, RuO2, and Sr–O layers was confirmed. In particular, [1|0.5] SL showed ferromagnetism below at 44.5 K exhibiting MS value of 1.59 μB/Ru at 5 K. We verified that emergent ferromagnetism can be generated from strengthening of p–d hybridization, which originated from the newly established structure with the octahedral configuration of a+a+c–.

Two-dimensional Strontium Tantalate: 2D-Sr[formula omitted]TaO[formula omitted

We propose and characterize a novel 2D material with a perovskite structure, Sr2TaO4 monolayer. Using a first principles approach, we study the stability, elastic and electronic properties of the 2D-Sr2TaO4 system. In this metallic monolayer system, the tantalum atom is surrounded by six oxygen atoms in an octahedral configuration. The rotation of the octahedra structures yields antiferrodistortive distortions favoring a phase transition. We have demonstrated the stability of this perovskite-like monolayer using phonons, molecular dynamics, and elasticity criteria.

Three-Dimensional Au Octahedral Nanoheptamers: Single-Particle and Bulk Near-Field Focusing for Surface-Enhanced Raman Scattering.

Herein, we present a synthetic approach to fabricate Au nanoheptamers composed of six individual Au nanospheres interconnected through thin metal bridges arranged in an octahedral configuration. The resulting structures envelop central Au nanospheres, producing Au nanosphere heptamers with an open architectural arrangement. Importantly, the initial Pt coating of the Au nanospheres is a crucial step for protecting the inner Au nanospheres during multiple reactions. As-synthesized Au nanoheptamers exhibit multiple hot spots formed by nanogaps between nanospheres, resulting in strong electromagnetic near-fields. Additionally, we conducted surface-enhanced Raman-scattering-based detection of a chemical warfare agent simulant in the gas phase and achieved a limit of detection of 100 ppb, which is 3 orders lower than that achieved using Au nanospheres and Au nanohexamers. This pseudocore-shell nanostructure represents a significant advancement in the realm of complex nanoparticle synthesis, moving the field one step closer to sophisticated nanoparticle engineering.