Structural Characterization Research Articles

Solid-State Nuclear Magnetic Resonance Spectroscopy for Surface Characterization of Metal Oxide Nanoparticles: State of the Art and Perspectives.

Metal oxide materials have found wide applications across diverse fields; in most cases, their functionalities are dictated by their surface structures and properties. A comprehensive understanding of the intricate surface features is critical for their further design, optimization, and applications, necessitating multi-faceted characterizations. Recent advances in solid-state nuclear magnetic resonance (ssNMR) spectroscopy have significantly extended its applications in the detailed analysis of multiple metal oxide nanoparticles, offering unparalleled atomic-level information on the surface structures, properties, and chemistries. Herein, we present an overview of the current state of the art from an NMR perspective. We begin with a brief introduction to contemporary ssNMR methodologies. Subsequently, we introduce and provide critical reviews on the applications of different ssNMR techniques in the detailed characterizations of the surface local structures, disorders, defects, active sites, and acidity on metal oxide nanoparticles, as well as the revelation of mechanisms behind some intriguing chemistries that occur on the surfaces, referencing representative recent studies. Finally, we address the challenges beyond the current status and provide perspectives on the future development and application of advanced ssNMR methodologies in this emerging field.

Insect-based chitin and chitosan from whole body sources and rearing by-products: extraction, physicochemical, structural and bioactivity characterisation

Abstract Fractionation of edible insects and their rearing by-products can lead to expanded industrial applications and extraction of value-added products. The main goal of this study was to extract chitin and synthesise chitosan from three different insect sources – Tenebrio molitor larvae, adult Acheta domesticus and A. domesticus rearing by-products (legs and wings). Furthermore, the physicochemical, structural, and bioactive properties of insect-derived chitin and chitosan were characterised and compared to commercial crustacean-based samples. Chitin was isolated from defatted sources through chemical hydrolysis followed by decolourisation and was deacetylated with a strong alkaline solution to synthesise chitosan. Notably, A. domesticus rearing by-products yielded the highest chitin and chitosan content. Chitin and chitosan derived from insects exhibited physicochemical and structural characteristics consistent with the α-polymorphic form, similar to the commercial samples. Differences were found in surface morphology, with insect-derived samples presenting large and irregular flakes and porosity, while the crustacean-derived samples presented irregularly arranged fibres and a more regular and smoother surface. As for antioxidant activity, although all chitosan samples demonstrated poor DPPH radical scavenging activity, this study showed for the first time that insect-derived chitosan presents lipid peroxidation inhibition ability. All chitosan samples presented antimicrobial activity against different pathogenic bacteria, with K. pneumoniae being the most susceptible strain. Nevertheless, there is potential for enhancement of the biological properties through modifications on the molecular weight and deacetylation degree. This research introduces the potential of cricket-rearing by-products as sustainable sources of chitosan with functional bioactive properties.

Intramolecular Agostic Interactions and Dynamics of a Methyl Group at a Preorganized Dinickel(II) Site.

Alkyl nickel intermediates relevant to catalytic processes often feature agostic stabilization, but relatively little is known about the situation in oligonickel systems. The dinickel(I) complex K[LNiI2], which is based on a compartmental pyrazolato-bridged ligand L3- with two β-diketiminato chelate arms, or its masked version, the dihydride complex [KL(NiII-H)2] that readily releases H2, oxidatively add methyl tosylate to give diamagnetic [LNiII2(CH3)] (1) with d(Ni···Ni) ≈ 3.7 Å. Structural characterization shows that the methyl group in 1 is bound to one NiII and exhibits an intramolecular agostic interaction with the more distant NiII. This is supported spectroscopically (viz., a ν(C-H) stretch at 2658 cm-1 and lowered 1JC-H of 114 Hz) and by DFT calculations, including topological analysis of the computed electron density for 1. NMR spectroscopy reveals very fast hopping of the CH3 group between the two NiII ions, which according to DFT has a minute barrier of 4 kcal mol-1 and proceeds via a planar CH3 moiety in the transition state (Walden-like inversion). The alkylidene group in K[LNi2(μ-CHSi(Me3)3)], obtained from the reaction of [KL(Ni-H)2] with N2CHSiMe3, is symmetrically bridging. This work provides new insight into the stabilization and dynamics of alkyl ligands at dinickel sites with a constrained metal···metal distance.

Advanced chemical and structural characterization of RAM memory waste: an approach towards recyclability and environmental safety

Este estudio aborda la caracterización química y estructural de polvos derivados de la molienda de desechos de memorias RAM, enfocándose en la identificación de su composición química (elementos metálicos y no metálicos). Mediante el uso de técnicas avanzadas como espectroscopía de energía dispersiva de rayos X (EDS) y difracción de rayos X, se detectó una variedad de elementos y compuestos tanto metálicos (Cu, Si, Sn) como no metálicos (fibra de vidrio) esenciales en la manufactura de placas de circuitos electrónicos. Además, se evaluaron las concentraciones de elementos ambientalmente peligrosos (Pb, As, Cd) y bifenilos policlorados, encontrando que, en su mayoría, están dentro de los niveles autorizados por las regulaciones internacionales, lo que sugiere que estos desechos son relativamente seguros desde una perspectiva ecológica. No obstante, se observaron niveles de plomo superiores a los límites establecidos, lo que indica la necesidad de un manejo cuidadoso. Este trabajo contribuye al conocimiento sobre la composición de los desechos electrónicos y subraya la importancia de desarrollar procesos de reciclaje efectivos y seguros para mitigar los posibles riesgos ambientales.

Solvent-Dependent Reactivity of Fe(CO)5 under Superacidic and Oxidative Conditions.

Herein, we report the solvent-dependent reactivity of Fe(CO)5 toward AsF5 in either anhydrous HF or liquid SO2. The reaction of Fe(CO)5 with the superacid HF/AsF5 leads to the protonation of the iron center and allows for the first-time structural characterization of [FeH(CO)5]+ in the solid state, representing one of the most acidic transition metal hydride complexes to ever be isolated and structurally characterized. In the aprotic but oxidation-stable solvent SO2, Fe(CO)5 is oxidized and dimerized to [Fe2(CO)10]2+, which is isoelectronic with well-known Mn2(CO)10. [Fe2(CO)10]2+ is the first structurally characterized example of a homoleptic dinuclear transition metal carbonyl cation. Together with Fe(CO)5 and [Fe(CO)5]+•, it is a rare example of an iron-centered triad from which the neutral, the radical cationic, and the dimerized dicationic species have been structurally and spectroscopically characterized. All characterizations are well supported by quantum chemical calculations. We also make the argument that the dimerization of [Fe(CO)5]+• is largely dependent on the employed solvent.

Exploring the Potential of Oxalyldihydrazide-Derived Schiff Bases as Versatile Ligands: Synthesis, Structural Characterization, and Magnetic Properties

Schiff bases constitute a broad and well-established class of ligands widely utilized in coordination chemistry. To further enrich this family and assess the potential impact of oxalyldihydrazide-derived Schiff bases in the realms of coordination chemistry and molecular magnetism, three novel ligands have been synthesized and investigated. i.e., N′1,N′2-bis((E)-pyridin-2-ylmethylene)oxalohydrazide (H2L1), N′1-((E)-(3-methylpyridin-2-yl)methylene)-N′2-((E)-(6-methylpyridin-2-yl)methylene)oxalohydrazide (H2L2) and N′1,N′2-bis((E)-phenyl(pyridin-2-yl)methylene)oxalohydrazide (H2L3) were synthesized and then combined with various 3d metals, resulting in the formation of five new complexes with formula [Cu5(L1)2(H2O)8(MeOH)2(NO3)2](NO3)4 (1), [Mn2(HL2)2(BzO)2(MeOH)2]·2MeOH (2), [Ni(HL2)2]·2MeOH (3), [Ni4(L2)4]·4MeOH (4), [Ni8(L3)4(AcO)4(H2O)12](OAc)4 (5). These compounds were structurally and magnetically characterized, revealing the various coordination modes exhibited by the ligands and a distinct antiferromagnetic behavior. Alternating current (AC) susceptibility measurements were conducted on complex 1, showing no evidence of Single Molecule Magnet (SMM) behavior.

Evaluation of safe exposure time for two-photon microscopy imaging of acrylic-painted mock-ups

Abstract Nonlinear optical microscopies are widely used in the biological and biomedical fields, as they are non-invasive techniques that permit the safe structural and morphological characterisation of cells and tissues. They are increasingly being used in the Cultural Heritage field because of their ability to overcome some limits of the well-established optical techniques. However, since nonlinear optical microscopies use pulsed laser sources with high peak power, their application in Cultural Heritage raises concerns due to artworks' unique, priceless, and delicate nature. In this paper, we present a new method for evaluating the photo-induced damage when using a near-infrared femtosecond pulsed laser to perform two-photon excited fluorescence imaging of acrylic-painted mock-ups. In particular, we explore herein several irradiation conditions, varying the exposure time and excitation power, in order to provide useful experimental indications for safely imaging acrylic paints with two-photon microscopy.

CPconf_score: A Deep Learning Free Energy Function Trained Using Molecular Dynamics Data for Cyclic Peptides.

Accurate structural feature characterization of cyclic peptides (CPs), especially those with less than 10 residues and cis-peptide bonds, is challenging but important for the rational design of bioactive peptides. In this study, we performed high-temperature molecular dynamics (high-T MD) simulations on 250 CPs with random sequences and applied the point-adaptive k-nearest neighbors (PAk) method to estimate the free energies of millions of sampled conformations. Using this data set, we trained a SchNet-based deep learning model, termed CPconf_score, to predict the conformational free energies of CPs. We tested CPconf_score to identify near-native conformations from MD-sampled conformations of 50 CPs from the Cambridge Structural Database. Our method achieved accurate predictions for 41 out of 50 CPs with a backbone RMSD of less than 1.0 Å compared to crystal structures. In comparison, other advanced CP structure prediction tools, such as HighFold and Rosetta, successfully predicted 12 and 19 CPs, respectively.

Experimental Investigation of a C-S-H Nanocrystalline Nucleus Modified with PCE Dispersant on the Early-Age Mechanical Behavior of Oil Well Cement Paste

For the exploration and development of oil and gas reservoirs in shallow, cold regions and deep oceans, oil well cement (OWC) pastes face the challenge of slow cement hydration reactions and the low early-strength development of cement stone at low temperatures, which can cause the risk of fluid channeling and the defective isolation of the sealing section during the cementing construction process. To address the above challenges, a nanoscale hydrated calcium silicate (C-S-H) crystal nucleus, DRA-1L, was synthesized. Its application performance and action mechanism were studied. The structural characterization of DRA-1L revealed that its crystal structure resembles that of amorphous C-S-H gel, with a size distribution ranging from 20 to 200 nm. The addition of DRA-1L significantly shortens the transition time of static gel strength, preventing the channeling of OWC paste and promoting the strength development of cement stone at low temperatures. Moreover, the mechanism by which DRA-1L enhances the early strength of cement stone was studied. Results indicated that the nanoscale DRA-1L with nucleation effect reduces the barrier to C-S-H gel formation and accelerates cement hydration, which leads to the increased compactness and early strength of cement stone.

EXPLORATION OF HALLUCINOGENIC COMPOUNDS IN PEGANUM HARMALA, A POPULAR INCENSE IN FOLK CULTURE, COUPLED WITH ANATOMICAL ANALYSIS

Objective: Peganum harmala L., commonly known as "harmala," is extensively used as an herbal incense product today and is renowned for its reported calming effects on humans. This study aims to perform a structural characterization of incense, with a particular focus on its fruit and seed components, by analyzing both the combustion process and dissolving the resulting smoke in an appropriate solvent. Additionally, we aim to contribute to the literature by investigating the presence of hallucinogenic compounds in this incense. Simultaneously, anatomical features of pedicels, petals, sepals, stamens, and pistils of P. harmala were examined through manual sectioning. Material and Method: Smoke from incense was dissolved using n-hexane and dichloromethane solvents. Chemical analysis of seeds and fruits was conducted using GC-MS at the Erzurum Regional Criminal Police Laboratory Directorate. Anatomical characterization involved manual sectioning of pedicels, petals, sepals, and pistils, followed by examination under a microscope. Result and Discussion: Upon analysis of samples extracted from dichloromethane and n-hexane solvents, the presence of harmine-a compound exhibiting hallucinogenic properties-has been identified. Harmine is known to impact human perception, cognition, and emotions by influencing central nervous system. The anatomical analysis revealed the presence of glandular trichomes on the pedicel, and sepal. Chemical compounds in smoke of P. harmala seeds and fruits, including hallucinogenic compound harmine, were identified through GC-MS analysis.

Stability of Ternary Drug–Drug–Drug Coamorphous Systems Obtained Through Mechanochemistry

Background/Objectives: This study investigates the preparation of coamorphous systems composed entirely of active pharmaceutical ingredients (APIs), namely praziquantel, niclosamide, and mebendazole. The objective was to formulate and characterize binary and ternary coamorphous systems to evaluate their structural, thermal, and stability properties. Methods: Ten different mixtures (binary and ternary) were designed through a mixture design approach and prepared using a sustainable, one-step neat grinding process in a lab-scale vibrational mill. The systems were prepared reproducibly within 4 h across the entire experimental domain. Structural characterization was performed using PXRD and FTIR to confirm the absence of crystalline domains and the presence of molecular interactions. The glass transition temperature (Tg) was theoretically calculated using the Gordon–Taylor equation for three-component systems and determined experimentally via DSC. Stability studies were conducted on seven systems under different storage conditions (−30 °C, 5 °C, 25 °C, and 40 °C) for six months. Results: PXRD analysis confirmed the formation of coamorphous systems with no crystalline phases. DSC revealed a single Tg for most systems, indicating homogeneity. Stability studies demonstrated that five out of seven systems adhered to the “Tg—50 °C” stability rule, remaining physically stable over six months. Recrystallization studies indicated diverse pathways: some systems reverted to their original crystalline phases, while others formed new entities such as cocrystals. Conclusions: This study highlights the feasibility of coamorphous systems composed of multiple APIs using a simple, solvent-free grinding approach. The findings underscore the importance of molecular interactions in determining stability and recrystallization behavior, offering insights for designing robust coamorphous formulations.

A Pyrrole‐Fused Nanographene and its Edge‐Perchlorinated Derivative Featuring a Corannulene Core and Five N‐doped Heptagons

A pyrrole‐fused analogue of warped nanographene, designated as deca‐nitrogen doped 'WNG' (azaWNG), was synthesized through the annular fusion of decapyrroylcorannulene. The resulting azaWNG exhibited extremely limited solubility in common organic solvents and was characterized solely by mass spectrometry. Theoretical calculations revealed that azaWNG has a sunflower‐like molecular structure with electron‐deficient corannulene as the core and electron‐rich pyrrole as the petals, demonstrating a significantly narrower energy gap compared to all‐carbon WNG. To improve its solubility and facilitate precise structural characterization, iodine monochloride was utilized for edge‐perchlorination of azaWNG, enabling successful separation and purification of chlorinated azaWNG in solution phase. X‐ray crystallography analysis unequivocally confirmed that edge‐perchlorinated azaWNG contains 5 heptagons and 11 pentagons embedded within the warped π skeleton. Cyclic voltammetry measurements indicated that the first oxidation potential of azaWNG is –0.59 V, representing the lowest value reported for any previously studied aza‐nanographene. Consequently, azaWNG can be readily oxidized by AgPF6 or even atmospheric oxygen to yield stable oxidation states, as corroborated by UV‐visible absorption spectroscopy; this behavior is attributed to the fusion of ten pyrroles around corannulene. This work marks the first instance of nitrogen doping in WNG (C80H30), underscoring the significant modification to electronic structure induced by such doping.

Synthesis and Structural Characterization of Four Bidentate Ortho‐Hydroxy Schiff Bases and Their Copper (II) Complexes: Evaluation of Biological Activities, Antioxidant Power, and Molecular Docking Studies

ABSTRACTFour ortho‐hydroxy aromatic bidentate Schiff bases were synthesized along with the corresponding copper (II) complexes and characterized by various analytical methods. The spatial configurations of the metal complexes were suggested in light of the analytical results obtained. Antibacterial evaluations revealed that the ligands were more active than their Cu(II) complexes. The study of antifungal activity showed that the fungus Candida albicans was more inhibited by the ligands (HL3 and HL4) and their Cu(II) complexes (IZ = 25 mm). According to the evaluation of antioxidant potency by the DPPH method, only ligand HL4 demonstrated a comparatively low ability to scavenge free radicals compared to the ascorbic acid reference. Using the AutoDock 4.2 program, molecular docking investigations were conducted with the aim of predicting the structure–activity relationship for antibacterial qualities. Using the active sites of receptor proteins, the synthesized ligands were evaluated by molecular docking assays. A good correlation was found between the results of experimental antibacterial activity and the molecular docking data.

A Pyrrole-Fused Nanographene and its Edge-Perchlorinated Derivative Featuring a Corannulene Core and Five N-doped Heptagons.

A pyrrole-fused analogue of warped nanographene, designated as deca-nitrogen doped 'WNG' (azaWNG), was synthesized through the annular fusion of decapyrroylcorannulene. The resulting azaWNG exhibited extremely limited solubility in common organic solvents and was characterized solely by mass spectrometry. Theoretical calculations revealed that azaWNG has a sunflower-like molecular structure with electron-deficient corannulene as the core and electron-rich pyrrole as the petals, demonstrating a significantly narrower energy gap compared to all-carbon WNG. To improve its solubility and facilitate precise structural characterization, iodine monochloride was utilized for edge-perchlorination of azaWNG, enabling successful separation and purification of chlorinated azaWNG in solution phase. X-ray crystallography analysis unequivocally confirmed that edge-perchlorinated azaWNG contains 5 heptagons and 11 pentagons embedded within the warped π skeleton. Cyclic voltammetry measurements indicated that the first oxidation potential of azaWNG is -0.59 V, representing the lowest value reported for any previously studied aza-nanographene. Consequently, azaWNG can be readily oxidized by AgPF6 or even atmospheric oxygen to yield stable oxidation states, as corroborated by UV-visible absorption spectroscopy; this behavior is attributed to the fusion of ten pyrroles around corannulene. This work marks the first instance of nitrogen doping in WNG (C80H30), underscoring the significant modification to electronic structure induced by such doping.

Microwave-assisted extraction of dandelion root polysaccharides: Extraction process optimization, purification, structural characterization, and analysis of antioxidant activity.

This study aimed to establish a microwave-assisted method (MAE) for the efficient extraction of polysaccharides from dandelion roots. This study investigated the molecular structure and bioactivity of the polysaccharides from dandelion roots. Extraction conditions were optimized using response surface methodology (RSM). The microwave extraction conditions were set to an extraction time of 42 min, an extraction temperature of 80 °C, and a solid-liquid ratio (g/mL) of 1:33. Under the optimized conditions, the highest dandelion root polysaccharides (DRP) yield was achieved (24.85 ± 0.457 %). Water-pure DRP (DRPw) and NaCl-pure DRP (DRPs) were purified by activated carbon decolorization and DEAE fiber column chromatography. The molecular weights of DRPw and DRPs were 8653 Da and 5930 Da, respectively. The Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses confirmed the existence of α- and β-pyranose in DRPw and DRPs. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that DRPw and DRPs were semi-crystalline substances with irregular shapes and rough surfaces. Bioactivity assays revealed the good antioxidant activities of DRPw and DRPs. The present study provides useful information about DRP as natural antioxidants for the benefit of food.

Isolation and identification of two novel PDE-5 inhibitors illegally added to pressed candies

Two novel phosphodiesterase 5 (PDE-5) inhibitors were detected in pressed candy using high-performance liquid chromatography (HPLC)-diode array detection. Following extraction with acetonitrile and sonication, the compounds were isolated and purified via semi-preparative liquid chromatography. Structural characterisation was achieved through high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy. The results indicate that both compounds possess identical UV absorption spectra. The molecular formulas of compounds 1 and 2 are C23H32N4O4 and C22H30N4O4, respectively, each featuring a pyrimidinone benzene structure with a single methylene group (-CH2) variation. As studies on these illicit compounds in functional foods have not been conducted, regulatory agencies must take note and incorporate them for the assessment of illicit additives in functional and healthcare foods.

Boosting the energy storage performance of BCZT-based capacitors by constructing a Schottky contact.

Multilayer thin films composed of dielectric Ba0.7Ca0.3Zr0.2Ti0.8O3 (BCZT) and oxygen-deficient BCZT (BCZT-OD) were fabricated on (001)-oriented NSTO substrates using the pulsed laser deposition (PLD) technique. Unlike conventional approaches to energy storage capacitors, which primarily focus on compositional or structural modifications, this study explored the influence of the layer sequence and periodicity. The interface between the NSTO substrate and the BCZT-OD layer forms a Schottky barrier, resulting in electric field redistribution across the sublayers of the BCZT/BCZT-OD//(1P) thin film. This redistribution delays the breakdown of the BCZT layer, significantly enhancing the film's electric breakdown strength. Furthermore, mathematical analysis reveals that the electric field redistribution amplifies dipole polarization, with BCZT-OD-initiated multilayers exhibiting superior polarization compared to those with equivalent periodicity but different starting layers. Consequently, the BCZT/BCZT-OD//(1P) multilayer achieves an exceptional recoverable energy density (Wrec) of 150.22 J cm-3 and an energy efficiency (η) of 83.07%, surpassing typical performance benchmarks for BCZT-based thin films. These findings are corroborated by comprehensive structural characterization studies, performance evaluations, and finite element simulations, which further validate the role of the Schottky barrier in enhancing voltage endurance. Analogous to "Tian Ji's Strategy for Horse Racing", this work achieved high Wrec by sacrificing the ferroelectricity of the negative side of the P-E loop, introducing an innovative paradigm for designing and developing next-generation electronic devices.

Microstructural Analysis and Radiological Characterization of Alkali-Activated Materials Based on Aluminosilicate Waste and Metakaolin

The formation of an aluminosilicate gel structure made of alkali-activated materials (AAMs) was conducted through an alkali-activation reaction of the solid precursors (fly ash, metakaolin, and wood ash). Fly and wood ash are by-products of the burning process of coal and wood, respectively. Alkali-activated materials of aluminosilicate origin, made from the different ashes, fly and wood, are very attractive research targets and can be applied in various technological fields due to their thermal stability, resistance to thermal shock, high porosity, high sustainability, and finally, low energy loss during production. In this paper, we evaluate physico-chemical properties, microstructure, and radiological environmental impacts when wastes that contain elevated levels of naturally occurring radionuclides (NORs) such as fly ash and wood ash are made into “green cements” such as AAMs. The determination of radionuclide content was performed by means of gamma-ray spectrometry. Results showed that the AAMs have a lower value in the activity concentration of radionuclides than raw materials. The external absorbed gamma dose rate was 74.7–107.3 nGy/h, and the external radiation hazard index values were in range of 0.445–0.628 Bq/kg. The results of the activity concentration measurements for alkali-activated materials indicate the potential of their safe application in building construction. In terms of the structural characterizations, the obtained alkali-activated materials were examined using XRD, DRIFT, FESEM, and TEM analyses.

Synthesis, structural characterization, and optical properties of two Co(II)-based coordination compounds

Two new Co(II)-based coordination compounds, [Co(Hmctrz)2(H2O)2] (1) and [Co(Hdctrz)(H2O)2]n (2), were synthesized via routine or hydrothermal reactions using cobalt salts, triazole derivatives, and auxiliary reagents. Characterizations, including single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, TGA, and PXRD, confirmed their formation. UV-Vis and fluorescence studies revealed distinct optical properties, with 1 and 2 exhibiting UV absorption peaks at 353 and 370 nm, respectively, and concentration-dependent fluorescence emission, indicating potential for optoelectronic and biological imaging applications. Additionally, adsorption studies showed excellent dye removal capabilities, with 1 achieving 98% removal of methylene blue (MB) and 93% of methyl orange (MO), outperforming 2, which removed 95% of MB and 87% of MO. These results highlight the compounds’ potential in both environmental remediation and advanced material applications.

An Efficient Photocatalytic Material, rGO-TiO2, That Can Be Industrially Produced: Fabrication and Structural Characterization

An Efficient Photocatalytic Material, rGO-TiO2, That Can Be Industrially Produced: Fabrication and Structural Characterization