Spectroscopic Techniques Research Articles

Covalent Functionalisation of rGO and Nanodiamonds: Complementary Versatility and Applicability of Azomethine Ylide, Nitrile Oxide and Nitrone.

The existing synthetic protocols for the direct functionalization of carbon-based nanomaterials often entail limitations due to their harsh reaction conditions, which require the use of high temperatures for extended periods. This study aims to overcome these limitations by developing mild and efficient synthetic protocols around 1,3-dipolar cycloaddition. Beginning with the well-established azomethine ylide derivatization, we progress to the utilization of nitrile oxide, and of nitrone derivatives for the functionalization of reduced graphene oxide (rGO) as well as of nanodiamonds (NDs). This comparative work employs both classical heating and microwave activation with the aim of reducing reaction times and enhancing efficacy. Results demonstrate that nitrone can react at 60 °C and that the reaction temperature may be decreased to 30 °C with nitrile oxide. Excellent progress was made in reducing the large excess of dipoles typically required for derivatization. Nitrile oxide was proved to be the most efficient in terms of derivatization degree, while nitrone was the most versatile reagent, facilitating the decoration of the carbon nanolayer with disubstituted dihydroisoxazole. To accurately assess the degree of functionalization, the reaction products underwent characterization using various spectroscopic and analytical techniques. Additionally, an indirect evaluation of the reaction outcome was conducted through Fmoc deprotection and quantification.

Electrochemical Analysis on Corrosion of Stainless Steels in Molten Nitrate Salt

Electrochemical analysis of corrosion in molten nitrate salt of stainless steel grade SS 430, SS 2205, SS 2507 and SS 304 is directly performed to evaluate corrosion resistance. Stainless steels are exposed to molten nitrate salt at 600 °C for two hours. This is done in a furnace equipped with a working electrode terminal, reference and counter electrodes. According to this, electrochemical impedance spectroscopy and potentiodynamic polarization techniques are applied in situ to measure corrosion rates and corrosion resistance. Microstructures of stainless steel reveal the ferrite phase for SS 430, the austenite phase for SS 304 and the duplex phase for SS 2205 and SS 2507. In this study, the existence of an austenite phase promotes corrosion resistance in molten nitrate salt.

Three new xanthones and other anti-inflammatory components from the aerial parts of Hypericum beanii.

Hypericum beanii, a traditional folk medicine plant, has been employed in treating various inflammation-related diseases. In this study, three new prenylated xanthones, named beanigenin A (1), beanigenin B (2), and beanigenin C (3), along with twenty-five known compounds (4-28), were isolated from the aerial parts of H. beanii. The new xanthones were elucidated based on modern spectroscopic experiments, including nuclear magnetic resonance spectroscopy (NMR) techniques, high-resolution electrospray ionization mass spectroscopy (HR-ESI-MS), and electronic circular dichroism (ECD). All the compounds were evaluated for their anti-inflammatory effects by measuring their inhibitory effect on nitric oxide (NO) production in LPS-stimulated RAW 264.7 macrophages. Our findings showed that compounds 1-10, 12, 14, 21-23, 26, and 28 displayed significant anti-inflammatory effects, with IC50 values ranging from 0.82 to 9.71μM. The MOE software was utilized to conduct an in silico evaluation of the potential inhibitory activity of the three new xanthones against inducible NO synthase (iNOS) and cyclooxygenase 2 (COX-2) proteins. The results indicated that the three new xanthones demonstrated a high binding affinity with both iNOS and COX-2 proteins.

The Use of Nanosecond Pulsed Fibre Laser Treatment to Improve the Corrosion Resistance of 316L SS Utilised as Surgical Devices

The nanosecond pulsed fibre laser (NsPFL) treatment is extensively employed to distinguish hospital surgical instruments (micro-surgical forceps, surgical blades, orthopaedic drills, and high-precision laparoscopic tools), which are generally composed of stainless steel. Nevertheless, if the laser parameters are not properly optimised, this process may unintentionally provoke corrosion. Maintaining the structural integrity of these materials is essential for ensuring patient safety and minimising long-term costs. This work aims to optimise the laser scanning parameters for marking 316L stainless steel (316L SS), seeking to improve its corrosion resistance. The corrosion behaviour was assessed by using open circuit potential (OCP), potentiodynamic polarisation curves (PPc), and electrochemical impedance spectroscopy (EIS) techniques, conducted in 0.9% wt NaCl solution at a controlled temperature of 25 ± 1 °C. A comprehensive study employing optical profilometry has significantly enhanced our understanding of the corrosion micromechanisms of 316L SS, comparing specimens both with and without NsPFL treatment. Considering applications involving environments rich in chloride ions, the results indicated that the NsPFL-316L SS samples demonstrated markedly enhanced performance compared to the untreated base material after 48 h of immersion in 0.9% wt NaCl solution. This improvement is particularly noteworthy given the widespread utilisation of 316L SS in the manufacturing of surgical instruments, where corrosion resistance is of paramount importance.

Transcriptome-aligned metabolic profiling by SERSome reflects biological changes following mesenchymal stem cells expansion

BackgroundMesenchymal stem cells (MSCs) are widely applied in the treatment of various clinical diseases and in the field of medical aesthetics. However, MSCs exhibit greater heterogeneity limited stability, and more complex molecular and mechanistic characteristics compared to conventional drugs, making rapid and precise monitoring more challenging.MethodsSurface-enhanced Raman spectroscopy (SERS) is an ultrasensitive, tractable and low-cost fingerprinting technique capable of identifying a wide range of molecules related to biological processes. Here, we employed SERS for reproducible quantification of ultralow concentrations of molecules and utilized spectral sets, termed SERSomes, for robust and comprehensive intracellular multi-metabolite profiling.ResultsWe revealed that with increasing passage number, there is a gradual decline in cell expansion efficiency, accompanied by significant changes in intracellular amino acids, purines, and pyrimidines. By integrating these metabolic features detected by SERS with transcriptomic data, we established a correlation between SERS signals and biological changes, as well as differentially expressed genes.ConclusionIn this study, we explore the application of SERS technique to provide robust metabolic characteristics of MSCs across different passages and donors. These results demonstrate the effectiveness of SERSome in reflecting biological characteristics. Due to its sensitivity, adaptability, low cost, and feasibility for miniaturized instrumentation throughout pretreatment, measurement, and analysis, the label-free SERSome technique is suitable for monitoring MSC expansion and offers significant advantages for large-scale MSC manufacturing.

In Situ Metal Vacancy Filling in Stable Pd-Sn Intermetallic Catalyst for Enhanced CC Bond Cleavage in Ethanol Oxidation.

A common challenge in electrochemical processes is developing high performance, stable catalysts for specific chemical reactions. In this work, a Pd-Sn intermetallic compound with Pd site deficiency (Pd1.9-xSn) (x = 0.06) and trace amount of SnOx was synthesised by controlled process. Under the electrochemical conditions, the deficient Pd site is filled by metallic Sn, which generates a highly active and stable (Pd1.84Sn0.06)Sn catalyst for ethanol oxidation reaction (EOR). The crystal structure and atomic arrangements for synthesized and in situ generated compound are comprehensively characterized by various spectroscopic techniques. The in situ generated catalyst exhibits excellent performance toward EOR (anodic reaction in fuel cell), which outperforms the state-of-the-art Pd/C catalyst by three times in terms of activity. Furthermore, it is observed that the catalyst preferentially cleaves the CC bond in ethanol, which is a crucial process that enhances the efficiency of the fuel cells. The catalyst retains its superlative activity even after 1500 cycles of continuous operation. The mechanism for EOR and CC bond cleavage is evidenced by operando Infra Red spectroscopyand Differential Electrochemical Mass Spectroscopy (DEMS), and the driving force toward excellent performance has been proposed via theoreticalcalculations.

Manganese(II) Complexes with Non-Steroidal Anti-Inflammatory Drugs: Structure and Biological Activity

Nine manganese(II) complexes with a series of non-steroidal anti-inflammatory drugs (namely sodium diclofenac, diflunisal, flufenamic acid, sodium meclofenamate, mefenamic acid, and tolfenamic acid) were prepared in the presence of diverse nitrogen donors, i.e., pyridine, 1,10–phenanthroline, 2,2′–bipyridine and neocuproine, as co-ligands and were characterized with spectroscopic techniques and single-crystal X-ray crystallography. The biological profile of the resultant complexes was investigated regarding their antioxidant potency and their interaction with DNA and serum albumins. The complexes interact with calf–thymus DNA in an intercalative mode and bind tightly and reversibly to human and bovine serum albumins studied. In order to assess the antioxidant activity of the Mn(II) complexes, their ability to scavenge 2,2′–azinobis(3–ethylbenzothiazoline–6–sulfonic acid) free radicals was monitored.

Antiproliferative Activity and Molecular Docking Analyses of Sesquiterpene Lactones Obtained from Activity-Directed Isolation of Centaurea saligna (K.Koch) Wagenitzin Neoplastic Cells.

Secondary metabolites obtained from plants are among the most commonly encountered chemotherapeutics used in cancer treatment. Plants contain thousands of metabolites; therefore, it is important to reach the compound primarily responsible for activity by fractionating plant extracts through activity-guided isolation. The cytotoxic activities of C. saligna fractions, sub-fractions, and all pure compounds obtained from the plant were investigated in vitro using MCF-7 (human breast cancer), HeLa (human cervical cancer), and PC-3 (prostate cancer) cell lines. Eighteen compounds were isolated from C. saligna, comprising eight sesquiterpene lactones, three flavonoids, five lignans, and two phenolic compounds, with their structures elucidated through 1H-NMR, 13C-NMR, and HMBC spectroscopic techniques. The molecular docking scores of the pure compounds obtained from these sub-fractions were determined using both AutoDock and AutoDock Vina programs. It has been proven that the affinities of linichlorin B and aguerin B for Bcl-2 are higher than those of other compounds, considering the calculated Ki values and placement scores. Notable activities of linichlorin B, cynaropicrin, and aguerin B (with IC50 values of 13.67μg/ml, 6.79μg/ml, and 3.46μg/ml, respectively) were detected in the PC-3 cell line; aguerin B demonstrated activity most comparable to the standard anticancer agent doxorubicin. Likewise, linichlorin B, aguerin B, and cynaropicrin demonstrated notable efficacy in the HeLa and MCF-7 cell lines, as reported by the American National Cancer Institute. Aguerin B, linichlorin B, and cynaropicrin are projected to serve as promising novel chemotherapeutic agents for cancer therapy.

Bimetallic PdPt nanoparticle-incorporated PEDOT:PSS/guar gum-blended membranes for enhanced CO2 separation.

To address the escalating demand for efficient CO2 separation technologies, we introduce novel membranes utilizing natural polymer guar gum (GG), conjugate polymer (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)) PEDOT:PSS, and bimetallic PdPt nanoparticles. Bimetallic PdPt nanoparticles were synthesized using the wet chemical method and characterized using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques. The morphologies, chemical bonds, functional groups, and mechanical properties of the fabricated membranes were characterized using various techniques. Through meticulous fabrication and characterization, the binary blended membranes demonstrated enhanced homogeneity and smoothness in their structure, attributed to the interaction between the polymers, and superior CO2 permeability due to the amphiphilic nature of the PEDOT:PSS polymer. Gas separation experiments performed using H2, N2, and CO2 gases confirmed that the 20% PEDOT:PSS/GG blended membranes showed the best performance with sufficient mechanical properties. Moreover, the results demonstrated an increase of 172% in CO2 permeability and 138% in CO2/H2 selectivity, respectively. Furthermore, integrating bimetallic PdPt nanoparticles provided an additional 197% increase in CO2/H2 selectivity, owing to the unique catalytic activities of noble metal nanoparticles. The study not only underscores the transformative potential of polymer blending and noble metal engineering, but also highlights the significance of using natural polymers for sustainable environmental solutions.

Spatially Quantitative Imaging of Enzyme Activity in a Living Cell.

Enzyme activity plays a key role in cell heterogeneity. Its spatially quantitative imaging in a living cell not only directly displays but also helps people to understand cell heterogeneity. Current methods are hard to achieve due to the short intracellular retention or lack of internal reference of the imaging probes. Herein, we rationally designed a self-referenced Raman probe Val-Cit-Cys(StBu)-Pra-Gly-CBT (Yne-CBT) which takes an intracellular cathepsin B (CTSB)-initiated CBT-Cys click reaction to yield a long-retained cyclic dimer in cell. In the meantime, Raman signal changes of its two chemical bonds (C≡C and C≡N) after the reaction are used for self-referencing and quantitative Raman imaging of CTSB activity. In vitro experiments demonstrated that, with shell-isolated nanoparticle-enhanced Raman spectroscopy technique, 20 μM Yne-CBT was able to quantitatively detect CTSB activity with a limit of detection of 61.4 U L-1. Under a homemade microfluidic channel, Yne-CBT was successfully applied for spatially quantitative imaging CTSB activity in a living cell. Our strategy provides people with a facile method to directly and quantitatively display cell heterogeneity.

Novel Schiff Base Sulfonate Derivatives as Carbonic Anhydrase and Acetylcholinesterase Inhibitors: Synthesis, Biological Activity, and Molecular Docking Insights.

Sulfonate derivatives are an essential class of compounds with diverse pharmacological applications. This study presents the synthesis and detailed characterization of six novel Schiff base sulfonate derivatives (L1-L6) through spectroscopic techniques (FTIR and NMR). Their inhibitory potential was evaluated against human carbonic anhydrase isoenzymes (hCA I and hCA II) and acetylcholinesterase (AChE), which are crucial therapeutic targets for diseases such as glaucoma, epilepsy, and Alzheimer's disease. The Kivalues for the compounds concerning AChE, hCA I, and hCA II enzymes were in the ranges of, 106.10 ± 14.73-422.80 ± 17.64 nM (THA: 159.61± 8.41 nM), 116.90 ± 24.40-268.00 ± 35.84 nM (AAZ: 439.17 ± 9.30 nM), and 177.00 ± 35.03-435.20 ± 75.98 nM (AAZ: 98.28 ± 1.69 nM), respectively. Molecular docking analyses revealed key interactions within the active sites of the enzymes, including hydrogen bonding with critical residues and π-π stacking interactions. Notably,L3demonstrated superior inhibition against hCA I (Ki: 116.90 ± 24.40 nM) and AChE (Ki: 106.10 ± 14.73 nM), positioning it as a promising lead compound. This comprehensive investigation contributes to the development of isoform-specific inhibitors for therapeutic use and provides valuable insights into their binding mechanisms.

Trisodium Citrate‐Assisted Synthesis of Edge‐Abundant Nickel‐Iron Layered Double Hydroxides for Efficient Oxygen Evolution Reaction

AbstractThe edges of layered double hydroxides (LDHs) display an exceptionally more efficient oxygen evolution reaction (OER) activity than the (001) basal plane as demonstrated by both theoretical calculations and experimental studies. However, a controllable synthesis method of LDHs with abundant edges has yet to be described. Herein, we report a strategy enabling the synthesis of nickel‐iron LDHs with abundant edges (NiFe LDHs‐E) based on the use of citrate anions as the structure‐directing agent. The edge density is characterized using spectroscopy techniques and its OER performance is compared with that of nickel‐iron LDHs with abundant basal planes (NiFe LDHs‐B). In alkaline electrolyte (1 M KOH), NiFe LDHs‐E exhibits excellent OER activity with very low overpotential (235 mV at 10 mA cm−2) and current densities (at η = 320 mV) up to sixfold higher than those of NiFe LDHs‐B. Density functional theory (DFT) calculations confirm the high OER activities ascribed to the abundant side‐plane edges with optimal strength of binding of OER intermediates. Overall, a comprehensive investigation, employing both experimental and computational methodologies, yields new insights to fabricate superior catalysts meticulously designed with specific crystal planes and unveils the crucial structural attributes, thus unleashing the limitless potential of the catalytic domain.

Fluorescent Macrocycles with Customizable Backbone: Design, Synthesis, and Detection of Explosive Picric Acid.

Synthesis of size and functional-group tunable dansyl-appended fluorescent macrocycles MC-n, MC-h, MC-p, MC-c, MC-mx, and MC-px using click reaction is reported. Macrocycles were extensively characterized by using various spectroscopic and theoretical techniques. Fluorescent macrocycles showed positive-solvatofluorism, high quantum yields, and strong interactions with nitroaromatic-explosives. Sensing in real water-sample, soil and vapor phase revealed that MC-p exhibits selective detection of picric acid containing three nitro-groups when compared to other nitroaromatics and structurally similar aromatics. Paper-strip based sensor was developed for real-time detection.

Crystallographic symmetry increasing in the pressure-induced phase transition of the hydrogen-bonded organic crystal 1-methylhydantoin.

In situ high-pressure Raman spectroscopy and synchrotron angular dispersive x-ray diffraction techniques, combined with first-principles calculations, have been performed to investigate the 1-methylhydantoin (C4H6N2O2, 1-MH) molecular crystal. High-pressure experiments have shown that phase I (monoclinic system) begins to transform into phase II (orthorhombic system) at pressures above 4.0GPa, and the transformation range is from 4.0 to 14.2GPa. It is proposed that the mechanism of phase transition is the interlayer contraction and rearrangement of the hydrogen-bonding network due to the enhanced strong hydrogen-bonded interactions at high pressures. This study provides some theoretical basis for this rare pressure-induced phase transition from low symmetry to high symmetry in organic supramolecular polymorphism.

Synthesis, Characterisation, Computational ADME studies, Pharmacological screening and In-vitro Hydrolysis studies of potential novel mutual prodrugs of N-(2,3-xylyl anthranillic acid)

In the present work we report Synthesis, Computational ADME study, Pharmacological evaluation and In-vitro hydrolysis study of new mutual prodrugs of N-(2,3-xylyl anthranillic acid) prepared with and without spacer using Dicyclohexylcarbodiimide (DCC) as coupling agent. The structures of mutual prodrugs formed were confirmed by advanced spectroscopic techniques. The title compounds were tested for analgesic activity by Eddy’s hot plate and tail-flick method; for anti-inflammatory activity by carrageenan induced rat paw edema method and for ulcerogenicity and acute oral toxicity. Title compounds exhibited promising analgesic and anti-inflammatory activity. The compounds were found to be devoid of ulcerogenicity at the test dose level and presented significant values of the ADME properties studied, obeying Lipinski Rule of five violations, good oral absorption and lipophilicity. Hydrolysis studies revealed that the compounds were sufficiently stable at pH 1.2, indicating that no appreciable hydrolysis to the free acids might occur in the stomach. The amount of free drug released on hydrolysis in 80% human plasma (pH 7.4) was greater than that released in aqueous buffers, suggesting that the rate of hydrolysis of compounds in 80% human plasma was markedly accelerated compared with that in aqueous buffers.

Synthesis and Biological Evaluation of some 2,5-Disubstituted -1,3,4- Oxadiazole Derivatives

Synthesis of some new 2, 5-diaryl-1, 3, 4-oxadiazole derivatives starting from Isoniazide (INH) is described. The target compounds 11- 20 were obtained by treating INH with various aromatic aldehydes and monosaccharides to give corresponding Schiff ’s bases 1- 10, which upon subsequent oxidation, by using either method A, B or C, yielded desired compounds. They were purified and characterized by spectroscopic techniques and elemental analyses. These compounds were evaluated for antibacterial, antifungal and antiviral activities. Compounds 11, 16 and 17 exhibited good antibacterial and antifungal activity, however, none of the compounds were enough active against various strains of virus.

Non-Aqueous Electrochemical CO2 Reduction to Multivariate C2-Products Over Single Atom Catalyst at Current Density up to 100mAcm-2.

Electrochemical CO2 reduction reaction (CO2-RR) in non-aqueous electrolytes offers significant advantages over aqueous systems, as it boosts CO2 solubility and limits the formation of HCO3 - and CO3 2- anions. Metal-organic frameworks (MOFs) in non-aqueous CO2-RR makes an attractive system for CO2 capture and conversion. However, the predominantly organic composition of MOFs limits their electrical conductivity and stability in electrocatalysis, where they suffer from electrolytic decomposition. In this work, electrically conductive and stable Zirconium (Zr)-based porphyrin MOF, specifically PCN-222, metalated with a single-atom Cu has been explored, which serves as an efficient single-atom catalyst (SAC) for CO2-RR. PCN- 222(Cu) demonstrates a substantial enhancement in redox activity due to the synergistic effect of the Zr matrix and the single-atom Cu site, facilitating complete reduction of C2 species under non-aqueous electrolytic conditions. The current densities achieved (≈100mAcm- 2) are 4-5 times higher than previously reported values for MOFs, with a faradaic efficiency of up to 40% for acetate production, along with other multivariate C2 products, which have never been achieved previously in non-aqueous systems. Characterization using X-ray and various spectroscopic techniques, reveals critical insights into the role of the Zr matrix and Cu sites in CO2 reduction, benchmarking PCN-222(Cu) for MOF-based SAC electrocatalysis.

Spectroscopic Signatures of Ultra-Thin Amorphous Carbon with the Tuned Disorder Directly Grown on a Dielectric Substrate.

The reduced structural complexity of atomically thin amorphous carbons makes it suitable for semiconductor technology. Inherent challenges arise from transfer processes subsequent to growth on metallic substrates, posing significant challenges to the accurate characterization of amorphous materials, thereby compromising the reliability of spectroscopic analysis. Here this work presents a novel approach: direct growth of ultra-thin amorphous carbon with tuned disorder on a dielectric substrate (SiO2/Si) using photochemical reaction and thermal annealing process with a solid precursor. This work characterizes the amorphous carbon films' disorder using spectroscopic techniques, such as X-ray photoelectron spectroscopy, Electron energy loss spectroscopy, and Raman spectroscopy, which offer greater convenience compared to microscopy-based studies. This method, rooted in comprehensive spectroscopic characterization, elucidates characteristic signatures inherent to the amorphous carbon films. These findings reveal that Raman spectroscopy is particularly effective in identifying the amorphous phase of atomically-thin carbon. Additionally, I-V characterization and high-frequency dielectric measurements showcase the potential application of directly grown amorphous carbon films in the semiconductor industry, where nanometer-level thin conductors and dielectrics are commonly utilized. This transfer-free characterization method provides a useful tool to find the correlation between atomic structure and electrical/optical properties, giving valuable insights into comprehensive crystallographic fundamental research.

Size-Dependent Multiexciton Dynamics Governs Scintillation From Perovskite Quantum Dots.

The recent emergence of quantum-confined nanomaterials in the field of radiation detection, in particular lead halide perovskite nanocrystals, offers scalability and performance advantages over conventional materials. This development raises fundamental questions about the mechanism of scintillation itself at the nanoscale and the role of particle size, arguably the most defining parameter of quantum dots. Understanding this is crucial for the design and optimization of future nanotechnology scintillators. In this work, these open questions are addressed by theoretically and experimentally studying the size-dependent scintillation of CsPbBr3 nanocrystals using a combination of Monte Carlo simulations, spectroscopic, and radiometric techniques. The results show that the simultaneous effects of size-dependent energy deposition, (multi-)exciton population, and light emission under ionizing excitation, typical of confined particles, combine to maximize the scintillation efficiency and time performance of larger nanocrystals due to greater stopping power and reduced Auger decay. The agreement between theory and experiment produces a fully validated descriptive model that predicts the scintillation yield and kinetics of nanocrystals without free parameters, providing fundamental guidance for the rational design of nanoscale scintillators.

Synthesis and Chemical Characterisation of Some Novel Substituted Flavone’s for It’s Anti Microbial Activity

The present study reports an experiment on some derivatives of 2-phenyl-chromen-4-one (flavone ring) have a proven inhibitory activity against a variety of human pathogens, including antibiotic-resistant Gram-positive and Gram-negative bacteria and antifungal activities screened against four human pathogenic bacteria and two phytopathogenic fungi. Flavanoid derivatives have been made through Algar– Flynn–Oyamada reaction from hydroxyacetophenones and aromatic-aldehydes. The structures of the synthesized compounds were elucidated by UV, IR and 1H NMR spectroscopic techniques, and elemental analysis. These compounds are potentially useful pharmacologically active compounds and are studied for biological activities like antibacterial and antifungal screens performed in vitro by the plate-hole diffusion method.