Adsorption of Glucose Molecules on Stainless Steel Enables Ni‐Rich Passivation Film

Posted on 5 October 2023 by

For diverse applications of stainless steel, precise control of the surface layer's composition and morphology is essential. In this work, we study the formation of a nickel-rich passive film via electrochemical potential sweep in an alkaline solution containing glucose. In addition, the nickel- or iron-rich passive surface layer is capable of reversible interchange by adding or removing glucose.

Abstract

Stainless steel (SS) is well known for its remarkable versatility. Besides the importance of passivation film for durability and stability of SS, the composition and morphology of passive surface layer have to be precisely modified to create an alloy that is optimal for specific purposes. Herein, we report on the electrochemical preparation of nickel-enriched passive film which is accomplished by the preferential adsorption of glucose on nickel species among constituents of SS. The presence of nickel-rich surface and the exposure of nickel on the outmost surface layer participating in surface reactions are verified by monitoring redox couple of Ni²⁺/Ni³⁺ as well as elemental analyses (TEM-Energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy). Reversible interchange of nickel-rich into iron-rich surface and vice versa is possible by adding or removing glucose. We find that molecules having more than tri-dentate of hydroxy groups (e. g. glycerol) is required for the formation of Ni-rich surface (chelate effect).

Reaction Pathways in Carbonates and Esters

Posted on 5 October 2023 by nPietro Tundo, nFabio Aricòn

This review reports a comparison between Carbonates and Esters chemistry. Analysis of the experimental data led to propose a Model outlining the differences in energy profiles among the reaction mechanisms of these compounds. Several case studies were herein discussed so to corroborate the proposed theoretical energy model.

Abstract

This review reports on the competition/collaboration among intertwined base-catalyzed acyl cleavage bimolecular mechanism (B_Ac2)/base-catalyzed alkyl cleavage bimolecular mechanism (B_Al2) or the related acid catalyzed mechanisms A_Ac2/A_Al2 and A_Al1 concerning Carbonates chemistry also in comparison with Esters reactivity. A consistent analysis of the experimental data so far available in the literature led to proposing a theoretical Model outlining the differences in energy profiles among the above-mentioned reaction mechanisms. The reactions involving Carbonates are so tightly interconnected that the formation of the final product is driven by a precise not interfering sequence of B_Ac2-B_Al2 (or A_Al2-A_Ac2) mechanisms. When entropic effect (in cyclisations) or an anchimeric effect (mustard carbonates, isosorbide methylation) are involved, the difference in Gibbs activation energy is reduced allowing chemical transformations that would normally require higher temperatures. In these cases (intramolecular alkylation, cyclisation reaction, and alkylation by mustard carbonates) only a catalytic amount of base is required as the leaving group CH₃OCOO⁻ decomposes restoring the base. As Green Chemistry is concerned, syntheses with much lower environmental impact are achieved with Carbonates when compared with the corresponding ones involving Chlorine chemistry.

Multicomponent Synthesis Strategies, Catalytic Activities, and Potential Therapeutic Potential of Pyranocoumarins: A Comprehensive Review

Posted on 5 October 2023 by nJayalakshmi M, nFrancis Joy, nAatika Nizam, nSuresh Babu Naidu Krishnan

Abstract

Fused coumarins, because of their remarkable biological and therapeutic properties, particularly pyranocoumarins, have caught the interest of synthetic organic chemists, leading to the development of more efficient and environmentally friendly protocols for synthesizing pyranocoumarin derivatives. These compounds are the most promising heterocycles discovered in both natural and synthetic sources, with anti-inflammatory, anti-HIV, antitubercular, antihyperglycemic, and antibacterial properties. This review employed the leading scientific databases Scopus, Web of Science, Google Scholar, and PubMed up to the end of 2022, as well as the combining terms pyranocoumarins, synthesis, isolation, structural elucidation, and biological activity. Among the catalysts employed, acidic magnetic nanocatalysts, transition metal catalysts, and carbon-based catalysts have all demonstrated improved reaction yields and facilitated reactions under milder conditions. Herein, the present review discusses the various multicomponent synthetic strategies for pyranocoumarins catalyzed by transition metal-based catalysts, transition metal-based nanocatalysts, transition metal-free catalysts, carbon-based nanocatalysts, and their potential pharmacological activities.

Comparative Study between 2‐Furonitrile and 2‐Cyanopyridine as Dehydrants in Direct Synthesis of Dialkyl Carbonates from CO2 and Alcohols over Cerium Oxide Catalyst

Posted on 5 October 2023 by

Which is better? The performance of 2-cyanopyridine and 2-furonitrile as a dehydrant has been compared in the CeO₂-catalyzed direct synthesis of dialkyl carbonates from CO₂ and various alcohols. The affinity of nitrile dehydrant and CeO₂ as well as bulkiness of alkyl chain in alcohols are important factors.

Abstract

The shift of equilibrium by removing water with nitrile dehydrants is crucial for CeO₂-catalyzed synthesis of dialkyl carbonates from CO₂ and alcohols. Two nitriles – 2-cyanopyridine and 2-furonitrile – were previously found as effective dehydrants, yet their detailed comparison as well as exploration of potential of 2-furonitrile remain insufficient. Herein, the performance of 2-cyanopyridine and 2-furonitrile was compared in the synthesis of various dialkyl carbonates. 2-furonitrile was found to be superior to 2-cyanopyridine in the synthesis of dialkyl carbonates from CO₂ and bulky or long-chain (≥C3) alcohols. Namely, the yield of diisopropyl carbonate (up to 50 %) achieved using CeO₂ and 2-furonitrile is comparable to or even higher than previously reported ones. Meanwhile, 2-cyanopyridine acted as a better dehydrant than 2-furonitrile in the synthesis of dimethyl carbonate and diethyl carbonate. The adsorption experiments and density functional theory calculations have indicated that the better performance of 2-furonitrile compared to 2-cyanopyridine in the synthesis of dialkyl carbonates from bulky or long-chain alcohols is due to the weaker interaction of 2-furonitrile with the CeO₂ surface. Such weak interaction of 2-furonitrile offers a larger reaction field on the catalyst surface for both CO₂ and alcohols.

Unveiling the Anthelminthic Potential of Merremia vitifolia Stem through in Vitro and in Silico Approach

Posted on 5 October 2023 by nFakhrul Islam, nMohammad Shariful Islam, nKawser Ahmed, nMuhammed Amanatn

Abstract

This study aimed to assess the anthelmintic activity of methanol extracts from Merremia vitifolia stems using a combination approach encompassing experimental, in vitro, and in silico evaluations. Despite the well-recognized pharmacological properties of M. vitifolia, its potential as an anthelmintic agent remained unexplored. This plant's anthelmintic potential was assessed on adult earthworms (Pheretima posthuma), revealing a dose-dependent reduction in spontaneous motility leading to paralysis and eventual mortality. The most effective dose of M. vitifolia (200 mg/ml) for anthelmintic effects on Pheretima posthuma was identified. Complementary in silico investigations were also conducted, employing Autodock PyRx 0.8 for docking studies of reported M. vitifolia compounds. Notably, quercetin emerged as a promising candidate with superior binding energies against β-tubulin (−8.3 Kcal/mol). Moreover, this comprehensive research underlines the anthelmintic potential of Merremia vitifolia stem extract and highlights quercetin as a noteworthy compound for further investigation in the quest for novel anthelmintic agents.

Aptamers: Features, Synthesis and Applications

Posted on 5 October 2023 by

Abstract

Aptamers have become a topic of interest among the researchers and scientists since they not only possess all of the benefits of antibodies but also possess special qualities including heat stability, low cost, and limitless uses⋅ Here we give a review about the features, applications, and challenges of aptamers and also how they are beneficial over the antibodies for biomedical applications. Their unique features make aptamers a prominent tool in therapeutics, diagnostics, biosensors and targeted drug delivery. In conclusion, aptamers represent exciting materials for a variety of applications and can be modified to improve their properties and to extend their applications in biomedical field.

Graphene Doped Carbon‐Gels and MnO2 for Next Generation of Solid‐State Asymmetric Supercapacitors

Posted on 5 October 2023 by

Solid-state asymmetric supercapacitors: The supercapacitor with asymmetric configuration with the graphene-doped carbon xerogel in the negative electrode and the manganese oxide in the positive electrode, along with the use of Na⁺-form Aquivion electrolyte membrane as solid electrolyte, presents great stability in a wide operational voltage window and a very low self-discharge rate.

Abstract

Supercapacitors are playing a very relevant role in many applications due to their capability to supply high power density and long durability. However, there is a growing demand to increase their energy density, in gravimetric and volumetric basis. There are different strategies to increase supercapacitor performance by improving the active materials used in the electrodes, the type of electrolyte used or even the configuration employed in the cell. In this work, a combination of these strategies is presented with the use of different active materials, electrolytes, and symmetric vs. asymmetric configuration. The supercapacitor with asymmetric configuration using the graphene-doped carbon xerogel in the negative electrode and the manganese oxide in the positive electrode, along with the use of Na⁺-form Aquivion electrolyte membrane as solid electrolyte, seems to be a promising combination to obtain a substantial enhancement of both gravimetric and volumetric capacitance. Furthermore, the device presents great stability in a wide operational voltage window from 0 to 1.8 V and with a neutral pH polymer electrolyte which contributes to improve the performance, safety, and long cycle life of the device.

Single‐Atom and Dual‐Atom Electrocatalysts: Synthesis and Applications

Posted on 5 October 2023 by

This article is a detailed review of ADCs in the field of electrocatalysis: the economic production, electrocatalytic reaction pathways and associated mechanisms, uncovered structure-performance relationships, the major challenges and opportunities in this field. This review provides a systematic summary in the light of the differences in their electrocatalytic performances for a certain reaction due to the differences in preparation strategies, active site design, etc.

Abstract

Distinguishing themselves from nanostructured catalysts, single-atom catalysts (SACs) typically consist of positively charged single metal and coordination atoms without any metal-metal bonds. Dual-atom catalysts (DACs) have emerged as extended family members of SACs in recent years. Both SACs and DACs possess characteristics that combine both homogeneous and heterogeneous catalysis, offering advantages such as uniform active sites and adjustable interactions with ligands, while also inheriting the high stability and recyclability associated with heterogeneous catalyst systems. They offer numerous advantages and are extensively utilized in the field of electrocatalysis, so they have emerged as one of the most prominent material research platforms in the direction of electrocatalysis. This review provides a comprehensive review of SACs and DACs in the field of electrocatalysis: encompassing economic production, elucidating electrocatalytic reaction pathways and associated mechanisms, uncovering structure-performance relationships, and addressing major challenges and opportunities within this domain. Our objective is to present novel ideas for developing advanced synthesis strategies, precisely controlling the microstructure of catalytic active sites, establishing accurate structure-activity relationships, unraveling potential mechanisms underlying electrocatalytic reactions, identifying more efficient reaction paths, and enhancing overall performance in electrocatalytic reactions.

Molecular Oxygen Trimer: Multiplet Structures and Stability

Posted on 5 October 2023 by

The dependence of the triplet PES with the hyperangles is used to interpret the ground state DMC wavefunction, revealing it to be very floppy. When restricted ranges are analysed, the distributions connect with the local minima of C _2v and C ₂ symmetries. On the contrary, the vibrationally averaged structures are consistent with an equilateral triangle due to permutational symmetry.

Abstract

We present a detailed theoretical study of the molecular oxygen trimer where the potential energy surfaces of the seven multiplet states have been calculated by means of a pair approximation with very accurate dimer ab initio potentials. In order to obtain all the states a matrix representation of the potential using the uncoupled spin representation has been applied. The and states are nearly degenerate and low-lying isomers appear for most multiplicities. A crucial point in deciding the relative stabilities is the zero-point energy which represents a sizable fraction of the electronic well-depth. Therefore, we have performed accurate diffusion Monte Carlo studies of the lowest state in each multiplicity. Analysis of the wavefunction allows a deeper interpretation of the cluster structures, finding that they are significantly floppy in most cases.

Reversible Electrochemical Conversion Reaction for Selective Ion Removal and Recovery

Posted on 5 October 2023 by nYilong Yang, nJiaming Miao, nKan Zhangn

Getting ions back! Due to the high selectivity and reversibility of the conversion reaction, it is possible to selectively remove and recover ions from the solution. This Concept highlights the great advantages and state-of-the-art efforts of the conversion reaction for selective removal and recovery of ions and puts forward further improvement.

Abstract

Capacitive deionization (CDI) is a green and pollution-free emerging technology that can be used for ions removal and recovery from water. However, the traditional electro-adsorption process to achieve ions removal faces the challenges of non-selectivity, low efficiency and difficult ion recovery. In recent years, the conversion reaction has attracted wide attention due to its high selectivity, reversibility and excellent desalination ability for ions removal and recovery. This concept article will focus on the connotation and representative applications of conversion reactions that can be used for ion-selective removal and recovery and put forward the perspectives and outlooks of conversion reactions.