Disclosing the Biocide Activity of α-Ag2−2xCuxWO4 (0 ≤ x ≤ 0.16) Solid Solutions

In this work, α-Ag2−2xCuxWO4 (0 ≤ x ≤ 0.16) solid solutions with enhanced antibacterial (against methicillin-resistant Staphylococcus aureus) and antifungal (against Candida albicans) activities are reported. A plethora of techniques (X-ray diffraction with Rietveld refinements, inductively coupled plasma atomic emission spectrometry, micro-Raman spectroscopy, attenuated total reflectance–Fourier transform infrared spectroscopy, field emission scanning electron microscopy, ultraviolet–visible spectroscopy, photoluminescence emissions, and X-ray photoelectron spectroscopy) were employed to characterize the as-synthetized samples and determine the local coordination geometry of Cu2+ cations at the orthorhombic lattice. To find a correlation between morphology and biocide activity, the experimental results were sustained by first-principles calculations at the density functional theory level to decipher the cluster coordinations and electronic properties of the exposed surfaces. Based on the analysis of the under-coordinated Ag and Cu clusters at the (010) and (101) exposed surfaces, we propose a mechanism to explain the biocide activity of these solid solutions.

MOF Embedded and Cu Doped CeO2 Nanostructures as Efficient Catalyst for Adipic Acid Production: Green Catalysis

Greatly efficient chemical processes are customarily based upon a catalyst activating the process pathway to achieve higher yields of a product with desired specifications. Catalysts capable of achieving good performance without compromising green credentials are a pre-requisite for the development of a sustainable process. In this study, CeO2 nanoparticles were tested for their catalytic activity with two different configurations, one as a hybrid of CeO2 nanoparticles with Zeolitic Immidazole Framework (ZIF-67) and second being doped Cu cations into CeO2 nanoparticles. Physicochemical and catalytic activity was investigated and compared for both systems. Each hybrid was synthesized by embedding the CeO2 nanoparticles into the microporous structure of ZIF-67, and Cu doped CeO2 nanoparticles were prepared by a facile hydrothermal route. As a catalytic test, it was employed for the oxidation of cyclohexene to adipic acid (AA) as an alternative to expensive noble metal-based catalysts. Heterogeneous ZIF-67/CeO2 found catalytical activity towards the oxidation of cyclohexene with nearly complete conversion of cyclohexene into AA under moderate and co-catalyst free reaction conditions, whereas Cu doped CeO2 nanoparticles have shown no catalytic activity towards cyclohexene conversion, depicting the advantages of the porous ZIF-67 structure and its synergistic effect with CeO2 nanoparticles. The large surface area catalyst could be a viable option for the green synthesis of many other chemicals.

Adipic Acid Route: Oxidation of Cyclohexene vs. Cyclohexane

A cleaner alternative to the current inefficient oxidation of cyclohexane to adipic acid is presented. Direct oxidation of neat cyclohexene by aq. hydrogen peroxide to adipic acid is selectively achieved in good yield (46%), in the presence of the recyclable C-homoscorpionate iron(II) complex [FeCl2{κ3-HC(pz)3}] (pz = pyrazol-1-yl) and microwave irradiation, by a nitrous oxide-free protocol.

A biradical oxo-molybdenum complex containing semiquinone and o-aminophenol benzoxazole-based ligands

We report a new mononuclear molybdenum(iv) complex, MoOLBISLSQ, in which LSQ (2,4-di-tert-butyl o-semibenzoquinone ligand) has been prepared from the reaction of the o-iminosemibenzoquinone form of a tridentate non-innocent benzoxazole ligand, LBIS, and MoO2(acac)2. The complex was characterized by X-ray crystallography, elemental analysis, IR and UV-vis spectroscopy and magnetic susceptibility measurements. The crystal structure of MoOLBISLSQ revealed a distorted octahedral geometry around the metal centre, surrounded by one O and two N atoms of LBIS and two O atoms of LSQ. The effective magnetic moment (μ eff) of MoOLBISLSQ decreased from 2.36 to 0.2 μB in the temperature range of 290 to 2 K, indicating a singlet ground state caused by antiferromagnetic coupling between the metal and ligand centred unpaired electrons. Also, the latter led to the EPR silence of the complex. Cyclic voltammetry (CV) studies indicate both ligand and metal-centered redox processes. MoOLBISLSQ was applied as a catalyst for the oxidative cleavage of cyclohexene to adipic acid and selective oxidation of sulfides to sulfones with aqueous hydrogen peroxide.

Unconventional Magnetization Generated from Electron Beam and Femtosecond Irradiation on α-Ag2WO4: A Quantum Chemical Investigation

Novel magnetic metals and metal oxides that use both the spin and charge of an electron offer exciting technological applications. Their discovery could boost research on functional nanoscale materials. Here, for the first time, we report the magnetization of α-Ag2WO4 under electron beam and femtosecond laser irradiation. The formation and growth of silver oxides (AgO, Ag2O, and Ag3O4) and Ag nanofilaments can be observed on the surface of α-Ag2WO4 crystals. These features were also present in the composition of an extruded material and could open new avenues for surface magnetism studies. In order to understand these results, we used first-principles density functional theory calculations. This allowed us to investigate several potential scenarios for controlling magnetic properties. The effect of electron addition on the crystalline structures of α-Ag2WO4, Ag3O4, Ag2O, and AgO has been analyzed in detail. The creation of Ag and O vacancies on these compounds was also analyzed. Based on structural and electronic changes at the local coordination site of Ag, a mechanism was proposed. The mechanism illustrates the processes responsible for the formation and growth of metallic Ag and the magnetic response to electron beam irradiation.

One-pot oxidative cleavage of cyclic olefins for the green synthesis of dicarboxylic acids in Pickering emulsions in the presence of acid phosphate additives

Dicarboxylic acids were prepared by the oxidative cleavage of cyclic alkenes by adsorbing dodecyltrimethylammonium phosphotungstate particles and silica particles functionalized with octadecyl chains and sulfonic acid groups at the W/O interface.

Heterogeneous Gold Catalysis: From Discovery to Applications

In the present review, the important and current developments of gold catalysts for a wide range of applications are comprehensively summarized. This review also provides a detailed study of the literature data concerning the preparation, characterization, and catalytic applications of gold catalysts. Additionally, the main aspects of using supported gold nanoparticles (AuNPs) as catalysts for oxidation reactions are considered. In particular, the oxidation of benzyl alcohol to benzaldehyde and the production of adipic acid from cyclohexane are discussed in detail. Lastly, the key properties of gold catalysts are described, and an outlook on the application of gold catalysts is presented.

Synthesis of Benzoxazoles, Benzimidazoles, and Benzothiazoles Using a Brønsted Acidic Ionic Liquid Gel as an Efficient Heterogeneous Catalyst under a Solvent-Free Condition

Herein, we introduce a reusable Brønsted acidic ionic liquid gel (BAIL gel) obtained by treating 1-methyl-3-(4-sulfobutyl)-1H-imidazolium hydrogen sulfate with tetraethyl orthosilicate (TEOS). The grafting of the Brønsted acidic ionic liquid to the surface of TEOS has increased the catalytic activity of the material and also simplified catalyst recovery from the reaction mixture. This reaction has a wide substrate scope, and the BAIL gel represents a new catalyst for the synthesis of benzoxazoles, benzimidazoles, and benzothiazoles. The method shows attractive characteristics such as high yields, recyclable catalyst, and work-up simplicity. More importantly, no additional additives or volatile organic solvent and inert atmosphere are required for the reaction, and the BAIL gel has shown a great promise for industrial applications. To the best of our knowledge, the synthesis of benzoxazoles, benzimidazoles, and benzothiazoles using a recyclable heterogeneous ionic liquid gel was not previously reported in the literature.

Recent trends in the development of sustainable catalytic systems for the oxidative cleavage of cycloalkenes by hydrogen peroxide

This review proposes a comprehensive, critical, and accessible assessment of reaction conditions for cycloolefin oxidative cleavage regarding green chemistry criteria.

Towards the scale-up of the formation of nanoparticles on α-Ag2WO4 with bactericidal properties by femtosecond laser irradiation

In recent years, complex nanocomposites formed by Ag nanoparticles coupled to an α-Ag₂WO₄ semiconductor network have emerged as promising bactericides, where the semiconductor attracts bacterial agents and Ag nanoparticles neutralize them. However, the production rate of such materials has been limited to transmission electron microscope processing, making it difficult to cross the barrier from basic research to real applications. The interaction between pulsed laser radiation and α-Ag₂WO₄ has revealed a new processing alternative to scale up the production of the nanocomposite resulting in a 32-fold improvement of bactericidal performance, and at the same time obtaining a new class of spherical Ag_xW_yO_z nanoparticles.

Uncovering the metastable γ-Ag2WO4 phase: a joint experimental and theoretical study

A combination of experiments and simulation provides a fundamental understanding of the structure of materials.

Preparation of CoWO4/g-C3N4 and its Ultra-Deep Desulfurization Property

The ultra-deep desulfurization of fuel oil has become inevitable for environmental protection. Here, CoWO4/g-C3N4 was used as a catalyst, H2O2 as an oxidant, and 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4], IL) as an extractant for the oxidative desulfurization of model oil. Scanning electron microscopy, FT-IR spectroscopy, N2 adsorption isotherms, and X-ray diffraction were used to confirm the morphology, structure, and properties of the catalysts. The influence of calcination temperature, loading dose of cobalt, amount of H2O2, reaction temperature, and other parameters were investigated. The removal rate of sulfide in model oil could reach 92.9 % at 80°C in 180 min under the optimal operation conditions (V(oil) = 5 mL, T = 80°C, m(catalyst) = 0.03 g, V(H2O2) = 0.4 mL, t = 180 min, V(IL) = 1.0 mL). In addition, the catalyst was reused five times with no significant reduction in the catalytic activity.

In situ growth of Ag nanoparticles on α-Ag2WO4 under electron irradiation: probing the physical principles

Exploiting the plasmonic behavior of Ag nanoparticles grown on α-Ag2WO4 is a widely employed strategy to produce efficient photocatalysts, ozone sensors, and bactericides. However, a description of the atomic and electronic structure of the semiconductor sites irradiated by electrons is still not available. Such a description is of great importance to understand the mechanisms underlying these physical processes and to improve the design of silver nanoparticles to enhance their activities. Motivated by this, we studied the growth of silver nanoparticles to investigate this novel class of phenomena using both transmission electron microscopy and field emission scanning electron microscopy. A theoretical framework based on density functional theory calculations (DFT), together with experimental analysis and measurements, were developed to examine the changes in the local geometrical and electronic structure of the materials. The physical principles for the formation of Ag nanoparticles on α-Ag2WO4 by electron beam irradiation are described. Quantum mechanical calculations based on DFT show that the (001) of α-Ag2WO4 displays Ag atoms with different coordination numbers. Some of them are able to diffuse out of the surface with a very low energy barrier (less than 0.1 eV), thus, initiating the growth of metallic Ag nanostructures and leaving Ag vacancies in the bulk material. These processes increase the structural disorder of α-Ag2WO4 as well as its electrical resistance as observed in the experimental measurements.

Influence of electron beam irradiation on structural and optical properties of α-Ag2WO4 nanoparticles

The influence of 8MeV electron beam irradiation on the structural and optical properties of silver tungstate (α-Ag2WO4) nanoparticles synthesized by chemical precipitation method was investigated. The dose dependent effect of electron irradiation was investigated by various characterization techniques such as, X-ray diffraction, scanning electron microscopy, UV-vis absorption spectroscopy, photoluminescence and Raman spectroscopy. Systematic studies confirm that electron beam irradiation induces non-stoichiometry, defects and particle size variation on α-Ag2WO4, which in turn results changes in optical band gap, photoluminescence spectra and Raman bands.

In situ Transmission Electron Microscopy observation of Ag nanocrystal evolution by surfactant free electron-driven synthesis

The study of the interaction of electron irradiation with matter and the response of the material to the passage of electrons is a very challenging problem. However, the growth mechanism observed during nanostructural evolution appears to be a broad and promising scientific field in nanotechnology. We report the in situ TEM study of nanostructural evolution of electron-driven silver (Ag) nanocrystals through an additive-free synthetic procedure. Observations revealed the direct effect of the electron beam on the morphological evolution of Ag nanocrystals through different mechanisms, such as mass transport, site-selective coalescence, and an appropriate structural configuration after coalescence leading to a more stable configuration. A fundamental understanding of the growth and formation mechanisms of Ag nanocrystals, which interact with the electron beam, is essential to improve the nanocrystal shape-control mechanisms as well as the future design and study of nanomaterials.

Highly dispersible bis-imidazolium/WO42− modified magnetic nanoparticles: a heterogeneous phase transfer catalyst for green and selective oxidations

A novel magnetically recoverable catalyst was prepared in which magnetic nanoparticles were functionalized by bis-imidazolium tungstate ionic liquid molecules.

Preparation and characterization of WO3 bonded imidazolium sulfonic acid chloride as a novel and green ionic liquid catalyst for the synthesis of adipic acid

The work represents the synthesis of a novel WO₃ bonded IL catalyst. It is used as a heterogeneous recoverable catalyst in the oxidation of cyclohexene to adipic acid.

Effects of chemical substitution on the structural and optical properties of α-Ag2−2xNixWO4(0 ≤ x ≤ 0.08) solid solutions

In this work, we investigated the effects of chemical substitution of α-Ag_2−2xNi_xWO₄(0 ≤x≤ 0.08) solid solutions prepared by a facile microwave-assisted hydrothermal method.

Synthesis and characterization of metastable β-Ag2WO4: an experimental and theoretical approach

The geometry, cluster coordination and electronic structure of metastable β-Ag₂WO₄ microcrystals were elucidated using experimental techniques and first-principles calculations.