Synthesis of Catalysts Containing Mixed Oxides of Mo‐V‐Cu‐W to Produce Acrylic Acid: A Comparison between Hydrothermal Synthesis and Coprecipitation

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Synthesis of Catalysts Containing Mixed Oxides of Mo-V-Cu-W to Produce Acrylic Acid: A Comparison between Hydrothermal Synthesis and Coprecipitation

In order to convert glycerol into acrylic acid, catalysts were synthesized containing mixed oxides of molybdenum, vanadium, and other metals like tungsten and copper via hydrothermal treatment and coprecipitation to evaluate how these preparation techniques influence the physicochemical and morphological properties of the materials and their selectivity for obtaining acrylic acid.


Abstract

Mixed oxides of Mo-V-W-Cu were prepared by three different synthesis methods, namely, evaporation (EV), hydrothermal treatment (TH), and evaporation, followed by hydrothermal treatment (EV-TH). The catalyst samples were characterized by X-ray diffraction (XRD) and fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), and N2 adsorption/desorption techniques. Subsequently, their catalytic performance was evaluated for the oxidation of acrolein to obtain acrylic acid. The results revealed that the composition of the crystalline phases of the mixed oxide catalysts influences their catalytic performance, and this effect varies depending on the synthesis method. The catalysts synthesized by EV-TH showed better catalytic results than catalysts synthesized solely via EV or TH methods. This improvement may be attributed to the higher content of vanadium oxides found in the samples of EV-TH, along with the formation of V0.35Mo4.65O14 as the predominant crystalline phase.

Development of molecular cluster models to probe pyrite surface reactivity

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Development of molecular cluster models to probe pyrite surface reactivity

Mapping the chemical interactions in pyrite enabled the development of molecular cluster models for mineral surface sites. These models serve as computational nano-reactors for exploring the atomic-scale mechanism of pyrite reactivity. The maquettes of surface sites are composed of a layer of magnetic iron sites that are connected with bridging persulfides and wrapped around a non-magnetic bulk iron core. Incompleteness of iron site chemical environment enables binding of reductants, interconversion of pyrite to an intermediate surface-associated iron-sulfur phase, and ultimately to mackinawite nanoparticles upon abiotic and biotic reductive dissolution.


Abstract

The recent discovery that anaerobic methanogens can reductively dissolve pyrite and utilize dissolution products as a source of iron and sulfur to meet their biosynthetic demands for these elements prompted the development of atomic-scale nanoparticle models, as maquettes of reactive surface sites, for describing the fundamental redox steps that take place at the mineral surface during reduction. The given report describes our computational approach for modeling n(FeS2) nanoparticles originated from mineral bulk structure. These maquettes contain a comprehensive set of coordinatively unsaturated Fe(II) sites that are connected via a range of persulfide (S2 2−) ligation. In addition to the specific maquettes with n = 8, 18, and 32 FeS2 units, we established guidelines for obtaining low-energy structures by considering the pattern of ionic, covalent, and magnetic interactions among the metal and ligand sites. The developed models serve as computational nano-reactors that can be used to describe the reductive dissolution mechanism of pyrite to better understand the reactive sites on the mineral, where microbial extracellular electron-transfer reactions can occur.

Synthesis and Characterization of Ultra‐Small Gold Nanoparticles in the Ionic Liquid 1‐Ethyl‐3‐methylimidazolium Dicyanamide, [Emim][DCA]

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Synthesis and Characterization of Ultra-Small Gold Nanoparticles in the Ionic Liquid 1-Ethyl-3-methylimidazolium Dicyanamide, [Emim][DCA]

Formation of 1 nm-sized gold clusters with long-stability in an ionic liquid is reported. Formation via a three-stage process is suggested. Cluster growth from gold nuclei takes place according to the Lifshitz–Slyozov–Wagner (LSW) model followed by oriented attachment to form colloidal stable clusters.


Abstract

We report on gold clusters with around 62 gold atoms and a diameter of 1.15±0.10 nm. Dispersions of the clusters are long-term stable for two years at ambient conditions. The synthesis was performed by mixing tetrachloroauric acid (HAuCl4 ⋅ 3 H2O) with the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCA]) at temperatures of 20 to 80 °C. Characterization was performed with small-angle X-ray scattering (SAXS), UV-Vis spectroscopy, and MALDI-TOF mass spectrometry. A three-stage model is proposed for the formation of the clusters, in which cluster growth from gold nuclei takes place according to the Lifshitz-Slyozov-Wagner (LSW) model followed by oriented attachment to form colloidal stable clusters.

Synthesis of Double Defects in g‐C3N4 to Enhance the H2O2 Production by Dual‐Electron O2 Reduction

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Synthesis of Double Defects in g-C3N4 to Enhance the H2O2 Production by Dual-Electron O2 Reduction

Light to H2O2 : The nanosheet photocatalysts containing double defects were prepared by the calcination method. The microstructure, photoelectric properties, and photocatalytic performance of the materials were systematically investigated. The −C≡N groups promote the adsorption of H+ and the S-defects provide the active center for the adsorption and activation of O2.


Abstract

In this work, the graphitic carbon nitride with −C≡N defects and S-defects (N2−SCN-4) was constructed. The H2O2 production efficiency of N2−SCN-4 was 1423.3 μmol g−1 h−1 under the visible light (λ≥420 nm) irradiation, which was 15.4 times that of pristine g-C3N4. The −C≡N groups promote the adsorption of H+ and the S-defects provide the active center for the adsorption and activation of O2. Furthermore, the surface morphology, microstructure, and photoelectric chemical properties of samples were investigated by a series of characterizations, and the response range of N2−SCN-4 to visible light increases obviously. Meanwhile, the efficiency of photo-produced charge separation and the selectivity of H2O2 production were discussed in detail. The experimental and characterization results confirmed that the charge separation efficiency and the selectivity of the 2e− O2 reduction reaction (ORR) were improved under the synergistic effect of the double defects. This work provides a strategy for improving the photocatalytic performance of photocatalysts.

Color Tunable Emission and Oxygen Sensing from a Discrete Europium−Pyrene Assembly

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Color Tunable Emission and Oxygen Sensing from a Discrete Europium−Pyrene Assembly

The multi-functional discrete Eu3+−pyrene assembly shows both color tunable emission (blue through to red including white-emission) and molecular oxygen sensing properties.


Abstract

We report the synthesis of a new pyrene, dipicolinic acid-based ligand (L1H) and its corresponding multi-emissive and multifunctional europium complex [Eu(L1 )3] that is capable of single component color switchable emission from red to blue and also white. At high concentration (10 mM) the single component system results in near pure white emission (CIE coordinates x,y=0.329, 0.324). Furthermore, the system showed ratiometric oxygen sensing with oxygen significantly quenching the pyrene centered emission but not the Eu3+ emission, resulting in an overall emission color change from blue to red on increasing oxygen content.

The Unique Ambiphilicity of Tellurium in the [MesitylTe(I)(I2)(I3)]− Anion

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The Unique Ambiphilicity of Tellurium in the [MesitylTe(I)(I2)(I3)]− Anion

A first example of a tellurium(II) compound with three different bonding modes to iodine featuring covalent and non-covalent bonds such as two different σ-hole interactions is introduced: [MesTe(I)(I2)(I3)]−. The character of chalcogen and halogen bonds are evaluated by the combination of crystallographic data and computational methods.


Abstract

A first example of an aryltellurium(II) compound with three different bonding modes to iodine featuring covalent and non-covalent bonds such as two orthogonal, ambiphilic σ-hole interactions is introduced: [MesTe(I)(I2)(I3)]−. It is a member of a series of mesityltellurenyl anions, which are formed during reactions of (MesTe)2 with ZnI2, phenanthroline (phen) and iodine. [Zn(phen)3][MesTe(I)2] (1), [Zn(phen)3][{MesTe(I)-(I)…Te(I)Mes}{MesTeI2}] (2) and [Zn(phen)3][MesTe(I)(I2)(I3)][MesTeI2] (3) are isolated depending on the amount of iodine used. The products contain tellurium atoms bonded to a variety of iodine species (I−, μ2-I−, I2 and I3 −) and are, thus, perfectly suitable to explore the amphiphilic behavior of tellurium(II) and its relevance for the formation of non-covalent bonds, where tellurium acts as both donor and acceptor simultaneously. The character of chalcogen and halogen bonds are evaluated by the combination of crystallographic data and computational methods.

Strong‐field coherent control of the proton momentum distribution arising from the n$$ n $$‐photon (n=1,2,3$$ n=1,2,3 $$) field‐dressed adiabatic potentials of H2+$$ {}_2^{+} $$

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Strong-field coherent control of the proton momentum distribution arising from the n$$ n $$-photon (n=1,2,3$$ n=1,2,3 $$) field-dressed adiabatic potentials of H2+$$ {}_2^{+} $$

Proton distributions in dissociative-ionization of 2+$$ {}_2^{+} $$ are controlled by manipulating parameters of the strong field laser pulse to yield the desired distributions we want to aim for. The captured images of the distributions have advanced our knowledge of controlling a chemical reaction in more systematic ways. In this study, I have successfully controlled the proton distributions to move preferentially in one direction namely to the right side of H-H+ molecule using a specific laser parameter.


Abstract

A systematic directionality coherent control of total proton momentum distributions in the dissociative-ionization of H2+$$ {}_2^{+} $$ subjected to a strong field of six-cycle laser pulses in a full range of carrier-envelope phase ϑ$$ \vartheta $$ is studied by solving a non-Born-Oppenheimer time-dependent Schrödinger equation numerically. The trend of distributions involves insightful investigation into the spatial-temporal overlap between nuclear wave packets evolving on the coupled field-dressed electronic potentials of H2+$$ {}_2^{+} $$ associated with the n$$ n $$-photon potential crossings. This leads to new quantum images for the nonlinear nonperturbative interaction of H2+$$ {}_2^{+} $$ with a strong field. It turns out that the symmetry of the ϑ$$ \vartheta $$-dependent momentum distribution begins to break after undergoing interaction with one-photon field-dressed potentials. At this point, the most probable proton momentum distribution tends to move in a forward direction indicating also that the three-photon field-dressed potentials strongly govern the dissociative-ionization pathway.