Monthly Archives: March 2024

Carbon quantum dots for efficient hydrogen production: A critical review

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Carbon quantum dots for efficient hydrogen production: A critical review

Carbon quantum dots (CQDs), or fluorescent carbon nanoparticles, have attracted a lot of attention due to their many uses in chemical sensing, biomedical imaging, nanotechnology, photovoltaics, LEDs, and hydrogen production. This review's main goal is to provide a detailed analysis and highlight the revolutionary potential of CQDs in advancing hydrogen-generating technology.


Abstract

Fluorescent carbon nanoparticles, also known as carbon quantum dots (CQDs), have piqued the interest of researchers due to their numerous uses in chemical sensing, biomedical imaging, nanotechnology, photovoltaics, LEDs, and hydrogen generation. Aside from their optical brilliance, CQDs have benefits like low toxicity, environmental friendliness, cost-effectiveness, and ease of manufacture, with adjustable properties via surface passivation and functionalization. This review article goes over CQDs in-depth, addressing synthesis advances, benefits, limits, various synthesis processes, and prospective hydrogen generation applications. While CQDs have photocatalytic properties, they confront a few challenges, including low quantum yields, spectrum limitations, photostability limitations, limited catalytic activity, scaling difficulties, and environmental issues. Thorough research is required to use CQDs in sustainable hydrogen generation. Despite obstacles, CQD research remains appealing, with transformational promise for a cleaner and more sustainable energy future through controlled synthesis approaches displaying CQDs’ many uses.

High‐Throughput Colorimetric Detection and Quantification of Indoles and Pyrroloindoles for Enzymatic Activity Determination

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High-Throughput Colorimetric Detection and Quantification of Indoles and Pyrroloindoles for Enzymatic Activity Determination

Multiple enzymes catalyze the formation of pyrroloindoles from indoles, usually coupled with a functional group transfer in the 3-position. In this work, two high-throughput complementary absorbance-based assays were developed for the monitoring of substrate depletion (indole) and product formation (pyrroloindole). The assays were used successfully for enzymatic activity determination, but can be also used for the quantification of natural products.


Abstract

Indoles and pyrroloindoles are structural motifs present in many biologically active natural products. Multiple classes of enzymes catalyze the transformation of indoles into pyrroloindoles via group transfer followed by intramolecular cyclization, such as peroxydases, methyltransferases, and prenyltransferases. Due to the selective introduction of a stereogenic center, these enzymes receive increasing attention as catalytic tools for the production of pharmacologically relevant compounds. Two new colorimetric assays are described in this work, which allow for the quantification of such enzymatic reactions from the perspective of the substrate and the product. For the substrates, the indole assay is based on a modified version of the Ehrlich test, with the use of light as a driving force for color formation. The pyrroloindole assay uses cerium sulfate as a reagent for the colorimetric quantification of the enzymatic products. The assays are complementary and both were successfully utilized for enzymatic activity determination of a C3-indole methyltransferase. They can facilitate high-throughput screening of mutant libraries, offering support for the engineering of such enzymes, but can also be used as stand-alone methods for the detection and quantification of natural products.

The Transthyretin Protein and Amyloidosis – an Extraordinary Chemical Biology Platform

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The Transthyretin Protein and Amyloidosis – an Extraordinary Chemical Biology Platform


Abstract

The amyloidoses are diseases caused by accumulation of amyloid fibrils from over 40 different human misfolded proteins in various organs of the body depending on precursor protein. Amyloidogenesis is a self-perpetuating reaction with deleterious consequences causing degeneration in cells and organs where depositions occur. Transthyretin, TTR, is an amyloidogenic protein causing sporadic disease from the wild-type protein during aging and from numerous different autosomal dominant familial mutations at earlier ages depending on the sequence of the hereditary variant. Until recently the disease process was poorly understood, and therapies were scarce. Over the past decades, spurred by clinical data, using chemical biology research, the mechanisms of TTR production and misfolding have been elucidated affording almost complete coverage of the TTR amyloidogenesis pathway to be targeted. This translational science success has provided a plethora of therapeutic options for the TTR amyloidoses providing an inspiring example for success in previously intractable diseases.

Recent Advances in Hydrodeoxygenation of Lignin‐Derived Phenolics over Metal‐Zeolite Bifunctional Catalysts

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Recent Advances in Hydrodeoxygenation of Lignin-Derived Phenolics over Metal-Zeolite Bifunctional Catalysts

Metal-zeolite bifunctional catalysts, incorporating a judicious combination of metal and acid functionalities within confined spaces, have been widely acknowledged as highly efficient catalysts for the hydrodeoxygenation of lignin-derived phenolics to hydrocarbons. Elucidating the distinct roles and synergistic effects of these active components offers valuable insights for the rational design of advanced catalysts for the hydrodeoxygenation process.


Abstract

The hydrodeoxygenation (HDO) reaction provides a promising catalytic strategy to remove oxygen in biomass-derived bio-oil to produce renewable transportation fuels and value-added chemicals. The development of highly efficient and stable HDO catalysts plays an essential role in biomass valorization. Metal-zeolite bifunctional catalysts have been well-developed as the effective HDO catalysts in upgrading lignin-derived phenolics due to their excellent activity, selectivity, and thermal and hydrothermal stability. However, clarifying the roles of the active sites and their synergistic effect, and establishing effective structure-performance relationships in the HDO process still face challenges. In this review, we first survey the conventional catalysts applied in the HDO of bio-oil, followed by thoroughly discussing the roles of metal centers, acid sites, supports, and their impacts on the HDO process of phenolic model compounds or bio-oil. Finally, a discussion on the stability and deactivation of metal-zeolite catalysts, especially in the aqueous-phase HDO reaction, is provided. This critical review offers new insights into the development of state-of-the-art metal-zeolite bifunctional catalysts with well-defined porosity and metal-acid properties for viable biomass valorization.

Hydrogenation of glucose to sorbitol by using nickel hydroxyapatite catalyst

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Hydrogenation of glucose to sorbitol by using nickel hydroxyapatite catalyst

A facile hydrogenation of glucose to sorbitol has been reported with Ni-HAP catalyst using water as a solvent. The excellent yield of sorbitol, 97 % in 1 h is possible due to the high surface area and high acid-base strength of the Ni-HAP-4 catalyst.


Abstract

A series of nickel hydroxyapatite catalysts were synthesized by the co-precipitation method followed by calcination and reduction. These catalysts were employed for the aqueous phase hydrogenation of glucose to sorbitol. The Ni-HAP catalyst with comparatively high surface area and acid-base strength gave high sorbitol selectivity in 1 h. Ni-HAP-4 catalyst with moderate Ni (3.5 wt. %) content having smaller and highly dispersed nickel particles gives an excellent yield of sorbitol, 97 % in 1 h. The Ni-HAP-4 catalyst works well with other polar protic solvents. Different characterization techniques like XRD, TEM, SEM-EDS, BET, NH3-TPD, and CO2-TPD were employed to analyze the Ni-HAP-4 catalyst.

A Distibene with Extremely Long Sb=Sb Distance and Related Heavier Dipnictenes from Salt‐Free Metathesis Reactions

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A Distibene with Extremely Long Sb=Sb Distance and Related Heavier Dipnictenes from Salt-Free Metathesis Reactions

The Cover Feature shows construction machinery actively engaged in a distibene project. The picture refers to a compound bearing the highly encumbered Ar* ligand (Ar* = C6H2−2,6-(CHPh2)2−4-iPr), which was isolated from salt-free metathesis reactions – alongside other novel dipnictenes – during this study. The distibene shown at the construction site protrudes from other compounds of this class, as it exhibits the currently longest Sb=Sb distance [2.8605(5) Å] of all thus far reported distibenes. “Construction” of dipnictenes with elongated bonds between the heavier atoms is currently of great interest in the research community, as such compounds are promising candidates for the application in the controlled activation of small molecules. More information can be found in the Research Article by R. C. Fischer and co-workers.


Isolable Dipyrromethene‐Based Heavier Group 14 and 15 Element Complexes

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Isolable Dipyrromethene-Based Heavier Group 14 and 15 Element Complexes

The air-stable dipyrromethene-based tin complexes (SNDIPYs) 1 and 3 and the first isolable ASDIPY 2, which are direct analogues of BODIPY, have been synthesized and fully characterized. All of these complexes exhibit green photoluminescence.


Abstract

Boron-dipyrromethenes (BODIPYs) have attracted much attention owing to their unique properties and widespread applications; however, the incorporation of the heavier group 14 and 15 elements in the rigid dipyrromethene ligands remains limited. Herein, the dipyrromethene-based heavier group 14 and 15 element complexes, tin-dipyrromethene (SNDIPY, 1) and arsenic-dipyrromethene (ASDIPY, 2), which are direct analogues of BODIPY, have been facilely synthesized and isolated in moderate yields. Both compounds have been investigated by NMR, UV-vis absorption, photoluminescence spectroscopy, cyclic voltammogram, X-ray crystallography, as well as theoretical studies. Both compounds exhibit green photoluminescence. Notably, SNDIPY 1 is air-stable and compound 2 represents the first isolable and structurally characterized ASDIPY.

Pivotal Role of Salicylates in Tuning the Formation and Reactivity of Mn(V)=O’s

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Pivotal Role of Salicylates in Tuning the Formation and Reactivity of Mn(V)=O's

Salicylates influencing High valent MnV=O at room temperature: This work provides an alternate path to generate transient reactive MnV=O species under stoichiometric conditions. The studies involved highlight the pivotal role of bound 5-X-salicylate moieties on the MnV=O species exhibiting a significant effect on its electrophilicity. Besides, the employed complexes are potent to prevent the proliferation of cancer cells effectively and are mapped to the oxidative mechanism of action.


Abstract

An alternative and efficient route has been derived to generate the high valent [Mn(V)=O(m-Cl-salicylate)]+ intermediates with a series of non-heme neutral ligand frameworks at 20 °C. The current method provides an advantage with feasibility in maintaining stoichiometric oxidant ratios along with the crucial variations of the salicylate moieties in tuning the reactivity of Mn(V)=O species. An in-depth analysis of the Hammett studies revealed that the bound 5-X-salicylate (X=Cl, and NO2) drastically alters the corresponding Mn(V)=O's reactivity rates. In contrast, variations in the parent ligand frameworks resulted in consistent ρ values with increased lifetimes depicting the ligand's role in stabilization. Lastly, the complexes have been characterized to promote oxidative stress and prevent the proliferation of cancer cells effectively.

Metal Oxides Derived from Perovskite or Spinel for the Selective Hydrogenation of α,β‐Unsaturated Aldehydes: A Mini–Review

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Metal Oxides Derived from Perovskite or Spinel for the Selective Hydrogenation of α,β-Unsaturated Aldehydes: A Mini–Review

Recent developments in the liquid–phase selective hydrogenation of α,β-unsaturated aldehydes, with metal oxides derived from perovskite or spinel as supports or catalyst precursors, were summarized. Spatial isolation of A-site ions with B-site ions makes these ions highly dispersed and enhances the intimate contact with the active components supported on them, leading to electron transfer or synergistic effect to promote the catalytic ability.


Abstract

Mixed metal oxides with perovskite ABO3 or spinel AB2O4 structure can provide uniformly and highly dispersed metal oxides, which can be adopted as catalyst supports, as catalysts directly or as catalysts after reduction. When they are used as catalyst supports, the spatial isolation of A-site ions with B-site ions not only makes these ions highly dispersed, but also enhances the intimate contact with the active components supported on them, leading to electron transfer or synergistic effect to promote the catalytic ability. After reduction, highly dispersed A/B nanoparticles supported on BOx/AOx can be achieved for the relevant applications. Herein, recent developments in the liquid–phase selective hydrogenation of α,β-unsaturated aldehydes, with metal oxides derived from perovskite or spinel as supports or catalyst precursors, were summarized.

Enhancing Ammonia Synthesis on Co3Mo3N via Metal Support Interactions on a Single‐crystalline MgO Support

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Enhancing Ammonia Synthesis on Co3Mo3N via Metal Support Interactions on a Single-crystalline MgO Support

The study examines Co3Mo3N catalysts on two MgO substrates, revealing MgO preparation‘s impact on surface basicity. Remarkably, Co3Mo3N on single-crystalline MgO exhibits a superior rate of 162.0 mmol g−1 metal h−1, surpassing commercial MgO support (41.2 mmol g−1 metal h−1) and unsupported Co3Mo3N (15.0 mmol g−1 metal h−1).


Abstract

Co3Mo3N has been reported to have activity for the synthesis of ammonia surpassing that of industrial Fe catalysts under certain conditions. However, so far the research has largely focused on unsupported Co3Mo3N. We report a comprehensive study on the catalytic activity of Co3Mo3N when supported on two distinct MgO substrates. Our findings reveal that the method of MgO preparation plays a crucial role in influencing surface basicity. Remarkably, Co3Mo3N supported on single-crystalline MgO demonstrates significantly enhanced catalytic activity, achieving a 162.0 mmol g−1 metal h−1 rate. This surpasses the performance on commercial MgO support (41.2 mmol g−1 metal h−1) and unsupported Co3Mo3N (15.0 mmol g−1 metal h−1). While kinetic analyses show no substantial differences between the two supported catalysts, spectroscopic studies employing CO2 and N2 temperature-programmed desorption (TPD) reveal a richer array of basic sites and adsorption/desorption phenomena on the single-crystalline MgO support. These catalysts exhibit exceptional stability. The drastically reduced Co/Mo loading amounts in comparison to the bulk form, make the commercialization of Co3Mo3N catalysts more practical.