TBA−Br and Selectfluor Mediated Bromination of Glycals and Heterocyclic Compounds: Substrate Scope and Synthetic Utility

Posted on 11 October 2023 by nMittali Maheshwari, nNazar Hussainn

The metal-free stereoselective procedure is developed by using selectfluor and TBAB as a reagent system for the dibromination of sugar enol-ethers and monobromination of heterocyclic compounds. This protocol attained dibrominated product with glycals in 5 minutes at room temperature with excellent yields. For substituted indoles and chromones, same reagent system delivered the 3-brominated products but at elevated temperatures. Further, the synthetic utility was shown by synthesizing 3-aryl indoles and isoflavones via Suzuki-Miyura cross-coupling reactions.

Abstract

Herein, we have devised a metal-free stereoselective protocol mediated by selectfluor for the dibromination of sugar enol-ethers and monobromination of heterocyclic compounds. The dibromination of glycals was achieved within 5 minutes at room temperature with excellent yields. The tolerance of various protecting groups such as acetyl, benzyl, and silyl in sugars was checked. When the same reagent system was applied to substituted indoles and chromones 3-brominated products were obtained but at elevated temperatures. The synthetic utility of the methodology was demonstrated by using the brominated indoles and chromones to synthesize the 3-aryl indoles and isoflavones respectively via Suzuki-Miyura cross-coupling reactions.

Recent Progress, Challenges, and Future Prospects in Solar H2 Evolution via Pure/Sea Water Splitting Using Nanocomposites as Photocatalysts under Solar Light

Posted on 11 October 2023 by nPrakash Jakhar, nShaily Sharma, nSurbhi Dhadda, nHimanshu Sharman

This review summarizes a study on photocatalytic solar-driven water splitting, specifically comparing pure and sea water systems for hydrogen (H₂) generation. Sea water shows superior H₂ production under solar light due to cost-effectiveness and ample availability. However, challenges persist in fully harnessing natural light, often necessitating co-catalysts and sacrificial agents to boost efficiency.

Abstract

Photocatalytic pure/sea water splitting driven by solar light, emerges as the most promising strategy to address both the global energy crisis and environmental degradation. Research efforts have mainly resulted in the development of artificial photocatalytic solar hydrogen generation systems applicable to both freshwater and sea water. During long-term testing, sea water demonstrated enhanced stability compared to pure water, offering experimental advantages in designing novel techniques aimed at reducing hydrogen generation costs, alleviating freshwater scarcity, and optimizing the utilization of natural water resources. Moreover, sea water splitting proves to be more effective in producing solar hydrogen due to the potential sacrificial action of salt ions, which promote hydrogen evolution within the photocatalytic system. This review comprehensively outlines the fundamental principles of photocatalytic H₂ production, examines the efficiencies and recent progress in hydrogen generation, explores the challenges faced, and envisions the future prospects of enhancing hydrogen production efficiency and reactivity through photocatalytic pure/sea water splitting.

Iron ions embedded in hexagonal mesoporous silica via a simple method: implementation in mild oxidation catalysis

Posted on 11 October 2023 by

Mesoporous silica monoliths containing dispersed Fe^III sites have been prepared using a simple and cheap synthetic procedure. These materials are efficient as epoxidation catalysts by hydrogen peroxide under mild conditions. The textural and spectroscopic analyses of these materials reveal that the catalytic activity results from a compromise between several parameters such as the pore diameter and the hydophobicity of the silica walls.

Abstract

Mesoporous silica monoliths containing dispersed Fe^III sites have been prepared following a direct and simple synthetic method. The iron-containing materials are able to catalyze the epoxidation of cyclooctene by H₂O₂ under mild conditions. Textural and spectrophotometric analyses reveal that, when the thermal treatment temperature of the materials increases (from 500 °C to 1000 °C), the pore diameter of the silica matrix decreases while the formation of small oxo-iron(III) clusters is promoted. Among the five materials obtained after treatment at 500, 700, 800, 900 or 1000 °C, the one prepared at 700 °C exhibits the best catalytic performances. This indicates that a compromise must be found between several parameters, such as the pore size (which decreases with calcination temperature) and the hydrophobicity of the channel surface (which is favored at higher temperature), for an optimal reactivity.

A Facile and Fast Syntheeis of Barium Molybdate Nanoparticles: Effects of PH and Surfactant

Posted on 11 October 2023 by nAdem Sarılmazn

BaMoO₄s with nano-sized and homogeneous particle distribution were obtained at low reaction temperatures and time. Also, the effects of pH values and surfactant types on the morphologies of particles were investigated. In addition, the properties of BaMoO₄ particles obtained by the co-precipitate method were characterized using various analysis methods.

Abstract

Barium molybdate (BaMoO₄) is one of the materials used extensively in electronic and optical devices. Although there are many synthesis methods in the literature, a route for facile synthesis of nano-BaMoO₄ has been ignored. In this study, BaMoO₄ nanoparticles were produced by the co-precipitation method at room temperature within a short time. The effects of ammonia solutions and surfactants on the morphology of the particles were investigated. Various properties of these materials were characterized by XRD, SEM-EDX, elemental mapping, TEM, and UV-Vis analysis methods. Also, the crystal structure parameters and the compatibility of these values with the theoretical calculations were determined by Rietveld refinement. From the HR-TEM image, the interplanar spacing was calculated as 3.2 Å. It was determined from these analyses that BaMoO₄ particles with optical band gaps varying between 3.80 and 3.95 eV were produced in nano and micrometer sizes. It has been demonstrated by this study that the pH of the synthesis solution and the type of surfactant have significant effects on the morphological and optical properties of the materials.

The Effect of Different Morphologies of Polyaniline on Its Catalytic Activity for the Thermal Decomposition of Ammonium Perchlorate

Posted on 11 October 2023 by

NP-PANi was synthesized by three different methods comprising: chemical, sonochemical, and electrochemical routes. The synthesized polymers were deeply characterized using FTIR, N₂ adsorption-desorption, FESEM, and EDAX analysis. From BET results, electro-PANi has the highest surface area, highest pore volume, and the smallest pore size among others and, as expected revealed the best catalytic activity. It merged two peaks of AP decomposition into a drastically solo sharp peak revealed at low temperature (approximately 90 °C lower than) and increased the enthalpy of the reaction significantly by about 140 %.

Abstract

In this study, a novel strong green catalyst as a promising replacement for conventional transition metal oxides (TMOs) based burning rate modifiers was introduced. For this aim, the morphology of the nano-porous polyaniline (NP-PANi) was manipulated by changing its synthesis method, and the effect of that on the activity of the catalyst on the thermal decomposition of ammonium perchlorate (AP) was investigated. To achieve this goal, NP-PANi was synthesized by three different methods comprising: chemical, sonochemical, and electrochemical routes. The synthesized polymers were deeply characterized using FTIR, N₂ adsorption-desorption, FESEM, and EDAX analysis. From BET results, electro-PANi has the highest surface area, highest pore volume, and the smallest pore size among others and, as expected revealed the best catalytic activity. It merged two peaks of AP decomposition into a drastically solo sharp peak revealed at low temperature (approximately 90 °C lower than) and increased the enthalpy of the reaction significantly by about 140 %. The obtained results can open a new window in the world of practical green burning rate modifiers for the energetic material industry.

Preparation of an Activated Carbon Composite with High Thermal Conductivity Based on Emulsified Asphalt and Carbon Nanotubes and its Adsorption Performance for n‐Hexane

Posted on 11 October 2023 by

The preparation process of composite activated carbon is mainly from stirring, then high temperature sintering to carbon, followed by a large amount of water washing to remove impurities, and finally drying to obtain composite activated carbon. During the high temperature sintering, asphalt is carbonized to form fluffy carbon material, which increases a lot of space for the loading of CNTs.

Abstract

Activated carbon, as the main adsorption material for treating VOCs, has been widely used. To solve the problem of safety hazards in activated carbon adsorption process due to the large amount of heat released, highly thermally conductive composite activated carbon (A-AC/CNTs) was prepared using asphalt and highly thermally conductive carbon nanotubes (CNTs) for thermal conductivity improvement. Uniform dispersion and firm loading of CNTs in the carbon production material were achieved by dispersing carbon nanotubes (CNTs) in the asphalt-in-water emulsion. Experimental results showed that the specific surface area of A-AC/CNTs reached a maximum when the loading of CNTs was 0.5 wt %. Meanwhile, the thermal conductivity increased by 1.5 times compared with the original activated carbon. The adsorption capacity of n-hexane reached the maximum of 2868 mmol ⋅ g⁻¹, and the adsorption capacity increased by 21.41 %. It also maintained good regeneration performance after dynamic adsorption experiments.

Facile Synthesis of Citric Acid Functionalized Fe3O4@Activated Carbon Magnetic Nanocomposite for Efficient Adsorption of Brilliant Green Dye from Wastewater

Posted on 11 October 2023 by

Surface of Citric acid functionalized Fe₃O₄/Activated Carbon behaves as cationic and anionic depending on its point zero charge (pH~8), which lead to various adsorbent-dye interactions. Brilliant green dye shows superior adsorption behaviour near neutral condition as depicted from the plot of dye removal percentage as a function of contact time owing to the surface interactions such as electrostatic interactions and hydrogen bonding.

Abstract

Owing to the impact of brilliant green dye on potable water contamination, citric acid functionalized magnetic nanocomposite in presence of activated carbon was prepared for easy, quick, and efficient removal of the dye from water. Batch adsorption studies were conducted to maximize the adsorption efficiency by optimizing contact time, initial dye concentration, pH, dosage, and salt concentration. The maximum efficiency of the citric acid functionalized Fe₃O₄@activated carbon was found to be 773 mg g⁻¹. The efficiency of the monolayer adsorption process as depicted from the Langmuir model is explained based on the hydrogen bonding, electrostatic interaction, and porosity of the adsorbent. The adsorption process follows a pseudo-second order kinetics model which can also be correlated to the relatively quick adsorption process. The saturation magnetization of the nanocomposites prepared in presence of activated carbon was found to be 35.2 emu/g, which makes it effective for quick magnetic separation. Built on the findings, we report an economical, efficient, and satisfactory alternative adsorbent for the abatement of brilliant green dye from coloured wastewater and contaminated water sources.

3D‐Printed TiO2 Electrode as a Viable Alternative for Photoelectrocatalytic Purification of Water

Posted on 11 October 2023 by

Ti-TiO₂ nanotube photoelectrodes manufactured via sintering of commercial pure titanium powder (cp-Ti), followed by anodization, has equivalent characteristics and photoelectrocataytic performance for treatment of organic compounds compared to photoelectrode produced from commercial titanium foil. Using the 3D-printed electrode, the photoelectrocatalysis has showed as a viable advanced oxidation alternative for the treatment of Benzothiazole. Results allow exploration of innovative electrode designs.

Abstract

A commercial pure titanium (cp-Ti) powder was used to produce a photoelectrode substrate via 3D-printing and a commercial titanium foil (Ti-foil) was used as substrate for direct comparison. TiO₂ nanotubes were prepared on both Ti substrates via electrochemical anodization. Characterisation of electrodes showed similar results in all aspects analysed: morphology, absorbance, crystallinity, and photo-current response. The efficiency of photoelectrocatlytic treatment of methylene blue dye (MB) in water with a single-chip UVA-LED was identical. The cp-Ti/TiO₂ electrode achieved 93±4 % removal of MB after 210 min, when combined with a four-chip UVA-LED. The cp-Ti photoelectrode was also tested for the first time for photoelectrocatalytic treatment of benzothiazole (BTH). The highest degradation of BTH (98±2 %, 120 min) was also achieved using the four-chip UVA-LED. This study supports further development of 3D-printed electrodes, maximizing the potential for the creation of novel electrodes for use in PEC technologies for abatement of organic pollutants.

Synthesis of Novel Polycyclic Alkylated Tetralin Base Oils Catalyzed by Ionic Liquids and Its Lubricating Properties

Posted on 11 October 2023 by

At low temperatures, an efficient synthesis of polycyclic alkylated compounds by tetralin and 1,7-octadiene using Et₃NHCl−AlCl₃ ionic liquid has been developed. The polycyclic alkylated tetralin with high viscosity has excellent tribological properties, which provides a new route for the production of high viscosity lubricating base oils from coal-based feedstocks.

Abstract

A novel polycyclic alkylated tetralin (PAT) similar to the naphthenic oil was successfully synthesized through Friedel-Crafts alkylation. This was accomplished by reacting coal-based chemical tetralin with 1,7-octadiene, using Et₃NHCl−AlCl₃ ionic liquid as a catalyst. To enhance the selectivity towards dialkylated products (C28−2THN), the reaction conditions were systematically studied. Interestingly, the reaction could proceed well even at a low temperature of 0 °C and the selectivity for C28−2THN products could reach 54.0 %. The primary physicochemical properties of PAT were investigated in detail, it was found that the existence of polycyclic structures contributes to high viscosity, better thermal-oxidative stability and good polarity. Compared with octyltetralins- and commercial alkylnaphthalene-based oil (AN30), the PAT exhibited superior friction-reducing and anti-wear properties under the load of 100 N at 50 °C due to its rigid cycle structures and flexible chain.

Selective Electrophoretic Deposition of Silicon Nanoparticles onto PAN‐Based Carbon Fiber as a Prospective Anode for Structural Li‐Ion Batteries

Posted on 11 October 2023 by

New class of batteries is needed as the traditional ones are heavyweight, limiting their applications in some areas. Structural battery can be a solution as it provides both mechanical and electrochemical functions simultaneously. This work presents the potential of silicon-modified PAN-based carbon fiber as prospective anode for structural Li-ion batteries, which was obtained via facile and cheap electrophoretic deposition method.

Abstract

The demand for revolutionizing the lightweight design of Li-ion batteries has become inevitable due to the ever-increasing development of electric transportation modes. Integration of structural and energy storage functionalities into a single structural battery device can be a smart way to improve the overall performance of electric vehicles. In this study, we propose a facile and cost-effective approach to develop a prospective anode for structural Li-ion batteries through electrophoretic deposition of silicon (Si) particles onto polyacrylonitrile (PAN)-based carbon fiber. The synthesis method is able to selectively deposit small-sized silicon particles on the surface of carbon fiber, producing a thin, continuous, and porous coating of silicon nanoparticles on commercial PAN-based carbon fiber. The synthesized Si/PAN-based carbon fiber electrode exhibits remarkable mechanical properties, delivering a tensile strength of 2.57 GPa and a tensile modulus of 118.2 GPa. Benefitting from the morphology of the deposited silicon, the discharge capacity of silicon/PAN-based carbon fiber anode can reach 565 mAh g⁻¹ with 81 % capacity retention after 50 cycles. This work highlights the potential of silicon-modified carbon fiber electrodes obtained via a simple and cost-effective deposition method for structural Li-ion battery applications.