Magnetically separable γ-Fe2O3 nanoparticles: An efficient catalyst for acylation of alcohols, phenols, and amines using sonication energy under solvent free condition

Modified nano magnetic Fe2O3-MgO as a high active multifunctional heterogeneous catalyst for environmentally beneficial carbon-carbon synthesis

In this study, novel nanomagnetic catalysts, namely Fe2O3-MgO@choline formate (Ch. F.) and Fe2O3-MgO@choline cyanide (Ch. CN), were synthesized through immobilizing choline-based ion liquids to magnetic support via a simple and cost-effective methodology. FT-IR, TGA, FE-SEM, VSM, EDS, BET, and XRD techniques were employed to assess and characterize these organic-inorganic compounds. Following the successful preparation of nanoparticles, the catalysts were utilized in Knoevenagel and benzoin condensations. Fe2O3-MgO@Ch.F. exhibited exceptional activity in Knoevenagel condensation under solvent-free conditions at room temperature, achieving high yields (91-98%) in a short timeframe. Similarly, Fe2O3-MgO@Ch.CN demonstrated remarkable activity in benzoin condensation under environmentally friendly solvent conditions, yielding higher isolated yields (76-88%). Furthermore, these magnetically recyclable multifunctional catalysts displayed the ability to be reused up to five times without a significant loss in efficiency. Additionally, the heterogeneity of this nanocatalyst was investigated using the hot filtration technique. The findings indicated that the reaction primarily occurs via a heterogeneous pathway.

Singlet oxygen dominance for phenolic degradation mediated by mixed-valence FeOx nanospheres

In this investigation, we successfully synthesized magnetic FeOx nanosphere catalysts with mixed-valence and high operational stability through the pyrolysis of a hybrid material containing polyferrocenlyphosphazene with coordinating heteroatoms (N, P, O). We evaluated the degradation performance of these catalysts using the peroxymonosulfate (PMS) activation process against four different phenolic compounds, namely phenol, 4-nitrophenol, 2,4-dinitrophenol, and 2,4,5-trinitrophenol. Our results demonstrate the significant role of FeOx in the degradation process. The presence of mixed iron species, such as ferric iron, zero-valent iron, and iron oxides, activated PMS to generate radicals. Additionally, the heteroatoms facilitated the anchoring and dispersion of FeOx nanospheres while also breaking the inertness of the carbon structure. Notably, the FeOx-800 catalyst exhibited a maximum degradation activity of 98% for phenol, surpassing its counterparts. Electron paramagnetic resonance and free radical scavenging experiments confirmed that singlet oxygen (1O2) is the principal reactive oxygen species (ROS) that leads to the oxidative breakdown of phenolic compounds. This study introduces new concepts for designing Fenton-like catalysts incorporating heteroatoms into the carbon matrix. Due to their low cost and non-toxicity, these catalysts have recently received a great deal of attention for peroxymonosulfate (PMS) activation and environmental remediation.

Structural and optical properties of silver supported α-Fe2O3 nanocomposite fabricated by Saraca asoca leaf extract for the effective photo-degradation of cationic dye Azure B

In recent decades, several nanocomposites developed by chemical synthetic routes, have been demonstrated as efficient photocatalysts for the photodegradation of hazardous organic dyes. The present investigation reports the sonochemical-assisted fabrication of silver-supported α-Fe2O3 nanocomposites (SA@Ag@IONCs) using the Saraca asoca leaf extract. The magnetic nanocomposites can be easily removed from the reaction mixture. The morphology of these materials was characterized by field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), XPS, BET surface area analyzer, UV-visible spectroscopy, photoluminescence, X-ray diffraction (XRD), and VSM techniques. The XRD and electron microscopy analyses revealed the small size and well-crystalline SA@Ag@IONC particles with spherical and buckyball structures. The large surface area of SA@Ag@IONCs was confirmed by BET analysis. The absorption edge in UV-visible spectra appeared to migrate towards high wavelengths for the SA@Ag@IONC composite, causing a change in the bandgap energy. In the case of the sonication assisted composite, the bandgap energy was 2.1 eV, making it easier for the electron to transfer from the valence band to conduction band. The decoration of ultrasmall silver onto the surfaces of the α-Fe2O3 nanocomposite, which considerably increases the capacity to absorb sunlight, enhances the efficiency of charge carrier separation, and inhibits the electron-hole recombination rate as confirmed by the reduced PL intensity, is responsible for the excellent photocatalytic degradation performance. Outcomes shown SA@Ag@IONCs have a high photodegradation rate as well as high-rate constant value at an optimized condition that is at pH 9 and 0.5 g L-1 dose of nanocomposite, photodegradation rate of Azure B is ∼94%. Trap experiment results indicated that O2˙- and h+ are the active species responsible for the photodegradation of AzB.

Synthesis and characterization of silica gel from Lapindo volcanic mud with ethanol as a cosolvent for desiccant applications

Lapindo mud (LM) is a volcanic mud from a natural disaster that occurred 16 years ago in Sidoarjo District, East Java, Indonesia. The high amount of silica in the local materials of LM has been extracted for silica gel synthesis via hydrometallurgy methods, followed by sol-gel methods. The presence of ethanol in the synthesis process generated a unique textural property at different ratios between ethanol and sodium silicate (e/ss). Sol-gel mediated silica gel synthesis exhibited mesoporous properties with an amorphous structure, which is a characteristic of the silica gel. The silica gel exhibits silica nanoparticles over the average diameter of 2.08 nm with a spherical morphology and is connected to form an agglomeration structure. Increasing the e/ss ratio enhanced the amount of the hydroxyl group and the specific surface area ranged from 57 to 103 m² g^-1. The moisture adsorption performance of each silica gel showed that the silica gel with an e/ss ratio of 5 : 5 exhibited the highest adsorption capacity measured by conventional gravimetric methods and thermogravimetric analysis of 10.56% and 11.20% g_water g_silica ^-1, respectively. These results indicated that the silica gel with an e/ss ratio has a high number of hydroxyl groups and more surface-active sites, which is beneficial for the adsorption process. The adsorption capacity of the synthesized silica gel is also higher than that of the commercial silica gel, indicating an excellent performance for desiccant applications.

Fe(III)-Rhamnoxylan-A Novel High Spin Fe(III) Octahedral Complex Having Versatile Physical and Biological Properties

An iron (III) complex with rhamnoxylan, a hemicellulose from Salvia plebeia seeds, was synthesized and characterized by elemental analysis, spectroscopic and magnetic susceptibility measurements, thermal analysis and scanning electron microscopy. The rhamnoxylan was found to be a branched hemicellulose consisting of β-1,4-linked xylose main chain and rhamnose attached to the chain at β-1,3 positions. The complex was found to contain 18.8% w/w iron. A high-spin octahedral geometry of Fe3+ was indicated by the electronic absorption spectrum of the complex. In other experiments, the complex exhibited good electrical and magnetic properties. In vivo efficacy, as hematinic, of the complex in induced anemia was demonstrated equivalent to that of iron protein succinylate (taken as standard) as evidenced by raised red blood cell count, hemoglobin, hematocrit and total iron in rabbit. The complex was found to be non-toxic with LD50 > 5000 mg kg−1 body weight in rabbit. Thus, iron(III)-rhamnoxylan hold the potential for application as hematinic for treatment of iron deficiency anemia.

Crystal Plane Impact of ZnFe2O4-Ag Nanoparticles Influencing Photocatalytical and Antibacterial Properties: Experimental and Theoretical Studies

This paper describes the crystal interphase impact of ZnFe₂O₄-Ag in the photodegradation of Rhodamine B. Prepared ZnFe₂O₄ nanoparticles (NPs) were deposited with Ag NPs to offer ZnFe₂O₄-Ag (0-2.5%). An X-ray diffraction peak corresponding to the Ag NPs was detected if the particle content reached about 2.0%, observing multiple crystalline interphases in HR-TEM. Magnetic saturation (Ms) was increased ∼160% times for ZnFe₂O₄-Ag (7.25 to 18.71 emu/g) and ZnFe₂O₄ (9.62 to 25.09 emu/g) if the temperature is lowered from 298 to 5.0 K; while for Fe₃O₄ (91.09 to 96.19 emu/g), the Ms increment was just about 5.6%. After analyzing the DFT-Density of State, a decrease of bandgap energy for ZnFe₂O₄-Ag₆ from the influence of the size of Ag cluster was seen. Quantum yield (Φ) was 0.60 for ZnFe₂O₄, 0.25 for ZnFe₂O₄-Ag (1.0%), 0.70 for ZnFe₂O₄-Ag (1.5%), 0.66 for ZnFe₂O₄-Ag (2.0%), and 0.66 for ZnFe₂O₄-Ag (2.5%), showing that the disposition of Ag NPs (1.5-2.5%) increases the Φ to >0.60. The samples were used to photo-oxidize RhB under visible light assisted by photopowered Langmuir adsorption. The degradation follows first-order kinetics (k = 5.5 × 10^-3 min^-1), resulting in a greater k = 2.0 × 10^-3 min^-1 for ZnFe₂O₄-Ag than for ZnFe₂O₄ (or Fe₃O₄, k = 1.1 × 10^-3 min^-1). DFT-total energy was used to analyze the intermediates formed from the RhB oxidation. Finally, the ZnFe₂O₄-Ag exhibits good antibacterial behavior because of the presence of Zn and the Ag components.

Metal-Organic Polymer-Derived Interconnected Fe-Ni Alloy by Carbon Nanotubes as an Advanced Design of Urea Oxidation Catalysts

The electrochemical urea oxidation reaction (UOR) is considered as a promising renewable source for harvesting energy from waste. We report a new synthetic design approach to produce an iron-nickel alloy nanocatalyst from a metal-organic polymer (MOP) by a single-step carbonization process at 500 °C, thus forming a core-shell of iron-nickel-coated carbon (C@FeNi) nanostructures wired by embedded carbon nanotubes (CNTs) (CNT/C@FeNi). Powder X-ray diffraction confirmed the formation of metallic FeNi₃ alloy nanoparticles (∼20 to 28 nm). Our experimental results showed that MOP containing CNTs acquired an interconnected hierarchical topology, which prevented the collapse of its microstructure during pyrolysis. Hence, CNT/C@FeNi shows higher porosity (10 times) than C@FeNi. The electrochemical UOR in alkaline electrolytes on these catalysts was studied using cyclic voltammetry (CV). The result showed a higher anodic current (3.5 mA cm^-2) for CNT/C@FeNi than for C@FeNi (1.1 mA cm^-2) at 1.5 V/RHE. CNT/C@FeNi displayed good stability in chronoamperometry experiments and a lower Tafel slope (33 mV dec^-1) than C@FeNi (41.1 mV dec^-1). In this study, CNT/C@FeNi exhibits higher exchange current density (3.2 μA cm^-2) than does C@FeNi (2 μA cm^-2). The reaction rate orders of CNT/C@FeNi and C@FeNi at a kinetically controlled potential of 1.4 V/RHE were 0.5 and 0.9, respectively, higher than the 0.26 of β-Ni(OH)₂, Ni/Ni(OH)₂ electrodes. The electrochemical impedance result showed a lower charge-transfer resistance for CNT/C@FeNi (61 Ω·cm^-2) than for C@FeNi (162 Ω·cm^-2), due to faster oxidation kinetics associated with the CNT linkage. Moreover, CNT/C@FeNi exhibited a lower Tafel slope and resistance and higher heterogeneity (25.2 × 10^-5 cm s^-1), as well as relatively high faradic efficiency (68.4%) compared to C@FeNi (56%). Thus, the carbon-coated FeNi₃ core connected by CNT facilitates lower charge-transfer resistance and reduces the UOR overpotential.

Rust-derived Fe2O3 nanoparticles as a green catalyst for the one-pot synthesis of hydrazinyl thiazole derivatives

A novel route of one-pot multicomponent reaction of tosylates, aryl aldehydes and thiosemicarbazide for the synthesis of hydrazinyl thiazole is reported using Fe₂O₃ NPs derived from rust iron as a catalyst.

Green synthesis and characterization of novel 1,2,4,5-tetrasubstituted imidazole derivatives with eco-friendly red brick clay as efficacious catalyst

Use of cheaper and recyclable materials contributes positively to economic growth with environmental sustainability. We report the prospect of utilizing red brick clay as catalyst, which exhibited excellent activity in rapid one-pot four-component condensation of 1,2,4,5-tetrasubstituted imidazoles with high conversion and yields (91-96%) in aqueous medium at 60 °C in short reaction times (25-40 min). The red brick clay material was fully characterized by XRD, FT-IR, SEM, TEM, EDX and BET analyses. Red brick clay consisted of oxides of Si (20.38%), Fe (19.55%), Al (14.30%) and minor amounts of Ca (3.60%) and Mg (1.68%). The slate-like-shaped structure morphology and flaky appearance of inexpensive solid clay material proved competent material for the synthesis of 15 novel 1,2,4,5-tetrasubstituted imidazole derivatives. In addition, the advantages of the eco-friendly method are non-toxicity and re-usability of the catalyst. Reaction offers 78% atom economy and 84% carbon capture.

Acetylation of Alcohols, Amines, Phenols, Thiols under Catalyst and Solvent-Free Conditions

In the present study, an easy and an efficient approach is reported for the acetylation of alcohols, amines, phenols, and thiols under solvent- and catalyst-free conditions. The experimental conditions were milder than conventional methods and the reactions were completed in shorter reaction time. The examined substrates afforded higher yields of the acetylated products under the short reaction time. Comparison of this work with earlier reported procedures reveals that this method offers some advantages than with reported catalysts and solvents. The as-synthesized products were characterized by 1H-NMR and GC-MS techniques to ensure their purity and identity. In addition, a possible mechanism was also proposed for this reaction.

Crystal phase induced band gap energy enhancing the photo-catalytic properties of Zn–Fe2O4/Au NPs: experimental and theoretical studies

Au NPs on ZnFe₂O₄ enhances visible absorption, employed for paracetamol oxidation, where peaks were resolved by 2D HPLC.

Photocatalytic degradation of industrial pulp and paper mill effluent using synthesized magnetic Fe2O3-TiO2: Treatment efficiency and characterizations of reused photocatalyst

In this work, heterogeneous photocatalysis was used to treat pulp and paper mill effluent (PPME). Magnetically retrievable Fe₂O₃-TiO₂ was fabricated by employing a solvent-free mechanochemical process under ambient conditions. Findings elucidated the successful incorporation of Fe₂O₃ into the TiO₂ lattice. Fe₂O₃-TiO₂ was found to be an irregular and slightly agglomerated surface morphology. In comparison to commercial P25, Fe₂O₃-TiO₂ exhibited higher ferromagnetism and better catalyst properties with improvements in surface area (58.40 m²/g), pore volume (0.29 cm³/g), pore size (18.52 nm), and band gap (2.95 eV). Besides, reusability study revealed that Fe₂O₃-TiO₂ was chemically stable and could be reused successively (five cycles) without significant changes in its photoactivity and intrinsic properties. Additionally, this study demonstrated the potential recovery of Fe₂O₃-TiO₂ from an aqueous suspension by using an applied magnetic field or sedimentation. Interactive effects of photocatalytic conditions (initial effluent pH, Fe₂O₃-TiO₂ dosage, and air flow-rate), reaction mechanism, and the presence of chemical oxidants (H₂O₂, BrO₃^-, and HOCl) during the treatment process of PPME were also investigated. Under optimal conditions (initial effluent pH = 3.88, [Fe₂O₃-TiO₂] = 1.3 g/L, and air flow-rate = 2.28 L/min), the treatment efficiency of Fe₂O₃-TiO₂ was 98.5% higher than the P25. Based on Langmuir-Hinshelwood kinetic model, apparent rate constants of Fe₂O₃-TiO₂ and P25 were 9.2 × 10^-3 and 2.7 × 10^-3 min^-1, respectively. The present study revealed not only the potential of using magnetic Fe₂O₃-TiO₂ in PPME treatment but also demonstrated high reusability and easy separation of Fe₂O₃-TiO₂ from the wastewater.