Preparation of Activated Carbon-Reinforced Composite Beads Based on MnO2/MCM-41@Fe3O4 and Calcium Alginate for Efficient Removal of Tetracycline in Aqueous Solutions

Tetracycline (TC) is a common antibiotic; when untreated TC enters the environment, it will cause a negative impact on the human body through the food chain. In the present study, MnO2/MCM-41@Fe3O4 (FeMnMCM) prepared using a hydrothermal and redox method and Camellia oleifera shell-activated carbon (COFAC) prepared through alkali activation were encapsulated using alginate (ALG) and calcium chloride as a cross-linking matrix to give the composite beads COFAC-FeMnMCM-ALG. The resultant COFAC-FeMnMCM-ALG composite beads were then carefully characterized, showing a high immobilization of MnO2/MCM-41@Fe3O4, with porous COFAC as an effective bioadsorbent for enriching the pollutants in the treated samples. These bead catalysts were subsequently applied to the oxidative degradation of TC in a Fenton oxidation system. Several parameters affecting the degradation were investigated, including the H2O2 concentration, catalyst dosage, initial TC concentration, and temperature. A very high catalytic activity towards the degradation of TC was demonstrated. The electron paramagnetic resonance (EPR) and quenching results showed that ·OH and ·O2- were generated in the system, with ·OH as the main radical species. In addition, the COFAC-FeMnMCM-ALG catalyst exhibited excellent recyclability/reusability. We conclude that the as-prepared COFAC-FeMnMCM-ALG composite beads, which integrate MnO2 and Fe3O4 with bioadsorbents, provide a new idea for the design of catalysts for advanced oxidation processes (AOPs) and have great potential in the Fenton oxidation system to degrade toxic pollutants.

Fe3O4@void@C-Schiff-base/Pd yolk-shell nanostructures as an effective and reusable nanocatalyst for Suzuki coupling reaction

This article describes the synthesis of a novel Yolk-Shell structured Magnetic Yolk-Shell Nanomaterials Modified by Functionalized Carbon Shell with Schiff/Palladium Bases (Fe3O4@void@C-Schiff-base/Pd). The designed Fe3O4@void@C-Schiff-base/Pd catalyst was characterized using several techniques such as Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD) and Inductively coupled plasma (ICP). The Fe3O4@void@C-Schiff-base/Pd was used as powerful catalyst for preparation Suzuki reaction in short reaction times and high yield in H2O at 60 °C and presence of potassium carbonate base. This nanocatalyst was magnetically recovered and reused several times with keeping its efficiency.

Magnetic ethylene-based periodic mesoporous organosilica supported palladium: An efficient and recoverable nanocatalyst for Suzuki reaction

In the present study, a novel magnetic ethylene-based periodic mesoporous organosilica supported Pd-Schiff base complex (Fe₃O₄@PMO/SB-Pd) was prepared, characterized and applied as a recoverable nanocatalyst for green synthesis of Suzuki products. Chemical composition, magnetic and thermal behavior, morphology and particle size of Fe₃O₄@PMO/SB-Pd were investigated by using FT-IR, TGA, EDX, VSM, PXRD, TEM and Scanning electron microscopy (SEM) analyses. The Fe₃O₄@PMO/SB-Pd nanocomposite was applied as an efficient nanocatalyst in the Suzuki reaction under ultrasonic conditions giving corresponding products in high yield. Some advantages of this study are simple purification of products, the use of water solvent, easy catalyst separation, short reaction time and high catalyst efficiency and recoverability.

Guanidine functionalized core-shell structured magnetic cobalt-ferrite: an efficient nanocatalyst for sonochemical synthesis of spirooxindoles in water

Core/shell nanoparticles have a wide range of applications in the science of chemistry and biomedicine. The core-shell material can be different and modified by changing the ingredients or the ratio of core to the shell. In this research, a CoFe₂O₄@SiO₂-guanidine nanocomposite was prepared and identified as an efficient catalyst for the one-pot synthesis of spirooxindole derivatives in water under ultrasonic irradiation conditions. The advantages of this method are in its simplicity, saving costs and energy, high yields, short reaction times, environmental friendliness, reusability and easy recovery of the catalyst using an external magnet. The catalyst was characterized by XRD, SEM, TEM, EDX, FT-IR, TGA and VSM techniques.

Improved delivery system for celastrol-loaded magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods: HIF-1α-related apoptotic effects on SMMC-7721 cell

Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods were prepared by a rapid combustion method with α-FeOOH nanorods as precursors. Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods with a saturation magnetization of 33.2 emu·g^-1 were obtained using 30 mL of absolute ethanol at a calcination temperature of 300 °C. Their average length was around 140 nm, and average diameter was about 20 nm. To improve the dispersion characteristics of the Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods in aqueous solution, citric acid and PEG were applied to modify the nanorod surface via the Mitsunobu reaction. The results showed that the hydrodynamic size range of Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol was 250-500 nm, the surface potential was -15 mV, and the saturation magnetization was approximately 23 emu·g^-1. The drug loading capacity of Fe₃O₄/α-Fe₂O₃/CA-PEG was larger than the non-PEG modified version. Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol had slow-release characteristics and was sensitive to changes in pH. Application of a magnetic field significantly promoted the inhibition of SMMC-7721 human liver cancer cell growth after treatment with Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol. Celastrol and Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol increased the production of reactive oxygen species in SMMC-7721 cells and promoted apoptosis and apoptosis-related proteins (p53, Bax, Bcl-2) were also changed. In addition, the expression of hypoxia-inducible factor 1α (HIF-1α) was enhanced. We may conclude that celastrol-loaded magnetic Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods may be applied in the chemotherapy of human cancer with good biocompatibility and delivery.

Ru-Pd Thermoresponsive Nanocatalyst Based on a Poly(ionic liquid) for Highly Efficient and Selectively Catalyzed Suzuki Coupling and Asymmetric Transfer Hydrogenation in the Aqueous Phase

The development of intelligent polymeric materials to precisely control the catalytic sites of heterogeneous catalysts and enable highly efficient catalysis of a cascade reaction is of great significance. Here, the utilization of a polymer ionic liquid (PIL) containing two different anions facilitates the preparation of Ru-Pd catalysts with controllable phase transition temperatures and hydrophilic and hydrophobic surfaces. The combined multifunctionality, synergistic effects, micellar effects, aggregation effects, and temperature responsiveness of the nanocatalyst render it suitable for promoting selectively catalyzed Suzuki coupling and asymmetric transfer hydrogenation in water. Above the lower critical solution temperature (LCST) of the catalyst, it catalyzes only the coupling reaction with a high turnover number (TON) of up to 999.0. Below the LCST, the catalyst catalyzes only the asymmetric transfer hydrogenation with good catalytic activity and enantioselectivity. It is important that the catalyst can be simply and effectively recovered and recycled at least 10 times without significant loss of catalytic activity and enantioselectivity. This study also highlights the superiority of multifunctional heterogeneous catalysts based on PILs, which not only overcome limitations associated with low activity of heterogeneous catalysts but also realize selective reactions according to a temperature change, thereby improving the reactivity and enantioselectivity in multiple organic transformations.

Palladium(ii) complexes of tetradentate donor–acceptor Schiff base ligands: synthesis and spectral, structural, thermal and NLO properties

Structural and NLO behavior of push–pull palladium(ii) complexes of metallocenyl-containing asymmetric Schiff base ligands.