Fe3O4/CuO/Chitosan Nanocomposites: An Ultrasound-Assisted Green Approach for Antibacterial and Photocatalytic Properties

The fundamental goal of this research was to use an environmentally friendly sonochemical method to synthesize a Fe3O4/CuO/chitosan magnetic nanocomposite. The nanocomposites featured particle sizes ranging from 50 to 90 nm, and structural characteristics were thoroughly examined. Moreover, the material displayed selective photodegradation capabilities with MB, achieving an impressive efficiency of nearly 98% within 180 min under specific conditions. Notably, the material's reusability was remarkable, maintaining an efficiency of approximately 88% even after five cycles. The possible photodegradation mechanism was proposed based on the evaluation of energy bands, along with a comprehensive analysis of the impacts on MB photodegradation. Concurrently, adsorption isotherms and kinetic models were evaluated. Additionally, this material exhibited promising antibacterial activity against Saccharomyces cerevisiae, Bacillus subtilis, and Escherichia coli. These findings suggested that the Fe3O4/CuO/chitosan material could be utilized in real-world scenarios for environmental purification due to its ability to function as a photocatalyst and antibacterial agent.

Solid-State Schikorr Reaction from Ferrous Chloride to Magnetite with Hydrogen Evolution as the Kinetic Bottleneck

The selective formation of meta-stable Fe3O4 from ferrous sources by suppressing its oxidative conversion to the most stable hematite (α-Fe2O3) is challenging under oxidative conditions for solid-state synthesis. In this work, we investigated the conversion of iron(II) chloride (FeCl2) to magnetite (Fe3O4) under inert atmosphere in the presence of steam, and the obtained oxides were analyzed by atomic-resolution TEM, 57Fe Mössbauer spectroscopy, and the Verwey transition temperature (Tv). The reaction proceeded in two steps, with H2O as the oxide source in the initial step and as an oxidant in the second step. The initial hydrolysis occurred at temperatures higher than 120 °C to release gaseous HCl, via substituting lattice chloride Cl- with oxide O2-, to give iron oxide intermediates. In the first step, the construction of the intermediate oxides was not topotactic. The second step as a kinetic bottleneck occurred at temperatures higher than 350 °C to generate gaseous H2 through the oxidation of FeII by H+. A substantially large kinetic isotope effect (KIE) was observed for the second step at 500 °C, and this indicates the rate-determining step is the hydrogen evolution. Quantitative analysis of evolved H2 revealed that full conversion of ferrous chloride to magnetite at 500 °C was followed by additional oxidation of the outer sphere of magnetite to give a Fe2O3 phase, as supported by X-ray photoelectron spectroscopy (XPS), and the outer phase confined the conductive magnetite phase within the insulating layers, enabling kinetic control of magnetite synthesis. As such, the reaction stopped at meta-stable magnetite with an excellent saturation magnetization (σs) of 86 emu g-1 and Tv > 120 K without affording the thermodynamically stable α-Fe2O3 as the major final product. The study also discusses the influence of parameters such as reaction temperature, initial grain size of FeCl2, the extent of hydration, and partial pressure of H2O.

Chitosan-Based Composite Membranes with Different Biocompatible Metal Oxide Nanoparticles: Physicochemical Properties and Drug-Release Study

Chitosan (CS) composite membranes were prepared using different biocompatible metal oxide nanoparticles (NPs): titanium dioxide (TiO₂); iron oxide (Fe₃O₄); and aluminum oxide (Al₂O₃). For each nanoparticle, the CS-based composite membranes were prepared with two NPs contents in the CS solution, high (H) and low (L) NPs concentrations. To establish both concentrations, the NPs saturation point in the CS polymeric matrix was determined. The influence of NP concentrations on the physicochemical properties of the CS films was assessed. The prepared CS membranes were characterized with different techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and zeta potential. It was found that the addition of NPs in the CS matrix improved both swelling and mechanical properties. Nanocomposite CS membranes could be prepared using Al₂O₃ NPs. Swelling experiments revealed different pH-sensitive mechanisms, which might be beneficial in biomedical applications since solute permeation through CS-based composite membranes could be controlled by adjusting environmental conditions. When aspirin transport (ASA) through the prepared membranes was carried out in different release media, SGF (simulating gastric fluid) and SIF (simulating intestinal fluid without enzymes), it was observed that the Fickian diffusion coefficient (D) was conditioned by the pH of the release solution. In SGIT (simulating gastrointestinal transit) medium, a transition time (t_trans) was detected due to the shrinkage of the CS polymeric chains, and the drug release depended not only on the Fickian's diffusion but also on the shrinkage of the biopolymer, obeying Peppas and Sahlin equation.

Rapid and selective magnetic separation of uranium in seawater and groundwater using novel phosphoramidate functionalized citrate-Fe3O4@Ag nanoparticles

One-pot magnetic separation of uranium (U) in seawater and groundwater samples has been made possible by synthesizing phosphoramidate functionalized Ag coated citrate-Fe₃O₄ nanoparticles (NPs). The magnetic saturation value of these functionalized NPs is 27.1 emu g^-1. The synergistic extraction mechanism of U(VI) ion by the surface-modified phosphoramidate and citrate molecules make these NPs highly selective towards U(VI). The adsorption kinetics follows a pseudo-second-order model and the adsorption isotherm fits successfully to the Langmuir adsorption model. The functionalized NPs show quantitative extraction efficiency in the pH range of 6.5-8 with a maximum loading capacity (Q_m) of 108.7 mg g^-1. The equilibration time required by these functionalized NPs to attain the Q_m value is 120 s. The recycling of these NPs can be done up to 5-6 times with 1.0 mol L^-1 of Na₂CO₃ or NH₄OH for quantitative extraction of U(VI). These functionalized NPs show high resilience towards large number of naturally abundant metal ions.