Synthesis of magnetic CuFe2O4 self-assembled hollow nanospheres and its application for degrading methylene blue

Development of a simple polymer-based sensor for detection of the Pirimicarb pesticide

In this study, a sensitive and selective fluorescent chemosensor was developed for the determination of pirimicarb pesticide by adopting the surface molecular imprinting approach. The magnetic molecularly imprinted polymer (MIP) nanocomposite was prepared using pirimicarb as the template molecule, CuFe2O4 nanoparticles, and graphene quantum dots as a fluorophore (MIP-CuFe2O4/GQDs). It was then characterized using X-ray diffraction (XRD) technique, Fourier transforms infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), and transmission electron microscopy (TEM). The response surface methodology (RSM) was also employed to optimize and estimate the effective parameters of pirimicarb adsorption by this polymer. According to the experimental results, the average particle size and imprinting factor (IF) of this polymer are 53.61 nm and 2.48, respectively. Moreover, this polymer has an excellent ability to adsorb pirimicarb with a removal percentage of 99.92 at pH = 7.54, initial pirimicarb concentration = 10.17 mg/L, polymer dosage = 840 mg/L, and contact time = 6.15 min. The detection of pirimicarb was performed by fluorescence spectroscopy at a concentration range of 0-50 mg/L, and a sensitivity of 15.808 a.u/mg and a limit of detection of 1.79 mg/L were obtained. Real samples with RSD less than 2 were measured using this chemosensor. Besides, the proposed chemosensor demonstrated remarkable selectivity by checking some other insecticides with similar and different molecular structures to pirimicarb, such as diazinon, deltamethrin, and chlorpyrifos.

Recent Advances in the Development of Novel Iron–Copper Bimetallic Photo Fenton Catalysts

Advanced oxidation processes (AOPs) have been postulated as viable, innovative, and efficient technologies for the removal of pollutants from water bodies. Among AOPs, photo-Fenton processes have been shown to be effective for the degradation of various types of organic compounds in industrial wastewater. Monometallic iron catalysts are limited in practical applications due to their low catalytic activity, poor stability, and recyclability. On the other hand, the development of catalysts based on copper oxides has become a current research topic due to their advantages such as strong light absorption, high mobility of charge carriers, low environmental toxicity, long-term stability, and low production cost. For these reasons, great efforts have been made to improve the practical applications of heterogeneous catalysts, and the bimetallic iron–copper materials have become a focus of research. In this context, this review focuses on the compilation of the most relevant studies on the recent progress in the application of bimetallic iron–copper materials in heterogeneous photo–Fenton-like reactions for the degradation of pollutants in wastewater. Special attention is paid to the removal efficiencies obtained and the reaction mechanisms involved in the photo–Fenton treatments with the different catalysts.

Engineering controllable oxygen vacancy defects in iron hydroxide oxide immobilized on reduced graphene oxide for boosting visible light-driven photo-Fenton-like oxidation

Visible light-driven photo-Fenton-like technology is a promising advanced oxidation process for water remediation, while the construction of effective synergetic system remains a great challenge. Herein, iron hydroxide oxide (α-FeOOH) with controllable oxygen vacancy defects were engineered on reduced graphene oxide (rGO) nanosheets (named as OVs-FeOOH/rGO) through an in-situ redox method for boosting visible light-driven photo-Fenton-like oxidation. By adjusting the pH environment to modulate the redox reaction kinetics between graphene oxide (GO) and ferrous salt precursors, the oxygen vacancy concentration in α-FeOOH could be precisely controlled. With optimized oxygen vacancy defects obtained at pH 5, the OVs-FeOOH/rGO displayed superior photo-Fenton-like performance for Rhodamine B degradation (99% within 40 mins, rate constant of 0.2278 mg^-1 L min^-1) with low H₂O₂ dosage (5 mM), standing out among the reported photo-Fenton-like catalysts. The catalyst also showed excellent reusability, general applicability, and tolerance ability of realistic environmental conditions, which demonstrates great potential for practical applications. The results reveal that moderate oxygen vacancy defects can not only strengthen absorption of visible light and organic pollutants, but also promote the charge transfer to simultaneously accelerate the photogenerated electron-hole separation and Fe(III)/Fe(II) Fenton cycle, leading to the remarkable photo-Fenton-like oxidation performance. This work sheds light on the controllable synthesis and mechanism of oxygen vacancy defects to develop efficient photo-Fenton-like catalysts for wastewater treatment.

Fabrication, functionalization and advanced applications of magnetic hollow materials in confined catalysis and environmental remediation

Magnetic hollow-structured functional hybrid materials with unique architectures and preeminent properties have always been an area of extensive research. They represent a subtle collaboration of hollow architecture, mesoporous nanostructure and magnetic character. Owing to the merits of a large void space, low density, high specific surface area, well-defined active sites and facile magnetic recovery, these materials present promising application projections in numerous fields, such as drug delivery, adsorption, storage, catalysis and many others. In this review, recent progress in the design, synthesis, functionalization and applications of magnetic hollow-meso/nanostructured materials are discussed. The first part of the review has been dedicated to the preparation and functionalization of the materials. The synthetic protocols have been broadly classified into template-assisted and template-free methods and major trends in their synthesis have been elaborated in detail. Furthermore, the benefits and drawbacks of each method are compared. The later part summarizes the application aspects of confined catalysis in organic transformations and environmental remediation such as degradation of organic pollutants, dyes and antibiotics and adsorption of heavy metal ions. Finally, an outlook of future directions in this research field is highlighted.

Facile synthesis of Cu-CuFe2O4 nanozymes for sensitive assay of H2O2 and GSH

Artificial enzymes have drawn substantial research interest from the scientific community due to their advantages over natural enzymes. However, majority of artificial enzymes exhibit low affinity towards H2O2, which means that a high H2O2 concentration is needed for the oxidation of a substrate such as 3,3',5,5'-tetramethylbenzidine (TMB) to blue-colored oxTMB. With this concern, Cu-CuFe2O4 was facilely synthesized, wherein, Cu0 accelerates the redox capacity of Cu-CuFe2O4 as well as the electron transfer between CuFe2O4 and H2O2. These materials induce excellent activity as a peroxidase. Cu-CuFe2O4 shows high affinity towards H2O2 with lower Michaelis-Menten constant (Km) than the reported values for ferrites and Horseradish enzyme (HRP). Moreover, it took only 5 min to detect hydrogen peroxide (H2O2) and glutathione (GSH) through a colorimetric assay using Cu-CuFe2O4. Compared with CuFe2O4, the limit of detection (LOD) is about 90-fold lower for H2O2 using Cu-CuFe2O4. In addition, Cu-CuFe2O4 shows high stability as a nanozyme. Thus, the mechanism of the peroxidase-like nanozyme Cu-CuFe2O4 is proposed.