Peptide-mediated green synthesis of the MnO2@ZIF-8 core-shell nanoparticles for efficient removal of pollutant dyes from wastewater via a synergistic process

Recent Development of Nanomaterials for Chemical Engineering

There has been an explosive growth in research on nanomaterials since the late 1980s and early 1990s [...].

An all-in-one portable colorimetric detection platform for sensitive detection of bisphenol A based on target-mediated CeO2@ZIF-8/Apt biocomposites

BPA aptamers functionalized cerium oxide nanoparticles encapsulated in zeolitic imidazolate framework-8 (CeO2@ZIF-8/Apt) were developed to fabricate an all-in-one portable platform for on-site quantitative detection of BPA. By combining biocomposites with a 3,3',5,5'-tetramethylbenzidine (TMB)-based sodium alginate (SA) hydrogel and smartphone-based RGB analysis, highly sensitive and convenient monitoring of BPA was achieved. CeO2@ZIF-8 composites were constructed using a novel surfactant-modified concentration-controlled synthesis strategy. After being functionalized with BPA aptamers, CeO2@ZIF-8/Apt biocomposites were used as target-response colorimetric probes for target recognition and signal transduction. The oxidase-like activity of CeO2@ZIF-8 was effectively sealed by BPA aptamers and controllably released in a concentration-dependent manner through aptamer-BPA reactions. Utilizing SA hydrogels containing TMB in the caps, a one-step sample addition and one-pot detection can be conveniently achieved and reliably quantified by smartphone-based RGB analysis in an instrument-free way. The detection range of this portable detection platform is 50 pg/mL to 500 ng/mL with limit of detection calculated as 34.88 pg/mL, comparable to that of conventional detection in the solution system (4.57 pg/mL). The recoveries in tap water, apple juice, and milk ranged from 91.02 % and 106.75 %. This work contributes new insights into the design of all-in-one detection platforms for contaminants monitoring in resource-constrained regions.

Preparation, Characterization, and Application of Metal Oxide-Doped Zeolitic Imidazolate Framework

Metal-organic frameworks (MOFs) attract the attention of researchers due to their unique properties, such as high surface area, porosity, and stability. Therefore, in this study, the synthesis of zeolitic imidazole frameworks (ZIF-8), a subclass of MOFs, and copper oxide (Cu2O) and manganese oxide (MnO2) containing ZIF-8 was carried out by a mixing method with methanol. The characterization results show that the polyhedral structure of ZIF-8 was prepared with a surface area of 2088 m2/g and a crystallite size of 43.48 nm. Then, each and mixture of two metal oxides were introduced into the ZIF-8 crystal structure. It was found that the surface area and pore volumes of all metal/ZIF-8 samples decreased with metal loading, depending on the type and ratio of metal oxides. The ZIF-8 containing 4.0 wt % Cu2O and 1.0 wt % MnO2 had the highest surface area (2084 m2/g), which was closest to that of ZIF-8. The polyhedral structure was maintained by the addition of both metal oxides, and the crystal size of the material decreased with the loading of MnO2 to the ZIF-8 structure. All of the synthesized samples were analyzed in supercapacitor applications and a relatively higher value of specific capacitance was obtained for Cu-Mn/ZIF-8 due to higher surface area and improved conductivity. In addition to supercapacitor applications, the properties of metal/ZIF-8 are also promising for applications such as catalysts, membranes, and gas storage.

Peroxymonosulfate Activation by Facile Fabrication of α-MnO2 for Rhodamine B Degradation: Reaction Kinetics and Mechanism

The persulfate-based advanced oxidation process has been an effective method for refractory organic pollutants' degradation in aqueous phase. Herein, α-MnO₂ with nanowire morphology was facially fabricated via a one-step hydrothermal method and successfully activated peroxymonosulfate (PMS) for Rhodamine B (RhB) degradation. Influencing factors, including the hydrothermal parameter, PMS concentration, α-MnO₂ dosage, RhB concentration, initial pH, and anions, were systematically investigated. The corresponding reaction kinetics were further fitted by the pseudo-first-order kinetic. The RhB degradation mechanism via α-MnO₂ activating PMS was proposed according to a series of quenching experiments and the UV-vis scanning spectrum. Results showed that α-MnO₂ could effectively activate PMS to degrade RhB and has good repeatability. The catalytic RhB degradation reaction was accelerated by increasing the catalyst dosage and the PMS concentration. The effective RhB degradation performance can be attributed to the high content of surface hydroxyl groups and the greater reducibility of α-MnO₂, and the contribution of different ROS (reactive oxygen species) was ¹O₂ > O2·- > SO4·- > ·OH.

MnO2 Doped with Ag Nanoparticles and Their Applications in Antimicrobial and Photocatalytic Reactions

A wide range of nanoparticles have been produced for photocatalysis applications. Nonetheless, degrading organic dyes requires nanoparticles that are efficient and excellent. As a photocatalyst, pure manganese oxide (MnO2) was prepared via a sol–gel method using silver (Ag) nanoparticles of transition metal oxide. In addition to X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX), the crystal structure and elemental composition were analysed. According to XRD data, the transition metal of MnO2 oxide is highly pure and has a small crystallite size. The presence of functional groups was confirmed and clarified using Fourier-transform infrared spectra (FTIR). By irradiating the transition pure and doped MnO2 photocatalysts with visible light, the UV-vis, μ-Raman, and surface areas were determined. As a result, of using the photocatalysts with aqueous methylene blue (MB) solutions under visible light irradiation, the MnO2 doped with Ag nanoparticles demonstrated high degradation efficiencies and were utilised to establish heterogeneous photocatalysis dominance. In this paper, we demonstrate that the photocatalytic efficiency of transition metal oxides is exclusively determined by the particle size and surface area of nano-sized materials. Due to their high surface charge ratio and different surface orientations, have the highest photocatalytic efficiency. Generally, MnO2 doped with Ag nanoparticles is resistant to bacteria of both Gram-positive and Gram-negative types (B. sublittus and Escherichia coli). There is still a need for more research to be performed on reducing the toxicity of metal and metal oxide nanoparticles so that they can be used as an effective alternative to antibiotics and disinfectants, particularly for biomedical applications.

ZIF-8 metal organic framework materials as a superb platform for the removal and photocatalytic degradation of organic pollutants: a review

Metal organic frameworks (MOFs) are attracting significant attention for applications including adsorption, chemical sensing, gas separation, photocatalysis, electrocatalysis and catalysis. In particular, zeolitic imidazolate framework 8 (ZIF-8), which is composed of zinc ions and imidazolate ligands, have been applied in different areas of catalysis due to its outstanding structural and textural properties. It possesses a highly porous structure and chemical and thermal stability under varying reaction conditions. When used alone in the reaction medium, the ZIF-8 particles tend to agglomerate, which inhibits their removal efficiency and selectivity. This results in their mediocre reusability and separation from aqueous conditions. Thus, to overcome these drawbacks, several well-designed ZIF-8 structures have emerged by forming composites and heterostructures and doping. This review focuses on the recent advances on the use of ZIF-8 structures (doping, composites, heterostructures, etc.) in the removal and photodegradation of persistent organic pollutants. We focus on the adsorption and photocatalysis of three main organic pollutants (methylene blue, rhodamine B, and malachite green). Finally, the key challenges, prospects and future directions are outlined to give insights into game-changing breakthroughs in this area.