Relationships Between Crystal, Internal Microstructures, and Physicochemical Properties of Copper-Zinc-Iron Multinary Spinel Hierarchical Nano-microspheres

Spinel ferrites (MFe2O4): Synthesis, improvement and catalytic application in environment and energy field

To develop efficient catalysts is one of the major ways to solve the energy and environmental problems. Spinel ferrites, with the general chemical formula of MFe₂O₄ (where M = Mg²⁺, Co²⁺, Ni²⁺, Zn²⁺, Fe²⁺, Mn²⁺, etc.), have attracted considerable attention in catalytic research. The flexible position and valence variability of metal cations endow spinel ferrites with diverse physicochemical properties, such as abundant surface active sites, high catalytic activity and easy to be modified. Meanwhile, their unique advantages in regenerating and recycling on account of the magnetic performances facilitate their practical application potential. Herein, the conventional as well as green chemistry synthesis of spinel ferrites is reviewed. Most importantly, the critical pathways to improve the catalytic performance are discussed in detail, mainly covering selective doping, site substitution, structure reversal, defect introduction and coupled composites. Furthermore, the catalytic applications of spinel ferrites and their derivative composites are exclusively reviewed, including Fenton-type catalysis, photocatalysis, electrocatalysis and photoelectro-chemical catalysis. In addition, some vital remarks, including toxicity, recovery and reuse, are also covered. Future applications of spinel ferrites are envisioned focusing on environmental and energy issues, which will be pushed by the development of precise synthesis, skilled modification and advanced characterization along with emerging theoretical calculation.

Yolk-shell (Cu,Zn)Fe2O4 ferrite nano-microspheres with highly selective triethylamine gas-sensing properties

Multicomponent spinel ferrites are essential to be used in high-performance gas-sensing materials. Herein, multinary (Cu,Zn)Fe2O4 spinel nano-microspheres with tunable internal structures, including solid, core-shell, and yolk-shell, were successfully synthesized by a simple self-templated solvothermal method combined with a subsequent annealing strategy. The internal structures of the (Cu,Zn)Fe2O4 nano-microspheres significantly rely on the heating rates of the precursors, which show promising selective response towards trimethylamine gas. Among them, the as-formed yolk-shell (Cu,Zn)Fe2O4 nano-microspheres exhibited high response to triethylamine with excellent selectivity of STEA/SX = 1.86 at 160 °C, fast response-recovery rate (58 s/136 s), and long-term repeatability and stability of more than one month. The corresponding triethylamine gas-sensing mechanism with the special microstructures is discussed. This work provides new insights into the rational design of interior structure and the modulation of high gas response and selectivity of multinary spinel ferrites in gas-sensing applications.

Multifunctional Magnetic Copper Ferrite Nanoparticles as Fenton-like Reaction and Near-Infrared Photothermal Agents for Synergetic Antibacterial Therapy

Synergistic therapeutic strategies for bacterial infection have attracted extensive attentions owing to their enhanced therapeutic effects and less adverse effects compared with monotherapy. Herein, we report a novel synergistic antibacterial platform that integrates the nanocatalytic antibacterial therapy and photothermal therapy (PTT) by hemoglobin-functionalized copper ferrite nanoparticles (Hb-CFNPs). In the presence of a low concentration of hydrogen peroxide (H₂O₂), the excellent Fenton and Fenton-like reaction activity of Hb-CFNPs can effectively catalyze the decomposition of H₂O₂ to produce hydroxyl radicals (·OH), rendering an increase in the permeability of the bacterial cell membrane and the sensitivity to heat. With the assistance of NIR irradiation, hyperthermia generated by Hb-CFNPs can induce the death of the damaged bacteria. Additionally, owing to the outstanding magnetic property of Hb-CFNPs, it can improve the photothermal efficiency by about 20 times via magnetic enrichment, which facilitates to realize excellent bactericidal efficacy at a very low experimental dose (20 μg/mL). In vitro antibacterial experiment shows that this synergistic antibacterial strategy has a broad-spectrum antibacterial property against Gram-negative Escherichia coli (E. coli, 100%) and Gram-positive Staphylococcus aureus (S. aureus, 96.4%). More importantly, in vivo S. aureus-infected abscess treatment studies indicate that Hb-CFNPs can serve as an antibacterial candidate with negligible toxicity to realize synergistic treatment of bacterial infections through catalytic and photothermal effects. Accordingly, this study proposes a novel, high-efficiency, and multifunctional therapeutic system for the treatment of bacterial infection, which will open up a new avenue for the design of synergistic antibacterial systems in the future.

Sustainable fixation of CO2 into epoxides to form cyclic carbonates using hollow marigold CuCo2O4 spinel microspheres as a robust catalyst

The present work demonstrates the chemical fixation of CO₂ for the synthesis of organic carbonates using mesoporous hollow marigold CuCo₂O₄ spinel microspheres as a catalyst prepared using the solvothermal method.

Two-dimensional SnS2 nanosheets exfoliated from an inorganic–organic hybrid with enhanced photocatalytic activity towards Cr(vi) reduction

Thin SnS₂ nanosheets with {001} facets dominating were obtained with the liquid-exfoliation method and exhibit largely improved photocatalytic activity for Cr(vi) reduction.