ZnFe2O4 Surface Research Articles

Magnetic Field Induction ZnFe2O4@Carbon for Construction of a PVDF‐HFP‐Based 3D Dielectric Network

AbstractFunctional fillers in the polymerization system cannot be arranged in an orderly manner when exposed to natural conditions. The application of magnetic fields in the material preparation process has been shown to greatly enhance the distribution of functional fillers, leading to the organized alignment of functional fillers and the production of polymer matrix composites with remarkable characteristics. In this experiment, rod‐like ZnFe2O4 was synthesized by reverse microemulsion method, and amorphous carbon was coated on the surface of ZnFe2O4 by freeze‐drying method to obtain ZnFe2O4@Carbon core‐shell particles. The composite films were prepared by dispersing ZnFe2O4 with different volume contents into P(VDF‐HFP) matrix. The external parallel magnetic field was used to manipulate the ZnFe2O4@C/P(VDF‐HFP) composite film during the hot‐pressing process, resulting in an oriented ZnFe2O4@C/P(VDF‐HFP) composite film. The experiment revealed that when ZnFe2O4@C is aligned with the film orientation, the dielectric constant of the composite film is 50(50 Hz), which is 130 % higher than that of the unoriented composite film and 290 % higher than that of pure P(VDF‐HFP). When the filling amount is 40 Vol.%, the energy storage density of ZnFe2O4@C/P(VDF‐HFP) composite film is 1.18 times higher than that of unoriented composite material and 1.32 times higher than that of pure P(VDF‐HFP).

Biogenic Punica granatum Flower Extract Assisted ZnFe2O4 and ZnFe2O4-Cu Composites for Excellent Photocatalytic Degradation of RhB Dye.

Globally, the textile industry contributes to pollution through accidental discharges or discharge of contaminated wastewater into waterways, significantly affecting water quality. These pollutants, including dye molecules, are environmental hazards for aquatic and terrestrial life. The field of visible light-mediated photocatalysis has experienced rapid growth, driven by the utilization of photocatalysts that can absorb low-energy visible light and effectively degrade dyes. In the present study, we report a simple method to controllably synthesize Fe2O3, ZnO, and ZnFe2O4 using the one-pot synthesis method. In the subsequent step, copper (Cu) was deposited on the surface of ZnFe2O4 (forming ZnFe2O4-Cu) using a facile, green, and cost-effective method. The synthesized samples were characterized using various techniques, including XRD, UV-Vis DRS, FT-IR, SEM-EDX, HR-TEM, XPS, PL, and BET analysis. These techniques were employed to investigate the composition, morphology, structure, and photophysical properties of as-prepared samples. The ZnFe2O4-Cu nanocomposite demonstrated efficient photocatalytic activity for degrading RhB dye pollutants under visible light. The photocatalyst was successfully reused for three consecutive cycles without significantly decreasing performance. Furthermore, during the study, the radical scavenging test emphasized the role of different radicals in the degradation of dye pollutants. This research has the potential to enable the efficient production of high-performance photocatalysts that can rapidly eliminate ecologically harmful dyes from aqueous solutions.

Magnetic ZnFe2O4 composite advances SERS assay for Patent blue V

BackgroundPatent blue V (PbV) an Azo colorant because of its high toxicity to children has been severely limited in food industry. However, frequently the abuse of PbV in some artificial foods is still exposed by media. Current methods for the detection of PbV have to perform tedious pre-processing and the detection sensitivity and speed are required to be further improved. ResultsIn this work, we immobilize gold nanoparticles (Au NPs) on the surface of ZnFe2O4 with aid of Inositol hexaphosphate (IP6) to prepare a novel magnetic surface-enhanced Raman scattering (SERS) substrate (designated as ZnFe2O4–IP6–Au NPs) for rapid detection of PbV in beverages. Synergistic effect of magnetic enrichment, magnetic inducing improvement effect (MIIE) and efficient charge transfer (CT) enables ZnFe2O4–IP6–Au NPs-based SERS assay to achieve limit of detection of PbV down to 1.31 × 10−8 mol/L and a concentration linear relationship ranging from 8.6 × 10−4 to 8.6 × 10−8 mol/L. The detection recoveries for PbV in beverages locate in the range from 98.1 to 102.5 %, meaning the feasibility of method. In addition, the presence of IP6 protection greatly improves the storage stability of ZnFe2O4–IP6–Au NPs. SignificanceZnFe2O4–IP6–Au NPs substrates with excellent SERS performance could on-site, rapidly and sensitively detect PbV. As a perspective, magnetic-composite-based SERS assay has great scenario in food safety by using portable Raman spectrometer.

ZnFe2O4 nanoparticles with iron-rich surfaces for enhanced photocatalytic water vapor splitting

Photocatalytic water splitting has emerged as a promising avenue for the utilization of solar energy to produce hydrogen. To advance the development of photocatalytic hydrogen production, the optimization and design of novel photocatalysts is a crucial task. In this study, ZnFe2O4 nanoparticles with iron-rich surfaces were synthesized through alkali treatment and employed in photocatalytic water vapor decomposition. The alkali-treated ZnFe2O4 displayed superior photocatalytic activity, with the optimized sample exhibiting an impressive H2 generation rate of 61.9 μmol·g−1 after 5 h of irradiation, which is significantly higher than the untreated ZnFe2O4 sample (15.9 μmol·g−1). This enhanced performance is attributed to the improved separation of photogenerated carriers and the improved adsorption of water molecules on the iron-rich ZnFe2O4 surface. This research may provide a valuable guide for the design of highly active ternary oxide/sulfide semiconductor photocatalysts for water vapor splitting.

Enhanced degradation of herbicides in groundwater using sulfur-containing reductants and spinel zinc ferrite activated persulfate

A challenge to successfully implementing an injection-based remedial treatment in aquifers is to ensure that the oxidative reaction is efficient and lasts long enough to contact the contaminated plume. Our objective was to determine the efficacy of zinc ferrite nanocomposites (ZnFe2O4) and sulfur-containing reductants (SCR) (i.e., dithionite; DTN and bisulfite; BS) to co-activate persulfate (S2O82−; PS) and treat herbicide-contaminated water. We also evaluated the ecotoxicity of the treated water. While both SCRs delivered excellent PS activation in a 1:0.4 ratio (PS:SCR), the reaction was relatively short-lived. By including ZnFe2O4 in the PS/BS or PS/DTN activations, herbicide degradation rates dramatically increased by factors of 2.5 to 11.3. This was due to the SO4− and OH reactive radical species that formed. Radical scavenging experiments and ZnFe2O4 XPS spectra results revealed that SO4− was the dominant reactive species that originated from S(IV)/PS activation in solution and from the Fe(II)/PS activation that occurred on the ZnFe2O4 surface. Based on liquid chromatography mass spectrometry (LC–MS), atrazine and alachlor degradation pathways are proposed that involve both dehydration and hydroxylation. In 1-D column experiments, five different treatment scenarios were run using 14C-labeled and unlabeled atrazine, and 3H2O to quantify changes in breakthrough curves. Our results confirmed that ZnFe2O4 successfully prolonged the PS oxidative treatment despite the SCR being completely dissociated. Toxicity testing showed treated 14C-atrazine was more biodegradable than the parent compound in soil microcosms. Post-treatment water (25 %, v/v) also had less impact on both Zea Mays L. and Vigna radiata L. seedling growth, but more impact on root anatomies, while ≤4 % of the treated water started to exert cytotoxicity (<80 % viability) on ELT3 cell lines. Overall, the findings confirm that ZnFe2O4/SCR/PS reaction is efficient and relatively longer lasting in treating herbicide-contaminated groundwater.

Efficient activation of persulfate by Ti3C2 MXene QDs modified ZnFe2O4 for the rapid degradation of tetracycline

Mxene-based catalysts with specific interfacial characteristics are beneficial for photocatalytic applications. Herein, Ti3C2 MXene modified ZnFe2O4 nanocomposite materials were prepared for photocatalysis. The morphology and structure of the nanocmposites were characterized by scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), which revealed that Ti3C2 MXene as quantum dots (QDs) was uniformly distributed on the ZnFe2O4 surface. The Ti3C2 QDs modified ZnFe2O4 catalyst (ZnFe2O4/MXene-15%) under visible light achieved 87% degradation efficiency of tetracycline within 60 min when coupled with persulfate (PS) system. The initial solution pH, PS dosage and co-existing ions were found to be the main factors affecting the heterogeneous oxidation process, while quenching experiments showed that O2•- is the main oxidizing species in the removal of tetracycline in ZnFe2O4/MXene-PS system. In addition, the cyclic experiments suggested that ZnFe2O4/MXene had good stability and thus it may have practical applications in industry.

Pt-decorated ZnFe2O4 sensors prepared via a facile impregnation method free of reductants and surfactants for conductometric acetone sensing

Noble metals have been widely reported to improve sensing properties. However, conventional methods of preparing noble metal-decorated metal oxide sensors usually involve the use of multiple reductants and surfactants, as well as complex equipment and procedures, and most importantly, waste noble metal sources. In this study, we develop a novel modified impregnation method, which is a green, energy-saving, fast, convenient technique for preparing Pt-decorated ZnFe2O4 gas sensors. This method consists only of mixing ZnFe2O4 powder into a H2PtCl6 solution and then fabricating sensors by a general procedure, without the use of additional reagents or further treatment. Detailed structural and chemical analyses revealed that over 88% of Pt element was uniformly dispersed on the surface of ZnFe2O4. The average activation energy decreased by 51% after Pt was decorated onto the surface of ZnFe2O4, resulting in a shorter response time. As expected, the thus prepared Pt-decorated ZnFe2O4 sensors are superior to pristine commercial ZnFe2O4 in terms of better sensing properties, a higher response, and a lower optimal temperature. The proposed reductant-free impregnation method was demonstrated to provide noble-metal-decorated metal oxides successfully, easily, quickly, and economically.

Thermal and bisphenol-A adsorption properties of a zinc ferrite/β-cyclodextrin polymer nanocomposite.

The present study investigated the use of a nanocomposite, produced by reinforcing nanosize zinc ferrite (ZnFe2O4) in a porous β-CD based polymeric matrix (β-CD-E-T/ZnFe2O4), for the removal of Bisphenol A (BPA) from aqueous solutions via adsorption. The thermal stability of the β-CD-based polymer and β-CD-E-T/ZnFe2O4 nanocomposite were investigated using simultaneous thermal analysis at four heating rates. Non-isothermal isoconversion methods were employed to study the thermal degradation kinetics of the β-CD based polymer before and after ZnFe2O4 nano-filling. The results showed that ZnFe2O4 nano-reinforcement increased the activation energy barrier for the thermal degradation of the β-CD-based polymeric matrix. Adsorption experiments showed that the β-CD-E-T/ZnFe2O4 nanocomposite exhibited very high BPA adsorption within 5 minutes. Isotherm, kinetics, and thermodynamic investigations revealed that the adsorption of BPA was via multilayer adsorption on a heterogeneous β-CD-E-T/ZnFe2O4 surface. The thermodynamic studies indicated that BPA adsorption on β-CD-E-T/ZnFe2O4 was spontaneous and exothermic. Overall, the β-CD-E-T/ZnFe2O4 nanocomposite showed less thermal degradation and high efficiency for removing BPA from contaminated water, indicating its potential as a promising material for wastewater treatment applications.

ZnFe2O4@l-Arginine-Ni: A novel, green, recyclable, and highly versatile catalyst for the synthesis of 1H-tetrazoles and oxidation of sulfides to the sulfoxides

In this work, we report the synthesis of ZnFe2O4@l-Arginine-Ni as a novel and green nanomagnetic catalyst, which is containing the l-Arginine-Ni catalytic sites on the surface of ZnFe2O4 as the catalytic support. The as-synthesized ZnFe2O4@l-Arginine-Ni MNPs were characterized with accuracy by different physicochemical methods; including, Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), X-ray powder diffraction (XRD), Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray elemental mapping, Thermogravimetric (TGA), and Vibrating Sample Magnetometry (VSM) analyses. The prepared magnetic nanoparticles exhibit excellent catalytic activity in synthesizing 1H-tetrazole derivatives and oxidation of sulfides to the sulfoxide under green conditions. The heterogeneous nature of the catalyst was confirmed via the hot filtration experiment. Furthermore, the activity of the recycled nanocatalyst was examined for at least five cycles with a negligible loss of its activity.

Room temperature detection of low-concentration H2S based on CuO functionalized ZnFe2O4 porous spheres

Room temperature H2S gas sensor with low detection limit is necessary for practical application. In this work, ZnFe2O4 was synthesized through a simple solvothermal method, and then CuO was decorated onto the surface of ZnFe2O4 via a modified metal organic framework synthesis method. After a series of characterization methods, it was found that CuO/ZnFe2O4 had porous nanosphere morphology. Gas sensing measurements indicating that the synthesized CuO/ZnFe2O4 porous spheres exhibited excellent H2S sensing performance under room temperature, including high sensitivity under low concentration (less than 10 ppm), excellent selectivity, low limit of detection (0.1 ppm), good repeatability, and fast response/recovery time. The sensing mechanism was discussed in detail, which is mainly contributed to the sensitization effect of CuO. This work provides a new strategy for constructing room temperature H2S gas sensor based on ZnFe2O4.

Investigation on In Situ Carbon-Coated ZnFe2O4 as Advanced Anode Material for Li-Ion Batteries.

ZnFe2O4 as an anode that is believed to attractive. Due to its large theoretical capacity, this electrode is ideal for Lithium-ion batteries. However, the performance of ZnFe2O4 while charging and discharging is limited by its volume growth. In the present study, carbon-coated ZnFe2O4 is synthesized by the sol–gel method. Carbon is coated on the spherical surface of ZnFe2O4 by in situ coating. In situ carbon coating alleviates volume expansion during electrochemical performance and Lithium-ion mobility is accelerated, and electron transit is accelerated; thus, carbon-coated ZnFe2O4 show good electrochemical performance. After 50 cycles at a current density of 0.1 A·g−1, the battery had a discharge capacity of 1312 mAh·g−1 and a capacity of roughly 1220 mAh·g−1. The performance of carbon-coated ZnFe2O4 as an improved anode is electrochemically used for Li-ion energy storage applications.

Preparation, Characterization and Application of Epitaxial Grown BiOBr (110) Film on ZnFe2O4 Surface with Enhanced Photocatalytic Fenton Oxidation Properties.

A novel BiOBr photocatalyst was epitaxially grown in situ onto the surface of ZnFe2O4, a ferroelectric material with a strong polarization effect. The formatted BiOBr/ZnFe2O4 composite (BOB/ZFO) showed excellent photocatalytic degradation performance of tetracycline antibiotics (TCs). One of the composites with ZnFe2O4 content of 10% (BOB/ZFO-10) showed the best properties; the degradation efficiency of TCs upon visible light irradiation for 180 min was 99.2%, which was 3.58 times higher than that of pure phase BiOBr. The functions of ZnFe2O4 are assumed to be such that the addition of this ferroeletric material not only regulated the spontaneous polarization of BiOBr in the process of synthesis, but also resulted in the construction of Z-scheme heterostructures due to the appropriate staggered band structure of BiOBr and ZnFe2O4. In the presence of ferroelectric material ZnFe2O4, the local structure of BiOBr may be distorted accordingly, resulting in preferential growth of a (110) crystal facet of BiOBr and enhancement of spontaneous polarization, which promotes the efficient separation of photogenerated electron-hole pairs of ZnFe2O4 and BiOBr, and therefore enhances the redox capacity of the photocatalytic degradation of organic pollutants.

RGO Sheets/ZnFe2O4 Nanocomposities as an Efficient Electro Catalyst Material for I3−/I− Reaction for High Performance DSSCs

In this paper, Reduced Graphene Oxide (rGO)/ZnFe2O4 (rZnF) nanocomposite is synthesized by a simple hydrothermal method and employed as a counter electrode (CE) material for tri-iodide redox reactions in Dye sensitized solar cells (DSSC) to replace the traditional high cost platinum (Pt) CE. X-ray diffraction analysis and High resolution Transmission electron microscopy, clearly indicated the formation of rZnF nanocomposite and also amorphous rGO sheets were smoothly distributed on the surface of ZnFe2O4 (ZnF) nanostructure. The rZnF-50 CE shows excellent electro catalytic activity toward I3− reduction, which has simultaneously been confirmed by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization measurements. A DSSC developed by rZnF-50 CE (η = 8.71%) obtained quite higher than the Pt (η = 8.53%) based CE under the same condition. The superior performances of rZnF-50 CE due to addition of graphene in to Spinel (ZnF) nanostructure results in creation of highly active electrochemical sites, fast electron transport linkage between CE and electrolyte. Thus it’s a promising low cost CE material for DSSCs.

Evaluation of the effects of Au addition into ZnFe2O4 nanostructures on acetone detection capabilities

Spinel type zinc ferrite (ZnFe2O4) nanostructured based sensors are conducive to the detection of volatile organic compounds. However, their poor sensing capabilities hinder practical application. Herein, we produced pure ZnFe2O4 and Au modified ZnFe2O4 nanostructures to evaluate the effects of ZnFe2O4 surface modification towards acetone detection. The pure and Au modified ZnFe2O4 nanostructures were facilely prepared using a microwave-assisted hydrothermal approach. Successful incorporation of Au into ZnFe2O4 NPs and the subsequent influence on ZnFe2O4 nanostructure was evaluated by X-ray diffraction, high resolution-transmission electron microscopy, and X-ray photoelectron spectroscopy. Comparative gas sensing analysis between the pure and Au modified ZnFe2O4 based sensors demonstrated that the modified sensor exhibited high response and selectivity towards acetone (C3H6O) at an operating temperature of 120 °C compared to the pure sensor owing to a high concentration of defects and sensitization effects.

New insight in adsorption of Sb(III)/Sb(V) from waters using magnetic nanoferrites: X-ray absorption spectroscopy investigation

Antimony (Sb) is widely used in many agricultural and industrial application. However, Sb contamination can threaten ecosystem and human health. This study attempts to find a simple and fast way in removing Sb, especially for severely toxic Sb(III) from waters. Six kinds of magnetic nanoferrites (CuFe2O4, MnFe2O4, CoFe2O4, NiFe2O4, ZnFe2O4, Fe3O4) were synthesized to investigate their ability in removing Sb(III) and Sb(V) from aquatic systems. Sb K-edge XANES spectra indicated that Sb(V) was adsorbed on the surface of ZnFe2O4 and would not be converted to more toxic Sb(III). Contrarily, Sb(III) was observed to be adsorbed on ZnFe2O4 and ZnFe2O4 could oxidize Sb(III) to Sb(V). O K-edge XANES analyses showed the downswing of Fe 3d-O 2p characteristic peak after adsorption, which proved again that ZnFe2O4 had the great potential to adsorb and oxidize Sb(III) in aqueous solutions. EXAFS revealed that the peaks on k-space and R-space were quite different, implying that Sb(III) and/or Sb(V) did not replace Fe and/or Zn during the adsorption process. Additionally, XRD spectrum showed that after adsorption of Sb(III) and/or Sb(V), the structure of ZnFe2O4/Fe3O4 remained as fcc spinel structure (Fd-3m), indicating that these nanoferrites possessed good structural stability. This study provided essential information for designing a rapid and effective Sb removal technique in treating Sb-contaminated river water, tap water, and groundwater.

Role of Surfaces in the Magnetic and Ozone Gas-Sensing Properties of ZnFe2O4 Nanoparticles: Theoretical and Experimental Insights.

The magnetic properties and ozone (O3) gas-sensing activity of zinc ferrite (ZnFe2O4) nanoparticles (NPs) were discussed by the combination of the results acquired by experimental procedures and density functional theory simulations. The ZnFe2O4 NPs were synthesized via the microwave-assisted hydrothermal method by varying the reaction time in order to obtain ZnFe2O4 NPs with different exposed surfaces and evaluate the influence on its properties. Regardless of the reaction time employed in the synthesis, the zero-field-cooled and field-cooled magnetization measurements showed superparamagnetic ZnFe2O4 NPs with an average blocking temperature of 12 K. The (100), (110), (111), and (311) surfaces were computationally modeled, displaying the different undercoordinated surfaces. The good sensing activity of ZnFe2O4 NPs was discussed in relation to the presence of the (110) surface, which exhibited low (-0.69 eV) adsorption enthalpy, promoting reversibility and preventing the saturation of the sensor surface. Finally, the O3 gas-sensing mechanism could be explained based on the conduction changes of the ZnFe2O4 surface and the increase in the height of the electron-depletion layer upon exposure toward the target gas. The results obtained allowed us to propose a mechanism for understanding the relationship between the morphological changes and the magnetic and O3 gas-sensing properties of ZnFe2O4 NPs.

Hierarchical bead chain ZnFe2O4-PEDOT composites with enhanced Li-ion storage properties as anode materials for lithium-ion batteries

In this study, we synthesized hierarchical bead chain ZnFe2O4-PEDOT composites with network of macroporous channels. For the first time, a ZnFe2(C2O4)3 precursor was prepared by co-precipitation using steel waste pickling liquor as a raw material, which was then sintered in air at 800 °C to yield monolithic ZnFe2O4. PEDOT was coated on the surface of ZnFe2O4 via in-situ polymerization of 3,4-ethylenedioxythiophene (EDOT). Electrochemical measurements showed that the 15 wt% PEDOT coated ZnFe2O4 composites (ZFPE-15) delivered a discharge capacity of 1510.5 mAh g−1 at 100 mA g−1 after 200 cycles, which was much larger than that of pure ZnFe2O4 (1055.9 mAh g−1), 10 wt% PEDOT coated ZnFe2O4 composites (ZFPE-10, 1264.2 mAh g−1), and 20 wt% coated ZnFe2O4 composites (ZFPE-20, 900.1 mAh g−1). Additionally, the ZFPE-15 composite exhibited a reversible capacity of 1004.7 mAh g−1, even at a large current density of 1 A g−1 after 200 cycles. These more desirable electrochemical properties can be attributed to the interconnected macroporous channels in the hierarchical bead chain skeleton, which can buffer volume expansion during circulation and inhibit particle agglomeration. Furthermore, the PEDOT nanoparticle coating produces a composite with greater mechanical strength and higher electrical conductivity, which provides higher electron transfer during the charge/discharge processes.

Novel Ag–TiO2/ZnFe2O4 Nanocomposites for Effective Photocatalytic, Electrocatalytic and Cytotoxicity Applications

We report the preparation and characterization of a new heterostructured Ag-TiO₂/ZnFe₂O₄ (ATZ) nanocomposite. X-ray diffraction (XRD) reveals the presence of spinel type ZnFe₂O₄ and anatase TiO₂. Scanning electron microscope (SEM) images of ATZ nanocomposites show that Ag nanoparticles are successfully loaded on the composite Ag-TiO₂ and is uniformly distributed on surface of ZnFe₂O₄ forming a nanocomposite with an approximate particle size of 44.8 nm. High-resolution transmission electron microscope (HR-TEM) analysis clearly indicates the particles with spherical and hexagonal structure and sizes of most of the particles are below 50 nm. Ultra violet-visible diffuse reflectance spectra (UV-vis-DRS) show that Ag-TiO₂/ZnFe₂O₄ has increased visible absorption than TiO₂. Photoluminescence (PL) spectra shows that the intensity of ATZ is low relative to prepared TiO₂. The photocatalytic degradation of Reactive Yellow 86 (RY 86) dye was studied. Based on the band gap energies of TiO₂ and ZnFe₂O₄, a mechanism of degradation is given. Photocatalytic activity results suggest that as-prepared ATZ shows higher photodegradation efficiency than pure TiO₂. The main reactive oxidative species involved in the degradation and stability of photocatalyst were also investigated. ATZ shows higher electrocatalytic activity than TiO₂ for methanol electrooxidation. The cytotoxicity of ATZ was analysed. Multifunctionality of ATZ makes it useful for environmental and biomedical applications.

Ab-initio approach to the stability and the structural, electronic and magnetic properties of the (001) Znfe2O4 surface terminations

We present a Density Functional Theory (DFT) based study of the structural and magnetic properties of the (001) surface of the semiconducting oxide ZnFe2O4 (spinel structure). The calculations were performed using the DFT based ab initio plane wave and pseudopotential method as implemented in the Quantum Espresso code. The all electron Full-potential linearized-augmented-plane-wave method (FP-LAPW) was also employed to check the reproducibility of the plane wave method. In both calculations the DFT+U methodology was employed and different (001) surface terminations of ZnFe2O4 were studied. We find that the surface terminated in Zn is the stable one. For all the (001) surface terminations our calculations predict that the Zn-Fe cationic inversion (anti-sites), which are defects in bulk ZnFe2O4, becomes stable and an integral part of the surface. Also, a ferrimagnetic behavior is predicted for the case of anti-sites in the superficial layer. Our results for different properties of the surface of ZnFe2O4 are compared with those obtained in bulk samples and those reported in the literature.

Magnetic ZnFe2O4@ZnSe hollow nanospheres for photocatalytic hydrogen production application

Magnetic ZnFe2O4@ZnSe hollow nanospheres were fabricated by a two-step method and applied for visible light photocatalytic water splitting. Magnetic ZnFe2O4 hollow nanosphere was prepared by using the carbonaceous microsphere as a template, and ZnSe nanoparticles were in site grown on the ZnFe2O4 surface. Through optimizing the reaction time, ZnFe2O4@ZnSe hollow nanospheres exhibited efficient light absorption and improved photocatalytic performance, and ZnFe2O4@ZnSe-20 with suitable ZnSe shell thickness possessed highest hydrogen production amount in 6 h (16897.3 μmol/g). The experimental results revealed that the formation of heterojunction between ZnSe and ZnFe2O4 effectively separated and transferred the photo-induced electrons and holes, and inhibited the electron-hole pairs recombination. In addition, the magnetic recyclability of ZnFe2O4@ZnSe hollow nanospheres was beneficial to further photocatalytic hydrogen production application.