α-Fe2O3 Composites Research Articles

Utilising bauxite residue (red mud) to construct Z-type heterojunction for formaldehyde degradation

The photocatalytic treatment of pollutants has garnered significant attention owing to its ability to safely and efficiently treat pollutants without secondary contamination. However, the complexity of synthesis methods and the high costs of photocatalysts remain major challenges for the industrial application of this technology. The high content of α-Fe2O3 metal semiconductors in red mud (RM) presents an opportunity for the effective preparation of RM-based α-Fe2O3 composites for catalytic degradation. Graphitic-phase carbon nitride features a similar energy band structure to α-Fe2O3 and demonstrates excellent photocatalytic properties. Herein, we directly prepared a novel Z-scheme-heterojunction g-C3N4/RM composites via a one-step calcination method by reconstructing the interface between RM and melamine. Comprehensive characterisations revealed the formation of a Z-scheme heterojunction between g-C3N4 and α-Fe2O3. This significantly improved the spatial separation of photogenerated carriers, enabling the efficient degradation of formaldehyde. The degradation efficiency reached 63.04% after 2 h of light exposure, and the composites exhibited excellent recyclability. The optical adsorption and photocatalytic properties of this newly developed composite material were significantly enhanced compared with pristine RM, which degraded 26.96% of formaldehyde under similar conditions. This study marks the first application of Z-type heterojunctions constructed from bauxite residue and nonmetallic semiconductors for degrading formaldehyde, an air pollutant. Our work offers new insights into leveraging solid wastes for high-value-added advanced catalytic applications.

Variation in defects and properties in composite of ZnO and α-Fe2O3 for sustainable wastewater treatment

Defects in nanostructures play a pivotal role in determining their properties and performance in the desired applications. Herein, the defect states and structural properties of the bi-metal oxide composite of ZnO and α-Fe2O3 (ZF-W) are varied by annealing the composite at different temperatures. The changes in defects, structures, and phase are evaluated thoroughly using transmission electron microscopy, x-ray diffraction, photoluminescence, and Mössbauer spectroscopy techniques. The defect-rich ZF-W composite is found to be composed of defect-deficient ZnFe2O4 attaining the equilibrium state when as-synthesized ZF-W is annealed at 500 °C [ZF-W(500)]. Further annealing at 1000 °C, ZF-W(1000), a non-stoichiometric and highly defected ZnFe2O4 is evidenced in the composite. The changes in the composite with the annealing temperature are correlated with the cationic migration and evolution of defect states. Moreover, the transition associated with the vacancy defects, which trapped the excited electron and dispel the free electrons, thereby inhibiting fast electron–hole pair recombination, is corroborated from the photoluminescence spectra. When implemented for methyl blue adsorption/degradation without the assistance of any external sources, the degradation efficiency of ZF-W, ZF-W(300), ZF-W(500), and ZF-W(1000) is found to be 86%, 84%, 68%, and 82%, respectively. The prepared samples are highly stable and can be used repeatedly without losing effectiveness. The simultaneous evolution of defects and structural properties of the composite are attributed for the variation in methyl blue adsorption/degradation. The present study reveals the importance of defects present in the mixed metal oxide composite in obtaining high-performance dye degradation/adsorption properties for sustainable wastewater treatment.

Potential of iron-based composites derived from sucrose foam for mercury removal and safe recovery

Although various methods for removal of elemental mercury from gas streams have been proposed, the control of mercury emissions to the environment from anthropogenic sources, mainly coal-fired power plants, remains unresolved in many countries worldwide. Meanwhile, the Minamata Convention and the IED of the European Commission continue to impose restrictions for its control and mitigation. In this work, a new material based on a sucrose foam impregnated with iron oxide nanoparticles has been developed for the adsorption of elemental mercury from flue gases allowing the regeneration of the material and the recovery of elemental mercury. Of the different iron oxides supported on the sucrose foam, αFe2O3 nanoneedles were found to be the most efficient in capturing mercury through a Mars-Maessen mechanism and the forming of HgO. The adsorbents developed proved to be effective in the presence of SO2 and H2O, with the O2 present in the gas playing a key role in the regeneration of the material. From the results found sucrose foam-based αFe2O3 composite could be an attractive alternative to traditional non-regenerable activated carbons, reducing costs and being environmentally sustainable.

Supramolecular photocatalyst of perylene bisimide decorated with α-Fe2O3: Efficient photo-Fenton degradation of organic pollutants

The composite of α-Fe2O3/PTCDI based on supramolecular photocatalyst of perylene bisimide (PTCDI) decorated with α-Fe2O3 was prepared via calcination of ferric nitrate with self-assembly PTCDI. The composite displayed an enhanced performance for the degradation of phenol pollutants and coking wastewater via photo-Fenton reaction relative to the single component, which owing to efficient charge transfer on the heterojunction and effective Fe3+/Fe2+ conversion. The degradation ratio of phenol by the composite catalyst was increased by 73 % and 17 % under photo-Fenton reaction compared with the constituent monomer of α-Fe2O3 and PTCDI respectively. For coking wastewater, the COD and TOC removal rates of α-Fe2O3/PTCDI were up to 66.7 % and 44.5 %. The enhanced degradation activity with photo-Fenton condition was attributed to the formed type II heterojunction between the two semiconductors, effectively inhibiting the recombination of e- and h+ and the injected electrons from PTCDI to α-Fe2O3 beneficial to the Fe3+/Fe2+ cycle, further promoting the Fenton reaction. This effective photo-Fenton degradation system shows potential application value in treatment of complex industrial wastewater.

Enhanced Photo-Fenton Activity of SnO2/α-Fe2O3 Composites Prepared by a Two-Step Solvothermal Method

The x-SnO2/α-Fe2O3 (x = 0.04, 0.07, and 0.1) heterogeneous composites were successfully prepared via a two-step solvothermal method. These composites were systematically characterized by the X-ray diffraction technique, field emission scanning electron microscopy, an energy dispersive spectrometer, X-ray photoelectron spectroscopy and a UV–visible spectrometer. It was found that SnO2 nanoparticles were uniformly decorated on the surface of α-Fe2O3 particles in these heterogeneous composites. A comparative study of methylene blue (MB) photodegradation by α-Fe2O3 and x-SnO2/α-Fe2O3 composites was carried out. All x-SnO2/α-Fe2O3 composites showed higher MB photodegradation efficiency than α-Fe2O3. When x = 0.07, the MB photodegradation efficiency can reach 97% in 60 min. Meanwhile, the first-order kinetic studies demonstrated that the optimal rate constant of 0.07-SnO2/α-Fe2O3 composite was 0.0537 min−1, while that of pure α-Fe2O3 was only 0.0191 min−1. The catalytic mechanism of MB photodegradation by SnO2/α-Fe2O3 was examined. The SnO2 can act as a sink and help the effective transfer of photo-generated electrons for decomposing hydrogen peroxide (H2O2) into active radicals. This work can provide a new insight into the catalytic mechanism of the photo-Fenton process.

Nitrogen-doped carbon dots as electron “bridge” in heterostructure of alpha-Fe2O3/NCDs/g-C3N4 for efficient degradation of indole using heterogeneous photo-Fenton

A special component, acting as “bridge” in composite photocatalyst, can remarkably improve the transfer and migration of charges by strengthening interfacial contact and constructing conductive channels. Nitrogen-doped carbon dots (NCDs) may be suitable for the bridge due to great conductivity, sufficient surface groups and more delocalized electrons. Here, we fabricated a composite of α-Fe2O3/NCDs/g-C3N4 for heterogeneous photo-Fenton degradation of indole and investigated the “bridge” roles of NCDs. Although the introduction of NCDs reduced surficial adsorption and light absorption abilities, the composite has a significant improvement in photocurrent density and EIS spectra, which were attributed to the bridge of NCDs between α-Fe2O3 and g-C3N4 through Fe-O-C and N-CN bonds. Besides, great conductivity of NCDs is another important factor for the transfer channels of charges. Finally, a Z-scheme mechanism was proposed for explanation of the transfer and migration of charges.

RGO functionalized α-Fe2O3/Co3O4 heterojunction for NO2 detection

To improve α-Fe2O3 gas sensing properties the composites of α-Fe2O3/Co3O4 heterojunction decorated with rGO were prepared via hydrothermal, chemical bath deposition (CBD) and thermal reduction methods. Structure and morphology characterizations of the as-prepared products were proved by X-ray diffraction (XRD), Raman spectra (Raman), Scanning electron microscope (SEM),Transmission Electron Microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Ultraviolet and visible spectrophotometry(UV–vis). Gas-sensing measurements revealed that the ternary composite of α-Fe2O3/Co3O4-5 min-rGO-0.15 wt% showed high response of 17.64 at 130 °C towards 2 ppm NO2, which is 6.17 times and 1.46 times higher than that of pure α-Fe2O3 (2.86) and binary composite of α-Fe2O3/Co3O4-5 min (12.16) and faster response/recovery time compared with published NO2 sensors based on α-Fe2O3. The enhanced sensing mechanism was also discussed in detail, which is attributed to the synergistic effects aroused by the as-formed p-n heterojunctions and modification of rGO. The work shed a new light to design p-n junction composites and fabricate high performance NO2 sensors.

Unused to useful: Recycling plasma chamber coated waste composite of ZnO and α-Fe2O3 into an active material for sustainable waste-water treatment

While conventional cleaning to remove the coating from plasma chamber walls becomes essential to reproduce the desired materials on the target substrate for widespread applications, an attention towards wall-deposited materials is scarce. Recycling those waste materials to value-added product is of great importance for sustainable progress of our modern society. Herein, we investigated the materials deposited on the wall of plasma chamber, explored their promising features and compared them with conventionally grown materials. A mixture of ZnO and α-Fe2O3 (ZF) exposed to high energy plasma was collected from the wall (ZF-W) and also from the substrate (ZF-S) to check the feasibility of providing same quality products. With same lattice constant of hematite, magnetite and zinc ferrites, ZF-W differs from ZF-S in coercivity, saturation magnetization, ferromagnetic stoichiometry and defects. In addition, degradation of Methyl Blue (MB) dye in ZF-W without use of any external light sources are comparable, more stable and durable in comparison to ZF-S. The slight differences obtained in the property-performances between ZF-W and ZF-S are attributed to the cationic arrangement and the oxygen vacancy defects present in the structure. The study reflects the potentiality of ZF-W as a promising active material for wastewater treatment just as one can use ZF-S. These findings clearly depict that the unused products with altered intrinsic properties obtained after plasma treatment has similar or even better potential to its actual targeted product and thus can be utilized properly thereby saving cost and time and, hence generates an unexplored direction for the materials science community.

Structural and Electrical Properties of La<sub>0.7</sub>Ca<sub>0.3</sub>MnO<sub>3</sub> /α-Fe<sub>2</sub>O<sub>3</sub> Composites

Colossal magnetoresistive (CMR) materials have huge potential in modern application and it has been widely used in magnetic sensing industry. From the literature, an incorporation of secondary insulating phase into mixed-valence manganites could improve its extrinsic effect especially low-field magnetoresistance (LFMR). However, nanoparticle addition could lead to substitution and diffusion with its parent compound. In this work, the structural and electrical properties of La0.7Ca0.3MnO3 (LCMO) were investigated by adding the α-Fe2O3 nanoparticle with ratio of 0.00, 0.05, 0.10, 0.15 and 0.20 as the artificial grain boundaries. The LCMO compound has been synthesised using sol-gel route. The samples were chosen to sinter at 800°C to obtain the pure LCMO phase by referring to the thermogravimetric analysis (TGA). The structural properties were investigated by an X-ray diffractometer (XRD) while electrical properties were measured by a four-point probe (4PP) system. XRD patterns showed the coexistence of two phases (LCMO & α-Fe2O3). LCMO crystallised in orthorhombic structure with space group Pnma while α-Fe2O3 exhibited in hexagonal form with space group R-3c. As the content of α-Fe2O3 increases, the resistivity of the samples increases drastically. Nevertheless, the addition of iron oxide has no significant effect on the metal-insulator transition temperature (T­MI). From the XRD and 4PP analysis, it can be deduced that the α-Fe2O3 nanoparticles do not react with LCMO compound and successfully formed the La0.7Ca0.3MnO3 /α-Fe2O3 composites. The resistivity increases when the nano-sized α-Fe2O3 is added into LCMO nanocomposites due to the insulator nature of α-Fe2O3.

Li2ZnTi3O8@α-Fe2O3 composite anode material for Li-ion batteries

Li2ZnTi3O8@α-Fe2O3 composites have been successfully prepared by a facile hydrothermal process. Li2ZnTi3O8/α-Fe2O3 composites show similar irregular spherical morphologies like Li2ZnTi3O8 and relatively smaller particle sizes than pristine Li2ZnTi3O8. Among all Li2ZnTi3O8/α-Fe2O3 composites, Li2ZnTi3O8/α-Fe2O3 composite (5 wt%) exhibits the best electrochemical properties. Li2ZnTi3O8/α-Fe2O3 composite (5 wt%) delivers a reversible charge capacity of 184.8 mAh g−1 even at 1000 mA g−1 after 500 cycles, while pristine Li2ZnTi3O8 only delivers a reversible charge capacity of 110.7 mAh g−1. The strong covalent bonds between Li2ZnTi3O8 and α-Fe2O3 will be formed, which is beneficial for the reduction of interfacial energy and thus helpful for the stabilization of the composite. Because of the special synergistic effect of the multi-phase interface, Li2ZnTi3O8/α-Fe2O3 composites not only possess the advantages of single components but also show novel and attractive performances, such as the enhanced ionic conductivity, reduced interfacial charge transfer impedance, improved migration rate of lithium ions, and the enhancement of the rate performance and reversible capacity. The as-prepared Li2ZnTi3O8/α-Fe2O3 composites reveal important potentials as anode materials for next-generation rechargeable Li-ion batteries, and this work also offers an effective strategy to design high performance lithium storage materials for advanced lithium-ion batteries.

Remediation Performance via the Passivation of a Porous Biomorph Genetic Composite of α-Fe2O3/Fe3O4/C Using a Bamboo Template on As(Ⅴ) Contaminated Soils

Red soil from Guangxi, China was selected as the background soil, and a porous biomorphic genetic composite of α-Fe2O3/Fe3O4/C comprising a bamboo template (PBGC-Fe/C) was used as a passivator to remediate As(Ⅴ) contaminated soils. The performance of PBGC-Fe/C was characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The results showed that PBGC-Fe/C could improve the passivation effect of As(Ⅴ) from the contaminated soils compared with a single passivation material. Under the conditions of a 5% dose addition, 25% water content, and particle size of 100 mesh, the stability rates of PBGC-Fe/C on As(Ⅴ) contaminated soils with different concentrations of 500 mg·kg-1 and 1000 mg·kg-1 could reach 80.95% and 73.49%, respectively. The porous biomorphic genetic composite of bamboo charcoal provided a large number of adsorption sites for As(Ⅴ), and the acidity of the soil was favorable for the remediation of As(Ⅴ) via passivation. Moreover, PBGC-Fe/C could not only adsorb and fix As(Ⅴ), but also promoted the stabilization of As species. Chemical complexation and ion exchange played major roles in this passivation process.

Enhanced catalytic performance with Fe@α-Fe2O3 thin nanosheets by synergistic effect of photocatalysis and Fenton-like process

Developing novel catalysts and catalysis processes are highly attractive in environmental protection and energy utilization. Photocatalysis-Fenton combinational process is an environmentally friendly technology and has broad application prospects. In this work, thin Fe@α-Fe2O3 nanosheets with thickness of 2–5 nm were designed by oxidation of Fe metal nanostructure synthesized using a modified solution reaction method. The nanosheet structure with thin thickness has short diffusion distance for the photogenerated carriers and prolongs the carriers' life. Simultaneously, the presence of Fe can reduce the resistance of system and further promote the transport and transfer of photogenerated carriers from the bulk to the surface, causing less carrier recombination and better photocatalytic performance. What's more, the Fe@α-Fe2O3 composite can induce the Fenton-like reaction to generate active •OH radicals, which significantly improve the degradation rate. The synergistic effect of photocatalysis and Fenton processes makes the system show an enhanced photodegradation performance: 96.5% of RhB is degraded after 60 min visible light irradiation, especially, 84.3% of RhB is degraded within the first 10 min, which are much higher than that of the pure α-Fe2O3 sample. This work demonstrates that the conjunction of photocatalysis and Fenton processes based on the Fe@α-Fe2O3 nanosheets provides a potential application for pollutants degradation.

Dandelion-like SiO2@SnO2/α-Fe2O3 hollow spheres formed by growing of α-Fe2O3 nanotubes on low crystalline SiO2@SnO2 and their enhanced acetone-sensing properties

Herein, dandelion-like SiO2@SnO2/α-Fe2O3 hollow microspheres with average size of 600 nm were successfully synthesized by an in-site hydrothermal method. The α-Fe2O3 nanotubes with average diameters of 30 nm were epitaxially grown on the low crystalline mesoporous SiO2@SnO2 hollow spheres. The hollow microspheres owned mesoporous structure, while the pore size and the specific surface area were 8.8 nm and 86.7 m2/g, respectively. The influence of the Fe3+ initial concentration on structure, morphology and gas-sensing property of the as-synthesized products were studied. Compared with α-Fe2O3, SiO2@SnO2, and other SiO2@SnO2/α-Fe2O3 composites, the sensor based on SiO2@SnO2/α-Fe2O3-0.15 (the concentration of Fe3+ was 0.15 μM) showed excellent gas sensitivity, which had high response value (41 towards 100 ppm acetone), faster response and recovery time (7 s and 23 s) and a lower detection limit. The remarkable improvement of gas-sensing performance could be attributed to the unique mesoporous SiO2@SnO2/α-Fe2O3 hollow structure with α-Fe2O3 nanotubes, the large specific surface area, the catalysis of α-Fe2O3 and the synergistic effect of SiO2, SnO2 and α-Fe2O3. The sensor based on dandelion-like SiO2@SnO2/α-Fe2O3 hollow microspheres would be a potential application in acetone gas detection.

Designing micro/nano hybrid TNT@[formula omitted]-Fe2O3 composites for high performance supercapacitors

In the present work, we demonstrate the supercapacitor applications of titania nanotube @α-Fe2O3 composites (TNT@α-Fe2O3) synthesized via successive anodization–hydrothermal methods. The structure and morphology of the composites were studied through XRD and SEM analyses and the electrochemical properties were studied through CV, GCD and EIS analyses. The hybrid composite, TNT-Fe4 exhibited highest supercapacitor performance with a capacitance of 157.32 mFcm−2 at a scan rate of 5 mVs−1 owing to the unique micro/nano hybrid architecture of the composite, comprising of a hierarchical layered Fe2O3 coating on titania nanotubes. The asymmetric supercapacitor fabricated with the composite electrode together with activated carbon showed an excellent capacitance of 142.86 mFcm−2 with an energy density of 38.88μWhcm−2 at 0.2 mAcm−2. The high rate capability and outstanding cyclic stability of the composite validate the potential application of the device in charge-storage systems.

Oxygen vacancy defects engineering on Ce-doped α-Fe2O3 gas sensor for reducing gases

Surface oxygen vacancy defects (OV) are regarded to be beneficial to the gas sensing behavior by significantly improving the carrier density and providing more oxygen adsorption sites. In this work, Ce-doped α-Fe2O3 composites with abundant OV defects were synthesized using an oil bath method assisted with annealing treatment. Morphological characterization results indicate that the lamellar architecture of α-Fe2O3 is transformed to nanospheres composed of massive nanoparticles with small sizes (7–9 nm) after introducing Ce elements. Gas sensing results show that the FeCe10 (Fe/Ce = 10:1) sensors exhibit enhanced acetone sensing response of 26.3–100 ppm gas at the operating temperature of 220 °C toward that of pure α-Fe2O3. Most importantly, X-ray photoelectron spectroscopy and electron spin resonance spectroscopy results confirm that the sensing responses of Ce-doped α-Fe2O3 sensors are directly related to the OV defects, that is, the larger the quantity of the OV defects, the higher the sensing response. The unpaired electrons trapped in OV defects can provide more active sites for adsorption of oxygen and acetone molecules, resulting in a thicker depletion layer and a higher potential barrier. Our work highlights the decisive role of OV defects in gas sensors, which can also provide a rational approach to boost the sensing performance.

Improving photocatalytic decomposition by MWCNT and anodized α-Fe2 O3 composite

In recent years, photocatalytic technology has received attention for environmental protection. In this study, the usefulness of iron nanostructures generated by anodization was confirmed. Moreover, the synergistic effect of anodized iron (hematite, α-Fe₂O₃) and MWCNT (multi-walled carbon nanotube) was confirmed by methylene blue (MB) decomposition by MWCNT /α-Fe₂O₃ composite material. Electrophoretic deposition(EPD) was used as a method of making the MWCNT/α-Fe₂O₃ composite material. Characterization of the anodized samples and samples after EPD was performed by SEM and XRD, and concentration measurement of MB decomposition was performed using a spectrophotometer. The MB decomposition rate was improved in all the samples with MWCNT and the highest obtained with the MWCNT/α-Fe₂O₃ sample

A facile microwave stimulated g-C3N4/α-Fe2O3 hybrid photocatalyst with superior photocatalytic activity and attractive cycling stability

In this report, we successfully fabricate the ratio-perfect g-C3N4/α-Fe2O3 hybrid nanocomposites by regulating the mass ratio between two components via a facile one step hydrothermal route. The hybrid catalysts were characterized by X-ray powder diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV–Vis diffuse reflectance spectroscopy (DRS), photoluminescence and Brunauer–emmett–teller (BET). The photocatalytic activity of g-C3N4/α-Fe2O3 for decolorization of congo-red (CR) and malachite green (MG) was evaluated. The results show that g-C3N4/α-Fe2O3 composites exhibit higher photocatalytic performance than the pure g-C3N4 under simulated visible light irradiation. The results demonstrate that g-C3N4/α-Fe2O3 with 1:2 mass ratios shows the optimal overall photocatalytic performance such as huge degradation efficiency (95%) towards MG dye. The enhanced photocatalytic activity could be due to the suited band structure and close contact interfaces between g-C3N4 and α-Fe2O3, which lead to the efficient transfer and separation of the photogenerated charge carriers. The improved photocatalytic mechanism of the hybrid g-C3N4/α-Fe2O3 hybrid catalysts was also proposed.

Synthesis of α-Fe2O3 decorated g-C3N4/ZnO ternary Z-scheme photocatalyst for degradation of tartrazine dye in aqueous media

Abstract In this study, we report the synthesis of a novel α-Fe2O3 decorated g-C3N4/ZnO (g-C3N4/ZnO@α-Fe2O3) ternary Z-scheme photocatalyst for degradation of organic dye. The g-C3N4/ZnO@α-Fe2O3 ternary nanocomposite was synthesized by using the direct pyrolysis and sol-gel methods. Different physicochemical methods were used to confirm the as-synthesized nanomaterials including Transmission electron microscopy, high-resolution field-emission scanning electron microscopy, Fourier Transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The as-synthesized different nanocomposite materials were used to investigate the photodegradation of tartrazine (Acid Yellow 23). Photoluminescence spectra revealed that the g-C3N4/ZnO@α-Fe2O3 ternary nanocomposite has lower recombination rate than pristine g-C3N4. The as-synthesized nanocomposite showed high photocatalytic activity towards degradation of tartrazine than that of g-C3N4, ZnO, ZnO@α-Fe2O3. Also, g-C3N4/ZnO@α-Fe2O3 nanocomposite can able to degrade 99.34% of tartrazine within 35 min under visible light irradiation. The g-C3N4/ZnO@α-Fe2O3 nanocomposite has a higher rate constant and excellent cyclic stability towards the photodegradation of tartrazine. The electrochemical impedance spectra results confirmed that the g-C3N4/ZnO@α-Fe2O3 nanocomposite has faster electron-transfer ability towards the electrode surface than that of g-C3N4, ZnO, and ZnO@α-Fe2O3 composite.

Facile one-step hydrothermal synthesis of α-Fe2O3/g-C3N4 composites for the synergistic adsorption and photodegradation of dyes.

With the expansion of industrialization, dye pollution has become a significant hazard to humans and aquatic ecosystems. In this study, α-Fe2O3/g-C3N4-R (where R is the relative percentage of α-Fe2O3) composites were fabricated by a one-step method. The as-prepared α-Fe2O3/g-C3N4-0.5 composites showed excellent adsorption capacities for methyl orange (MO, 69.91 mg g−1) and methylene blue (MB, 29.46 mg g−1), surpassing those of g-C3N4 and many other materials. Moreover, the ionic strength and initial pH influenced the adsorption process. Relatively, the adsorption isotherms best fitted the Freundlich model, and the pseudo-second-order kinetic model could accurately describe the kinetics for the adsorption of MO and MB by α-Fe2O3/g-C3N4-0.5. Electrostatic interaction and π–π electron donor–acceptor interaction were the major mechanisms for MO/MB adsorption. In addition, the photocatalytic experiment results showed that more than 79% of the added MO/MB was removed within 150 min. The experimental results of free-radical capture revealed that holes (h+) were the major reaction species for the photodegradation of MO, whereas MB was reduced by the synergistic effect of hydroxyl radicals (·OH) and holes (h+). This study suggests that the α-Fe2O3/g-C3N4 composites have an application potential for the removal of dyes from wastewater.

A sensitive DNAzyme-based electrochemical sensor for Pb2+ detection with platinum nanoparticles decorated TiO2/α-Fe2O3 nanocomposite as signal labels

In this work, a sensitive DNAzyme-based electrochemical sensor had been developed for Pb2+ detection with platinum nanoparticles decorated TiO2/α-Fe2O3 composite as signal labels. The morphological and compositional properties of the PtNPs/TiO2/α-Fe2O3 were examined by using transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The result showed that the shape of α-Fe2O3 nanocrystals were the cubic, the average length ranged from 150 to 300 nm, and the PtNPs with about 3–4 nm in diameter were well dispersed on the surface of TiO2/α-Fe2O3. TiO2/α-Fe2O3 were used as a “carrier” to load the PtNPs tracers as well as for Apt3 immobilization. In turn, the DNAzyme structure of Apt1 and Apt2 was immobilized on the gold electrode surface as the capture probes. Subsequently, DNAzyme modified electrodes reacted with target Pb2+ and the Apt3/PtNPs/TiO2/α-Fe2O3 composite were deposited on the electrode surface. The performance of the DNAzyme-based electrochemical sensor was tested by recording the electrocatalytic reduction current toward H2O2. Enhanced sensitivity was achieved by TiO2/α-Fe2O3 nanocomposites as a nanocarrier in order to PtNPs at a high ratio. The DNAzyme-based electrochemical sensor described here exhibited excellent sensitivity and specificity for target ion. This work represented a promising potential for on-site testing Pb2+ in real drinking water and serum sample analysis.