γ-Fe2O3 Nanoparticles Research Articles

Tuning the Fe-Gd nanoparticles co-functionalized mesoporous carbon from sphere to nanobowl for advanced bioapplications

Studies on the function-integrated nanocomposites with well-tuned morphologies have received considerable interest. Here, we reported the preparation of mesoporous carbon nanobowl integrated with stoichiometric γ-Fe2O3 and GdPO4 nanoparticles (Fe-Gd/MCN-B) for morphological advantage exploration. Followed by (i) emulsion-induced interface anisotropic assembly of polydopamine, (ii) solvent evaporation-induced sorption of Wells-Dawson-like heterometallic cluster of {Fe6Gd6P6} and (iii) temperature-programmed carbonization, Fe-Gd/MCN-B with the size around 200 nm was isolated. Our in-vitro studies revealed that Fe-Gd/MCN-B showed a 63.0 % amplified photoacoustic (PA) signal intensity as compared with its nanospherical analogue of Fe-Gd/MCN-S owing to the enhanced light harvesting and photothermal conversion on the interface of its nanobowl morphology. Furthermore, the combined magnetic resonance (MR) imagining, drug delivery and photothermal treatment efficacy in Fe-Gd/MCN-B were also validated in-vitro. These results demonstrated that the delicate design of the morphology of function-integrated nanocomposites is an available way for enhanced imaging performance.

Non-exchange bias hysteresis loop shifts in dense composites of soft-hard magnetic nanoparticles: New possibilities for simple reference layers in magnetic devices

Exchange bias has been extensively studied in both exchange-coupled thin films and nanoparticle composite systems. However, the role of non-exchange mechanisms in the overall hysteresis loop bias is far from being understood. Here, dense soft-hard binary nanoparticle composites are used not only as a novel tool to unravel the effect of dipolar interactions on the hysteresis loop shift but also as a new strategy to enhance the bias of any magnet exhibiting an asymmetric magnetization reversal. Mixtures of equally sized, 6.8 nm, soft maghemite (γ-Fe2O3) nanoparticles (no bias—symmetric reversal) and hard cobalt doped γ-Fe2O3 nanoparticles (large exchange bias—asymmetric reversal) reveal that, for certain fractions of soft particles, the loop shift of the composite can be significantly larger than the exchange-bias field of the hard particles in the mixture. Simple calculations indicate how this emerging phenomenon can be further enhanced by optimizing the parameters of the hard particles (coercivity and loop asymmetry). In addition, the existence of a dipolar-induced loop shift (“dipolar bias”) is demonstrated both experimentally and theoretically, where, for example, a bias is induced in the initially unbiased γ-Fe2O3 nanoparticles due to the dipolar interaction with the exchange-biased hard nanoparticles. These results open a new paradigm in the large field of hysteresis bias and pave the way for novel approaches to tune loop shifts in magnetic hybrid systems beyond interface exchange coupling.

Effects of foliar and root application of Zn and Fe bio-nanofertilizers on the glucosinolate, Zn and Fe contents of Pak choi (Brassica rapa Subsp. Chinensis) grown under hydroponic and pot cultivation

Pak choi is a rich source of minerals and health beneficial compounds such as glucosinolates (GSLs). This study is focused on implementing sustainable agronomic approaches to optimize pre-harvest cultivation and improve plant growth and nutritional value. Therefore, the aim of this work was to evaluate the effect of foliar and root fertilization of algae capped ZnO and γ-Fe2O3 nanoparticles on the growth and content of GSLs, Zn and Fe of Pak choi grown under hydroponic floating system and pot conditions. The foliar application of ZnO (77 nm) and γ-Fe2O3 (68 nm) nanoparticles functionalized with an Arthrospira platensis extract increased fresh weight (39.71 %), plant height (42.77 %), leaves number (26.47 %), root length (33.33 %), and Zn (10-fold) and Fe (2-fold) contents in hydroponic plants. The same treatment also improved plant fresh weight (31.73 %), and Zn (6-fold) and Fe (2-fold) in pot cultivated Pak choi. Six GSLs were detected, which were also enhanced by the joint application of nanoparticles and microalgae extract. The results revealed a high synergy between the ZnO- and γ-Fe2O3 nanoparticles and the A. platensis extract to increase plant growth and Zn and Fe micronutrients and glucosinolates in Pak choi grown under hydroponic and pot systems.

Enhanced performance of aerobic granular sludge-membrane system through the utilization of different iron-based nano-metal oxides for mitigating membrane fouling

Fe3O4, γ-Fe2O3, and α-Fe2O3 nanoparticles play a crucial role in influencing the adsorption capacity and pretreatment efficacy as iron-based nano-metal oxides due to their distinct structural and physicochemical properties. However, the impact of these adsorbents on membrane filtration efficiency remains unexplored. This study aimed to investigate the influence of these three adsorbents on membrane fouling in an aerobic granular sludge–membrane system (AGSMS) used for municipal wastewater reuse treatment. The results demonstrated that under optimal conditions, γ-Fe2O3 exhibited superior effectiveness in removing low and medium molecular weight contaminants from wastewater, resulting in a higher normalized flux (0.59) and reduced total fouling resistance (2.66 × 1011 m−1). It also showed the highest removal rate for organic matter and suspended solids, making it particularly effective in mitigating AGSMS membrane fouling. However, excessive addition (2 g/L) of Fe3O4, γ-Fe2O3, and α-Fe2O3 could potentially hinder the proper operation of the AGSMS. Pre-adsorption facilitated the formation of a porous cake layer while inhibiting standard blocking behavior. Additionally, the extended Derjaguin–Landau–Verwey–Overbeek theory analysis revealed a substantial energy barrier between membrane-foulant interactions (125.65 kT) as well as foulant-foulant interactions (62.06 kT) within the γ-Fe2O3 system, confirming its exceptional antifouling characteristics. This study offers valuable insights into the selection of iron oxide adsorbents for membrane fouling mitigation and wastewater reuse.

Medium scale-up synthesis of nanomaghemite as an inhibitor of cadmium uptake in seedlings of Theobroma cacao L

The aim of this research was to show that the absorption of divalent cadmium ions (Cd2+) in Theobroma cacao L. seedlings can be controlled and adjusted by remediation with maghemite (γ-Fe2O3) nanoparticles (NPs), i.e., leading to the low tolerance limits established by the European Union (EU) in 2014 for Cd in products made from cocoa. The research had two stages; the first one involved the medium scale synthesis of 92 g of 15 nm γ-Fe2O3 NPs via room temperature chemical co-precipitation of ferrous salts and their characterizations using diverse physicochemical techniques. In the second stage, and for the first time, three doses of these γ-Fe2O3 NPs (1, 2, and 4 g) were applied to the substrate of cocoa seedlings of genotypes ICS 39, ICS 95, and CCN 51 for three months of exposure. A morphological analysis revealed non-significant toxic effects on the seedlings’ height, leaf area, and stem diameter among the genotypes and tested doses. The results of the atomic absorption analysis of the treatment with 4 g of γ-Fe2O3 NPs showed a concentration of 0.10 mg kg−1 of Cd2+, a limit lower than the control and the recommended value by the 2014 EU regulation. Thus, the transport and/or absorption of the Cd2+ toxic metal were significantly inhibited, since up to 74 % of Cd2+ uptake in the genotype ICS 95 was experimentally observed. Also, the environmental Fe-dynamics in the seedlings and soils demonstrated no transport of γ-Fe2O3 NPs to the seedlings. Thus, the study found that the Cd2+ adsorption in remediated soil using γ-Fe2O3 NPs involves three steps: electrostatic exchange, Fe-oxide adsorption, and substrate-γ-Fe2O3 NPs complexation and precipitation.

Seaweed assisted preparation of Fe2O3 nanoparticles and their antiviral studies against White Spot Syndrome Virus (WSSV): In vitro and in silico approach.

In the present study, preparation of Fe2O3 nanoparticles using seaweed Sargassum swartzii extract and characterized using XRD, FTIR, and FE-SEM with EDAX analysis. The crystalline nature of γ-Fe2O3 nanoparticles (hematite powders) were confirmed using XRD. In FT-IR spectra of the Fe2O3 nanoparticles, the major bands at 594 cm−1 and 461 cm−1 observed correspond to the metal‑oxygen (FeO) vibrational modes. The surface morphology of Fe2O3 nanoparticles has been studied by FE-SEM. In vitro toxicity and anti-WSSV activity of Fe2O3 nanoparticles were carried out using the shrimp-insect hybrid cell line (PmLyo-Sf9). The bioactivity of Fe2O3 nanoparticles against the WSSV infected with the PmLyo-SF9 cell line was analyzed through dose-dependent attachment inhibition and virucidal activity at an optimum concentration of 320 μg/mL and confirmed by the expression of viral envelope protein VP28. Further, the computational approach of VP28 envelope protein and Fe2O3 binding affinity was confirmed using molecular docking studies. Hence, the Fe2O3 nanoparticles can be formulated as an anti-viral agent against the aquaculture pathogens in efficient disease control.

Chiral Effect on the Electrochemistry of Magnetic Ferrite Colloidal Nanocrystal Assembly Modified by Amino Acids.

Chirality on the molecular or nanometer scale is particularly significant in chemistry, materials science, and biomedicine. Chiral electrochemical reactions on solid surfaces are currently a hot research topic. Herein, a chiral solid surface is constructed in aqueous solutions by mixing chiral molecules, d- and l-glutamic, with γ-Fe2O3 and Fe3O4 nanoparticles (NPs) and MnFe2O4 colloidal nanocrystal assembly (CNA). Cyclic voltammetry and differential pulse voltammetry measurements are conducted in a phosphate buffer solution (PBS) containing ascorbic acid (AA) or isoascorbic acid (IAA), and a chiral effect appears on the electroreduction of ferric ions of amino acid-modified magnetic samples. A negative or positive potential shift is observed, respectively, for magnetic structures modified by l- and d-glutamic acid in aqueous AA electrolyte, while the opposite is observed for these samples in IAA electrolyte. The reduction peak current increases by 0.8-1.2 times for the electrodes modified with l- and d-glutamate molecules, improving the electron transport efficiency. The chiral effect is absent when the electrolytes contain achiral uric acid or dopamine, or even chiral l-/d-/ld-tartaric acid. The chiral recognition between d-/l-glutamic acid and AA/IAA at the electrochemical interface is suggested to be related to their spinal configurations. These observations will be helpful for the rational design of inorganic functional chiral micro/nanostructures.

Photocatalytic degradation of ternary dye mixture using RGO, γ-Fe2O3 and ZnO based binary and ternary nanocomposites

In this work, we report on the improved photocatalytic degradation of a ternary dye mixture of Malachite green (MG), Methyl orange (MO), and Rhodamine B (RhB), by RGO-based binary (RGO/γ-Fe2O3) and ternary (RGO/γ-Fe2O3/ZnO) nanocomposites (NCs). These NCs are synthesized with a green, facile, and rapid microwave irradiation route using Mangifera Indica leaf extract as a reducing agent. X-ray diffraction (XRD) and scanning electron microscopy (SEM) give clear insight into the phase purity and uniform growth of γ-Fe2O3 and γ-Fe2O3-ZnO nanoparticles over the RGO sheets which confirms the reduction of iron and zinc precursors, and graphene oxide via Mangifera to form NCs. The binary and ternary NCs show 100 % degradation of ternary dye mixture in 40 min and 21 min, respectively, under UV irradiation. UV–Visible spectra confirm a reduced energy band gap, 1.96 eV for ternary NCs, and 2 eV for binary NCs as compared to 2.3 eV for γ-Fe2O3. The reduction in band gap and synergism amid RGO and nanoparticles of γ-Fe2O3 and ZnO presents that suppressed charge carrier recombination, enhanced charge carrier lifetime, improved interfacial charge transfer and availability of more active sites in RGO/γ-Fe2O3/ZnO ternary NCs are responsible for highly efficient photocatalytic activities. Reaction kinetics analysis reveals the suitability of the pseudo first-order kinetics and Freundlich model for dye degradation.

CHF Enhancement by γ-Fe2O3 Nanofluids with Pool Boiling Condition on a Downward-Facing Plane

In this study, the heat transfer performance of γ-Fe2O3 nanofluid is investigated. The particle size used in the experiment was about 20 nm. It was found by X-ray diffraction that it was consistent with the characteristic peak and no other impurities. Nanofluids with different concentrations were configured through a two-step method. Since the γ-Fe2O3 nanoparticles are not easily dispersed, the ultrasonic time was relatively long. After a series of experiments and data processing, we could see that nanofluids have the best heat transfer performance at 0.07 g/L. Compared to a reverse-osmosis (R·O) water case, the enhancement of critical heat flux (CHF) was about 34.09%, and the heat transfer coefficient enhancement was about 49.32%. The movement of bubbles during the experiment was recorded and analyzed. Compared with the R·O water case, the bubbles were larger and fewer in the nanofluid case, and what is more, the bubble movement was relatively intense. The heating surface was characterized after the experiment, and it was found that the wettability of the heating surface was changed, and the roughness of the heating surface decreased. Scanning electron microscopy showed that the deposition of the nanoparticles on the heating surface was the main cause of CHF enhancement. When the concentration was 0.08 g/L, CHF decreased, mainly because the excessive deposition of the nanoparticles increased the thermal resistance of the heating surface and led to the deterioration of heat transfer.

Unravelling the efficacy of pencil graphite anode decorated with PdCu@γ-Fe2O3 nanoparticles in the electro-oxidation of amoxicillin: Insights into kinetics, oxidative pathways and toxicity evaluation

Indiscriminate use of antibiotics has resulted in the occurrence of antibiotic residues in sediments, water bodies and industrial sewage, causing ill effects on aquatic organisms and humans. Electrochemical oxidation process via in-situ generation of strong oxidant •OH is the promising method for the removal of pollutants. In this work, PdCu/γ-Fe2O3 NPs electrodeposited pencil graphite electrode (PdCu/γ-Fe2O3@PGE) has been projected as a cost-effective anode for electro-oxidation of amoxicillin (AMX), while bare PGE was used as a cathode to generate H2O2. The electrochemical measurements showed that PdCu/γ-Fe2O3 @PGE exhibited lower ΔEp (0.191 V), high electrochemical active surface area (ECSA) (0.4620 cm2), higher oxygen evolution potential (OEP) (1.72 V), and lower charge transfer resistance of 9.747 Ω/ cm2 which was ideal for electro-oxidation of AMX. Under the optimum reaction conditions (I = 0.2 mA, pH = 4), the % AMX removal reached 90.5 % after 50 min of electro-oxidation in 0.5 M NaCl. •OH, H2O2, and HOCl were found to be the in-situ generated oxidants. The AMX solution after electro-oxidation did not exhibit antibacterial activity. The toxicity of the formed intermediates were evaluated using Toxicity Estimation Software Tool (T.E.S.T) and found to be less toxic. The electrical energy consumption was estimated to be 0.786 kWhm−3.Thus, modified PGE finds application in the remediation of effluents containing amoxicillin.

The electrical transport property and gas detection behaviour of polyvinyl alcohol and γ-Fe2O3 nanocomposite film

This paper presents the electrical and gas detection behaviour of polyvinyl alcohol (PVA)/γ-Fe2O3 nanocomposite films. The physical characterization includes X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and UV–Visible spectroscopy. The analysis of both the dc resistivity and ac conductivity using Correlated Barrier Hoping (CBH) conduction process shows that the conductivity enhances with the decreasing of activation energy in case of the PVA/γ-Fe2O3 nanocomposite film which is the indication of interfacial defect states. The current voltage study at various temperatures follows the thermoionic emission model of Schottky Barrier diode. Moreover, the dielectric constant enhances for PVA/γ-Fe2O3 nanocomposite film, which indicates homogeneous distribution of γ-Fe2O3 nanoparticles within PVA matrix and the aggregation of trapped charges found in interface develops an interfacial polarization. As a result, the gas adsorption capacity of the nanocomposite film increases which improves the signal-to-noise ratio, leading to higher gas detection sensitivity.

Influence of γ-Fe2O3 Nanoparticles Added to Gasoline–Bio-Oil Blends Derived from Plastic Waste on Combustion and Emissions Generated in a Gasoline Engine

The environmental pressure to reduce the use of fossil fuels such as gasoline generates the need to search for new fuels that have similar characteristics to conventional fuels. In this sense, the objective of the present study is the use of commercial gasoline in mixtures with pyrolytic oil from plastic waste and the addition of γ-Fe2O3 nanoparticles (NPs) in a spark ignition engine to analyze both the power generated in a real engine and the emissions resulting from the combustion process. The pyrolytic oil used was obtained from thermal pyrolysis at low temperatures (450 °C) of a mixture composed of 75% polystyrene (PS) and 25% polypropylene (PP), which was mixed with 87 octane commercial gasoline in 2% and 5% by volume and 40 mg of γ-Fe2O3 NPs. A standard sample was proposed, which was only gasoline, one mixture of gasoline with bio-oil, and a gasoline, bio-oil, and NPs mixture. The bio-oil produced from the pyrolysis of PS and PP enhances the octane number of the fuel and improves the engine’s power performance at low revolutions. In contrast, the addition of iron NPs significantly improves gaseous emissions with a reduction in emissions of CO (carbon monoxide), NOx (nitrogen oxide), and HCs (hydrocarbons) due to its advantages, which include its catalytic effect, presence of active oxygen, and its large surface area.

Synthesis and Characterization of Maghemite Nanoparticles Functionalized with Poly(Sodium 4-Styrene Sulfonate) Saloplastic and Its Acute Ecotoxicological Impact on the Cladoceran Daphnia magna.

Using a modified co-precipitation method, 11(2) nm γ-Fe2O3 nanoparticles functionalized with PSSNa [Poly(sodium 4-styrenesulfonate)] saloplastic polymer were successfully synthesized, and their structural, vibrational, electronic, thermal, colloidal, hyperfine, and magnetic properties were systematically studied using various analytic techniques. The results showed that the functionalized γ-Fe2O3/PSSNa nanohybrid has physicochemical properties that allow it to be applied in the magnetic remediation process of water. Before being applied as a nanoadsorbent in real water treatment, a short-term acute assay was developed and standardized using a Daphnia magna biomarker. The ecotoxicological tests indicated that the different concentrations of the functionalized nanohybrid may affect the mortality of the Daphnia magna population during the first 24 h of exposure. A lethal concentration of 533(5) mg L-1 was found. At high concentrations, morphological changes were also seen in the body, heart, and antenna. Therefore, these results suggested the presence of alterations in normal growth and swimming skills. The main changes observed in the D. magna features were basically caused by the PSSNa polymer due to its highly stable colloidal properties (zeta potential > -30 mV) that permit a direct and constant interaction with the Daphnia magna neonates.

Harnessing the power of multifunctional γ-Fe2O3@CuO nanocomposites: Effective extraction of heavy metals and bacterial pathogens from contaminated water

Waterborne diseases and carcinogenic effects associated with heavy metal poisoning have drawn considerable attentionto removing heavy metals from contaminated water and killing disease-causing bacteria. In this regard, γ-Fe2O3 nanoparticles (NPs) were synthesized by ion reduction method, while CuO NPsand γ-Fe2O3–CuO nanocomposites (NCs) by hydrothermal method. XRD, FTIR, FESEM, EDX and UV–visible spectroscopy were used for system characterization. The dumbbell shape of CuO NPs and spherical shape of γ-Fe2O3 NPs and γ-Fe2O3@CuO NCs were indicated via SEM analysis. The elemental composition and successful synthesis of γ-Fe2O3@CuONCs were confirmed by EDX results. The order for elemental composition: O > Cu > Fe showed the higher content ratio of Cu and O while Fe has the lowest content. The antibacterial activities against E. Coli and B. subtili were evaluated by Minimum Inhibitory Concentration (MIC) and Zone of Inhibition. γ-Fe2O3@CuO NCs showed excellent antibacterial performance as compared to γ-Fe2O3 NPs,CuO NPs, commercial Cu NPs and Cu salt. The drastic improvement in properties of γ-Fe2O3@CuO NCs resulted in better surface contact and extensive cell membranes rupture to eliminate bacterial pathogens present in wastewater Batch adsorption experiments were performed for selective removal of toxic Pb2+ ionsexisting in polluted water. The greatest adsorption capacity was determined to be 346 mg/g, and the highest removal percentage of 95 % was achieved at pH 4 in 60 min. Isotherm models and kinetic studies indicated that Pb2+ ions followed pseudo-second-order kinetics. The results obtained from batch adsorption experiment revealed γ-Fe2O3@CuO NCs as effective nanosorbent for quick elimination of toxic metal ions from industrial wastewater.

Extraction of gamma iron oxide (γ-Fe2O3) nanoparticles from waste can: Structure, morphology and magnetic properties

In this work, the transformation of waste iron cans to gamma iron oxide (γ-Fe2O3) nanoparticles following acid leaching precipitation method along with their structural, surface chemistry, and magnetic properties was studied. Highly magnetic iron-based nanomaterials, maghemite with high saturation magnetization have been synthesized through an acid leaching technique by carefully tuning of pH and calcination temperature. The phase composition and crystal structure, surface morphology, surface chemistry, and surface composition of the synthesized γ-Fe2O3 nanoparticles were explored by X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDS). The XRD results confirm the cubic spinel structure having crystallite size 26.90–52.15 nm. The XPS study reveals the presence of Fe, O element and the binding energy of Fe (710.31 and 724.48 eV) confirms the formation of γ-Fe2O3 as well. By dynamic light scattering (DLS) method and zeta potential analyzer, the particle size distribution and stability of the systems were investigated. The magnetic behavior of the synthesized γ-Fe2O3 nanoparticles were studied using a vibrating sample magnetometer (VSM) which confirmed the ferrimagnetic particles with saturation magnetization of 54.94 emu/g. The resultant maghemite nanoparticles will be used in photocatalysts and humidity sensing. The net impact of the work stated here is based on the principle of converting waste into useful nanomaterials. Finally, it was concluded that our results can give insights into the design of the synthesis procedure from the precursor to the high-quality gamma iron oxide nanoparticles with high saturation magnetization for different potential applications which are inexpensive and very simple.

Enhancing the MRI contrast and hyperthermic properties of magnetic nanoflowers by modulating magnetisation dynamics using poly(butyl cyanoacrylate) shells: Towards multi-functional clinical carriers

Magnetic-polymeric complexes have strong potential as theranostic tools; when prepared as stable suspensions in the nano-range they are functionalisable carriers which can provide MRI (magnetic resonance imaging) tracking, static-field targeting and localised hyperthermia (on AC-field irradiation). In this work the effect of the polymer layer thickness on the MRI and hyperthermic efficacies, in clinically relevant ranges, for poly(butyl cyanoacrylate) encapsulated multi-domain γ-Fe2O3 nanoparticles was investigated for the first time. A series of nanocomposites were prepared at varying particle/polymer ratios revealing that progressively thicker polymer shells maximised the carrier potential and improved the MRI and hyperthermic efficacy due to enhancement of the Néel and partial suppression of the Brownian contribution to the dynamics of the magnetic moments. The implications for the development of multifunctional theranostic agents with optimised efficacy for AC-field triggered release are discussed.

Preparation of Peptide-Based Magnetogels for Removing Organic Dyes from Water.

Water pollution by organic dyes represents a major health and environmental issue. Despite the fact that peptide-based hydrogels are considered to be optimal absorbents for removing such contaminants, hydrogel systems often suffer from a lack of mechanical stability and complex recovery. Recently, we developed an enzymatic approach for the preparation of a new peptide-based magnetogel containing polyacrylic acid-modified γ-Fe2O3 nanoparticles (γ-Fe2O3NPs) that showed the promising ability to remove cationic metal ions from aqueous phases. In the present work, we tested the ability of the magnetogel formulation to remove three model organic dyes: methyl orange, methylene blue, and rhodamine 6G. Three different hydrogel-based systems were studied, including: (1) Fmoc-Phe3 hydrogel; (2) γ-Fe2O3NPs dispersed in the peptide-based gel (Fe2O3NPs@gel); and (3) Fe2O3NPs@gel with the application of a magnetic field. The removal efficiencies of such adsorbents were evaluated using two different experimental set-ups, by placing the hydrogel sample inside cuvettes or, alternatively, by placing them inside syringes. The obtained peptide magnetogel formulation could represent a valuable and environmentally friendly alternative to currently employed adsorbents.

Stabilization of γ-Fe2O3 nanoparticles to heat by doping Nb and its property studied by Mössbauer spectroscopy

Nb5+-doped γ-Fe2O3 was synthesized by sol–gel method followed by calcination at various temperatures from 200 to 700 °C, analyzed using Powder X-ray Diffraction (PXRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS) and Mössbauer Spectroscopy. PXRD results show the formation of γ-Fe2O3 at 300 °C and it begins to transform to α-Fe2O3 at 350 °C for pure and 2 at.% Nb-doped samples. As the Nb doping increases (≥3.8 at.%), the transformation was suppressed up to 600 °C. TEM EDS confirms the incorporation of Nb to γ-Fe2O3 lattice in 9.1 at.% Nb sample calcined at 500 °C. At elevated temperature of 700 °C, γ-Fe2O3 went through full transformation to α-Fe2O3 by expelling large amount of Nb to the surface forming FeNbO4. TEM EDS confirms the compositional change during this process with reduced Nb content in α-Fe2O3 and Nb-rich nanoparticle on the surface of α-Fe2O3. Superparamagnetic properties were observed for Mössbauer spectra when the Nb doping increased, which is caused by decreased particle size. The slight increase in internal magnetic field also indicated the transformation from γ-Fe2O3 to α-Fe2O3. High Nb doping with 20 and 40 at.% shows the formation of FeNbO4 at lower temperature where limited or almost no Nb substitution in α-Fe2O3 was detected by EDS.

Engineering metal oxide heterostructures derived from MOFs/MXene hybrids as efficient acetone sensor

Acetone, one of the most used solvents in industry and the laboratory, can anesthetize the central nervous system of humans and cause damage to the kidneys, pancreas, and liver. For the purpose of monitoring the leakage and concentration of acetone, α-/γ-Fe2O3/TiO2-X (α-/γ-Fe2O3-X) materials were successfully manufactured by in-situ solvothermal and calcination processes. Here, MIL-100-derived porous α-/γ-Fe2O3 and TiO2 nanoparticles are uniformly grown on the self-sacrificial template of exfoliated Ti3C2Tx nanosheets (ex-Ti3C2Tx) that simultaneously serve as the Ti source. The heterostructure between TiO2 and Fe2O3 therein is conducive to carrier transfer and sharp resistance change. And bulk resistance-controlled γ-Fe2O3 is able to raise the response to gas. Besides, the porous structure of α-/γ-Fe2O3-X could create plenty of oxygen vacancies and surface functional groups, which facilitate diffusion and contact interaction between acetone and active sites. Accordingly, the α-/γ-Fe2O3-X endow exceptional response (R = 105.5) towards 100 ppm acetone at 240 ℃, fast response/recovery time, outstanding selectivity and stability. To further substantiate this promotion mechanism, density functional theory (DFT) calculations were carried out for investigating the adsorption behavior of α-/γ-Fe2O3-X for acetone.

Powering of IOTs through single jersey wearable tribo-electric nano generator

A simple, lightweight, and easy to develop Single Jersey Wearable Tribo-Electric Nano Generators (SJ-WTENG) were constructed using Cotton and Acrylic fabrics (Triboelectric series materials). Fabrics were also coated with Maghemite (γ-Fe2O3) nanoparticles (13 nm) to increase the electrical conductance of the samples. Compression and Vertical contact-separation modes were adopted for studying the performance of the developed samples. Along with a Single WTENG sample, the outputs of two samples connected in series were also measured. To study the effect of developed Maghemite (γ-Fe2O3) nanoparticle coating, non-coated fabrics WTENGs were also constructed and tested. The maximum voltage reached with the Maghemite (γ-Fe2O3) nanoparticle-coated SJ-WTENG samples was a time-varying signal of 7.68 volts peak to peak volts with an approximate frequency of 50.5 Hertz. A shotky diode-based full bridge rectifier was used to get the DC voltage. The rectified DC signal was observed to be 5 volts which was enough to light up an LED with a threshold voltage of 1.7 volts DC as well as charge 3.7 volts, 3.6Ah Li-ion battery pack. Results confirmed that the application of Maghemite (γ-Fe2O3) nanoparticles was useful in augmenting the output of the proposed SJ-WTENG design. The proposed system can be used to power the battery powered IOT (Internet of Things) devices, widely used in medical and body sensor network applications.