Debye Temperature Evaluation for Secondary Battery Cathode of α-SnxFe1-xOOH Nanoparticles Derived from the 57Fe- and 119Sn-Mössbauer Spectra.

Debye temperatures of α-SnxFe1-xOOH nanoparticles (x = 0, 0.05, 0.10, 0.15 and 0.20, abbreviated as Sn100x NPs) prepared by hydrothermal reaction were estimated with 57Fe- and 119Sn-Mössbauer spectra measured by varying the temperature from 20 to 300 K. Electrical properties were studied by solid-state impedance spectroscopy (SS-IS). Together, the charge-discharge capacity of Li- and Na-ion batteries containing Sn100x NPs as a cathode were evaluated. 57Fe-Mössbauer spectra of Sn10, Sn15, and Sn20 measured at 300 K showed only one doublet due to the superparamagnetic doublet, while the doublet decomposed into a sextet due to goethite at the temperature below 50 K for Sn 10, 200 K for Sn15, and 100 K for Sn20. These results suggest that Sn10, Sn15 and Sn20 had smaller particles than Sn0. On the other hand, 20 K 119Sn-Mössbauer spectra of Sn15 were composed of a paramagnetic doublet with an isomer shift (δ) of 0.24 mm s-1 and quadrupole splitting (∆) of 3.52 mm s-1. These values were larger than those of Sn10 (δ: 0.08 mm s-1, ∆: 0.00 mm s-1) and Sn20 (δ: 0.10 mm s-1, ∆: 0.00 mm s-1), suggesting that the SnIV-O chemical bond is shorter and the distortion of octahedral SnO6 is larger in Sn15 than in Sn10 and Sn20 due to the increase in the covalency and polarization of the SnIV-O chemical bond. Debye temperatures determined from 57Fe-Mössbauer spectra measured at the low temperature were 210 K, 228 K, and 250 K for Sn10, Sn15, and Sn20, while that of α-Fe2O3 was 324 K. Similarly, the Debye temperature of 199, 251, and 269 K for Sn10, Sn15, and Sn20 were estimated from the temperature-dependent 119Sn-Mössbauer spectra, which were significantly smaller than that of BaSnO3 (=658 K) and SnO2 (=382 K). These results suggest that Fe and Sn are a weakly bound lattice in goethite NPs with low crystallinity. Modification of NPs and addition of Sn has a positive effect, resulting in an increase in DC conductivity of almost 5 orders of magnitude, from a σDC value of 9.37 × 10-7 (Ω cm)-1 for pure goethite Sn (Sn0) up to DC plateau for samples containing 0.15 and 0.20 Sn (Sn15 and Sn20) with a DC value of ~4 × 10-7 (Ω cm)-1 @423 K. This non-linear conductivity pattern and levelling at a higher Sn content suggests that structural modifications have a notable impact on electron transport, which is primarily governed by the thermally activated via three-dimensional hopping of small polarons (SPH). Measurements of SIB performance, including the Sn100x cathode under a current density of 50 mA g-1, showed initial capacities of 81 and 85 mAh g-1 for Sn0 and Sn15, which were larger than the others. The large initial capacities were measured at a current density of 5 mA g-1 found at 170 and 182 mAh g-1 for Sn15 and Sn20, respectively. It is concluded that tin-goethite NPs are an excellent material for a secondary battery cathode and that Sn15 is the best cathode among the studied Sn100x NPs.

Photocatalytic and Cathode Active Abilities of Ni-Substituted α-FeOOH Nanoparticles.

The present study investigates the relationship between the local structure, photocatalytic ability, and cathode performances in sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) using Ni-substituted goethite nanoparticles (NixFe1-xOOH NPs) with a range of 'x' values from 0 to 0.5. The structural characterization was performed applying various techniques, including X-ray diffractometry (XRD); thermogravimetry differential thermal analysis (TG-DTA); Fourier transform infrared spectroscopy (FT-IR); X-ray absorption spectroscopy (XANES/EXAFS), both measured at room temperature (RT); 57Fe Mössbauer spectroscopy recorded at RT and low temperatures (LT) from 20 K to 300 K; Brunauer-Emmett-Teller surface area measurement (BET), and diffuse reflectance spectroscopy (DRS). In addition, the electrical properties of NixFe1-xOOH NPs were evaluated by solid-state impedance spectroscopy (SS-IS). XRD showed the presence of goethite as the only crystalline phase in prepared samples with x ≤ 0.20, and goethite and α-Ni(OH)2 in the samples with x > 0.20. The sample with x = 0.10 (Ni10) showed the highest photo-Fenton ability with a first-order rate constant value (k) of 15.8 × 10-3 min-1. The 57Fe Mössbauer spectrum of Ni0, measured at RT, displayed a sextet corresponding to goethite, with an isomer shift (δ) of 0.36 mm s-1 and a hyperfine magnetic distribution (Bhf) of 32.95 T. Moreover, the DC conductivity decreased from 5.52 × 10-10 to 5.30 × 10-12 (Ω cm)-1 with 'x' increasing from 0.10 to 0.50. Ni20 showed the highest initial discharge capacity of 223 mAh g-1, attributed to its largest specific surface area of 174.0 m2 g-1. In conclusion, NixFe1-xOOH NPs can be effectively utilized as visible-light-activated catalysts and active cathode materials in secondary batteries.

[Stability of Ferrihydrite and Goethite Nanoparticles Under Different Environmental Conditions].

Agglomeration and dispersion of nanoparticles control many important environmental processes. In this study, the particle size and zeta potential of ferrihydrite nanoparticles (FHNPs) and goethite nanoparticles (GTNPs) under different pH, ion, and organic matter conditions were measured. These data were used to calculate the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy between nanoparticles to further investigate the stability of two nanoparticles. The results showed that Na+ and Ca2+ promoted FHNPs and GTNPs agglomeration due to their ionic strength. The PO43- with low-concentration (2 mmol·L-1), humic acid and fulvic acid (2 mg·L-1 and 10 mg·L-1) loaded on iron mineral nanoparticles changed their surface charge and further improved the stability of FHNPs and GTNPs at medium and high pH. Although the PO43- with high concentration (10 mmol·L-1) also changed the electrical properties of iron mineral nanoparticles, it had little contribution to the GTNP stability due to its ionic strength. When the zeta potentials of FHNPs or GTNPs were close to 0, the primary barrier and secondary minima were nonexistent simultaneously. The two kinds of nanoparticles irreversibly agglomerated in primary minima. When the primary barrier and secondary minima coexisted, the proportion of reversible aggregation of FHNPs and GTNPs in secondary minima increased. The results provided support for further investigation of the environmental behavior of FHNPs and GTNPs, and iron mineral nanoparticle-facilitated transport of pollutants.

Zero valent iron and goethite nanoparticles as new promising remediation techniques for As-polluted soils.

The capacity of two iron-based nanomaterials, namely goethite nanospheres (nGoethite) and zero valent iron nanoparticles (nZVI), to immobilize As in a polluted soil was evaluated and compared. The composition and morphology of the products were studied by energy dispersive X-ray analysis and transmission electron microscopy, while zeta potential and average sizes were determined by dynamic light scattering. To assess As immobilization, soil subsamples were treated with nGoethite or nZVI at a range of Fe doses (0.5%, 2%, 5% and 10%) and then studied by the TCLP test and the Tessier sequential extraction procedure. The influence of both nanoparticles on As speciation was determined, as was impact on soil pH, electrical conductivity, Fe availability and phytotoxicity (watercress germination). For nZVI, notable results were achieved at a dose of 2% (89.5% decrease in As, TCLP test), and no negative effects on soil parameters were detected. Indeed, even soil phytotoxicity was reduced and only at the highest dose was a slight increase in As3+ detected. In contrast, excellent results were obtained for nGoethite at the lowest dose (0.2%) (82.5% decrease in As, TCLP test); however, soil phytotoxicity was increased at higher doses, probably due to a marked enhancement of electrical conductivity. For both types of nanoparticle, slight increases in Fe availability were observed. Thus, our results show that both nZVI and nGoethite have the capacity to effectively immobilize As in this brownfield. The use of lower doses of nGoethite emerges as a promising soil remediation strategy for soils affected by As pollution.

Synthesis of highly-specific stable nanocrystalline goethite-like hydrous ferric oxide nanoparticles for biomedical applications by simple precipitation method.

Exploration of novel types of iron oxide nanoparticles as well as novel versatile ways to prepare them in a controlled manner keeping in mind necessity of narrow size distributions and high colloidal and chemical stability is an important task for modern nanochemistry. Most of the procedures for preparation of nanocrystalline iron oxides require drastic conditions and complex mixtures of reagents, therefore there is a high demand for methods of synthesis of such nanoparticles (NPs) in mild conditions. In this study, we discovered a new way to prepare crystalline goethite-like hydrous ferric oxide (HFO) NPs by fast and simple precipitation procedure in aqueous media and probed modification strategies aimed at the development of modified HFO nanoparticles for biomedical applications, including express-diagnostics and specific cell targeting.

Microwave-Assisted Synthesis of Goethite Nanoparticles Used for Removal of Cr(VI) from Aqueous Solution.

The microwave-assisted synthesis of goethite nanoparticles has been studied. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA) and Brunauer-Emmett-Teller (BET) method. Goethite rod-like nanoparticles have been successfully synthesized in 10 min of microwave treating at 100 °C. Particle size is in the range from 30 to 60 nm in width and from 200 to 350 nm in length. BET analysis indicated that the surface area of the product is 158.31 m²g-1. The feasibility of Cr(VI) removal fromaqueous solution depends on the pH of the solution and contact time. The maximum adsorptionis reached at pH 4.0 and 540 min of contact time. The adsorption kinetics was analyzedby the pseudo-first- and second-order models and the results reveal that the adsorption process obeys the pseudo-second-order model. The adsorption data were fitted well with the Langmuir adsorption isotherm.

Acute ecotoxicity of coated colloidal goethite nanoparticles on Daphnia magna: Evaluating the influence of exposure approaches.

Synthesized iron oxide nanoparticles have been proposed as an alternative to non-dispersed iron oxides for in situ environmental remediation. Their colloidal properties enable their injection into porous media, i.e. soils and aquifers, and offer a higher efficiency in removing contaminants. However, this dispersed state is also the cause of concerns over their environmental fate and toxicity, e.g., by increasing the exposure time to aquatic organisms in groundwater remediation activities. Therefore, the objective of in situ groundwater remediation is to establish local reactive barriers in the subsurface by injection by means of reactive colloids with a controllable mobility under in situ conditions and present as colloids as shortly as possible. In this work, we examined the toxicity of humic acid-coated colloidal goethite nanoparticles in Daphnia magna. The adaptation of the ecotoxicological standard tests for nanomaterials is intensely discussed to increase comparability and reliability of results. In the present study, the effect of different exposure conditions on goethite nanoparticles colloidal behaviour and acute Daphnia immobilization effects was investigated. For this purpose, iron concentration in the water column, aggregation state and acute effects were studied in: i) a standard test, ii) test design with exposure dispersions incubated for a week and iii) water accommodated fraction. Despite the different aggregation and settling of the particles found between the approaches tested, no differences in toxicity were observed. Coated nanoparticles were found clogging up the filtering apparatus, and/or adhered to the exoskeleton, hindering the swimming and molting, and causing the immobilization and death of the organisms at doses of ≥943mg/L (EC50). The data suggests that the toxic potential of these nanoparticles is mainly related to the physical interaction with the daphnids.