FexOy Nanoparticles Research Articles

Sustainable synthesis of ZnO and FexOy nanoparticles and their nanocomposite ZnFe2O4: Comprehensive characterization and applications in antioxidant activity and antibiotics degradation efficiency

This study focuses on developing and evaluating eco-friendly nanoparticles, specifically FexOy NPs, ZnO NPs, and a ZnFe2O4 nanocomposite (NC), for potential applications in environmental remediation and biomedicine. The nanoparticles were synthesized and characterized using X-ray diffraction (XRD), which revealed their crystalline structures with sizes of 20.3 nm for FexOy NPs, 22.1 nm for ZnO NPs, and 10.9 nm for ZnFe2O4 NC. Fourier-transform infrared (FTIR) spectroscopy identified functional groups, while UV–visible spectroscopy determined band gap energies of 2.35 eV, 3.38 eV, and 2.68 eV for FexOy NPs, ZnO NPs, and ZnFe2O4 NC, respectively. Morphological analysis via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that FexOy NPs have cubic, hexagonal, and tetragonal forms, ZnO NPs are hexagonal nanorods, and ZnFe2O4 NC has a hexagonal-faced cubic structure. Antioxidant activity, assessed through the DPPH assay, revealed that ZnFe2O4 NC had the highest potency. Additionally, under sunlight irradiation, ZnFe2O4 NC demonstrated superior degradation of the antibiotic cephalexin (96 % within 30 min) compared to FexOy NPs (58.2 %) and ZnO NPs (52 %), with respective kinetic rate constants of 0.109 min−1, 0.029 min−1, and 0.025 min−1. These results highlight the nanoparticles’ potential for environmental and biomedical applications.

Sol-Gel-Derived Functional Coatings for Pre-Sowing Seed Treatment

The superatomic structure of film-forming sols obtained by the acid hydrolysis of tetraethoxysilane (TEOS) in an aqueous medium (free of organic solvents) was studied using the SAXS method. The formation of nanoparticles (NPs) was confirmed in alcohol-free silica sols with both a low (1 vol. %) content of TEOS and a high (10 vol. %) content of TEOS, hydrolyzed in an aqueous-alcoholic medium. A trimodal size distribution was revealed for the resulting NPs, with radii ranging from less than 1 nm to ~11 nm. The volume fraction of NPs tends to grow with increases in TEOS concentration, as well as with the introduction of magnetic NPs of iron oxides into silica sols. The synthesized silica sols and suspensions based on silica sols with FexOy NPs were used for the pre-sowing treatment of white and cauliflower cabbage seeds in order to provide a functional coating on their surfaces, thereby improving seed germination, stimulating their growth in the early stages of development, and suppressing the effect of phytopathogens. The effect of the pre-sowing seed treatment in sol-gel compositions on seed germination and the growth characteristics of plant seedlings is analyzed, including the influence of iron-oxide magnetic NPs’ compositions and concentrations in silica sols.

FexOy Nanoparticles Doped Spinel Nickel Aluminate as Partial Oxidation Catalyst: Synthesis, Characterization and Catalytic Evaluation

FexOy Nanoparticles Doped Spinel Nickel Aluminate as Partial Oxidation Catalyst: Synthesis, Characterization and Catalytic Evaluation

Incorporation of FexOy nanoparticles into 3D interlinked porous carbon nanofiber networks to synergistically enhance the electrical insulation, electromagnetic wave absorbing/shielding performance and thermal conductivity

The property incompatibility among heat conduction, electromagnetic wave (EMW) absorption/shielding, and electrical insulation has restricted the synchronous enhancement and application of polymer-based composites. Herein, we first synthesized porous 3D interlinked C nanofiber/FexOy (CNF/FexOy) wafers for significantly enhanced properties by a simple sol–gel and annealing route. The texture, composition, defects and the resulting properties can conveniently be manipulated via altering Fe3+ concentration and annealing temperature. The CNF/FexOy wafers exhibit a high heat conductivity (3.22 W/mK) at a low loading (30 wt%) thanks to the shorter continuous thermal transfer paths and the increased phonon mean free path and thermal capacity of phonons per volume. Moreover, CNF/FexOy wafers possess a wide absorption band (9.36 GHz), prominent EMI shielding effectiveness (SET ≥ 20 dB over C, X, and Ku bands), excellent electrical insulation (σ = 0.00991 S/m), and enhanced mechanical/hydrophobicity properties, surpassing most reported fillers. These enhancements could be explained by the fact that the cooperative action of porous structures, defects, and magnetic/dielectric FexOy hinder electron migration and improve the impedance matching and multiple-scattering of materials. The silicone composites supported by 3D interlinked CNF/FexOy wafers have great potential as a filler with high-performance EMI shielding/absorption and thermal control in next-generation flexible electronics.

One-pot synthesis of FexOy nanoparticles embedded within N-doped carbon layers as highly efficient and selective catalysts for the hydrogenation of nitroarenes

Inhibiting the side reactions while promoting hydrogenation are the main target for the production of functional anilines from nitroarenes; consequently, the preparation of an ideal catalyst to improve chemical selectivity is one of the hot issues. In this work, we provided an easy-to-prepare catalyst with N-doped carbon layers, where the FexOy nanoparticles were encapsulated and distributed uniformly. The structural features of catalyst were characterized by several techniques, and the selected catalyst was next applied to the hydrogenation of nitrobenzene under varied conditions, involving temperature, holding period and H2 pressure. Subsequently, we conducted the synthesis of more than 16 substrates for the corresponding anilines with varied functional groups. The hydrogenation protocol to gram-scale synthesis as well as lifecycle performance were also demonstrated in the batch reactor, together with the explanation of its catalytic mechanisms. Overall, the present work provides an available preparation of simple but highly efficient catalysts for the production or aromatic amines, which will be benefit for the sustainable development of this field in near future.

The Potentiometric determination of fluoride in various brands of toothpaste

The potentiometric analysis of the fluoride content (as F-ion) in toothpaste suspension with an ion-selective fluoride electrode is simple, reliable and inexpensive. Very low fluoride ion concentrations (up to 10–5 mol / l) can be determined with a fluoride-selective electrode, whereby the ionic strength of a solution is regulated and the concentration of hydroxide ions and interfering metal ions is controlled. The influence of the pH value and the complex ions of metals can be successfully regulated by the Total ionic strength adjustment buffer (TISAB) solution and by maintaining the pH value in the range from 5.00 to 8.00. The fluoride concentrations of 34 different toothpaste samples of different brands are determined using an ion-selective electrode. The highest value is 1285.85 ppm from Germany (Blend a. Med) and the lowest value is 18.15 ppm from Indonesia (Formula junior). Most of the low values are from Asian countries between (18.15-514.84) ppm, which are less than 600 ppm and this concentration is insufficient for Iraqi prescriptions and World Health Organization (WHO) specifications, the highest Values are between (940.66-1285.85) ppm, from Japan, USA and Germany References Abramowitz, A. (1967) ‘Principles, current practice, and applications of potentiometers based on Poggendorff’s second method’, Review of Scientific Instruments, 38(7), pp. 898–904. doi: 10.1063/1.1720918. Barmes, D. E. (1996) ‘Fluorides and oral health’, Community Dental Health, pp. 3–4. Bereczki, R. et al. (2006) ‘How to assess the limits of ion-selective electrodes: Method for the determination of the ultimate span, response range, and selectivity coefficients of neutral carrier-based cation selective electrodes’, Analytical Chemistry, 78(3), pp. 942–950. doi: 10.1021/ac050614s. Bralić, M. et al. (2001) ‘Fluoride electrode with LaF3-membrane and simple disjoining solid-state internal contact’, Talanta, 55(3), pp. 581–586. doi: 10.1016/S0039-9140(01)00448-9. Chakraborty, M., Pandey, M. and Pandey, P. (2017) ‘Spectrophotometric method vs ion selective electrode for field determination of fluoride in water and complex samples’, Reserch Journal of Chemical Sciences, 7(5)(5), pp. 31–37. Available at: http://www.isca.in/rjcs/Archives/v7/i5/5.ISCA-RJCS-2017-022.pdf. Gao, W., Xie, X. and Bakker, E. (2020) ‘Direct Potentiometric Sensing of Anion Concentration (Not Activity)’, ACS Sensors, 5(2), pp. 313–318. doi: 10.1021/acssensors.9b02523. J, U. (2019) ‘a Review on Effect of Fluoride Concentration in Drinking Water.’, International Journal of Advanced Research, 7(3), pp. 475–478. doi: 10.21474/ijar01/8659. Jasielec, J. (no date) Modelling of potentiometric ion sensors. Julie, L. (1967) ‘A Universal Potentiometer’, IEEE Trans Instr. Meas., IM(3), pp. 187–191. Lennon, M. A. et al. (2004) ‘Rolling Revision of the WHO Guidelines for Drinking-Water Quality’, World Health Organization, (September), pp. 105–116. Available at: http://www.who.int/water_sanitation_health/dwq/chemicals/en/nitratesfull.pdf. Light, T. S. and Cappuccino, C. C. (1975) ‘Determination of fluoride in toothpaste using an lon-selective electrode.’, Journal of chemical education, 52(4), pp. 247–250. doi: 10.1021/ed052p247. Michalski, R. and Mathews, B. (2006) ‘Simultaneous determination of fluoride and monofluorophosphate in toothpastes by supressed ion chromatography’, Central European Journal of Chemistry, 4(4), pp. 798–807. doi: 10.2478/s11532-006-0042-0. Midgley, D. (1987) ‘Limits of detection of ion-selective electrodes: Theory and practice’, Transactions of the Institute of Measurement & Control, 9(1), pp. 25–36. doi: 10.1177/014233128700900105. Radić, J. et al. (2020) ‘Development of the New Fluoride Ion-Selective Electrode Modified with FexOy Nanoparticles’, Molecules (Basel, Switzerland), 25(21). doi: 10.3390/molecules25215213. Seguí Femenias, Y. et al. (2016) ‘Ag/AgCl ion-selective electrodes in neutral and alkaline environments containing interfering ions’, Materials and Structures/Materiaux et Constructions, pp. 2637–2651. doi: 10.1617/s11527-015-0673-8. TOKALIOGLU, Š., KARTAL, S. and SAHIN, U. (2004) ‘Determination of Fluoride in Various Samples and’, Turk J Chem, 28(2), pp. 203–211. Tzimou-Tsitouridou, R., Kabasakalis, B. and Alexiades, C. A. (1985) ‘A new TISAB with Aluminon for fluoride determination in water with ion-selective electrode’, Microchemical Journal, 32(3), pp. 373–382. doi: 10.1016/0026-265X(85)90104-3. Yildiz, Y. et al. (2018) ‘Analytical Chemistry : An Indian Journal Potentiometric Determination of % Fluoride Ion Content ( w / v ) in Toothpastes by Ion Selective Electrode’, 18(August), pp. 0–8. Zohoori, F. V. et al. (2015) ‘Effect of exercise on fluoride metabolism in adult humans: A pilot study’, Scientific Reports, 5, pp. 1–9. doi: 10.1038/srep16905.

Controllable design of defect-rich hybrid iron oxide nanostructures on mesoporous carbon-based scaffold for pseudocapacitive applications.

The controllable design of functional nanostructures for energy and environmental applications represents a critical yet challenging technology. The existing fabrication strategies focus mainly on increasing the number of accessible active sites. However, these techniques generally necessitate complex chemical agents and suffer from limited experimental conditions delivering high costs, low yields, and poor reproducibility. The present work reports a new strategy for controllable synthesis of a hybrid system including mixed iron oxide nanostructures enriched with non-stoichiometric Fe21.34O32 and Fe3+[Fe5/33+□1/32+]O4 phases, which possess a high concentration of oxygen and Fe2+ vacancies, and a mesoporous carbon-based scaffold (MCS), which was dervied from coffee residues, with graphitic surface and perforated architecture. The nanoperforates acted as trapping sites to localise the FexOy nanoparticles, thereby boosting the density of accessible active sites. Additionally, at the interfacial regions between the FexOy crystallites, a high density of oxygen vacancies with an oriented pattern was shown to create superlattice structures. The energy storage functionality of the defect-rich MCS/FexOy nanostructure with nanoperforated architecture was investigated, where the results exhibited a high gravimetric capacitance of 540 F g-1 at a current density of 1 A g-1 with outstanding capacitance retention of 73.6% after 14 000 cycles.

Development of the New Fluoride Ion-Selective Electrode Modified with FexOy Nanoparticles.

A new modified ion-selective electrode with membranes of LaF3 single crystals with different internal contacts (solid steel or electrolyte) and with FexOy nanoparticles as loading was developed. The best response characteristic with linear potential change was found in the fluoride concentration range from 10−1 to 3.98 × 10−7 M. The detection limit for the electrolyte contact was determined at 7.41 × 10−8 M with a regression coefficient of 0.9932, while the regression coefficient for the solid contact was 0.9969. The potential change per concentration decade ranged from 50.3 to 62.4 mV, depending on whether the contact was solid or electrolytic. The prepared modified electrode has a long lifetime, as well as the possibility of application in different positions (solid contact), and it can also be used for the determination of iron ions. The electrode characterization was performed with scanning electron microscopy and elemental analysis with the technique of electron-dispersive X-ray spectroscopy.

Magnetically modified montmorillonite - characterisation, sorption properties and stability

Clay mineral montmorillonite (Mt) magnetised by FexOy nanoparticles (NPs) was prepared by precipitation in two steps. Magnetically modified montmorillonite (MMt) was tested as a sorbent for the elimination of heavy metals ions from aqueous solutions. Zn(II), Cd(II), Pb(II) ions and their combination were successfully sorbed by magnetic composite (MMt). The equilibrium was achieved after 30 min of interaction of the liquid phase with MMt. The influence of solid-to-liquid ratio on the MMt sorption properties was studied as well. The amounts of ions removed by Mt and MMt were comparable. Therefore, magnetisation of Mt did not influence its sorption capacity. The composite can be easily removed by a magnetic field from the solution after sorption.

Gradient electrospinning and controlled pyrolysis derived FexOy@N-doped carbon nanorods towards enhanced lithium storage

The rational structural design of the anode material plays a vital role in the performance of lithium-ion batteries (LIBs). Herein, a novel one-dimensional carbon based anode material, consisting of ultra-fine hollow FexOy nanoparticles (NPs) uniformly anchored on the porous N-doped carbon nanorods (donated as FexOy@PN-CNR) has been fabricated via electrospinning technique combined with controlled pyrolysis. Under the Kirkendall-type diffusion, Fe3C is transformed into hollow FexOy NPs. This unique structure could effectively prevent the aggregation, dissolution, and pulverization of iron oxide NPs, maintaining the structural integrity of the electrode. Additionally, it also provides a connected hierarchical conducting network with doped N for electron transport and offers abundant accessible porous channels for fast Li+ diffusion. As a consequence, the resulting FexOy@PN-CNR composite delivers an ultra-high reversible specific capacity of 1198.6 mA h g−1 at 1000 mA g−1 over 100 cycles as anode in LIBs. Remarkably, a stable cycle life (800 mA h g−1 after 200 cycles with a nearly 100% coulombic efficiency) can be obtained even at a large rate of 5000 mA g−1. The present study provides a promising strategy for the construction of nanostructured anode materials toward prominent electrochemical performance of LIBs.

Selective synthesis and characterization of iron oxide nanoparticles via PVA/PVP polymer blend as structure-directing agent

FexOy nanoparticles have been prepared by hydrothermal technique in the absence and presence of 5% polymer blend of PVA/PVP as structure-directing agent. The as-prepared nanoparticles have been characterized by powder x-ray diffraction (XRD), ultraviolet visible light spectroscopy (UV–Vis), Brunauer–Emmett–Teller (BET) analysis, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and x-ray photoelectron spectroscopy (XPS). TEM, and HRTEM results revealed that the as-prepared nanoparticles were single crystalline and had semi-spherical morphology. Also, the results revealed that the presence of the polymer blend served as a structural controlling agent as the presence of the polymer blend produced Fe3O4 (magnetite) nanoparticles selectively rather than γ-Fe2O3 (maghemite) nanoparticles. The reasons behind the impact of polymer blend were investigated. This method represents a facile and polymorphs-selective synthesis of iron oxide nanoparticles for different applications.

Effect of Spray Parameters in a Spray Flame Reactor During FexOy Nanoparticles Synthesis

Synthesis and characterization of FexOy nanoparticles were carried out in order to study reaction parameters influence in a spray flame reactor. FexOy powders were prepared with three different precursors aiming to understand how the reactor conditions, dispersion gas flow, and precursor solution flow affect morphology, shape, particle size distribution, crystalline phases, and residue content of the obtained materials. Thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy (TEM), x-ray diffraction (XRD), and Raman spectroscopy were employed to characterize the materials. In addition, magnetic behavior of the obtained samples was evaluated. It was found that the evaluated parameters influenced the residue contents obtaining weight changes from 10 to 35%. Particle size distribution centers also showed differences between 17 and 24 nm. By XRD, Raman, and TEM, the presence of hematite (a-Fe2O3), maghemite (γ-Fe2O3), and magnetite (Fe3O4) was evidenced and explained based on the gas and liquid content in the flame. Additionally, the saturation magnetization was measured for selected samples, obtaining values between 26 and 32 emu g−1. These magnetic measurements were correlated with the crystalline phase composition and particle size distributions.

Easy and low-cost preparation method of magnetic montmorillonite/FexOy composite: initial study for future applications

Magnetic montmorillonite with FexOy nanoparticles was prepared by precipitation. The results of the leaching test showed that the magnetic montmorillonite is stable in the acidic pH. The microwave treatment and the presence of FexOy nanoparticles on the montmorillonite did not influence the montmorillonite structure or distinctive release of the monitored cations. The main goal of the present paper was to find the optimal solid-to-liquid ratio when the ionic strength remains unchanged. The influence of solid-to-liquid ratio, leaching time, initial pH of extraction agent and the variation of the ionic strength of the final extract were studied as well. The results evaluated by analysis of variance (ANOVA) showed that both the solid-to-liquid ratio and the initial pH are factors which significantly influence the release of the cations from the study materials as well as the ionic strength of final extracts.

Step-by-step monitoring of a magnetic and SERS-active immunosensor assembly for purification and detection of tau protein.

We report a bottom‐up synthesis of iron oxide and gold nanoparticles, which are functionalized and combined to form a nanohybrid serving as an immune sensor, which selectively binds to tau protein, a biomarker for diagnosis of Alzheimer's disease. Detection of the target analyte is achieved by surface‐enhanced Raman scattering originating from the diagnostic part of the nanohybrid that was prepared from Au nanoparticles functionalized with 5,5′‐dithiobis‐(2‐nitrobenzoic acid) as a Raman reporter and monoclonal anti‐tau antibody. The magnetic part consists of FexOy nanoparticles functionalized with polyclonal anti‐tau antibody and is capable to separate tau protein from a complex matrix such as cerebrospinal fluid. We further identified and validated a set of analytical tools that allow monitoring the success of both nanoparticle preparation and each functionalization step performed during the assembly of the two binding sites by an immune reaction. By applying UV/Vis spectroscopy, dynamic light scattering, zeta potential measurements, X‐ray diffraction, small‐angle X‐ray scattering, and transmission electron microscopy, we demonstrate a proof‐of‐concept for a controlled and step‐by‐step traceable synthesis of a tau protein‐specific immune sensor.

From Newspaper Substrate to Nanotubes—Analysis of Carbonized Soot Grown on Kaolin Sized Newsprint

Herein, we report the successful use of newspaper as a substrate for the growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD) with intriguing results demonstrating that (a) the large surface area of newspaper stock allows for SWCNT growth and (b) only newspaper produced with kaolin clay sizing allowed for SWCNT growth. Kaolin newsprint was impregnated with Al2O3 and Fe(NO3)3·9H2O (as precursors to FexOy nanoparticles), and calcined (30 min at 400 °C). The subsequent char residue was loaded into a CVD chamber and used as a substrate for SWCNT growth at 750 °C, using H2, C2H2, and water vapor as the growth gas. Samples of raw carbon soot exhibiting fluorescence spectra, indicative of SWCNTs, were further evaluated by resonant Raman spectroscopy, and by transmission electron microscopy (TEM). The calcinated substrate remnants were evaluated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Experiments utilizing paper substrates produced with kaolin filler resulted in hybridized sp2–sp3 bonded carbon species. The soot was found to consist primarily of carbon nanotubes and bi-layer graphene in the form of collapsed nanotubes, also known as graphene nanoribbons (GNR).

Fe O nanoparticles in-situ embedded in porous carbon framework towards improved lithium storage

Abstract Constructing stable structure and efficient ion and electron diffusion pathways are critically important for high-performance anode materials of lithium-ion batteries. Herein, a unique nanocomposite composed of FeO/Fe2O3 (FexOy) nanoparticles in-situ wrapped within porous carbon framework has been successfully fabricated by an extremely facile and relatively green method, namely just calcinating the commercial ferric citrate in Ar atmosphere. Therefore, our strategy for preparing composites with unique structures has advantages of relative green and extreme simple compared with the commonly hydrothermal or solvothermal and followed by carbonization ways due to no use of various solvents and reagents, and additional time-and power-consuming hydrothermal or solvothermal heating treatment. Benefiting from the synergistic effect of FexOy nanoparticles and uniquely porous carbon framework, the as-achieved composite possesses robust structural stability and improved electrochemical kinetics. As a result, it exhibits superior lithium storage performance, delivering capacities of 606.4 and 526.6 mAh g−1 at 200 and 1000 mA g−1 after 450 and even 1200 cycles, respectively. Moreover, the advantages of relatively green and extremely facile preparation process, and good lithium storage performance may make this composite a promising anode candidate for next generation of high-performance lithium-ion batteries.

Metal-Organic Gel-Derived Fex Oy /Nitrogen-Doped Carbon Films for Enhanced Lithium Storage.

The development of cost-effective and flexible electrodes is demanding in the field of energy storage. Herein, flexible Fex Oy /nitrogen-doped carbon films (Fex Oy /NC-MOG) are prepared by facile electrospinning of Fe-based metal-organic gels (MOGs) followed by high-temperature carbonization. This approach allows the even mixing of fragile coordination polymers with polyacrylonitrile into flexible films while reserving the structural characteristics of coordination polymers. After thermal treatment, Fex Oy /NC-MOG films possess uniformly distributed Fex Oy nanoparticles and larger accessible surface areas than traditional Fex Oy -NC films without MOG. Taking advantage of the unique structure, Fex Oy /NC-MOG exhibits a superior rate performance (449.8 mA h g-1 at 5000 mA g-1 ) and long cycle life (629.3 mA h g-1 after 500 cycles at 1000 mA g-1 ) when used as additive-free anodes in lithium-ion batteries.

Investigating the Influence of Fe Speciation on N2O Decomposition Over Fe\u2013ZSM-5 Catalysts

The influence of Fe speciation on the decomposition rates of N2O over Fe–ZSM-5 catalysts prepared by Chemical Vapour Impregnation were investigated. Various weight loadings of Fe–ZSM-5 catalysts were prepared from the parent zeolite H-ZSM-5 with a Si:Al ratio of 23 or 30. The effect of Si:Al ratio and Fe weight loading was initially investigated before focussing on a single weight loading and the effects of acid washing on catalyst activity and iron speciation. UV/Vis spectroscopy, surface area analysis, XPS and ICP-OES of the acid washed catalysts indicated a reduction of ca. 60% of Fe loading when compared to the parent catalyst with a 0.4 wt% Fe loading. The TOF of N2O decomposition at 600 °C improved to 3.99 × 103 s−1 over the acid washed catalyst which had a weight loading of 0.16%, in contrast, the parent catalyst had a TOF of 1.60 × 103 s−1. Propane was added to the gas stream to act as a reductant and remove any inhibiting oxygen species that remain on the surface of the catalyst. Comparison of catalysts with relatively high and low Fe loadings achieved comparable levels of N2O decomposition when propane is present. When only N2O is present, low metal loading Fe–ZSM-5 catalysts are not capable of achieving high conversions due to the low proximity of active framework Fe3+ ions and extra-framework ɑ-Fe species, which limits oxygen desorption. Acid washing extracts Fe from these active sites and deposits it on the surface of the catalyst as FexOy, leading to a drop in activity. The Fe species present in the catalyst were identified using UV/Vis spectroscopy and speculate on the active species. We consider high loadings of Fe do not lead to an active catalyst when propane is present due to the formation of FexOy nanoparticles and clusters during catalyst preparation. These are inactive species which lead to a decrease in overall efficiency of the Fe ions and consequentially a lower TOF.

Laser-Assisted Synthesis of Colloidal FeWx Oy and Fe/Fex Oy Nanoparticles in Water and Ethanol.

Homogeneous polycrystalline Fex Oy nanoparticles were generated by ablation of iron targets in water by nanosecond laser pulses at 532 nm. In ethanol, crystalline core-shell Fe/Fex Oy structures with size medians around 20 nm were produced. The ablation of FeWx Oy targets in water resulted in crystalline hollow shells and homogeneous FeWx Oy nanoparticles. In contrast, amorphous core-shell FeWx Oy nanoparticles with a median size of 17 nm were produced in ethanol. The size distribution of both the Fex Oy and the FeWx Oy particles showed a slight dependence on fluence and pulse number. This may be related to primary and secondary ablation and modification mechanisms.

Modification of microwave assisted preparation of FexOy nanoparticles

During the recent several years, several preparation methods of FexOy micro and nanoparticles and composites of FexOy/phylosilicate were developed. The simple microwave-assisted synthesis of FexOy from FeSO4.7H2O has been tested recently. Both in magnetite (Fe3O4) and maghemite (γ-Fe2O3) have been proved in prepared FexOy particles. The goal was to prepare a micro and nanoparticles with higher Fe3O4 content. For this purpose, the iron nanoparticles were prepared using the FeSO4.7H2O with the addition of oxalic acid during the iron oxides precipitation. The syntheses were carried out under various conditions (pH of precipitation, amount of added oxalic acid, time of microwave activity). The prepared micro and nanoparticles were characterized by X-ray diffraction, chemical analyses, scanning and transmission electron microscopy, and magnetic properties measurement. The results showed that pH and addition of oxalic acid affected the content of FeO in prepared nanoparticles but the wüstite (FeO) was not identified and, as the result, the magnetic properties were changed. In contrast to the spherical iron oxides nanoparticles prepared using the unmodified method, resulting nanoparticles were of cylindrical shape when the oxalic acid was present.