Staff

Abstract:
In this research, electrophoretic deposition (EPD) was employed to prepare a porous composite film (ACF electrode) consisting of 90 wt% activated carbon particles, 10 wt% iron oxide nanoparticles, and a chitosan as binder in a facile, fast, and sustainable manner. This micro-mesoporous composite film, with a thickness of ∼45 µm and a surface area of ∼208.1 m2g−1, was coated on a stainless steel substrate. The SEM and TEM investigations proved the homogeneous distribution of carbon microparticles and iron oxide nanoparticles in the deposit, while the EDX, XRD, Raman spectroscopy, and XPS confirmed the chemical composition. ACF electrodes were also used in a symmetric two-electrode cell configuration with a sandwiched gel polymer electrolyte - PVdF(HFP)-PC-Mg(ClO4)2 and revealed a specific capacitance of ∼54.4 F g−1, along with satisfactory energy and power density of ∼4.7 Wh kg−1 and 1.2 kW kg−1, respectively, and excellent electrochemical stability up to ∼10,000 cycles (with merely 8.5% decay by the 5000th cycle). Obtained results confirmed the stability of the used system and its possible application in the field of energy storage and conversion.

Abstract:
In this current work, the pristine LiNi0.5Mn1.5O4 (LNMO) and fluorine-doped LiNi0.5Mn1.5O4–xFx (x = 0.1; 0.2; 0.3) cathode materials were successfully synthesized through a facile spray-drying method. The performed morphological and structural characterizations revealed that the fluorine doping led to a partial conversion of Mn4+ to Mn3+ ions in LNMO structure and an increase of their average particle sizes. These characteristics made the LiNi0.5Mn1.5O3.9F0.1 cathode exhibited the best rate capability at high C-rates and cycling performance among all investigated LNMO-based electrodes. Its improved electrochemical properties resulted from excellent crystallinity, high Li+ diffusion coefficient, and low charge-transfer resistance. Moreover, the LiNi0.5Mn1.5O3.9F0.1 electrode was found to possess the excellent resistant against Mn dissolution at elevated temperature. According to its great thermal stability, an impressive capacity retention of 81.5% after 100-cycle at 0.2 C at elevated temperature was achieved. In terms of the facile synthesis approach, superior electrochemical performances, and great thermal stability, the LiNi0.5Mn1.5O3.9F0.1 electrode synthesized by the scalable spray-drying method can be regarded as a promising high-voltage cathode material for high-performance Li-ion batteries.

Keywords:
Cathode material, Fluorine doping, Spinel LiNi0.5Mn1.5O4, Spray-drying synthesis, Li-ion batteries

Abstract:
The sustainable transformation of bio-waste into usable, material has gained great scientific interest. In this paper, we have presented preparation of an activated carbon material from a natural mushroom (Suillus boletus) and explor its properties for supercapacitor and dye adsorption applications. The produced cell exhibited a single electrode capacitance of ∼247 F g−1 with the energy and power density of ∼35 Wh kg−1 and 1.3 kW kg−1, respectively. The cell worked well for ∼20,000 cycles with ∼30% initial declination in capacitance. Three cells connected in series glowed a 2.0 V LED for ∼1.5 min. Moreover, ultrafast adsorption of methylene blue dye onto the prepared carbon as an adsorbent was recorded with ∼100% removal efficiency in an equilibrium time of three minutes. The performed tests indicate that the mushroom-derived activated carbon has the potential to become a high-performance electrode material for supercapacitors and an adsorbent for real-time wastewater treatment applications.

Keywords:
Activated carbon, Amorphous material, Biomass, Polymer gel electrolyte, Supercapacitor, Dye adsorption

Abstract:
The main aim of this work was to use the iron–iron oxide nanochains (Fe NCs) as adsorbents of the carcinogenic cationic crystal violet (CV) and anionic Congo red (CR) dyes from water. The investigated adsorbent was prepared by a magnetic-field-induced reduction reaction, and it revealed a typical core–shell structure. It was composed of an iron core covered by a thin Fe3O4 shell (<4 nm). The adsorption measurements conducted with UV–vis spectroscopy revealed that 15 mg of Fe NCs constituted an efficient dose to be used in the CV and CR treatment. The highest effectiveness of CV and CR removal was found for a contact time of 90 min at pH 7 and 150 min at pH 8, respectively. Kinetic studies indicated that the adsorption followed the pseudo-first-order kinetic model. The adsorption process followed the Temkin model for both dyes taking into account the highest value of the R2 coefficient, whereas in the case of CR, the Redlich–Peterson model could be also considered. The maximal adsorption capacity estimated from the Langmuir isotherms for the CV and CR was 778.47 and 348.46 mg g–1, respectively. Based on the Freundlich model, both dyes adsorbed on the Fe NCs through chemisorption, but Coulombic interactions between the dye and adsorbent cannot be excluded in the case of the CV dye. The obtained results proved that the investigated Fe NCs had an excellent adsorption ability for both dye molecules within five cycles of adsorption/desorption, and therefore, they can be considered as a promising material for water purification and environmental applications.

Abstract:
The zerovalent iron (Fe0) nanomaterials tend to be spontaneously oxidized in the presence of oxygen. This leads to the formation of interface composed of iron core and thin iron oxide shell. These structures are frequently observed with transmission electron microscope but, at the same time, it is hard to determine the precise structural and chemical composition of oxide shell. This feature is very important for possible applications of Fe0 nanostructures. Hence, the present work aims to deliver more detailed insights in this topic. The investigations are performed for the iron nanochains prepared in the magnetic-field-induce reduction of FeCl3 by NaBH4. The high-resolution transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoemission spectroscopy confirm that the iron nanochains are covered by very thin oxide layer not exceeding over 3 nm. Moreover, the detailed XPS analyses of O 1s and Fe 2p lines indicate that the iron oxide shell reveals Fe3O4 nature. Moreover, this work demonstrated that some by-products of the reaction containing boron are presented in the sample even after a removal of the thin iron oxide shell by Ar+ treatment.

Keywords:
iron nanochains, magnetic-field-induced synthesis, surface oxidation, x-ray photoemission spectroscopy

Abstract:
In order to use the infrared (IR) radiation shielding materials, they should take a form of thin film coatings deposited on glass/polymer substrates or be used as fillers of glass/polymer. The first approach usually suffers from several
technological problems. Therefore, the second strategy gains more and more attention. Taking into account this trend, this work presents the usage of iron nanoparticles (Fe NPs) embedded into the poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films as the shielding material in near-infrared (NIR) and mid-infrared (MIR) region. The performed
investigations show that the transmittance of copolymer films decreases with
increasing content of the Fe NPs inside them. It is found that the average fade of IR transmittance for 1, 2.5, 5, 10, and 50 mg of Fe NPs is about 13%, 24%, 31%, 77%, and 98%, respectively. Moreover, it is observed that the PVDF-HFP films filled in the Fe NPs almost does not reflect the NIR and MIR radiation. Hence, the IR shielding properties of the PVDF-HFP films can be effectively tuned by the addition of proper amount of the Fe NPs. This, in turn, shows that the PVDF-HFP films filled in the Fe NPs constitute a great option for IR antireflective and shielding applications.

Keywords:
antireflective materials, copolymer films, infrared radiation shielding materials, iron nanoparticles, nanofillers

Abstract:
Commendable efforts have been gingered towards the fight against cancer. Nevertheless, it remains a major public health concern due to its predominant cause of death globally. Given this, we synthesized two different nanoparticles, Sr2+ and Gd3+ doped magnetite for magnetic hyperthermia and drug delivery application. Based on the characterization, the diffractogram shows that only one phase related to magnetite with a crystallite size of 10 nm was formed. TEM images revealed nanoparticles of spherical shapes of approximately 12 nm. There is no difference in magnetic saturation of the as-received synthesized samples (Fe3O4@Sr and Fe3O4@Gd), while the BET-specific surface area of Fe3O4@Gd is 8 m2 g−1 higher than Fe3O4@Sr. The heat generation in alternating magnetic field (the magnetic hyperthermia) of Fe3O4@Sr functionalized with citric acid and loaded with 5- fluorouracil (Fe3O4@Sr@CA@5-flu) is slower than Fe3O4@Gd@CA@5-flu. The specific absorption rate (SAR) of Fe3O4@Gd@CA@5-flu, 112.0 ± 10.4 W g−1 was found to be higher than that of Fe3O4@Sr@CA@5-flu. The thermogram shows that 11% of the drug was successfully loaded on Fe3O4@Gd@CA@5-flu. The release of the antitumor drug by the synthesized nanoparticle drug carriers for ovarian cancer (SKOV-3 cells) therapy showed that more than 50% of the cancer cell’s viability was reduced after 72 h of incubation. The synthesized nanoparticles demonstrated a promising drug carrier for the treatment of SKOV-3 cells.

Abstract:
A coupled process of ultrasonic spray pyrolysis and lyophilisation was used for the synthesis of dried gold nanoparticles. Two methods were applied for determining their melting temperature: uniaxial microcompression and differential scanning calorimetry (DSC) analysis. Uniaxial microcompression resulted in sintering of the dried gold nanoparticles at room temperature with an activation energy of 26–32.5 J/g, which made it impossible to evaluate their melting point. Using DSC, the melting point of the dried gold nanoparticles was measured to be around 1064.3°C, which is close to pure gold. The reason for the absence of a melting point depression in dried gold nanoparticles was their exothermic sintering between 712 and 908.1°C.

Keywords:
gold nanoparticles, melting point, ultrasonic spray pyrolysis, characterisation

Abstract:
This work presents a growth of Fe3O4 nanoparticle films on silicon substrate. The iron oxide is deposited applying a pulsed laser deposition technique. The process is performed in open air in the absence and presence of external magnetic field. In fact, the morphologies of the obtained Fe3O4–Si samples are similar. The Fe3O4 nanoparticles are spherical with average diameters of 30 nm and are densely agglomerated on the Si substrate. The Fe3O4–Si material prepared in the absence of magnetic field has revealed more intense signals during X-ray diffraction and Raman measurements. The magnetic investigations indicate that the Fe3O4 nanoparticles are significantly coupled with the Si substrate and do not exhibit superparamagnetic behavior. Moreover, the Verwey transition is 98 K for both investigated Fe3O4–Si samples.

Keywords:
Fe3O4 nanoparticles,magnetic materials,pulsed laser deposition

Abstract:
Li4Ti5O12 (LTO) is a promising anode material for lithium-ion batteries (LIBs) due to its stable reversibility, high-rate cyclability, and high operational potential. On the other hand, it suffers from poor electronic conductivity and low capacitance. To overcome these disadvantages, modification of the LTO surface is frequently undertaken. Considering this idea, the production of a biomass-derived carbon-coated LTO material (LTO/C) and its application as an anode in LIBs is described in this work. The carbon precursor was obtained from commercial carrot juice, which was degraded using microwaves. According to the UV studies, the carbon precursor revealed similar properties to carbon quantum dots. Then, it was deposited on LTO synthetized through a sol-gel method. The LTO/C electrode exhibited a high specific capacity of 211 mAhg−1 at 0.1 C. Capacity retention equal to 53% of the initial value was found for the charge–discharge rate increase from 0.1 C to 20 C. The excellent electrochemical performance of LTO/C was caused by the carbon coating, which provided (i) short diffusion pathways for the Li+ ions into the LTO structure and (ii) enhanced electronic conductivity. The obtained results indicated that biomass-derived carbon quantum dot-coated LTO can be considered as a promising anode for LIBs.

Keywords:
anode material, biomass-derived carbon, carbon coating, carbon quantum dot, lithium-ion battery

Abstract:
Magnetic nanoparticles-mediated hyperthermia was widely studied in the last decades as applicable in cancer therapy. The majority of magnetic hyperthermia research was devoted to improvement of heating efficiency by application of various nanomaterials. The influence of biocompatibility, magnetic properties, sizes, composition, and concentration of magnetic nanoparticles (MNPs) on hyperthermia efficiency was extensively studied. Also, the limits preserving biological safety and the chemical stability of MNPs delivered to the tissue were established. However, much less research concerned the impact of the physical interactions between the closest MNPs on the hyperthermia efficiency. Our goal was to demonstrate the relationships between the internal structure of soft tissue containing MNPs, and the thermal effects of an alternating magnetic field. Because agarose-based gel exhibits a tissue-like internal structure, we performed hyperthermia experiments in two types of such gel containing bare and polyethylene glycol-coated Fe3O4 nanoparticles. We described the structural difference and we estimated the ferrogels specific absorption rate coefficients (SAR) from calorimetric experiments. Magnetic measurements showed 11% lower magnetic saturation of PEG-coated MNPs than of the bare MNPs. While the SAR of ferrogel with PEG-coated MNPs was 15% greater than bare MNPs. The structural characteristics calculated from TEM and SEM images were significantly different. Particularly, we observed the nanoparticle agglomeration in the gel with bare MNPs. The bare MNPs uniformly packed and located inside agarose double helices were observed for the first time. The distribution of MNPs and their spatial configuration in gel influenced strongly the strength of bonds blocking the movement of MNPs and determined the ferrogels heating efficiency. As the tissues to which we delivered MNPs were composed of agarose gel-like structures, our results may be useful in further research on hyperthermia in vivo. 10.1016/j.jmmm.2021.169000, 10.1016/j.jmmm.2022.169423

Keywords:
nanoparticle-mediated magnetic hyperthermia, ferrogel, nanoparticles distribution, double helices structure

Abstract:
Magnetic nanoparticles (MNP)s of Fe3O4 were synthesized in the co-precipitation reaction of iron chlorides dissolved in water and ammonia water. To produce polyethylene glycol (PEG) coatings of the NMPs, we added PEG to the ammonia water during the fabrication process. Magnetic fluids, ferrofluids, for research were prepared as oleic acid suspension of bare and PEG-coated nanoparticles at four concentrations. The results of the conducted calorimetric experiments confirmed that the efficiency of heating ferrofluids strongly depends on the concentration of nanoparticles in fluids. The results also indicate that the ferrofluids containing PEG-coated NPs heat up more than ferrofluids with bare nanoparticles. They are characterized by a higher specific absorption rate (SAR) value calculated from the initial slope of temperature versus time curve during heating. 10.1016/j.jmmm.2021.168918, 10.1016/j.jmmm.2022.169422

Keywords:
nanoparticle fluid hyperthermia, magnetite nanoparticles, PEG-coated nanoparticles, hyperthermia

Abstract:
This work presents the evolution of morphological, structural and magnetic properties of amorphous Fe-Ni wire-like nanochains caused by thermal oxidation. The initial Fe1−xNix samples (x = 0.75; 0.50; 0.25) were prepared through the magnetic-field-induced synthesis, and then they were heated in dry air at 400 °C and 500 °C. These treatments led to two competing simultaneous processes occurring in the investigated samples, i.e., (i) a conversion of amorphous material into crystalline material, and (ii) their oxidation. Both of them strictly affected the morphological and structural properties of the Fe-Ni nanochains which, in turn, were associated with the amount of iron in material. It was found that the Fe0.75Ni0.25 and Fe0.50Ni0.50 nanochains were covered during thermal treatment by the nanoparticle oxides. This coverage did not constitute a good barrier against oxidation, and these samples became more oxidized than the Fe0.25Ni0.75 sample which was covered by oxide nanosheets and contained additional Ni3B phase. The specific morphological evolutions of the Fe-Ni nanochains also influenced their saturation magnetizations, whereas their coercivities did not vary significantly. The obtained results constitute an important source of information for future application of the thermally treated Fe-Ni nanochains which could be applied in the energy storage devices or catalysis.

Abstract:
Thermal treatment is a post-synthesis treatment that aims to improve the crystallinity and interrelated physical properties of as-prepared materials. This process may also cause some unwanted changes in materials like their oxidation or contamination. In this work, we present the post-synthesis annealing treatments of the amorphous Fe1−xCox (x = 0.25; 0.50; 0.75) Wire-like nanochains performed at 400 °C in two different atmospheres, i.e., a mixture of 80% nitrogen and 20% hydrogen and argon. These processes caused significantly different changes of structural and magnetic properties of the initially-formed Fe-Co nanostructures. All of them crystallized and their cores were composed of body-centered cubic Fe-Co phase, whereas their oxide shells comprised of a mixture of CoFe2O4 and Fe3O4 phases. However, the annealing carried out in hydrogen-containing atmosphere caused a decomposition of the initial oxide shell layer, whereas a similar process in argon led to its slight thickening. Moreover, it was found that the cores of thermally-treated Fe0.25Co0.75 nanochains contained the hexagonal closest packed (hcp) Co phase and were covered by the nanosheet-like shell layer in the case of annealing performed in argon. Considering the evolution of magnetic properties induced by structural changes, it was observed that the coercivities of annealed Fe-Co nanochains increased in comparison with their non-annealed counterparts. The saturation magnetization (MS) of the Fe0.25Co0.75 nanomaterial annealed in both atmospheres was higher than that for the non-annealed sample. In turn, the MS of the Fe0.75Co0.25 and Fe0.50Co0.50 nanochains annealed in argon were lower than those recorded for non-annealed samples due to their partial oxidation during thermal processing.

Keywords:
annealing, amorphous materials, Fe-Co nanochains, magnetic-field-induced synthesis, wire-like nanostructure

Abstract:
An improved method for the production of luminescent carbon nanoparticles is proposed in this work. The new method overcomes the disadvantages of commonly used approaches. It involves two-stage laser ablation in water and in aqueous solutions, where the first stage is the laser ablation of a graphite target and the second is the shredding of particles produced in the first step. The two-stage method offers the optimization of the laser pulse fluence for the performance of each process. It was found that the two-stage process of laser ablation allows producing photoluminescent carbon structures in pure water. The additional reagent may be added either in the first or second stage. The first stage performed in pure water allows avoiding the contamination of the target. Moreover, it simplifies the identification of the origin of photoluminescence. Two synthesis routes for the preparation of carbon nanoparticles by the proposed method using pure water as well as urea aqueous solution are investigated. It was found that the use of urea as a reagent results in luminescence properties similar to those obtained with other more hazardous amine-based reagents. The influence of the synthesis approach and process parameters on the structural and luminescent properties of nanoparticles is also explored in this work.

Keywords:
pulsed laser ablation in liquid, carbon nanoparticles, photoluminescent particles

Abstract:
Preparation and detailed structural characterization of iron-nickel wire-like nanochains with Fe0.75Ni0.25, Fe0.50Ni0.50, and Fe0.25Ni0.75 compositions are reported. The investigated nanomaterials were produced in the novel template-free magnetic-field-induced reduction reaction with NaBH4 as a reducing agent. It is demonstrated that this method leads to the formation of Fe-Ni nanochains composed of spherical nanoparticles with an average diameter of 50-70 nm and with a very high degree of atomic disorder manifested as the lack of clearly developed bcc and fcc phases, which are usually observed for nano- and polycrystalline Fe-Ni species. The recorded wide-angle X-ray scattering data for the obtained Fe-Ni nanochains exhibit a strong resemblance to those obtained for bulk metallic glasses. The atomic scale structure of the investigated nanochains has been studied using pair distribution function analysis of the recorded total scattering data. The best fits to the experimental pair distribution functions have been achieved assuming two-phase models of hcp and bcc networks with the size of coherently scattering regions of about 2.5 nm in diameter, for each Fe-Ni composition. Transmission electron microscopy images indicate that the glass-like bimetallic alloy cores are covered by amorphous oxide/hydroxide shells with thickness ranging from 2 to 5 nm. Moreover, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy results confirm the core-shell structure of the Fe-Ni nanochains and a complex character of shell layer which consists of several iron- and nickel-containing phases.

Abstract:
A novel solution combustion synthesis of nanoscale spinel-structured Co3O4 powder was proposed in this work. The obtained material was composed of loosely arranged nanoparticles whose average diameter was about 36 nm. The as-prepared cobalt oxide powder was also tested as the anode material for Li-ion batteries and revealed specific capacities of 1060 and 533 mAh·g^−1 after 100 cycles at charge–discharge current densities of 100 and 500 mA·g^−1, respectively. Moreover, electrochemical measurements indicate that even though the synthesized nanomaterial possesses a low active surface area, it exhibits a relatively high specific capacity measured at 100 mA·g^−1 after 100 cycles and a quite good rate capability at current densities between 50 and 5000 mA·g^−1.

Keywords:
anode material, cobalt oxide, lithium-ion battery, solution combustion synthesis, transition metal oxide

Abstract:
Activated carbons are one of the possible electrode materials for supercapacitors (SCs), which are widely used in commercial applications. Herein, we reported the synthesis of a novel activated carbon derived through a cavitation process from the mixture of native European deciduous trees, Birch, Fagaceae, and Carpinus betulus (commonly known as European hornbeam), which was employed as the electrode material in SC. From the morphological and structural characterization, we observed that the prepared sample is a desirable carbon with good porosity and high specific surface area of about 614 m^2 g^-1. The electrochemical properties of the synthesized material were evaluated with a three-electrode configuration in 1.0 M H2SO4 electrolyte. It was found that in device mode, the carbon material delivers a specific capacitance of 24 F g^-1 at 0.25 A g^-1 with excellent cycling stability of over 10000 consecutive charge/discharge cycles. Thus, our studies demonstrate the facile synthesis of biomass-derived carbon and its application as a versatile electrode material for SC applications.

Keywords:
biomass, carbon material, deciduous trees, electrode material, supercapacitor

Abstract:
In this study, spinel LiNi0.5Mn1.5O4 (LNMO) was successfully decorated with Al2O3 thin film by using atomic layer deposition (ALD) approach and evaluated as a cathode material for high-temperature applications in lithium ion batteries (LIBs). To optimize the LNMO-Al2O3 electrodes operated at elevated temperature (55 °C), the effects of Al2O3 thicknesses adjusted by controlling the ALD deposition cycle were systemically investigated. According to the series of electrochemical results, the LNMO coated with the Al2O3 thin layer in the thickness of ca. 2 nm was achieved by using one-cycle ALD and the LNMO-Al2O3 electrode exhibited superior electrochemical stability (capacity retention up to 93.7% after consecutive 150 charge/discharge cycles at 0.5 C to the pristine LNMO electrode at elevated temperature. This can be attributed to two factors: (i) the decoration of Al2O3 thin layer could not contribute remarkably to extra resistance for charge transfer; (ii) Al2O3 thin film deposition could efficiently stabilize the growth of cathode electrolyte interface (CEI) and suppress the dissolution of transition metals. Therefore, these results verify that the LNMO-Al2O3 electrode could be regarded as a promising cathode material for high-voltage LIBs, especially at elevated temperature operation.

Keywords:
atomic layer deposition, Al2O3 coating, lithium nickel manganese oxide, lithium-ion battery, elevated temperature

Abstract:
This work describes comparative study on the application of Li4Ti5O12 (LTO) as anode materials for lithium-ion batteries which were successfully prepared by sol-gel synthesis with the use of two titanium sources. One of them was anatase-type titanium dioxide (TiO2), whereas the second was tetrabutyl titanate (TBT). Both obtained LTO materials were very similar in terms of their crystallinity and purity. In turn, the sample synthetized with TBT source revealed better particle dispersibility, and its particles were slightly lower in size. These particular features resulted in higher Li+ diffusion coefficient and better kinetic of Li+ ions during charge transfer reactions for the LTO synthetized with TBT source. This reflected in specific capacitance values for both electrodes which equalled 150 mAh g^−1, 120 mAh g^−1, and 63 mAh g^−1 for TBT-LTO and 120 mAh g^−1, 80 mAh g^−1, and 58 mAh g^−1 for TiO2-LTO at C-rates of 1, 5, and 10 C, respectively.

Keywords:
anodematerial, lithiumtitanate, lithium-ion batteries, sol-gel synthesis, tetrabutyl titanate, titaniumdioxide

Abstract:
This work describes the application of nano-iron modified carbon paste electrodes (CPEs) for the detection of copper, lead and zinc ions in aqueous solutions. The CPEs were manufactured by mixing commercial graphite powder with mineral oil and two types of iron nanomaterials, namely iron nanoparticles (Fe-NPs) and iron nanowires (Fe-NWs) whose preparation processes and properties were also presented herein. Preliminary electrochemical results showed that the CPEs modified with Fe-NWs (10% relative to the graphite) possessed a larger electrochemically active surface area in a comparison with unmodified electrodes and those modified with Fe-NPs. The current responses of investigated electrodes depended on the type of metal ion and its concentration. Contrary to previous literature reports on the modification of CPEs, higher current responses and lower detection limits were found for electrodes prepared with Fe-NWs. This indicates that the Fe-NWs constitute a promising modifier of CPEs for sensor application.

Keywords:
carbon paste electrode, iron nanoparticles, iron nanowires, magnetic-field-induced synthesis, metal ion detection

Abstract:
In this work, we successfully synthesized series of LiNi0.5Mn1.5O4 (LNMO) cathode materials with spinel structure by using a facile sol-gel method and then calcined at various temperature ranging from 600 to 1000 °C. The application of different calcination temperatures significantly influenced the surface morphology, stoichiometry and crystalline nature of the as-synthesized LNMO material. According to the results of physical characterizations, the LNMO materials calcined at various temperatures mainly revealed the stoichiometric disordered Fd-3m structure with a small amount of well-ordered P4332 phase. The structural analysis also exhibited that the control of the calcination temperature contributed to the higher crystalline nature. Moreover, the morphological investigations indicated that the increasing calcination temperatures caused the formation of large micron-sized LNMO material. In turn, the electrochemical evaluations revealed the impact of the calcination temperatures on enhancing the electrochemical performances of the LNMO electrode materials up to 900 °C. The LNMO electrode calcined at 900 °C exhibited an impressive initial discharge specific capacity of ca. 142 mAh g^−1 between 3.5 and 4.9 V vs. Li/Li+, and remarkably improved capacity retention of 97% over 50 cycles. Those excellent electrochemical properties were associated with the presence of the dominant Fd-3m phase over the P4332 phase. Additionally, the results of the corrosion and dissolution tests which were performed for all calcined LNMO materials in order to estimate the amount of manganese and nickel ions leached from them, proved that the micro-sized LNMO calcined at 900 °C was the most stable.

Keywords:
spinel LiNi0.5Mn1.5O4, sol-gel synthesis, calcination temperature, cathode material, lithium-ion batteries

Abstract:
So far, it has been proven that the magnetic-field-induced (MFI) synthesis is a process which mainly leads to the formation of magnetic metallic one-dimensional nanostructures. Taking advantage of this method, the new procedures which allow manufacture of the magnetic bimetallic iron–cobalt wire-like nanochains with Fe0.75 Co0.25, Fe0.50 Co0.50, and Fe0.25 Co0.75 compositions are demonstrated in this work. They were produced through a simple one-step magnetic-field-induced (MFI) chemical co-reduction of three different mixtures containing a proper amount of Fe2+ and Co2+ ions with aqueous sodium borohydride solution as the reducing agent. The synthesis process was carried out at room temperature without the use of templates, surfactants, complexing agents, and organic solvents. The morphological and structural studies indicated that all as-prepared materials were amorphous, and they were composed of nanoparticles aligned in almost straight chains. Moreover, they revealed the core–shell structures with bimetallic alloy cores containing desired iron-to-cobalt ratios and very thin oxide shells. Furthermore, the obtained nanostructures behaved as ferromagnetic materials. Their magnetic properties were correlated with their structural properties and chemical compositions. It was observed that their saturation magnetization decreased significantly with increasing content of cobalt in the chains, whereas the variation of their coercivity was less pronounced.

Abstract:
In this work we apply N+ ion irradiation on vertically aligned carbon nanotube (VACNT) arrays in order to increase the number of connections and joints in the CNT network. The ions energy was 50 keV and fluence 5 × 10^17 ions cm^−2. The film was 160 μm thick. SEM images revealed the ion irradiation altered the carbon bonding and created a sponge-like, brittle structure at the surface of the film, with the ion irradiation damage region extending ~4 μm in depth. TEM images showed the brittle structure consists of amorphous carbon forming between nanotubes. The significant enhancement of mechanical properties of the irradiated sample studied by the cyclic nanoindentation with a flat punch indenter was observed. Irradiation on the VACNT film made the structure stiffer, resulted in a higher percentage recovery, and reduced the energy dissipation under compression. The results are encouraging for further studies which will lead to create a class of materials - ion-irradiated VACNT films - which after further research may find application in storage or harvesting energy at the micro/nanoscale.

Keywords:
vertically aligned carbon nanotubes, ion irradiation, nanoindentation

Abstract:
Manufacturing process of wire-like binary or ternary metal nanoalloys applying the magnetic-field-induced (MFI) synthesis is still a challenging task. Hence, this work demonstrates for the first time how to produce the iron-nickel wire-like nanostruc-tures with Fe0.75Ni0.25, Fe0.5Ni0.5 and Fe0.25Ni0.75 compositions. In a contrary to the previously reported synthesis of the Fe-Ni wire-like nanomaterials, this process has been carried out at room temperature without employment of templates, surfactants, organic solvents, and other chemical additives. The as-prepared samples exhibit specific structures with the amorphous bimetallic alloy cores covered by thin amorphous oxide shells. Moreover, they are composed of nanoparticles which are aligned in nearly linear chains. The Fe-Ni samples are ferromagnetic materials. Their coercivity values and saturation magnetizations depend on chemical compositions and dimensions of the investigated chains. The highest saturation magnetization and the lowest coercivity is found for the material with the lowest content of nickel and vice versa.

Keywords:
amorphous materials, Fe–Ni chains, magnetic-field-induced synthesis, magnetic materials, wire-like nanostructure

Abstract:
The magnetically-assisted growth of the amorphous bimetallic iron–nickel wire-like nanostructures is presented in this work. The applied process is based on a simple reduction reaction of aqueous solutions containing Fe2+ and Ni2+ ions with NaBH4 in the presence of an external magnetic field of about 0.05 T. The morphology, chemical composition, and magnetic properties of as-prepared Fe–Ni nanostructures have been determined by means of scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry, and vibrating sample magnetometry. The obtained experimental data indicate that the as-prepared samples exhibit quite complex architectures i.e., they comprise of nanoparticles aligned in almost straight lines. In addition, they reveal the typical core-shell structures where the amorphous bimetallic alloy cores are covered by thin amorphous oxide shells. In turn, the magnetic measurements show that the Fe–Ni wire-like nanostructures behave as typical ferromagnetic nanomaterials and their magnetic parameters like saturation magnetizations and coercivities are strictly dependent on their sizes and chemical compositions.

Keywords:
amorphous materials, bimetallic nanostructures, magnetic-field-induced synthesis, magneticmaterials, wire-like nanostructures

Abstract:
This paper explores an anomalous size effect in thermal residual stresses occurring in the alumina matrix of Al2O3/Cr sintered composite upon varying the particle size of the chromium reinforcement. When a coarse chromium powder (45 µm mean particle size) is used the average residual stress in the alumina phase after cooling is compressive in accordance with the classical Eshelby solution. However, in the case of a fine chromium (5 µm mean particle size) it switches to tension. This effect, detected by photoluminescence piezospectroscopy, is also confirmed by X-ray and neutron diffraction experiments. As the classical micromechanics models are incapable to capture it, a finite element model is developed with the actual composite microstructure being reconstructed from the microtomography images. It is shown by numerical simulations that the anomalous size effect is associated with the complex microstructure of the composite fabricated with the fine chromium powder. It is also pointed out that the temperature dependence of the coefficients of thermal expansion of the matrix and the reinforcement affects the residual stress levels.

Keywords:
thermal residual stress, metal-ceramic composites, size effect, microcomputed tomography, finite element analysis

Abstract:
Iron is the crucial element for living organisms and its deficiency is described as the most common nutritional disorder all over the world. Nowadays, more effective and safe iron supplementation strategies for both humans and animals become one of the most important challenges in the therapy of nutritional deficiencies. Our previous in vivo studies confirmed safety and biodegradability of in-house manufactured zinc oxide-based nanoparticles and their rapid distribution to majority of organs and tissues in the body. In vitro examinations performed on Caco-2 cell line, a model of epithelial cells of the gastrointestinal tract, revealed a low toxicity of studied nanomaterials. In the current study, we investigated biodegradable zinc oxide nanoparticles doped with Fe(III) as a perspective supplementation strategy for iron deficiency. Biodegradable ZnO:Fe nanoparticles were intra-gastrically administered to adult mice and following 24 h, animals were sacrificed with collection of internal organs for further analyses. The iron concentration measured with atomic absorption spectrometry and histological staining (Perl's method) showed a rapid distribution of iron-doped nanoparticles to tissues specifically related with iron homeostasis. Accumulation of iron was also visible within hepatocytes and around blood vessels within the spleen, which might indicate the transfer of Fe-doped nanoparticles from the bloodstream into the tissue. Reassuming, preliminary results obtained in the current study suggest that biodegradable ZnO nanoparticles doped with Fe might be a good carriers of exogenous iron in the living body. Therefore, subsequent investigations focus on determination an exact mechanisms related with an iron deposition in the tissue and influence of nanoparticle carriers on iron metabolism are required.

Keywords:
ZnO:Fe, nanoparticles, iron deficiency, iron delivery, iron doping

Abstract:
This work describes a use of a composite nanomaterial which consists of multiwall carbon nanotubes covered by iron oxide nanoparticles as a hybrid electrode in aqueous supercapacitor. The investigated nanomaterial was manufactured in a two-step simple chemical synthesis in which the first step was a functionalization of carbon nanotubes whereas the second one was the deposition of iron oxide. According the morphological and structural characterization, the carbon nanotubes with diameters of 10–40 nm were successfully covered by randomly-dispersed magnetite nanoparticles with average diameter of 10 nm. Moreover, the thermogravimetric analysis results indicated that the mass ratio between carbon nanotubes and iron oxide nanoparticles was about 65–35%. The electrochemical performance of studied hybrid electrode was tested in 1M aqueous KCl electrolyte. The highest specific capacitance of 143 F g^‒1 was recorded at a discharge current density of 1 A g^‒1. The investigated nanomaterial also exhibited excellent cycling stability i.e. 81% retention of the initial capacitance after 3000 cycles.

Keywords:
hybrid electrode, magnetite, multiwall carbon nanotube, nanocomposite, supercapacitor

Abstract:
The thermal treatment of chains composed of amorphous Fe 1–x Co x nanoparticles in two different oxygen atmospheres was studied. The nanostructures were manufactured using a magnetic-field-induced coreduction reaction, in which the precursor solutions containing 1:3 and 3:1 proportions of Fe 2+ and Co 2+ ions were reduced with sodium borohydride. The as-prepared nanochains were then heated for 30 min at 400 and 500 °C in dry air or argon containing about 1% oxygen. These processes led to their oxidation, and, as a result, the thermally treated Fe 1–x Co x nanochains were transformed into cobalt ferrite. Heating at 500 °C in the air-containing atmosphere caused the nanomaterials to lose their nanochain structures. In accordance to room-temperature magnetic measurements, the as-prepared and thermally treated Fe 1–x Co x nanochains were ferromagnetic. The highest saturation magnetization (Ms) was measured for the Fe 1–x Co x nanochains treated at 400 °C in dry air (105 A*m^2/kg and 154 A*m^2/kg for Fe 0.25 Co 0.75 and Fe 0.75 Co 0.25, respectively), whereas the lowest Ms was found for the Fe 0.25 Co 0.75 heated at 500 °C in dry air (17 A*m^2/kg) and the Fe 0.75 Co 0.25 heated at 500 °C in argon (16 A*m^2/kg).

Keywords:
nanomagnetics, FeCo nanochains, magnetic-field-induced synthesis, thermal treatment

Abstract:
This work describes optical measurements of processing-induced thermal residual stresses in an alumina matrix reinforced with chromium particles. This ceramic-metal composite is manufactured by the powder metallurgy method comprising powder mixing in a planetary ball mill and consolidation by hot pressing. Two different chromium powders (5 μm and 45 μm mean particle size) are used, while the average alumina particle size is kept constant (1 μm). The residual stresses in aluminum oxide are determined by applying two optical methods: photoluminescence piezo-spectroscopy (PLPS) and Raman spectroscopy (RS). Both experimental techniques reveal a chromium size effect in the residual stress measurements. When the fine chromium powder (5 μm) is used, the average residual stress in the ceramic phase is tensile (unusual effect), whereas for the coarser chromium powder (45 μm) it becomes compressive. The PLPS measurements of the hydrostatic residual stress component in the ceramic phase yield the values of 0.290 and −0.130 GPa for samples with 5 μm and 45 μm chromium powders, respectively. In the RS experiments, the corresponding stress component in the alumina equals 0.351 GPa for the composite with 5 μm chromium and −0.158 GPa for that with 45 μm chromium powder. These values indicate that the residual stress in the alumina reinforced with 5 μm chromium is approximately twice higher than that in the alumina reinforced with 45 μm chromium. Finally, the validity of the results obtained with the optical techniques is confirmed by the neutron diffraction measurements.

Abstract:
The main objective of this work is to study the influence of thermal oxidation on the chemical composition and magnetic properties of iron nanoparticles which were manufactured in a simple chemical reduction of Fe3+ ions coming from iron salt with sodium borohydride. The annealing processing was performed in an argon atmosphere containing the traces of oxygen to avoid spontaneous oxidation of iron at temperatures ranging from 200 °C to 800 °C. The chemical composition and magnetic properties of as-prepared and thermally-treated nanoparticles were determined by means of X-ray diffractometry, Raman spectroscopy, Mössbauer spectroscopy and vibrating sample magnetometry. Due to the magnetic interactions, the investigated iron nanoparticles tended to create the dense aggregates which were difficult to split even at low temperatures. This caused that there was no empty space between them, which led to their partial sintering at elevated temperatures. These features hindered their precise morphological observations using the electron microscopy techniques. The obtained results show that the annealing process up to 800 °C resulted in a progressive change in the chemical composition of as-prepared iron nanoparticles which was associated with their oxidation. As a consequence, their magnetic properties also depended on the annealing temperature. For instance, considering the values of saturation magnetization, its highest value was recorded for the as-prepared nanoparticles at 1 T and it equals 149 emu/g, while the saturation point for nanoparticles treated at 600 °C and higher temperatures was not reached even at the magnetic field of about 5 T. Moreover, a significant enhancement of coercivity was observed for the iron nanoparticles annealed over 600 °C.

Keywords:
Chemical composition, Chemical reduction, Iron nanoparticle, Magnetic properties, Oxidation

Abstract:
Magnetic nanoparticles based on iron or iron oxides represent an excellent nanomaterial in respect of their fundamental research as well as numerous applications. This work presents a Mössbauer study of the influence of thermal treatment on the structure and phase composition of iron nanoparticles fabricated via a simple reduction reaction. Identification of iron-containing phases has been carried out for the series of samples annealed at different temperatures ranging between 200 C and 800 C. Both crystalline and amorphous iron as well as variety of iron oxides have been detected. It has been proved that the nanoparticles annealed at 500 C show superparamagnetic behavior as a result of ultrafine sizes of crystallites of iron oxides that arise in the oxidation processes.

Abstract:
A lot of physical and chemical preparation methods of one-dimensional (1D) structures are known today. Most of them use highly advanced technology or quite complex chemical reagents. This results in their high costs and difficulties with their implementation to a large industrial scale. Hence, new, facile and inexpensive approaches are still sought. One alternative to wire-like structure production is based on the chemical reduction reactions combined with an external magnetic field, which acts as an independent synthesis parameter. This approach is commonly called magnetic-field-assisted (MFA) synthesis or magnetic-field-induced (MFI) synthesis. As usual, this manufacturing strategy comprises both drawbacks and advantages, which are introduced in this review. Moreover, this work shows that MFI synthesis depends on several synthesis parameters including the strength of the applied magnetic field, reaction temperature, pH value of the reaction environment, chemical composition of the precursor solution, reaction time, and also the presence of surfactants, complexing agents, nucleating agents, initiators as well as organic solvents. All of them have an impact on the morphology and dimensions of wire-like materials and their chemical, physical and mechanical properties. Finally, the opportunities and challenges associated with the magnetic-assisted fabrication of wire-like structures are widely discussed in this review

Keywords:
magnetic-field-induced synthesis, nanowire, microwire, nanochain, nanostructure, one-dimensional nanostructures

Abstract:
This work describes the detailed studies performed on the nanocomposite composed of chemically-modified multiwall carbon nanotubes covered by hematite nanoparticles which diameters vary from 10 nm to 70 nm. This nanomaterial was fabricated in two-steps facile chemical synthesis and was characterized with the use of several experimental techniques, such as: thermogravimetric analysis, differential thermal analysis, Raman spectroscopy, X-ray diffraction, and transmission Mössbauer spectroscopy in order to determine its structure precisely. Moreover, the investigated nanocomposite was tested as an anode material of Li-ion batteries. Its cycling performance was stable during 40 cycles, while its capacity was retained at the level of 330 and 230 mAh/g at the discharge/charge rate of 25 and 200 mA/g, respectively.

Keywords:
anode material, hematite, Li-ion battery, multiwall carbon nanotube, nanocomposite

Abstract:
Functionalized multiwall carbon nanotubes as well as nanocomposite based on that material covered by nanoparticles composed of iron oxides were the subject of investigations. In order to identify all iron-bearing phases including those reported on the base of previous X-ray diffraction measurements, the transmission Mössbauer spectroscopy was utilized. The experiments were carried out both at room temperature and also at low temperatures. It was stated that in the investigated nanotubes some impurities were present, originating from the catalyst remains, in form of Fe–C and -Fe nanoparticles. The Mössbauer spectra collected for the nanocomposite showed a complex shape characteristic of temperature relaxations. The following subspectra related to iron-based phases were identified: sextet attributed to hematite, with hyperfine magnetic field reduced due to the temperature relaxations, sextet corresponding to iron carbide as well as two doublets linked to superparamagnetic hematite and ferrihydrites.

Keywords:
Mossbauer spectroscopy, multiwall carbon nanotubes, phase transition

Abstract:
This work describes an oxidation process of iron–iron oxide core–shell nanowires at temperatures between 100°C and 800°C. The studied nanomaterial was synthesized through a simple chemical reduction of iron trichloride in an external magnetic field under a constant flow of argon. The electron microscopy investigations allowed determining that the as-prepared nanowires were composed of self-assembled iron nanoparticles which were covered by a 3 nm thick oxide shell and separated from each other by a thin interface layer. Both these layers exhibited an amorphous or highly-disordered character which was traced by means of transmission electron microscopy and Mössbauer spectroscopy. The thermal oxidation was carried out under a constant flow of argon which contained the traces of oxygen. The first stage of process was related to slow transformations of amorphous Fe and amorphous iron oxides into crystalline phases and disappearance of interfaces between iron nanoparticles forming the studied nanomaterial (range: 25–300°C). After that, the crystalline iron core and iron oxide shell became oxidized and signals for different compositions of iron oxide sheath were observed (range: 300–800°C) using X-ray diffraction, Raman spectroscopy and Mössbauer spectroscopy. According to the thermal gravimetric analysis, the nanowires heated up to 800°C under argon atmosphere gained 37% of mass with respect to their initial weight. The structure of the studied nanomaterial oxidized at 800°C was mainly composed of α-Fe2O3 (∼93%). Moreover, iron nanowires treated above 600°C lost their wire-like shape due to their shrinkage and collapse caused by the void coalescence.

Keywords:
annealing, core-shell nanostructure, iron nanoparticles, iron nanowires, oxidation, thermal treatment

Abstract:
The main aim of this work was to study the impact of thermal annealing on the structure of iron oxide shell covering iron nanowires in relation to their semiconducting properties. Studied nanomaterial has been produced via a simple chemical reduction in an external magnetic field and then it has been thermally-treated at 400oC, 600oC and also 800oC in a slightly oxidizing argon atmosphere. Annealed iron nanowires have been characterized by means of the Raman spectroscopy and photoluminescence in order to study the structure of iron oxide shell and its influence on semiconducting properties of the whole nanostructure. According to obtained experimental results, the composition of iron oxide shell covering the studied nanomaterial is changing with annealing temperature. The thermal treatment at 400oC leads to oxidation of iron coming from the core of nanomaterial and formation of a mixture of Fe3O4 and a-Fe2O3 on the surfaces of nanowires, while annealing at higher temperatures results in further oxidation of iron as well as the phase transformation of previously created Fe3O4 into the most thermo-dynamically stable form of iron oxide at ambient conditions — a-Fe2O3. This oxide has a major impact on the semiconducting properties of studied nanomaterial. Thereby, the measurements of photoluminescence enabled to estimate the bandgap of bulk and surface layer at about 1.8 eV and 2.1 eV, respectively.

Keywords:
nanowires, structure, optical properties, semiconductor nanostructures, micro- and nano-oxidation

Abstract:
The main goal of this work is to study the structural and magnetic properties of iron nanowires and iron nanoparticles, which have been fabricated in almost the same processes. The only difference in the synthesis is an application of an external magnetic field in order to form the iron nanowires. Both nanomaterials have been examined by means of transmission electron microscopy, energy dispersive X-ray spectrometry, X-ray diffractometry and Mössbauer spectrometry to determine their structures. Structural investigations confirm that obtained iron nanowires as well as nanoparticles reveal core–shell structures and they are composed of crystalline iron cores that are covered by amorphous or highly defected phases of iron and iron oxides. Magnetic properties have been measured using a vibrating sample magnetometer. The obtained values of coercivity, remanent magnetization, saturation magnetization as well as Curie temperature differ for both studied nanostructures. Higher values of magnetizations are observed for iron nanowires. At the same time, coercivity and Curie temperature are higher for iron nanoparticles.

Keywords:
iron nanoparticles, iron nanostructures, iron nanowires, magnetic properties, structural properties

Abstract:
This work presents the results of high temperature annealing of iron nanowires at five different temperatures (ranging 200–800 °C) in the slightly oxidative atmosphere. Investigated nanomaterial was prepared in simple chemical reduction process from aqueous solution of iron trichloride placed in external magnetic field. Experimental results allowed determining how magnetic properties of as-prepared as well as annealed iron nanowires change in respect to their structures. They also delivered information about phase transitions occurred in as-prepared sample under thermal treatment.

Keywords:
annealing, iron, magnetic properties, nanowires

Abstract:
Raman spectroscopy as well as Mössbauer spectroscopy were applied in order to study the phase composition of iron nanowires and its changes, caused by annealing in a neutral atmosphere at several temperatures ranging from 200°C to 800°C. As-prepared nanowires were manufactured via a simple chemical reduction in an external magnetic field. Both experimental techniques proved formation of the surface layer covered by crystalline iron oxides, with phase composition dependent on the annealing temperature (Ta). At higher Ta, hematite was the dominant phase in the nanowires.

Keywords:
amorphous iron and iron oxides, iron nanowires, Mössbauer spectroscopy, Raman spectroscopy, thermal annealing

Abstract:
The aim of this work is to study the preparation and characterization of a new nanocomposite which consists of chemically-modified multiwall carbon nanotubes covered by randomly-deposited nanoparticles of hematite. The morphology, structural and physical properties of the investigated nanomaterial were determined by means of transmission electron microscopy, X-ray diffraction and vibrating sample magnetometry at ambient conditions. The presence of residual catalyst nanospheres inside multiwall carbon nanotubes was confirmed by transmission electron microscopy. The signal coming from this contamination was under the detection limit of X-ray diffractometer, therefore it was not registered.

Keywords:
Hematite, Multiwall carbon nanotubes, CVD, TEM, XRD, VSM

Abstract:
The aim of the paper was a preliminary comparison of heating efficiency by the two physically different modalities, namely ultrasound sonication and alternating magnetic field, of magnetic nanoparticles added to an agar-gel. Special agar-based tissue mimicking material (TMM) were manufactured from agar with the addition of produced by us iron oxide magnetic nanoparticles of order c/a 11 nanometers. To perform comparison of heating by the measured temperature rise curves caused by the two physical fields differently acting on the material sample, in the case of ultrasonic radiation we did not locate the sensor of thermometer in the ultrasonic beam focus, as it was usually studied, but we put it in the place where distribution of ultrasound intensity was more homogeneous. It was motivated by the fact that the “homogeneous heating” by the magnetic iron oxide nanoparticles which are spatially homogeneously distributed should be compared with the ultrasonic heating effects caused by the spatially homogeneous ultrasonic sources. The obtained results confirm that for both fields, ultrasound and magnetic, the temperature increase was caused by the presence of nanoparticles. In the case of heating by magnetic field pure agar-gel was not heated at all, and during sonication the pure agar-gel exhibited very small thermal effect, due only to the structure of the agar-gel crosslinking. We concluded that the ultrasonic absorption was in our experiment greater than magnetic, but the temperature rise after 180 s of magnetic field action was greater than of sonication.

Keywords:
Heating systems, Ultrasonic imaging, Temperature measurement, Acoustics, Magnetic fields, Nanoparticles, Ultrasonic variables measurement

Keywords:
magnetic-field-induced process, magnetic material, nanoalloy, wire-like nanostructure