Nano-sized Oxide Research Articles

Unveiling the Reaction Mechanism during Li Uptake and Release of Nanosized "NiFeMnO4": Operando X-ray Absorption, X-ray Diffraction, and Pair Distribution Function Investigations.

Here, we report that the trimetallic nanosized oxide NiFeMnO4 consists of a mixture of NiO and a strained cubic spinel phase, which is clearly demonstrated by analysis of the pair distribution function (PDF) and synchrotron X-ray data. Such a finding can easily be overlooked by using only inhouse X-ray powder diffraction, leading to inaccurate assumption of the stoichiometry and oxidation states. Such advanced characterization is essential because a homogeneous distribution of the elements is observed in energy-dispersive X-ray spectroscopy maps, giving no hints for a phase separation. Cycling of the sample against Li delivers a high reversible capacity of ≈840 mAh/g in the 50th cycle. Operando X-ray absorption spectroscopy (XAS) experiments indicate that ≈0.8 Li/fu is consumed without detectable changes of the electronic structure. Increasing amounts of Li, Mn3+, and Fe3+ are simultaneously reduced. The disappearance of the pre-edge features in X-ray absorption near-edge spectroscopy indicates movement of these cations from tetrahedral sites to octahedral sites. PDF analysis of the pattern after an uptake of 2 Li/fu evidences that the principal structure can be sufficiently well modeled assuming coexisting NiO, a mixed monoxide, and a small amount of residual spinel phase. Thus, the majority of cations is located on octahedral sites. Furthermore, an improvement of the PDF model is achieved taking into account small amounts of LiOH. The 7Li MAS NMR spectrum of this sample clearly shows the signal of Li in a diamagnetic environment, excluding Li–O–TM bonds. A further increase of the Li content leads to a successive conversion of the cations to nanosized metal particles embedded in a LiOH/Li2O matrix. Ex situ XAS results indicate that Fe can be reversibly reoxidized to Fe3+ during charge whereas Mn does not reach the oxidation state observed in the pristine material. After excessive cycling, reoxidation of metallic Ni is suppressed and contributes to a capacity loss compared with the early discharge/charge cycles.

Synthesis of eco-friendly facile nano-sized zinc oxide particles using aqueous extract of Cymodocea serrulata and its potential biological applications

Green synthesis of nanoparticles is an emerging branch of nanotechnology due to its low cost and effectiveness. In this study, zinc oxide (ZnO-NPs) nanoparticles were biosynthesized by an eco-friendly method using Cymodocea serrulata. They were characterized by Ultraviolet–visible (UV–vis) spectroscopy, energy-dispersive X-ray (EDX), scanning electron microscopy (SEM), X-ray diffractometer (XRD), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. The synthesized crystalline nanoparticles were found to be 26.0–52.0 nm in size. The antioxidant activity of synthesized ZnO nanoparticles at 1000 µg/ml have revealed 75.55% in DPPH, 69.5% in deoxy-ribose, 62.75% in ABTS, 71.25% in nitric oxide and 74.10% in superoxide-scavenging assays. They also depicted significant bactericidal action against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, and Shigella flexneri. ZnO nanoparticles at 100 µg/ml concentration showed increased inhibition against B. subtilis with 18.0 mm, whereas moderate inhibition was seen against S. flexneri with 14.3 ± 0.25 mm. The cytotoxicity of ZnO-NPs was evaluated on A549 and H520 cell lines. The anti-proliferative effect was seen at 120 µg concentration on A549 and H520 cell lines with IC50 values of 55.0 ± 0.25 and 60.0 ± 0.50 µg/ml at 24 h. C. serrulata-coated zinc nanoparticles was found potential against bacterial pathogens and cancer cells. Therefore, they may be developed in future for biomedical applications.

Fabrication and characterization of nanocrystalline ODS-W via a dissolution-precipitation process

In this paper, high density nanocrystalline W with uniform dispersion of nanosized oxide particles was fabricated via a dissolution-precipitation process by well controlled high-energy ball milling of the raw powder materials of Y2O3, Ti and W and the subsequent spark plasma sintering (SPS). XRD and TEM analysis revealed that the Y2O3 and Ti were dissolved in W matrix during the high-energy ball milling and the Y2Ti2O7 particles were precipitated in the SPS process, resulting in the refinement in both W grains and oxide particles. The average grain size of W is 67 nm. The average size of particles in grain interior and at grain boundaries is 8.5 nm and 16.4 nm, respectively. The Vickers microhardness of such a nanostructured W alloy is as high as 1441 Hv, which is 2–3 times that of the ever reported W alloys. Such a dissolution-precipitation process offers a general pathway for manufacturing nanocrystalline refractory metals with dispersion of nanoscale oxides in a controllable manner.

Antibacterial activity of ZnO nanoparticles: dependence on particle size, dispersion media and storage time

Zinc oxide nanoparticles have a high potential as novel antimicrobial products. In this study ZnO nanoparticles of various sizes: 20-100 nm (ZnO-1) and 50-300 nm (ZnO-2) have been examined. This paper presents the results of an integrated study of the influence of physicochemical properties such as particle size and concentration of the freshly prepared and 24-hour suspensions of ZnO nanoparticles (0. 001…1000 mg/L) in distilled water and in normal saline upon their toxicity against bacteria E. coli. Ionic solutions of ZnCl2 were used for comparison study. Fresh aqueous solutions of nanoparticles displayed the highest antibacterial effect (E. coli survival under 5 − 25%). Storage for 24 hours reduced the toxicity of all the samples. In normal saline solutions the toxicity of the studied nanoparticles decreased at concentrations below 10 g/L. In all cases ZnO-2 suspensions displayed lower toxicity levels, especially after ageing for 24 hours. Stability analysis showed that the highest antibacterial effect was produced by less stable solutions containing the largest aggregates. Thus, it has been shown that antibacterial effects of zinc oxide nanoparticles are affected by the size of particles and their aggregates in colloidal solutions, chemical composition of the media and the suspensions storage time. The obtained results can be used for creating new types of antibacterial products including phytoprotectors based on nano-sized zinc oxide particles as well as for development of methods to assess and predict toxicity of zinc-containing suspensions.

Nano-sized mesoporous phosphated tin oxide as an efficient solid acid catalyst.

Herein, we prepared a mesoporous tin oxide catalyst (mSnO2) activated with phosphate species by the adsorption of phosphate ions from a phosphoric acid solution onto tin oxyhydroxide (Sn(OH)4) surface. The phosphate content ranged from 3 to 45 wt%. The nonaqueous titration of n-butylamine in acetonitrile was used to determine the total surface acidity level. FTIR of chemically adsorbed pyridine was used to differentiate between the Lewis and Brönsted acid sites. Thermal and X-ray diffraction analysis indicated that the addition of phosphate groups stabilized the mesostructure of mSnO2 and enabled it to keep its crystalline size at the nanoscale. FTIR analysis indicated the polymerization of the HPO42− groups into P2O74−, which in turn reacts with SnO2 to form a SnP2O7 layer, which stabilizes the mesoporous structure of SnO2. The acidity measurements showed that the phosphate species are distributed homogeneously over the mSnO2 surface until surface saturation coverage at 25 wt% PO43−, at which point the acid strength and surface acidity level are maximized. The catalytic activity was tested for the synthesis of hydroquinone diacetate, where it was found that the % yield of hydroquinone diacetate compound increased gradually with the increase in PO43− loading on mSnO2 until it reached a maximum value of 93.2% for the 25% PO43−/mSnO2 catalyst with 100% selectivity and excellent reusability for three consecutive runs with no loss in activity.

Chemistry of iron nitrate-based precursor solutions for spray-flame synthesis.

Understanding the chemistry of iron-based metal-organic precursor solutions for spray-flame synthesis is a key step to developing inexpensive and large scale applications for gas-phase synthesized, nano-sized iron oxide particles. Owing to the large variety of available organic solvents and iron compounds, the choice of a suitable precursor-solvent pair is challenging. Systematic investigations of the precursor chemistry of iron-based systems are currently not available. This work aims at filling this gap by providing a detailed spectroscopic analysis of mixtures containing iron(iii) nitrate nonahydrate and alkyl alcohols (C2-4). Moreover, the impact of adding 2-ethylhexanoic acid is explored. The FTIR spectra reveal the formation of carboxylates and allow deriving information about the coordination of the metal-carboxylate complexes. The stability of the precursor solutions is investigated by monitoring precipitation phenomena and turbidity. Furthermore, gas chromatography is employed to provide additional information on oxidation products and esters as well as to aid the interpretation of the FTIR data. It is found that the formation of esters has an enhancing effect on iron sorption and, thus, it promotes precursor stability.

Two-step synthesis of polymer fibre material comprising indium-, bismuth-, or antimony-doped nanosized tin oxides

In this paper, we present a method of formation of polymer fibre materials comprising dispersed oxides of rare and trace elements. The results of X-ray diffraction and spectral analyses show that the optimum synthesis conditions of the antimony-doped tin oxide, indium-doped tin oxide, and bismuth-doped tin oxide particles are provided using the “reverse” hydrolytic co-precipitation of hydroxides from chloride solutions combined with the subsequent thermal treatment at 1000°C. Durable fixation of nanoparticles on the fibre surface is confirmed by the atomic emission spectrometry with inductively coupled plasma and transmission electron microscopy. The results show that spraying of a free stream of the thermoplastic polymer melt with a gas stream containing nanoparticles allows obtaining fibre materials, which possess catalytic, photosensitive, as well as heat and sound insulating properties.

Evaluation of REE potential in Portuguese legacy mines

REE have unique properties that are mostly used to manufacture high tech devices. Most REE have geochemical properties that cause them to be typically dispersed and not often found in concentrated and economically exploitable forms, and difficult to separate. The ENVIREE project aims to develop environmentally friendly and efficient methods for their extraction from secondary sources. REE contents of tailings from four legacy mining sites have been obtained by INAA and analysed by 57Fe Mössbauer spectroscopy. REE concentrations in the tailings of Covas and Cumieira are more dependent on the REE contents of the primary ores and the treatment to extract the target metals than on the nano-sized oxides present. The tailings’ size, REE contents and Mössbauer results support the selection of the Covas tailing as the one to be submitted for further steps of REE extraction on the framework of the project.

Nano Ferric Oxide: Synthesis, Characterization and Catalytic Activity on Thermal Decomposition of Ammonium Perchlorate

A lot of attention has been given to incorporation of Nano-sized oxides including Fe₂O₃ in ammonium perchlorate (AP) based solid propellants to enhance their final performance. Nano ferric oxide was synthesized by a solid-state reaction method. The obtained products were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) for particle size, purity and morphology. Size reduction of the catalyst increases the surface area and hence, the catalytic activity is also increased.

Impact of nano-sized cerium oxide on physico-mechanical characteristics and thermal properties of the bacterial cellulose films

Impact of nano-sized cerium oxide on physico-mechanical characteristics and thermal properties of the bacterial cellulose films

CTAB-assisted synthesis of ZnCo2O4 nanoparticles embedded in N-doped carbon as superior anode materials for lithium-ion battery

One of the most effective methods to reduce the volume expansion of metal oxides is by designing nanosized metal oxides and forming composites with carbon materials. In this work, we report a simple method for constructing quasi-spherical ZnCo2O4 nanoparticles using a cetyltrimethylammonium bromide (CTAB) assisted sol-gel autocombustion method, followed by coating with an N-doped carbon layer to form a core-shell structure. When evaluated as anode material for Lithium ion battery, the novel core-shell structure electrode delivers a high capacity of 1146.6 mAh g−1 at a current density of 500 mA g−1 after 100 cycles. The electrode also demonstrates a high cycle stability with a good capacity of 811.3 mAh g−1 for 200 cycles at a current density of 2 A g−1. This performance is due to the carbon coating layer, which improves the electrical conductivity, relieves the volume expansion and mitigates the agglomeration of the ZnCo2O4 nanoparticles. Furthermore, the coating also ensures that a stable SEI layer forms at the outer surface of the robust carbon.

ZnO nanoparticles affect nutrient transport in an in vitro model of the small intestine

Nano-sized zinc oxide (ZnO) is present in food packaging, putting consumers at risk of ingestion. There is little information on the amount of ZnO nanoparticles (NP) present in food packaging and the effects of ZnO NP ingestion on intestinal function. To estimate physiologically relevant ZnO NP exposures from food that are commonly packaged with ZnO NP, food samples were analyzed with inductively coupled plasma mass spectrometry (ICP-MS). An in vitro model of the small intestine was used to investigate the effects of ZnO NP exposure. Cells were exposed to pristine NP in culture medium and to NP subjected to an in vitro digestion process to better reflect the transformation that the NP undergo in the human gastrointestinal (GI) tract. The findings show that a physiologically relevant dose of ZnO NP can cause a significant decrease in glucose transport, which is consistent with gene expression changes for the basolateral glucose transporter GLUT2. There is also evidence that the ZnO NP affect the microvilli of the intestinal cells, therefore reducing the amount of surface area available to absorb nutrients. These results suggest that the ingestion of ZnO NP can alter nutrient absorption in an in vitro model of the human small intestine.

Growth of free-standing SnO nanostructures on single layer graphene

The physical properties of nano-sized metal oxide semiconductors are influenced by the nanostructures as well as the crystallinity, thus the growth of crystalline tin oxide (SnO) with controlled morphologies would be important to its applications. To date, the various morphologies of SnO have been successfully synthesized such as nanodisks, nanobelts, nanoplatelets, nanoslabs, nanoflowers, and nanobranches. Here, the vertical free-standing SnO nanostructures were densely grown on single layer graphene (SLG) by vapor transport method. Compared with the tilted SnO nanostructures on SiO2/Si substrate, surface area ratio of the free-standing SnO nanostructures exhibit over of 4.4 times. According to analysis results such as Raman spectroscopy, FE-SEM, XRD, and FE-TEM, uniform and high quality free-standing SnO nanostructures were grown on large area SLG. We observed that the synthetic shapes of SnO nanostructures are different depending on the presence or absence of graphene film on substrate.

Nano-sized oxide filled composite PEO/PMMA/P(VDF-HFP) gel polymer electrolyte for rechargeable lithium and sodium batteries

Developing solid electrolyte for alkali metal batteries is of important significance. A gel polymer electrolyte (GPE) based on the porous composite polymer membrane formed by blending of PEO, PMMA and P(VDF-HFP) is prepared, and the effects of the addition of nano-sized oxide fillers (Al2O3, TiO2, SiO2) on the characteristics of the composite GPEs are investigated. The composite GPE with filling of SiO2 has more amorphous region and porous structure which can hold more liquid electrolyte without leakage, so the composite GPE can provide high ionic conductivity at room temperature and large Li+ or Na+ transport number. Furthermore, the composite GPE possesses a large electrochemical window, superior thermal stability and excellent interfacial stability. The composite GPEs can be applied in a variety of lithium and sodium metal batteries and exhibit superior cycling stability and rate performance.

Facile synthesis of UV blocking nano-sized Zinc Oxide and Polymethyl-methacrylate polymer nanocomposite coating material

Present work reports the synthesis of a polymer nanocomposite film of nano-sized Zinc Oxide and Polymethyl-methacrylate and its application in the museums and art galleries for absorbing ultra-violet radiations falling on the objects which are vulnerable to it. The Zinc Oxide nanoparticles were synthesized using facile sol–gel technique and Zinc Oxide and Polymethyl-methacrylate polymer nanocomposite was prepared by simple mixing. The size of nanoparticles and uniformity of the thin film were determined using optical and electron microscopy. Thermal stability of the Zinc Oxide and Polymethyl-methacrylate polymer nanocomposite was studied with the help of thermogravimetric analysis. The efficiency of thin coated film of synthesized polymer nanocomposite material was investigated by using a UV monitor in museum conditions.

Arsenate and arsenite adsorbents composed of nano-sized cerium oxide deposited on activated alumina

ABSTRACTCerium oxide composited activated alumina was prepared and used as arsenate and arsenite adsorbents by oxidation of cerium chloride in H2O2 solution. The preparation conditions affected arsenic adsorption capabilities in the Al2O3–CeO2. Efficient adsorption of arsenic was achieved when CeO2 was deposited on 6.0 g of powdered activated alumina at 0.01 M Ce3+ concentration and H2O2/Ce = 0.5. The arsenic adsorption was particularly enhanced in the presence of the nano-size CeO2 on the Al2O3 support, obeying the Langmuir adsorption isotherm model with maximum adsorption capacities of 13.6 and 10.5 mg/g, respectively, for arsenate and arsenite.

Development and evaluation of diffusive gradients in thin films based on nano-sized zinc oxide particles for the in situ sampling of tetracyclines in pig breeding wastewater

The pollution of antibiotics, including tetracyclines (TCs), in aquatic environments has become an issue of concern in recent years. Herein, an in situ sampling of TCs in pig breeding wastewater that utilizes the technique of diffusive gradients in thin films (DGT), based on commercial nanosized ZnO (nanoZnO) particles as the potential effective binding agent and a polyethersulfone (PES) membrane as the diffusion layer, was developed. The diffusion coefficients of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) in a PES membrane at 25 °C were (1.37 ± 0.06) × 10−6 cm2 s−1, (1.29 ± 0.05) × 10−6 cm2 s−1 and (1.94 ± 0.07) × 10−6 cm2 s−1, respectively. The results showed that the adsorption capacities of a gel disc containing 2.5 g L−1 of nanoZnO particles were as high as 3.93 ± 0.20 mg disc−1 for TC, 3.21 ± 0.20 mg disc−1 for OTC and 4.62 ± 0.22 mg disc−1 for CTC. Both a solution pH in the range of 5–9 and an ionic strength (as pNaCl) in the range of 1–3 had an insignificant influence on the TCs uptake by nanoZnO−DGT samplers. There was no significant influence of fulvic acid or tannic acid on the TC uptake by nanoZnO−DGT samplers at the tested mass ratios. For all spiked freshwater samples, there was no notable interference of matrices on the performance of the nanoZnO−DGT samplers, suggesting that the nanoZnO−DGT samplers yielded satisfactory results for the uptake of TCs at concentrations existing in the spiked freshwater samples. Field deployment of the nanoZnO−DGT samplers in pig breeding wastewater also exhibited excellent precision and accuracy, indicating that the nanoZnO−DGT samplers could be used as a promising method for the in situ sampling of TC antibiotics in aquatic environments.

Ultrasonic assisted synthesis, crystallographic, spectroscopic studies and biological activity of three new Zn(II), Co(II) and Ni(II) thiosemicarbazone complexes as precursors for nano-metal oxides

Using ultrasonic irradiations, three new complexes of type [ZnL2].CH3CN, [NiLCl] and [CoL2] (where L is 2-acetylpyridine-4N-p-chlorophenylthiosemicarbazone ligand) have been prepared and investigated using various spectroscopic methods. Crystal structures of ZnL2 and NiLCl complexes displayed distorted octahedral and square-planar coordination geometry around the central metal, respectively. The UV-visible and mass spectroscopic analysis revealed 1:2 (metal:ligand) stoichiometry for Co(II) complex. The synthesized complexes have been used as precursors for preparing their corresponding nano-sized metal oxides via thermal decomposition. The nanostructures of metal oxides were characterized by scanning electron microscope (SEM), energy dispersive X-ray (EDX), X–ray diffraction (XRD) and Fourier transform infrared (FT–IR). The in vitro antibacterial activity of thiosemicarbazone complexes and their corresponding nano-sized metal oxides were studied against a series of gram positive and gram negative bacteria, using the zone inhibition methods. While NiLCl complex was shown to possess more antimicrobial activity than its nano-sized metal oxide, the prepared nano-sized zinc and cobalt oxides have shown the highest activity.

Nanosized materials CeO2/SnO2 and CeO2/SnO2-Sb2O5 for adsorption semiconductor sensors to detect hydrogen in air

Nanosized materials based on SnO2 and SnO2 – Sb2O5 with different concentrations of added cerium were synthesized by a sol-gel method. Semiconductor gas sensors on the base of the materials were created and their characteristics (electrical resistance in air, response to hydrogen, dynamic properties) were studied. It is shown that cerium addition significantly improves the sensor response due to high catalytic activities of Ce-containing nanosized oxide materials in the H2 oxidation reaction. SnO2-based sensors were found to demonstrate higher sensitivity to hydrogen than SnO2-Sb2O5 based sensors. Possible mechanism concerning formation of the sensitivity of the Ce-containing sensors to H2 is proposed.

Progress with insulating nanocomposites based on ferrite plating of Sm2Fe17N3 micropowders

Abstract Typical exchange spring magnets are composed of two phases, a rare-earth hard magnetic material and a metallic soft magnetic material, whose magnetization value is higher than those of hard magnetic phases, such as α-Fe, Fe-B, or Fe-Co. A novel high-electrical-resistance composite magnet was fabricated by consolidating micron-sized ferromagnetic nitride Sm2Fe17N3 powder particles coated with a continuous nano-sized soft magnetic ferrite oxide layer, which suppressed intergrain conductivity but sustained the magnetic exchange interactions between grains [21] . A non-magnetic resin or ceramic insulator may suffice for the coated layer but gives rise to high electrical resistance of the magnet with large deterioration of magnetization. The soft magnetic ferrite oxide layer not only suppressed intergrain conductivity, but also only slightly reduced the magnetization of the magnet. At present, the only exchange spring magnet having a combination of a soft magnetic oxide and hard magnetic nitride is the ferrite/Sm2Fe17N3 composite magnet. Sm2Fe17N3 powder particles with a size of 2 μm were coated with an “iron ferrite” layer with a grain size of about 10 nm by ferrite plating, which is an aqueous process, following which the samples were consolidated by the explosive consolidation (EC) technique. The coercivity and rectangularity of the ferrite/Sm2Fe17N3 composite magnet decreased slightly compared to those of a Sm2Fe17N3 magnet. The fully dense ferrite/Sm2Fe17N3 magnet exhibited a resistivity of about 4000 μΩ cm, which is ten times larger than that of a fully dense Sm2Fe17N3 magnet. Thus, the soft magnetic ferrite layer in the composite magnet maintained the magnetic exchange coupling between ferromagnetic Sm2Fe17N3 grains and simultaneously suppressed intergrain electrical coupling to increase the resistivity. This decreased the eddy current loss and improved the high-frequency characteristics of the composite magnets. Therefore, ferrite/Sm2Fe17N3 composites are promising materials for magnets that are operated at high frequencies in advanced applications, such as electric vehicle magnets.