Formation Of Metal Oxide Nanoparticles Research Articles

Cu-ZnO Embedded in a Polydopamine Shell for the Generation of Antibacterial Surgical Face Masks.

A new easy protocol to functionalize the middle layer of commercial surgical face masks (FMs) with Zn and Cu oxides is proposed in order to obtain antibacterial personal protective equipment. Zinc and copper oxides were synthesized embedded in a polydopamine (PDA) shell as potential antibacterial agents; they were analyzed by XRD and TEM, revealing, in all the cases, the formation of metal oxide nanoparticles (NPs). PDA is a natural polymer appreciated for its simple and rapid synthesis, biocompatibility, and high functionalization; it is used in this work as an organic matrix that, in addition to stabilizing NPs, also acts as a diluent in the functionalization step, decreasing the metal loading on the polypropylene (PP) surface. The functionalized middle layers of the FMs were characterized by SEM, XRD, FTIR, and TXRF and tested in their bacterial-growth-inhibiting effect against Klebsiella pneumoniae and Staphylococcus aureus. Among all functionalizing agents, Cu2O-doped-ZnO NPs enclosed in PDA shell, prepared by an ultrasound-assisted method, showed the best antibacterial effect, even at low metal loading, without changing the hydrophobicity of the FM. This approach offers a sustainable solution by prolonging FM lifespan and reducing material waste.

Label-Free Electrochemical Sensor Based on Manganese Doped Titanium Dioxide Nanoparticles for Myoglobin Detection: Biomarker for Acute Myocardial Infarction.

A label free electrochemical sensor based on pure titanium oxide and manganese (Mn)-doped titanium oxide (TiO2) nanoparticles are fabricated and characterized for the sensitive detection of myoglobin (Mb) levels to analyze the cardiovascular infarction. Pristine and Mn-doped TiO2 nanoparticles were synthesized via the sol-gel method and characterized in order to understand their structure, morphologies, composition and optical properties. The structural properties revealed that the pure- and doped-TiO2 nanoparticles possess different TiO2 planes. FTIR studies confirm the formation of metal oxide nanoparticles by exhibiting a well-defined peak in the range of 600–650 cm−1. The values of the optical band gap, estimated from UV-Vis spectroscopy, are decreased for the Mn-doped TiO2 nanoparticles. UV-Vis spectra in the presence of myoglobin (Mb) indicated interaction between the TiO2 nanoparticles and myoglobin. The SPE electrodes were then fabricated by printing powder film over the working electrode and tested for label-free electrochemical detection of myoglobin (Mb) in the concentration range of 0–15 nM Mb. The fabricated electrochemical sensor exhibited a high sensitivity of 100.40 μA-cm−2/nM with a lowest detection limit of 0.013 nM (0.22 ng/mL) and a response time of ≤10 ms for sample S3. An interference study with cyt-c and Human Serum Albumin (HSA) of the sensors show the selective response towards Mb in 1:1 mixture.

In-Situ Growth of Metal Oxide Nanoparticles on Cellulose Nanofibrils for Dye Removal and Antimicrobial Applications

Nanocellulose is known to act as a platform for the in-situ formation of metal oxide nanoparticles, where the multiple components of the resultant hybrids act synergistically toward specific applications. However, typical mineralization reactions require hydrothermal conditions or addition of further reducing agents. Herein, we demonstrate that carboxylated cellulose nanofibril-based films can spontaneously grow functional metal oxide nanoparticles during the adsorption of heavy metal ions from water, without the need of any further chemicals or temperature. Despite the apparent universality of this behavior with different metal ions, this work focuses on studying the in-situ formation of copper oxide nanoparticles on TOCNF films as well as the resultant hybrid films with improved functionality toward dye removal from water and antimicrobial activity. Using a combination of cutting-edge techniques (e.g., in-situ SAXS and QCMD) to systematically follow the nanoparticle formation on the nanocellulosic films in real time, we suggest a plausible mechanism of assembly. Our results confirm that carboxylated cellulose nanofibril films act as universal substrate for the formation of metal oxide nanoparticles, and thus hybrid nanomaterials, during metal ion adsorption processes. This phenomenon enables the upcycling of nanocellulosic materials through multistage applications, thus increasing its sustainability and efficiency in terms of an optimal use of resources.

Molecular-Level Understanding of Continuous Growth from Iron-Oxo Clusters to Iron Oxide Nanoparticles.

The formation of inorganic nanoparticles has been understood based on the classical crystallization theory described by a burst of nucleation, where surface energy is known to play a critical role, and a diffusion-controlled growth process. However, this nucleation and growth model may not be universally applicable to the entire nanoparticle systems because different precursors and surface ligands are used during their synthesis. Their intrinsic chemical reactivity can lead to a formation pathway that deviates from a classical nucleation and growth model. The formation of metal oxide nanoparticles is one such case because of several distinct chemical aspects during their synthesis. Typical carboxylate surface ligands, which are often employed in the synthesis of oxide nanoparticles, tend to continuously remain on the surface of the nanoparticles throughout the growth process. They can also act as an oxygen source during the growth of metal oxide nanoparticles. Carboxylates are prone to chemical reactions with different chemical species in the synthesis such as alcohol or amine. Such reactions can frequently leave reactive hydroxyl groups on the surface. Herein, we track the entire growth process of iron oxide nanoparticles synthesized from conventional iron precursors, iron-oleate complexes, with strongly chelating carboxylate moieties. Mass spectrometry studies reveal that the iron-oleate precursor is a cluster comprising a tri-iron-oxo core and carboxylate ligands rather than a mononuclear complex. A combinatorial analysis shows that the entire growth, regulated by organic reactions of chelating ligands, is continuous without a discrete nucleation step.

Montmorillonites supported with metal oxide nanoparticles for decontamination of sulfur mustard

The montmorillonites supported with MgO, MnO2, Fe2O3, CoO, NiO, CuO, ZnO, CeO2, and Ag2O nanoparticles were made by ion exchange, precipitation, and successive calcination. Prepared solids were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive analysis of X-rays, nitrogen adsorption, and gravimetric techniques. X-ray diffraction data depicted the maintenance of the host structure during synthesis of montmorillonites supported with metal oxide nanoparticles. It also indicated the presence of crystallites of MnO2, Fe2O3, CuO, ZnO, CeO2, and Ag2O metal oxide nanoparticles on the respective montmorillonite supported materials. The absence of corresponding diffraction peaks of MgO, CoO, and NiO metal oxide nanoparticles in the respective montmorillonite supported materials indicated that the concentration of the crystalline nanoparticles was low on the surface. Transmission electron microscopy data indicated the formation of metal oxide nanoparticles of size varying from 2 to 11nm on the external surface of montmorillonites. Significant decrease in the values of specific surface area and pore volume indicated the partial blocking of pores of montmorillonites by metal oxide nanoparticles. These materials were used for decontamination of sulfur mustard. Montmorillonite supported Ag2O nanoparticles demonstrated superior decontamination efficiency against sulfur mustard. It chemically degraded 100% of sulfur mustard within 2h, whereas other materials took up to 16h to completely degrade the same. Bare montmorillonite displayed least decontamination efficiency among all materials toward sulfur mustard. It decontaminated only 90% of sulfur mustard in 24h.

Ni(II), Cu(II), AND Zn(II) COMPLEXES DERIVED FROM A NEW SCHIFF BASE 2-((Z)-(3-METHYLPYRIDIN-2-YLEIMINO)METHYL)PHENOL AND SYNTHESIS OF NANO SIZED METAL OXIDE PARTICLES FROM THESE COMPOUNDS

Synthesis, spectral identification, and magnetic properties of three complexes of Ni(II), Cu(II), and Zn(II) are described. All three compounds have the general formula [M(L)2(H2O)2], where L = deprotonated phenol in the Schiff base 2-((z)-(3-methylpyridin-2-yleimino)methyl)phenol. The three complexes were synthesized in a one-step synthesis and characterized by elemental analysis, Fourier transform infrared spectroscopy, electronic spectra, X-ray diffraction (XRD), and room temperature magnetic moments. The Cu(II) and Ni(II) complexes exhibited room temperature magnetic moments of 1.85 B.M. per copper atom and 2.96 B.M. per nickel atom. The X-band electron spin resonance spectra of a Cu(II) sample in dimethylformamide frozen at 77 K (liquid nitrogen temperature) showed a typical ΔMS = ± 1 transition. The complexes ([M(L)2(H2O)2]) were investigated by the cyclic voltammetry technique, which provided information regarding the electrochemical mechanism of redox behavior of the compounds. Thermal decomposition of the complexes at 750 oC resulted in the formation of metal oxide nanoparticles. XRD analyses indicated that the nanoparticles had a high degree of crystallinity. The average sizes of the nanoparticles were found to be approximately 54.3, 30.1, and 44.4 nm for NiO, CuO, and ZnO, respectively.

Controlled surface mineralization of metal oxides on nanofibers

Metal oxide/polymer hybrid nanofibers are prepared by in situ formation of metal oxide nanoparticles on surface-functionalized polymer fibers.

Molecular sieves supported with metal oxide nanoparticles: synthesis, characterization and decontamination of sulfur mustard

Molecular sieves supported with MgO, CaO, NiO, CuO, Ag2O, MnO2, CeO2, Fe2O3 nanoparticles were synthesized by ion exchange, precipitation, and subsequent calcination. They were characterized by transmission electron microscopy, X-ray diffraction, nitrogen adsorption, and gravimetric techniques. Transmission electron microscopy data indicated the formation of metal oxide nanoparticles of size varying from 1.2 to 25 nm on the external surface of molecular sieves. X-ray diffraction revealed the preservation of the host structure during the synthesis. Reduction in surface areas and pore sizes indicated the partial blocking of pores of molecular sieves by metal oxide nanoparticles. These materials were used for decontamination of sulfur mustard. Molecular sieve supported with Ag2O nanoparticles showed greater decontamination efficiency when compared to molecular sieves supported with other materials. Molecular sieve supported with Ag2O nanoparticles chemically degraded 100 % of sulfur mustard within 16 h. Furthermore, molecular sieves supported with other materials showed better decontamination efficiency when compared to bare molecular sieve which decontaminated only 66 % of sulfur mustard in 48 h.

A facile thermal-treatment route to synthesize the semiconductor CdO nanoparticles and effect of calcination

In this research, a thermal treatment method was used to synthesize cadmium oxide nanoparticles. The metal precursor, cadmium nitrate and a capping agent were dissolved in deionized water, which later was dried and crushed into powder. The powder underwent calcination treatment of 500, 550, 600, and 650°C to crystallize the nanoparticles and to remove organic compounds. The structural studies of CdO nanoparticles have been carried out using EDAX, FTIR, XRD, SEM and TEM. The FTIR and XRD spectra showed that the crystalline structure formation of metal oxide nanoparticles has only occurred after been exposed to calcination. The optical properties which were determined using a UV–vis spectrophotometer showed a decrease in the band gap with increasing calcination temperature. These results prove that the thermal treatment method is a simple technique that can produce pure metal oxide nanoparticles with no other chemicals added.

Metal Oxide Nanocrystals from the Injection of Metal Oxide Sols in a Coordinating Environment: Principles, Applicability, and Investigation of the Synthesis Variables in the Case Study of CeO2 and SnO2

Metal oxide sols (ZnO, SnO2, TiO2, ZrO2, Fe2O3, NiO, Ga2O3, MnO2, In2O3, CeO2) were prepared by hydrolysis of chloro-alkoxo or acetylacetonato complexes, preventing precipitation. The sols were injected in a solution of tetradecene and an aliphatic amine at 160 °C and heated at the resulting temperature for 3 h, resulting in the formation of metal oxide nanoparticles. The crystallization degree of the resulting nanoparticles depended on the particular system, and nanocrystals were obtained for ZnO, SnO2, Fe2O3, Ga2O3, In2O3, CeO2 systems. The chemical features of the process were investigated on SnO2 and CeO2 as case systems, by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and nuclear magnetic resonance. The initial hypothesis that the amine present in the injection solution may act at the same time as a catalyst of the inorganic condensation reactions and as a growth stopper by bonding to the surface metal atoms of the nanoparticles, was thoroughly investigated and it resulted that the alkylamine structure and the processing of the starting sol can influence the nanocrystal formation pathway. In particular, bulkier amines favor the formation of smaller nanocrystals, whereas favoring the condensation reactions in the starting sols results in larger nanocrystals.

In vitro selection of RNA sequences capable of mediating the formation of iron oxide nanoparticles

In vitro selection experiments involving RNA, phagemids, or whole cells can yield biomolecules that bind tightly to or mediate the formation of inorganic materials. Herein we show that RNA sequences that mediate the formation of metal oxide nanoparticles can be isolated from iterative cycles of RNA selection and amplification. In contrast to prior work, the in vitro selection described within was based upon a desired materials property. In order to be isolated from a starting random sequence pool, an RNA sequence was required to mediate the assembly of Co and/or Fe into a solid that responded to a magnetic field. Sequences isolated from this selection were able to mediate the formation of iron oxide nanoparticles containing small amounts of Co under atypical synthesis conditions of temperature and pH.

Highly-dispersed and thermally-stable NiO nanoparticles exclusively confined in SBA-15: Blockage-free nanochannels

In this work, exclusive formation of metal oxide nanoparticles confined in ordered mesoporous supports was achieved by a hydrophobic encapsulation route illustrated with the NiO/SBA-15 system. Uniform, discrete and thermally-stable NiO nanoparticles are well-distributed in a confined space. The confined nanoparticles possessed high thermal stability, the average size only slightly increasing from 2.83 nm to 3.69 nm after treatment at 900 °C. The NiO-confined nanochannels show no blockages, even though the NiO loading is as high as 18.55 wt%. This blockage-free nanoarchitecture greatly enhances application in catalysis, as demonstrated by the methanation reaction, for which the new catalyst was ∼18.5 times as effective as conventional types.

Porous Co3O4 Nanotubes Derived From Co4(CO)12 Clusters on Carbon Nanotube Templates: A Highly Efficient Material For Li‐Battery Applications

Over the past decades, a worldwide effort has been made to search for alternative anode materials of lithium batteries for improving their energy density and safety. It has been found that 3d transition metal oxides such as nickel oxide, cobalt oxide, and iron oxide exhibit reversible capacities about three times larger than those of graphite (372 mAh g) at a relative low potential, which greatly spurs the rapid development in this field. Among them, cobalt oxides (Co3O4 and CoO) have shown the highest capacity (700 mAh g) and best cycle performance (93.4 % of initial capacity was retained after 100 cycles), compared with nickel oxide (NiO) and iron oxides (Fe2O3 and Fe3O4). [3] In recent years, the nanostructured materials have attracted great interest in the application of anode or cathode materials for lithium batteries because of their high surface-to-volume ratio and short path length for Li transport. As a result, it is believed that the Co3O4 nanomaterials can exhibit the superior Li-battery performance. Previously, several Co3O4 nanostructures such as nanoparticles, nanowires, and nanotubes were prepared by different methods. Among them, the nanotubes have been considered one of the most promising structures for lithium batteries due to their higher surface-to-volume ratio than other one-dimensional nanostructures such as nanowires and more difficult for aggregation in comparison with nanoparticles. By far, there is little literature about the synthesis and application of Co3O4 nanotubes for lithium batteries. For example, Chen et al. synthesized the Co3O4 nanotubes via the anodic aluminum oxide (AAO) template route and applied them for lithium batteries with the capacity of about 800 mAh g at the current density of 50 mA g. However, there are some disadvantages for the AAO template assisted approach to synthesize metal oxide nanotubes, which restrict their application in Libattery. Firstly, the mass production of metal oxide nanotubes prepared by such an approach is impracticable, which is one of the bottlenecks for their wide applications. Secondly, it is very difficult to completely remove the nanoporous alumina template. Thirdly, the diameters of metal oxide nanotubes prepared by such an approach are usually larger than 100 nm. Recently, carbon nanotubes (CNTs) have been considered to be an ideal template for the synthesis of metal oxide nanotubes due to the mass production, being easily removed and small diameter. For example, Liu et al. reported the synthesis of Fe2O3/CNTs core-shell nanostructures and polycrystalline Fe2O3 nanotubes by supercritical fluids approach using CNTs as templates. Unfortunately, the high temperature and pressure were needed in this approach. In addition, metal oxide/ CNTs core-shell nanostructures and metal oxide nanotubes were also achieved by CNT-template assisted chemical vapor deposition (CVD), which operated at high temperature and, moreover, only deposited oxides on the top surface of CNTs. Furthermore, metal oxide/CNTs core-shell nanostructures were also fabricated by chemical precipitation method. However, the formation of metal oxide nanoparticles in the solution or metal oxide with very large grain size on the surface of CNTs was inevitable in this approach, which made it difficult to form metal oxide nanotubes after oxidation of CNTs. Very recently, we have developed a novel approach to synthesizing the porous and polycrystalline In2O3 nanotubes by layer-by-layer assembly on CNT templates in combination with subsequent calcinations, which exhibit superior gas sensing performance. Herein, we report a novel sonochemistry method to synthesizing CNTs-CoOx nanocables derived from Co4(CO)12 clusters on CNT templates at room temperature and subsequent transformation into uniform porous Co3O4 nanotubes by the calcination. Moreover, the assynthesized porous Co3O4 nanotubes have been applied in anode materials for lithium batteries, which exhibit the superior performance and thus promising application. Firstly, Co4(CO)12 and CNTs were mixed in hexane and sonicated for 1 h at room temperature. During the sonication, Co4(CO)12 can be readily decomposed to Co and CO, as shown in Reaction 1. Secondly, Co atom can be rapidly oxidized into CoOx due to the oxygen atmosphere in the solution, as illustrated in Reaction 2. Thirdly, CoOx with positive charge can be compactly deposited on the surface of CNTs C O M M U N IC A IO N

Porous Indium Oxide Nanotubes: Layer‐by‐Layer Assembly on Carbon‐Nanotube Templates and Application for Room‐Temperature NH3 Gas Sensors

Indium oxide (In2O3), as an n-type and wide-bandgap semiconductor, is of great interest for use in toxic-gas detectors, solar cells, and light-emitting diodes because of its high electrical conductivity and high transparency. In particular, In2O3 has been extensively applied in film-based chemical sensors for a long time. However, In2O3-film-based sensing devices possess several critical limitations such as a limited maximum sensitivity and high operation temperatures (200–600 °C). In2O3 nanostructured materials, possessing ultrahigh surface-to-volume ratios, are expected to be superior gas-sensor candidates that may overcome the fundamental limitations as mentioned above. Therefore, considerable efforts have been devoted to synthesizing In2O3 nanostructures such as nanoparticles, nanowires, nanotubes, and nanobelts. Among them, nanotubes are believed to be one of the most promising structures for chemical sensors because of their higher surface-to-volume ratios and, moreover, they do not aggregate as easily as nanoparticles. Up to now, template-assisted approaches have been widely used to synthesize metal oxide nanotubes. Metal oxide nanotubes prepared by template-assisted approaches possess higher surface-to-volume ratios than those prepared by template-free approaches because of their polycrystalline and porous structure, and, therefore, may display a more superior gas-sensor performance. As a result, owing to the simplicity in the synthesis of nanotubes and their availability, quite a few metal oxide nanotubes have been fabricated by nanoporous alumina template assisted approaches such as Ga2O3, In2O3, TiO2, and Fe2O3. [8] Nevertheless, there are some disadvantages in using nanoporous alumina as a template to synthesize metal oxide nanotubes. Firstly, mass production of metal oxide nanotubes by such an approach is impractical, which is one of the bottlenecks for their wide application. Secondly, it is very difficult to completely remove the nanoporous alumina template. Thirdly, the diameters of the prepared metal oxide nanotubes by such an approach are usually larger than 100 nm. Recently, carbon nanotubes (CNTs) have been considered to be an ideal template for the synthesis of metal oxide nanotubes, which can circumvent the disadvantages of nanoporous alumina as mentioned above. For example, Rao and co-workers first fabricated ZrO2, Al2O3, V2O5, SiO2, and MoO3 nanotubes by a metal-alkoxide-based sol–gel process using CNTs as templates in combination with subsequent calcination. However, the deliquescence, toxicity, and high cost of metal alkoxides, as well as the long reaction time, restrict the practical applications of this approach. Liu and co-workers reported the synthesis of Fe2O3/CNT core–shell nanostructures and polycrystalline Fe2O3 nanotubes by a supercritical-fluid-approach using CNTs as templates. Unfortunately, this approach needed to be carried out at high temperature and pressure. In addition, metal oxide/CNT core–shell nanostructures and metal oxide nanotubes have been obtained by CNT-template-assisted chemical vapor deposition (CVD), which was also carried out at high temperature and, moreover, only resulted in the deposition of oxides on the top surface of the CNTs. Metal oxide/CNT core–shell nanostructures were also fabricated by a chemical precipitation method. However, in this route, the formation of metal oxide nanoparticles in the solution or metal oxides with a very large grain size on the surface of the CNTs was inevitable, which made it difficult to form metal oxide nanotubes after oxidation of the CNTs. We report a novel and versatile approach to synthesize metal oxide nanotubes using layer-by-layer (LBL) assembly on the CNT templates in combination with subsequent calcination. LBL assembly is based on the electrostatic attraction between charged species and it has been widely used to synthesize polymeric multicomposites, inorganic and hybrid hollow spheres, polymer nanotubes, and core–shell nanostructures. We now present its use, for the first time, to synthesize metal oxide nanotubes including In2O3, NiO, SnO2, Fe2O3, and CuO. Of these, In2O3 nanotubes are used to illustrate the basic idea underlying the approach presented in this work. The as-synthesized In2O3 nanotubes were applied in an NH3 gas sensor operated at room temperature, which exhibits improved performance and thus promising applications. C O M M U N IC A IO N

Formation of metal oxide nanoparticles in combustion of titanium and aluminum droplets

A study was performed of the formation of metal oxide nanoparticles during combustion of aluminum and titanium drops which moved in air at a velocity of up to 3 m/sec. The source of the burning particles was a pyrotechnic mixture which contained an oxidizer, a binder, and metal particles of size 4–350 µm. Transmission electron microscopic studies showed that the combustion products were 1–10 µm aggregates of fractal structure consisting of primary particles (spherules) of Al2O3/TiO2 5–150 nm in diameter. The Brownian diffusion of the aggregates and their motion in electric and gravitational fields were observed using videomicroscopic recording. The charge distribution of TiO2 aggregates and the equivalent radius of Brownian mobility were determined. In Al combustion, the zone of nanoparticle formation is separated from the particle surface by a distance approximately equal to the particle radius, and in Ti combustion, this zone is located directly near the surface. Coagulation of the oxide aerosol in the track of a burning particle leads to aerogelation with the formation of huge aggregates. Analytical expressions for approximate calculation of the parameters of the oxide particles and zones of their formation are proposed.