MgO Nanostructures Research Articles

MgO nanostructure via a sol-gel combustion synthesis method using different fuels: An efficient nano-adsorbent for the removal of some anionic textile dyes

Magnesium oxide nanostructures were synthesized via a sol-gel combustion method using urea, oxalic acid, and citric acid fuels. The effect of the fuel type on the products was studied. The as-prepared products were characterized by means of FE-SEM, HR-TEM, XRD, and FT-IR analyses. The results exhibited that the used fuels gave MgO products with different morphologies, and the oxalic acid fuel produced pure MgO nanoparticles with the smallest crystallite size (ca. 12nm). The adsorption properties of the MgO products for the removal of Reactive Red 195 (RR195) and Orange G (OG) anionic dyes were examined. Using a batch method, various parameters affecting the adsorption properties were studied. The results revealed that MgO nanostructure generated from the oxalic acid fuel had the highest adsorption capacities (207 and 21.5mg/g for RR195 and OG dyes, respectively). Additionally, the adsorption data followed the pseudo-second-order kinetic model and Langmuir adsorption isotherm model. And the adsorption process was controlled by intra-particle diffusion, bulk diffusion, and film diffusion mechanisms. Besides, the thermodynamic study showed that the adsorption of the textile dyes of interest on the as-prepared MgO nanostructures was an exothermic, physisorption and spontaneous process.

Facile and scalable synthesis of uniform MgO/Carbon Black nano-admixture for microstructural and mechanical property improvement of magnesia-carbon refractory bricks

Facile and scalable synthesis method of MgO/Carbon Black nano-admixture as an additive for MgO/C refractory bricks has been developed via simple precipitation method. The main idea of the present work lies on the precipitation of magnesium hydroxide in well dispersed/stabilized carbon black nanoparticle suspension resulting in Mg(OH)2/CB nano-admixture preparation. Furthermore, applying such colloidal suspension of CBs prevent the sever agglomeration of Mg-containing precipitate and make simple precipitation method as a reliable synthesis method of nano-structured MgO. Finally, different analytical methods including X-ray diffractometer, Scanning electron microscopy, Cold crushing strength and physical properties measurement have been utilized to study the effect of such nano-admixture on the microstructural and mechanical properties of typical MgO/C refractory bricks.

Development of high oxidation resistant coating of nanostructured MgO on carbon nanotubes via simple precipitation technique in Mg/CO gas system

The synthesis of oxide-coated carbon nanotubes (CNTs) by a simple precipitation reaction in Mg/CO gaseous system was studied. The results showed that nanostructured MgO could be uniformly coated on the surface of CNTs via inhomogeneous Mg(g) and CO(g) precipitation reaction. Furthermore, we have developed a mixing procedure based on simultaneous agitation and ultra-sonication in order to break CNT bundles and prepare highly dispersed starting materials. By applying such mixing procedure, dispersed and distinct nano-oxide coated CNTs were synthesized which can be efficiently utilized in different composite matrices. Oxidation resistance of samples was investigated by DSC/TG thermal analysis. The results showed that oxide-coated CNTs present superior resistance against oxidation even at rather elevated temperature of 1000°C and total weight loss of coated CNTs was measured to be less than 1wt% during heat treatment at such temperature. Finally, coating adhesion was evaluated employing ultrasonic waves (as mechanical force) and subsequent weight loss measurement at temperature of 1000°C.

Application of flowerlike MgO for highly sensitive determination of lead via matrix-assisted laser desorption/ionization mass spectrometry.

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) is a high-throughput method to achieve fast and accurate identification of lead (Pb) exposure, but is seldom used because of low ionization efficiency and insufficient sensitivity. Nanomaterials applied in MS are a promising technique to overcome the obstacles of MALDI. Flowerlike MgO nanostructures are applied for highly sensitive lead profiling in real samples. They can be used in two ways: (a) MgO is mixed with N-naphthylethylenediamine dihydrochloride (NEDC) as a novel matrix MgO/NEDC; (b) MgO is applied as an absorbent to enrich Pb ions in very dilute solution. The signal intensities of lead by MgO/NEDC were ten times higher than the NEDC matrix. It also shows superior anti-interference ability when analyzing 10μmol/L Pb ions in the presence of organic substances or interfering metal ions. By applying MgO as adsorbent, the LOD of lead before enrichment is 1nmol/L. Blood lead test can be achieved using this enrichment process. Besides, MgO can play the role of internal standard to achieve quantitative analysis. Flowerlike MgO nanostructures were applied for highly sensitive lead profiling in real samples. The method is helpful to prevent Pb contamination in a wide range. Further, the combination of MgO with MALDI MS could inspire more nanomaterials being applied in highly sensitive profiling of pollutants. Copyright © 2016 John Wiley & Sons, Ltd.

A facile, novel and low-temperature synthesis of MgO nanorods via thermal decomposition using new starting reagent and its photocatalytic activity evaluation

Herein, the MgO nanorods were successfully synthesized via a facile, novel and solvent-free thermal decomposition route at low temperature using Mg–MOF as a new starting reagent for the first time. The Mg–MOF was prepared via fast microwave-based method using 2,6-pyridinedicarboxylic acid ammonium and Mg(NO3)2·2H2O. Furthermore, the efficiency of MgO nanostructures as a photocatalyst for decolorization of methylene blue (MB) under visible light irradiation has been evaluated. The synthesized MgO nanostructures exhibited appreciable photocatalytic activity and in presence of MgO, 90% degradation of MB was obtained after 180min.

Green solvent ionic liquids: structural directing pioneers for microwave-assisted synthesis of controlled MgO nanostructures

Various MgO nanostructures were obtained via one-pot microwave-assisted synthesis in various structural directing ionic liquids.

Effect of anion type on the synthesis of mesoporous nanostructured MgO, and its excellent adsorption capacity for the removal of toxic heavy metal ions from water

MgO nanostructures with controllable morphology and tunable textural properties synthesized via aqueous based route in the absence of organic templates were found to be excellent adsorbent for the removal of Pb(ii) and Cd(ii) ions from water.

Facile synthesis of defect-induced highly-luminescent pristine MgO nanostructures for promising solid-state lighting applications

Successful demonstration of the facile synthesis of defect-induced highly-luminescent pristine MgO nanostructures for white-light generation and proposed WLED application.

Porphyrin Metalation at MgO Surfaces: A Spectroscopic and Quantum Mechanical Study on Complementary Model Systems.

We show that both single-crystalline and nanostructured MgO surfaces convert free-base tetraphenyl porphyrin (2HTPP) into magnesium tetraphenyl porphyrin (MgTPP) at room temperature. The reaction can be viewed as an ion exchange between the two aminic protons of the 2HTPP molecule with a Mg(2+) ion from the surface. The driving force for the reaction is the strong stability of the formed hydroxyl groups along the steps and at defects on the MgO surface. We have used an integrated characterization approach that includes UV/Vis diffuse reflectance measurements on nanostructured powders, X-ray photoelectron spectroscopic investigation of atomically clean MgO(100) single-crystalline thin films, and density functional theory (DFT) calculations on model systems. The DFT calculations demonstrate that MgTPP formation is strongly exothermic at the corners, edges and steps, but slightly endothermic on terrace sites. This agrees well with the UV/Vis diffuse reflectance, which upon adsorption of 2HTPP shows a decrease in the absorption band associated with corner and edge sites on MgO nanocube powders.

Synthesis and Characterization of Mg(OH)2 and MgO Nanostructures Via Simple Hydrothermal Method

Mg(OH)2 and MgO nanostructures were synthesized via simple hydrothermal method by MgSO4, ethylenediamine, and hydrazine as reagents. The products were characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Different parameter's effect on product size and morphology was investigated.

Sonocatalyzed decolorization of synthetic textile wastewater using sonochemically synthesized MgO nanostructures

The present study focused on the synthesis of nanostructured MgO via sonochemical method and its application as sonocatalyst for the decolorization of Basic Red 46 (BR46) dye under ultrasonic irradiation. The sonocatalyst was characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray microanalysis (EDX). In the following, the sonocatalytic removal of the dye under different operational conditions was evaluated kinetically on the basis of pseudo first-order kinetic model. The reaction rate of sonocatalyzed decolorization using MgO nanostructures (12.7×10−3min−1) was more efficient than that of ultrasound alone (2.0×10−3min−1). The increased sonocatalyst dosage showed better sonocatalytic activity but the application of excessive dosage should be avoided. The presence of periodate ions substantially increased the decolorization rate from 14.76×10−3 to 33.4×10−3min−1. Although the application of aeration favored the decolorization rate (17.8×10−3min−1), the addition of hydrogen peroxide resulted in a considerable decrease in the decolorization rate (9.5×10−3min−1) due to its scavenging effects at specific concentrations. Unlike alcoholic compounds, the addition of phenol had an insignificant scavenging effect on the sonocatalysis. A mineralization rate of 7.4×10−3min−1 was obtained within 120min. The intermediate byproducts were also detected using GC–MS analysis.

Structure sensitivity of the oxidative activation of methane over MgO model catalysts: I. Kinetic study

The role of surface structure and defects in the oxidative coupling of methane (OCM) was studied over magnesium oxide as a model catalyst. Pure, nano-structured MgO catalysts with varying primary particle size, shape and specific surface area were prepared by sol–gel synthesis, oxidation of metallic magnesium, and hydrothermal post treatments. The initial activity of MgO in the OCM reaction is clearly structure-sensitive. Kinetic studies reveal the occurrence of two parallel reaction mechanisms and a change in the contribution of these pathways to the overall performance of the catalysts with time on stream. The initial performance of freshly calcined MgO is governed by a surface-mediated coupling mechanism involving direct electron transfer between methane and oxygen. The two molecules are weakly adsorbed at structural defects (steps) on the surface of MgO. The proposed mechanism is consistent with high methane conversion, a correlation between methane and oxygen consumption rates, and high C2H4 selectivity after short times on stream. The water formed in the OCM reaction causes sintering of the MgO particles and loss of active sites by degradation of structural defects, which is reflected in decreasing activity of MgO with time on stream. At the same time, gas-phase chemistry becomes more important, which includes the formation of ethane by coupling of methyl radicals formed at the surface and the partial oxidation of C2H6. The mechanistic concepts proposed in this work (Part I) will be substantiated in Part II by spectroscopic characterization of the catalysts (Schwach et al. [1]).

Novel approach for the synthesis of Mg(OH)2 nanosheets and lamellar MgO nanostructures and their ultra-high adsorption capacity for Congo red

Abstract

MgO nanomaterials with different morphologies and their sorption capacity for removal of toxic dyes

MgO nanorods, hierarchical nanostructures and nanoflakes were synthesized by precipitation, reflux and hydrothermal methods, respectively. The SEM and FESEM images suggested the formation of nanorods with diameter around 400–500nm, hierarchical nanostructures containing plates with thickness around 100–200nm and nanoflakes with diameter around 300–500nm. XRD and FTIR confirmed the formation of single phase MgO with well crystalline nature. The hierarchical MgO nanostructures possessed higher specific surface area (147.5m2/g) than MgO nanorods (48.45m2/g) and nanoflakes (110.9m2/g). The prepared nanomaterials were used as adsorbents to remove organic dyes such as Malachite green and Congo red from aqueous media. The percentage of removal of Malachite green by MgO nanorods, hierarchical nanostructures and nanoflakes are 95.1, 99.98 and 97.42%, respectively, and percentage of removal of Congo red by MgO nanorods, hierarchical nanostructures and nanoflakes are 86.28, 99.94 and 92.68%, respectively. The hierarchical MgO nanostructure exhibited excellent adsorption performance for removal of Malachite green and Congo red with maximum sorption capacities of 1205.23 and 1050.81mg/g, respectively.

Multi-particle assembled porous nanostructured MgO: its application in fluoride removal

In this article, a simple and economical route based on ethylene glycol mediated process was developed to synthesize one-dimensional (1D) multiparticle assembled nanostructured MgO using magnesium acetate and urea as reactants. Porous multiparticle chain-like MgO has been synthesized by the calcination of a solvothermally derived single nanostructured precursor. The prepared products were characterized by an x-ray diffraction (XRD) pattern, thermogravimetry, scanning/transmission electron microscopy (SEM/TEM) and N2 adsorption (BET). As a proof of concept, the porous multiparticle chain-like MgO has been applied in a water treatment for isolated and rural communities, and it has exhibited an excellent adsorption capability to remove fluoride in waste water. In addition, this method could be generalized to prepare other 1D nanostructures with great potential for various attractive applications.

Electrochemical biosensor based on one-dimensional MgO nanostructures for the simultaneous determination of ascorbic acid, dopamine, and uric acid

One-dimensional (1D) MgO nanostructures of various morphologies including tadpole-like nanobelts (tadpoles), nanobelts, and nanorods were synthesized via direct current (DC) arc plasma jet chemical vapor deposition (CVD). The effect of morphology on the biosensing properties of the nanostructures was investigated by comparing their electrochemical properties. Compared with tadpoles and nanorods, the MgO nanobelts had excellent electrocatalytic activity toward ascorbic acid (AA), dopamine (DA) and uric acid (UA). The response of the MgO nanobelts to the analytes was twice that of the tadpoles. A MgO nanobelt-modified electrode was thus fabricated for the simultaneous determination of AA, DA, and UA. The peak separations between AA and DA, DA and UA, and AA and UA for this electrode were 111, 161, and 272mV, respectively. The linear response ranges of the electrodes were 2.5–15 and 25–150μM for AA, 0.125–7.5μM for DA, and 0.5–3 and 5–30μM for UA. The calculated detection limits were 0.2, 0.05, and 0.04μM (S/N=3), respectively. The excellent electrocatalytic activity of the MgO nanobelts can be attributed to various surface defects such as low-coordination anions (O5C2− and O4C2− at the terrace and edge sites, and O3C2− at the corner and kink sites). Additionally, electron tunneling between these surface defects is possible. These defects have a strong adsorption capacity toward AA, DA, and UA. This affinity improves sensitivity and decreases the detection limits of the MgO nanobelt electrodes.

Synthesis of nanostructured MgO powders with photoluminescence by plasma-intensified pyrohydrolysis process of bischofite from brine

Abstract Nanostructured MgO powders were synthesized by an ultra-high temperature pyrohydrolysis process of bischofite (MgCl2·6H2 O) in a radio frequency (RF) induction thermal plasma system. The structure, morphology and optical properties were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The results showed that MgO nanopowders with two different morphologies were fabricated: near spherical MgO nanoparticles with size in the range of 20∼40 nm and 1D nanobelts with a width of about 100 nm. The photoluminescence (PL) studies showed that both of these two kinds of nanostructured MgO powders exhibited a strong ultraviolet-green PL emission under the excitation of 325 nm He-Ne laser.

Simple and Economical Method for the Preparation of MgO Nanostructures with Suitable Surface Area

A facile and simple method was proposed to control the size and shape of the MgO nano structures with high surface area in the presence of efficient and cheap templates like PEG 200, PEG 600, PEG 4000 and sorbitol at low temperature within a little time. Nano rods and Nanoparticles have been achieved by applying these templates and altering other growth parameters. The products were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Thermo Gravimetric Analysis (TGA). The surface area of the samples was characterized by BET method. The effect of the growth parameters such as template, pH, Mg2+/template, molar ratio and temperature on the growth and morphology of MgO nano structures have been investigated in details. By tuning these parameters MgO nano rods and nano particles can be formed.

Elevated temperature CO2 capture on nano-structured MgO–Al2O3 aerogel: Effect of Mg/Al molar ratio

Nano-structured MgO–Al2O3 aerogel adsorbents (denoted as MgAl-AE-X) with different Mg/Al molar ratio (X) were prepared by a single-step epoxide-driven sol–gel method and a subsequent CO2 supercritical drying method. The effect of Mg/Al molar ratio of nano-structured MgO–Al2O3 aerogel adsorbents on their physicochemical properties and CO2 adsorptive performance at elevated temperature (200°C) was investigated. Successful formation of flower-like nano-structured MgAl-AE-X adsorbents was confirmed by N2 adsorption–desorption isotherms and SEM analyses. The crystalline structure of MgAl-AE-X adsorbents was transformed in the sequence of Al2O3→MgAl2O4→MgO-MgAl2O4 with increasing Mg/Al molar ratio from 0 to 3. All the MgAl-AE-X adsorbents were found to possess weak base site and medium base site except for strong base site. In the dynamic CO2 adsorption, both the total CO2 capacity and the 90% breakthrough CO2 capacity showed volcano-shaped curves with respect to Mg/Al molar ratio, and they were decreased in the order of MgAl-AE-0.5>MgAl-AE-1.0>MgAl-AE-2.0>MgAl-AE-3.0>MgAl-AE-0. It was found that the 90% breakthrough CO2 capacity increased with increasing medium basicity of the adsorbents. Among the adsorbents tested, MgAl-AE-0.5 (Mg/Al=0.5) adsorbent with the highest medium basicity showed the best CO2 adsorptive performance. Thus, medium basicity of nano-structured MgO–Al2O3 aerogel adsorbents served as a crucial factor in determining CO2 adsorptive performance at elevated flue gas temperature (200°C).

Molybdenum oxide supported on nanostructured MgO: Influence of the alkaline support properties on MoOx structure and catalytic behavior in selective oxidation

Local structure and catalytic activity of molybdenum oxide supported on alkaline, nanostructured support materials were investigated. The structure of the surface oxide catalysts was significantly affected by the properties of the support. The support material was prepared via two different routes. A direct MgO synthesis approach was compared to SBA-15 coated with magnesium oxide. The structure of the support materials was investigated by XRD and N2 physisorption. Both materials exhibited a high specific surface area with a narrow pore size distribution. The MgO-coated SBA-15 (MgO/SBA-15) exhibited a similar alkaline character as pure nanostructured MgO (nano-MgO) but was more stable under catalytic conditions. The highly dispersed molybdenum species on the support was characterized by XRD, XAS and DR-UV–Vis spectroscopy. The catalytic activity for selective oxidation of propene was investigated by gas chromatography. A considerably different species was present on the alkaline support, compared to more acidic support materials like SBA-15. The structure of the supported molybdenum oxide consisted of predominantly isolated [MoO4] tetrahedra and was largely independent from Mo loadings. The supported catalysts with isolated [MoO4] tetrahedra exhibited only poor catalytic activity compared to the higher polymerized Mo species supported on silica SBA-15.