MgO Nanoflakes Research Articles

Effects of water adsorption on active site-dependent H2 activation over MgO nanoflakes

Effects of water adsorption on active site-dependent H2 activation over MgO nanoflakes

Development of photoactive MgO nanoflakes using the sol–gel method for the removal of organic contaminants

Development of photoactive MgO nanoflakes using the sol–gel method for the removal of organic contaminants

Boosting the selectivity of higher alcohols in upgrading of aqueous bioethanol over amphiphilic NiSn@C-MgO catalyst

Bio-ethanol produced from biomass has been regarded as a promising feedstock for producing higher alcohols (C4+ alcohols) through the Guerbet route. Nevertheless, the high-efficiency upgrading of bio-ethanol is driven by the current disadvantage of low selectivity to C6+ alcohols. Herein, we designed and synthesized an amphiphilic NiSn@C-MgO, which was composed of NiSn nanoparticles (NPs) coated with carbon shell and MgO nanoflakes support. Detailed experiments reveal that the amphiphilic NiSn@C-MgO catalyst can stabilize emulsions and facilitate the cross-coupling of ethanol and C4+ alcohols (generated by ethanol self-condensation) to generate C6+ alcohols in aqueous ethanol upgrading. Furthermore, the carbonization temperature has a great influence on the structure of NiSn@C-MgO, thus greatly affecting the catalyst performance. Consequently, the optimal NiSn@C-MgO-550 displays an excellent activity with ethanol conversion of 73.3 %, the selectivities of C6+ alcohols and C8+ alcohols in liquid products also reach up to 60.9 % and 32.5 %, respectively. This present strategy provides an efficient strategy for the direct upgrading of water-containing bio-ethanol to desired biofuel components, which may promote the fundamental researches on the production of biorefineries and green fuels.

Effects of Calcinations Temperatures on Structural, optical and magnetic properties of MgO nanoflakes and its photocatalytic applications

This study investigates the thermal, structural, optical and magnetic properties of MgO nanoflakes prepared by a precipitation method calcined at various temperatures ranging from 600 °C to 1000 °C. The structural properties of the samples studied by X-ray diffraction reveal cubic structure of MgO nanocrystals. Scanning electron microscopy study revealed flakes type morphology. Optical bandgap energy calculated from UV–Visible spectra varied from 5.59eV to 5.62eV, was found to be slightly increased with the increase of calcinations temperatures. Photoluminescence study indicates violet and blue emission arising due to oxygen and Mg vacancies and interstitials. The surface area obtained from BET analysis exhibited a higher surface area for sample calcined at 600 °C. Superparamagnetic behaviour is observed for the samples calcined below 800 °C where as a ferromagnetic response is exhibited at lower field for the samples calcined at higher temperatures. The photocatalytic activity was determined for the samples calcined at 600 °C, 800 °C and 1000 °C from which MgO-600 has shown the excellent photocatalytic potency of 98.1%. This study indicates that the structural, optical, magnetic properties and photocatalytic activity of MgO are significantly affected with the calcinations temperatures.

Preparation and Characterization of Magnesium Oxide Nanoparticles and Its Application for Photocatalytic Removal of Rhodamine B and Methylene Blue Dyes

In this research work, MgO nanoparticles were synthesized by a single‐step coprecipitation approach using Kappaphycus alvarezii extract as stabilizer. The synthesized MgO nanoparticles exhibit cubic crystal structure, which were confirmed by XRD and FTIR. The purity of MgO nanomaterials was confirmed by P‐XRD. The diffraction crests of MgO nanomaterials are in accordance with customary patterns of pure MgO (JCPDS No.00–004‐0821). Electron microscopic analysis demonstrated the appearance of MgO nanoflakes. The UV‐DRS was used to calculate the optical band gap of MgO nanoparticles and found to be 4.71 eV. MgO nanoparticles have substantial photocatalytic activity for the deterioration of rhodamine B (RhB) and methylene blue (MB) dyes under visible light irradiation. The experimental data fitted first‐order kinetics and around >95% degeneration of both dyes was achieved by photocatalysis using synthesized MgO nanoparticles. Thus, the data obtained from this research can effectively be utilized in large‐scale industrial applications during wastewater treatments.

Phosphate recovery from aqueous solution through adsorption by magnesium modified multi-walled carbon nanotubes

In this study, multi-walled carbon nanotubes modified by magnesium (Mg@CNT) was prepared as a novel adsorbent to recover phosphate from wastewater. Mg@CNT with the mass ratio of 0.48 (Mg versus MWCNTs) was the most efficient for phosphate adsorption and the maximum experimental adsorption capacity was up to 198 mg P/g. The Mg@CNT characterization was done by Field emission scanning electron microscope coupled with energy-dispersive spectroscopy detector (FESEM-EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), surface area analyzer (BET), Transmission electron microscope coupled with energy-dispersive spectroscopy detector (TEM-EDS). The MgO nanoflakes spread on the surface of multi-walled carbon nanotubes and reacted with phosphate to generate Mg3(PO4)2·10H2O as the end product. Phosphate adsorption on Mg@CNT was chemisorption onto heterogeneous surface according to the kinetic model and isotherm model fitting results. Several common co-existing ions, e.g., Cl−, NO3− and humic acid, had no obvious negative impact on the phosphate adsorption capacity; while SO42− and CO32− expressed stronger negative impacts and led to 13.2% and 39.5% decrease in phosphate adsorption capacity, respectively. After five adsorption-desorption cycles, Mg@CNT still maintained more than 80% adsorption capacity of the initial and high phosphate desorbability. These results implied that Mg@CNT possessed great application potential in phosphate recovery.

Electric field controlled near-infrared high-speed electro-optic switching modulator integrated with 2D MgO.

The electro-optic effect in two-dimensional (2D) MgO nanoflakes synthesized by a microwave-assisted process is demonstrated using a designed optical fiber modulator. The guiding properties of intense core modes excited by the material cavity are modulated by the external electric field. The feasibility of 2D MgO nanoflakes as an effective electro-optic modulator and switching are experimentally verified for the first time, to the best of our knowledge. The proposed optical-fiber-based electro-optic modulator achieves a linear wavelength shift with a high sensitivity of 12.87 pm/V(77.22 nm/kV/mm, in the electric field). The results show that MgO, as a metal oxide 2D material, is a very promising material for electro-optic modulators and switching.

Green Mediated Synthesis of MgO Nano-Flakes and Its Electro-Chemical Applications

MgO nano flakes were synthesized by a green mediated route using Vetiver (Chrysopogonzizanioides) grass as a fuel. The obtained products were characterized by powder X-ray diffraction (PXRD), diffuse reflectance spectroscopy (DRS) Scanning electron microscope (SEM), Travelling Electron Microscope (TEM) and Fourier transform infrared spectroscopy (FTIR). PXRD patterns show singlecubic phase MgO matched with JCPDS card No. 4-829 with the crystallite size was found to be ∼ 20-25 nm. SEM result reveals flakes and agglomerated nanoparticles. The optical energy gap was 4.50eV which demonstrates that there is a movement to the higher wavelengths of the absorption edge with reduction of the energy gap when using green fuel for synthesis.The electrochemical properties of MgO havebeen investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements using a modified carbon paste electrode. Further, modified carbon paste electrodeis also found to exhibit higher capacitance and lower charge transfer resistance. These findings suggest that the synthesized electrode possess better electrochemical properties and thus can be recognized as apromising candidate for the battery electrode applications

Effect of Morphology of MgO on the CO<sub>2</sub> Adsorption Capacity for Low Temperature Applications

MgO nanoparticles, nanoflakes and nanorods were synthesized by sol-gel or hydrothermal method. X-ray diffraction confirmed the formation of cubic MgO in entire samples after calcination. The round particles diameter was in the range of 200-500 nm while the flakes structure were with thickness 100-200 nm. The rods were in average diameter of 150-500 nm. CO2 adsorption capacity was measured by using TGA. MgO flakes with smaller crystallite size demonstrated high CO2 adsorption capacity of 1.738 mmol/g at low adsorption temperature of 50°C.

A novel synthesis method of hierarchical mesoporous MgO nanoflakes employing carbon nanoparticles as the hard templates for photocatalytic degradation

We describe a novel synthesis method for the preparation of bimodal mesoporous MgO nanoflakes and their application in photocatalytic activity for the degradation of methylene blue dye under UV light irradiation. For this purpose, Mg(OH)2/carbon nanocomposite was obtained through the precipitation of magnesium hydroxide in the presence of carbon nanoparticles. X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), and transition electron microscopy (TEM) micrographs have shown that this strategy could be successfully used to prepare bimodal mesoporous MgO nanoflakes with two different pore size distributions centered at 3 and 25nm and a high specific surface area of 216.9m2/g. Furthermore, the product was used as an adsorbent to remove methylene blue dye from aqueous media. The results confirmed that the photocatalytic activity of the synthesized mesoporous MgO was significantly improved due to the presence of such different pore sizes and high specific surface area resulting in higher adsorption, storage, and degradation of dye molecules.

Synthesis and Characterization of MgO Modified Diatomite for Phosphorus Recovery in Eutrophic Water

The highly dispersed MgO-nanoflake modified diatomite (MgO–D) was synthesized by a two-step process and used for the adsorption of phosphate from wastewater. The adsorbents involved were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and field-emission scanning electron microscopy (SEM). Different conditions such as solution pH, contact time, temperature, and coexisting anions were investigated. MgO–D exhibited an excellent phosphate adsorption capacity within the pH range of 3–10 and approached its maximum of 104.94 mg g–1 at optimal conditions. The adsorption kinetics followed the pseudo-second-order kinetic model. The adsorption isotherms had a good fit with the Langmuir model, while the maximum adsorption capacity reached 137.93 mg g–1 at 298 K. The thermodynamics parameters indicated that the sorption process was spontaneous and exothermic. A mechanism that involved (i) hydroxylation of MgO nanoflakes, (ii) electrostatic attraction of negatively charged phosphate ions with hy...

Ultrathin hexagonal MgO nanoflakes coated medical textiles and their enhanced antibacterial activity

A facile hydrothermal method for development of ultrathin MgO nanoplates from different precursors and their enhanced antibacterial activity after coating onto medical textiles is reported. Ultrathin MgO nanoplates having hexagonal structure were characterized using UV–visible spectroscopy, atomic force microscopy, field emission scanning electron microscopy, x-ray diffraction and high resolution transmission electron microscopy. The formation of MgO nanoplates was found to exhibit profound anionic effect leading to ultrathin, planar structures with exposed MgO [111] facets, which may be responsible for enhanced antimicrobial activity. Medical fabrics (bleached 100% cotton) were coated with MgO nanoplates using pad-dry-cure method. The antibacterial activity of these fabrics was tested against Bacillus subtilis and Escherichia coli. The MgO nanoplates coated onto the fabric were found to have good adherence properties owing to their two-dimensional structure and were durable even after repeated washings without substantial reduction in the antimicrobial activity. The enhanced antibacterial activity may be attributed to the presence of oxygen vacancies, surface oxygen anions and hydroxyl groups on the surface of MgO nanoplates. This cost-effective functional finish (anti-microbial) to cotton fabric using MgO nanoplates may be suitable for many prospective medical applications and can serve as an alternative to the costlier silver based antimicrobial textiles.

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.

Template-free synthesis of MgO nanoparticles for effective photocatalytic applications

MgO nanoparticles were synthesized by template-free reflux condensation approach. XRD and FTIR confirmed the formation of single phase MgO exhibiting cubic crystal structure. SEM and TEM analysis revealed the formation of MgO nanoflakes. The optical band gap of MgO nanoparticles estimated from UV DRS was in the range 5.40–5.45eV. PL spectra of MgO nanoparticles showed visible emissions due to the formation of defects in the band gap region of MgO. Synthesized MgO nanoparticles exhibited appreciable photocatalytic activity for the degradation of methyl orange and methylene blue dyes under UV light irradiation. Results demonstrated that the origin of photocatalytic activity in MgO arises due to the existence of high concentration of native defects on the surface of MgO.

Synthesis of porous MgO-biochar nanocomposites for removal of phosphate and nitrate from aqueous solutions

A new synthesis was developed to create highly porous nanocomposite material consisting of MgO nano-flakes within a biochar matrix that has high sorption ability for ionic contaminations. The synthesis method was used in laboratory to produce MgO-biochar nanocomposites from a variety of carbon-rich biomass. Physical and chemical properties of the synthesized nanocomposites were studied systematically with X-ray powder diffraction, thermogravimetric analysis, scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray analysis. In addition, batch sorption experiment was conducted to determine the sorption ability of the MgO-biochar nanocomposites to aqueous phosphate and nitrate. The results showed that the MgO nano-flakes have uniform morphologies and disperse uniformly on the surface of the biochar matrix. HR-TEM indicated that the biochar matrix is mesoporous with average pore size of 50nm and the MgO nano-flakes have spacing between 2 and 4nm, which can serve as adsorption sites for anions. As a result, all the tested MgO-biochar nanocomposites showed excellent removal efficiencies to phosphate and nitrate in water. Nanocomposites made from sugar beet tailings and peanut shells had the best performances with Langmuir adsorption capacities as high as 835mgg−1 for phosphate and 95mgg−1 for nitrate, respectively, much higher than the reported values of other adsorbents.

Investigation of the optical properties of Mg(OH)2 and MgO nanostructures obtained by microwave-assisted methods

Two simple methods for the synthesis of Mg(OH)2 nanostructures, MgO nanoflakes and MgO/Mg(OH)2 nanocomposite using a conventional microwave oven are reported. The first method includes the preparation of Mg(OH)2 by a simple reaction of magnesium powder with deionized water under microwave radiation. The second approach relates to the transformation of Mg(OH)2 to MgO nanoflakes and grass-like nanostructures by rapid microwave hybrid heating using a SiC-based composite susceptor. The as-synthesized samples have been characterized by X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) The optical properties of the samples are investigated using UV–visible spectroscopy to study the reflective index and optical dielectric constant.

Novel surfactant-free synthesis of MgO nanoflakes

A new and an environmentally benign route have been developed for the synthesis of MgO nanoflakes, which does not require any additives, surfactants and substrates. The technique is based on a very simple reaction of magnesium powder and water at temperature of 100 °C. The formation of MgO nanostructures by the reaction of metals with water is suggested to occur due to the decomposition of magnesium hydroxide at higher temperature and higher pressure. The MgO nanoflakes have an average width of 40 nm, thickness of 20 nm and length up to 1 μm. Compared with other methods, the present method is fast, economical, low temperature and free of pollution which will make it suitable for large scale production. Moreover, the technique does not require any sophisticated equipments and as such can be extended to the other metal oxides.

Preparation of Rhombic MgO Nanoflakes from Dolomites

Rhombic magnesia flakes with multi interspaces were prepared by calcining magnesium hydrate.The precursor of MgO could be obtained via acid immersing twice and ammonia depositing from dolomites.The structure,morphology,and composition of MgO and its precursor were characterized by means of XRD,FT-IR,SEM,and TEM methods.The results indicated that EDTA and PEG molecules were possessed of the effect directing the radial epitaxial growth of Mg(OH)2 flakes.The rhombic magnesia nanoflakes with 10-20 nm in thickness and up to 1 μm2 in area of main surface are single crystal with cubic crystal structure.It grows with a preferred orientation along the [100] direction and inherits the features of radial epitaxial growth of Mg(OH)2.The orientated growth mechanism of the MgO nanoflakes was studied based on corresponding thermodynamics and dynamics theories.