Energy Dispersive X-ray Mapping Analysis Research Articles

Surface modification of silica nanoparticles by chitosan for stabilization of water-in-oil Pickering emulsions

Water-in-oil (W/O) Pickering emulsions (PEs) as delivery systems have recently attracted important research efforts. The lack of food-grade hydrophobic particulate as emulsion stabilizers is the most important challenge in this field. This study investigates the surface modification of silica (SiO2) nanoparticles (SNPs) by chitosan and their role in formulation and stabilization of PEs; namely, the adsorption of chitosan on the surface of SNPs through electrostatic attraction with different chitosan/SiO2 ratio and pH values. The ability of SNPs to stabilize water in oil PEs regarding this modification was then investigated. The interaction between SNPs and chitosan was characterized by zeta potential, wettability, FTIR, Energy dispersive X-ray mapping analysis (EDX- MAP) and nitrogen absorption/desorption isotherm. The results confirmed that the surface modification of SNPs by chitosan had a significant impact on zeta potential and on the wettability of SNPs. Finally, modified SNPs were applied to the formulation of PEs; we identified the optimized conditions that increase the emulsion formulation process and stability. Therefore, modified SNPs by chitosan in this study could act as food-grade W/O Pickering stabilizers to fabricate environmental-friendly emulsion products.

Fabrication of sub-5 nm uniform zirconium oxide films on corrugated copper substrates by a scalable polymer brush assisted deposition method

We demonstrate a polymer brush assisted approach for the fabrication of continuous zirconium oxide (ZrO2) films over large areas with high uniformity (pin-hole free) on copper (Cu) substrates. This approach involves the use of a thiol-terminated polymethyl methacrylate brush (PMMA-SH) as the template layer for the selective infiltration of zirconium oxynitrate (ZrN2O7). The preparation of a highly uniform covalently grafted polymer monolayer on the Cu substrate is the critical factor in fabricating a metal oxide film of uniform thickness across the surface. Infiltration is reliant on the chemical interactions between the polymer functional group and the metal precursor. A following reductive H2 plasma treatment process results in ZrO2 film formation whilst the surface Cu2O passive oxide layer was reduced to a Cu/Cu2O interface. Fundamental analysis of the infiltration process and the resulting ZrO2 film was determined by XPS, and GA-FTIR. Results derived from these techniques confirm the inclusion of the ZrN2O7 into the polymer films. Cross-sectional transmission electron microscopy and energy dispersive X-ray mapping analysis corroborate the formation of ZrO2 layer at Cu substrate. We believe that this quick and facile methodology to prepare ZrO2 films is potentially scalable to other high-κ dielectric materials of high interest in microelectronic applications.

Membranes Based on Polyvinylidene Fluoride and Radiation-Grafted Sulfonated Polystyrene and Their Performance in Proton-Exchange Membrane Fuel Cells.

Proton-exchange membranes based on gamma-irradiated films of PVDF and radiation-grafted sulfonated polystyrene with an ion-exchange capacity of 1.8 meq/g and crosslinking degrees of 0 and 3% were synthesized. A solvent-free, environmentally friendly method of styrene grafting from its aqueous emulsion, with a styrene content of only 5 vol.% was used. Energy dispersive X-ray mapping analysis showed that the grafted sulfonated polystyrene is uniformly distributed throughout the membrane thickness. The obtained materials had a proton conductivity up to 132 mS/cm at 80 °C and a hydrogen permeability of up to 5.2 cm2/s at 30 °C, which significantly exceeded similar values for Nafion®-212 membranes. The resulting membranes exhibited a H2/O2 fuel cell peak power density of up to 0.4 W/cm2 at 65 °C. Accelerated stability tests showed that adding a crosslinking agent could significantly increase the stability of the membranes in the fuel cells. The thermal properties and crystallinity of the membranes were investigated through differential scanning calorimetry and X-ray powder diffraction methods. The conductivity, water uptake, and mechanical properties of the membranes (stress–strain curves) were also characterized.

Green synthesis of spinel copper ferrite (CuFe2O4) nanoparticles and their toxicity

Abstract In this study, magnetic spinel copper ferrite (CuFe2O4) nanostructures were eco-friendly synthesized using Nasturtium officinale extract. Physicochemical properties of these nanostructures were determined by transmission electron microscopy, field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), vibrating sample magnetometry, and energy dispersive X-ray mapping analysis. XRD patterns conform to the CuFe2O4 formation. SEM results demonstrated ceramic spinel CuFe2O4 nanostructures with spherical surface morphologies. The cytotoxicity effect of CuFe2O4 nanostructures against rat pheochromocytoma (PC12) cells was evaluated based on MTT assay. The magnetic nanostructures had low toxicity at a concentration of 250 µg/mL. It appears that these nanostructures can be considered as suitable candidates for drug delivery and other biomedical applications, because of their low toxicity effects.

Supercritical carbon dioxide assisted co-electrodeposition of nickel-titanium dioxide composite film and the dispersity

This work reports effects of supercritical carbon dioxide (SC-CO2) on the dispersion of TiO2 in Ni-TiO2 composite films prepared by SC-CO2 assisted co-electrodeposition. Pure Ni and Ni-TiO2 composite films prepared by the conventional electrodeposition method are prepared as comparisons. The average grain size of the Ni matrix is compared from the X-ray diffraction results, and grain refinement is observed in the composite film prepared by the SC-CO2 assisted co-electrodeposition. The incorporation amount of TiO2 and the dispersity in the composite film are determined from results obtained in energy dispersive X-ray mapping analysis, and the TiO2 content reaches 5.47 wt% and the dispersity of TiO2 becomes more uniform in the composite film by the SC-CO2 assisted co-electrodeposition. The dispersity is quantified through a convolution process. Vickers hardness of the composite film reaches 1167 Vickers Pyramid Number (HV0.1/15) because of the fine Ni grains, high TiO2 content and uniform TiO2 distribution.

A novel TMD/MOF (Transition Metal Dichalcogenide/Metalorganic frameworks) composite for highly and selective adsorption of methylene blue dye from aqueous mixture of MB and MO

The removal of organic dye effluents released from numerous dye-utilizing industries is of increasing concern. In this study, the efficiency of wastewater dye adsorption methods was studied by synthesizing and characterizing MoS2-COOH @ UiO-66-NH2 composite based on a novel type of transition metal dichalcogenide/metal-organic frameworks (TMD/MOF) prepared using basic materials such as MoS2, and UiO-66-NH2. The fabricated MoS2-COOH @ UiO-66-NH2 composite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermal stability (TGA), FT-IR spectroscopy, and Energy Dispersive X-ray mapping analysis. In addition, the surface charge of the nanocomposite was probed with Zeta potential (ζ) measurements using the Dynamic Light Scattering (DLS) technique. TMD/MOF composites, as adsorbents, were investigated under various experimental conditions and their equilibrium adsorption capacity towards MB was found to be up to 253mgg−1 (when pH = 7.0, contact time was 100 min, the adsorbent dose was 6 mg and initial MB concentration was 75 mgL − 1 (30 ml) Using the pseudo-first-order and pseudo-second-order models to study the kinetic behavior of the adsorption process, a better performance of the pseudo-second-order model in describing the kinetic behavior of the MB and MO adsorption process was observed. In addition, MoS2-COOH @ UiO-66-NH2 composites could selectively separate methylene blue from a mixture of MB (methylene blue) and MO (methyl orange) with a separation efficiency of 86%.

Lanthanum phosphate foam as novel heterogeneous nanocatalyst for biodiesel production from waste cooking oil

In this study, the potential of LaPO4 foam as a heterogeneous catalyst to produce biodiesel from highly acidic waste cooking oil (WCO) was investigated. The LaPO4 supported nickel foam was characterized by scanning electron microscopy (SEM), energy dispersive X-ray mapping analysis (EDX), X-ray diffraction, and Fourier transform infrared (FT-IR). In addition, the effect of different parameters such as the molar ratio of feedstock to methanol, contact time and the reaction temperature. Under the study conditions, with methanol to oil molar ratio of 5:1, and a reaction temperature of 90 °C, 91% FAME yield was obtained within 120 min with 2.5 wt % of LaPO4. The obtained results demonstrated that LaPO4 foam can be used effectively as a heterogeneous catalyst with superior catalytic efficiency (>90%) with easy separation and excellent stability.

Ultrasound-assisted efficient synthesis of a novel Nd–MOF polymer as a new candidate for electrocatalytic activity in hydrogen storage

For the first time, Nd-MOF nanostructures were synthesized using a novel ultrasonic procedure. The final products were characterized by relevant techniques of X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy, energy-dispersive X-ray mapping analysis, nuclear magnetic resonance, vibrating sample magnetometer, photoluminescence, and Brunauer–Emmett–Teller (BET) surface area analysis. Results showed that using ultrasonic irradiation can produce Nd-MOF samples with desirable physicochemical properties. It was found that the Nd-sample synthesized in optimum conditions has a high surface area of 1649 m2 g−1. This value expands the application of these novel materials in different fields such as electrochemical applications. The electrochemical cyclic voltammetry method was employed to study the behavior of DA on the proposed modified electrode. The results revealed high yields of these compounds in the electrooxidation of dopamine. The efficient synthesis route, novel physichochemical properties, and potential electrochemical applications developed in this study can be used as a novel protocol for other MOFs.

β-Cyclodextrin covalent organic framework–modified organic polymer monolith as a stationary phase for combined hydrophilic and hydrophobic aqueous capillary electrochromatographic separation of small molecules

Aβ-Cyclodextrin covalent organic framework (β-CD COF) was successfully prepared under ambienttemperature with a mild chemistry strategy from heptakis(6-amino-6-deoxy)-β-cyclodextrin and terephthalaldehyde. It was embedded into the poly[(glycidyl methacrylate)-co-(ethylene dimethacrylate)] [poly(GMA-co-EDMA)] monolith and served as the β-CD COF material-incorporated monolith. The synthetic materials were characterized by field emission scanning electron microscopy, energy-dispersive X-ray mapping analysis, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and N2 adsorption-desorption isotherm. The β-CD COF material-incorporated monolith achieved baseline separation in capillary electrochromatographic separationof three amides, three amino acids, three nucleosides, four aromatic acids, and three positional isomers (withresolutionvalues of three amides, 1.75 and 1.54; three amino acids, 5.24 and 1.75; three nucleosides, 2.56 and 1.77; four aromatic acids, 6.96, 2.74, and 1.64; three positional isomers, 1.61 and 1.50). In comparison with the original monolith, the β-CD COF material-incorporated monolith shows significantly enhanced resolution for mixed molecules. The effect ofpH and concentration of buffer and applied voltage were discussed in detail. The fabricated monolith showed good stability and reproducibility (relative standard deviation (RSD) < 6.9%). Molecular modeling illuminated the interactions between the small molecules and stationary phase, and provided a sufficient theoretical basis for experimental data. Graphical abstract Schematic presentation of the preparation of β-cyclodextrin covalent organic framework (β-CD COF) material-incorporated organic polymer monolith for separating the amides, amino acids, nucleosides, aromatic acids, and positional isomers. β-CD COF materials were synthesized and incorporated into the monolith as the stationary phase. Then, the incorporated monolith was applied in the capillary electrochromatography system for separating small molecules.

A novel ternary Pd-GO/N-doped TiO2 hierarchical visible-light sensitive photocatalyst for nanocomposite membrane

We investigated the visible-light sensitive photocatalytic ability of a designed ternary Pd-GO/TiON nano-composite for use as an effective photocatalyst in membranes. We succeeded in synthesizing the TiO2-based photocata-lyst for Suzuki coupling reaction and application of this photocatalyst for fabricating high performance photocatalytic membrane. In this regard, palladium metal as a complementary metal in combination with N-doped TiO2 (TiON) and graphene oxide (GO) nanosheets was utilized to synthesize the upgraded version of the visible light sensitive nanocom-posite photocatalyst. The synthesis of Pd-GO/TiON hierarchical nanostructure was confirmed by detecting Ti, Pd, C, O and N elements by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX) and EDX mapping analysis. Then, a series of PVDF-based photocatalytic nanocomposite membranes (PhNMs) filled with Pd-GO/TiON was fabricated. Evaluating the yield of Pd-GO/TiON photocatalyst was around 99% and 70% for heterogeneous system and the prepared PhNM containing 3% Pd-GO/TiON, respectively. Although, yield of Pd-GO/TiON photocatalyst in membrane is not comparable with the high yield reported by other researchers in heterogeneous system; however, it can be considered as a valuable result because of the importance of photocatalytic reactions and the environmental advantages of membrane technology. Furthermore, various analyses were also performed to study the synthesized photocata-lysts and the prepared photocatalytic membranes, including thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and diffuse reflectance spectrophotometry (DRS).

Green Synthesis of CuFe2O4@Ag Nanocomposite Using the Chlorella vulgaris and Evaluation of its Effect on the Expression of norA Efflux Pump Gene Among Staphylococcus aureus Strains

Increasing drug resistance among Staphylococcus aureus is a global health threat and finding alternative antimicrobial agents against it has been considered. Multidrug resistance efflux pumps, including NorA, are involved with resistance to different drugs, especially fluoroquinolones, in S. aureus. Using metal nanoparticles against pathogenic bacteria is a promising approach; however, physio-chemical synthesis of nanoparticles has limitations. Biosynthesis of metal nanoparticles with antibacterial activity has gained interest, recently. In this study, biosynthesis of CuFe2O4@Ag nanocomposite using aqueous extract from microalgae Chlorella vulgaris was performed, and its antibacterial property and effect on expression of norA efflux pump gene were investigated. Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), energy dispersive X-ray mapping analysis (EDX-map), differential reflectance spectroscopy (DRS), and dynamic light scattering (DLS) were used to characterize synthesized nanocomposite. Antibacterial activity of the prepared nanocomposite individually and combined with ciprofloxacin against S. aureus strains was evaluated using the disk assay method, and minimum inhibitory concentration (MIC) of each agent was determined using the broth dilution method. Anti-biofilm activity of this nanocomposite was checked. Finally, the effect of CuFe2O4@Ag nanocomposite alone and in combination with ciprofloxacin on the expression of norA was assessed by real-time PCR. The physical analysis revealed proper synthesis of spherical and well-dispersed CuFe2O4@Ag nanocomposite with an average diameter of 20nm. Synthesized nanocomposite had synergistic antibacterial activity with ciprofloxacin. Moreover, expression of norA gene among clinical and standard strains treated with CuFe2O4@Ag nanocomposite combined with ciprofloxacin reduced by 59% and 65%, respectively. Thus, CuFe2O4@Ag nanocomposite synthesized in this study can be considered as a promising candidate to be used to inhibit staphylococcal efflux pump genes and increasing the antibiotic efficacy.

Surface modification of poly (L-lactic acid) films to improve electrical conductivity by surface entrapment/in situ polymerization methods

Electrical properties play an important role in the interaction of cells and biomaterials. The aim of this study was to increase surface electrical conductivity of poly (L-lactic acid) (PLLA) films by polyaniline (PANI) using surface entrapment (SE) and surface entrapment in situ polymerization (SEIP) methods. The entrapment modification technique was performed by the reversible gelation of the PLLA surface region following exposure to a solvent and non-solvent mixture, while PANI chains were diffused into the swollen PLLA surface. In SEIP method, PANI was entrapped through in situ chemical oxidative polymerization of aniline on PLLA films. The effects of PANI concentration, the ratios of solvents and immersion time on the electrical conductivity were studied by SE method. The effects of aniline concentration, doping effect, temperature and time of polymerization were evaluated by SEIP method too. The results obtained by attenuated total reflection Fourier transformer infrared spectroscopy, scanning electron microscopy and energy dispersive x-ray mapping analysis confirmed the presence of PANI on the surface of PLLA films. UV-visible analysis was employed to investigate the doping effect on the reduction of energy and conductivity of the films. Experimental results also indicated that the electrical conductivity, uniformity and density of the SEIP modified films were significant in comparison to those of the modified films by SE method.

Rational design of thermoresponsive functionalized MCM-41 and their decoration with bimetallic Ag–Pd nanoparticles for catalytic application

Abstract MCM-41 was functionalized with thermoresponsive poly (N-isopropyl acrylamide) (p-NIPAM) by free radical polymerization. The surface of the p-NIPAM-coated on MCM-41 (MCM-41/p-NIPAM) nanocatalyst was decorated with bimetallic Ag–Pd nanoparticles for catalytic applications. The nanocatalyst was characterized by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, nitrogen adsorption/desorption analysis, thermograviametric analysis (TGA), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM) with energy dispersive X-ray (EDX) spectroscopy, x-ray photoelectron spectroscopy (XPS), and dynamic light scattering (DLS). The thermoresponsive behavior of the synthesized nanocatalyst was analyzed by UV–vis spectroscopy (UV–vis) and DLS analysis. The distribution of bimetallic nanoparticles and their compositions on the polymer-coated mesoporous silica surface were investigated by EDX mapping analysis. The specific surface area was characterized by nitrogen adsorption/desorption analysis. The nanocatalyst was tested for the catalytic reduction of benzaldehyde by UV–vis analysis. Interestingly, the bimetallic nanoparticle-supported MCM-41/p-NIPAM nanocatalyst showed higher activity compared to the other counterparts. In addition, the nanocatalyst showed thermoresponsive behavior at different temperatures and could be recycled for consecutive five cycles with minimal loss in activity. This study is expected to open promising probability for the use of the above material for a range of catalytic applications.

Synthesis of Polymeric Nanocomposite Hydrogels Containing the Pendant ZnS Nanoparticles: Approach to Higher Refractive Index Optical Polymeric Nanocomposites

Nanocomposites have attracted more attention due to their extensive applications. However, it is still a huge technological challenge in fabrication of transparent hybrid materials because of nanoparticle aggregation resulting from their high specific surface energies. In this paper polymerizable molecule was controlled chemically grafted onto ZnS nanoparticles to obtain polymerizable-group-capped nanoparticles that can copolymerize with a mixture of acrylic monomers of N,N-dimethylacrylamide (DMA) and 2-hydroxyethyl methacrylate (HEMA) or glycidyl methacrylate (GMA) or methyl methacrylate (MMA) to prepare transparent high refractive index (RI) nanocomposite hydrogels. The dispersion homogeneity of the nanoparticles in the nanocomposites was studied by dynamic mechanical thermal analysis (DTMA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray mapping analysis (EDX). Moreover, the nanocomposites were characterized by transmittance, mechanical properties, and refractive index (RI). The results showed that grafted amount of polymerizable group on the nanoparticle surface influences the cross-link density and microphase structure of the resultant nanocomposites, leading to different transmittance and mechanical properties. The RI of hydrated and dry nanocomposites can be regulated to a peak value of 1.652 and 1.751, respectively, by a simple adjustment of ZnS content in the nanocomposites. Our approach was also proved to be effective in preparing DMA-free transparent nanocomposites with high RI of 1.824 by copolymerizing between polymerizable-group-capped ZnS and single monomer of HEMA or GMA or MMA.

An electrochemical sensing platform of cobalt oxide@gold nanocubes interleaved reduced graphene oxide for the selective determination of hydrazine

Reduced graphene oxide-cobalt oxide nanocube@gold (rGO-Co3O4@Au) nanocomposite was prepared using a one-pot hydrothermal synthesis. The nanocomposite was characterized using the UV-Vis absorption spectroscopy, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) mapping, X-ray diffraction (XRD) and Raman analyses. The EDX mapping analysis showed the uniform distribution of Au nanoparticles on the Co3O4 surface that made the surface more roughness. The higher degree of reduction of GO was confirmed from the increased intensity ratio of the D and G bands (ID/IG) of the Raman spectrum during the hydrothermal synthesis. The rGO-Co3O4@Au nanocomposite exhibited good electrocatalytic activity towards the oxidation of hydrazine in phosphate buffer (pH 7.2). The detection of hydrazine was carried out using amperometry technique and the current response was linear in the range of 10–620 μM. The limit of detection was found to be 0.443 μM. The selectivity of the nanocomposite for the sensing of hydrazine was studied with the interferents such as NO3−, SO42−, Cl−, Ag+, Na+, K+, ethanol, 4-nitrophenol, ascorbic acid and glucose. The sensing of different concentration of hydrazine present in the real water samples was analysed and an appreciable recovery was found.

Sol–gel growth and characterization of a new p-NiO/n-GaAs structure

A new p-NiO/n-GaAs heterostructure was fabricated by a simple and cheap sol–gel route. X-ray diffraction, atomic force microscope and UV/VIS studies indicated that nano-sized NiO film had polycrystalline cubic bunsenite crystal structure with optical band gap of 3.75 eV. The energy dispersive x-ray mapping analysis proved the homogenous distribution of nickel and oxygen elements on GaAs surface. The electrical characterization of p-NiO/n-GaAs structure showed a rectifying behavior with rectification ratio 3.3 × 104 at +2.0 V in the dark for p-NiO/n-GaAs structure. The ideality factor and barrier height were calculated as 2.21 and 0.76 eV. The results suggest that p-NiO/n-GaAs structure can be used in many electronic applications.

Ultraviolet photosensors fabricated with Ag nanowires coated with ZnO nanoparticles

We have developed a simple low temperature process to coat zinc oxide (ZnO) nanoparticles (NPs) on Ag nanowires (NWs) with well-controlled morphology. Triethanolamine (TEA) was employed to react with zinc acetate (Zn(CH3COO)2) forming ZnO NPs. TEA was also found to enhance the nucleation and binding of ZnO NPs on the Ag nanowire surfaces facilitating a complete coverage of Ag nanowire surfaces with ZnO NPs. The effects of the process parameters including reaction time and reaction temperature were studied. The surfaces of 60nm diameter Ag NWs could be completely covered with ZnO NPs with the final diameters of Ag-NWs@ZnO (core–shell NWs) turning into the range from 100nm to 450nm. The Ag-NWs@ZnO was characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray mapping analysis, X-ray diffraction, and photoluminescence spectra. Finally, ultraviolet (UV) photosensors were fabricated using Ag-NWs@ZnO. They were found to improve photosensitivity with greatly enhanced fast response by reducing the recovery time by 2 orders, in comparison with the UV-sensors using single-crystalline ZnO NWs.

Template Synthesis of 3D High-Temperature Silicon-Oxycarbide and Silicon-Carbide Ceramic Photonic Crystals from Interference Lithographically Patterned Organosilicates

The fabrication of 3D diamond-like silicon-oxycarbide and silicon-carbide high-temperature ceramic photonic crystals has been achieved by a strategy involving (1) the use of four-beam interference lithography (IL) to construct a patterned silsesquioxane (POSS) template and (2) infiltration of the polymeric allylhydridopolycarbosilane (AHPCS) silicon-carbide precursor into the patterned POSS template followed by high temperature ceramic conversion and HF etching. Energy-dispersive X-ray mapping analysis and Fourier transform infrared (FT-IR) studies suggested that the 3D ceramic photonic crystals formed at 1100 °C were SiC-like silicon oxycarbide. Additional thermal treatment at 1300 °C in vacuo resulted in the carbothermic reduction of the 3D silicon-oxycarbide to form 3D β-SiC with less than 10% shrinkage in the (111) plane and [111] direction, respectively. The reflectivities of the inverse 3D ceramic photonic crystals obtained at different stages were characterized by FT-IR in the [111] direction. Both the inverse 3D silicon-oxycarbide and silicon-carbide crystals showed bandgaps at 1.84 μm. These experimental values matched well with the calculated bandgaps, further supporting the robustness of such fabricated 3D ceramic photonic crystals.