Field Emission Scanning Electron Microscopy Images Research Articles

Enzyme activity inhibition properties of new cellulose nanocrystals from Citrus medica L. pericarp: A perspective of cholesterol lowering.

As a waste material, the amazing potential of cellulose nanocrystals (CNCs) isolated from Citrus medica L. pericarp in being a natural resource of lingo-cellulosic products has never been investigated before. In the present study, an alkaline pretreatment and a two-step bleaching procedure were applied to conduct the desired acid hydrolysis by the usage of 64% sulfuric acid at 50°C for 105 min. The extracted CNCs were distinguished through the means of transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic force microscopy (AFM), Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), zeta potential, and energy-dispersive X-ray spectroscopy (EDX). The elimination of peaks, which were accountable for the inducement of hemicelluloses and lignin, was confirmed by the FTIR results and were also validated by the outcomes of XRD that proved the gentle removal of non-cellulosic components. The morphology and size of CNCs were indicated through the FESEM and TEM results. In addition, the spherical forms of synthesized CNCs were observed with a diameter of 46 nm throughout the FESEM images, while displaying a value of 42.54nm as well due to TEM micrographs. The obtained zeta potential displayed a reasonable negative surface charge for CNCs. Furthermore, the cytotoxicity assessment of this product on fibroblast cells was performed to study their susceptibility for bio-medical and cosmetic industrial applications, which resulted in the lack of exhibiting any cytotoxic effects. In conformity to the outcomes of TEM and FESEM, the results of AFM revealed a fine dispersion and spherical form of cellulose nanoparticles. The interaction between HMG-CoA reductase and CNC was studied by the usage of multi-spectroscopic methods and enzyme kinetics to explore the binding mechanism of HMG-CoA reductase-CNC system. Reduced catalytic activity of the occurrence of changes in the secondary structure of HMG-CoA reductase was as a result of interacting with CNC causing a reduction in its catalytic activity.

Defect mediated structural, optical, electrical and mechanical properties of mechano-synthesized PbTe nanostructure as a superior thermoelectric material: Correlation among electrical, mechanical and optical properties

This work reports on the formation of anti-site defects in mechanically alloyed PbTe samples and their anomalous effects on the optical and electrical properties of the sample. PbTe nanoparticles have been synthesised by mechanical alloying of the elemental Pb and Te powders mixed in stoichiometric ratio under an inert (Ar) atmosphere for different time durations. The structural and microstructural characterisations have been carried out by analysing X-ray diffraction (XRD) patterns, field-emission scanning electron microscope (FESEM), and high-resolution transmission electron microscope (HRTEM) images. The elemental composition has been revealed from the energy-dispersive X-Ray (EDX) spectrum. The phase pure cubic PbTe is formed within just 30 min of milling. The Rietveld analysis of XRD patterns, FESEM, and HRTEM images revealed the crystallite size reduction and the increase in r.m.s. lattice strain with the increase in milling durations. Inclusions of more and more anti-site defects of type [PbTe] with increasing milling time are reflected in the expansion of the cubic lattice parameter with milling durations. Fourier-transform infrared (FTIR) spectrum reveals that PbTe is a narrow bandgap semiconductor, and the bandgap shows a redshift with increased milling time and reduced crystallite size. This anomalous behaviour of the optical bandgap with reduced particle size is well explained by Urbach tailing due to increased defects in the more extended milled sample. The positions of the conduction and valence bands in the milled PbTe samples are determined for different milling times. The DC conductivity study also shows anomalous behaviour; electrical conductivity increases with particle size reduction in more extended milling time samples. It is resolved by considering that the carrier concentration increases with a longer milling time due to induced anti-site defects while milling. It results in bandgap reduction with milling durations and shows the predominant effect of electronic conductivity over ionic conductivity. The conduction mechanism is explained as per the Pertritz model, and the dependence of activation energies on particle size and temperature has been explained in detail. The Vickers hardness of the milled samples is determined, and its variation with grain size is explained with the Hall-Petch relation. The improved electrical conductivity with increased milling is also manifested in the measured hardness values.

MnO2 integrated emeraldine polyaniline (PANI- MnO2) nanocomposites with inflated opto-electricaltraitsas ETLs for OLED applications

Herein, we report a preparation method of a new hybrid nanocomposite based on polyaniline nanofibers and manganese dioxidenanorods (PANI-MnO2) via in-situ chemical oxidative polymerization of aniline with the addition of varying MnO2 content by using ammonium peroxydisulphide (APS) as an oxidant. The synthesized PANI-MnO2 nanocomposites were characterized using X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM), which confirmed their formation. FESEM images revealed that PANI nanofibers coated the MnO2 nanorods. Fourier Transform Infrared Spectroscopy (FTIR) was employed to investigate the interaction between PANI and MnO2 nanoparticles. Optical properties of PANI-MnO2 nanocomposites were examined by UV–Vis. Spectroscopy and the reduced band gap was observed about 1.76 eV for the optimized PMN2 nanocomposite. Blue, violet and green bands were observed in the photoluminescence spectrum for PANI-MnO2 nanocomposites. The color purity of 39% was obtained from CIE software in the light blue region. The conductivity of PMN2 was enhanced by 21% from pristine PANI. Also,the dielectric constant increases with temperature due to better implantation of dipoles of the conjugated polymer PANI in the direction of the electric field These resultsinferred that optimized PMN2 appeared to be a potential candidate as an effective electron transport layer for efficient OLED devices for lighting and display purposes.

Role of nickel in structural and mechanical properties of nc-WNNi sputtered nanocomposite coatings

Nanocomposites coatings offers a wide range of possibilities to promote hardness, oxidation resistance, wear resistance, etc properties significant for protective coatings. Finding new nanostructured coating with high hardness and thermal stabilities are the prime requirement of modern industries. In view of above, the nc-WNNi nanocomposite coatings were deposited using reactively sputtered method on silicon (100) substrate by varying the power of Nickel (Ni). The coatings were characterized by using grazing incidence X-ray diffraction (GIXRD), Field emission scanning electron microscope (FESEM), energy dispersive x-ray analysis (EDX), thickness profiler, four probe resistivity measurement and nanoindentation tester. Through GIXRD studies the desired face centered cubic W2N phase was confirmed, with decreasing crystallite size on increasing Ni power (content). FESEM image revels/suggest that at low Ni content, the film structure stabilized into well separated grains with the presence of grain boundary and were of uneven shape throughout. On increasing Ni power, the agglomeration increase and no clear signature of grain boundaries were visible. The resistivity of the films was found to be decreasing with increasing Ni content at different temperatures. Improved mechanical properties were observed at low Ni power (content), which drastically decreases with increasing Ni power. The highest hardness (H), elastic modulus (Er), elastic recovery (We), and resistance to plastic deformation (H3/E2) were obtained 26.60 GPa, 276.82 GPa, 69.80 GPa, 245 MPa respectively for nc-WN10Ni film. The nc-WN10Ni film shows the highest mechanical properties as compared to others.

Exploring the superhydrophilicity of nanosecond laser textured silicon: a Raman analysis.

We present Raman analysis of nanosecond laser textured silicon. The samples have also been characterized by field emission scanning electron microscopy (FESEM) and x ray diffraction. Contact angles (CAs) are measured to trace the hydrophilic nature. Characterization of the textured samples in argon and air shows that cleavage cracks are developed during texturing. CA measurements reveal the superhydrophilic nature of textured samples obtained in the presence of ambient oxygen and argon. In vacuum, however, the hydrophilicity is decreased. Micro-Raman analysis indicates the formation of nano-sized cleavage cracks that impart stable superhydrophilic properties to textured silicon is supported from FESEM images also. On the other hand, in vacuum textured silicon, evidence of such cracks is not noticed, which is also supported by Raman analysis. Further, the hydrophilicity is decreased. A definitive trend appears to exist between Raman signatures and hydrophilicity. We believe that the study will further the understanding of the mechanistic aspect in designing textured silicon with a high degree of self-cleaning capability.

Fabrication of 3D Gelatin Hydrogel Nanocomposite Impregnated Co-Doped SnO2 Nanomaterial for the Catalytic Reduction of Environmental Pollutants.

In the catalytic reduction of various environment pollutants, cobalt-doped tin oxide, i.e., Co-SnO2 intercalated gelatin (GL) hydrogel nanocomposite was prepared via direct mixing of Co-SnO2 doped with GL. Then, it was crosslinked internally using formaldehyde within a viscous solution of gelatin polymer, which led to the formation of GL/Co-SnO2 hydrogel nanocomposite. GL/Co-SnO2 hydrogel nanocomposite was fully characterized by using field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (XRD), and attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR). The FESEM images indicate that the Co-SnO2 composite has a spherical structure on the GL matrix while EDX elucidates the elemental composition of each atom in the crosslinked GL/Co-SnO2 hydrogel nanocomposite. The GL/Co-SnO2 nanocomposite was checked for the reduction of various pollutants, including 2-nitro-phenol (2-NP), 2,6-dinitro-phenol (2,6-DNP), 4-nitro-phenol (4-NP), Congo red (CR), and methyl orange (MO) dyes with a strong sodium borohydride (NaBH4) reducing agent. The GL/Co-SnO2 nanocomposite synergistically reduced the MO in the presence of the reducing agent with greater reduction rate of 1.036 min−1 compared to other dyes. The reduction condition was optimized by changing various parameters, such as the catalyst amount, dye concentration, and the NaBH4 amount. Moreover, the GL/Co-SnO2 nanocomposite catalyst can be easily recovered, is recyclable, and revealed minimal loss of nanomaterials.

Photocatalytic Dye Degradation and Bio-Insights of Honey-Produced α-Fe2O3 Nanoparticles

Iron oxide nanoparticles are produced using simple auto combustion methods with honey as a metal-stabilizing and -reducing agent. Herein, α-Fe2O3 nanoparticles are produced using an iron nitrate precursor. These prepared samples are analyzed by an X-ray diffractometer (XRD), FTIR spectroscopy, UV-DRS, and a field-emission scanning electron microscope (FESEM) combined with energy-dispersive spectroscopy and a vibrating sample magnetometer (VSM). The XRD results confirm a rhombohedral structure with an R3c¯ space group single-phase formation of α-Fe2O3 in all samples. FESEM images reveal the different morphologies for the entire three samples. TEM analysis exhibits spherical shapes and their distribution on the surfaces. XPS spectroscopy confirms the Fe-2p and O-1s state and their valency. The VSM study shows strong ferromagnetic behavior. The prepared α-Fe2O3 nanoparticles exhibit exceptional charge carriers and radical production. The prepared sample retains excellent photocatalytic, antifungal and antibacterial activity.

Antimicrobial and Mechanical Properties of Orthodontic Acrylic Resin Containing Zinc Oxide and Titanium Dioxide Nanoparticles Supported on 4A Zeolite.

Polymethyl methacrylate (PMMA) is widely used to manufacture removable orthodontic appliances. However, since the porous structure, cold-curing acrylic resins are susceptible to bacterial adhesion and colonization. The aim of this study was to investigate the antibacterial and mechanical properties of a cold-curing PMMA resin containing ZnO and TiO2 nanoparticles supported on the 4A zeolite. ZnO and TiO2 nanoparticles supported on the 4A zeolite were synthesized. Nanoparticles were added in three compositions as ZnO/4A, TiO2/4A, and ZnO/TiO2/4A at 2wt% and 4wt% concentrations to cold-curing acrylic resin powder (SR Triplex® Cold Ivoclar Vivadent AG, FL-9494 Schaan/Liechtenstein). X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), and dynamic light scattering (DLS) were performed to investigate the nanocomposite characteristics. A direct test method was used to assess the antibacterial properties against Streptococcus mutans, Klebsiella pneumoniae, and Escherichia coli. The surface roughness of acrylic samples was measured with a profilometer. Flexural strength was evaluated by a three-point bending test, and one-way ANOVA and Tukey's post hoc tests were used for statistical evaluation of the data. A p value of less than 0.05 was considered statistically significant. XRD confirmed the accurate crystalline structure of synthesized nanoparticles; FE-SEM images showed nanoparticle dispersion within polymerized acryl. The addition of 2 and 4 wt% of ZnO/4A, TiO2/4A, and ZnO/TiO2/4A caused colony reduction in all types of tested microorganisms more than 99% and 100%, respectively. The mean flexural strengths of acrylic specimens containing 2wt% and 4wt% of synthesized nanoparticles were significantly lower than those of the resin without nanoparticles. Fabricated samples showed favorable antibacterial properties but decreased flexural strength.

Examination of Structural and Electrical Properties of CuO‐Doped CdO Nanocomposites Produced by the Hydrothermal Method

AbstractIn this study, pure CdO and CdO‐CuO nanopowders with different dopant concentrations are synthesized by the hydrothermal method. Structural properties of the nanopowders are characterized by X‐ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR), morphological properties and elemental analyses are characterized by Field Emission Scanning Electron Microscopy (FESEM), optical properties are characterized by UV–vis spectroscopy, and electrical properties are characterized by the current–voltage technique. XRD data show that nanopowders are polycrystalline and crystallinity decreases with the doping concentration. In the analysis of FESEM images, it can be concluded that the morphology of the particles is shaped as needle‐like, spherical‐like, and randomly oriented nanorods forms from the cube form. Also, by joining those nanorods, spherical‐like microstructures occur, and while the dopant concentration increases, echinus‐like forms are obtained. The energy bandgap of the nanopowders decreases with an increased dopant concentration of CuO. It is observed that the dopant concentration of CuO also changes the electrical properties.

Synthesis and characterization of a g-C3N4/TiO2-ZnO nanostructure for photocatalytic degradation of methylene blue

In this study, graphitic carbon nitride (g-C3N4) nanostructures with different molar ratios of ZnO and TiO2 (i.e. g-C3N4/TiO2, g-C3N4/ZnO, and g-C3N4/TiO2-ZnO) were synthesized. The synthesized samples were characterized using field-emission scanning electron microscopy (FE-SEM), x-ray diffraction, Brunauer–Emmett–Teller (BET) analysis, and ultraviolet (UV)–visible diffuse reflectance spectroscopy (UV-vis-DRS) techniques. The FE-SEM images showed the surface morphology of each sample. The UV-vis-DRS results indicated that the bandgap of TiO2 was reduced by adding g-C3N4 and different molar ratios of ZnO. The results obtained from BET analysis confirmed that the surface area of the g-C3N4/TiO2-ZnO (1:10) nanostructure was 97.494 cm2 g−1, which was comparatively higher than other nanostructures, and became suitable for photocatalytic activity. The photocatalytic activity of the g-C3N4/TiO2-ZnO nanostructure was performed by photo-degradation of methylene blue (MB) dye under simulated solar light. The results of the photocatalytic activity showed that the synthesized nanostructure had good degradation under UV and visible light irradiation by 94.6% and 62.4%, respectively. Also, the kinetics of the photocatalytic degradation confirmed that degradation of MB dye in the presence of UV light was faster than visible light. Furthermore, a study of the reusability of the nanostructure exhibited good photo-stability and activity after six runs.

Preparation and Characterization of Novel Microgels Containing Nano-SiO2 and Copolymeric Hydrogel Based on Poly (Acrylamide) and Poly (Acrylic Acid): Morphological, Structural and Swelling Studies.

In this paper, novel microgels containing nano-SiO2 were prepared by in situ copolymerization using nano-SiO2 particles as a reinforcing agent, nanosilica functional monomer (silane-modified nano-SiO2) as a structure and morphology director, acrylamide (AAm) as a monomer, acrylic acid (AAc) as a comonomer, potassium persulfate (KPS) as a polymerization initiator, and N,N′-methylene bis (acrylamide) (MBA) as a crosslinker. In addition, a conventional copolymeric hydrogel based on poly (acrylamide/acrylic acid) was synthesized by solution polymerization. The microgel samples, hydrogel and nanoparticles were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A FESEM micrograph of copolymeric hydrogel showed the high porosity and 3D interconnected microstructure. Furthermore, FESEM results demonstrated that when nano-SiO2 particles were used in the AAm/AAc copolymerization process, the microstructure and morphology of product changed from porous hydrogel to a nanocomposite microgel with cauliflower-like morphology. According to FESEM images, the copolymerization of AAm and AAc monomers with a nanosilica functional monomer or polymerizable nanosilica particle as a seed led to a microgel with core–shell structure and morphology. These results demonstrated that the polymerizable vinyl group on nano-SiO2 particles have controlled the copolymerization and the product morphology. FTIR analysis showed that the copolymeric chains of polyacrylamide (PAAm) and poly (acrylic acid) (PAAc) were chemically bonded to the surfaces of the nano-SiO2 particles and silane-modified nano-SiO2. The particulate character of microgel samples and the existence of long distance among aggregations of particles led to rapid swelling and increasing of porosity and therefore increasing of degree of swelling.

Sintering parameters influence on dielectric properties of modified nano-BaTiO3 ceramics

BaTiO3 (BTO) is considered the most commonly used ceramic material in multilayer ceramic capacitors due to its desirable dielectric properties. Considering that the miniaturization of electronic devices represents an expanding field of research, modification of BTO has been performed to increase dielectric constant and DC bias characteristic/sensitivity. This research presents the effect of N2 and air atmospheres on morphological and dielectric properties of BTO nanoparticles modified with organometallic salt at sintering temperatures of [Formula: see text]C, [Formula: see text]C, [Formula: see text]C, and [Formula: see text]C. Measured dielectric constants were up to 35,000, with achieved very high values in both atmospheres. Field emission scanning electron microscopy (FESEM) was used for morphological characterization, revealing a porous structure in all the samples. The software image analysis of FESEM images showed a connection between particle and pore size distribution, as well as porosity. Based on the data from the image analysis, the prediction of dielectric properties in relation to morphology indicated that yttrium-based organometallic salt reduced oxygen vacancy generation in N2 atmosphere. DC bias sensitivity measurements showed that samples with higher dielectric constant had more pronounced sensitivity to voltage change, but most of the samples were stable up to 100 V, making our modified BTO a promising candidate for capacitors.

Design of Cube-like MnO2/r-GO Nanocomposite as a Superior Electrode Material for an Asymmetric Supercapacitor

A pure MnO2 cube and MnO2 cube/r-GO nanocomposite were synthesized by the simple hydrothermal method. The structural formation, morphological and chemical composition of as-prepared MnO2 cube/r-GO nanocomposite were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The FE-SEM and TEM images were revealed that the MnO2 cubes are homogeneously distributed on the surface of r-GO nanosheets. The electrochemical results showed that the high specific capacitance of MnO2 cube/r-GO nanocomposite was 1570 F g−1 at a current density of 2 A g−1 in 1 M Na2SO4 electrolyte solution. The long life-term cycling performance of MnO2 cube/r-GO nanocomposite were delivered at outstanding capacitance retention of 99.3% subsequently 10,000 charge-discharge cycles at 8 A g−1. Moreover, we construct the asymmetric supercapacitor (ASC) of MnO2/r-GO//r-GO for practical application. Herein, MnO2/r-GO act as an anode material and r-GO as a cathode material. The assembled device shows a high specific capacitance of 92.49 F g−1 at 1 A g−1, high power density of 1.5860 W kg−1, and a high energy density of 17.7555 Wh kg−1 at 8 A g−1. Furthermore, the ASC device exhibits excellent capacitance retention of 98% after 10000 sequential charge-discharge cycles in 1 M Na2SO4 electrolyte solution. Based on the electrochemical performance as-prepared MnO2 cube/r-GO nanocomposite considered as the potential electrode material for energy storage application.

Antibacterial study of ZnO and Zn0.5Mg0.5O nanoparticles synthesized by co-precipitation method

In the present study, zinc oxide (ZnO) and magnesium doped zinc oxide (Zn0.5Mg0.5O) nanoparticles were synthesized by simple and cost-effective co-precipitation method. The synthesized materials were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) with Energy dispersive X-ray spectrum (EDAX). Finally, the effect of magnesium (Mg) doping on the structural, morphological and anti-bacterial property of ZnO nanoparticles was analyzed. From the XRD results, it was found that there was a formation of hexagonal structured ZnO and the average crystallite size of ZnO and Zn0.5Mg0.5O was calculated to be 71 nm and 36 nm respectively. The FTIR analysis confirmed the existence of possible functional groups in ZnO and Zn0.5Mg0.5O. There was formation of almost spherical shaped particles as evident from FESEM images and agglomeration of particles was observed upon doping Mg into ZnO. The EDAX spectra of the prepared nanoparticles provided the composition of Zn, O in ZnO and Zn, Mg, O in Zn0.5Mg0.5O. No other elements have been found in the EDAX spectra of ZnO and Zn0.5Mg0.5O that confirmed the formation of pure materials. Finally the anti-bacterial study demonstrated that ZnO and Zn0.5Mg0.5O was effective in inhibiting E. coli bacteria.

Study of antibacterial performance of biosynthesized pure and Ag-doped ZnO nanoparticles

In the present paper, pure and silver-doped zinc oxide (Ag-doped ZnO) nanoparticles were prepared using a green route and employing Salvadora persica leaf extract. Antibacterial performance of synthesized nanoparticles (NPs) survey on gram-negative and gram-positive bacteria through disk diffusion and micro-dilution technics was also studied. The synthesized NPs were identified by X-ray diffraction (XRD), ultraviolet–visible (UV–Vis), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) analyses. XRD and EDX results presented that the silver was well doped into the structure of ZnO. In addition, spherical shape of this product, as well as the average size of 25–40 nm, were observed in the results of FESEM and TEM images. The results of disk diffusion and microdilution of synthesized nanoparticles showed that Ag-doped ZnO nanoparticles, have more antibacterial performance than pure zinc oxide nanoparticles on Staphylococcus aureus and Escherichia coli. So, synthesized NPs can be proposed as a choice in clinical and laboratory applications.

Controlled and localized drug delivery using Titania nanotubes

Titanium-dioxide nanotubes (TNTs) were fabricated by anodic oxidation of titanium (Ti) substrate and loaded with ciprofloxacin. A thin layer of Poly Lactic-co-Glycolic Acid (PLGA) was coated on top of the drug-loaded TNTs at various thicknesses. Field Emission Scanning Electron Microscopy (FESEM) was used to characterize the developed substrate. The FESEM images of anodized samples showed that, the native oxide layer on the surface of the Ti substrate was replaced with an array of ordered nanotubes up to ~700 nm in length. Drug release studies of ciprofloxacin were conducted in Phosphate Buffered Saline (PBS) solution for 24 h. The studies showed the ability of PLGA to slow down the drug release rate, depending on the thickness of the deposited layer. MG-63 cells (human osteosarcoma cell lines) were cultured on the TNT substrates after loading ciprofloxacin and coating with various concentrations of PLGA to show the potentiality for better osseointegration. An MTT assay was carried out to study cell viability and proliferation on these substrates. Anti-microbial studies were carried out to demonstrate the release of ciprofloxacin in treating infections against Staphylococcus epidermidis. These in-depth studies showed that local concentration of the drug released could be controlled by varying the thickness of the PLGA layer to allow for better implant osseointegration and treatment of bone infections.

Low temperature green methanol synthesis by CO2 hydrogenation over Pd/SiO2 catalysts in slurry reactor

The utilization of the greenhouse gas of carbon dioxide (CO2) for fuel and value-added chemicals synthesis has become globally indispensable process for healthy environment. In this context, the hydrogenation of CO2 to methanol is an attractive avenue for achieving such goal. Thus, we prepared mesoporous silica-supported nanocrystalline palladium metal (Pd) for methanol synthesis by CO2 hydrogenation. To investigate the role of Pd metal, the synthesized mesoporous silica was loaded with 1, 2, 3 and 4 wt% of Pd. Physicochemical profile of synthesized mesoporous silica supported Pd catalysts were assessed by Inductively coupled plasma - optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), Field-Emission Scanning Electron Microscopy (FESEM), Nitrogen adsorption–desorption and Temperature Program Reduction (TPR) techniques. ICP-OES measurement confirmed the actual Pd metal loading on the mesoporous silica support. XRD confirmed amorphous and crystalline nature of mesoporous silica and Pd metal, respectively. FESEM images exhibited homogenous and well dispersed Pd metal particles on the surface of mesoporuse silica support. Nitrogen adsorption desorption studies displayed enlargement in BET surface area with Pd promotion. Reduction behaviour of PdO was revealed by TPR data over the studied temperature range. The structure–activity studies suggested the degree of Pd crystallinity and higher dispersions as amongst the main factors contributing to the performance of Pd/SiO2 catalysts for pure CO2 hydrogenation in slurry reactor.

Effect of Calcium Carbonate Content on the Mechanical and Thermal Properties of Chitosan-Coated Poly(urethane) Foams

In this work, the effect of chitosan and CaCO3 coating on polyurethane (PU) foam on the mechanical and thermal properties was studied. PU-foams were soaked in a mixture of chitosan- calcium carbonate solution at different concentrations, i.e., 0.1–0.4%. The molecular behaviors due to the incorporation of chitosan/CaCO3 into the PU-foam matrix were investigated by Fourier-Transform Infrared (FTIR) spectroscopy. Field Emission Scanning Electron Microscope (FE-SEM) was utilized to study the effect of chitosan/CaCO3 coat on the pore structure of PU-foam. FTIR spectra show changes in the peak of 1446 and 1413 cm–1, which serve as evidence of molecular interaction between PU and chitosan/CaCO3. FE-SEM images show that the addition of chitosan/calcium carbonate cells was starting to close together, probably due to the increased dispersion of calcium carbonate on the entire surface of PU-foams/chitosan, which indicates that reducing the size of the cell will increase mechanical properties. From this study, it was found that PU-foam soaked in 0.4% CaCO3 had the highest tensile strength. Coating PU-foam with 0.4% CaCO3 also improved its thermal stability, indicated by an increase in its residual mass compared to neat PU-foam.

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Optimization of antibacterial activity of new poly(vinyl alcohol)–gum arabic–MgO nanoparticles bionanocomposite

Untreated dental caries is an important challenge in human life. In this work, the authors synthesized a new poly(vinyl alcohol) (PVA)–gum arabic (GA)–magnesium oxide (MgO) nanoparticle bionanocomposite and evaluated its antibacterial properties against Streptococcus mutans biofilm in vitro. For optimization of variables to obtain the maximum antibacterial properties, the L9 orthogonal array of the Taguchi method was used for the design of extraction conditions. The nanocomposites were characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy, thermogravimetric analysis and transmission electron microscopy. The FESEM images of the nanocomposite show that the nanoparticles are entirely surrounded with polymer chains of the matrix and nanoparticles are deposited on its walls; thus, a layered nanocomposite is formed. The sheet width and size ranges of the nanocomposite were determined to be between 30 and 40 and 20 and 90 nm, respectively. The results showed that the nanocomposite synthesized under conditions of 1 mg/ml PVA, 3 mg/ml GA and 6 mg/ml magnesium oxide (experiment 3) had the strongest antibacterial activity against the S. mutans bacteria’s biofilm. Under these optimal conditions, the bacterial survival rate was the lowest at 0.21 colony-forming units (CFU)/ml and the activity of S. mutans bacteria could be inhibited at a rate of 0.09 CFU/ml.