Elemental Mapping Analysis Research Articles

One–pot synthesis of gold nanoparticles using Pandanus amaryllifolius leaf extract and their antibacterial, antioxidant, anticancer, and ecotoxicity assessment

This work demonstrated a one–pot synthesis of gold nanoparticles (Au NPs) using Pandanus amaryllifolius leaf extract as well as their biological activity and biocompatibility impacts. The synthesized Au NPs were characterized by UV–vis, FT–IR, XRD, XPS, DLS, ZP, SEM, element mapping, EDX, and TEM analysis. The Au NPs tested against Gram–positive and negative bacteria of Staphylococcus aureus and Escherichia coli. The antioxidant capacity of Au NPs showed a moderate effect. Different concentrations of Au NPs were tested on the MDA–MB–231 epithelial human breast cancer cell line, showing that IC50 value at 118.26 μg/mL. Au NPs treated Artemia salina nauplii did not promote any mortality. By contrast, microphotographic analysis of the Au NPs found in the aggregated form inside the guts region. The 100% Au NPs treated Allium cepa root tip cell showed a mitotic index of 77.63 ± 0.42. This investigation demonstrates that Au NPs have better antioxidant and anticancer activities. In addition, the A. salina nauplii emphasized nontoxicity with biocompatibility. The Au NPs treatments showed a dose–depended response to enhance the mitotic cell divisions of A. cepa root tip cells without chromosomal aberration and no antibacterial efficiency of Au NPs against bacterial pathogens. Our study shows that this one–step synthesis is highly efficient. Near the future, synthesized Au NPs can be used for cancer therapeutic, food packaging, and cosmetic applications.

Table 1.Percentage (%) area coverage of elements Based of Imagej software analysis of elemental maps

Table 1.Percentage (%) area coverage of elements Based of Imagej software analysis of elemental maps

Synthesis of Ce and Sm Co-Doped TiO2 Nanoparticles with Enhanced Photocatalytic Activity for Rhodamine B Dye Degradation

One of the major concerns that receive global attention is the presence of organic pollutants (dyes, pharmaceuticals, pesticides, phenolic compounds, heavy metals, and so on), originating from various industries, in wastewater and water resources. Rhodamine B is widely used in the dyeing of paints, plastics, textiles, and other fabrics, as well as biological products. It is highly persistent, toxic, and carcinogenic to organisms and humans when directly released into the water supply. To avoid this hazard, several studies have been conducted in an attempt to remove Rhodamine B from wastewater. Metal oxide semiconducting materials have gained great interest because of their ability to decompose organic pollutants from wastewater. TiO2 is one of the most effective photocatalysts with a broad range of applications. Several attempts have been made to improve its photocatalytic activity. Accordingly, we have prepared in this work a series of cerium (Ce) and samarium (Sm) co-doped TiO2 nanoparticles (x = 0.00, 0.25, 0.50, 1.00, and 2.00%) using a sol–gel auto-combustion approach. The influence of Ce–Sm concentrations on the structural, morphology, electronic, and optical properties, as well as the photocatalytic activity, was investigated. Structure and elemental mapping analyses proved the presence of Ce and Sm in the compositions as well as the development of the TiO2 anatase phase with a tetragonal structure and crystallite size of 15.1–17.8 nm. Morphological observations confirmed the creation of spherical nanoparticles (NPs). The examination of the electronic structure properties using density functional theory (DFT) calculations and of the optical properties using a UV/Vis diffuse spectrophotometer showed a reduction in the bandgap energy upon Ce–Sm co-doping. The photocatalytic activity of the synthesized products was assessed on the degradation of Rhodamine B dye, and it was found that all Ce–Sm co-doped TiO2 nanoparticles have better photocatalytic activities than pristine TiO2 nanoparticles. Among all of the prepared nanoparticles, the sample with x = 0.50% demonstrated the best photocatalytic activity, with a degradation efficiency of 98% within 30 min and a reaction rate constant of about 0.0616 min−1. h+ and •O2− were determined to be the most important active species in the photocatalytic degradation process. Besides the high photocatalytic degradation efficiency, these photocatalysts are highly stable and could be easily recovered and reused, which indicates their potential for practical applications in the future.

Electrospun nanofibers of cellulose acetate/metal organic framework-third generation PAMAM dendrimer for the removal of methylene blue from aqueous media

In this research, magnetic metal–organic framework nanofibers were produced by the electrospinning method. The nanocomposite was functionalized by third generation hyperbranched poly(amidoamine) dendrimer (PAMAM) to improve its dye adsorption efficiency from aqueous media. The characteristics of the synthesized magnetic nanocomposite was determined by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) along with elemental mapping analysis and scanning electron microscopy (SEM). Central composite design (CCD) based on response surface methodology (RSM) was performed to optimize the adsorption variables and the values of coefficient of determination (R2) and adjusted R2 were 0.9837 and 0.9490, respectively. The results obtained demonstrated remarkable properties of the synthesized nanofiber as adsorbent for methylene blue from aqueous solutions with the removal efficiency of 95.37% and maximum methylene blue (MB) adsorption capacity of 940.76 mg g−1 under optimized conditions. In addition, it was shown that kinetics and adsorption isotherm of the dye removal process followed Langmuir and pseudo-second-order models, respectively. Thermodynamic study of the dye removal indicated that the process was spontaneous and favorable at higher temperatures. Also, the reusability study shows favorable dye removal efficiency of 80.67% even after 4 cycles. To investigate the performance of the adsorbent for the removal of MB in real samples, a sewage sample from a local hospital was used. The result showed good efficiency of the adsorbent.

Chemical-state distributions in charged LiCoO2 cathode particles visualized by soft X-ray spectromicroscopy

Lithium-ion deintercalation/intercalation during charge/discharge processes is one of the essential reactions that occur in the layered cathodes of lithium-ion batteries, and the performance of the cathode can be expressed as the sum of the reactions that occur in the local area of the individual cathode particles. In this study, the spatial distributions of the chemical states present in prototypical layered LiCoO2 cathode particles were determined at different charging conditions using scanning transmission X-ray microscopy (STXM) with a spatial resolution of approximately 100 nm. The Co L3- and O K-edge X-ray absorption spectroscopy (XAS) spectra, extracted from the same area of the corresponding STXM images, at the initial state as well as after charging to 4.5 V demonstrate the spatial distribution of the chemical state changes depending on individual particles. In addition to the Co L3-edge XAS spectra, the O K-edge XAS spectra of the initial and charged LiCoO2 particles are different, indicating that both the Co and O sites participate in charge compensation during the charging process possibly through the hybridization between the Co 3d and O 2p orbitals. Furthermore, the element maps of both the Co and O sites, derived from the STXM stack images, reveal the spatial distribution of the chemical states inside individual particles after charging to 4.5 V. The element mapping analysis suggests that inhomogeneous reactions occur on the active particles and confirm the existence of non-active particles. The results of this study demonstrate that an STXM-based spatially resolved electronic structural analysis method is useful for understanding the charging and discharging of battery materials.

Functionalized metal-organic framework UIO-66 nanocomposites with ultra-high stability for efficient adsorption of heavy metals: Kinetics, thermodynamics, and isothermal adsorption

BackgroundThis work reports an easily prepared, reusable and novel ethylenediamine tetramethylene phosphonic acid (EDTMP)-modified defective UIO-66-based metal-organic framework (MOF) for the removal of heavy metals especially Pb(II) from wastewater. MethodsThe adsorption process was determined by batch experiment. The synthesized materials were evaluated by advance characterization techniques including SEM, FTIR, XRD, TGA, XPS and elemental mapping analyses and the effect of reaction conditions on the adsorption process was evaluated. Significant findingsResults showed that the maximum adsorption capacity of UIO-66-EDTMP for Pb(II) was 381.195 mg/g, achieved at equilibrium time of 480 min at pH 5 and temperature 298 K, respectively. Langmuir, Hill, R-P and Sips isotherms and Pseudo second order (PSO) kinetic models well describes the adsorption process via multi-molecular, irreversible, and chemical adsorption process. Experimental and mechanistic tests have shown that the treatment of Pb by UIO-66-EDTMP consists mainly of chelation, ion exchange, electrostatic, and interactions between O, N, and P-containing groups. In addition, UIO-66-EDTMP showed better selectivity for Pb(II) compared to the treatment of Cd(II), Cu(II), Zn(II) and Ni(II) under coexistence and good reproducibility in five adsorption cycles. This work would serve as blueprint for further research into post-functionalized MOF materials for heavy metals removal from water.

Partial Miscibility and Concentration Distribution of Two-Phase Blends of Crosslinked NBR and PVC

We found that the blends of nitrile butadiene rubber (NBR) and polyvinyl chloride (PVC) exhibited lower critical solution temperature (LCST)-type phase behavior in which a single-phase blend tends to phase separate at elevated temperatures when the acrylonitrile content of NBR was 29.0%. The tan δ peaks, which originated from the glass transitions of the component polymers measured by dynamic mechanical analysis (DMA), were largely shifted and broader in the blends when the blends were melted in the two-phase region of the LCST-type phase diagram, suggesting that NBR and PVC are partially miscible in the two-phase structure. The TEM-EDS elemental mapping analysis using a dual silicon drift detector revealed that each component polymer existed in the partner polymer-rich phase, and the PVC-rich domains consisted of aggregated small PVC particles the size of several ten nanometers. The partial miscibility of the blends was explained by the lever rule for the concentration distribution in the two-phase region of the LCST-type phase diagram.

New protocol for functionalization of fullerene soot with dinitrobenzene groups from a non-diazonium resource

The nitrobenzene functionalized fullerene soot has been considered as a potentially energetic material. In our previous study, the in situ produced nitrobenzene diazonium ions have been used for the synthesis of 2-nitrobenzene, 4-nitrobenzene and 2,4-dinitrobenzene functionalized fullerene soot nanoparticles with moderate oxygen (14.91 wt%) and nitrogen (6.27 wt%) contents. In the present study, a new protocol for the functionalization of fullerene soot with 3,5-dinitrobenzene groups from a non-diazonium resource is reported. The functionalization of fullerene soot is performed through Ag(I)-catalyzed decarboxylative oxidation of 3,5-dinitrobenzoic acid (DNBA) under conventional heating or microwave irradiation. The effects of various parameters such as the oil bath temperature and the amounts of substrate (DNBA), catalyst (AgNO3) and oxidant (K2S2O8) on these reactions are evaluated. The synthesized compounds are characterized by FT-IR, Raman, XRD, SEM-EDX and elemental mapping analysis, FE-SEM and TEM along with particle size analysis, as well as TGA-DSC. The DSC thermograms of functionalized fullerene soot show a single exothermic peak attributed to the exothermic decomposition of 3,5-dinitrobenzene groups. Some of these compounds have up to 82.16 wt% oxygen and 6.10 wt% nitrogen contents. These findings are important for development of the energetic materials with improved oxygen content.

Enhanced Nitrogen Reduction to Ammonia by Surface- and Defect-Engineered Co-catalyst-Modified Perovskite Catalysts under Ambient Conditions and Their Charge Carrier Dynamics.

An electrocatalytic nitrogen reduction reaction is considered a potential approach for green ammonia production─a zero-carbon fertilizer, fuel, and energy storage for renewable energy. To harness the synergistic properties of perovskites, the inherent dipole moment due to their non-centrosymmetric structure (that facilitates better charge separation), oxygen vacancies, and the presence of Ni metal sites that permit activation and reduction of N2 efficiently, the NiTiO3-based nanoelectrocatalysts have been synthesized. Further, these catalysts have been modified with ultra-small metal nanocrystal co-catalysts to form heterointerfaces that not only aid to improve the charge separation but also activate N2 and lower overpotential requirements. The appearance of peaks corresponding to (012), (104), (110), (11-3), (024), (11-6), (018), (027), and (300) confirms the formation of rhombohedral NiTiO3. The shift in the XRD peak corresponding to the (104) plane to a smaller 2θ value and peak shifting and widening of Raman spectra imply the lattice distortion that signifies the formation of Pd-NiTiO3 and Pt-NiTiO3 heterojunction electrocatalysts with the loadings of 0.4 and 0.3 wt % of Pd and Pt, respectively, as confirmed by ICP-OES analysis. The detailed XPS analysis reveals the presence of Pd (0), Pd (II), and Pt (0), Pt (II) in respective electrocatalysts. The appearance of XPS peaks at 528.7 and 531.1 eV suggests the presence of oxidative oxygen species (O2-/O-) and the presence of oxygen defects due to oxygen vacancy. The detailed nitrogen reduction (NRR) investigation exhibits a 5-fold enhancement in ammonia yield rate (∼14.28 μg h-1 mg-1 at -0.003 V vs RHE), a faradic efficiency of 27% (at 0.097 V vs RHE) for Pd-NiTiO3 electrocatalysts than that for bare NiTiO3 (3.08 μg h-1 mg-1), and 9-folds higher than that of the activity shown by the commercial TiO2 (P25) (1.52 μg h-1mg-1). The formation of ammonia was further confirmed by using isotopic nitrogen as the feeding gas. Furthermore, the highest NRR is observed at lower cathodic potential (-0.003 V vs RHE) in the case of the Pd-NiTiO3 electrocatalyst than that of the Pt-NiTiO3 electrocatalyst (-0.203 V vs RHE), implying significantly reduced overpotential requirement. Such enhanced NRR activity with lower overpotential requirement in the case of the Pd-NiTiO3 electrocatalyst is due to efficient charge separation as shown by the semicircle Nyquist plot, decreased photoluminescence emission intensity, shorter average lifetime (∼29 ns) of excitons, appropriate band bending, and improved activation of N2 by the oxygen vacancies and heterointerface formed between Pd nanocrystals and NiTiO3. Furthermore, no change is observed in the current density, after stabilization in the initial few seconds, even up to 2 h, which signifies that these electrocatalysts are stable. The structural and morphological integrity of the optimized catalyst remained even after the nitrogen reduction reactions, as revealed by no significant change observed in FESEM, elemental mapping, and EDS analysis.

Process ambient effects on amorphous phase control of Sn-doped CuI films: Towards flexible transparent photodetector application

Herein, process ambient effects on controlling the amorphous phase of Sn-doped CuI films (Sn-CuI) via a direct solution spin coating are reported. The structural analysis reveals that the Sn-CuI films fabricated in the glove box exhibit an amorphous phase, whereas films processed in the atmospheric environment have a crystalline phase. XPS and elemental mapping analysis validate Cu-rich chemical composition for prepared CuI and Sn-CuI films, and morphology and uniformity of the films are manifested by scanning electron microscopy (SEM). The optical transparency (∼60%), the highest photosensitivity (395.25 ± 25.26%), photoresponsivity (Rph= (214 ± 21.35)mA/W), linear dynamic range (LDR=(15.38 ± 0.67)dB) and others, under 365 nm are achieved for Sn-CuI devices at Vb = 3 V. These results suggest that this platform can be a potential material for flexible transparent photodetectors.

Trans‐metallated chlorophyllin by copper supported on silica‐coated magnetic nanoparticles as an efficient and green catalyst for the synthesis of furan‐2(5H)‐ones

In recent years, an unprecedented increase in environmental pollution as a result of the rapid industrialization of the world has attracted a lot of attention to green chemistry. Chlorophyllin copper complex (Chln‐Cu) is one of the most vital compounds derived from natural chlorophyll that can be used as an environmental, sustainable, and green catalyst in industrial processes. In the current paper, chlorophyll was first extracted from spinach leaves, hydrolyzed, and trans‐metallated to chlorophyllin copper (II) complex. The fixation of Chln‐Cu on functionalized magnetic nanoparticles was performed using a green mechanical method. This mechanical solvent‐free reaction was done in a planetary ball mill with 60 zirconia balls (diameter = 3 mm) and the rotation speed 200 rpm at 12 h. In conclusion, an efficient and reusable Fe3O4@SiO2‐NH2‐Chln‐Cu catalyst was obtained. To characterize the synthesized catalyst, several analytical techniques were used such as UV–Vis, FT‐IR, 1H‐NMR, and 13C‐NMR spectra as well as TG, ICP‐OES, XRD, FE‐SEM, elemental mapping, VSM, and XPS analyses. The conducted analyses showed that the catalyst was successfully synthesized. The efficiency of the catalyst was checked in the preparation of 3,4,5‐trisubstituted furan‐2(5H)‐one derivatives at room temperature in propylene carbonate as a green solvent. Moreover, the effect of time, temperature, and solvent on the reaction yield was thoroughly investigated. Excellent performance at mild, environmentally friendly, and nontoxic conditions showed that Fe3O4@Si‐Chln‐Cu not only is an excellent catalyst for this process but also it can be an outstanding catalyst for other catalytic reactions.

Chitosan bead containing metal–organic framework encapsulated heteropolyacid as an efficient catalyst for cascade condensation reaction

Using cyclodextrin and chitosan that are bio-based compounds, a novel bi-functional catalytic composite is designed, in which metal–organic framework encapsulated phosphomolybdic acid was incorporated in a dual chitosan-cyclodextrin nanosponge bead. The composite was characterized via XRD, TGA, ICP, BET, NH3-TPD, FTIR, FE-SEM/EDS, elemental mapping analysis and its catalytic activity was examined in alcohol oxidation and cascade alcohol oxidation–Knoevenagel condensation reaction. It was found that the designed catalyst that possess both acidic feature and redox potential could promote both reactions in aqueous media at 55 °C and various substrates with different electronic features could tolerate the aforementioned reactions to furnish the products in 75–95% yield. Furthermore, the catalyst could be readily recovered and recycled for five runs with slight loss of the catalytic activity. Notably, in this composite the synergism between the components led to high catalytic activity, which was superior to each component. In fact, the amino groups on the chitosan served as catalysts, while cyclodextrin nanosponge mainly acted as a phase transfer agent. Moreover, measurement of phosphomolybdic acid leaching showed that its incorporation in metal–organic framework and bead structure could suppress its leaching, which is considered a drawback for this compound. Other merits of this bi-functional catalyst were its simplicity, use of bio-based compounds and true catalysis, which was proved via hot filtration.

Electroreduction of CO2 on Au(310)@Cu High-index Facets.

The chemical selectivity and faradaic efficiency of high-index Cu facets for the CO2 reduction reaction (CO2 RR) is investigated. More specifically, shape-controlled nanoparticles enclosed by Cu {hk0} facets are fabricated using Cu multilayer deposition at three distinct layer thicknesses on the surface facets of Au truncated ditetragonal nanoprisms (Au DTPs). Au DTPs are shapes enclosed by 12 high-index {310} facets. Facet angle analysis confirms DTP geometry. Elemental mapping analysis shows Cu surface layers are uniformly distributed on the Au {310} facets of the DTPs. The 7 nm Au@Cu DTPs high-index {hk0} facets exhibit a CH4 : CO product ratio of almost 10 : 1 compared to a 1 : 1 ratio for the reference 7 nm Au@Cu nanoparticles (NPs). Operando Fourier transform infrared spectroscopy spectra disclose reactive adsorbed *CO as the main intermediate, whereas CO stripping experiments reveal the high-index facets enhance the *CO formation followed by rapid desorption or hydrogenation.

Electroreduction of CO2 on Au(310)@Cu High‐index Facets

AbstractThe chemical selectivity and faradaic efficiency of high‐index Cu facets for the CO2 reduction reaction (CO2RR) is investigated. More specifically, shape‐controlled nanoparticles enclosed by Cu {hk0} facets are fabricated using Cu multilayer deposition at three distinct layer thicknesses on the surface facets of Au truncated ditetragonal nanoprisms (Au DTPs). Au DTPs are shapes enclosed by 12 high‐index {310} facets. Facet angle analysis confirms DTP geometry. Elemental mapping analysis shows Cu surface layers are uniformly distributed on the Au {310} facets of the DTPs. The 7 nm Au@Cu DTPs high‐index {hk0} facets exhibit a CH4 : CO product ratio of almost 10 : 1 compared to a 1 : 1 ratio for the reference 7 nm Au@Cu nanoparticles (NPs). Operando Fourier transform infrared spectroscopy spectra disclose reactive adsorbed *CO as the main intermediate, whereas CO stripping experiments reveal the high‐index facets enhance the *CO formation followed by rapid desorption or hydrogenation.

Nickel Cobalt LDH/Graphene Film on Nickel-Foam-Supported Ternary Transition Metal Oxides for Supercapacitor Applications

Layered double hydroxides (LDHs) of transition metals have attained significant attention for supercapacitor applications due to their excellent charge storage, low internal resistance, and superior electrochemical stability. Here, a nanocomposite of reduced graphene oxide/nickel cobalt layered double hydroxide (rGO/NiCo LDH) on the surface of nickel foam (NF) containing hierarchical nickel cobalt copper transition metal oxides (TMOs) is prepared through two-step processes of electrochemical and coprecipitation methods. The TMOs/rGO/NiCo LDH nanocomposite is characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman, X-ray energy-dispersive (EDS), and X-ray photoelectron (XPS) spectroscopies as well as by transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), elemental mapping analysis, nitrogen adsorption/desorption, and contact angle measurements. The supercapacitive behavior of the electrodes has been investigated through cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) measurements, and electrochemical impedance spectroscopy (EIS). The study has shown that the synergetic effect and the electrochemical properties have considerably improved when the layered double hydroxides are synthesized in the presence of rGO. The TMOs/rGO/NiCo LDH nanocomposite exhibits an excellent specific capacitance of 2763 F g–1 at a current density of 1 A g–1 and a stability of 85% after 3000 GCD cycles at a current density of 24 A g–1. Also, a TMOs/rGO/NiCo LDH//rGO asymmetric supercapacitor device is constructed with an aqueous KOH electrolyte, which shows a capacitance of 244 F g–1 at a current density of 1 A g–1. The device attains the highest energy density of 34 Wh kg–1 and power density of 2500 W kg–1, with an excellent cycling stability of 100% after 3000 GCD cycles at a current density of 10 A g–1.

Gamma Attenuation and Mechanical Characteristics of a Lead/NBR/SBR Rubber Composite with Black Nanocarbon Reinforcement

In this work, black nanocarbon-loaded 0–100 parts-per-hundred (phr) PbO-filled acrylonitrile butadiene rubber (NBR)/styrene-butadiene rubber (SBR) blend composites were prepared by using an ordinary standard rubber mixer. Both mechanical and gamma attenuation properties of the prepared samples were investigated. Maximum tensile strength and elongation at break were obtained at 40 phr PbO concentration. The obtained values for the mass attenuation coefficient with the increased PbO concentration from 0–100 phr ranged from 0.12–0.22 cm2/g at 0.239 MeV. Scanning electron microscope (SEM) with the elemental mapping analysis results showed high homogeneity at 40 phr of the prepared rubber composites, with some areas of elemental agglomeration at a high concentration of lead oxide. The obtained results highly recommend the use of the prepared nanocarbon-reinforced PbO/NBR/SBR blend compared to those previously used as personal protective equipment in radiation-shielding applications.

Preparation of gold nanoparticles using monoolein cubic phase as a template

MO cubic phase containing gold nanoparticle (GNP) was prepared by hydrating MO melt with gold ion solution to synthesize GNP of different sizes and shapes. A TEM microscopy and an elemental mapping analysis disclosed that GNP could be formed within the cubic phase. GNP prepared in an aqueous solution (GNP(W)) exhibited its surface plasmon resonance (SPR) spectrum in the visible light region with the peak around 528 nm and it was a sphere of which diameter was 10–30 nm. Besides a SPR spectrum in the visible light region, GNP formed in the cubic phase (GNP(CP)) showed its SPR spectrum spanning from the far-red to the near-infrared region, indicating GNP(CP) was gold particles of different sizes and shapes. In fact, non-spherical particles, including tetrahedron, decahedron, and rod, were found on the TEM photo of GNP(CP) and were larger than GNP(W). Furthermore, GNP(CP) exhibited the inherent lattice constant of gold, confirmed by a high-resolution TEM microscopy and an X-ray diffraction spectroscopy, indicating that various gold particles of different sizes and shapes could be formed in the cubic phase, maintaining its intrinsic crystalline structure.

MOx@VOx‐Pd‐type Nanorods and Nanotubes as Catalysts for Selective Reduction of NO

AbstractVanadium oxide (VOx‐Pd) nanotubes as well as VOx‐coated ZnO nanorods (ZnO@VOx‐Pd) and VOx‐coated, layered‐titania nanotubes (l‐TiO2@VOx‐Pd) are decorated with Pd nanoparticles and evaluated for selective catalytic reduction with hydrogen (H2‐SCR) for the first time. The nanostructures exhibit lengths of 300 to 700 nm, diameters of 20–100 nm and, in the case of the nanotubes, an inner tube diameter of about 10 nm. Pd nanoparticles (14±5 nm) are well‐dispersed over the respective nanorod/nanotube nanostructure. Structure and composition are characterized by SEM, TEM, EDXS with element mapping, XPS, FT‐IR, XRD, and sorption analysis. Thermal analysis indicates the nanostructures to be thermally stabile up to 350 °C (VOx), and 500 °C (ZnO@VOx, l‐TiO2@VOx). All catalysts are tested for their activity in regard of the selective catalytic reduction of NO with H2, revealing a significant impact of the catalyst support on both activity and selectivity. Specifically, l‐TiO2@VOx nanotubes show promising properties with an activity up to 70 % and a selectivity up to 80 % N2.

Electrochemical detection of riboflavin in pharmaceutical and food samples using in situ electropolymerized glycine coated pencil graphite electrode

The electronic conductivity and electrocatalytic property of an electrode can be improved by coating its surface with a thin film, polymer or some nanomaterial; however, the fabrication procedure is time-consuming, expensive, and require multistep. In this study, an electrochemically polymerized polyglycine-coated pencil graphite electrode (PGl/PGE) was prepared for the sensitive detection of riboflavin (RF). The formation of glycine polymer on the PGE surface was confirmed by Fourier transform infrared (FTIR), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and elemental mapping analysis. The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed that the charge transfer on PGl/PGE was significantly enhanced when compared to PGE. The fabricated PGl/PGE sensor was used to detect riboflavin (RF) in 0.2 M phosphate buffer (pH 7.0) using square wave voltammetry. The linear concentration range of RF was 2–450 nM under optimized conditions, with a calculated limit of detection of 1.24 nM. Finally, some critical sensor parameters such as sensitivity, selectivity, stability, and reproducibility were evaluated and practically applied for RF detection in pharmaceutical and food samples.

Facile synthesis of a new covalent organic nanosheet (CON-KEY1) based on polyamide links as an effective heterogeneous catalyst in C-C cross coupling reactions.

C-C coupling reactions represent a fundamental synthetic methodology widely employed in academic and industrial settings. Herein, we present a report on developing and synthesizing a heterogeneous catalyst that is environmentally compatible and has recycling capabilities. Furthermore, the utilization of this catalyst for C-C coupling reactions was explored. A novel amide-based CON was prepared via the reaction of a novel [2,2'-bipyridine]-5,5'-diamine (BDA) and 1,3,5-tris(4-carboxyphenyl) (TCB). TCB was activated with carbonyl diimidazole (CDI) and then reacted with BDA to synthesize favorable CON (i.e., CON-KEY1). Finally, the CON synthesized was reacted with palladium chloride ions, and the palladium-containing organocatalytic complex was decorated with the abbreviated Pd/CON-KEY1. This new heterogeneous complex was fully characterized through the required techniques, including FT-IR, EDX, XRD, TEM, SEM, ICP, TGA-DTA, N2 isotherms, and elemental mapping analysis. Computer simulation results include a multi-sheet 2D framework proposed by CON-KEY1. As a result, palladium ions were found to be arranged between the layers and on the CON surface. This heterogeneous complex functioned as a catalyst precursor in both the Suzuki-Miyaura coupling reaction of aryl boronic acids with aryl halides and the Heck reaction of aryl halides with acrylate derivatives or styrene. The desired coupling products with various functional groups were successfully attained with excellent yields of up to 98%. Simple set-up, improved yields, short reaction times, non-toxic solvents, catalyst durability, and high turnover frequency are among the distinct advantages of this synthetic method. Some other outstanding features of this catalytic system include convenient separation of catalysts and products, high yields, almost complete conversion, high selectivity, and good turnover frequency (TOF). The results show that the highest product efficiency in the reaction was achieved in the shortest possible time using Pd/CON-KEY1. Theoretical studies demonstrated the precedence of the palladium complexation with nitrogen atoms of CON-KEY1 rather than oxygen ones. Natural Bond Orbital (NBO) analysis affirmed that the system with Pd-N bonds (Eg = 0.089 eV) is more reactive with high electron conductivity compared to the Pd-O system (Eg = 0.120 eV).