Alfa Aesar Research Articles

Synergistic effects of silver nanoparticles in combination with ineffective antibiotics against multidrug resistant Salmonella typhi.

To determine the antimicrobial activity of silver nano-particles(AgNPs) with tetracycline and ampicillin against multi-drug resistance (MDR) and extensively-drug resistance (XDR) Salmonella typhi. Cross sectional non-probability purposive study was conducted from September, 2021 to May, 2022 at Microbiology department PNS Shifa, Hospital Karachi. Blood cultures of patients suspicious of typhoid fever were collected and incubated in automated Bact/Alert system. Positive cultures were identified on blood and MacConkey and processed by API-10S, confirmed by serotyping (O9 antisera) (SSI Diagnostica's Salmonella). Antibiotic resistance was done by Kirby-Bauer disk diffusion (Sigma and Rich). MDR and XDR isolates were preserved in Brain Heart Infusion in a volume of 2ml in screw capped bottles at -70°C. Antimicrobial powders (ampicillin and tetracycline (Alfa Aesar) weighed by an electrical weighing balance (OHAUS) to take 1mg of antimicrobial drug. Absorbance spectra of serial concentrations of antibiotics (UV-Vis spectrophotometer (Mole-Qule-) AgNPs (10nm) (nanocomposix) + Antibiotic in (1:1 volume ratio). Conjugation of silver nanoparticles with tetracycline and ampicillin was done by FTIR (thermos scientificThermos ScientificNicolet 50). Out of 77 isolates, 54 were resistant to ceftriaxone (XDR) and 23 sensitive to ceftriaxone (MDR). All isolates were susceptible to azithromycin and meropenem. Comparison of zone of inhibitions of ampicillin and Amp-AgNPsas and tetracycline with Tet-AgNPs was done. Minimal inhibitory concentration was also done to determine antimicrobial activity. Significant synergistic inhibitory effects against Salmonella Typhi isolates were obtained by combination of tetracycline with silver nano-particles even at low concentration.

(Invited) Fundamental Structure-Function Relationships for Iridium Oxide Catalysts in PEM Water Electrolyzers

The intermittency of renewable energy poses significant challenges to developing a grid system that utilizes primarily renewable-based sources. Proton exchange membrane water electrolyzers (PEMWEs) can convert surplus energy from the grid into chemical energy in the form of green hydrogen, which can then be used to generate electricity when the renewable supply is low. Despite much technological advancement over the last two decades, PEMWEs still face many barriers to widespread commercialization. Around a quarter of the cost of the PEMWE system is attributed to iridium, a highly scarce material used as the oxygen evolution reaction (OER) catalyst on the anode side. To enable lower loadings/higher utilization of these catalysts, fundamental studies on iridium activity and degradation are necessary. As it stands in the literature, studies on how physical properties of the catalyst (i.e. crystallinities, valance states, etc.) affect PEMWE performance are scarce. This work aims to elucidate the relationship between structural properties and efficiency/performance for iridium oxide (IrOx ) catalysts in PEMWEs. Five commercially available iridium oxide catalysts were characterized (47491 Alfa Aesar, TEC77100, TEC77110, FIO-01, FIO-11) using transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) analysis, and x-ray diffraction (XRD) to obtain crystallinities, particle size distributions, specific surface areas, thermal stabilities, elemental compositions, and valance states. Afterwards, kinetic performance was baselined by taking cyclic voltammograms (CVs) via rotating disk electrode (RDE) experiments and electrochemical surface areas (ECSA) were approximated by using a novel analysis developed in this work that can relate the hysteresis in OER potentials to a double layer capacity. Results show that greater amorphous character of IrOx was correlated with increased kinetic performance at the expense of electrochemical stability across redox potentials between 0-1.6V. From the cyclic voltammograms, the catalyst with the most amorphous character underwent multiple (two, possible three) redox transitions, while the one with the most crystalline character showed no evidence of any redox transitions. It was also found that increased ECSA was correlated with greater physical surface areas obtained from BET analysis and that greater amorphous character resulted in a higher Ir III :Ir IV ratio. For future work, we aim to incorporate these fundamental structure-function insights to create standardized accelerated stress tests for PEMWEs, as standards for durability testing have yet to be established.

Ex-situ spark plasma sintered MgB2 with Ge-based organometallic additions: Key ingredients for superconductivity enhancement

Dense samples of MgB2, with a relative density of 98.3–99.1 %, were prepared by ex-situ spark plasma sintering using a raw powder supplied by Alfa Aesar. Samples were added with Ge-based organometallics (repagermanium/RGe, propagermaniu/PGe, linear Ge-based organometallic/GeSP, and Na-doped octamer/8THGP-Na) for the starting composition (MgB2)(Ge-based organometallics)0.0014. Except for the 8THGP-Na, they have a similar chemical composition in respect to Ge and C, while the crystal structure differs. Below 20 K, all studied additions increased the critical current density, Jc, and the irreversibility field, Hirr. Samples added with GeSP and 8THGP-Na have marginal differences regarding superconducting characteristics. The best Jc and Hirr are obtained for the sample added with RGe. This sample has the highest amount of carbon in the crystal lattice of MgB2. Results point out that there is a complex influence of the additive on carbon behaviour. Although in general it is accepted that a higher amount of carbon produces higher Jc and Hirr, a comparison with the literature indicates that C-rich raw MgB2 powders (e.g. the C-enhanced MgB2 nanopowder produced by Pavezyum) are not suitable to promote strong superconductivity enhancement in the samples added with indicated organometallics, and the origin, states, and evolution of carbon should to be carefully assessed.

A Novel Alkali Precipitation Method for Tungsten Separation and High‐Precision Isotopic Measurement in Geological Samples

Tungsten (W) isotopes are useful tools in geological and cosmochemical research, but the chemical separation of W is cumbersome for high‐precision measurement. Here, a novel alkali (sodium hydroxide, NaOH) precipitation method for separation and purification of W in geological samples is described, which simplifies the chemical procedure. The amphoteric character of W is exploited to separate it from most matrix elements in alkaline conditions. Subsequently, TEVA resin was applied to further purify W for measurements using a multi‐collector inductively coupled plasma‐mass spectrometer. Importantly, the introduction of a certain amount of Na in the W analyte can increase the signal intensity by approximately 1.6 times, which may be caused by Coulomb fission. Such Na‐triggered signal enhancement reduces the test portion mass required for analysis. Our results show that the Alfa Aesar W standard solution and geological reference materials JB‐3, BCR‐2 and BHVO‐2 yield 182W/184W ratios consistent with previously reported values within uncertainty. Repeated measurement of the Alfa Aesar W standard solution shows that the intermediate precision of 182W/184W was better than 5 ppm (2s), which is sufficient to identify subtle 182W isotope variations in terrestrial and extra‐terrestrial samples. Above all, the alkali precipitation method in this study optimises the experimental process and mass spectrometric analysis.

Thermal expansion of oldhamite, CaS: Implication for the surface of Mercury

The temperature excursion variation of Mercury's surface may significantly change crystal structure of surface-comprising minerals. The thermal stability of oldhamite (CaS) was investigated to validate its presence on the Mercury's surface. In particular, X-Ray Powder Diffraction (XRPD) and Thermogravimetric Analyses (TGA) on synthetic powder calcium sulfide (Alfa Aesar) were performed with the aim of confirming its stability up to 723.15 K, the highest temperature that is recorded for the surface of Mercury.Our results by XRPD and TGA results confirmed that CaS phase is stable within the daily temperature excursion on Mercury surface. Thermal expansion analyses determined the thermal expansion volume coefficient of αV = 4.03 × 10−5 K−1. The results of this work support the presence of Ca-sulfide phases on Mercury's surface and provide valid tools for interpreting the data that will be collected by the BepiColombo space mission (European Space Agency and Japanese Aerospace Exploration Agency) to Mercury.

Methanol steam reforming kinetics using a commercial CuO/ZnO/Al2O3 catalyst: Simulation of a reformer integrated with HT-PEMFC system

This study provides a kinetic examination of methanol steam reforming (MSR) over a Cu-based commercial catalyst (CuO/ZnO/Al2O3, Alfa Aesar) as a function of CH3OH and H2O partial pressures at 246 °C and 1 atm in a once-through flow reactor. A power rate law was used to best describe the experimental rate data by linear and non-linear regressions at the operating conditions where transport bottlenecks were eliminated. Comparison of the rate parameters indicated that a strong correlation was suggested by non-linear regression giving reaction orders of 0.29 for methanol and 0.09 for water along with a frequency factor of 53.48 (molCH3OH s−1 gcatalyst−1 kPa−0.38) and an activation energy of 65.59 kJ mol−1. A simulation study of the rate equation to analyze an integrated system of a reformer and an HT-PEMFC was also conducted. The results demonstrate that the system has the potential to produce 15 W power output.

Магнитные композиты на основе эпоксидной смолы с магнитными микро- и наночастицами оксида железа: фокус на магнитное детектирование

Magnetic and structural properties iron oxide micro- and nanoparticles and composites based on epoxy resin at different mass concentrations of particles are investigated (0, 5, 10, 30%). Commercial Alfa Aesar microparticles and nanoparticles obtained by electric explosion of wire with different dispersion parameters were compared. Magnetoimpedance detection of stray magnetic fields of the obtained composites in the form of cylinders using a strip multilayer film element [FeNi/Cu]5/Cu/[FeNi/Cu]5 was carried out. It is shown that it is possible to determine the position of filled magnetic composites at different mass concentrations of magnetic micro- or nanoparticles with different parameters of dispersion of the ensemble using magnetoimpedance detection. Ключевые с

Global palladium market report to 2031 - featuring Alfa Aesar, China North Industries, Indian Platinum and, Norilsk Nickel among others

Global palladium market report to 2031 - featuring Alfa Aesar, China North Industries, Indian Platinum and, Norilsk Nickel among others

Stable W Isotope Measurements of Geological Reference Materials and Tungsten Ore Minerals by Double Spike MC‐ICP‐MS

This study presents high‐precision W isotopic measurement results using the 180W‐183W double spike technique with MC‐ICP‐MS. The effects of isobaric and polyatomic interferences on W isotopic measurements were evaluated. The δ186/184W values were not significantly affected when the solution had Hf/W ≤ 3 × 10‐4, Ta/W ≤ 1, Os/W ≤ 0.06, Ce/W ≤ 0.0075, Nd/W ≤ 3.5 and Sm/W ≤ 5. The intermediate measurement precisions of both standard solutions (NIST SRM 3163 and Alfa Aesar W) and geological reference materials (NOD‐A‐1) were better than ±0.024‰ (2s). We also obtained a precision of 0.026‰ for a minimum sample loading mass of 5 ng, allowing the analysis of samples with low W contents. Replicated measurements of geological reference materials (AGV‐2, BCR‐2, BHVO‐2, GSP‐2, RGM‐1, SDC‐1, NOD‐A‐1 and NOD‐P‐1) yielded δ186/184W values ranging from 0.017‰ to 0.144‰. The δ186/184W values of two major tungsten ore minerals (scheelite and wolframite) were reported and compared herein. Scheelites had systematically slightly heavier W isotopic compositions than wolframites, which may reflect differences in the crystal structure. The resolvable variations of stable/mass‐dependent W isotopic compositions in rocks and ore minerals make W isotopes a novel tool for studying hydrothermal mineralisation processes and the W cycle of geological reservoirs.

D 6 h Symmetric Radical Donor–Acceptor Nanographene Modulated Interfacial Carrier Transfer for High-Performance Perovskite Solar Cells

<i>D</i> ^{6 <i>h</i>} Symmetric Radical Donor–Acceptor Nanographene Modulated Interfacial Carrier Transfer for High-Performance Perovskite Solar Cells

Functionalized carbon nanotube and carbon nanodot modified multiblock poly(arylene ether ketone sulfone) copolymer as proton exchange composite membranes for fuel cell applications

AbstractThe present study describes the successful synthesis of –COOH functionalized carbon nanodots (f‐CNDs) via pyrolysis of citric acid and 4,4′‐bis(4‐hydroxyphenyl)valeric acid (DPA‐OH, Sigma Aldrich, St. Louis, Missouri, United States) based hydrophilic oligomer at 250 °C. The multiblock copolymers were prepared by a coupling reaction between phenoxide terminated valeric acid based poly(arylene ether ketone) (DPA‐OH) hydrophilic oligomer and decafluorobiphenyl (DFBP, Alfa Aesar, Haverhill, Massachusetts, United States) end‐capped poly(arylene ether sulfone) (BP‐X‐F) hydrophobic oligomers (where X is 6, 9 and 12). Multiblock poly(arylene ether ketone sulfone) copolymer crosslinked membranes were prepared using 6F‐bisphenol‐A based novolac epoxy resin (EFN) and –COOH functionalized multiwalled carbon nanotubes/functionalized carbon nanodots (f‐MWCNTs/f‐CNDs, Nanoshell company, Utah, U. S) were used for the preparation of acid doped composite membranes for fuel cell applications. From high resolution TEM images, the average size of the prepared f‐CNDs found to be ca 10–12 nm. The N1 multiblock copolymer membrane with loading of 0.9 wt% ratio of CNTs showed better proton exchange membrane related properties such as proton conductivity (0.136 S cm−1), ion exchange capacity (1.18 meq g−1) and selectivity ratio (0.17) compared to the prepared pristine, crosslinked and CND based composite membranes. The overall results revealed that the composite membranes with loading of 0.9 wt% of CNTs and CNDs exhibited a superior combination of fuel cell related properties such as higher proton conductivity, high dimensional and oxidative stability and low methanol permeability and also showed better fuel cell performance compared to the respective pristine and EFN crosslinked membranes. © 2022 Society of Industrial Chemistry.

Spin-Enhanced C–C Coupling in CO 2 Electroreduction with Oxide-Derived Copper

Spin-Enhanced C–C Coupling in CO ₂ Electroreduction with Oxide-Derived Copper

(Digital Presentation) Selective Lead Recovery from a Mixture of Lead and Tin for Silicon Solar Module Recycling

During the recycling of solar modules, it is imperative to recover all the toxic lead used in solder. In this experiment, acetic acid is investigated for lead leaching and electrowinning from a mixture of lead and tin. 0.0636 g of tin powder (Alfa Aesar, 325 mesh, 99.8%) and 0.0372 g of lead powder (Alfa Aesar, 100 mesh, 99.95%, atomized) were combined with 30 mL of 0.01 M acetic acid (Sigma Aldrich) and 100 μL hydrogen peroxide (Alfa Aesar, ACS, 29-33% w/w). The solution was allowed to sit for 48 hours before electrowinning to allow the hydrogen peroxide to decompose. A copper working electrode, graphite counter electrode, and silver/silver chloride reference electrode were used in a three-electrode system.A cyclic voltammogram shows lead reduction around –0.4 V vs Ag/AgCl, and a large stripping peak around –0.05 V. There is only one set of redox peaks in the graph, indicating only lead is reduced and oxidized. EDX confirms the presence of metallic lead on the working electrode after electrowinning at –0.6 V vs Ag/AgCl for 90 minutes. Only lead is present on the working electrode surface, no tin. These results show acetic acid to be a promising leachate for the electrowinning of metallic lead from silicon solar module solder waste. Figure 1

Large-scale production of Fe3O4 nanopowder using ferrous ions in a rotating packed bed with precipitation

This study concerns the use of the rotating packed bed (RPB) in the large-scale production of Fe3O4 nanopowder using ferrous ions and precipitation. Fe3O4 nanopowder was produced at 25 °C with an FeCl2 concentration of 0.15 mol/L, an NaOH concentration of 0.3 mol/L, a rotational speed of 1800 rpm, and flow rates of aqueous FeCl2 and NaOH of 0.5 L/min. The rate of large-scale production of Fe3O4 nanopowder using ferrous ions in the RPB with precipitation was 7.6 kg/day. The produced Fe3O4 nanopowder had a mean crystallite size of 28.4 nm, an average particle size of 34.5 nm, and a BET specific surface area of 32.5 m2/g. The produced Fe3O4 nanopowder displayed ferromagnetic behavior with a saturation magnetization of 37 emu/g. The adsorption of Orange G (OG) in water was utilized to assess the adsorption capacity of the produced Fe3O4 nanopowder. The maximum adsorption capacity (17.5 mg/g) of the produced Fe3O4 nanopowder greatly exceeded that (2.4 mg/g) of Fe3O4 nanopowder that was purchased from Alfa Aesar.

Inhibition by Ascorbate among Phosphofructokinase-1, Aldolase, Enolase, and Lactate Dehydrogenase in Rabbit Muscle

Background: These studies examined mutual protective relationships among rabbit muscle aldolase, enolase, phosphofructokinase-1 (PFK-1) and LDH from inhibitions by ascorbate (AA). It was proposed earlier that specific inhibitions of PFK-1 and LDH by AA faciltated glycogen storage in resting muscle by inhibiting glycolysis. Materials and Methods: The L-ascorbate (AA), L-ascorbyl dibutyrate (AADB), L-ascorbyl dipalmitate (AADP), L-ascorbyl palmitate (AAP), and L- ascorbyl stearate (AS) are shown in Figure 1 and were obtained from TCI and Alfa Aesar. Unless otherwise stated, all enzymes come from rabbit and all experimental temperatures were 25°C, pH 8.0. Results: Rabbit muscle enolase was examined for its protective effect on other rabbit muscle glycolytic enzymes against inhibitions by ascorbate (AA) and some AA-faty acid derivatives. The IC50 values of enolase by ascorbate (AA) and IC50 values of AA-fatty acid derivatives were compared to estimate inhibition potency. For example, ascorbyl dipalmitate (AADP) was 156 times more inhibitory to enolase than AA. It was previously shown that rabbit muscle aldolase prevented LDH activity loses due to AA inhibition and prevented PFK-1 activity losses due both to dilution and AA inhibition; enolase was found to have the same effects as aldolase. Additionally, PFK-1 prevented enolase and LDH inhibitions by AA. LDH did not prevent enolase or PFK-1 from inhibition by AA. LDH did stimulate enolase activity but not PFK-1 activity. Conclusion: The results suggest that interactions among glycolytic enzyme serve to mutually protect one another from activity losses. The inhibition properties of the AA-fatty acid derivatives are discussed in relation to their possible roles in cancer and diabetes.

BiO 2-x Nanosheets with Surface Electron Localizations for Efficient Electrocatalytic CO 2 Reduction to Formate

BiO _2-x Nanosheets with Surface Electron Localizations for Efficient Electrocatalytic CO ₂ Reduction to Formate

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Highly Sensitive Photodetector Based on the n-Si/p-GaSe Vertical Heterojunction

Photodetectors based on two-dimensional materials and their van der Waals (vdW) heterojunctions usually have excellent optoelectronic performance and great potential applications. Herein, gallium (Aladdin, particles, 99.999% trace metal basis), selenium (Aladdin, powder, 99.999% trace metal basis), and iodine (Alfa Aesar, 99.999% trace metal basis) are the raw materials for the growth of gallium selenide (GaSe) single crystals by the chemical vapor transport method, in which iodine is the transport agent. Subsequently, GaSe nanoflakes are exfoliated from the grown bulk GaSe crystals by mechanical exfoliation. The n-Si/p-GaSe van der Waals vertical heterojunctions have been designed and fabricated for photodetection, which show good characteristics including a high responsivity of 1.74 A/W and a fast response/recovery time of 48 μs/88 μs under zero bias owing to their type-II band structure and built-in electric field. The results indicate that n-Si/p-GaSe vdW vertical heterojunctions are promising candidates in future ultrafast optoelectronic devices.

Structural, optical and Judd-Offelt intensity parameters of samarium doped with zinc tellurite glasses

ObjectiveThe current challenges in materials science and technology is to modify the optical response of rare-earth-doped inorganic glasses for optical applications. The main objectives of the present study are to identify the effect of samarium oxide concentration on the linear optical properties of the zinc tellurite glass system and to use the Judd–Ofelt analysis to study the compositional dependence of the optical properties of the synthesized glasses. MehodologyZinc tellurite glasses [(TeO2)0.7 (ZnO) 0.3]1−x [Sm2O3NPs] x, with x = 0.01, 0.02, 0.03, 0.04 and 0.05 molar fraction are prepared by melt quenching technique. The glass samples were produced by employing high-purity analytical chemicals of TeO2 (Alfa Aesar 99.99 per cent), ZnO (Alfa Aesar 99.99 per cent) and Sm2O3 NPs (Alfa Aesar 99.99 per cent). The density of the glass samples was determined based on Archimedes principles with distilled water as an immersed liquid. The density measurement was taken at 10 different times and the average value was recorded. ResultsDensimeter, Fourier transform infrared (FTIR) and X-ray diffraction (XRD) were used to study the physical and structural properties. The density and molar volume increases from 5.10 to 5.32 g/cm3 and 27.06–27.54 cm3/mol with an increase in Sm2O3 NPs concentrations. The XRD revealed that the glasses are amorphous. FTIR spectrum reflects the TeO4 structural unit stretching mode. The UV-Vis absorption spectra have seven absorption peaks from the ground state 6H5/2 to 4F7/2, 4I9/2, 6F11/2, 6F9/2, 6F7/2,6F5/2, and 6F3/2 excited energy levels of Sm3+ NPs. The emission spectra under 404 nm wavelength comprised of four bands at 566 nm, 604 nm, 647 nm, and 710 nm represented as 4G5/2→6H5/2, 6H7/2, 6H9/2, and 6H11/2 transitions. The presence of Sm2O3 NPs was confirmed by high-resolution electron microscopy transmission (HR-TEM) with a particle size of 72.43 nm. Judd-Offelt parameters (Ω2= 4.94, Ω4=4.38 and Ω6=3.38) were obtained from the least square fitting and the results revealed that the glasses have potential for laser application.

Nanoporous Vesicular Membranes of Amphiphilic Polymers Containing Trans / Cis Isomers

Nanoporous Vesicular Membranes of Amphiphilic Polymers Containing <i>Trans</i> / <i>Cis</i> Isomers