Mineralogical Evolution of Di- and Trioctahedral Smectites in Highly Alkaline Environments

2015 ◽  
Vol 63 (6) ◽  
pp. 414-431 ◽  
Author(s):  
Kerstin Elert ◽  
Eduardo Sebastián Pardo ◽  
Carlos Rodriguez-Navarro
Keyword(s):  
Alkaline Environments ◽  
Trioctahedral Smectites

Controlled Growth of the Non-centrosymmetric Zn(3-ptz)2 and Zn(Oh)(3-ptz) Metal-organic Frameworks

2019 ◽  
Author(s):  
javier enriquez ◽  
Ignacio Chi-Duran ◽  
Carolina Manquian ◽  
Felipe Herrera ◽  
Ruben Fritz ◽  
...  
Keyword(s):  
Single Crystal ◽  
Nonlinear Optical ◽  
Metal Organic Frameworks ◽  
Molar Ratio ◽  
Thermal Synthesis ◽  
Small Crystals ◽  
Alkaline Environments ◽  
Potential Applications ◽  
Metal Organic ◽  
Long Rod

Non-centrosymmetric single-crystal metal-organic frameworks (MOF) are promising candidates for phase-matched nonlinear optical communication, but typical hydrothermal synthesis produces small crystals with relatively low transmittance and poor phase matching. We study the effect of the metal-to-ligand molar ratio and reaction pH on the hydro-thermal synthesis of the non-centrosymmetric Zn(3-ptz)<sub>2</sub> and Zn(OH)(3-ptz) MOFs with <i>in-situ </i>ligand formation. In acidic environments, we find that decreasing the amount of ligand below the stoichiometric molar ratio 1:2 also produces highly transparent single-crystal octahedrons of <b>Zn(3-ptz)<sub>2</sub></b>. In alkaline environments, we obtain long rod-like <b>Zn(OH)(3-ptz) </b>crystals whose length exceeds previous reports by up to four orders of magnitude. Potential applications of these results in the development of MOF-based nonlinear optical devices are discussed.

scholarly journals Development of TLC Chromatographic-Densitometric Procedure for Qualitative and Quantitative Analysis of Ceftobiprole

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 708
Author(s):  
Żaneta Binert-Kusztal ◽  
Małgorzata Starek ◽  
Joanna Żandarek ◽  
Monika Dąbrowska
Keyword(s):  
High Sensitivity ◽  
Biologically Active ◽  
Fifth Generation ◽  
Ich Guidelines ◽  
Relative Standard ◽  
Lipophilicity Parameter ◽  
Alkaline Environments ◽  
Acetic Acid Water ◽  
Cephalosporin Antibiotics ◽  
The Stability

Currently, there is still a need for broad-spectrum antibiotics. The new cephalosporin antibiotics include, among others, ceftobiprole, a fifth-generation gram-positive cephalosporin, active against Staphylococcus aureus methicillin agonist (MRSA). The main focus of the work was to optimize the conditions of ceftobiprole qualitative determination and to validate the developed procedure according to ICH guidelines. As a result of the optimization process, HPTLC Cellulose chromatographic plates as a stationary phase and a mixture consisting of ethanol:2-propanol: glacial acetic acid: water (4:4:1:3, v/v/v/v) as a mobile phase were chosen. The densitometric detection was carried out at maximum absorbance of ceftobiprole (λ = 232 nm). Next, the validation process of the developed procedure was carried out. The relative standard deviation (RSD) for precision was less than 1.65%, which proves the high compatibility of the results, as well as the LOD = 0.0257 µg/spot and LOQ = 0.0779 µg/spot values, which also confirm the high sensitivity of the procedure. The usefulness of the developed method for the stability studies of ceftobiprole was analyzed. Study was carried out under stress conditions, i.e., acid and alkaline environments, exposure to radiation imitating sunlight and high temperature (40–60 °C). It was found that cefotbiprole is unstable in an alkaline environment and during exposure to UV-VIS radiation. Moreover, the lipophilicity parameter, as a main physicochemical property of the biologically active compound, was determined using experimental and computational methods.

scholarly journals Superhydrophobicity and Durability in Recyclable Polymers Coating

2021 ◽  
Vol 13 (15) ◽  
pp. 8244
Author(s):  
Francesca Cirisano ◽  
Michele Ferrari
Keyword(s):  
Thermal Treatment ◽  
Superhydrophobic Surface ◽  
Low Cost ◽  
Spray Coating ◽  
Large Area ◽  
Average Roughness ◽  
Water Contact ◽  
Alkaline Environments ◽  
Fine Control ◽  
Recycle And Reuse

Highly hydrophobic and superhydrophobic materials obtained from recycled polymers represent an interesting challenge to recycle and reuse advanced performance materials after their first life. In this article, we present a simple and low-cost method to fabricate a superhydrophobic surface by employing polytetrafluoroethylene (PTFE) powder in polystyrene (PS) dispersion. With respect to the literature, the superhydrophobic surface (SHS) was prepared by utilizing a spray- coating technique at room temperature, a glass substrate without any further modification or thermal treatment, and which can be applied onto a large area and on to any type of material with some degree of fine control over the wettability properties. The prepared surface showed superhydrophobic behavior with a water contact angle (CA) of 170°; furthermore, the coating was characterized with different techniques, such as a 3D confocal profilometer, to measure the average roughness of the coating, and scanning electron microscopy (SEM) to characterize the surface morphology. In addition, the durability of SH coating was investigated by a long-water impact test (raining test), thermal treatment at high temperature, an abrasion test, and in acidic and alkaline environments. The present study may suggest an easy and scalable method to produce SHS PS/PTFE films that may find implementation in various fields.

scholarly journals Mechanochemically Synthetized PAN-Based Co-N-Doped Carbon Materials as Electrocatalyst for Oxygen Evolution Reaction

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 290
Author(s):  
Paulette Gómez-López ◽  
José Ángel Salatti-Dorado ◽  
Daily Rodríguez-Padrón ◽  
Manuel Cano ◽  
Clemente G. Alvarado-Beltrán ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Photoelectron Spectroscopy ◽  
Carbon Nanomaterials ◽  
Carbon Materials ◽  
Catalytic Performance ◽  
X Ray Diffraction ◽  
New Class ◽  
Electrocatalytic Performance ◽  
Alkaline Environments ◽  
Metal Doped

We report a new class of polyacrylonitrile (PAN)-based Co-N-doped carbon materials that can act as suitable catalyst for oxygen evolution reactions (OER). Different Co loadings were mechanochemically added into post-consumed PAN fibers. Subsequently, the samples were treated at 300 °C under air (PAN-A) or nitrogen (PAN-N) atmosphere to promote simultaneously the Co3O4 species and PAN cyclization. The resulting electrocatalysts were fully characterized and analyzed by X-ray diffraction (XRD) and photoelectron spectroscopy (XPS), transmission (TEM) and scanning electron (SEM) microscopies, as well as nitrogen porosimetry. The catalytic performance of the Co-N-doped carbon nanomaterials were tested for OER in alkaline environments. Cobalt-doped PAN-A samples showed worse OER electrocatalytic performance than their homologous PAN-N ones. The PAN-N/3% Co catalyst exhibited the lowest OER overpotential (460 mV) among all the Co-N-doped carbon nanocomposites, reaching 10 mA/cm2. This work provides in-depth insights on the electrocatalytic performance of metal-doped carbon nanomaterials for OER.

Solubilization of Cs and K from Tetraphenylborate Precipitates in Highly Alkaline Environments

2018 ◽  
Vol 22 (1) ◽  
pp. 04017021 ◽  
Author(s):  
Aaron Barkatt ◽  
Wing Kot ◽  
Mohammad Adel Hadadi ◽  
Danika A. Coaplin ◽  
Jaclyn M. Connor ◽  
...  
Keyword(s):  
Alkaline Environments

Solvent-mediated crystalline phases of NixSy anchored on rGO sheets as electrocatalysts for hydrogen evolution application

2019 ◽  
Vol 12 (01) ◽  
pp. 1850089
Author(s):  
Hou Lin Yu ◽  
Wenliang Shi ◽  
Shuaishuai Li ◽  
Junma Zhang ◽  
Xiaobo Zhang ◽  
...  
Keyword(s):  
Ethylene Glycol ◽  
Hydrogen Evolution ◽  
Hydrothermal Process ◽  
Volume Ratio ◽  
Decisive Role ◽  
Catalytic Performance ◽  
Deionized Water ◽  
Alkaline Media ◽  
One Pot ◽  
Alkaline Environments

A facile, one-pot solvent-mediated hydrothermal process was adopted to prepare nickel sulfide nanoparticles decorated on reduced graphene oxide (NixSy/rGO) as electrocatalysts for hydrogen evolution reaction (HER). The designed solvent (ethylene glycol and deionized water) played a decisive role in controlling both crystalline phase and morphology of NixSy/rGO composites, leading to pure [Formula: see text]-NiS nanoparticles uniformly distributed on rGO sheets under suitable volume ratio of ethylene glycol and deionized water (2:1). The optimized [Formula: see text]-NiS/rGO showed prominent HER catalytic performance with a rather small Tafel slope of 93[Formula: see text]mV/decade and prominent current density of 10[Formula: see text]mA/cm2 at the overpotential of 177[Formula: see text]mV in alkaline environments when compared to pristine [Formula: see text]-NiS and NiS2/rGO catalysts. The excellent catalytic performance and long-term durability even after 8000 cycles confirmed the potential of [Formula: see text]-NiS/rGO composites as efficient electrocatalysts for HER in the alkaline media.

scholarly journals Electrocatalysis of the HER in acid and alkaline media

2013 ◽  
Vol 78 (12) ◽  
pp. 2007-2015 ◽  
Author(s):  
Nemanja Danilovic ◽  
Ram Subbaraman ◽  
Dusan Strmcnik ◽  
Vojislav Stamenkovic ◽  
Nenad Markovic
Keyword(s):  
Catalytic Decomposition ◽  
Alkaline Media ◽  
Alkaline Solutions ◽  
Water Molecules ◽  
Bifunctional Catalysts ◽  
High Coverage ◽  
Acidic Solutions ◽  
Noble Metal Catalysts ◽  
Alkaline Environments ◽  
Decomposition Of Water

Trends in the HER are studied on selected metals (M= Cu, Ag, Au, Pt, Ru, Ir, Ti) in acid and alkaline environments. We found that with the exception of Pt, Ir and Au, due to high coverage by spectator species on non-noble metal catalysts, experimentally established positions of Cu , Ag, Ru and Ti in the observed volcano relations are still uncertain. We also found that while in acidic solutions the M-Hupd binding energy most likely is controlling the activity trends, the trends in activity in alkaline solutions are controlled by a delicate balance between two descriptors: the M-Had interaction as well as the energetics required to dissociate water molecules. The importance of the second descriptor is confirmed by introducing bifunctional catalysts such as M modified by Ni(OH); e.g. while the latter serves to enhance catalytic decomposition of water, the metal sites are required for collecting and recombining the produced hydrogen intermediates.

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