Basic Aqueous Media Research Articles

Morphological and chemical dynamics upon electrochemical cyclic sodiation of electrochromic tungsten oxide coatings extracted by in situ ellipsometry.

The sodiation-desodiation process of sputtered amorphous electrochromic tungsten oxide coatings in an aqueous-based medium was simultaneously monitored over 99 cycles by cyclic voltammetry and in situ spectroscopic ellipsometry. This allowed extracting the evolution of optical and geometrical parameters upon cycling. The resulting electrochemical coloring-bleaching process was dynamically fitted in the 1.8-2.8 eV optical range with a four-phase model including a constrained spline parametrization of the dielectric function. This allows real time access to thickness, surface roughness, and dielectric function of ${{\rm Na}_x}\!{{\rm WO}_3}$NaxWO3. The temporal evolution of the latter in the fully colored state was used to highlight the porosity extent of the probed coating of opened morphology. The designed spectroelectrochemical approach was applied to map the temporal evolution of the $\rm Na$Na content (${x}$x in ${{\rm Na}_x}\!{{\rm WO}_3}$NaxWO3) during and between cycles, taking into account the intricate interplay between charge density, thickness, and electrolyte uptake.

Colorimetric detection of glyphosate: towards a handmade and portable analyzer

Abstract Glyphosate (GFT) is a widely used herbicide, considered toxic and a probable carcinogen. The main challenge is its detection, usually requiring expensive and laborious methodologies. Herein, we report a colorimetric detection of GFT, using a derivatization reaction with 2,4-dinitrofluorobenzene (DNFB) that leads to a yellow-colored product. This is undertaken under mild conditions (weakly basic aqueous medium and ambient conditions). A thorough kinetic study was carried out, showing that the derivatization reaction with GFT predominates over the hydrolysis of DNFB. Hence, the colorimetric product is the major product formed, which was fully characterized by nuclear magnetic resonance. Finally, a portable, handmade and cheap colorimeter was used to detect and quantify GFT, relying on the colorimetric reaction proposed. Simulating real contaminated samples, it was possible to analyze in just 10 min, with less than 7 % of error of the nominal concentration. Overall, a highly sustainable approach is shown for an herbicide monitoring, with a simple and mild derivatization reaction that does not require purification and leads to a colorimetric product. Moreover, a simple apparatus with low time analysis is proposed that uses a problematic electronic trash: cellphone chargers. This cheapens the process and allows field analysis that can be extended to other agrochemicals.

Novel Bi-heterocycles as Potent Inhibitors of Urease and Less Cytotoxic Agents: 3-({5-((2-Amino-1,3-thiazol-4-yl)methyl)-1,3,4-oxadiazol-2-yl}sulfanyl)-N-(un/substituted-phenyl)propanamides.

The synthesis of a novel series of bi-heterocyclic propanamides, 7a-l, was accomplished by S-substitution of 5-[(2-amino-1,3-thiazol-4-yl)methyl]-1,3,4-oxadiazol-2-thiol (3). The synthesis was initiated from ethyl 2-(2-amino-1,3-thiazol-4-yl)acetate (1) which was converted to corresponding hydrazide, 2, by hydrazine hydrate in methanol. The refluxing of hydrazide, 2, with carbon disulfide in basic medium, resulted in 5-[(2-amino-1,3-thiazol-4-yl)methyl]-1,3,4-oxadiazol-2-thiol (3). A series of electrophiles, 6a-l, was synthesized by stirring un/substituted anilines (4a-l) with 3-bromopropanoyl chloride (5) in a basic aqueous medium. Finally, the targeted compounds, 7a-l, were acquired by stirring 3 with newly synthesized electrophiles, 6a-l, in DMF using LiH as a base and an activator. The structures of these bi-heterocyclic propanamides were confirmed through spectroscopic techniques, such as IR, 1H-NMR, 13C-NMR, and EI-MS. These molecules were tested for their urease inhibitory potential, whereby, the whole series exhibited very promising activity against this enzyme. Their cytotoxic behavior was ascertained through hemolysis and it was observed that all these were less cytotoxic agents. The in-silico molecular docking analysis of these molecules was also in full agreement with their in-vitro enzyme inhibition data.

Synthesis, molecular docking, dynamic simulations, kinetic mechanism, cytotoxicity evaluation of N-(substituted-phenyl)-4-{(4-[(E)-3-phenyl-2-propenyl]-1-piperazinyl} butanamides as tyrosinase and melanin inhibitors: In vitro, in vivo and in silico approaches.

In the current research work, different N-(substituted-phenyl)-4-{(4-[(E)-3-phenyl-2-propenyl]-1-piperazinyl}butanamides have been synthesized according to the protocol described in scheme 1. The synthesis was initiated by reacting various substituted anilines (1a-e) with 4-chlorobutanoyl chloride (2) in aqueous basic medium to give various electrophiles, 4-chloro-N-(substituted-phenyl)butanamides (3a-e). These electrophiles were then coupled with 1-[(E)-3-phenyl-2-propenyl]piperazine (4) in polar aprotic medium to attain the targeted N-(substituted-phenyl)-4-{(4-[(E)-3-phenyl-2-propenyl]-1-piperazinyl}butanamides (5a-e). The structures of all derivatives were identified and characterized by proton-nuclear magnetic resonance (1H NMR), carbon-nuclear magnetic resonance (13C NMR) and Infra-Red (IR) spectral data along with CHN analysis. The in vitro inhibitory potential of these butanamides was evaluated against Mushroom tyrosinase, whereby all compounds were found to be biologically active. Among them, 5b exhibited highest inhibitory potential with IC50 value of 0.013±0.001µM. The same compound 5b was also assayed through in vivo approach, and it was explored that it significantly reduced the pigments in zebrafish. The in silico studies were also in agreement with aforesaid results. Moreover, these molecules were profiled for their cytotoxicity through hemolytic activity, and it was found that except 5e, all other compounds showed minimal toxicity. The compound 5a also exhibited comparable results. Hence, some of these compounds might be worthy candidates for the formulation and development of depigmentation drugs with minimum side effects.

Synthesis, 3D-structure and stability analyses of NRPa-308, a new promising anti-cancer agent

We report herein the synthesis of a newly described anti-cancer agent, NRPa-308. This compound antagonizes Neuropilin-1, a multi-partners transmembrane receptor overexpressed in numerous tumors, and thereby validated as promising target in oncology. The preparation of NRPa-308 proved challenging because of the orthogonality of the amide and sulphonamide bonds formation. Nevertheless, we succeeded a gram scale synthesis, according to an expeditious three steps route, without intermediate purification. This latter point is of utmost interest in reducing the ecologic impact and production costs in the perspective of further scale-up processes. The purity of NRPa-308 has been attested by means of conventional structural analyses and its crystallisation allowed a structural assessment by X-Ray diffraction. We also reported the remarkable chemical stability of this molecule in acidic, neutral and basic aqueous media. Eventually, we observed for the first time the accumulation of NRPa-308 in two types of human breast cancer cells MDA-MB231 and BT549.

In situ spectroelectrochemical ellipsometry using super continuum white laser: Study of the anodization of magnesium alloy

This work shows the interest to use a real time, white laser-based ellipsometer to characterize a complex electrolyte|electrode interface during an electrochemical process in an aqueous-based medium. This method is proposed to probe electrochemical interfaces that are usually not suitable to the full extent application of ellipsometry due to great disturbance of the reflected light flux provoked by gas evolution or roughness. In situ spectroelectrochemical ellipsometry combining such a visible super continuum fiber laser-band source was not previously reported to the best of the authors’ knowledge. The setup was employed to monitor an electrochemical process whose mechanism was previously incompletely described: the prespark anodization regime of the plasma electrolytic oxidation process of the Mg alloy AZ91D in the 3M KOH electrolyte. Above the anodization voltage of 4 V, the side water oxidation reaction induced light diffusion that reduces reflected light beam intensity. The process is monitored in an extended voltage range from 4 to 40 V and in an extended spectral range (495–800 nm). In the presented case, the use of a visible super continuum fiber laser-band source enhanced the signal-to-noise ratio giving access to a deeper picture of the triplex layer structure during surface repassivation by monitoring the evolution of the outer, inner, and interfacial layers.

Preparation and Photocatalytic Properties of CdS and ZnS Nanomaterials Derived from Metal Xanthate.

In this paper, we report a new, simple method for the synthesis of CdS and ZnS nanoparticles (NPs) prepared in a basic aqueous medium using metal xanthate as the sulfur source. The structure, morphology, size distribution, optical band gap, and photocatalytic properties of the newly obtained nanomaterials were investigated by UV-Vis spectroscopy, X-ray diffraction, and transmission electron microscopy. The results show that both CdS and ZnS crystallized in cubic phase and formed NPs with average sizes of 7.0 and 4.2 nm for CdS and ZnS, respectively. A blue shift of UV-Vis absorbance band and higher energy band gap values were observed for both materials in comparison with their bulk counterparts, which is in accordance with the quantum confinement effect. The as-prepared nanomaterials were tested in visible-light driven photocatalytic decomposition of methylene blue (MB). After irradiation for 180 min, the degradation rate of MB with a concentration of 8 × 10−6 mol/L mixed with a photocatalyst (CdS or ZnS, both 10 mg in 100 mL solution of MB) was found to be 72% and 61%, respectively. The CdS NPs showed better photocatalytic activity than ZnS, which could be explained by their lower energy band gap and thus the ability to absorb light more efficiently when activated by visible-light irradiation.

Development of a novel bio-based hybrid resin system for hygienic coating

A new water based organic-inorganic nano hybrid resin was synthesised through sol-gel technique by using alkoxysilane modified acrylic resin, silane monomer and chitosan as functional components. The uniqueness of this process is the incorporation of chitosan via in situ hydrolysis-condensation reaction of silane modified acrylic resin and methyl triethoxy silane in aqueous basic medium. The formation of nano silica and their bonding with chitosan in acrylic matrix has been confirmed by spectroscopic and SEM analysis. The coating based on such hybrid polymer exhibited excellent antibacterial activity, hydrophobicity and formaldehyde absorption ability. Such innovative bio-based resin has potential for application in hygienic interior decorative coating.

Synthesis and structure-activity relationship of 1-[(E)-3-phenyl-2-propenyl] piperazine derivatives as suitable antibacterial agents with mild hemolysis

A new series of 1-[(E)-3-phenyl-2-propenyl]piperazine derivatives (5a-m) as antibacterial agents was designed and synthesized. The synthetic strategy was initiated by coupling different anilines (1a-m) with bromoacetyl bromide (2) in aqueous basic medium to acquire different electrophiles, 3a-m, with good yields. These electrophiles were further reacted with 1-[(E)-3-phenyl-2-propenyl]piperazine (4) to yield the desired compounds, N-(substituted)-2-{4-[(E)-3-phenyl-2-propenyl]-1-perazinyl}acetamides (5a-m). The structures of these compounds were established from their IR, 1H-NMR, 13C-NMR, EI-MS and CHN analysis data. The bacterial biofilm inhibitory potential of these piperazine derivatives was tested against two pathogenic strains, Bacillus subtilus and Escherichia coli. Two compounds, 5d and 5h were identified as suitable antibacterial agents. The cytotoxicity of these molecules was profiled through hemolytic assay and it was inferred that all the compounds were nearly harmless for membrane of red blood cells.

Contalactone, a contaminant formed during chemical synthesis of the strigolactone reference GR24 is also a strigolactone mimic

Strigolactone (SL) plant hormones control plant architecture and are key players in both symbiotic and parasitic interactions. GR24, a synthetic SL analog, is the worldwide reference compound used in all bioassays for investigating the role of SLs in plant development and in rhizospheric interactions. In 2012, the first characterization of the SL receptor reported the detection of an unknown compound after incubation of GR24 samples with the SL receptor. We reveal here the origin of this compound (P270), which comes from a by-product formed during GR24 chemical synthesis. We present the identification of this by-product, named contalactone. A proposed chemical pathway for its formation is provided as well as an evaluation of its bioactivity on pea, Arabidopsis, root parasitic plant seeds and AM fungi, characterizing it as a SL mimic. Quality of GR24 samples can be easily checked by carrying out microscale hydrolysis in a basic aqueous medium to easily detect P270 as indicator of the presence of the contalactone impurity. In all cases, before being used for bioassays, GR24 must be careful purified by preparative HPLC.

Effect of Carbon Support on Fe-N3/C Model Active Site for the Oxygen Reduction Reaction

Non-precious metal catalysts for the oxygen reduction reaction (ORR) are of great interest for fuel cell technology due to their low cost and wide availability of materials. Development of these catalysts has been a constantly growing area. However, there have been very few literature reports that provide insights into the precise nature of the structure and geometry of the catalytically active sites formed in these materials. In the current literature, the most commonly proposed catalytically active site(s) for ORR corresponds to Fe-N2+2/C geometry. This is typically produced through a high temperature pyrolysis step to obtain this desired configuration in the active sites[1]. However, the pyrolysis step is very disadvantageous due to the production of a distribution of nitrogen functional groups on the surface which can negatively affect the activity of the catalyst, since only nitrogen functionalities with specified geometry are considered to be the most active for ORR[2,3]. As well, high temperature treatments increase the cost of production, and can be quite energy demanding. Thus, high-temperature treatment makes it difficult to design a surface rich in a specific active site for the desired application. The work presented here demonstrates a model system for a non-precious metal catalyst for the ORR achieved by covalently functionalizing a conventional carbon support with a nitrogen-rich ligand. The terpyridine ligand geometry allows the formation of well-defined active catalytic sites when covalently attaching an N3/C functionality to the carbon surface, leaving exposed the most active sites for the ORR. Room temperature metal-ligand coordination with Fe results in desired Fe-N3/C moieties on the surface. We demonstrate that this system can be prepared using mild reaction conditions and does not require high temperature treatment for improved activity, in fact heat treatment to this system was detrimental to the activity. The Fe-N3/C support was subjected to electrochemical studies in both acidic and basic aqueous media and demonstrates the potential of this system to be used as a model for an Fe-N3/C active site for ORR.

Investigation of the chemical stability of Zn2SnO4 in aqueous media by using ICP-OES and TEM analyses

Zn2SnO4 (ZTO) is an important electroceramic material having unique optical and electrical properties. For some applications, ZTO has to be used in an aqueous media under various conditions; however, there is still limited understanding about the relationship between particle characteristics and chemical stability in aqueous media. Therefore, in this study, chemical stability of solid state (S-ZTO) and hydrothermally synthesized (H-ZTO) powders was investigated under different conditions; pH, time and particle characteristics as well as dye-sensitized solar cell conditions. Analyses revealed that the acidic media resulted with higher dissolution rate of Zn2+ and Sn4+ ions compared with the basic media. H-ZTO is more stable with respect to S-ZTO particles due to less defect concentration. Zn2+ ions dissolve via proton promoted dissolution mechanism in acidic media. Moreover, cationic field strength of the ions in ZTO results in differential dissolution of Sn4+ and Zn2+ ions, which were determined as maximum 0.04% and 0.4%, respectively. TEM studies revealed that no interaction layer found at the surface of particles, thus ZTO powders are chemically stable. Physical and electrical properties of aged ZTO powders prove that ZTO material can be used in different applications which involve acidic or basic aqueous media.

Bimetallic AuCu nanoparticles supported on CeO2 as selective catalysts for glycerol conversion to lactic acid in aqueous basic medium

Gold-based catalysts, monometallic Au/CeO2 or bimetallic AuCu/CeO2, evaluated on the glycerol conversion to lactic acid, demonstrated to be active and selective at a reaction temperature of 220 °C in aqueous basic medium at low base concentration. The concentration of NaOH slightly modified the activity of AuCu/CeO2 for converting glycerol, while selectivity toward lactic acid increased on AuCu/CeO2 catalyst but had no influence on Au/CeO2 catalytic performance. Recyclability tests demonstrated that AuCu/CeO2 kept high conversion for up to the fourth catalytic cycle and selectivity remained stable, while conversion on Au/CeO2 significantly decreased in the second cycle. For instance, copper stabilized gold on AuCu/CeO2 catalysts for converting glycerol to lactic acid in aqueous medium at relatively high temperature of 220 °C. Characterization of AuCu/CeO2 catalyst using H2-TPR showed that the presence of Au modified the reduction events of Cu species, while HRTEM analysis of nanoparticles showed particles of an average size of 6.3 nm and lattice fringes for metallic Au and Cu. These results suggest that Au and Cu might be in close proximity.

Conversion of skin collagen fibrous material waste to an oil sorbent with pH-responsive switchable wettability for high-efficiency separation of oil/water emulsions

Collagen fibrous material waste is an undervalued sustainable resource with many potential applications. Herein, a three-dimensional collagen fiber matrix (CFM), derived from skin collagen fiber waste generated in the leather industry, was modified by pH-responsive copolymer P(MAA-co-GMA) terminated with dodecyl hydrocarbon chains via an in situ free radical polymerization. The functionalized CFM possesses an appropriate porous structure, and shows switchable hydrophobicity/hydrophilicity for different pH values. It displayed high separation efficiency (∼99.93 ± 0.03%) for separating surfactant-free oil-in-water emulsion (10 cycles) as well as surfactant-stabilized oil-in-water emulsion (3 cycles). More importantly, the functionalized CFM displayed excellent self-cleaning performance. In other words, the absorbed oil was released after treatment in basic aqueous medium. The attractive properties of the functionalized smart collagen fiber matrix make it an excellent prospect for potential application in oily emulsion treatment from the reusable resource and environmentally friendly perspectives.

Efficient, one-step, cascade synthesis of densely functionalized furans from unprotected carbohydrates in basic aqueous media

One-pot Et3N-catalyzed reaction of unprotected carbohydrates with malononitrile or malonamide nitrile in aqueous media gave selectively densely functionalized furans in 84–98% yields.

Ozonation of pentabromophenol in aqueous basic medium: Kinetics, pathways, mechanism, dimerization and toxicity assessment

Ozonation has been identified effective technique to degrade phenolic compounds, and production of intermediate dimers are major threat. In this study, we systematically investigated the degradation of Pentabromophenol (PBP) in an aqueous medium by using two different ozone generators (sources: air and water). We studied various factors that influenced the degradation kinetics of PBP, including the pH (7.0, 8.0, and 9.0), humic acid (HA) and anions (Cl−, SO42−, NO3−, and HCO3−). PBP was efficiently degraded within 5 min (O3 source: water) and 45 min (O3 source: air) at pH 8.0 maintained by phosphate buffer. Reaction kinetics revealed 17 b y-products with five possible pathways, including dimers with their isomers and lower bromophenols. Furthermore, the frontier molecular orbital theory was employed to confirm the proposed ozonation pathways, including the breakage of the CO bond at C5 and C4 positions, and the cleavage of the CC bond at C3 and C6 position. Product P5, P14 (hydroxyl-nonabromophenyl ether) and P15 (dihydroxyl-octabromophenyl ether) were identified with isomers. Ecological Structure Activity Relationships toxicity assessment resulted into the conversion of highly toxic PBP (acute toxicity: LC50 = 0.11 mg L−1 for fish, LC50 = 0.124 mg L−1 for daphnia, and EC50 = 0.118 mg L−1 for green algae) to less harmful products aside from dimers. P14 (acute toxicity: LC50 = 1.04 × 105) found to be more toxic as compare to PBP. From these findings, we concluded that ozonation is an effective and ideal process for PBP degradation.

Dissolution of sodium silicate glasses for the production of water glass – Part II: Dependence of corrosion process on pH in basic aqueous media

Dissolution of sodium silicate glasses for the production of water glass – Part II: Dependence of corrosion process on pH in basic aqueous media

Sustainable and Degradable Epoxy Resins from Trehalose, Cyclodextrin, and Soybean Oil Yield Tunable Mechanical Performance and Cell Adhesion

Natural product feedstocks such as carbohydrates and vegetable oils offer tremendous potential for creating sustainable cross-linked epoxy resin thermosets for numerous applications. Herein, we designed and synthesized trehalose- and β-cyclodextrin-based carboxylic acid hardeners to cure with epoxidized soybean oil forming predominantly sustainable epoxy resins. Trehalose (Tr) and β-cyclodextrin (Cd) were functionalized with heptanoyl chloride (H) and succinic anhydride (S). The resulting carboxylic acid hardeners were homogeneously formulated and cross-linked with epoxidized soy bean oil (ESO) at three different COOH/epoxide ratios. The cured resins were thermally stable up to 300 °C and stable in neutral and acidic aqueous conditions. Yet, degradation into water-soluble components could be triggered upon exposure to basic aqueous media. The physical properties of these materials are tunable based on feedstock composition and identity of the carbohydrate hardener. The glass transition temperatures (Tg) o...

Electrochemical Intercalation of AP-CVD Grown Few-Layer and Multi-Layer Graphene

First studies on intercalation of graphite date back to the first half of the XX century. At first, the ability of graphite to spontaneously form intercalation compound (GIC) by the soaking in strong acids was studied. Only later, GIC were obtained by electrochemical route, highlighting the mechanism of formation of GIC in extremely ordered layered structure as HOPG [1,2]. Anodic electrochemical intercalation is typically performed in acidic aqueous solution, forming GIC by the insertion of anions as ClO4-, HSO4- and NO3- [3]. Anodic electrochemical intercalation is nowadays useful to obtain high quality Graphene Oxide (GO) thorough an easy and green route [4]. Studies on the formation of GIC by cathodic polarization opened to the understanding and exploitation of the reversible intercalation of alkali ions (Li+, Na+) that found the suitable application in Li battery technology [5]. However, up to now, studies have concentrated mainly on the electrochemical formation of GIC HOPG, but very few have investigated the GIC formation in nanoscaled graphitic material as graphene [6]. In this work, we provide a comprehensive understanding of the GIC formation by electrochemical route in few-layer graphene grown through atmospheric pressure chemical vapor deposition (ACVD) on metallic substrates. Anodic electrochemical intercalation of few layer graphene in acidic, organic-based and aqueous-based media has been investigated. A deeper understanding of intercalation and doping phenomena of few layer graphene has been performed in situ through Raman spectroscopy measurements. Preliminary results on cathodic intercalation of few layer graphene in aqueous and organic media will be also discussed.

Effect of ionic strength on solution and drilling fluid properties of ionic polysaccharides: A comparative study between Na-carboxymethylcellulose and Na-kappa-carrageenan responses

Natural polymers are widely used in different industries, mainly due to their hydrophilic features, which make it possible to solubilize them in water or absorb a large amount of it. Polysaccharides are the most widely used hydrophilic polymers, mainly because of their non-toxicity, biodegradability, compliance with environmental regulations and thickening behaviour in water. Knowledge of polymer performance in different aqueous media is essential to ensure optimal use in a desired application. In this study, the stability of sodium kappa-carrageenan and sodium carboxymethylcellulose stability was investigated in saline and basic aqueous media, as well as their applicability in drilling fluids. The ionic strength effects of the aqueous media containing Na+, Mg2+ and Ca2+ on the rheological properties of the polymer solutions were evaluated by varying the salt concentration, pH and temperature. The rheological properties and drilling fluid filtrate volume were evaluated by varying salt concentration and pH. The kappa-carrageenan solutions and drilling fluids were scarcely influenced by ion addition, at pH 7 to 10, even at higher salt concentrations, but highly influenced at pH > 11. On the other hand, carboxymethylcellulose solutions and their drilling fluids were more affected by the presence of salt and pH changes, with a greater decline in viscosity and increase in filtrate volume. This behaviour was interpreted as conformation adopted by the kappa-carrageenan chains in the presence of ions, indicating that this polymer is a good candidate for drilling fluids in oil well operations.