Presence Of Quaternary Ammonium Salts Research Articles

Injectable exosome-loaded quaternized chitosan/oxidized sodium alginate hydrogel with self-healing, bioadhesive, and antibacterial properties for treating combined radiation-wound injury

The management of combined radiation-wound injury (CRWI) is a major clinical challenge owing to the delayed and prolonged wound-healing process. Moreover, the mechanisms underlying the healing of CRWI are complex, and chronic wounds can increase vulnerability to multidrug-resistant bacterial infections, vascular disease, and other adverse conditions. Although exosomes from iPSC-derived mesenchymal stem cells (iMSCs) can promote injury repair, the feasibility of encapsulating them within polysaccharide-based hydrogels to treat CRWI remains to be explored. Here, iMSC-derived exosomes were encapsulated within an injectable hydrogel (HACC/OSA) consisting of quaternized chitosan (HACC) and oxidized sodium alginate (OSA). The HACC/OSA hydrogel exhibited good self-healing properties, excellent injectability, and good biocompatibility. In mouse models of CRWI, the HACC/OSA hydrogel could form a protective barrier covering the wound. Due to the presence of quaternary ammonium salts, the hydrogel could provide long-term antimicrobial protection to the wound, which was favorable for wound healing. In addition, the hydrogel could also promote CRWI repair by stabilizing exosome release. The exosome-loaded hydrogel (HACC/OSA@Exos) significantly inhibited bacterial growth and promoted the repair of CRWI, as indicated by enhanced wound healing efficiency, rapid re-epithelialization, favorable collagen deposition, and abundant angiogenesis at the wound site. Together, the in vivo and in vitro results indicated that the exosome-loaded polysaccharide-based hydrogel (HACC/OSA@Exos) can promote the healing of CRWI and potentially serve as a valuable clinical agent for CRWI management.

Zinc Anodes with Electrodeposited Ionomer Protection Layer for Rechargeable Zinc-Air Batteries

Metal air batteries are assembled from a metal anode and a porous cathode in a suitable electrolyte. They combine the design of fuel cells and conventional batteries and have been demonstrated to have large theoretical energy densities higher compared to devices based on Li-ion chemistry, due to the ability to use air at the cathode and to exchange two electrons per zinc atom. ZAB represent a safe, environmentally benign, affordable and simple way to store and deliver electrical energy for a wide variety of devices. However, research efforts are necessary to increase the efficiency of rechargeable ZAB and mitigate obnoxious occurrences that decrease the number of charge-discharge cycles such as zinc dendrite formation, cathode degradation and alkaline electrolyte carbonation.The protection of zinc metal anodes in zinc-air batteries (ZAB) is an efficient way to reduce corrosion and Zn dendrite formation and improve cyclability and overall battery efficiency. The extent of improvement depends on the type and thickness of the protective layer.In this work, we explore an advanced coating of the zinc anode by anion-conducting poly(N-vinylbenzyl, N,N,N trimethylammonium) chloride (PVBTMA) that is electropolymerized directly on the zinc metal. The Zn deposition in presence of quaternary ammonium salts and polyelectrolytes was recently studied to improve the cyclability. The major advances foreseen by this approach are excellent qualities of the metal/ionomer interface, due to the in-situ deposition process, improving the corrosion protection and the selective anion permeability; furthermore, the chosen ionomer presents a high stiffness and strength to resist the formation of zinc dendrites, due to the stiff polystyrene backbone. Moreover, the presence of a polyelectrolyte separator facilitates device miniaturization. The zinc anode protection layer was observed by optical microscopy and scanning electron microscopy (Figure : SEM micrographs of Zn pellet with PVBTMA layer: a) from 0.01 M precursor solution, b) and c) from 0.1 M precursor solution) .and the wettability of the ionomer-coated zinc surface was investigated by contact angle measurements.The resulting ZAB battery with PVBTMA anode coating is analyzed in terms of cyclability in alkaline electrolyte and solid-state configuration using a Whatman paper separator.The goal is to pair metal-free electrode materials with appreciable catalytic activity for oxygen reduction and evolution with a zinc anode that has a protection layer against dendrite formation to maximize efficiency. Figure 1

Cover Feature: Electrochemical Cycling Behaviour and Shape Changes of Zn Electrodes in Mildly Acidic Aqueous Electrolytes Containing Quaternary Ammonium Salts (ChemElectroChem 12/2023)

The Cover Feature shows a schematic representation of Zn plating from an aqueous electrolyte in the presence of Quaternary Ammonium Salts (QASs) (upper part) and in an additive-free solution (bottom element). The study provides insight into the cycling behavior of zinc anodes in battery context, using QASs as additives in mildly acidic aqueous electrolytes. The cover was designed by one of the paper authors: Elisa Emanuele. More information can be found in the Research Article by B. Bozzini et al.

Characterization of benzopyrylium monomethine dyes as fluorescent probes for sensing and imaging of nucleic acids

In this study, a series of benzopyrylium monomethine dyes bearing a benzothiazole moiety and mainly differing in their substitution pattern were characterized regarding their ability for nucleic acid binding and their use as fluorescent probes for sensing and imaging of nucleic acids. Dyes were characterized with special focus on structure and substituent effects on dye binding towards nucleic acids. Absorption maxima of the free, unbound dyes ranged from 474 to 498 nm. Fluorescence intensities of the unbound dyes were extremely low with emission maxima in the range of 512 to 584 nm depending on the polarity of the used solvent. Quantum yields of the free dyes were below 1 %. Upon binding to nucleic acids, however, dyes became highly fluorescent. Dyes with sterically demanding 2-di- or -triamino substituents exhibited a significant enhancement of the fluorescence quantum yield in presence of nucleic acids. The formation of stable dye-nucleic acid complexes was confirmed by time- and spectrally-resolved fluorescence measurements using a streak camera-based setup. Dye complexation was associated with prolonged lifetimes. All dyes were cell permeable and able to stain nucleic acids present in nuclear structures in living as well as in fixed cells. Colocalization analysis with nuclear specific reporters revealed that all dyes bind selectively to nucleic acids, which confirms their applicability as highly specific fluorescent probes for sensing nucleic acids and cell nuclei imaging. In comparison to commercially available nucleic acid stains, the investigated dyes displayed superior staining properties with high cell viability and less cytoplasmic enrichment. In conclusion, the results obtained by different complementary methods demonstrate that studied dyes are useful fluorescent probes for sensing and imaging of nucleic acids in-vitro, in fixed as well as in living cells. Bulkier dye substituents like piperazinyl and the presence of quaternary ammonium salts in the 2-amino side chain enhance nucleic acid binding significantly, thereby making the parent dye structure attractive for sensing applications and ongoing studies of structure–function relationship of nucleic acid stains.

Novel Antireflection Coatings Obtained by Low-Temperature Annealing in the Presence of Tetrabutylammonium Bromide and Gold Nanoparticles.

In this work, nanoporous antireflective coatings on silicate glass were obtained from silicon dioxide sol compositions by the sol-gel method in the presence of quaternary ammonium salt (tetrabutylammonium bromide) at different annealing temperatures (200-250 °C). Varying the salt concentration from 3 to 5 wt.%, we achieved the transmittance of the coatings of about 97% at 250 °C in comparison with 91% for clean glass in the wavelength range from 400 to 1100 nm. The addition of gold nanoparticles to the composition containing 5 wt.% tetrabutylammonium bromide allowed us to decrease the annealing temperature to 200 °C, preserving the transmittance at the level of 96.5%. For this case, the optimal concentration of gold nanoparticles is determined (2.6 × 10-9 mol/mL). According to the SEM analysis, the obtained antireflective coatings contain pores with a minimum area size up to 4 nm2.

Tailored texture synthesized LDH catalysts in the presence of quaternary ammonium salts

Tetramethylammonium- and tetrabutylammonium-hydroxides operate as alternative bases to the traditional inorganic ones for the LDH structures synthesis with controlled texture. This is valuable for both co-precipitation and mechano-chemical routes, where these organic bases limited the production of wastewaters by more than ten times, the contamination of hydrotalcites with other metallic cations, an important decrease of the energy consumed in the synthesis and, also as a template for generating predetermined porosity. The crystallinity of the produced LDH is influenced by the nature of the alkyl ammonium cation. The catalytic behavior of the catalysts has been evaluated in the cyanoethylation, Claisen-Schmidt and self-cyclohexanone condensation.

Engineering Highly Fluorescent and Colloidally Stable Blue-Emitting CsPbBr3 Nanoplatelets Using Polysalt/PbBr2 Ligands

Two-dimensional (2D) colloidal perovskite CsPbBr3 nanoplatelets (NPLs) have recently attracted attention as promising blue-emitting materials because of their large exciton binding energy and precisely controlled thickness. However, synthesizing NPLs that are homogeneous and highly fluorescent while exhibiting long-term stability has been challenging, which has limited the successful integration of such materials in optoelectronic devices (e.g., light-emitting devices). Herein, we introduce a strategy relying on surface ligand-engineering, using PbBr2-complexed polymers as coating ligands that impart morphological and colloidal stability while enhancing the photoluminescence quantum yield of perovskite NPLs. The polymers are salt-rich compounds that present several ammonium (or imidazolium) bromide anchoring groups and alkyl chains with different lengths as solubilizing blocks. The presence of quaternary ammonium salts facilitates the dissolution of PbBr2 in organic solutions, forming polysalt-[PbxBry]2x−y complexes. These complexes strongly interact with the NPLs and eliminate surface defects, compared to the as-grown materials, and improve their structural and morphological stability. This strategy has yielded high-quality blue-emitting NPLs that maintain color purity (with narrow profiles at ∼460 nm) with photoluminescence quantum yield (PLQY) up to 80%. Additionally, significantly enhanced long-term stability of the nanoplatelets under several challenging conditions, including UV irradiation and highly diluted conditions, has been achieved.

Precise synthesis of α,ω-chain-end functionalized poly(dimethylsiloxane) with azide groups based on metal-free ring-opening polymerization and a quantitative azidation reaction

We have so far developed a method for the controlled ring-opening polymerization of cyclotrisiloxane catalyzed by strong organobasic compounds to produce various chain-end functionalized polysiloxanes with controlled number-average molar mass (Mn) and narrow molar-mass dispersity (ÐM) values. In this study, well-defined α,ω-chain-end functionalized poly(dimethylsiloxane) with azide groups (N3-PDMS-N3) possessing a narrow ÐM range (ÐM = 1.04) and a relatively high Mn of up to 28.2 kg mol−1 was precisely synthesized in a mixed solvent of tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) in the presence of quaternary ammonium salts as catalysts; N3-PDMS-N3 was obtained by converting α,ω-chain-end functionalized PDMS with bromomethyl groups (Br-PDMS-Br), which was prepared by polymerizing hexamethylcyclotrisiloxane (D3), water, and 1,3-trimethylene-2-n-propylguanidine (TMnPG) as the monomer, the initiator, and the catalyst, respectively. It was necessary to choose proper solvents depending on the Mn of Br-PDMS-Br to achieve the complete conversion of the bromomethyl groups by the azidation reaction. Moreover, we demonstrate the model reaction of copper-catalyzed 1,3-dipolar cycloaddition between N3-PDMS-N3 and phenylacetylene. As a result, the cycloadducted compound was exclusively obtained while maintaining a low ÐM value of 1.06 by employing copper(I) bromide and triethylamine as the catalyst and the ligand, respectively. This system was also effective for a polymer-polymer coupling reaction. Indeed, we successfully synthesized an ABA-type triblock copolymer where A and B are polystyrene (PS) and PDMS segments by reacting N3-PDMS-N3 with ω-chain-end functionalized PS with an alkynyl group.

Organophilic clays and their application in atrazine adsorption

Atrazine’s adsorptive capabilities make the use of clays practical and effective. Three types of organophilic clays modified by cationic surfactants with the ability of one of these clays to adsorb atrazine in an aqueous medium are discussed in this work. The modification in clays was done with the surfactants cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and dodecyltrimethylammonium chloride. The X-ray diffraction data indicated different lamellar expansions for the three organophilic clays obtained when compared to in natura clay, proving the presence of quaternary ammonium salts in the interlamellar space. There was also a decrease in the specific surface area showing less accessibility to the lamellar spaces due to the presence of surfactants. The thermogravimetric analysis showed a negative variation profile in all the clays. The adsorption test showed a better capacity for atrazine adsorption in the organophilic clay of 64% when compared with 36% of in natura clay, and it followed the Freundlich isotherm model.

Biological activity of quaternary ammonium salts and resistance of microorganisms to these compounds.

Quaternary ammonium salts (QASs) are ubiquitous in nature, being found in organisms ranging from microorganisms to vertebrates (e.g., glycine betaine, carnitine) where they have important cellular functions. QASs are also obtained by chemical synthesis. These compounds, due to their diverse chemical structure (e.g. monomeric QAS or gemini) and their biological properties, are widely used in medicine (as disinfectants, drugs, and DNA carriers), industry, environmental protection and agriculture (as preservatives, biocides, herbicides and fungicides). Discussed chemical compounds reduce the adhesion of microorganisms to various biotic and abiotic surfaces and cause the eradication of biofilms produced by pathogenic microorganisms. The properties of these chemicals depend on their chemical structure (length of the alkyl chain, linker and counterion), which has a direct impact on the physicochemical and biological activity of these compounds. QASs by incorporation into the membranes, inhibit the activity of proteins (H+-ATPase) and disrupt the transport of substances to the cell. Moreover, in the presence of QASs, changes in lipid composition (qualitative and quantitative) of plasma membrane are observed. The widespread use of disinfectants in commercial products can induce resistance in microorganisms to these surfactants and even to antibiotics. In this article we discuss the biological activity of QASs as cationic surfactants against microorganisms and their resistance to these compounds.

Influence of salt addition on polymer-free electrospinning of cyclodextrin nanofibers

Solution conductivity is one of the critical parameters affecting the electrospinning of polymer solutions as the jet formation is directly related to the movement of an electrically charged polymer solution to a grounded target. Hence, the solution conductivity has been studied for the electrospinning of various polymeric systems, but not yet for the electrospinning of polymer-free systems. In this regard, this study investigates the influence of solution conductivity on the electrospinning of CD molecules (i.e., hydroxypropyl (HP) modified β and γ -CDs) at various concentrations in the presence of quaternary ammonium salt (i.e., tetraethylammonium bromide, TEAB) from aqueous solutions. The addition of TEAB significantly boosted the conductivity of the CD solutions. It could lead to smaller particles at low CD concentrations because of electrohydrodynamic spraying, while the transformation from beaded-fibers to bead-free fibers was observed with an increase in the CD concentration. The salt addition decreased the fiber diameter and resulted in thinner nanofibers. Likewise, the incorporation of NaCl –used as an alternative to TEAB- caused thinning of the fibers due to enhanced solution conductivity. On the other hand, at higher salt contents, the fiber morphology was worsened for both CDs, leadings to beads on the fibers. Overall, this paper, for the first time, investigates the effect of solution conductivity of the electrospinning of a polymer-free system (i.e., CD), and the experimental findings show that increasing the solution conductivity with salt addition causes significant changes on the electrospinnability and fiber properties.

Synthesis and Catalytic Activity of Quaternary Ammonium Salts Containing gem-Dichlorocyclopropane and 1,3-Dioxolane Fragments

Quaternary ammonium salts containing gem-dichlorocyclopropane and 1,3-dioxolane groups were synthesized in high yield. The reactions of dichlorocarbonation of styrene and O-alkylation of 2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane in the presence of quaternary ammonium salts were studied. It was established that in the O-alkylation reaction, compounds containing cycloacetal and allyl moieties have the maximum efficiency in the series of catalysts studied. The structures of the isolated salts were proved by 1H and 13C NMR spectroscopy.

Exploring the potential of group III salen complexes for the conversion of CO2 under ambient conditions

Monometallic and bimetallic scandium and yttrium-salen complexes were synthesized and applied for the first time as homogeneous Lewis acids for the cycloaddition of CO2 to epoxides in the presence of quaternary ammonium salts. The developed rare-earth-based complexes showed the ability to catalyze the coupling of CO2 and industrially attractive epoxides such as epichlorohydrin and propylene oxide into cyclic carbonates under ambient conditions using low metal loading and leading to turnover numbers (TON) over 100. Additionally, functionalized cyclic carbonates with potential for application in polymer synthesis were obtained under mild conditions (T = 40−60 °C) under atmospheric CO2 pressure. DFT calculations were carried out to gain insight into the reaction mechanism justifying the observed difference of activity between the different complexes and indicating milder reaction barriers for the yttrium and scandium-based salen species compared to a homologous chromium complex. Moreover, advanced buried volume calculations were performed to assess the accessibility of the catalytic pockets in monometallic salen complexes versus bimetallic salen complexes.

Catalytic Conversion of Biomass‐Derived Carbohydrates into Levulinic Acid Assisted by a Cationic Surface Active Agent

AbstractLevulinic acid (LA), a bio‐renewable chemical building block, has been produced in good isolated yields by treating biomass‐derived carbohydrates with aqueous hydrochloric acid in the presence of quaternary ammonium salts as cationic surface‐active agent (SAA). Under optimized conditions (120 °C, 3 h, 20.2% HCl), the one‐pot process afforded LA in 80% isolated yield from glucose using only 5.77 mol% (10 wt%) of benzyltributylammonium chloride (BTBAC) at the SAA. The control reaction (no BTBAC) provided LA in only 64% yield from glucose under identical conditions. The process was optimized on the reaction temperature, loading of BTBAC, and the concentration of HCl. The use of BTBAC led to a nearly 8–17% increase in yield of LA (compared to the control reaction) for all the carbohydrates studied.

Catalytic Effect of Photoluminescent Zinc Oxide Nanoparticles Formed in the Presence of Quaternary Ammonium Salts.

The comparative effect of two quaternary ammonium salts from 1,2-bis(4-pyridyl)ethane (PyQAs), namely N,N′-diphenacyl-1,2-bis(4-pyridinium)ethane dibromide (PyQAs1) and N,N′-di(p-methoxyphenacyl)-1,2-bis(4-pyridinium)ethane dibromide (PyQAs2), upon the size and photoluminescence of zinc oxide nanoparticles (ZnO NPs) was investigated. The formation of ZnO NPs took place in the presence of variable amounts of the two PyQAs species (1, 2.5, and 5%), according to the chemical precipitation of zinc(II) acetate with potassium hydroxide in ethanol under reflux. The obtained ZnO NPs were structurally characterized by means of X-ray powder diffraction, infrared, and Raman spectroscopy. The fluorescence of all supernatant solutions, observed under ultraviolet light, determined us to make an investigation of the solutions by means of liquid chromatography coupled with electrospray ionization mass spectrometry (LC-MS-ESI) in order to elucidate the identity of the newly formed fluorescent species. Such an occurrence thus allowed the invocation of the catalytic effect of zinc(II) ions towards the organic transformation of both nonfluorescent PyQAs surfactants into new fluorescent organic species.

β-Cyclodextrin/Quaternary Ammonium Salt as an Efficient Catalyst System for Chemical Fixation of CO2

The environmental friendly biomaterial β-cyclodextrin (β-CD) was used for the synthesis of cyclic carbonates from CO₂ with epoxides in the presence of quaternary ammonium salts as co-catalyst. The factors affecting the activity of this binary catalyst system, such as reaction temperature, time, CO₂ pressure and the mole ratio of reactants, were investigated systematically. The excellent yield of cyclic carbonate (100%) was obtained at 130 °C, 3 MPa after 5 h with the catalyst system of β-CD/tetrabutylammonium bromine (TBABr). The catalyst system of β-CD/TBABr can also be applied to a wide substrates of epoxides with good to excellent yield and high selectivity (>99%). Recyclable ability of β-CD/TBABr can also be detected and there was no significant decline in activity after five recycles. Finally, reaction mechanism was proposed based on the reaction results and literatures.

Synthesis and characterization of antibacterial bio-nano films for food packaging

This study prepared antibacterial nanocomposite films for food packaging from Montmorillonite, which was modified by quaternary ammonium salts such as cetyltrimethylammonium bromide (CT), hexadecyl-tributyl phosphonium bromide (HD) and corn starch (CS). After this, it determined the antimicrobial activity of CS nanofilms against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria. Dispersion of silicate layers and starch nanocomposite films was analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), and the results indicated that presence of quaternary ammonium salts enhanced clay dispersion, and the starch films incorporated with quaternary ammonium salts would provide potential use in food packaging as nanostructural materials. The nanofilms that were obtained based on the results of the antibacterial analysis were confirmed to have much stronger antibacterial properties than those in similar studies in the literature.

Critical transition of epoxy resin from brittleness to toughness by incorporating CO2-sourced cyclic carbonate

A five-membered cyclic carbonate as CO2-sourced monomer was prepared from ethylene glycol diglycidyl ether (EGDE) with CO2 by cycloaddition reaction, abbreviated as 5CC-EGDE, at 130 ℃ under 10 bar CO2 pressure in the presence of quaternary ammonium salt modified amberlyst (D296) for 20 h. The complete conversion and 98.6% selectivity were obtained, respectively. The incorporation of 5CC-EGDE into epoxy resin could reduce the viscosity during preparation process and improve the toughness effectively. It was ascribed to the ring-opening reaction of 5CC-EGDE with curing agent, and hydrogen bonding, formed between urethane groups and other polar groups. Besides, the low crosslinking density and unreacted carbonate groups remaining in epoxy network were beneficial to the movement of molecular chains and dissipation of energy during deformation process. In addition, effects of hydrogen-bonding interactions and crosslinking density on mechanical performances were also investigated by varying EGDE conversion and amount of added curing agent, respectively. The results indicated that mechanical performances of epoxy resin were promoted by combined effects of urethane linkage, hydrogen bonding, low crosslinking density and unreacted carbonate groups.

Properties of polydienes in the presence of quaternary ammonium salts from raw materials as vulcanization activators

Properties of polydienes in the presence of quaternary ammonium salts from raw materials as vulcanization activators

Thermal degradation of Polylactide/Poly(ethylene glycol) fibers and composite fibers involving organoclay

In this study, electrospun fibers of melt blended poly(lactic acid) and poly(ethylene glycol), (PLA)-PEG blends involving 10, 15 and 20wt% PEG and their corresponding composites with organically modified montmorillonite, Cloisite 30B were prepared and characterized by x-ray diffraction, differential scanning calorimetry, thermogravimetry and direct pyrolysis mass spectrometry techniques. The narrower fiber diameters observed for the PLA-PEG fibers involving organoclay compared to the corresponding neat fibers were associated with the presence of quaternary ammonium salt as organic modifier increasing electrical conductivity. Strong evidence for phase separation during the electrospinning process was detected for PLA-PEG fibers. On the other hand, for PLA-PEG composite fibers, as a consequence of the diffusion of both PLA and PEG chains from the bulk polymer into the galleries between the silicate layers of the organoclay, the interactions between PLA and PEG chains were enhanced and both components showed similar thermal characteristics, indicating lack of phase separation. These interactions further inhibited the interactions between the PLA chains and organic modifier of the organoclay