Surface-Active Ionic Liquids and Surface-Active Quaternary Ammonium Salts from Synthesis, Characterization to Antimicrobial Properties.

The present work provides new evidence of the ongoing potential of surface-active ionic liquids (SAILs) and surface-active quaternary ammonium salts (surface-active QASs). To achieve this, a series of compounds were synthesized with a yield of ≥85%, and their thermal analyses were studied. Additionally, antimicrobial activity against both human pathogenic and soil microorganisms was investigated. Subsequently, their surface properties were explored with the aim of utilizing SAILs and surface-active QASs as alternatives to commercial amphiphilic compounds. Finally, we analyzed the wettability of the leaves' surface of plants occurring in agricultural fields at different temperatures (from 5 to 25 °C) and the model plant membrane of leaves. Our results show that the synthesized compounds exhibit higher activity than their commercial analogues such as, i.e., didecyldimethylammonium chloride (DDAC) and dodecyltrimethylammonium bromide (C12TAB), for which the CMC values are 2 mM and 15 mM. The effectiveness of the antimicrobial properties of synthesized compounds relies on their hydrophobic nature accompanied by a cut-off effect. Moreover, the best wettability of the leaves' surface was observed at 25 °C. Our research has yielded valuable insights into the potential effectiveness of SAILs and surface-active QASs as versatile compounds, offering a promising alternative to established antimicrobials and crop protection agents, all the while preserving substantial surface activity.

Quaternary ammonium salts based on caprylic acid as antimicrobial and surface-active agents.

In this work, amidequats and esterquats based on caprylic acid were investigated as promising compounds with surface properties and biological activity that are in harmony with the principles of green chemistry. Herein, caprylic acid, which is an essential component of the above compounds, is a noteworthy natural resource. Structural analysis was performed with the amphiphilic cations of the tested amidequats and esterquats, revealing two distinct factors, i.e., the elongation of the alkyl chain and the presence of two different functional groups; these factors undoubtedly affect the desired biological activity. These compounds were synthesized and characterized in terms of their physicochemical properties, among which surface activity is pivotal. In addition, the surfaces of the tested compounds were investigated through a detailed topographical analysis. The obtained results suggested that the esterquats exhibited higher surface activity, wettability and foamability than the amidequats. Antimicrobial studies, on the other hand, are not as conclusive. For shorter chains, esterquats are more active than amidequats, while for longer chains (over C12), the trend was the opposite. The amidequats and esterquats presented in this research may be a potential good replacement for antimicrobial formulations or as alternatives to surface-active agents used in industry.

Synthesis and Surface Properties of Piperidinium-Based Herbicidal Ionic Liquids as a Potential Tool for Weed Control.

A series of piperidinium-based herbicidal ionic liquids (HILs) were synthesized and investigated. The designed HILs, obtained with high yields, consisted of cation 1-alkyl-1-methylpiperidinium with surface activity and a commercially available herbicidal anion: (3,6-dichloro-2-methoxy)benzoates (dicamba). The above-mentioned compounds were characterized in terms of surface activity and phytotoxicity. Preliminary results were obtained at higher wettability for all HILs when compared to the wettability of commercial Dicash, with HIL having 18 atoms in the carbon chain being the best effectiveness in wetting surfaces (weeds and crop leaves), whereby a drop of HILs with short alkyl chains (C8-C10) could not slide down a leaf. Our findings present that wettability or mobility of HILs drops varied depending on the plant species. Moreover, in this study, by zeta potential and atomic force microscopy measurements, we provide conclusive evidence to demonstrate that alkyl chain elongation plays a significant role in the evolution of surface properties of HILs.

Spent Coffee as a Composite Filler for Wastewater Treatment.

Currently composites play an important role in all aspects of engineering and technology, with constantly growing applications. Recently, more attention was focused on natural fillers due to their suitability as reinforcement materials in thermo-plastic matrices which improve the mechanical properties of these polymers. Biofillers are used due to their low cost, high strength rigidity, non-toxicity, biodegradability, and availability. Currently, spent coffee grounds (SCG) are attracting more attention as a natural filler since high amounts of SCG are generated every day (food waste of coffee processing). This study allowed us to determine the long-term effect of activated sludge microorganisms with known technical and technological parameters on the mechanical properties of composites with spent coffee grounds filler. The fittings consisted of high-density poly-ethylene (PE-HD), which was used as the matrix, and a filler based on spent coffee grounds (SCG), which was used as a modifier. It was established that the composition of the composite and its residence time in the bioreactor directly influenced the contact angle value. The shift of the contact angle value is associated with the formation of the biofilm on the tested materials. An increase in the contact angle was observed in the case of all samples tested in the bioreactor, with the lowest values equal to approx. 76.4° for sample A (PE-HD) and higher values of approx. 90° for the remaining composite samples with a coffee grounds filler. The research confirmed that the increased ratio of coffee grounds in the composite results in the increased diversity and abundance of microorganisms. The highest number and the greatest diversity of microorganisms were observed in the case of the composite with 40% coffee grounds after more than a year of exposure in the bioreactor, while the composite with 30% SCG was second. Ciliates (Ciliata), especially the sessile forms belonging to the Epistylis genus, were the most common and the most numerous group of microorganisms in the activated sludge and in the biofilm observed on the samples after immersion in the bioreactor. The conducted research confirms that the use of polymer composite mouldings with a filler in the form of spent coffee grounds as a carrier allows the efficient increase in the population of microorganisms in the bioreactor.

Effect of 1-alkyl-1-methylpiperidinium bromides on lipids of fungal plasma membrane and lung surfactant.

This study aimed to investigate the potential of 1-alkyl-1-methylpiperidinium bromides as fungicides and evaluate their impact on the human respiratory system when spread in the atmosphere. We investigated the behavior of membrane lipids and model membranes in the presence of a series of amphiphilic 1-alkyl-1-methylpiperidinium bromides ([MePipCn][Br]), differing in the alkyl chain length (n = 4 - 18). The experiments were performed with the Langmuir monolayer technique using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and ergosterol (ERG)-the main components of lung surfactant and fungal plasma membrane, respectively and their mixtures with phospholipids and sterols. The mixtures were chosen as the representatives of target and non-target organisms. The surface pressure-area isotherms were obtained by compressing monolayers in the presence of [MePipCn][Br] in the subphase. The results were analyzed in terms of area expansion/contraction and compressibility. The surface activity of the studied organic salts was also studied. In addition, the monolayers were deposited on a solid surface and their topography was investigated using atomic force microscopy. This research implies that the studied compounds may destabilize efficiently the fungal plasma membrane. At the same time we demonstrated the significant impact of 1-alkyl-1-methylpiperidinium bromides on the lung surfactant layer. The interaction between [MePipCn][Br] and model membranes depends on the concentration and alkyl chain length of organic salt. The key role of contact time has been also revealed. The results may be helpful in the reasonable development of new agrochemical products aiming at the treatment of fungal infections in plants. In addition, our study indicates the significance of proper safety management while spreading the fungicides in the environment.

Antimicrobial and Cytotoxic Activity of Novel Imidazolium-Based Ionic Liquids.

In this study, a series of 10 novel 1-methyl-3-octyloxymethylimidazolium derivatives carrying various anionic moieties (4-hydroxybenzenesulfonate, benzenesulfonate, carvacroloxyacetate, chloride, formate, propionate, thymoloxyacetate, vanillinoxyacetate, eugenoloxyacetate and trimethylacetate) were synthesized. Compounds were tested for their antimicrobial activity against six microbe strains (Staph-ylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Enterococcus faecalis, and Candida albicans), cytotoxic activity against the mouse melanoma cell line (B16 F10), and surface active properties. All synthesized compounds exhibited antimicrobial activity (expressed as minimum inhibitory concentration; in range of 0.10-27.82 mM/L), especially against Gram-positive bacteria and fungi. In addition, all compounds demonstrated cytotoxicity on B16 F10 cells (IC50 values 0.0101-0.0197 mM/L). Surface properties defined as CMC values, ranged from 0.72 to 32.35 mmol L-1. The obtained results provide an insight into the promising activity of a novel group of quaternary imidazolium derivatives having ionic liquid properties. The most potent compounds, containing a thymoloxyacetate and eugenoloxyacetate moiety, could be candidates for new antimicrobial agents or surfactants.