Ionic Liquids as Designed, Multi-Functional Plasticizers for Biodegradable Polymeric Materials: A Mini-Review.

Measures to endorse the adoption of eco-friendly biodegradable plastics as a response to the scale of plastic pollution has created a demand for innovative products from materials from Nature. Ionic liquids (ILs) have the ability to disrupt the hydrogen bonding network of biopolymers, increase the mobility of biopolymer chains, reduce friction, and produce materials with various morphologies and mechanical properties. Due to these qualities, ILs are considered ideal for plasticizing biopolymers, enabling them to meet a wide range of specifications for biopolymeric materials. This mini-review discusses the effect of different IL-plasticizers on the processing, tensile strength, and elasticity of materials made from various biopolymers (e.g., starch, chitosan, alginate, cellulose), and specifically covers IL-plasticized packaging materials and materials for biomedical and electrochemical applications. Furthermore, challenges (cost, scale, and eco-friendliness) and future research directions in IL-based plasticizers for biopolymers are discussed.

Renewable Biopolymers Combined with Ionic Liquids for the Next Generation of Supercapacitor Materials.

The search for biocompatible and renewable materials for the next generation of energy devices has led to increasing interest in using biopolymers as a matrix component for the development of electric double-layer capacitors (EDLCs). However, using biopolymers as host matrices presents limitations in performance and scalability. At the same time, ionic liquids (ILs) have shown exceptional properties as non-aqueous electrolytes. This review intends to highlight the progress in integrating ILs and biopolymers for EDLC. While ILs have been used as solvents to process biopolymers and electrolyte materials, biopolymers have been utilized to provide novel chemistries of electrolyte materials via one of the following scenarios: (1) acting as host polymeric matrices for IL-support, (2) performing as polymeric fillers, and (3) serving as backbone polymer substrates for synthetic polymer grafting. Each of these scenarios is discussed in detail and supported with several examples. The use of biopolymers as electrode materials is another topic covered in this review, where biopolymers are used as a source of carbon or as a flexible support for conductive materials. This review also highlights current challenges in materials development, including improvements in robustness and conductivity, and proper dispersion and compatibility of biopolymeric and synthetic polymeric matrices for proper interface bonding.

Deep Eutectic Solvents: Alternative Solvents for Biomass-Based Waste Valorization.

Innovative technologies can transform what are now considered "waste streams" into feedstocks for a range of products. Indeed, the use of biomass as a source of biopolymers and chemicals currently has a consolidated economic dimension, with well-developed and regulated markets, in which the evaluation of the manufacturing processes relies on specific criteria such as purity and yield, and respects defined regulatory parameters for the process safety. In this context, ionic liquids and deep eutectic solvents have been proposed as environmentally friendly solvents for applications related to biomass waste valorization. This mini-review draws attention to some recent advancements in the use of a series of new-solvent technologies, with an emphasis on deep eutectic solvents (DESs) as key players in the development of new processes for biomass waste valorization. This work aims to highlight the role and importance of DESs in the following three strategic areas: chitin recovery from biomass and isolation of valuable chemicals and biofuels from biomass waste streams.

Phase Behavior of Aqueous Biphasic Systems with Choline Alkanoate Ionic Liquids and Phosphate Solutions: The Influence of pH.

Aqueous biphasic systems (ABS) composed of the choline alkanoate ionic liquids (ILs) choline acetate [Cho][OAc], choline propanoate [Cho][Pro], choline butyrate [Cho][But], and choline hexanoate [Cho][Hex], mixed with K3PO4 solutions at pH 7.2 and 14.5, were prepared and their phase diagrams were compared. The ability to form ABS with alkaline K3PO4 solutions decreased in the order [Cho][OAc] ≈ [Cho][Pro] > [Cho][But] > [Cho][Hex], while with neutral K3PO4 solutions, [Cho][OAc] could not form an ABS, and the other three ILs performed similarly. All of the biphasic regions of the ABS decreased with the increase in pH. 1H-NMR data indicated anion exchange between phases in ABS at neutral pH. The ABS at neutral pH were evaluated to extract the triazine herbicides simazine, cyanazine, and atrazine, and the ABS formed by [Cho][Pro] and the pH 7.2 K3PO4 solution has shown extraction recoveries higher than 90%.

Efficient Low-Cost Procedure for Microextraction of Estrogen from Environmental Water Using Magnetic Ionic Liquids.

In this study, three magnetic ionic liquids (MILs) were investigated for extraction of four estrogens, i.e., estrone (E1), estradiol (E2), estriol (E3), and ethinylestradiol (EE2), from environmental water. The cation trihexyl(tetradecyl)phosphonium ([P66614]+), selected to confer hydrophobicity to the resulting MIL, was combined with tetrachloroferrate(III), ferricyanide, and dysprosium thiocyanate to yield ([P66614][FeCl4]), ([P66614]3[Fe(CN)6]), and ([P66614]5[Dy(SCN)8]), respectively. After evaluation of various strategies to develop a liquid-liquid microextraction technique based on synthesized MILs, we placed the MILs onto a magnetic stir bar and used them as extracting solvents. After extraction, the MIL-enriched phase was dissolved in methanol and injected into an HPLC-UV for qualitative and quantitative analysis. An experimental design was used to simultaneously evaluate the effect of select variables and optimization of extraction conditions to maximize the recovery of the analytes. Under optimum conditions, limits of detection were in the range of 0.2 (for E3 and E2) and 0.5 µg L-1 (for E1), and calibration curves exhibited linearity in the range of 1-1000 µg L-1 with correlation coefficients higher than 0.998. The percent relative standard deviation (RSD) was below 5.0%. Finally, this method was used to determine concentration of estrogens in real lake and sewage water samples.

Singlet Oxygen Production and Tunable Optical Properties of Deacetylated Chitin-Porphyrin Crosslinked Films.

The increasing need for biocompatible materials as supports to immobilize photosensitizer molecules for photodynamic therapy (PDT), led us to investigate the use of chitin as a support for 4,4',4″,4‴-(porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid) (mTCPP) for singlet oxygen production. Chitin was first extracted from shrimp shells using the ionic liquid 1-ethyl-3-methyl-imidazolium acetate ([C2mim][OAc]), coagulated as a floc into water, and then deacetylated to varying degrees of deacetylation using 4 M NaOH. The deacetylated chitin (DA-chitin) was dissolved in [C2mim][OAc] and mTCPP was covalently attached by reaction between the amino groups of DA-chitin and the carboxyl groups of mTCPP using N-(3-(dimethylamino)propyl)- N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) as activators. The resulting composite polymers were cast as a film and coagulated with water to remove IL and excess reagents, resulting in homogeneous DA-chitin/mTCPP films. Attempts to prepare films by coagulation from a solution containing chitin and mTCPP to physically entrap the porphyrin, resulted in aggregation of mTCPP in the film. The DA-chitin/mTCPP films had strong optical absorbance and their absorbance intensity could be tuned by changing the mTCPP content and degrees of deacetylation of DA-chitin in a predictive manner. In addition, metal ions (Cu2+, Zn2+, Gd3+, and Fe3+) could be easily chelated into the DA-chitin/mTCPP films through mixing metal salt solutions with the films and heating. After chelating metal ions, optical properties, such as absorption region and intensities, of the films changed, suggesting chelating metal ions could tune their optical properties. Moreover, the DA-chitin/mTCPP films could generate singlet oxygen under light irradiation and, hence, might serve as a photosensitizer in PDT. The methodology used in this study is also applicable for developing other functional biomaterial devices.

Coprecipitation-assisted coacervative extraction coupled to high-performance liquid chromatography: An approach for determining organophosphorus pesticides in water samples.

An analytical methodology based on coprecipitation-assisted coacervative extraction coupled to HPLC-UV was developed for determination of five organophosphorus pesticides (OPPs), including fenitrothion, guthion, parathion, methidathion, and chlorpyrifos, in water samples. It involves a green technique leading to an efficient and simple analytical methodology suitable for high-throughput analysis. Relevant physicochemical variables were studied and optimized on the analytical response of each OPP. Under optimized conditions, the resulting methodology was as follows: an aliquot of 9 mL of water sample was placed into a centrifuge tube and 0.5 mL sodium citrate 0.1 M, pH 4; 0.08 mL Al2 (SO4 )3 0.1 M; and 0.7 mL SDS 0.1 M were added and homogenized. After centrifugation the supernatant was discarded. A 700 µL aliquot of the coacervate-rich phase obtained was dissolved with 300 µL of methanol and 20 µL of the resulting solution was analyzed by HPLC-UV. The resulting LODs ranged within 0.7-2.5 ng/mL and the achieved RSD and recovery values were <8% (n = 3) and >81%, respectively. The proposed analytical methodology was successfully applied for the analysis of five OPPs in water samples for human consumption of different locations of Mendoza.

Determination of polybrominated diphenyl ethers in milk samples. Development of green extraction coupled techniques for sample preparation.

Ultrasound-assisted extraction (UAE), cloud point extraction (CPE), and ultrasound back-extraction (UABE) techniques have been coupled for lixiviation, preconcentration, and cleanup of polybrominated diphenyl ethers (PBDEs) from milk samples for determination by gas chromatography-electron capture detection (GC-ECD). Physicochemical parameters that affect the efficiency of the extraction system were investigated using a design of experiments based on multivariate statistical tools, and considering the sample matrix along the development. The coupling of the leaching step, UAE, enhanced ca. 3.5 times the extraction efficiency of the former sample preparation methodology (CPE-UABE) leading to cleaner sample extracts suitable for GC analysis. Under optimum conditions, the proposed methodology exhibits successful performance in terms of linearity and precision, with recoveries in the range of 68-70% and LODs within the range 0.05-0.5 ng/g dry weight (d.w.). The proposed sample preparation methodology coupled three green analytical techniques. It expands the application frontiers of CPE for the analysis of biological samples by GC. The optimized methodology was used for determination of PBDEs in powder milk samples, from both commercial and human sources.

Separate mechanisms of ion oligomerization tune the physicochemical properties of n-butylammonium acetate: cation-base clusters vs. anion-acid dimers.

We investigated the ability of the ions comprising protic ionic liquids to strongly interact with their neutral acid and base forms through the characterization of n-butylammonium acetate ([C4NH3][OAc]) in the presence of excess n-butylamine (C4NH2) or excess acetic acid (HOAc). The conjugate and parent acid or base form new nonstoichiometric, noncovalently bound species (i.e., oligomeric ions) which change the physical and chemical properties of the resulting liquids, thus offering tunability. The effects of adding C4NH2 or HOAc to [C4NH3][OAc] on the resulting thermal and spectroscopic properties differ and suggest that C4NH2 interacts primarily with [C4NH3]+ to form 3-dimensional polymeric networks likely similar to those in H2O/[H3O]+, while HOAc interacts primarily with [OAc]- to form oligomeric ions (e.g., [H(OAc)2]-). The densities of the systems increased with the increase of acid content and reached a maximum when the acid molar fraction was 0.90, but decreased with increasing amine concentration. The viscosities decreased significantly with increasing acid or base concentration. The solvent properties of the mixtures were assessed by measuring the solubilities of benzene, ethyl acetate, diethyl ether, heptane, ibuprofen free acid, and lidocaine free base. The solubilities of the organic solutes and active pharmaceutical ingredients can be tuned with the concentration of acid or amine in the mixtures. In addition, crystallization of the active pharmaceutical ingredients can be induced with the modification of the composition of the mixtures. These observations support the usage of these mixtures for the synthesis and purification of acid or basic active pharmaceutical ingredients in the pharmaceutical industry.

Double salt ionic liquids based on 1-ethyl-3-methylimidazolium acetate and hydroxyl-functionalized ammonium acetates: strong effects of weak interactions.

The properties of double salt ionic liquids based on solutions of cholinium acetate ([Ch][OAc]), ethanolammonium acetate ([NH3(CH2)2OH][OAc]), hydroxylammonium acetate ([NH3OH][OAc]), ethylammonium acetate ([NH3CH2CH3][OAc]), and tetramethylammonium acetate ([N(CH3)4][OAc]) in 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) were investigated by NMR spectroscopy and X-ray crystallography. Through mixture preparation, the solubility of [N(CH3)4][OAc] is the lowest, and [Ch][OAc] shows a 3-fold lower solubility than the other hydroxylated ammonium acetate-based salts in [C2mim][OAc] at room temperature. NMR and X-ray crystallographic studies of the pure salts suggest that the molecular-level mechanisms governing such miscibility differences are related to the weaker interactions between the -NH3 groups and [OAc]-, even though three of these salts possess the same strong 1 : 1 hydrogen bonds between the cation -OH group and the [OAc]- ion. The formation of polyionic clusters between the anion and those cations with unsatisfied hydrogen bond donors seems to be a new tool by which the solubility of these salts in [C2mim][OAc] can be controlled.

Surfactant-based ionic liquids for extraction of phenolic compounds combined with rapid quantification using capillary electrophoresis.

A rapid liquid phase extraction employing a novel hydrophobic surfactant-based room temperature ionic liquid (RTIL), tetrabutylphosphonium dioctyl sulfosuccinate ([4C4 P][AOT]), coupled with capillary electrophoretic-UV (CE-UV) detection is developed for removal and determination of phenolic compounds. The long-carbon-chain RTIL used is sparingly soluble in most solvents and can be used to replace volatile organic solvents. This fact, in combination with functional-surfactant-anions, is proposed to reduce the interfacial energy of the two immiscible liquid phases, resulting in highly efficient extraction of analytes. Several parameters that influence the extraction efficiencies, such as extraction time, RTIL type, pH value, and ionic strength of aqueous solutions, were investigated. It was found that, under acidic conditions, most of the investigated phenols were extracted from aqueous solution into the RTIL phase within 12 min. Good linearity was observed over the concentration range of 0.1-80.0 µg/mL for all phenols investigated. The precision of this method, expressed as RSD, was determined to be within 3.4-5.3% range. The LODs (S/N = 3) of the method were in the range of 0.047-0.257 µg/mL. The proposed methodology was successfully applied to determination of phenols in real water samples.

Aluminosilicates-based nanosorbents for heavy metal removal - A review.

Contamination of water bodies with heavy metals poses a significant threat to human health and the environment, requiring the development of effective treatment techniques. In this context, aluminosilicates emerge as promising sorbents due to their cost-effectiveness and natural abundance. This review provides a clear, in-depth, and comprehensive description of the structure, properties, and characteristics of aluminosilicates, supporting their application as adsorbents and highlighting their diversity and adaptability to different matrices and analytes. Furthermore, the functionalization of these materials is thoroughly addressed, detailing the techniques currently used, exposing the advantages and disadvantages of each approach, and establishing comparisons and evaluations of the performances of various functionalized aluminosilicates in the extraction of heavy metals in aqueous matrices. This work aims not only to comprehensively review numerous studies from recent years but also to identify trends in the study of such materials and inspire future research and applications in the field of contaminant removal using aluminosilicates.

An immobilized graphene oxide stationary phase for open-tubular capillary electrochromatography.

The research literature currently abounds with studies of graphene-related materials as a result of the extraordinary properties of such materials. On the basis of these citations, it is clear that the range of applications for such materials is substantial. In this manuscript, we report the immobilization of graphene oxide (GO) onto a fused-silica capillary to form a potential stationary phase for use in open-tubular CEC. We successfully incorporated GO through an in situ condensation reaction with (3-aminopropyl)triethoxysilane after silanization with (3-aminopropyl)triethoxysilane on the inner surface of the capillary. This GO-incorporated capillary was then characterized by use of SEM, infrared spectroscopy, and measurements of EOF. The electrochromatographic features of this stationary phase have also been investigated. Evaluation of acquired data indicates high electrochromatographic resolution and good capillary efficiency. Highly reproducible results between runs, days, and capillaries were also obtained.

Wide dynamic range homodyne interferometry method and its application for piezoactuator displacement measurements.

Multiactuated piezoelectric flextensional actuators (MAPFAs) is a fast-growing technology in development, with a wide range of applications in precision mechanics and nanotechnology. In turn, optical interferometry is an adequate technique to measure nano/micro-displacements and to characterize these MAPFAs. In this work, an efficient method for homodyne phase detection, based on a well-known Bessel functions recurrence relation, is developed, providing practical applications with a high dynamic range. Fading and electronic noise are taken into account in the analysis. An important advantage of the method is that, for each measurement, only a limited number of frequencies in the magnitude spectrum of the photodetected signal are used, without the need to know the phase spectrum. The dynamic range for phase demodulation is from 0.2 to 100π rad (or 10 nm to 16 µm for displacement, using 632.8 nm wavelength). The upper range can be easily expanded by adapting the electronic system to the signal characteristics. By using this interferometric technique, a new XY nanopositioner MAPFA prototype is tested in terms of linearity, displacement frequency response, and coupling rate.

Ionic Liquids as Tools to Incorporate Pharmaceutical Ingredients into Biopolymer-Based Drug Delivery Systems.

This mini-review focuses on the various roles that ionic liquids (ILs) play in the development and applications of biopolymer-based drug delivery systems (DDSs). Biopolymers are particularly attractive as drug delivery matrices due to their biocompatibility, low immunogenicity, biodegradability, and strength, whereas ILs can assist the formation of drug delivery systems. In this work, we showcase the different strategies that were explored using ILs in biopolymer-based DDSs, including impregnation of active pharmaceutical ingredients (APIs)-ILs into biopolymeric materials, employment of the ILs to simplify the process of making the biopolymer-based DDSs, and using the ILs either as dopants or as anchoring agents.

Multifunctional fully biobased aerogels for water remediation: Applications for dye and heavy metal adsorption and oil/water separation.

Water ecosystem contamination from industrial pollutants is an emerging threat to both humans and native species, making it a point of global concern. In this work, fully biobased aerogels (FBAs) were developed by using low-cost cellulose filament (CF), chitosan (CS), citric acid (CA), and a simple and scalable approach, for water remediation applications. The FBAs displayed superior mechanical properties (up to ∼65 kPa m3 kg-1 specific Young's modulus and ∼111 kJ/m3 energy absorption) due to CA acting as a covalent crosslinker in addition to the natural hydrogen bonding and electrostatic interactions between CF and CS. The addition of CS and CA increased the variety of functional groups (carboxylic acid, hydroxyl and amines) on the materials' surface, resulting in super-high dye and heavy metal adsorption capacities (619 mg/g and 206 mg/g for methylene blue and copper, respectively). Further modification of FBAs with a simple approach using methyltrimethoxysilane endowed aerogel oleophilic and hydrophobic properties. The developed FBAs showed a fast performance in water and oil/organic solvents separation with more than 96% efficiency. Besides, the FBA sorbents could be regenerated and reused for multiple cycles without any significant impact on their performance. Moreover, thanks to the presence of amine groups by addition of CS, FBAs also displayed antibacterial properties by preventing the growth of Escherichia coli on their surface. This work demonstrates the preparation of FBAs from abundant, sustainable, and inexpensive natural resources for applications in wastewater purification.

Determination of nitrotyrosine in Arabidopsis thaliana cell cultures with a mixed-mode solid-phase extraction cleanup followed by liquid chromatography time-of-flight mass spectrometry.

In this work, a method for the determination of trace nitrotyrosine (NO(2)Tyr) and tyrosine (Tyr) in Arabidopsis thaliana cell cultures is proposed. Due to the complexity of the resulting extracts after protein precipitation and enzymatic digestion and the strong electrospray signal suppression displayed in the detection of both Tyr and NO(2)Tyr from raw A. thaliana cell culture extracts, a straightforward sample cleanup step was proposed. It was based on the use of mixed-mode solid-phase extraction (SPE) using MCX-type cartridges (Strata™-X-C), prior to identification and quantitation using fast liquid chromatography-electrospray time-of-flight mass spectrometry. Unambiguous confirmation of both amino acids was accomplished with accurate mass measurements (with errors lower than 2 ppm) of each protonated molecule along with a characteristic fragment ion for each species. Recovery studies were accomplished to evaluate the performance of the SPE sample preparation step obtaining average recoveries in the range 92-101%. Limit of quantitation obtained for NO(2)Tyr in A. thaliana extracts was 3 nmol L(-1). Finally, the proposed method was applied to evaluate stress conditions of the plant upon different concentrations of peroxynitrite, a protein-nitrating compound, which induces the nitration of Tyr at the nanomolar range. Detection and confirmation of the compounds demonstrated the usefulness of the proposed approach.

Use of Ionic Liquids in Chitin Biorefinery: A Systematic Review.

Lignocellulosic biomass biorefinery is the most extensively investigated biorefinery model. At the same time, chitin, structurally similar to cellulose and the second most abundant polymer on Earth, represents a unique chemical structure that allows the direct manufacture of nitrogen-containing building blocks and intermediates, a goal not accomplishable using lignocellulosic biomass. However, the recovery, dissolution, and treatment of chitin was fairly challenging until the polymer's easy dissolution in ionic liquids (salts that are liquid at room temperature) was discovered. In this systematic review, we highlight recent developments in the processing of chitin, with a particular emphasis placed on methods conducted with the help of ionic liquids used as solvents, co-solvents, or catalysts. Such use of ionic liquids in the field of chemical transformations of chitin not only allows for shorter times and less harsh reaction conditions, but also results in different outcomes and higher product yields when compared with reactions conducted in "traditional" manner. Valorization of biomass in general, and chitin in particular, is a key enabling strategy of the circular economy, due to the importance of the sustainable production of biomass-based goods and chemicals and full chain resource efficiency. Economics is driven by the production of high-value chemicals or chemical intermediates from various biomasses, and chitinous biomass is a valuable potential resource. A fundamental "paradigm shift" will radically change the balance of oil-based chemicals to biopolymer-based chemicals, and chitin valorization is a necessary step aimed toward its full market competitiveness and flexibility.

Solubility Studies of Cyclosporine Using Ionic Liquids.

Six ionic liquids (ILs) were selected based on their chemical and physical properties to study the solubility of cyclosporine A. Of these, cyclosporine exhibited higher room temperature solubility in 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) than in acetone, an effective molecular solvent used to solubilize and purify cyclosporine. The solubility of cyclosporine in the ILs dramatically increased at higher temperatures, a critical factor that cannot be varied in a wide range with low boiling molecular solvents. The differences in solubility were explored for cyclosporine purification. Cyclosporine was purified up to ∼93% with n-butylammonium acetate ([C4NH3][OAc]) and could be further purified to 95% using an IL/organic solvent biphasic system. After purification, cyclosporine was recovered as an amorphous solid using the ILs.

Enzymatic hydrolysis of ionic liquid-extracted chitin.

Chitin, one of Nature's most abundant biopolymers, can be obtained by either traditional chemical pulping or by extraction using the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate. The IL extraction and coagulation process provides access to a unique chitin, with an open hydrated gel-like structure. Here, enzymatic hydrolysis of this chitin hydrogel, dried shrimp shell, chitin extracted from shrimp shells using IL and then dried, and commercial chitin was carried out using chitinase from Streptomyces griseus. The enzymatic hydrolysis of shrimp shells resulted only in the monomer N-acetylglucosamine, while much higher amounts of the dimer (N,N'-diacetylchitobiose) compared to the monomer were detected when using all forms of 'pure' chitin. Interestingly, small amounts of the trimer (N,N',N''-triacetylchitotriose) were also detected when the IL-chitin hydrogel was used as substrate. Altogether, our findings indicate that the product distribution and yield are highly dependent on the substrate selected for the reaction and its hydrated state.