Special Issue "Ionic Liquids as Task-Specific Materials"

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanofabrication and Nanomanufacturing".

Deadline for manuscript submissions: 30 June 2022.

Special Issue Editors

Dr. Ana B. Pereiro
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Guest Editor
LAQV, REQUIMTE, Department of Chemistry, NOVA School of Science and Technology, NOVA University of Lisbon, 2829-516 Caparica, Portugal
Interests: ionic liquids; chemical engineering; thermodynamic study; phase equilibria; separation processes
Special Issues and Collections in MDPI journals
Dr. João M. M. Araújo
E-Mail Website
Guest Editor
LAQV, REQUIMTE, Department of Chemistry, NOVA School of Science and Technology, NOVA University of Lisbon, 2829-516 Caparica, Portugal
Interests: separation/purification processes; aqueous biphasic systems; solubilisation and aggregation mechanisms; biomass valorisation
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Ionic liquids (ILs) have been classified as excellent supported materials, solvents and co-solvents for their capacity to dissolve, extract, and purify different compounds in a wide range of applications. These compounds are considered tuneable materials due to their capacity to form different nanosegregated domains (polar, hydrogenated apolar and fluorinated apolar) which enhances their tuneability capacities and solvent quality. Then, the ideal material can be fine-tuned through the selection of each of the nanosegregated domains, and the contribution of each type of interaction (Coulombic, van der Waals and hydrogen bonding).

Prof. Ana Belén Pereiro
Prof. João M. M. Araújo
Guest Editor

Manuscript Submission Information

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Keywords

  • Ionic Liquids
  • Nanomaterials
  • Solvents
  • Dissolution
  • Extraction

Published Papers (7 papers)

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Research

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Article
Covalent Immobilization of Polyaniline Doped with Ag+ or Cu2+ on Carbon Nanotubes for Ethylene Chemical Sensing
Nanomaterials 2021, 11(8), 1993; https://doi.org/10.3390/nano11081993 - 03 Aug 2021
Cited by 1 | Viewed by 428
Abstract
Multi-walled carbon nanotubes (MWCNTs) are promising materials for chemical gas sensing because of their high electrical and mechanical properties and significant sensitivity to changes in the local environment. However, high-content MWCNT films suffer from the low tunability of the electrical resistance, which is [...] Read more.
Multi-walled carbon nanotubes (MWCNTs) are promising materials for chemical gas sensing because of their high electrical and mechanical properties and significant sensitivity to changes in the local environment. However, high-content MWCNT films suffer from the low tunability of the electrical resistance, which is crucial for high chemoresistive sensing performance. This study reports the conjugation of MWCNTs and oligomers of polyaniline (PANI) doped with Ag+ or Cu2+ incorporated into a PVC/polyacrylate. MWCNTs were sonicated in n-methyl pyrrolidine (NMP), and PANI was conjugated via a 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and an N-hydroxysuccinimide (EDC/NHS) process. MWCNT/PANI Ag+ or Cu2+ conjugates were doped to form a coordinate bond. The doped conjugates were successfully incorporated into the PVC/polyacrylate. These MWCNT/PANI conjugates doped were exposed to different concentrations of ethylene gas to examine their feasibility for ethylene detection. Full article
(This article belongs to the Special Issue Ionic Liquids as Task-Specific Materials)
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Article
Integration of Stable Ionic Liquid-Based Nanofluids into Polymer Membranes. Part I: Membrane Synthesis and Characterization
Nanomaterials 2021, 11(3), 607; https://doi.org/10.3390/nano11030607 - 28 Feb 2021
Cited by 2 | Viewed by 667
Abstract
In this work, polymeric membranes functionalized with ionic liquids (ILs) and exfoliated graphene nanoplatelets (xGnP) were developed and characterized. These membranes based on graphene ionanofluids (IoNFs) are promising materials for gas separation. The stability of the selected IoNFs in the polymer membranes was [...] Read more.
In this work, polymeric membranes functionalized with ionic liquids (ILs) and exfoliated graphene nanoplatelets (xGnP) were developed and characterized. These membranes based on graphene ionanofluids (IoNFs) are promising materials for gas separation. The stability of the selected IoNFs in the polymer membranes was determined by thermogravimetric analysis (TGA). The morphology of membranes was characterized using scanning electron microscope (SEM) and interferometric optical profilometry (WLOP). SEM results evidence that upon the small addition of xGnP into the IL-dominated environment, the interaction between IL and xGnP facilitates the migration of xGnP to the surface, while suppressing the interaction between IL and Pebax®1657. Fourier transform infrared spectroscopy (FTIR) was also used to determine the polymer–IoNF interactions and the distribution of the IL in the polymer matrix. Finally, the thermodynamic properties and phase transitions (polymer–IoNF) of these functionalized membranes were studied using differential scanning calorimetry (DSC). This analysis showed a gradual decrease in the melting point of the polyamide (PA6) blocks with a decrease in the corresponding melting enthalpy and a complete disappearance of the crystallinity of the polyether (PEO) phase with increasing IL content. This evidences the high compatibility and good mixing of the polymer and the IoNF. Full article
(This article belongs to the Special Issue Ionic Liquids as Task-Specific Materials)
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Article
Integration of Stable Ionic Liquid-Based Nanofluids into Polymer Membranes. Part II: Gas Separation Properties toward Fluorinated Greenhouse Gases
Nanomaterials 2021, 11(3), 582; https://doi.org/10.3390/nano11030582 - 26 Feb 2021
Cited by 1 | Viewed by 649
Abstract
Membrane technology can play a very influential role in the separation of the constituents of HFC refrigerant gas mixtures, which usually exhibit azeotropic or near-azeotropic behavior, with the goal of promoting the reuse of value-added compounds in the manufacture of new low-global warming [...] Read more.
Membrane technology can play a very influential role in the separation of the constituents of HFC refrigerant gas mixtures, which usually exhibit azeotropic or near-azeotropic behavior, with the goal of promoting the reuse of value-added compounds in the manufacture of new low-global warming potential (GWP) refrigerant mixtures that abide by the current F-gases regulations. In this context, the selective recovery of difluorometane (R32, GWP = 677) from the commercial blend R410A (GWP = 1924), an equimass mixture of R32 and pentafluoroethane (R125, GWP = 3170), is sought. To that end, this work explores for the first time the separation performance of novel mixed-matrix membranes (MMMs) functionalized with ioNanofluids (IoNFs) consisting in a stable suspension of exfoliated graphene nanoplatelets (xGnP) into a fluorinated ionic liquid (FIL), 1-ethyl-3-methylpyridinium perfluorobutanesulfonate ([C2C1py][C4F9SO3]). The results show that the presence of IoNF in the MMMs significantly enhances gas permeation, yet at the expense of slightly decreasing the selectivity of the base polymer. The best results were obtained with the MMM containing 40 wt% IoNF, which led to an improved permeability of the gas of interest (PR32 = 496 barrer) with respect to that of the neat polymer (PR32 = 279 barrer) with a mixed-gas separation factor of 3.0 at the highest feed R410A pressure tested. Overall, the newly fabricated IoNF-MMMs allowed the separation of the near-azeotropic R410A mixture to recover the low-GWP R32 gas, which is of great interest for the circular economy of the refrigeration sector. Full article
(This article belongs to the Special Issue Ionic Liquids as Task-Specific Materials)
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Article
Nanomaterial Synthesis in Ionic Liquids and Their Use on the Photocatalytic Degradation of Emerging Pollutants
Nanomaterials 2021, 11(2), 411; https://doi.org/10.3390/nano11020411 - 05 Feb 2021
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Abstract
The unique properties of ionic liquids make them suitable candidates to prepare nanoscale materials. A simple method that uses exclusively a corresponding bulk material and an ionic liquid—in this case, [P6,6,6,14]Cl—was used to prepare AgCl nanoparticles and [email protected]3O4 [...] Read more.
The unique properties of ionic liquids make them suitable candidates to prepare nanoscale materials. A simple method that uses exclusively a corresponding bulk material and an ionic liquid—in this case, [P6,6,6,14]Cl—was used to prepare AgCl nanoparticles and [email protected]3O4 or TiO2@Fe3O4 magnetic nanocomposites. The prepared nanomaterials were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, and X-ray photoelectron spectroscopy. The photodegradation of atenolol as a model pharmaceutical pollutant in wastewater was investigated under ultraviolet–visible light irradiation using the different synthesized nanocatalysts. In the presence of 0.75 g·L−1 AgCl nanoparticles, a practically complete degradation of 10 ppm of atenolol was obtained after 30 min, following pseudo-first-order reaction kinetics. The effect of different variables (concentrations, pH, oxidant agents, etc.) was analyzed. The recyclability of the nanocatalyst was tested and found to be successful. A degradation mechanism was also proposed. In order to improve the recovery stage of the nanocatalyst, the use of magnetic nanocomposites is proposed. Under the same experimental conditions, a slightly lower and slower degradation was achieved with an easier separation. The main conclusions of the paper are the suitability of the use of ionic liquids to prepare different nanocatalysts and the effectiveness of these at degrading an emerging pollutant in wastewater treatment. Full article
(This article belongs to the Special Issue Ionic Liquids as Task-Specific Materials)
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Article
Characterization of Local Structures of Confined Imidazolium Ionic Liquids in PVdF-co-HFP Matrices by High Pressure Infrared Spectroscopy
Nanomaterials 2020, 10(10), 1973; https://doi.org/10.3390/nano10101973 - 05 Oct 2020
Cited by 3 | Viewed by 707
Abstract
The nanoscale ion ordering of ionic liquids at confined interfaces under high pressures was investigated in this study. 1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf2])/poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-co-HFP) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2])/PVdF-co-HFP were prepared and characterized by using high-pressure infrared spectroscopy. Under ambient pressure, [...] Read more.
The nanoscale ion ordering of ionic liquids at confined interfaces under high pressures was investigated in this study. 1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf2])/poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-co-HFP) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2])/PVdF-co-HFP were prepared and characterized by using high-pressure infrared spectroscopy. Under ambient pressure, imidazolium C2–H and C4,5–H absorptions were blue-shifted in frequency due to the presence of PVdF-co-HFP. However, the absorption of anionic νa SO2 did not reveal any significant shifts in frequency upon dilution by PVdF-co-HFP. The experimental results suggest that PVdF-co-HFP disturbs the local structures of the imidazolium C–H groups instead of the anionic SO2 groups. The frequency shifts of C4,5–H became dramatic for the mixtures at high pressures. These results suggest that pressure-enhanced ionic liquid–polymer interactions may play an appreciable role in IL-PVdF-co-HFP systems under high pressures. The pressure-induced blue-shifts due to the PVdF-co-HFP additions were more obvious for the [HMIM][NTf2] mixtures than for [EMIM][NTf2] mixtures. Full article
(This article belongs to the Special Issue Ionic Liquids as Task-Specific Materials)
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Article
Tailor-Made Fluorinated Ionic Liquids for Protein Delivery
Nanomaterials 2020, 10(8), 1594; https://doi.org/10.3390/nano10081594 - 14 Aug 2020
Cited by 3 | Viewed by 786
Abstract
Nowadays, pharmaceutical companies are facing several challenges with the development and approval of new biological products. The unique properties of several fluorinated ionic liquids (FILs), such as their high surfactant power in aqueous solutions, their chemical and biological stability, and low toxicity, favor [...] Read more.
Nowadays, pharmaceutical companies are facing several challenges with the development and approval of new biological products. The unique properties of several fluorinated ionic liquids (FILs), such as their high surfactant power in aqueous solutions, their chemical and biological stability, and low toxicity, favor their application in the pharmaceutical industry. Furthermore, the numerous combinations between cations and anions, in the FILs design, enlarge the possibilities to construct a successful delivery system. Several FILs also proved to not affect the activity, stability, and secondary structure of the therapeutic protein lysozyme. This work aims to study the aggregation behavior of distinct FILs in the protein suitable medium, in the presence or absence of lysozyme. Besides, different incubation conditions were tested to guarantee the optimal enzymatic activity of the protein at more stable delivery systems. Following the optimization of the incubation conditions, the quantification of the encapsulated lysozyme was performed to evaluate the encapsulation efficiency of each FIL-based system. The release of the protein was tested applying variables such as time, temperature, and ultrasound frequency. The experimental results suggest that the aggregation behavior of FILs is not significantly influenced by the protein and/or protein buffer and supports their application for the design of delivery systems with high encapsulation efficiencies, maintaining the biological activity of either encapsulated and released protein. Full article
(This article belongs to the Special Issue Ionic Liquids as Task-Specific Materials)
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Review

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Review
Advances Achieved by Ionic-Liquid-Based Materials as Alternative Supports and Purification Platforms for Proteins and Enzymes
Nanomaterials 2021, 11(10), 2542; https://doi.org/10.3390/nano11102542 - 28 Sep 2021
Viewed by 401
Abstract
Ionic liquids (ILs) have been applied in several fields in which enzymes and proteins play a noteworthy role, for instance in biorefinery, biotechnology, and pharmaceutical sciences, among others. Despite their use as solvents and co-solvents, their combination with materials for protein- and enzyme-based [...] Read more.
Ionic liquids (ILs) have been applied in several fields in which enzymes and proteins play a noteworthy role, for instance in biorefinery, biotechnology, and pharmaceutical sciences, among others. Despite their use as solvents and co-solvents, their combination with materials for protein- and enzyme-based applications has raised significant attention in the past few years. Among them, significant advances were brought by supported ionic liquids (SILs), in which ILs are introduced to modify the surface and properties of materials, e.g., as ligands when covalently bond or when physiosorbed. SILs have been mainly investigated as alternative supports for enzymes in biocatalysis and as new supports in preparative liquid chromatography for the purification of high-value proteins and enzymes. In this manuscript, we provide an overview on the most relevant advances by using SILs as supports for enzymes and as purification platforms for a variety of proteins and enzymes. The interaction mechanisms occurring between proteins and SILs/ILs are highlighted, allowing the design of efficient processes involving SILs. The work developed is discussed in light of the respective development phase and innovation level of the applied technologies. Advantages and disadvantages are identified, as well as the missing links to pave their use in relevant applications. Full article
(This article belongs to the Special Issue Ionic Liquids as Task-Specific Materials)
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