Ionothermal Carbonization of Sugarcane Bagasse in 1-Alkyl-3-methylimidazolium Ionic Liquids: Insights into the Role of the Chloroferrate Anion

We report the ionothermal carbonization (ITC) of lignocellulosic biomass in imidazolium tetrachloroferrate ionic liquids (ILs) as an advantageous approach for the preparation of nanostructured carbonaceous materials, namely, ionochars. In a previous study, we investigated the role of the imidazolium cation and demonstrated the possibility of controlling both the textural and morphological properties of ionochars by cation engineering. Although essential for providing intermediate Lewis acidity and relatively high thermal stability, the role of the chloroferrate anion is still open to debate. Herein, we investigated the ITC of sugarcane bagasse and its main component, cellulose, in 1-alkyl-3-methylimidazolium ILs with different chloroferrate anions. We identified anionic speciation and its impact on the properties of the IL by Raman spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The obtained ionochars were characterized by gas physisorption, electron microscopy, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and 13C solid-state CP-MAS NMR spectroscopy. We show that the anionic species have a predominant impact on the textural and morphological properties of the ionochars.

Controlled formation of multi-scale porosity in ionosilica templated by ionic liquid

Mesoporous systems are ubiquitous in membrane science and applications due to their high internal surface area and tunable pore size. A new synthesis pathway of hydrolytic ionosilica films with mesopores formed by ionic liquid (IL) templating is proposed and compared with the traditional non-hydrolytic strategy. For both pathways, the multi-scale formation of pores has been studied as a function of IL content, combining the results of thermogravimetric analysis (TGA), nitrogen sorption, and small-angle X-ray scattering (SAXS). The combination of TGA and nitrogen sorption provides access to ionosilica and pore volume fractions, with contributions of meso- and macropores. We then elaborate an original and quantitative geometrical model to analyze the SAXS data based on small spheres (Rs = 1-2 nm) and cylinders (Lcyl = 10-20 nm) with radial polydispersity provided by the nitrogen sorption isotherms. As a result, we found that for a given incorporation of a templating IL, both synthesis pathways produce very similar pore geometries, but the better incorporation efficacy of the new hydrolytic films provides higher mesoporosity. Our combined study provides a coherent view of mesopore geometry, and thereby an optimization pathway of porous ionic membranes in terms of accessible mesoporosity contributing to the specific surface. Possible applications include electrolyte membranes with improved ionic properties, e.g., in fuel cells and batteries, as well as molecular storage.

Novel Antifouling Coatings by Zwitterionic Silica Grafting on Glass Substrates

Zwitterionic silica coatings for surface functionalization are greatly prominent because of their simple and fast preparation, high availability, and effective antifouling properties. In this work, two zwitterionic sulfobetaine silane coatings, i.e., mono-SBSi and tris-SBSi, were deposited on glass surfaces and tested for antifouling of biological material and biofilm using human cancer cell and seawater, respectively. The used zwitterionic precursors mono-SBSi and tris-SBSi differ by the number of hydrolyzable silane groups: mono-SBSi contains one trimethoxysilane group, whereas tris-SBSi contains three of these functions. First, X-ray photoelectron spectroscopy indicates the successful grafting of zwitterionic coatings onto a glass surface. Characterization using atomic force microscopy shows the different morphologies and roughness of the two coatings. The glass surface became more hydrophilic after the grafting of zwitterionic coatings than the bare glass substrate. The antifouling properties of two coatings were evaluated via human cancer cell adsorption. Interestingly, the tris-SBSi coating displays a significantly lower level of cell adsorption compared to that of both mono-SBSi coating and the non-modified control surface. The same trend was observed for biofilm formation in seawater. Finally, the toxicity of mono-SBSi and tris-SBSi coatings was evaluated on zebrafish embryos, indicating the good biocompatibility of both coatings. Our results indicate interesting antifouling properties of zwitterionic coatings. The chemical constitution of the used precursor has an impact on the antifouling properties of the formed coating: the tris-SBSi-based zwitterionic silica coatings display improved antifouling properties compared to those of the mono-SBSi-based coating. Besides, the use of trisilylated precursors should result in the formation of more resistant and robust coatings due to the higher number of grafting functions. For all these reasons, we anticipate that tris-SBSi coatings will open new perspectives for antifouling applications for biological environments and implants.

Periodic Mesoporous Ionosilica Nanoparticles for Dual Cancer Therapy: Two-Photon Excitation siRNA Gene Silencing in Cells and Photodynamic Therapy in Zebrafish Embryos

Photodynamic therapy (PDT) and photochemical internalization (PCI) are two methods that use light to provoke cell death or disturbance of cellular membranes, respectively, via excitation of a photosensitizer and the formation of reactive oxygen species (ROS). In this context, two-photon excitation (TPE) is of high interest for PCI and/or PDT due to spatiotemporal resolution of two-photon light and deeper penetration of near-infrared light in biological tissues. Here, we report that Periodic Mesoporous Ionosilica Nanoparticles (PMINPs) containing porphyrin groups allow the complexation of pro-apoptotic siRNA. These nano-objects were incubated with MDA-MB-231 breast cancer cells, and TPE-PDT led to significant cell death. Finally, MDA-MB-231 breast cancer cells were pre-incubated with the nanoparticles and then injected in the pericardial cavity of zebrafish embryos. After 24 hours, the xenografts were irradiated with femtosecond pulsed laser and the size monitoring by imaging showed a decrease 24 h after irradiation. Pro-apoptotic siRNA was complexed with the nanoparticles and incubation with MDA-MB-231 cells did not lead to cancer cell death in dark conditions, but with two-photon irradiation, TPE-PCI was observed and a synergic effect between pro-apoptotic siRNA and TPE-PDT was noticed, leading to 90% of cancer cell death. Therefore, PMINPs represent an interesting system for nanomedicine applications.

Wound Dressings Based on Sodium Alginate-Polyvinyl Alcohol-Moringa oleifera Extracts

Biopolymers have significant pharmaceutical applications, and their blending has favorable characteristics for their pharmaceutical properties compared to the sole components. In this work, sodium alginate (SA) as a marine biopolymer was blended with poly(vinyl) alcohol (PVA) to form SA/PVA scaffolds through the freeze-thawing technique. Additionally, polyphenolic compounds in Moringa oleifera leaves were extracted by different solvents, and it was found that extracts with 80% methanol had the highest antioxidant activity. Different concentrations (0.0-2.5%) of this extract were successfully immobilized in SA/PVA scaffolds during preparation. The characterization of the scaffolds was carried out via FT-IR, XRD, TG, and SEM. The pure and Moringa oleifera extract immobilized SA/PVA scaffolds (MOE/SA/PVA) showed high biocompatibility with human fibroblasts. Further, they showed excellent in vitro and in vivo wound healing capacity, with the best effect noted for the scaffold with high extract content (2.5%).

Periodic Mesoporous Ionosilica Nanoparticles for BODIPY Delivery and Photochemical Internalization of siRNA

Periodic Mesoporous Ionosilica Nanoparticles (PMINPs) made via co-condensation reactions starting from an ionosilica precursor and a porphyrin derivative were used for simultaneous BODIPY/siRNA delivery in cancer cells. We observed high BODIPY loading capacities and efficiencies of the PMINPs that are triggered by anion exchange. siRNA adsorption took place on the surface of the nanoparticles, whereas BODIPY was encapsulated within the core of the nanoparticles. BODIPY release was found to be pH-dependent. Our results indicate 94 % BODIPY release after 16 h at pH 4, whereas only 2 % were released at pH 7.4. Furthermore, complexation with siRNA against luciferase gene was observed at the surface of PMINPs and gene silencing through its delivery via photochemical internalization (PCI) mechanism was efficient in MDA-MB-231 breast cancer cells expressing stable luciferase.

Efficient removal of persistent and emerging organic pollutants by biosorption using abundant biomass wastes

Persistent and emerging organic pollutants represent a serious and global threat to human health and ecosystems. We describe here a simple, efficient and affordable technology for removing such organic pollutants from aquatic systems. Biosorption process was chosen, meeting these three criteria, and so that biosorbents should be biomass wastes combining the following characteristics: natural, cheap and abundant. Powdered dead roots from invasive alien species (Eichhornia crassipes, Pistia stratiotes and Fallopia japonica), and wastes rich in tannins such as coffee grounds and green tea grounds were tested as biosorbents for removing extensively used organic pollutants: organic UV-filters, insecticides and herbicides. The elemental composition and morphology of the biosorbents were fully determined. The biosorption kinetics for each pair of biosorbent/pollutant was described by a pseudo-second order model. Excellent biosorption efficiency was obtained for 10 μM solution of oxybenzone (89 ± 1%), octocrylene (90 ± 2%), lindane (88 ± 0%) and diuron (90 ± 1%) in only 2 h. And total removal of 10 μM of chlordecone (100 ± 0%) could be achieved, which could be of high concern for the population living in chlordecone-contaminated areas. As such pollutants can be found in aquatic ecosystems, an interference study with salts showed that biosorption efficiency remained as efficient in reconstituted seawater. A principal component analysis was performed as an attempt to rationalise the biosorption results. The solubility of the organic pollutants in water and the concentration of tanins in the biosorbents were key parameters.

Textural control of ionosilicas by Ionic Liquid templating

Due to their unique self-assembly properties, ionic liquids (ILs) are versatile soft templates for the formation of mesoporous materials. Here, we report the use of ionic liquids as soft templates...

Periodic Mesoporous Ionosilica Nanoparticles for Green Light Photodynamic Therapy and Photochemical Internalization of siRNA

We report periodic mesoporous ionosilica nanoparticles (PMINPs) as versatile nano-objects for imaging, photodynamic therapy (PDT), and efficient adsorption and delivery of small interfering RNA (siRNA) into breast cancer cells. In order to endow these nanoparticles with PDT and siRNA photochemical internalization (PCI) properties, a porphyrin derivative was integrated into the ionosilica framework. For this purpose, we synthesized PMINPs via hydrolysis-cocondensation procedures from oligosilylated ammonium and porphyrin precursors. The formation of these nano-objects was proved by transmission electron microscopy. The formed nanoparticles were then thoroughly characterized via solid-state NMR, nitrogen sorption, dynamic light scattering, and UV-vis and fluorescence spectroscopies. Our results indicate the formation of highly porous nanorods with a length of 108 ± 9 nm and a width of 54 ± 4 nm. A significant PDT effect of type I mechanism (95 ± 2.8% of cell death) was observed upon green light irradiation in nanoparticle-treated breast cancer cells, while the blue light irradiation caused a significant phototoxic effect in non-treated cells. Furthermore, PMINPs formed stable complexes with siRNA (up to 24 h), which were efficiently internalized into the cells after 4 h of incubation mostly with the energy-dependent endocytosis process. The PCI effect was obvious with green light irradiation and successfully led to 83 ± 1.1% silencing of the luciferase gene in luciferase-expressing breast cancer cells, while no gene silencing effect was observed with blue light irradiation. The present work highlights the high potential of porphyrin-doped PMINPs as multifunctional nanocarriers for nucleic acids, such as siRNA, with a triple ability to perform imaging, PDT, and PCI.

Quaternary Ammonium-Based Ionosilica Hydrogels as Draw Solutes in Forward Osmosis

In the last few years, forward osmosis (FO) has attracted increasing interest as a sustainable technique for water desalination and wastewater treatment. However, FO remains as an immature process principally due to the lack of efficient and easily recyclable draw solutes. In this work, we report that ionosilica hydrogels based on quaternary ammonium halide ionosilica are efficient draw solutes in FO. Fluidic ionosilica hydrogels were obtained via hydrolysis-polycondensation reactions of a trisilylated quaternary ammonium precursor in slightly acidic water/ethanol solvent mixtures. The liquid-to-gel transition of the precursor and the kinetics of the formation of hydrogels were monitored by liquid NMR measurements. The formed hydrogels were shown to generate osmotic pressure up to 10.0 atm, indicating the potential of these hydrogels as efficient draw solutes in FO. Our results suggest that iodide anions are the osmotically active species in the system. Regeneration of the hydrogels via ultrafiltration (UF) was successfully achieved, allowing the development of a closed FO-UF process. However, the osmotic performances of the ionosilica hydrogels irreversibly decreased along the successive FO-UF cycles, probably due to anion exchange processes.

Synthesis and antimicrobial properties of new chitosan derivatives containing guanidinium groups

New chitosan derivatives bearing guanidinium functions were synthesized following different synthesis strategies. N-guanidinium chitosan acetate and N-guanidinium chitosan chloride were synthesized by direct reaction between chitosan and cyanamide in the presence of scandium(III) triflate. The synthesis of N-guanidinium chitosan (N,N'-dicyclohexyl) chloride and N-guanidinium chitosan (N-(3-dimethylaminopropyl)-N'-ethyl hydrochloride) chloride involved the reaction of chitosan with carbodiimides in ionic liquid. The chitosan derivatives were characterized by analytical techniques including ¹³C solid state NMR, FT-IR spectroscopies, thermogravimetry and elemental analysis. The antimicrobial properties of chitosan and the new derivatives were investigated using the minimal inhibitory concentration (MIC) technique. All new guanylated chitosan derivatives displayed high antimicrobial activity in comparison with neat chitosan. The N-guanidinium chitosan acetate reduced the time required for killing to half in comparison with chitosan and recorded MIC values less than 3.125 mg/mL against all assayed microorganisms. This work opens new perspectives for using chitosan derivatives as antimicrobial surfaces.

Phase transfer of TiO2 nanoparticles from water to ionic liquid triggered by phosphonic acid grafting

Controlling the interface between TiO₂ nanocrystals and ionic liquids is of high fundamental and applied interest for energy storage and conversion devices. Phase transfer of nanoparticles from a synthesis medium to a processing or an application medium plays a significant role in nanotechnology. Here we demonstrate that surface modification with phosphonic acids bearing cationic end-groups can trigger the phase transfer of TiO₂ nanoparticles from an aqueous sol to a typical water-immiscible ionic liquid, [Emim][NTf₂]. The transfer involves both the grafting of the phosphonic acid moiety and the exchange of the counter ion of the cationic end-group by NTf₂ anions, as demonstrated by solid-state NMR, elemental analysis and independent grafting and ion exchange experiments. Furthermore, the colloidal stability of the TiO₂ sols in [Emim][NTf₂] strongly depends on the hydrophobic character of the cationic end-groups.

Biocompatible Periodic Mesoporous Ionosilica Nanoparticles with Ammonium Walls: Application to Drug Delivery

Periodic mesoporous ionosilica nanoparticles with ammonium walls were synthesized exclusively from a trisilylated ammonium precursor. The nanoparticles display a uniform particle size, together with a high specific surface area and an ordered hexagonal pore architecture. Completely biocompatible in vitro and in vivo, the nanoparticles are efficiently endocytosed by RAW 264.7 macrophages and used as carrier vehicles for anionic drugs. Diclofenac-loaded ionosilica nanoparticles are very efficient in inhibiting lipopolysaccharides-induced inflammation.

Expanding the biomass derived chemical space

The derivatization and covalent modification of biomass derived platform chemicals expand the biomass derived chemical spaces allowing for the preparation of new bioactive molecules and materials.

Biorefinery aims at the conversion of biomass and renewable feedstocks into fuels and platform chemicals, in analogy to conventional oil refinery. In the past years, the scientific community has defined a number of primary building blocks that can be obtained by direct biomass decomposition. However, the large potential of this “renewable chemical space” to contribute to the generation of value added bio-active compounds and materials still remains unexplored. In general, biomass derived building blocks feature a diverse range of chemical functionalities. In order to be integrated into value-added compounds, they require additional functionalization and/or covalent modification thereby generating secondary building blocks. The latter can be thus regarded as functional components of bio-active molecules or materials and represent an expansion of the renewable chemical space. This perspective highlights the most recent developments and opportunities for the synthesis of secondary biomass derived building blocks and their application to the preparation of value added products.

Design of Phosphonated Imidazolium-Based Ionic Liquids Grafted on γ-Alumina: Potential Model for Hybrid Membranes

Imidazolium bromide-based ionic liquids bearing phosphonyl groups on the cationic part were synthesized and grafted on γ-alumina (γ-Al₂O₃) powders. These powders were prepared as companion samples of conventional mesoporous γ-alumina membranes, in order to favor a possible transfer of the results to supported membrane materials, which could be used for CO₂ separation applications. Effective grafting was demonstrated using energy dispersive X-ray spectrometry (EDX), N₂ adsorption measurements, fourier transform infrared spectroscopy (FTIR), and special attention was paid to (31)P and (13)C solid state nuclear magnetic resonance spectroscopy (NMR).

Micellization Behavior of Long-Chain Substituted Alkylguanidinium Surfactants

Surface activity and micelle formation of alkylguanidinium chlorides containing 10, 12, 14 and 16 carbon atoms in the hydrophobic tail were studied by combining conductivity and surface tension measurements with isothermal titration calorimetry. The purity of the resulting surfactants, their temperatures of Cr→LC and LC→I transitions, as well as their propensity of forming birefringent phases, were assessed based on the results of ¹H and (13)C NMR, differential scanning calorimetry (DSC), and polarizing microscopy studies. Whenever possible, the resulting values of Krafft temperature (TK), critical micelle concentration (CMC), minimum surface tension above the CMC, chloride counter-ion binding to the micelle, and the standard enthalpy of micelle formation per mole of surfactant (ΔmicH°) were compared to those characterizing alkyltrimethylammonium chlorides or bromides with the same tail lengths. The value of TK ranged between 292 and 314 K and increased strongly with the increase in the chain length of the hydrophobic tail. Micellization was described as both entropy and enthalpy-driven. Based on the direct calorimetry measurements, the general trends in the CMC with the temperature, hydrophobic tail length, and NaCl addition were found to be similar to those of other types of cationic surfactants. The particularly exothermic character of micellization was ascribed to the hydrogen-binding capacity of the guanidinium head-group.

Alkylguanidinium based ionic liquids in a screening study for the removal of anionic pollutants from aqueous solution

Monoalkylguanidinium bis-trifluoromethane sulfonimides are highly efficient adsorbents for the sequestration of organic anions from aqueous solutions and display strongly enhanced adsorption properties compared to conventional imidazolium ILs.

Ionosilicas as efficient adsorbents for the separation of diclofenac and sulindac from aqueous media

Mesoporous and nanostructured ionosilica material containing ammonium groups was successfully applied for diclofenac and sulindac adsorption via ion exchange.

Anion selectivity in ion exchange reactions with surface functionalized ionosilicas

Mesoporous imidazolium functionalized ionosilicas have been investigated as anion exchange materials for the adsorption of oxo-anions in aqueous media. Pertechnetate exchange in the presence of competing anionic species revealed Hofmeister selectivity.

Periodic mesoporous organosilica from zwitterionic precursors

Mesoporous hybrid silica bearing zwitterionic species were synthesized via template-directed hydrolysis-polycondensation reactions from zwitterionic ammonium sulfonate precursors. The formation of the nanostructured phases involves specific precursor-template interactions. The obtained materials are efficient heterogeneous catalysts in Biginelli reactions.

Hybrid materials and periodic mesoporous organosilicas containing covalently bonded organic anion and cation featuring MCM-41 and SBA-15 structure

We report the synthesis of a new trialkoxysilylated ionic liquid based on disilylated guanidinium and monosilylated sulfonimide species. This compound allowed the successful preparation of new periodic mesoporous organosilicas containing covalently anchored ion-pair through both organo-cationic and organo-anionic moieties which have never been reported up to now. Two classes of hybrid materials containing guanidinium-sulfonimide ion-pairs (IPs) have been synthesized. The first type of material was prepared by grafting the silylated IP onto both MCM-41-type and SBA-15-type silicas according to a surface sol-gel polymerization. The second class was synthesized following a one-pot sol-gel procedure using silylated IP and tetraethoxysilane as framework precursors. These latter materials correspond to so-called periodic mesoporous organosilicas (PMOs) and gave "organo-ionically" modified MCM-41 and SBA-15 related solids. The materials were characterized by a series of techniques including XRD, nitrogen sorption, solid-state NMR, FTIR, transmission electronic microscopy, and elemental analysis. The highest structural regularity in terms of pore size distribution and channel size homogeneity was observed for IP-PMOs possessing SBA-15-type architecture due to an enhanced trialkoxysilylated IP precursor/surfactant interaction. Solvatochromic experiments with Reichardt's dye showed good accessibility of the silica-supported ion-pair and suggested the formation of monophasic materials.

Aerobic Oxidation of Alcohols in Carbon Dioxide with Silica-Supported Ionic Liquids Doped with Perruthenate

The replacement of toxic Cr(VI) for O2 and of chlorinated solvents for supercritical carbon dioxide (or ionic liquids) in the oxidation of alcohols remains hindered by the low selectivity and activity of the current heterogeneous catalysts. Using an integrated approach that combines sol-gel entrapped perruthenate as aerobic catalyst, an encapsulated ionic liquid as solubility promoter, and scCO2 as the reaction solvent, we have developed a system capable of rapidly converting different alcohols into carbonyl compounds with complete selectivity, including substrates which are otherwise difficult to oxidise. The methodology is generally applicable and may easily be extended to other waste-free, catalytic syntheses of fine chemicals.

Task-Specific Ionic Liquids Bearing 2-Hydroxybenzylamine Units: Synthesis and Americium-Extraction Studies

The synthesis of two task-specific ionic liquids (TSILs) bearing 2-hydroxybenzylamine entities is described. These compounds are based on an imidazolium substructure onto which one hydrobenzylamine-complexing moiety is grafted. We have demonstrated that, whether pure or diluted, TSIL is able to extract americium ions. Furthermore, recovery of americium from the IL phase into a receiving phase can be achieved under acidic conditions. A possible mechanism for the metal-ion partitioning is presented, in which the extraction system is driven by an ion-exchange mechanism.

Extraction of Lanthanides from Aqueous Solution by Using Room-Temperature Ionic Liquid and Supercritical Carbon Dioxide in Conjunction

For the first time, the study of a three-step extraction system of water/ionic liquid/supercritical CO2 has been performed. Extraction of trivalent lanthanum and europium from an aqueous nitric acid solution to a supercritical CO2 phase via an imidazolium-based ionic liquid phase is demonstrated, and extraction efficiencies higher than 87 % were achieved. The quantitative extraction is obtained by using different fluorinated beta-diketones with and without the addition of tri(n-butyl)phosphate. The complexation phenomenon occurring in the room-temperature ionic-liquid (RTIL) phase was evidenced by using luminescence spectroscopy.