Selective Water Pore Recognition and Transport through Self-Assembled Alkyl-Ureido-Trianglamine Artificial Water Channels.

In nature, aquaporins (AQPs) are proteins known for fast water transport through the membrane of living cells. Artificial water channels (AWCs) synthetic counterparts with intrinsic water permeability have been developed with the hope of mimicking the performances and the natural functions of AQPs. Highly selective AWCs are needed, and the design of selectivity filters for water is of tremendous importance. Herein, we report the use of self-assembled trianglamine macrocycles acting as AWCs in lipid bilayer membranes that are able to transport water with steric restriction along biomimetic H-bonding-decorated pores conferring selective binding filters for water. Trianglamine [(±)Δ, (mixture of diastereoisomers) and (R,R)3Δ and (S,S)3Δ], trianglamine hydrochloride (Δ.HCl), and alkyl-ureido trianglamines (n = 4, 6, 8, and 12) [(±)ΔC4, (±)ΔC8, (±)ΔC6, and (±)ΔC12] were synthesized for the studies presented here. The single-crystal X-ray structures confirmed that trianglamines form a tubular superstructure in the solid state. The water translocation is controlled via successive selective H-bonding pores (a diameter of 3 Å) and highly permeable hydrophobic vestibules (a diameter of 5 Å). The self-assembled alkyl-ureido-trianglamines achieve a single-channel permeability of 108 water molecules/second/channel, which is within 1 order of magnitude lower than AQPs with good ability to sterically reject ions and preventing the proton transport. Trianglamines present potential for engineering membranes for water purification and separation technologies.

A facile approach to modify cellulose nanocrystal for the adsorption of perfluorooctanoic acid.

Cellulose-based materials are a sustainable alternative to polymers derived from petroleum. Cellulose nanocrystal (CNC) is a biopolymer belonging to this family; it is commonly known for its important physical and chemical properties and ability to form a film. Modifying CNC via electrostatic interaction provided by cationic polymers is a facile and promising technique to enlarge the application of CNC. Herein, we report the preparation of films, from blends of negatively charged CNC and positively charged poly (trimethyl aminoethyl methacrylate) (PTMAEMA). The interaction between CNC and PTMAEMA was verified by using a quartz crystal microbalance with dissipation monitoring (QCM-D), as well as by measuring the particle size and ζ-potential of the casting mixture. To favor the application of the nanocomposite film in water treatment, the film was supported on Whatman™ paper, and adsorption tests were conducted using perfluorooctanoic acid (PFOA) as a model compound for the family of persistent fluorinated pollutants known as PFAS (per- and polyfluoroalkyl substances).

Synthesis: Molecular Structure, Thermal-Calorimetric and Computational Analyses, of Three New Amine Borane Adducts.

Cyclopropylamine borane C3H5NH2BH3 (C3AB), 2-ethyl-1-hexylamine borane CH3(CH2)3CH(C2H5)CH2NH2BH3 (C2C6AB) and didodecylamine borane (C12H25)2NHBH3 ((C12)2AB) are three new amine borane adducts (ABAs). They are synthesized by reaction of the corresponding amines with a borane complex, the reaction being exothermic as shown by Calvet calorimetry. The successful synthesis of each has been demonstrated by FTIR, Raman and NMR. For instance, the 11B NMR spectra show the presence of signals typical of the NBH3 environment, thereby implying the formation of B-N bonds. The occurrence of dihydrogen bonds (DHBs) for each of the ABAs has been highlighted by DSC and FTIR, and supported by DFT calculations (via the Mulliken charges for example). When heated, the three ABAs behave differently: C3AB and C2C6AB decompose from 68 to 100 °C whereas (C12)2AB is relatively stable up to 173 °C. That means that these ABAs are not appropriate as hydrogen carriers, but the 'most' stable (C12)2AB could open perspectives for the synthesis of advanced materials.

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.

Growth-Induced Wrinkles and Dotlike Patterns of a Swollen Fluoroalkylated Thin Film by the Reaction of Surface-Attached Polymethylhydrosiloxane.

The design of hydrophobic surfaces requires a material which has a low solid surface tension and a simple fabrication process for anchoring and controlling the surface morphology. A generic method for the spontaneous formation of robust instability patterns is proposed through the hydrosilylation of a fluoroalkene bearing dangling chains, Rf = C6F13(CH2)3-, with a soft polymethylhydrosiloxane (PMHS) spin-coated gel polymer (0.8 µm thick) using Karstedt catalyst. These patterns were easily formed by an irreversible swelling reaction due to the attachment of a layer to various substrates. The buckling instability was created by two different approaches for a gel layer bound to a rigid silicon wafer substrate (A) and to a soft nonswelling silicone elastomer foundation (B). The observations of grafted Rf-PMHS films in the swollen state by microscopy revealed two distinct permanent patterns on various substrates: dotlike of wavelength λ = 0.4-0.7 µm (A) or wrinkle of wavelength λ = 4-7 µm (B). The elastic moduli ratios of film/substrate were determined using PeakForce quantitative nanomechanical mapping. The characteristic wavelengths (λ) of the patterns for systems A and B were quantitatively estimated in relation to the thickness of the top layer. A diversity of wrinkle morphologies can be achieved by grafting different side chains on pristine PMHS films. The water contact angle (WCA) hysteresis of fluorinated chain (Rf) was enhanced upon roughening the surfaces, giving highly hydrophobic surface properties for water with static/hysteresis WCAs of 136°/74° in the resulting wrinkle (B) and 119°/41° in the dotlike of lower roughness (A). The hydrophobic properties of grafted films on A with various mixtures of hexyl/fluoroalkyl chains were characterized by static CA: WCA 104-119°, ethylene glycol CA 80-96°, and n-hexadecane CA 17-61°. A very low surface energy of 15 mN/m for Rf-PMHS was found on the smoother dotlike pattern.

Hydrolysis of the Borohydride Anion BH4-: A 11B NMR Study Showing the Formation of Short-Living Reaction Intermediates including BH3OH.

In hydrolysis and electro-oxidation of the borohydride anion BH4-, key reactions in the field of energy, one critical short-living intermediate is BH3OH-. When water was used as both solvent and reactant, only BH3OH- is detected by 11B NMR. By moving away from such conditions and using DMF as solvent and water as reactant in excess, four 11B NMR quartets were observed. These signals were due to BH3-based intermediates as suggested by theoretical calculations; they were DMF·BH3, BH3OH-, and B2H7- (i.e., [H3B-H-BH3]- or [H4B-BH3]-). Our results shed light on the importance of BH3 stemming from BH4- and on its capacity as Lewis acid to interact with Lewis bases such as DMF, OH-, and BH4-. These findings are important for a better understanding at the molecular level of hydrolysis of BH4- and production of impurities in boranes synthesis.

Tunable TiO2-BN-Pd nanofibers by combining electrospinning and atomic layer deposition to enhance photodegradation of acetaminophen.

The demand for fresh and clean water sources is increasing globally, and there is a need to develop novel routes to eliminate micropollutants and other harmful species from water. Photocatalysis is a promising alternative green technology that has shown great performance in the degradation of persistent pollutants. Titanium dioxide is the most used catalyst owing to its attractive physico-chemical properties, but this semiconductor presents limitations in the photocatalysis process due to the high band gap and the fast recombination of the photogenerated carriers. Herein, a novel photocatalyst has been developed, based on titanium dioxide nanofibers (TiO2 NFs) synthesized by electrospinning. The TiO2 NFs were coated by atomic layer deposition (ALD) to grow boron nitride (BN) and palladium (Pd) on their surface. The UV-Vis spectroscopy measurements confirmed the increase of the band gap and the extension of the spectral response to the visible range. The obtained TiO2/BN/Pd nanofibers were then tested for photocatalysis, and showed a drastic increase of acetaminophen (ACT) degradation (>90%), compared to only 20% degradation obtained with pure TiO2 after 4 h of visible light irradiation. The high photocatalytic activity was attributed to the good dispersion of Pd NPs on TiO2-BN nanofibers, leading to a higher transfer of photoexcited hole carriers and a decrease of photogenerated electron-charge recombination. To confirm its reusability, recycling tests on the hybrid photocatalyst TiO2/BN/Pd have been performed, showing a good stability over 5 cycles under UV and visible light. In addition, toxicity tests as well as quenching tests were carried out to check the toxicity of the byproducts formed and to determine active species responsible for the degradation. The results presented in this work demonstrate the potential of TiO2/BN/Pd nanomaterials, and open new prospects for the preparation of tunable photocatalysts.

Improved electrochemical conversion of CO2 to multicarbon products by using molecular doping.

The conversion of CO2 into desirable multicarbon products via the electrochemical reduction reaction holds promise to achieve a circular carbon economy. Here, we report a strategy in which we modify the surface of bimetallic silver-copper catalyst with aromatic heterocycles such as thiadiazole and triazole derivatives to increase the conversion of CO2 into hydrocarbon molecules. By combining operando Raman and X-ray absorption spectroscopy with electrocatalytic measurements and analysis of the reaction products, we identified that the electron withdrawing nature of functional groups orients the reaction pathway towards the production of C2+ species (ethanol and ethylene) and enhances the reaction rate on the surface of the catalyst by adjusting the electronic state of surface copper atoms. As a result, we achieve a high Faradaic efficiency for the C2+ formation of ≈80% and full-cell energy efficiency of 20.3% with a specific current density of 261.4 mA cm-2 for C2+ products.

Manganese distribution in the Mn-hyperaccumulator Grevillea meisneri from New Caledonia.

New Caledonian endemic Mn-hyperaccumulator Grevillea meisneri is useful species for the preparation of ecocatalysts, which contain Mn-Ca oxides that are very difficult to synthesize under laboratory conditions. Mechanisms leading to their formation in the ecocatalysts are unknown. Comparing tissue-level microdistribution of these two elements could provide clues. We studied tissue-level distribution of Mn, Ca, and other elements in different tissues of G. meisneri using micro-X-Ray Fluorescence-spectroscopy (µXRF), and the speciation of Mn by micro-X-ray Absorption Near Edge Structure (µXANES), comparing nursery-grown plants transplanted into the site, and similar-sized plants growing naturally on the site. Mirroring patterns in other Grevillea species, Mn concentrations were highest in leaf epidermal tissues, in cortex and vascular tissues of stems and primary roots, and in phloem and pericycle-endodermis of parent cluster roots. Strong positive Mn/Ca correlations were observed in every tissue of G. meisneri where Mn was the most concentrated. Mn foliar speciation confirmed what was already reported for G. exul, with strong evidence for carboxylate counter-ions. The co-localization of Ca and Mn in the same tissues of G. meisneri might in some way facilitate the formation of mixed Ca-Mn oxides upon preparation of Eco-CaMnOx ecocatalysts from this plant. Grevillea meisneri has been successfully used in rehabilitation of degraded mining sites in New Caledonia, and in supplying biomass for production of ecocatalysts. We showed that transplanted nursery-grown seedlings accumulate as much Mn as do spontaneous plants, and sequester Mn in the same tissues, demonstrating the feasibility of large-scale transplantation programs for generating Mn-rich biomass.

New Sustainable Synthetic Routes to Cyclic Oxyterpenes Using the Ecocatalyst Toolbox.

Cyclic oxyterpenes are natural products that are mostly used as fragrances, flavours and drugs by the cosmetic, food and pharmaceutical industries. However, only a few cyclic oxyterpenes are accessible via chemical syntheses, which are far from being ecofriendly. We report here the synthesis of six cyclic oxyterpenes derived from ß-pinene while respecting the principles of green and sustainable chemistry. Only natural or biosourced catalysts were used in mild conditions that were optimised for each synthesis. A new generation of ecocatalysts, derived from Mn-rich water lettuce, was prepared via green processes, characterised by MP-AES, XRPD and TEM analyses, and tested in catalysis. The epoxidation of ß-pinene led to the platform molecule, ß-pinene oxide, with a good yield, illustrating the efficacy of the new generation of ecocatalysts. The opening ß-pinene oxide was investigated in green conditions and led to new and regioselective syntheses of myrtenol, 7-hydroxy-α-terpineol and perillyl alcohol. Successive oxidations of perillyl alcohol could be performed using no hazardous oxidant and were controlled using the new generation of ecocatalysts generating perillaldehyde and cuminaldehyde.

Biobased dynamic hydrogels by reversible imine bonding for controlled release of thymopentin.

Thymopentin (TP5) is widely used in the treatment of autoimmune diseases, but the short in vivo half-life of TP5 strongly restricts its clinical applications. A series of blank and TP5 loaded hydrogels were synthesized via reversible dual imine bonding by mixing water soluble O-carboxymethyl chitosan (CMCS) with a dynamer (Dy) prepared from Jeffamine and benzene-1,3,5-tricarbaldehyde. TP5 release from hydrogels was studied at 37 °C under in vitro conditions. The molar mass of CMCS, drug loading conditions and drug content were varied to elucidate their effects on hydrogel properties and drug release behaviors. Density functional theory was applied to theoretically confirm the chemical connections between TP5 or CMCS with Dy. All hydrogels exhibited interpenetrating porous architecture with average pore size from 59 to 83 µm, and pH-sensitive swelling up to 10,000% at pH 8. TP5 encapsulation affected the rheological properties of hydrogels as TP5 was partially attached to the network via imine bonding. Higher TP5 loading led to higher release rates. Faster release was observed at pH 5.5 than at pH 7.4 due to lower stability of imine bonds in acidic media. Fitting of release data using Higuchi model showed that initial TP5 release was essentially diffusion controlled. All these findings proved that the dynamic hydrogels are promising carriers for controlled delivery of hydrophilic drugs, and shed new light on the design of drug release systems by both physical mixing and reversible covalent bonding.

Eco-Friendly Methodology for the Formation of Aromatic Carbon-Heteroatom Bonds by Using Green Ionic Liquids.

A new sustainable method is reported for the formation of aromatic carbon-heteroatom bonds under solvent-free and mild conditions (no co-oxidant, no strong acid and no toxic reagents) by using a new type of green ionic liquid. The bromination of methoxy arenes was chosen as a model reaction. The reaction methodology is based on only using natural sodium bromine, which is transformed into an electrophilic brominating reagent within an ionic liquid, easily prepared from the melted salt FeCl3 hexahydrate. Bromination reactions with this in-situ-generated reagent gave good yields and excellent regioselectivity under simple and environmentally friendly conditions. To understand the unusual bromine polarity reversal of sodium bromine without any strong oxidant, the molecular structure of the reaction medium was characterised by Raman and direct infusion electrospray ionisation mass spectroscopy (ESI-MS). An extensive computational investigation using density functional theory methods was performed to describe a mechanism that suggests indirect oxidation of Br- through new iron adducts. The versatility of the methodology was successively applied to nitration and thiocyanation of methoxy arenes using KNO3 and KSCN in melted hexahydrated FeCl3 .

Dynamic Hydrogels Based on Double Imine Connections and Application for Delivery of Fluorouracil.

Dynamic hydrogels have been prepared by cross-linking of O-carboxymethyl chitosan (O-CMCS) with reversibly connected imino-PEGylated dynamers. The double imine chitosan/dynamer and dynamer bonds and were used to provide tighter structures and adaptive drug release behaviors of the hydrogels. The structural and physical properties of the resulted hydrogels were examined, showing good thermal stability and higher swelling behaviors (up to 3,000%). When hydrogels with various composition ratios were further applied for delivery of anti-cancer drug fluorouracil (5-FU), high drug encapsulation rates were recorded, up to 97%. The release profile of 5-FU showed fast rate at the beginning, followed by slow increase to the maximum amount within 12 h, demonstrating potential as drug carriers for efficient drug delivery.

Self-assembled micelles prepared from bio-based hydroxypropyl methyl cellulose and polylactide amphiphilic block copolymers for anti-tumor drug release.

Fully bio-based amphiphilic diblock copolymers were synthesized from hydroxypropyl methyl cellulose (HPMC) and amino-terminated poly(l-lactide) (PLLA) or poly(l-lactide-co-dl-lactide) (PLA) by reductive amination. The resulting HPMC-PLLA and HPMC-PLA copolymers with various hydrophobic block lengths were characterized by NMR, DOSY-NMR and FT-IR. Micelles were obtained by self-assembly of copolymers in aqueous medium. The micelles are spherical in shape, and the micelle size ranges from 150 to 180 nm with narrow distribution. The critical micelle concentration decreases with increasing PLA block length. Paclitaxel was loaded in micelles. Enhanced drug loading is obtained with increase of PLA block length. A biphasic release profile is observed with a burst of 40% followed by slower release up to 80%. MTT assay indicates the good cytocompatibility of HPMC-PLA micelles. SRB assay shows a significant cytotoxicity of paclitaxel-loaded micelles against SK-BR-3cells. It is thus concluded that bio-based HPMC-PLA block copolymers could be promising nano-carrier of anti-tumor drugs.

Partial depolymerization of hydroxypropylmethyl cellulose for production of low molar mass polymer chains.

Low molar mass (LMM) biopolymers are highly required to design functional nanomaterials, which mainly find application in biomedical fields. However, the synthesis of LMM polymer is a challenging task. In this work, we report a partial enzymatic depolymerization process which allows to produce a series of LMM hydroxypropylmethyl cellulose (HPMC) polymer, with a weight average molar mass (Mw) under and over 10,000 g mol-1 and low dispersity (Ɖ < 1.5). Variation of the starting HPMC grade, reaction time, and enzyme concentration were the key parameters to control the Mw and yield of the target molecules. This approach provides a versatile way of producing LMM HPMCs with varying degrees of substitution, and having a single reactive aldehyde function at one chain extremity. LMM HPMC can find for instance application as building blocks for the development of new functional molecular architectures.

Enhanced sieving from exfoliated MoS2 membranes via covalent functionalization.

Nanolaminate membranes made of two-dimensional materials such as graphene oxide are promising candidates for molecular sieving via size-limited diffusion in the two-dimensional capillaries, but high hydrophilicity makes these membranes unstable in water. Here, we report a nanolaminate membrane based on covalently functionalized molybdenum disulfide (MoS2) nanosheets. The functionalized MoS2 membranes demonstrate >90% and ~87% rejection for micropollutants and NaCl, respectively, when operating under reverse osmotic conditions. The sieving performance and water flux of the functionalized MoS2 membranes are attributed both to control of the capillary widths of the nanolaminates and to control of the surface chemistry of the nanosheets. We identify small hydrophobic functional groups, such as the methyl group, as the most promising for water purification. Methyl- functionalized nanosheets show high water permeation rates as confirmed by our molecular dynamic simulations, while maintaining high NaCl rejection. Control of the surface chemistry and the interlayer spacing therefore offers opportunities to tune the selectivity of the membranes while enhancing their stability.

Eichhornia crassipes: a Powerful Bio-indicator for Water Pollution by Emerging Pollutants.

Eichhornia crassipes is well known as an invasive aquatic plant. It is also used very effectively in phytoremediation, particularly for the rhizofiltration of effluents contaminated by heavy metals. In this article, we show that it is also an excellent bioindicator of water polluted by worrying organic pollutants such as endocrine disruptors and neonicotinoids. As a proof of concept, di-n-hexylphthalate, pentabromodiphenyl ether, nitenpyram, acetamiprid and bis (3-tert-butyl-4-hydroxy-6-methylphenyl) sulfide were clearly identified by UHPLC-HRMS or GC-MS in the root system of E. crassipes after a short period of exposure. These results open up new perspectives for the remediation of water polluted by alarming organic pollutants.

Novel thermo-responsive micelles prepared from amphiphilic hydroxypropyl methyl cellulose-block-JEFFAMINE copolymers.

A series of amphiphilic and thermo-responsive block copolymers were synthesized by reductive amination between the aldehyde endgroup of hydrophilic HPMC and the amine group of monoamine, diamine, or triamine JEFFAMINE as hydrophobic block. The resulting diblock, triblock and three-armed copolymers with different hydrophilic/hydrophobic ratios and block lengths were characterized by NMR, FT-IR, DOSY-NMR and SEC. The cloud point (CP) of copolymers was determined by UV-visible spectrometer. Data show that both the geometrical structure and the molar mass of HPMC affect the CP of HPMC-JEF copolymers. The higher the hydrophilic/hydrophobic ratio, the higher the CP of copolymers which is lower than that of HPMC homopolymers. The self-assembly behavior of the copolymers was investigated from dynamic light scattering, transmission electron microscopy, and critical micelle concentration (CMC) measurements. Spherical nano-micelles are obtained by self-assembly of copolymers in aqueous solution, and the micelle size can be tailored by varying the block length of HPMC and the geometrical structure. Three-armed HPMC-JEF copolymers present lower CMC and smaller micelle size as compared to linear diblock and triblock ones. MTT assay evidenced the cytocompatibility of HPMC-JEF copolymers, indicating that they could be promising as drug carrier in drug delivery systems.

Depollution of mining effluents: innovative mobilization of plant resources.

Based on the ability of some specific aquatic plants to concentrate metals in their roots, we propose an innovative biosorption system to clean up mining effluents. The system we propose represents an interesting solution to an important environmental problem, the decontamination of metal-polluted water and prevention of dispersal of metals into the environment. The solution presented is a form of ecological recycling of Zn, an essential primary metal in many industrial applications. Finally, the methodology developed is a sustainable way of managing the biomass from eradication or control of invasive plants.

Biosourced Polymetallic Catalysis: A Surprising and Efficient Means to Promote the Knoevenagel Condensation.

Zn hyperaccumulator (Arabidobsis halleri) and Zn accumulator Salix "Tordis" (Salix schwerinii × Salix viminalis) have shown their interest in the phytoextraction of polluted brownfields. Herein, we explore a novel methodology based on the chemical valorization of Zn-rich biomass produced by these metallophyte plants. The approach is based on the use of polymetallic salts derived from plants as bio-based catalysts in organic chemistry. The formed ecocatalysts were characterized via ICP-MS, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) in order to precise the chemical composition, structure, and behavior of the formed materials. The Doebner-Knoevenagel reaction was chosen as model reaction to study their synthetic potential. Significant differences to usual catalysts such as zinc (II) chloride are observed. They can principally be related to a mixture of unusual mineral species. DFT calculations were carried out on these salts in the context of the Gutmann theory. They allow the rationalization of experimental results. Finally, these new bio-based polymetallic catalysts illustrated the interest of this concept for green and sustainable catalysis.