Quaternized Graphene for High-Performance Moisture Swing Direct Air Capture of CO2.

Nowadays, moisture-swing adsorption technology still relies on quaternary ammonium resins with limited CO2 capacity under ambient air conditions. In this work, a groundbreaking moisture-driven sorbent is developed starting from commercial graphene flakes and using glycidyltrimethylammonium chloride for incorporation of CO2-sensitive quaternary ammonium functional groups. Boasting an outstanding CO2 capture performance under ultra-diluted conditions (namely, 3.24 mmol g-1 at CO2 400 ppm and 20% RH), the functionalized sorbent (fGO) features clear competitive advantages over current technologies for direct air capture. Notably, fGO demonstrated unprecedented moisture-swing capacity, ease of regenerability, versatility, selectivity, and longevity. These distinctive features position the fGO as an advanced and promising solution, showcasing its potential to outperform existing methods for moisture-swing direct air capture of CO2.

Elucidating the Water and Methanol Dynamics in Sulfonated Polyether Ether Ketone Nanocomposite Membranes Bearing Layered Double Hydroxides.

Conventional Nafion membranes demonstrate a strong affinity for methanol, resulting in a high fuel crossover, poor mechanical stability, and thus poor performance in direct methanol fuel cells (DMFCs). This study involves the synthesis and physiochemical characterization of an alternative polymer electrolyte membrane for DMFCs based on sulfonated poly(ether ether ketone) and a layered double hydroxide (LDH) material. Nanocomposite membranes (sPL), with filler loading ranging between 1 wt% and 5 wt%, were prepared by simple solution intercalation and characterized by XRD, DMA, swelling tests, and EIS. For the first time, water and methanol mobility inside the hydrophilic channels of sPEEK-LDH membranes were characterized by NMR techniques. The introduction of LDH nanoplatelets improved the dimensional stability while having a detrimental effect on methanol mobility, with its self-diffusion coefficient almost two orders of magnitude lower than that of water. It is worth noting that anionic lamellae are directly involved in the proton transport mechanism, thus enabling the formation of highly interconnected paths for proton conduction. In this regard, sPL3 yielded a proton conductivity of 110 mS cm-1 at 120 °C and 90% RH, almost attaining the performance of the Nafion benchmark. The nanocomposite membrane also showed an excellent oxidative stability (over more than 24 h) during Fenton's test at 80 °C. These preliminary results demonstrate that an sPL3 nanocomposite can be potentially and successfully applied in DMFCs.

Encapsulation of an Anionic Surfactant into Hollow Spherical Nanosized Capsules: Size Control, Slow Release, and Potential Use for Enhanced Oil Recovery Applications and Environmental Remediation.

A new platform that allows encapsulation of anionic surfactants into nanosized capsules and subsequent release upon deployment is described. The system is based on DOWFAX surfactant molecules incorporated into sub-100 nm hollow silica nanoparticles composed of a mesoporous shell. The particles released 40 wt % of the encapsulated surfactant at 70 °C compared to 24 wt % at 25 °C after 21 and 18 days, respectively. The use of the particles for subsurface applications is assessed by studying the effectiveness of the particles to alter the wettability of hydrophobic surfaces and reduction of the interfacial tension. The release of the surfactant molecules in the suspension reduces the contact angle of a substrate from 105 to 25° over 55 min. A sustained release profile is demonstrated by a continuous reduction of the interfacial tension of an oil suspension, where the interfacial tension is reduced from 62 to 2 mN m-1 over a period of 3 days.

New Porous Heterostructures Based on Organo-Modified Graphene Oxide for CO2 Capture.

In this work, we report on a facile and rapid synthetic procedure to create highly porous heterostructures with tailored properties through the silylation of organically modified graphene oxide. Three silica precursors with various structural characteristics (comprising alkyl or phenyl groups) were employed to create high-yield silica networks as pillars between the organo-modified graphene oxide layers. The removal of organic molecules through the thermal decomposition generates porous heterostructures with very high surface areas (≥ 500 m2/g), which are very attractive for potential use in diverse applications such as catalysis, adsorption and as fillers in polymer nanocomposites. The final hybrid products were characterized by X-ray diffraction, Fourier transform infrared and X-ray photoelectron spectroscopies, thermogravimetric analysis, scanning electron microscopy and porosity measurements. As proof of principle, the porous heterostructure with the maximum surface area was chosen for investigating its CO2 adsorption properties.

Transport Properties and Mechanical Features of Sulfonated Polyether Ether Ketone/Organosilica Layered Materials Nanocomposite Membranes for Fuel Cell Applications.

In this work, we study the preparation of new sulfonated polyether ether ketone (sPEEK) nanocomposite membranes, containing highly ionic silica layered nanoadditives, as a low cost and efficient proton exchange membranes for fuel cell applications. To achieve the best compromise among mechanical strength, dimensional stability and proton conductivity, sPEEK polymers with different sulfonation degree (DS) were examined. Silica nanoplatelets, decorated with a plethora of sulfonic acid groups, were synthesized through the one-step process, and composite membranes at 1, 3 and 5 wt% of filler loadings were prepared by a simple casting procedure. The presence of ionic layered additives improves the mechanical strength, the water retention capacity and the transport properties remarkably. The nanocomposite membrane with 5% wt of nanoadditive exhibited an improvement of tensile strength almost 160% (68.32 MPa,) with respect to pristine sPEEK and a ten-times higher rate of proton conductivity (12.8 mS cm-1) under very harsh operative conditions (i.e., 90 °C and 30% RH), compared to a filler-free membrane. These findings represent a significant advance as a polymer electrolyte or a fuel cell application.

Development of Effective Lipase-Hybrid Nanoflowers Enriched with Carbon and Magnetic Nanomaterials for Biocatalytic Transformations.

In the present study, hybrid nanoflowers (HNFs) based on copper (II) or manganese (II) ions were prepared by a simple method and used as nanosupports for the development of effective nanobiocatalysts through the immobilization of lipase B from Pseudozyma antarctica. The hybrid nanobiocatalysts were characterized by various techniques including scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The effect of the addition of carbon-based nanomaterials, namely graphene oxide and carbon nanotubes, as well as magnetic nanoparticles such as maghemite, on the structure, catalytic activity, and operational stability of the hybrid nanobiocatalysts was also investigated. In all cases, the addition of nanomaterials during the preparation of HNFs increased the catalytic activity and the operational stability of the immobilized biocatalyst. Lipase-based magnetic nanoflowers were effectively applied for the synthesis of tyrosol esters in non-aqueous media, such as organic solvents, ionic liquids, and environmental friendly deep eutectic solvents. In such media, the immobilized lipase preserved almost 100% of its initial activity after eight successive catalytic cycles, indicating that these hybrid magnetic nanoflowers can be applied for the development of efficient nanobiocatalytic systems.

Scalable Synthesis of Switchable Assemblies of Gold Nanorod Lyotropic Liquid Crystal Nanocomposites.

A new class of solvent free, lyotropic liquid crystal nanocomposites based on gold nanorods (AuNRs) with high nanorod content is reported. Application of shear results in switchable, highly ordered alignment of the nanorods over several centimeters with excellent storage stability for months. For the synthesis, AuNRs are surface functionalized with a charged, covalently tethered corona, which induces fluid-like properties. This honey-like material can be deposited on a substrate and a high orientational order parameter of 0.72 is achieved using a simple shearing protocol. Switching shearing direction results in realignment of the AuNRs. For a film containing 75 wt% of AuNRs the alignment persists for several months. In addition to the lyotropic liquid crystal characteristics, the AuNRs films also exhibit anisotropic electrical conductivity with an order of magnitude difference between the conductivities in direction parallel and perpendicular to the alignment of the AuNRs.

Nanocomposites of polystyrene-b-poly(isoprene)-b-polystyrene triblock copolymer with clay-carbon nanotube hybrid nanoadditives.

Polystyrene-b-polyisoprene-b-polystyrene (PS-b-PI-b-PS), a widely used linear triblock copolymer of the glassy-rubbery-glassy type, was prepared in this study by anionic polymerization and was further used for the development of novel polymer nanocomposite materials. Hybrid nanoadditives were prepared by the catalytic chemical vapor deposition (CCVD) method through which carbon nanotubes were grown on the surface of smectite clay nanolayers. Side-wall chemical organo-functionalization of the nanotubes was performed in order to enhance the chemical compatibilization of the clay-CNT hybrid nanoadditives with the hydrophobic triblock copolymer. The hybrid clay-CNT nanoadditives were incorporated in the copolymer matrix by a simple solution-precipitation method at two nanoadditive to polymer loadings (one low, i.e., 1 wt %, and one high, i.e., 5 wt %). The resulting nanocomposites were characterized by a combination of techniques and compared with more classical nanocomposites prepared using organo-modified clays as nanoadditives. FT-IR and Raman spectroscopies verified the presence of the hybrid nanoadditives in the final nanocomposites, while X-ray diffraction and transmission electron microscopy proved the formation of fully exfoliated structures. Viscometry measurements were further used to show the successful incorporation and homogeneous dispersion of the hybrid nanoadditives in the polymer mass. The so prepared nanocomposites exhibited enhanced mechanical properties compared to the pristine polymer and the nanocomposites prepared by conventional organo-clays. Both tensile stress and strain at break were improved probably due to better interfacial adhesion of the clay-CNT hybrid of the flexible rubbery PI middle blocks of the triblock copolymer matrix.

Graphene-based nafion nanocomposite membranes: enhanced proton transport and water retention by novel organo-functionalized graphene oxide nanosheets.

Novel nanostructured organo-modified layered materials based on graphene oxide carrying various hydrophilic functional groups (-NH(2), -OH, -SO(3)H) are prepared and tested as nanofillers for the creation of innovative graphene-based Nafion nanocomposites. The hybrid membranes are characterized by a combination of analytical techniques, which show that highly homogeneous exfoliated nanocomposites are created. The pulsed field gradient NMR technique is used to measure the water self-diffusion coefficients. Remarkable behavior at temperatures up to 140 °C is observed for some composite membranes, thereby verifying the exceptional water retention property of these materials. Dynamic mechanical analysis shows that hybrid membranes are much stiffer and can withstand higher temperatures than pure Nafion.

Effective improvement of water-retention in nanocomposite membranes using novel organo-modified clays as fillers for high temperature PEMFCs.

Toward an enhanced water-retention of polymer electrolyte membranes at high temperatures, novel organo-modified clays were prepared and tested as fillers for the creation of hybrid Nafion nanocomposites. Two smectite clays (Laponite and montmorillonite), with different structural and physical parameters, were loaded with various cationic organic molecules bearing several hydrophilic functional groups (-NH(2), -OH, -SO(3)H) and incorporated in Nafion by solution intercalation. The resulted hybrid membranes were characterized by a combination of powder X-ray diffraction, FTIR spectroscopy, and thermal analysis (DTA/TGA) showing that highly homogeneous exfoliated nanocomposites were created where the individual organoclay layers are uniformly dispersed in the continuous polymeric matrix. In this paper, water-transport properties were investigated by NMR spectroscopy, including pulsed-field-gradient spin-echo diffusion and spectral measurements conducted under variable temperature. Organo-montmorillonite nanofillers demonstrate a considerable effect on the Nafion polymer in terms both of water absorption/retention and water mobility with a remarkable behavior in the region of high temperatures (100-130 °C), denoting that the surface modifications of this clay with acid organic molecules significantly improve the performance of the final composite membrane. (1)H NMR spectral analysis allowed a general description of the water distribution in the system and an estimation of the number of water molecules involved in the hydration shell of the sulfonic groups as well as that absorbed on the organoclay particles.

Physicochemical study of amino-functionalized organosilicon cubes intercalated in montmorillonite clay: H-binding and metal uptake.

Two organic-modified montmorillonite clays were prepared by embedding organosilanes bearing different chelating amino-functional groups [Apteos] (3-amino-propyltriethoxysilane), and [Edaptmos] (3-(2-aminoethylamino)propyltrimethoxysilane), in the interlayer space of a Zenith montmorillonite. XRD and FTIR spectroscopic data show that the amino organosilanes are intercalated into the interlamelar space forming cube-like structures bearing one polymanino tail at each cube apex. The intercalated cubes cause an increase of the interlayer spacing of the clay sheets by 6.6 A in [Zenith-Apteos] and by 7.1 A in [Zenith-Edaptmos]. The H-binding properties of the intercalated polyamino organosilanes were studied by potentiometric titration. The Cu-, Cd-, and Pb-binding capacity of [Zenith-Apteos] and [Zenith-Edaptmos] were evaluated in aqueous solution as a function of the pH. Both [Zenith-Apteos] and [Zenith-Edaptmos] showed improvement vs Zenith for metal binding in the order Cu > Pb > Cd. [Zenith-Edaptmos] showed the most important results vs Zenith. Theoretical analysis of the pH edge, achieved by a surface complexation model, shows that (a) the amino-functionalized cube-like structures constitute high affinity metal-binding sites; and (b) the metal ions are bound in a monodendate mode with the amino group of the cube, thus resulting in a maximization of metal-binding efficiency.