Inorganic Domains Research Articles

Enhanced performance of electrospun PVDF membranes modified with rare-earth metal oxides for membrane distillation: A systematic study

In the presented studies, the novel type of separation materials dedicated to membrane distillation was generated and systematically analyzed. Utilizing poly(vinylidene fluoride) (PVDF) electrospun membranes as a base, hybrid organic-inorganic materials were developed to enhance performance. These materials exhibited high hydrophobicity, featuring superhydrophobicity on a micro-scale due to fractal-like structures on the inorganic domain surface. Rare-earth metal oxides (REMO) were implemented for the first time as smart modifiers, covalently attached to the functionalized membrane surface. Three REMO types were selected to investigate their impact on membrane performance in air-gap membrane distillation (AGMD) for the desalination process. Chemical attachment via long enough linkers formed a flexible active surface structure, facilitating transport and separation. Dynamic goniometric studies evaluated membrane wetting stability. Particularly noteworthy was the membrane enhanced with Ho2O3 particles, with high flux and salt rejection rates of 14.41 ± 1.35 kg m−2 h−1 and >99.5 %, respectively. The membrane stability and affinity were further examined using Hansen Solubility Parameters and Pearson's hard–soft acid–base (HSAB) theory. The potential of the hybrid membranes is seen not only in desalination. With the ability to control surface properties by using different silane linkers, oleophobicity/oleophilicity can be achieved, and practical use in wastewater treatment or oil/water separation is possible.

Geometric Analysis of Free and Accessible Volume in Atmospheric Nanoparticles.

Computer-generated atomistic microstructures of atmospheric nanoparticles are geometrically analyzed using Delaunay tessellation followed by Monte Carlo integration to compute their free and accessible volume. The nanoparticles studied consist of cis-pinonic acid (a biogenic organic aerosol component), inorganic ions (sulfate and ammonium), and water. Results are presented for the free or unoccupied volume in different domains of the nanoparticles and its dependence on relative humidity and organic content. We also compute the accessible volume to small penetrants such as water molecules. Most of the free volume or volume accessible to a penetrant as large as a water molecule is located in the domains occupied by organics. In contrast, regions dominated by inorganics do not have any cavities with sizes larger than 1 Å. Solid inorganic domains inside the particle are practically impermeable to any small molecule, thereby offering practically infinite resistance to diffusion. A guest molecule can find diffusive channels to wander around within the nanoparticle only through the aqueous and organic-rich domains. The largest pores are observed in nanoparticles with high levels of organic mass and low relative humidity. At high relative humidity, the presence of more water molecules reduces the empty space in the inner domains of the nanoparticle, since areas rich in organic molecules (which are the only ones where appreciable pores are found) are pushed to the outer area of the particle. This, however, should not be expected to affect the diffusive process as transport through the aqueous phase inside the particle will be, by default, fast due to its fluid-like nature.

Nanofibrous hybrid scaffolds based on PCL-borosilicate system by a green sol-gel process

Tissue regeneration is yet a critical issue, and to mimic the natural extracellular matrix (ECM) innovative scaffolds need to be developed to ensure the functional and safe repair of the damaged organs or tissues. Hybrid biomaterials based on the combination of a biodegradable polymer and bioactive glasses (BGs) are potential candidates for tissue engineering (TE), since they exhibit tailored physical, biological, and mechanical properties, as well as controlled degradation behavior. Thus, the main purpose of this research was to develop by electrospinning (ES) a hybrid nanofibrous membrane composed of a synthetic polymeric matrix (PCL) and a boron and calcium silicate glass, formed via in situ sol-gel, and based on a non-aqueous and green fabrication route. Formic acid (FA) and glacial acetic acid (AA) were used as green solvents to dissolve the PCL. Different compositions were prepared: neat PCL and PCL/SiO2–B2O3–CaO with different sol-gel aging times and green solvent systems. All prepared hybrid solutions, except the composition with only AA, were spinnable. Structural features of the hybrids were assessed by ATR-FTIR spectroscopy, which confirmed the presence of siloxane (Si–O–Si) bonds of silica and carbonyl (CO) bonds characteristic of PCL polymer as well as intermolecular hydrogen-bonding interactions between the carbonyls of PCL and the silanol hydroxyls (Si–OH) of silica networks. Boron (B–O–B) and borosiloxane (B–O–Si) bonds were not visible due to the overlapping of PCL bands in the spectra. Only the solid state 11B NMR technique allowed to find peaks assigned to trigonal BO3 and tetrahedral BO4 groups, which evidence the boron linkages to silica. Thermal analysis showed a change in the crystallinity of PCL with the incorporation of inorganic domains, confirming the formation of chemical interactions between the polymer and the inorganic part. Microstructure and chemical analysis, by SEM/EDS, showed a homogenous distribution of Ca and Si elements into the fibers, as well as an increase of the fiber diameter with the incorporation of boron and calcium silicate glass in the PCL. The developed compositions of PCL/boron and calcium-containing silicate were feasible to electrospin into fibrous meshes, proving its potential for further design of multicomponent nanofibrous microstructures closer to extra cellular matrix architectures.

Tuning Polymer/TiO2 Nanocomposites Morphology by In Situ Non-Hydrolytic Sol-Gel Syntheses in Viscous Polymer Medium: Influence of the Polymer Nature and Oxygen Donor.

Herein, we reported the synthesis of TiO2 through different non-hydrolytic sol-gel (NHSG) routes in viscous polymer media. For the first time, the influence of the polymer nature (Polystyrene (PS) or Polypropylene (PP)) on the morphology of synthesized inorganic domains was investigated. The non-hydrolytic sol-gel reactions between titanium isopropoxide Ti(OiPr)4 and acetic anhydride in molten polypropylene lead to the formation of microfillers with a mean diameter of about 1 μm, while the same synthesis carried out in viscous polystyrene lead to the formation of nanofillers with diameter lower than 10 nm forming aggregates of approximately 200 nm. We have also investigated the influence of the oxygen donor nature on the morphology of synthesized fillers using aromatic oxygen donors in a polystyrene matrix. The use of benzoic anhydride or acetophenone as oxygen donors with Ti(OiPr)4 in viscous polystyrene lead to respectively platelet-like morphology or aggregated nanofillers. We demonstrated that the affinity between polymer, reactants, and/or by-products had an influence on the morphology and the size of in situ synthesized TiO2 fillers. These results evidenced for the first time the possibility to control and to tune the morphology of in situ grown inorganic objects through the NHSG process by the appropriate choice of solvent, here a viscous polymer medium, and reactants.

The Phoenix Complex

The Phoenix Complex

The Co-Transport of PFAS and Cr(VI) in porous media

PFAS and Cr are present at some sites as co-contaminants. The objective of this research was to investigate the co-transport behavior of per- and polyfluoroalkyl substances (PFAS) and hexavalent chromium (Cr(VI)) in porous media. Miscible-displacement experiments were conducted using two soils and an aquifer sediment with different geochemical properties. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were employed as model PFAS. The retardation of PFOS was decreased in the presence of Cr(VI). Conversely, the transport and retardation of PFOA was not affected by the presence of Cr(VI). The reduction of PFOS retardation caused by Cr(VI) is likely due to sorption competition for both organic-carbon and inorganic (metal-oxides and clay minerals) domains. The relative contributions of the three soil constituents to PFOS sorption and the potential for competition between PFOS and Cr(VI) is a function of the geochemical composition of the porous media (i.e., organic carbon, metal-oxides and clay minerals). The PFAS had minimal impact on the retention and transport of Cr(VI). To our knowledge, the results presented herein represent the first reported data for PFOS and Cr(VI) co-transport in porous media. The results of this study indicate that the presence of Cr(VI) has the potential to increase the migration potential of PFOS in soil and groundwater, which should be considered when characterizing electroplating facilities, leather tanning facilities, and other co-contaminated sites.

Organic metal-free halide perovskites tuned up for X-ray detection

X-ray detectors are conventionally in the inorganic domain, but all-organic metal-free halide perovskites (O-PVSK) have also entered the scene recently. Now, a comprehensive study by Cui et al. unveils how halide anions influence the O-PVSK, guiding future efforts to building high-performance organic X-ray detectors.

Non-hydrolytic sol–gel synthesis of polypropylene/TiO2 composites by reactive extrusion

An original way to synthesise polypropylene/titanium dioxide (PP/TiO2) composites combining non-hydrolytic sol–gel chemistry and reactive extrusion was reported. The non-hydrolytic sol–gel reaction between titanium alkoxide as a titanium dioxide precursor and an acid anhydride as an oxygen donor at 240 °C was first evaluated and optimised in an alkane liquid medium. TiO2 was present essentially in crystalline anatase form when synthesised in squalane with a domain size around 10 nm. Based on these encouraging results, the synthesis was adapted to reactive extrusion that means at high temperature in molten viscous polypropylene and for short reaction times (few minutes maximum). The proof of concept was evidenced through the formation of amorphous TiO2-based inorganic domains of size around 1 µm within the polymer matrix from the reaction between titanium isopropoxide and acetic anhydride. A condensation degree of 79% was obtained. To optimise the polymer/filler interface, titanium dioxide precursors and oxygen donors with different alkyl chain lengths were evaluated. Hexanoic anhydride as substituent of acetic anhydride and titanium tetrakis 2-ethylhexyloxide as substituent of titanium isopropoxide were used. The oxygen donor contribution appeared to be dominant for the particle dispersion state. The polypropylene (PP)/TiO2 composite synthesised from the reaction between titanium isopropoxide and hexanoic anhydride showed the narrowest TiO2 particle diameter distribution with a mean particle size around 700 nm.

Calcium phosphate nanocomposites via in situ mineralization in block copolymer hydrogels

Significant research has been directed toward producing composites that mimic the micro‐ to nanoscale structure of bone tissue, and it remains a challenge to develop synthetic strategies to create cost‐effective biocomposite materials with nanoscale inorganic domains. In this paper, we report the synthesis of nanocrystalline calcium phosphate minerals in situ in gels of a commercially available block copolymer, Pluronic F127 (F127). Although solutions of F127 have previously been explored as a templating agent for calcium phosphate mineralization, here we demonstrate the synthesis of nano‐sized calcium hydrogen phosphate hydrate directly in F127 gels. Composites formed at pH 7 contained highly crystalline, millimeter‐scale crystals of brushite, while composites created at an initial pH of 11 contained nanoscale particles of a calcium hydrogen phosphate hydrate similar to natural bone apatite in morphology and size, with a mean particle diameter of 120 nm. The in situ composites have storage moduli of 15–25 kPa, which is comparable to mechanically processed hydrogel composites containing four times more inorganic material. We believe that our synthetic strategy may provide a new class of versatile and cost‐effective nanostructured biomaterials for use in understanding and replicating mineralized tissues.

Gold-Speckled SPION@SiO2 Nanoparticles Decorated with Thiocarbohydrates for ASGPR1 Targeting: Towards HCC Dual Mode Imaging Potential Applications.

Efforts are made to perform an early and accurate detection of hepatocellular carcinoma (HCC) by simultaneous exploiting multiple clinically non-invasive imaging modalities. Original nanostructures derived from the combination of different inorganic domains can be used as efficient contrast agents in multimodal imaging. Superparamagnetic iron oxide nanoparticles (SPIONs) and Au nanoparticles (NPs) possess well-established contrasting features in magnetic resonance imaging (MRI) and X-ray computed tomography (CT), respectively. HCC can be targeted by using specific carbohydrates able to recognize asialoglycoprotein receptor 1 (ASGPR1) overexpressed in hepatocytes. Here, two different thiocarbohydrate ligands were purposely designed and alternatively conjugated to the surface of Au-speckled silica-coated SPIONs NPs, to achieve two original nanostructures that could be potentially used for dual mode targeted imaging of HCC. The results indicated that the two thiocarbohydrate decorated nanostructures possess convenient plasmonic/superparamagnetic properties, well-controlled size and morphology and good selectivity for targeting ASGPR1 receptor.

Thiophene Cation Intercalation to Improve Band-Edge Integrity in Reduced-Dimensional Perovskites.

The insertion of large organic cations in metal halide perovskites with reduced-dimensional (RD) crystal structures increases crystal formation energy and regulates the growth orientation of the inorganic domains. However, the power conversion performance is curtailed by the insulating nature of the bulky cations. Now a series of RD perovskites with 2-thiophenmethylammonium (TMA) as the intercalating cation are investigated. Compared with traditional ligands, TMA demonstrates improved electron transfer in the inorganic framework. TMA modifies the near-band-edge integrity of the RD perovskite, improving hole transport. A power conversion efficiency of 19 % is achieved, the highest to date for TMA-based RD perovskite photovoltaics; these TMA devices provide a 12 % relative increase in PCE compared to control RD perovskite devices that use PEA as the intercalating ligand, a result of the improved charge transfer from the inorganic layer to the organic ligands.

Thiophene Cation Intercalation to Improve Band‐Edge Integrity in Reduced‐Dimensional Perovskites

AbstractThe insertion of large organic cations in metal halide perovskites with reduced‐dimensional (RD) crystal structures increases crystal formation energy and regulates the growth orientation of the inorganic domains. However, the power conversion performance is curtailed by the insulating nature of the bulky cations. Now a series of RD perovskites with 2‐thiophenmethylammonium (TMA) as the intercalating cation are investigated. Compared with traditional ligands, TMA demonstrates improved electron transfer in the inorganic framework. TMA modifies the near‐band‐edge integrity of the RD perovskite, improving hole transport. A power conversion efficiency of 19 % is achieved, the highest to date for TMA‐based RD perovskite photovoltaics; these TMA devices provide a 12 % relative increase in PCE compared to control RD perovskite devices that use PEA as the intercalating ligand, a result of the improved charge transfer from the inorganic layer to the organic ligands.

Surface Properties of Structure-Controlled Silica Films Prepared Using Organic-Inorganic Hybrid Solutions

Silica films with various microstructures were fabricated using organic-inorganic (O-I) hybrid solutions containing a mixture of silica sols, polymethylmethacrylate (PMMA), and urethane acrylate nonionomer (UAN) as an amphiphilic polymer, The O-I hybrid solutions were prepared with various UAN:PMMA and polymer/solvent ratios, then spin-coated on glass and calcinated at 450 °C to produce silica films with various microphase-separated structures. For higher UAN and PMMA concentrations, the silica films showed spherical inorganic domains dispersed over the surface, while many pores were formed in the films with lower polymer contents (observed using scanning electron microscopy). The surface hydrophobicity of the silica films was determined using water contact angle measurements. After surface modification using (1H, 1H, 2H, 2H-perfluorooctyl)trichlorosilane solution, the hydrophobicity of films with a highly microphase-separated structure increased significantly, and all surface-modified films showed increasing hydrophobicity with increasing polymer content. Furthermore, pencil scratch hardness tests showed that the silica films formed on glass substrates could withstand the 5H scratch, test even after surface modification.

Efficient optimization of natural resonance theory weightings and bond orders by gram-based convex programming.

We describe the formal algorithm and numerical applications of a novel convex quadratic programming (QP) strategy for performing the variational minimization that underlies natural resonance theory (NRT). The QP algorithm vastly improves the numerical efficiency, thoroughness, and accuracy of variational NRT description, which now allows uniform treatment of all reference structures at the high level of detail previously reserved only for leading "reference" structures, with little or no user guidance. We illustrate overall QPNRT search strategy, program I/O, and numerical results for a specific application to adenine, and we summarize more extended results for a data set of 338 species from throughout the organic, bioorganic, and inorganic domain. The improved QP-based implementation of NRT is a principal feature of the newly released NBO 7.0 program version. © 2019 Wiley Periodicals, Inc.

Resonance Theory Reboot.

What is now called "resonance theory" has a long and conflicted history. We first sketch the early roots of resonance theory, its heritage of diverse physics and chemistry conceptions, and its subsequent rise to reigning chemical bonding paradigm of the mid-20th century. We then outline the alternative "natural" pathway to localized Lewis- and resonance-structural conceptions that was initiated in the 1950s, given semi-empirical formulation in the 1970s, recast in ab initio form in the 1980s, and successfully generalized to multi-structural "natural resonance theory" (NRT) form in the 1990s. Although earlier numerical applications were often frustrated by the ineptness of then-available numerical solvers, the NRT variational problem was recently shown to be amenable to highly efficient convex programming methods that yield provably optimal resonance weightings at a small fraction of previous computational costs. Such convexity-based algorithms now allow a full "reboot" of NRT methodology for tackling a broad range of chemical applications, including the many familiar resonance phenomena of organic and biochemistry as well as the still broader range of resonance attraction effects in the inorganic domain. We illustrate these advances for prototype chemical applications, including (i) stable near-equilibrium species, where resonance mixing typically provides only small corrections to a dominant Lewis-structural picture, (ii) reactive transition-state species, where strong resonance mixing of reactant and product bonding patterns is inherent, (iii) coordinative and related supramolecular interactions of the inorganic domain, where sub-integer resonance bond orders are the essential origin of intermolecular attraction, and (iv) exotic long-bonding and metallic delocalization phenomena, where no single "parent" Lewis-structural pattern gains pre-eminent weighting in the overall resonance hybrid.

Flux melting of metal-organic frameworks.

Recent demonstrations of melting in the metal-organic framework (MOF) family have created interest in the interfacial domain between inorganic glasses and amorphous organic polymers. The chemical and physical behaviour of porous hybrid liquids and glasses is of particular interest, though opportunities are limited by the inaccessible melting temperatures of many MOFs. Here, we show that the processing technique of flux melting, 'borrowed' from the inorganic domain, may be applied in order to melt ZIF-8, a material which does not possess an accessible liquid state in the pure form. Effectively, we employ the high-temperature liquid state of one MOF as a solvent for a secondary, non-melting MOF component. Differential scanning calorimetry, small- and wide-angle X-ray scattering, electron microscopy and X-ray total scattering techniques are used to show the flux melting of the crystalline component within the liquid. Gas adsorption and positron annihilation lifetime spectroscopy measurements show that this results in enhanced, accessible porosity to a range of guest molecules in the resultant flux melted MOF glass.

Preparation and application of novel bionanocomposite green membranes for gas separation

We report in this study the synthesis of thin-film bionanocomposite (BNC) membranes. In the presented study, at firstly, the synthesis and full characterization of new diamine and polyimide derived from amino acid (methionine) and benzimidazole fractions in the structure of pendant group are presented. Then, to improve the effect of surface modification, TiO2 was predisposed in ethanol via ultrasonic waves. Surface modification of TiO2 was conducted using 3-methacryloxypropyl-trimethoxysilane (MPS) under ultrasonic irradiation. The new BNC-containing chiral monomer (amino acid) is employed as a key monomer for the fabrication of a series of BNCs films with various TiO2 percentages under ultrasonic irradiation. The modified TiO2 presented good compatibility in PI matrix. The structures of the modified hybrid nanocomposites were identified with a FT-IR, whereas the size of the TiO2 in polyimides was characterized with a scanning electron microscope (SEM). SEM results indicated the formation and dispersion of nanometer scale size of inorganic domains inside the polyimide matrix due to the introduction of modified TiO2 and the interactions between organic and inorganic phases. The size of TiO2 particles in the modified system was about 25 nm. The transmission electron microscope analysis showing the well-dispersed nanosized titania NPs. Moreover, their thermal and mechanical properties exhibited a significant improvement. The studies on the optical properties of the hybrid films indicate redshift of the absorption band that increased with increased TiO2 content. The high TiO2, content in PI/TiO2, nanocomposite membranes resulted in the great enhancement of gas separation performance of the TiO2 polyimide nanocomposite materials compared with polyimide. When the TiO2, content in PI/TiO2, composite membranes was above 10 wt%, the permeability of the PI/TiO2 composite membranes was remarkably enhanced and the selectivity of PI/TiO2 composite membranes remained at a high level.

Fabrication and characterization of novel polyester thin‐film nanocomposite membranes achieved by functionalized SiO2 nanoparticles for gas separation

In this article, a new type of soluble polyester/silica (PE/SiO2) hybrid was prepared by the ultrasonic irradiation process. Surface modification of SiO2 was conducted using coupling agent γ‐glycidyloxypropyltrimethoxysilane (GOTMS) under ultrasonic irradiation. The structures of the modified hybrid nanocomposites were identified with a Fourier‐transform infrared spectroscopy (FT‐IR), whereas the size of the SiO2 in PE was characterized with a scanning electron microscope (SEM). SEM results indicated the formation and dispersion of nanometer scale size of inorganic domains inside the PE matrix due to the introduction of modified SiO2 and the interactions between organic and inorganic phases. The size of SiO2 particles in the modified system was about 25 nm. The transmission electron microscope (TEM) analysis showing the well‐dispersed nanosized titania nanoparticles (NPs). The densities and solubilities of the PE/SiO2 hybrids were also measured. Furthermore, thermal stability, residual solvent in the membrane film, and structural ruination of membranes were analyzed by thermal gravimetric analysis (TGA). Moreover, their mechanical properties were also characterized. It can be observed that the Young's moduli (E) of the hybrid films increase linearly with the silica content. The results obtained from gas permeation experiments showed that adding SiO2 to the PE membrane structure increased the permeability of the membranes. POLYM. ENG. SCI., 59:E237–E247, 2019. © 2018 Society of Plastics Engineers

Preparation and evaluation of hybrid organic-inorganic poly(urethane-siloxane) membranes with build-in poly(ethylene glycol) segments for efficient separation of CO2/CH4 and CO2/H2

Organic-inorganic polymer hybrids provide opportunities to tailor new materials for preparation of membranes with improved physico-mechanical and separation properties. This study deals with synthesizing of hybrid organic-inorganic poly(urethane-siloxane) membranes with built-in poly(ethylene glycol) (PEG) segments for CO2 separation. The membranes contain two different PEG content 55 and 71wt% based on the selected starting materials, PEG1000 and PEG2000, respectively. Inorganic siloxane (Si–O–Si) domains were created in the matrix of the membranes through a hydrolysis and condensation reaction. Presence of these inorganic domains improved thermal, mechanical and also separation properties. Separation performance of the poly(urethane-siloxane) membrane with PEG content of 71wt% was completely promising, PCO2 = 104 Barrer, PCO2/PCH4 = 20.8, and PCO2/PH2 = 6.9 at 400kPa and 308K.

Pentablock Ionomer Based TEOS-TIP Hybrid Nanocomposites: Morphology, Physical Properties, and Ion Transport

Nowadays, pure materials cannot embody all the physical, chemical, and mechanical properties required for a given application. Therefore, hybrid inorganic-organic composite materials were created to fill this critical void. The hybrid composites depend not only the properties of individual components, but also on the interfacial interactions between inorganic and organic phases. The significance of this work is to control the interaction-structure-property relationships of hybrid inorganic-organic nanocomposites in many applications such as fuel cells, lithium-ion batteries, biomimetic actuator, and water purification. The PBC based hybrid organic-inorganic films were synthesized based on tetraethylorthosilicate (TEOS), titanium isopropoxide (TIP), and poly(t-butylstyrene-b-hydrogenated isoprene-b-sulfonated styrene-b-hydrogenated isoprene-b-t-butylstyrene) or pentablock copolymer (PBC) via sol-gel chemistry. A ternary phase diagram was estibalished to understand the homogeneity of TEOS-TIP sol-gel system dependent on initial sol composition and reaction conditions leading to controllable materials. All hybrid PBC-TEOS-TIP membranes exhibited higher water uptake than unmodified PBC membranes. Proton conductivity increased 80% from 58 mS/cm for unmodified PBC film to 85 mS/cm for hybrid nanocomposite film due to the role TEOS-TIP within it. This can be attributed to the partial charge transfer from the titanate’s inorganic domains to sulfonate groups that promote acid dissociation and proton attraction. The PBC’s microphase-separated morphology changed from well-ordered lamella-like structure to a random and homogenous distribution of ionic domains with increasing TIP concentration, which was observed from AFM and SAXS results. TGA analyses revealed a decrease in degradation temperature due to titanate's catalytic character, and DMA results demonstrated reduced polymer chain mobility caused by inorganic-organic interactions. Finally, these PBC-TEOS-TIP hybrid composites were used as proton-exchange membranes (PEM) for hygroden fuel cells.