clay and laponite

Clay nanomaterials are an emerging class of 2D biomaterials of interest due to their atomically thin layered structure, charged characteristics, and well-defined composition. Synthetic nanoclays are plate-like polyions composed of simple or complex salts of silicic acids with a heterogeneous charge distribution and patchy interactions. Due to their biocompatible characteristics, unique shape, high surface-to-volume ratio, and charge, nanoclays are investigated for various biomedical applications. Here, a critical overview of the physical, chemical, and physiological interactions of nanoclay with biological moieties, including cells, proteins, and polymers, is provided. The state-of-the-art biomedical applications of 2D nanoclay in regenerative medicine, therapeutic delivery, and additive manufacturing are reviewed. In addition, recent developments that are shaping this emerging field are discussed and promising new research directions for 2D nanoclay-based biomaterials are identified.

Topics: Animals; Biocompatible Materials; Clay; Drug Delivery Systems; Humans; Nanostructures; Polymers; Printing, Three-Dimensional; Proteins; Regenerative Medicine; Silicates; Tissue Engineering; Tissue Scaffolds

Bionanocomposite materials based on clays have been designed for oral administration and controlled release of a neuroprotective drug derivative of 5-methylindole, which had featured an innovative pharmacological mechanism for the treatment of neurodegenerative diseases such as Alzheimer's. This drug was adsorbed in the commercially available Laponite® XLG (Lap). X-ray diffractograms confirmed its intercalation in the interlayer region of the clay. The loaded drug was 62.3 meq/100 g Lap, close to the cation exchange capacity of Lap. Per se toxicity studies and neuroprotective experiments versus the neurotoxin okadaic acid, a potent and selective inhibitor of protein phosphatase 2A (PP2A), confirmed that the clay-intercalated drug did not exert toxicity in cell cultures and provided neuroprotection. Release tests of the hybrid material performed in media mimicking the gastrointestinal tract indicated a drug release in acid medium close to 25 %. The hybrid was encapsulated in a micro/nanocellulose matrix and processed as microbeads, with pectin coating for additional protection, to minimize release under acidic conditions. Alternatively, low density materials based on a microcellulose/pectin matrix were evaluated as orodispersible foams showing fast disintegration times, sufficient mechanical resistance for handling, and release profiles in simulated media that confirmed a controlled release of the encapsulated neuroprotective drug.

Topics: Administration, Oral; Cellulose; Clay; Delayed-Action Preparations; Drug Delivery Systems; Neuroprotective Agents; Pectins

Phosphorus (P), an important macroelement for crops, may be lost into water systems by human activities and subsequently cause serious environmental problems such as eutrophication. Thus, the recovery of P from wastewater is essential. P can be adsorbed and recovered from wastewater using many natural, environmentally friendly clay minerals, however the adsorption ability is limited. Here we applied a synthesis nanosized clay mineral, laponite, to evaluate the P adsorption ability and molecular mechanisms of the adsorption process. We apply X-ray Photoelectron Spectroscopy (XPS) to observe the adsorption of inorganic phosphate onto laponite, and then measure the adsorption content of phosphate by laponite via batch experiments in different solution conditions, including pH, ionic species and concentrations. Then the molecular mechanisms of adsorption are analyzed by Transmission Electron Microscopy (TEM) and molecular modeling using Density Functional Theory (DFT). The results show that phosphate adsorbs to the surface and interlayer of laponite via hydrogen bonding, and the adsorption energies of the interlayer are greater than those of the surface. These bulk solution and molecular-scale results in a model system may provide new insights into the recovery of phosphorus by nanosized clay, with possible environmental engineering applications for P-pollution control and sustainable utilization of P sources.

Topics: Adsorption; Clay; Humans; Minerals; Phosphates; Phosphorus; Wastewater

Epinephrine (EP, also called adrenaline) is a compound belonging to the catecholamine neurotransmitter family. It can cause neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis. This work describes an amperometric sensor for the electroanalytical detection of EP by using an inkjet-printed graphene electrode (IPGE) that has been chemically modified by a thin layer of a laponite (La) clay mineral. The ion exchange properties and permeability of the chemically modified electrode (denoted La/IPGE) were evaluated using multi-sweep cyclic voltammetry, while its charge transfer resistance was determined by electrochemical impedance spectroscopy. The results showed that La/IPGE exhibited higher sensitivity to EP compared to the bare IPGE. The developed sensor was directly applied for the determination of EP in aqueous solution using differential pulse voltammetry. Under optimized conditions, a linear calibration graph was obtained in the concentration range between 0.8 µM and 10 μM. The anodic peak current of EP was directly proportional to its concentration, leading to detection limits of 0.34 μM and 0.26 μM with bare IPGE and La/IPGE, respectively. The sensor was successfully applied for the determination of EP in pharmaceutical preparations. Recovery rates and the effects of interfering species on the detection of EP were evaluated to highlight the selectivity of the elaborated sensor.

Topics: Carbon; Clay; Electrochemical Techniques; Electrodes; Epinephrine; Graphite; Pharmaceutical Preparations

Safe drinking water is a necessity for every human being, but clean water is scarce and not easily available due to natural geochemical factors or industrial pollutant activity. Many issues involving water quality could be greatly improved using clays as adsorbents. We highlight for the first time, the uptake of fluoride from natural water by Laponite, synthetic hectorite clay, in raw and modified state. A series of batch adsorption experiments were carried out to evaluate the adsorption potential of the different parameters. The optimized parameters were: contact time, adsorbent dose and pH. It was found that fluoride uptake from natural water was better using raw Laponite and inorganic-modified Laponite than using organic-modified Laponite clays. Adsorbents were characterized before and after fluoride adsorption by X-ray diffraction, X-ray fluorescence, FTIR, thermo gravimetric analyses and

Topics: Adsorption; Clay; Fluorides; Humans; Silicates; Thermodynamics

Topics: Amines; Carbon; Clay; Electrochemical Techniques; Electrodes; Humans; Quercetin; Silicates

The low quantum efficiency in the solid phase and the highly efficient quenching by oxygen are two major weaknesses limiting the practical applications of triplet-triplet annihilation (TTA) upconversion (UC). Herein, we report an organic-inorganic hybrid nanocomposites fabricated by self-assembly of LAPONITE® clay and poly(

Topics: Clay; Hydrogels; Nanocomposites; Oxygen

Biofabrication is revolutionizing substitute tissue manufacturing. Skeletal stem cells (SSCs) can be blended with hydrogel biomaterials and printed to form three-dimensional structures that can closely mimic tissues of interest. Our bioink formulation takes into account the potential for cell printing including a bioink nanocomposite that contains low fraction polymeric content to facilitate cell encapsulation and survival, while preserving hydrogel integrity and mechanical properties following extrusion. Clay inclusion to the nanocomposite strengthens the alginate-methylcellulose network providing a biopaste with unique shear-thinning properties that can be easily prepared under sterile conditions. SSCs can be mixed with the clay-based paste, and the resulting bioink can be printed in 3D structures ready for implantation. In this chapter, we provide the methodology for preparation, encapsulation, and printing of SSCs in a unique clay-based bioink.

Topics: Biocompatible Materials; Bioprinting; Bone and Bones; Bone Regeneration; Bone Substitutes; Cell Culture Techniques; Cells, Cultured; Clay; Humans; Ink; Microtechnology; Nanocomposites; Printing, Three-Dimensional; Silicates; Stem Cells; Tissue Engineering; Tissue Scaffolds

Unraveling the interaction mechanisms of type I collagen with various inorganic nanoparticles is of pivotal importance to construct collagen-based bionanocomposites with hierarchical structures for biomedical, pharmaceutical, and other industrial applications. In this study, synthetic two-dimensional Laponite nanoplatelets (LAP NPs) are surface-functionalized with tetrakis(hydroxymethyl) phosphonium sulfate (THPS) for reinforcing their incorporation with type I collagen matrix by focusing on the influences of the interactions on the hierarchical structures of the collagen. Our results indicate that the LAP NPs can be successfully surface-functionalized with THPS via covalent bonds between the amine-functionalized NPs and the hydroxymethyl groups of THPS. Moreover, the resulting NPs can be well dispersed into the collagen matrix and evenly bound onto the collagen fiber strands and between the collagen fibrils, preserving the native

Topics: Clay; Collagen Type I; Nanocomposites; Silicates

The extrusion 3D printing of hydrogels has evolved as a promising approach that can be applied for specific tissue repair. However, the printing process of hydrogel scaffolds with high shape fidelity is inseparable from the complex crosslinking strategy, which significantly increases the difficulty and complexity of printing. The aim of this study was to develop a printable hydrogel that can extrude at room temperature and print scaffolds with high shape fidelity without any auxiliary crosslinking during the printing process. To this end, a novel formulation consisting of a Laponite suspension with a high solid concentration and a gelatine methacrylate (GelMA) nanocomposite hydrogel was developed. A homogeneously dispersed high-concentration (up to 20% w/v) Laponite suspension was obtained by stirring at 0 °C. The addition of Laponite with high concentration improved the rheological properties, the degradation stability, and the mechanical strength of the hydrogel. The formulation of 15% (w/v) GelMA and 8% (w/v) Laponite nanocomposite hydrogel exhibited desirable printability and biocompatibility. The GelMA/Laponite hydrogels significantly promoted bone marrow mesenchymal stem cell (BMSC) proliferation and osteogenic differentiation. Both desirable printability under mild conditions and cyto-compatibility enable composite hydrogel a potential candidate as biomaterial inks to be applied for bone tissue regeneration.

Topics: Bone and Bones; Bone Development; Bone Regeneration; Cell Differentiation; Cell Line; Clay; Gelatin; Humans; Materials Testing; Mesenchymal Stem Cells; Methacrylates; Nanogels; Osteogenesis; Printing, Three-Dimensional; Rheology; Silicates

Photo-induced cancer therapies, mainly including photothermal therapy (PTT) and photodynamic therapy (PDT), have attracted numerous attentions owing to the high selectivity, convenience, and few side effects. However, single PTT usually requires high laser power density, and single PDT usually needs a high photosensitizer dosage. Herein, a kind of composite nanocarrier based on clay (laponite)-polypyrrole (LP) nanodisks was synthesized via the in situ polymerization of pyrrole in the interlayer space of laponite. LP composite nanodisks were then coated with polyvinylpyrrolidone (PVP) to form the LP-PVP (LPP) composite nanodisks which show an excellent colloidal stability and in vitro and in vivo biocompatibility. The interlayer space of LPP can be further used for the loading of Chlorin e6 (Ce6), with an ultrahigh loading capacity of about 89.2%. Furthermore, the LPP nanocarrier can enhance the PDT effect of Ce6 under the irradiation of a 660 nm laser, through enhancing its solubility and cellular uptake amount. Besides, it was found that LPP nanodisks exhibit a more outstanding photothermal performance under a 980 nm near-infrared laser (NIR) than a 808 nm NIR laser, with the photothermal conversion efficiency of 45.7 and 27.7%, respectively. The in vitro and in vivo tumor therapy results evidently confirm that the Ce6-loaded LPP nanodisks have a combined tumor PTT and PDT effect, which can significantly suppress the tumor malignant proliferation.

Topics: Clay; Nanoparticles; Photochemotherapy; Photosensitizing Agents; Polymers; Pyrroles; Silicates

Nanoclays have generated interest in biomaterial design for their ability to enhance the mechanics of polymeric materials and impart biological function. As well as their utility as physical cross-linkers, clays have been explored for sustained localization of biomolecules to promote in vivo tissue regeneration. To date, both biomolecule-clay and polymer-clay nanocomposite strategies have utilised the negatively charged clay particle surface. As such, biomolecule-clay and polymer-clay interactions are set in competition, potentially limiting the functional enhancements achieved. Here, we apply specific bisphosphonate interactions with the positively charged clay particle edge to develop self-assembling hydrogels and functionalized clay nanoparticles with preserved surface exchange capacity. Low concentrations of nanoclay are applied to cross-link hyaluronic acid polymers derivatised with a pendant bisphosphonate to generate hydrogels with enhanced mechanical properties and preserved protein binding able to sustain, for over six weeks in vivo, the localized activity of the clinically licensed growth factor BMP-2.

Topics: Animals; Bone Morphogenetic Protein 2; Clay; Diphosphonates; Drug Delivery Systems; Female; Hydrogels; Intercellular Signaling Peptides and Proteins; Materials Testing; Mice; Nanocomposites; Nanoparticles; Polymers; Protein Binding; Silicates

Clays can be synthesised to have specific functional properties, which have been exploited in a range of industrial processes. A key characteristic of clay is the presence of a negatively charged surface, surrounded by an oppositely charged rim. Because of that, clays are able to sequester cationic compounds resulting in the formation of ordered layered structures, known as tactoids. Recent research has highlighted the possibility of utilising clay as a drug delivery compound for cationic peptides. Here, we investigate the process of intercalation by using the highly cationic peptide deca-arginine, and the synthetic clay Laponite, in aqueous suspensions with 2.5 wt% Laponite, and varying peptide concentrations. Small-angle X-ray scattering experiments show that tactoids are formed as a function of deca-arginine concentration in the dispersion, and for an excess of peptide, i.e. above a matched charge-ratio between the peptide and clay, the growth of the tactoids is limited, resulting in tactoidal dissolution. Zeta-potential measurements confirm that the observed dissolution is caused by overcharging of the platelets. By employing coarse-grained molecular dynamics simulations based on the continuum model, we are able to predict the tactoid formation, the growth, and the dissolution, in agreement with experimental results. We propose that the present simulation method can be a useful tool to tune peptide and clay characteristics to optimise and determine the extent of intercalation by cationic peptides of therapeutic interest.

Topics: Cations; Clay; Drug Carriers; Drug Compounding; Molecular Conformation; Molecular Dynamics Simulation; Peptides; Silicates; Static Electricity; Structure-Activity Relationship; Suspensions; Water

Electrically conductive materials that mimic physical and biological properties of tissues are urgently required for seamless brain-machine interfaces. Here, a multinetwork hydrogel combining electrical conductivity of 26 S m

Topics: Acrylic Resins; Bridged Bicyclo Compounds, Heterocyclic; Cell Adhesion; Clay; Electric Conductivity; Humans; Hydrogels; Induced Pluripotent Stem Cells; Nanoparticles; Polymerization; Polymers; Silicates

Obesity is a rapidly growing epidemic, with over one-third of the global population classified as overweight or obese. Consequently, an urgent need exists to develop innovative approaches and technologies that regulate energy uptake, to curb the rising trend in obesity statistics. In this study, nanostructured clay (NSC) particles, fabricated by spray drying delaminated dispersions technologies that regulate energy uptake, to curb the rising trend in obesity statistics. In this study, nanostructured clay (NSC) particles, fabricated by spray drying delaminated dispersions of commercial clay platelets (Veegum® HS and LAPONITE® XLG), were delivered as complimentary, bioactive excipients with the potent lipase inhibitor, orlistat, for the inhibition of fat (lipid) hydrolysis. Simulated intestinal lipolysis studies were performed by observing changes in free fatty acid concentration and revealed that a combinatorial effect existed when NSC particles were co-administered with orlistat, as evidenced by a 1.2- to 1.6-fold greater inhibitory response over 60 min, compared to dosing orlistat alone. Subsequently, it was determined that a multifaceted approach to lipolysis inhibition was presented, whereby NSC particles adsorbed high degrees of lipid (up to 80% of all lipid species present in lipolysis media) and thus physically shielded the lipid-in-water interface from lipase access, while orlistat covalently attached and blocked the lipase enzyme active site. Thus, the ability for NSC particles to enhance the biopharmaceutical performance and potency of orlistat is hypothesised to translate into promising in vivo pharmacodynamics, where this novel approach is predicted to lead to considerably greater weight reductions for obese patients, compared to dosing orlistat alone.

Topics: Aluminum Compounds; Anti-Obesity Agents; Clay; Dietary Supplements; Digestion; Fatty Acids; Humans; Hydrolysis; Intestinal Absorption; Lipase; Lipids; Lipolysis; Magnesium Compounds; Nanoparticles; Obesity; Orlistat; Particle Size; Silicates; Surface Properties

To study the safety and biocompatibility of Laponite clay (LAP) within an intravitreal and suprachoroidal administration in rabbit eyes.. Thirty-two New Zealand albino rabbits were divided into two experimental groups to test intravitreal (IVT group) and suprachoroidal (SCS group) administration of a 100-μl and 50-μl Laponite suspension respectively. Following injection, the eyes were monitored by ocular tonometry, slit-lamp eye examination and indirect ophthalmoscopy, at 24 h, 1, 4, 12, and 14 weeks post administration. Histological examination was also performed to determine whether any ocular pathological change had occurred. Throughout the study, LAP presence in vitreous was estimated by complexometric titration with ethylenediaminetetraacetic acid (EDTA), taking advantage of the Laponite high content of magnesium ions.. Neither significant differences in the intraocular pressure, nor relevant ocular complications were found in the two experimental groups after LAP administration. The histology of the retina remained unchanged. LAP presence in vitreous could be indirectly confirmed by complexometric titration until 14 weeks post administration in eyes of IVT group.. Laponite could be considered as a vehicle for potential clinical use in ocular drug administration, due to its proven ocular biocompatibility and its transparency in gel state.

Topics: Aluminum Silicates; Animals; Biocompatible Materials; Clay; Disease Models, Animal; Electroretinography; Female; Intravitreal Injections; Ophthalmoscopy; Rabbits; Retina; Retinal Diseases; Silicates; Vision, Ocular

Bio-inspired LAPONITE® (clay)-liquid crystal (LC) polymer composite materials with high clay fractions (>80%) and a high level of orientation of the clay platelets, i.e. with structural features similar to the ones found in natural nacre, have been shown to exhibit a promising behavior in the context of reduced oxygen transmission. Key characteristics of these bio-inspired composite materials are their high inorganic content, high level of exfoliation and orientation of the clay platelets, and the use of a LC polymer forming the organic matrix in between the LAPONITE® particles. Each single feature may be beneficial to increase the materials gas barrier property rendering this composite a promising system with advantageous barrier capacities. In this detailed study, LAPONITE®/LC polymer composite coatings with different clay loadings were investigated regarding their oxygen transmission rate. The obtained gas barrier performance was linked to the quality, respective LAPONITE® content and the underlying composite micro- and nanostructure of the coatings. Most efficient oxygen barrier properties were observed for composite coatings with 83% LAPONITE® loading that exhibit a structure similar to sheet-like nacre. Further on, advantageous mechanical properties of these LAPONITE®/LC polymer composites reported previously give rise to a multifunctional composite system.

Topics: Aluminum Silicates; Animals; Biomimetic Materials; Clay; Diffusion; Gases; Materials Testing; Nacre; Oxygen; Permeability; Polymers; Porosity; Silicates

Laponite clay is able to retain dexamethasone by simple physisorption, presumably accomplished by hydrogen bonding formation and/or complexation with sodium counterions, as shown by solid state NMR. The physisorption can be somehow modulated by changing the solvent in the adsorption process. This simple system is able to deliver dexamethasone in a controlled manner to solutions used as models for vitreous humor. The proven biocompatibility of laponite as well as its transparency in the gel state, together with the simplicity of the preparation method, makes this system suitable for future in vivo tests of ophthalmic treatment.

Topics: Adsorption; Aluminum Silicates; Biocompatible Materials; Clay; Dexamethasone; Drug Carriers; Drug Delivery Systems; Humans; Hydrogen Bonding; Magnetic Resonance Spectroscopy; Molecular Structure; Silicates; Sodium; Solvents; Spectrophotometry, Infrared; Static Electricity; Vitreous Body

Early growth response protein 1 (EGR1), as a characteristic example of zinc finger proteins, acts as a transcription factor in eukaryotic cells, mediating protein-protein interactions. Here, a novel electrochemiluminescence (ECL)-based protocol for EGR1 assay was developed with a new eco-friendly emitter: singlet oxygen produced in the vicinity of nanoclay-supported zinc proto-porphyrin IX (ZnPPIX). Its electrochemical reduction stimulates an intense monochromic CL irradiation at 644 nm from the dissolved oxygen as endogenous coreactant in the aqueous solution. This ECL derivation was rationalized via hyphenated spectroscopy and theoretical calculation. To promote hydrophilicity and solid-state immobilization of porphyrins, the lamellar artificial laponite was employed as a nanocarrier owning to its large specific area without the blackbody effect. The facile exfoliation of laponite produced quality monolayered nanosheets and facilitated the adsorption and flattening of PPIX upon the surface, resulting in a highly efficient ECL emission. Based on the release of Zn(2+) in zinc finger domains of EGR1 upon contact with the ECL-inactive PPIX, which was monitored by circular dichroism and UV-absorption, a sensitive Zn(2+)-selective electrode for the "signal-on" detection of EGR1 was prepared with a detection limit down to 0.48 pg mL(-1) and a linearity over 6 orders of magnitude. The proposed porphyrin-based ECL system thus infused fresh blood into the traditional ECL family, showing great promise in bioassays of structural Zn(II) proteins and zinc finger-binding nucleotides.

Topics: Aluminum Silicates; Clay; Early Growth Response Protein 1; Electrochemistry; Electrodes; Kinetics; Limit of Detection; Luminescent Measurements; Metalloporphyrins; Models, Molecular; Nanostructures; Silicates; Singlet Oxygen; Zinc; Zinc Fingers

The spectroscopic behavior of ionic Eu(3+) or Tb(3+) complexes of an aromatic carboxyl-functionalized organic salt as well as those of the hybrid materials derived from adsorption of the ionic complexes on Laponite clay are reported. X-ray diffraction (XRD) patterns suggest that the complexes are mainly adsorbed on the outer surfaces of the Laponite disks rather than intercalated within the interlayer spaces. Photophysical data showed that the energy-transfer efficiency from the ligand to Eu(3+) ions in the hybrid material is increased remarkably with respect to the corresponding ionic complex. The hybrid material containing the Eu(3+) complex shows bright red emission from the prominent (5) D0 →(7) F2 transition of Eu(3+) ions, and that containing the Tb(3+) complex exhibits bright green emission due to the dominant (5) D4 →(7) F5 transition of Tb(3+) ions.

Topics: Aluminum Silicates; Cations; Clay; Coordination Complexes; Europium; Luminescence; Luminescent Agents; Silicates; Terbium; X-Ray Diffraction

A series of Fe/CeO2-intercalated clay catalysts were synthesized successfully, the physicochemical properties of the catalysts were characterized by XRD, BET, XRF, TG, FT-IR, O2-TPD, H2-TPR and XPS methods. The catalytic performances for selective catalytic oxidation of H2S were further investigated, all catalysts exhibited high catalytic activities. Among them 5% Fe/Ce-Lap presented the best activity at 180 degreeC and the maximum sulfur yield was up to 96% due to the interaction between iron and cerium, which improved the redox ability of Fe3+ . Moreover, the strong oxygen adsorption capacity and the well dispersion of iron species improved the catalytic performance efficiently.

Topics: Adsorption; Aluminum Silicates; Catalysis; Cerium; Clay; Hydrogen Sulfide; Intercalating Agents; Iron; Oxidation-Reduction; Silicates

Laponite clays composited with alumina, ceria and zirconia etc. were prepared using polyoxocations or simple metal ions as precursors, and then cobalt oxide was loaded onto them to obtain the catalysts. The results showed that compared with laponite clays, the as-prepared laponite had wide range of pore size distribution and increased pore volume. The pore volumes of laponite clays composited with alumina and ceria were more than 0.75 cm3 · g(-1). N2 isotherm type was maintained after Co3O4 loading, however, the N2 adsorption decreased with the increase of Co3 O4 loading, indicating the decrease of pore volume, which was caused by the blockage of metallic oxide/clay composites support. Furthermore, dispersion and catalytic performance of the catalysts were significantly influenced by the composited metallic elements. It was shown that according to the diffraction peak half-width of 311 crystal facet and scherrer equation, when the Co loading was 21.3% at laponite clays composited with Fe, Zr, Ce, Al, the average sizes of Co3O4 were 17.2, 16.0, 16.5 and 18.0 nm, respectively. Alumina composited clay with 21.3% Co loading showed high catalytic activity, the complete conversion temperature of benzene was 350°C. Among metallic oxide/laponite composites, the ZrO composited laponite with 21.3% Co loading exhibited the best catalytic performance, which could completely convert benzene at 310°C.

Topics: Adsorption; Aluminum Oxide; Aluminum Silicates; Benzene; Catalysis; Cerium; Clay; Cobalt; Hot Temperature; Oxidation-Reduction; Oxides; Silicates; X-Ray Diffraction; Zirconium

A series of iron oxide supported on alumina-intercalated clay catalysts (named Fe/Al-Lap catalysts) with mesoporous structure and high specific surface area were prepared. The structural and chemical properties were studied by nitrogen sorption isotherms, X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis DRS), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FTIR), H₂ temperature-programmed reduction (H₂-TPR) and NH₃ temperature-programmed desorption (NH3-TPD) techniques. It was realized that iron oxide mainly existed in the form of isolated Fe(3+) in an oxidic environment. Fe/Al-Lap catalysts showed high catalytic activities in the temperature range of 120-200 °C without the presence of excessive O₂. This can be attributed to the interaction between iron oxide and alumina, which improve the redox property of Fe(3+) efficiently. In addition, the strong acidity of catalysts and good dispersion of iron oxide were also beneficial to oxidation reaction. Among them, 7% Fe/Al-Lap catalyst presented the best catalytic performance at 180 °C. Finally, the catalytic and deactivation mechanisms were explored.

Topics: Air Pollutants; Aluminum Oxide; Aluminum Silicates; Catalysis; Clay; Environmental Pollutants; Ferric Compounds; Hydrogen Sulfide; Industrial Waste; Industry; Iron; Oxidation-Reduction; Oxygen; Photoelectron Spectroscopy; Silicates; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; Sulfur; Temperature; X-Ray Diffraction

In this article, we present a general overview of the organization of colloidal charged clay particles in aqueous suspension by studying different natural samples with different structural charges and charge locations. Small-angle X-ray scattering experiments (SAXS) are first used to derive swelling laws that demonstrate the almost perfect exfoliation of clay sheets in suspension. Using a simple approach based on geometrical constraints, we show that these swelling laws can be fully modeled on the basis of morphological parameters only. The validity of this approach was further extended to other clay data from the literature, in particular, synthetic Laponite. For all of the investigated samples, experimental osmotic pressures can be properly described by a Poisson-Boltzmann approach for ionic strength up to 10(-3) M, which reveals that these systems are dominated by repulsive electrostatic interactions. However, a detailed analysis of the Poisson-Boltzmann treatment shows differences in the repulsive potential strength that are not directly linked to the structural charge of the minerals but rather to the charge location in the structure for tetrahedrally charged clays (beidellite and nontronites) undergoing stronger electrostatic repulsions than octahedrally charged samples (montmorillonites, laponite). Only minerals subjected to the strongest electrostatic repulsions present a true isotropic to nematic phase transition in their phase diagrams. The influence of ionic repulsions on the local order of clay platelets was then analyzed through a detailed investigation of the structure factors of the various clay samples. It appears that stronger electrostatic repulsions improve the liquidlike positional local order.

Topics: Aluminum Silicates; Biological Products; Clay; Molecular Weight; Osmotic Pressure; Scattering, Small Angle; Silicates; Static Electricity; Suspensions; Water; X-Ray Diffraction

In this paper we report the effect of the incorporation of nano-dimensional clay platelets, laponite, on the J-aggregation of a thiacyanine dye N,N'-dioctadecyl thiacyanine perchlorate (NK) assembled into Langmuir-Blodgett (LB) monolayers. pi-A isotherms and atomic force microscopic studies confirm the successful incorporation of clay platelets into the Langmuir monolayer of NK. J-aggregates of NK remain present in LB films lifted at lower as well as higher surface pressures in the absence of laponite clay platelets. However, with the incorporation of clay platelets, J-aggregates are formed only in LB films lifted at higher surface pressure of 30 mN/m and totally absent in the films lifted at lower surface pressures of 10 and 15 mN/m. This may be due to the formation of nano-trapping level by overlapping of clay platelets at higher surface pressure. NK molecules may get squeezed to these nano-trapping to form J-aggregates.

Topics: Air; Aluminum Silicates; Chloroform; Clay; Coloring Agents; Microscopy, Atomic Force; Nanostructures; Pressure; Silicates; Solutions; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Surface Properties; Temperature; Water

New photo-Fenton catalysts have been prepared from synthetic layered clay laponite (laponite RD). Two series of Fe-laponite catalysts were synthesised, with or without thermal treatment of the mixture Fe polycations-laponite in the intercalation procedure. In each series, the intercalated solids underwent calcination at four temperatures, 250, 350, 450, and 550 degrees C. The catalysts were used for photo-assisted Fenton conversion of phenol, analyzing the influence of five operating factors: the wavelength of the light source (254 nm UV-C and 360 UV-A radiation), the amount of the catalyst (between 0 and 2 g/L), the initial phenol concentration (between 0.5 and 1.5 mmol/L), the initial concentration of hydrogen peroxide (between 20 and 100 mmol/L), and the initial pH of the solution (between 2.5 and 3.5). In all experiments, the temperature was kept constant at 30 degrees C. The results have shown that the almost complete conversion of phenol was possible, after only 5 min, under the following operating conditions: UV-C radiation; a pH of the aqueous solution of 3; a dose of 1 g(catalyst)/L, and a hydrogen peroxide concentration of 50 mmol/L for a solution containing 1 mmol/L of phenol. The catalyst prepared under thermal treatment and calcined at 350 degrees C showed the best catalytic performance. A kinetic model was proposed for the process, testing its validity and estimating the rate constants.

Topics: Aluminum Silicates; Carbon; Catalysis; Clay; Hydrogen Peroxide; Hydrogen-Ion Concentration; Iron; Kinetics; Light; Phenol; Photochemical Processes; Porosity; Silicates; Surface Properties; Temperature; Time Factors; Water; X-Ray Diffraction

The present study aims to describe emulsion particles containing a dispersed phase composed of nanostructured lipid mesophases and stabilized by montmorillonite and/or Laponite clay platelets. The size distributions of these emulsion particles were found independent of the clay mineral content and of the initial internal composition that determines the internal structure. The stabilization of the droplets by a shell of smectite layers was found possible even by montmorillonite which has a length of the same order or more than the droplets to stabilize. The clay platelets give a local flatness to the droplets that may influence the internal structure. In this paper, we describe the conditions to obtain such soft particles of about 220 nm, and we show by direct visualization the internal mesophase complexity and the shape of the particles. In particular, TEM analysis showed elongated particles with bent-back channels at their center but a different morphology at the periphery due to flat border conditions imposed by the presence of the clay minerals.

Topics: Aluminum Silicates; Bentonite; Clay; Emulsions; Freeze Fracturing; Lipids; Microscopy, Electron; Nanostructures; Particle Size; Silicates; X-Ray Diffraction

ABA triblock copolymers in solvents selective for the midblock are known to form associative micellar gels. We have modified the structure and rheology of ABA triblock copolymer gels comprising poly(lactide)-poly(ethylene oxide)-poly(lactide) (PLA-PEO-PLA) through addition of a clay nanoparticle, laponite. Addition of laponite particles resulted in additional junction points in the gel via adsorption of the PEO corona chains onto the clay surfaces. Rheological measurements showed that this strategy led to a significant enhancement of the gel elastic modulus with small amounts of nanoparticles. Further characterization using small-angle X-ray scattering and dynamic light scattering confirmed that nanoparticles increase the intermicellar attraction and result in aggregation of PLA-PEO-PLA micelles.

Topics: Aluminum Silicates; Biocompatible Materials; Clay; Hydrogels; Light; Micelles; Models, Chemical; Models, Molecular; Molecular Conformation; Nanoparticles; Polyesters; Polymers; Rheology; Scattering, Radiation; Silicates; Tissue Engineering

Surface effects on a laponite-exchanged bis(oxazoline)-copper complex modify the stereochemical course of the Mukaiyama aldol reaction between 2-(trimethylsilyloxy)furan and alpha-ketoesters, leading up to 90% ee (dr 86 : 14) becoming the best overall result obtained for this reaction and significantly improving the homogeneous process.

Topics: Alcohols; Aluminum Silicates; Catalysis; Clay; Copper; Cyclization; Ketones; Models, Molecular; Molecular Structure; Organometallic Compounds; Oxazoles; Silicates; Stereoisomerism; Surface Properties