Layered Silicate Clay Research Articles

Cascade Förster resonance energy transfer between layered silicate edge-linked chromophores

Förster resonance energy transfer (FRET) serves as a critical mechanism to study intermolecular interactions and the formation of macromolecular assemblies. Cascade FRET is a multi-step FRET process which can overcome limitations associated with traditional single-step FRET. Herein, a novel organic–inorganic hybrid composed of a nile red derivative attached to the edge of the layered silicate clay Laponite (Lap-NR) was used to facilitate cascade FRET between Laponite sheets. Utilizing naphthalene-diimide edge-modified Laponite (Lap-NDI) as the initial donor, Rhodamine 6G on the basal surface of Laponite as the first acceptor, and Lap-NR as the second acceptor, cascade FRET was achieved. The influence of solvent composition in a DMF/water mixture on cascade FRET was investigated, revealing that a higher water content led to an enhancement of the cascade FRET process, which is attributed to increased aggregation-induced emission of Lap-NDI and the enhanced quantum yield of R6G in water. This study provides a unique approach to achieve cascade FRET by taking advantage of the anisotropic surface chemistry of a two-dimensional nanomaterial, providing a colloidally-driven alternative with improved tunability compared to macromolecular routes. The flexibility and simplicity of this approach will advance the state of the art of organic–inorganic hybrids for applications in optoelectronics, sensors, and hybrid photovoltaics.

Strain rate sensitive polyampholyte hydrogels via well-dispersed XLG sheets

The physical interactions between anionic and cationic monomers and the layered silicate clay mineral Laponite (XLG) have received great attention because of their potential for a variety of applications such as strain sensitive sensors, wearable electronics, drug delivery systems, and tissue engineering applications. A detailed investigation of the interaction between XLG and charged monomers is presented in this article. The study includes the observation of the changes in the viscosity of the solutions and the mechanical performance of the gels at various concentrations by adding XLG to the ionic monomer solution. The ionic interactions between XLG and the charged monomers, driven by electrostatic forces, play a crucial role in gelation and formation of a three-dimensional network, giving the structure strain rate sensitivity. In this way, the addition of XLG nanoparticles not only improves the mechanical properties of the gels, but also gives us information about the microstructure of the mechanical properties that change depending on the strain rate.

Effect of natural organic residues on the adsorption capacity of layered silicate alumina clay

ABSTRACT Layered silicate clay can be modified with organic residues to enhance its adsorption properties and make it suitable for the removal of industrial hazardous substances in various industries. The modification process involves treating the clay with specific organic residues that can interact with and capture the targeted hazardous compounds effectively. Novel nano-composite adsorbing system was developed by inserting the products of powdered certain marine plant within the layers of layered silicate alumina clay (LS) through impregnation technique in order to form layered silicate alumina organic residue (LSOR). The SEM images showed clear agglomerations within the newly formed composite. Moreover, according to data obtained from Scherer equation extracted from XRD data all compounds under investigation were within the nanoscale. The newly prepared LSOR nano-composite showed a significant high adsorption capacity than the main reactants involved in the adsorbent formation process (LS and OR). The effects of various experimental factors were followed up using batch system, and kinetics and isotherms of CR dye adsorption were calculated accordingly. Adsorbent dosage, working temperature, and pH value all have a significant impact on CR removal percentage. Regarding the optimum conditions, the best temperature for CR adsorption onto LSOR is 40°C at a neutral pH medium. Adsorption isotherm study shows that the adsorption process could be followed up using Langmuir adsorption isotherm for OR while it follows Freundlich isotherm for LS adsorbent and can be followed up successfully by Temkin isotherm model in case of LSOR. Finally, field tests revealed that the LSOR nano-catalyst removed mixed dyes from industrial wastewater with a 93% performance. This outcome further solidifies the potential of LSOR nano-adsorbents as an eco-friendly solution for the treatment and reuse of industrial wastewater. It highlights the significant contribution of these new nano-adsorbents in promoting sustainable practices and addressing the challenges associated with industrial wastewater management.

Investigating Solvent-Induced Aggregation in Edge-Functionalized Layered Silicates via All-Atom Molecular Dynamics Simulations.

Molecular dynamics simulations can provide the means to visualize and understand the role of intermolecular interactions in the mechanisms involved in molecular aggregation. Along these lines, simulations can allow the study of how surface chemical modifications can influence nanomaterial assembly at the molecular level. Layered silicate clays have been of significant interest for some time, particularly with regard to their use in organic/inorganic nanocomposites. However, despite numerous reports on the covalent linkage of organic moieties via silanol condensation, the theoretical understanding of these systems has heretofore been limited to noncovalent interactions, specifically ionic interactions at the charged basal surfaces. Herein, a model for edge-functionalized layered aluminosilicate clay, based on the siloxane linkage, is presented. In addition to reproducing experimentally observed degrees of molecular aggregation of clay-linked perylene diimide derivatives with different terminal functional groups as a function of solvent composition, a molecular-level understanding of the role of van der Waals interactions and hydrogen bonding of the different end-groups on the aggregation state in different water/N,N-dimethylformamide mixtures is obtained. The reported model provides a means to simulate organic moieties covalently bound to the layered silicate edge, which will enable future simulations of nanocomposites and organic/inorganic hybrids based on this system.

Novel 2D Layered Manganese Silicate Nanosheets with Excellent Performance for Selective Catalytic Reduction of NO with Ammonia

AbstractTwo‐dimensional (2D) catalysts are highly attractive for their great potential in environment remediation and energy conversion. In this work, a novel layered manganese silicate (MnSiO3) catalyst was synthesized by hydrothermal method using silica in vermiculite, a layered silicate clay mineral, as the lattice‐matching matrix and silicon source. The epitaxial growth of MnSiO3 is confined in the 2D directions, resulting in the morphology of vermiculite crystal thin nanosheets. The physichemical characterization results showed that MnSiO3 possessed higher Mn4+ content, acidic sites and reducing substances than that of MnOx/SiO2. The MnSiO3 therefore exhibited 100 % NO conversion rate with 85 % N2 selectivity at 150 °C in the NH3−SCR process. In situ DRIFTS studies show that MnSiO3 has strong NO adsorption capacity and NH3 activation capacity, which is beneficial to the improvement of NH3−SCR activity.

Layered silicate edge-linked perylene diimides: Synthesis, self-assembly and energy transfer

The control over intermolecular interactions between chromophores at nanomaterial interfaces is important for sensing and light-harvesting applications. To that aim, inorganic nanoparticles with anisotropic shape and surface chemistry can serve as useful supports for organic modification. Herein, novel asymmetric perylene diimides with aspartic acid and oleyl terminal groups were grafted to the edges of the layered silicate clay Laponite, a water-dispersible discoidal nanoparticle. The photophysical properties and solvent-dependent self-assembly of the nanoclay-grafted perylenes were investigated, revealing that the polarity of the terminating ligand dictates the aggregation behavior in aqueous solution, where increased water content generally led to the formation of perylene H-aggregates. The anionic basal surface of the nanoclay provided a binding site for a cationic fluorophore, leading to energy transfer from the face-bound donor to the edge-bound perylene acceptor. This study encourages further research on the use of functional ligands for the formation of organic–inorganic hybrids, particularly where inorganic template particles with specific surface chemistry can be exploited to study intermolecular interactions. Overall, these findings should advance further design and implementation of novel semiconducting ligands towards inorganic–organic hybrids, with potential applications in sensing and energy harvesting.

An Investigative Study on the Progress of Nanoclay-Reinforced Polymers: Preparation, Properties, and Applications: A Review.

Nanoclay-reinforced polymers have attracted considerable universal attention in academic and industrial research due to their outstanding properties and their ever-expanding utilization in diversified applications. In that regard, in the present review, the structure of layered silicate clay, as well as procedures for clay material modification, are outlined. We also discuss the general characterization techniques, synthesis methods, and various properties of polymer–clay nanocomposites (PCNs), and some examples likewise are depicted from the scientific literature. The study’s primary goal is to provide an up-to-date survey of polymer–clay nanocomposites and their specific applications in industries such as automotive, flame-retardant, and biomedical applications, coating, and packaging.

Dynamically vulcanized thermoplastic elastomer nanocomposites based on linear low-density polyethylene/styrene-butadiene rubber/nanoclay/bitumen: morphology and rheological behavior

Dynamically crosslinked thermoplastic elastomer nanocomposites were synthesized as modifier for the bitumen binder-based asphalts. Linear low-density polyethylene (LLDPE) and styrene-butadiene rubber (SBR), with the ratio of 80/20, bitumen, and organically modified clay (OC) were all melt mixed in the presence of the sulfur curing system. The proposed mixing was carried out in an internal mixer at 160 °C with a rotor speed of 120 rpm. To enhance the molecular interactions between the polymer phases and the clay silicate layers, maleic anhydride-grafted LLDPE (PE-g-MA) with the maleiation degree of 50% was also incorporated into the mixture. Observation of the composite samples, using the scanning electron microscopy (SEM), revealed the matrix dispersed type of morphology for all dynamically vulcanized samples. X-ray diffraction (XRD) and transmission electron microscopy (TEM) examinations evidenced the exfoliation of the clay silicate layers with good dispersion. Rheomechanical spectrometry (RMS) was performed on the prepared nanocomposites. All dynamically vulcanized nanocomposites comprising 2.5% of OC exhibited shear-thinning behavior and non-terminal characteristics with a low frequency range. These indicate the formation of three-dimensional physical networks by the clay nanolayers throughout the LLDPE matrix. The presence of the bitumen in the composition of the prepared nanocomposites improved the flowability of the samples. This is a promising feature of the prepared nanocomposites to be used as an elastic and resistant modifier in the composition of the bitumen-based asphalts.

Micromechanical modeling of barrier properties of polymer nanocomposites

Observations in barrier tests on polymer composites with flake-like nanoparticles demonstrate one-step and two-step experimental dependencies of penetrant diffusivity on volume fraction of filler. Conventional models describe the one-step monotonic reduction in the effective diffusivity, but fail to predict the two-step decay. A model is developed for the effective diffusivity of polymer nanocomposites that takes into account clustering of nanoparticles induced by an increase in their content. An advantage of the model is that it (i) predicts both one-step and two-step experimental diagrams in an unified manner, and (ii) involves only two adjustable parameters with transparent physical meaning. The model is applied to the analysis of barrier properties of composites loaded with layered silicate clays, graphene, graphene oxide and reduced graphene oxide, boron nitride and molybdenum disulfide. Good agreement is shown between the experimental data and results of simulation. The influence of polymer matrices, types and chemical modifications of nanoparticles and preparation conditions on aggregation of filler is studied numerically.

Two-Dimensional Layered Zinc Silicate Nanosheets with Excellent Photocatalytic Performance for Organic Pollutant Degradation and CO2 Conversion.

Two-dimensional (2D) photocatalysts are highly attractive for their great potential in environmental remediation and energy conversion. Herein, we report a novel layered zinc silicate (LZS) photocatalyst synthesized by a liquid-phase epitaxial growth route using silica derived from vermiculite, a layered silicate clay mineral, as both the lattice-matched substrate and Si source. The epitaxial growth of LZS is limited in the 2D directions, thus generating the vermiculite-type crystal structure and ultrathin nanosheet morphology with thicknesses of 8-15 nm and a lateral size of about 200 nm. Experimental observations and DFT calculations indicated that LZS has a superior band alignment for the degradation of organic pollutants and reduction of CO2 to CO. The material exhibited efficient photocatalytic performance for 4-chlorophenol (4-CP) degradation and CO2 conversion into CO and is the first example of a claylike 2D photocatalyst with strong photooxidation and photoreduction capabilities.

Two‐Dimensional Layered Zinc Silicate Nanosheets with Excellent Photocatalytic Performance for Organic Pollutant Degradation and CO2 Conversion

AbstractTwo‐dimensional (2D) photocatalysts are highly attractive for their great potential in environmental remediation and energy conversion. Herein, we report a novel layered zinc silicate (LZS) photocatalyst synthesized by a liquid‐phase epitaxial growth route using silica derived from vermiculite, a layered silicate clay mineral, as both the lattice‐matched substrate and Si source. The epitaxial growth of LZS is limited in the 2D directions, thus generating the vermiculite‐type crystal structure and ultrathin nanosheet morphology with thicknesses of 8–15 nm and a lateral size of about 200 nm. Experimental observations and DFT calculations indicated that LZS has a superior band alignment for the degradation of organic pollutants and reduction of CO2 to CO. The material exhibited efficient photocatalytic performance for 4‐chlorophenol (4‐CP) degradation and CO2 conversion into CO and is the first example of a claylike 2D photocatalyst with strong photooxidation and photoreduction capabilities.

Synthesis of chromium pillared clay for adsorption of methylene blue

Synthesis of chromium pillared clay and its application for methylene blue adsorption has been conducted. Chromium pillared clays were prepared through intercalation of chromium polycation in the area between clay silicate layers. Whereas chromium polycation was synthesized by hydrolysis of CrCl3.6H2O solution with NaOH. The intercalated clay then dried and calcined at 200°C for 4 hours. The resulting chromium pillar clay was characterized by X-Ray Diffraction (XRD) and Surface Area Analyser (SAA). Furthermore, natural clays and chromium pillared clay were used as adsorbents for methylene blue adsorption. Chromium pillared clays showed better characteristics than natural clays. Basal spacing increased from 15.08 Å to 16.28 Å, surface area from 41.636 m2/g to 130.555 m2/g, average pore diameter from 30.516 Å to 30.590 Å, and pore volume from 0.067 mL/g to 0.128 mL/g. The adsorption results displayed that the optimum adsorption conditions occurred at pH 2 and there was no significant difference in adsorption ability due to time variation. The optimum efficiency for methylene blue adsorption was at a concentration of 180 ppm for natural clay and of 120 ppm for chromium pillared clay.

Nanoclay incorporation into soy protein/polyvinyl alcohol blends to enhance the mechanical and barrier properties

To enhance the mechanical and water barrier properties of soy protein isolate (SPI/)/polyvinyl alcohol (PVA) blends, montmorillonite (MMT), as a layered silicate clay was incorporated and SPI/PVA/MMT composite films were successfully prepared by melt processing in this work. The results showed that the structure of the composites was highly dependent on the MMT content. MMT nanofillers could act as the heterogeneous nucleating agent for PVA, which accelerated the crystallization and increased the size distribution of the crystalline. With the increase of MMT content, the tensile strength and Young's modulus of the composites increased, exhibiting the fine reinforcing effect. Due to the effective restriction of the highly disordered MMT lamellae on the matrix segment, the water sensitivity of the composites decreased and at the same time, the thermal stability improved. The resulting nanocomposite films exhibited wide applications as biodegradable materials, green packaging films, etc. POLYM. COMPOS., 40:3768–3776, 2019. © 2019 Society of Plastics Engineers

Nano Indendation Hardness Testing Of PP-CNT Composites

Abstract Hardness is an important mechanical property which determines the applicability of polymer composites. Carbon Nano Tubes (CNT) invented by Iijima by arc-discharge technique. It possess some unique properties like Young’s modulus the values varies from 0.42 to 4.15 TPa,tensile strength of 1 TPa, density varies between 1.3 -3 g/cm3 comparatively lower than commercial carbon fibers. CNTs have thermal stability up to 2800°C in vacuum. CNT present in Polypropylene (PP) has good impact on the hardness properties of the composites. Montmorillonite (MMT), a layered silicate clay, has been the focus of extended research for the preparation of polymer nanocomposites.Nano indentation hardness testing had been used to measure the hardness of the PP-CNT, PP-MMT system.

Charge fingerprint in relation to mineralogical composition of Quaternary volcanic ash along a climatic gradient on Java Island, Indonesia

We studied the relationship between the mineralogical composition and surface charge properties of representative Quaternary volcanic ash soils, classified as Andosols, along an East-West sequence on Java Island in Indonesia. The soil charge characteristics were determined using ‘charge fingerprinting’ procedures. Most of the studied soils have a limited ability to retain cations under their forest or grass vegetation. The surface charge properties of these soils are mainly related to allophane and organic matter contents and, to a lesser degree, to ferrihydrite content and layer silicate characteristics. In East Java, the soils are Andosols with low allophane content, dominated either by halloysitic clays or by a mixture of 2:1 and 1:1 layer silicate clays; these soils are characterized by a low to moderate permanent charge. In West Java, the soils are rich in allophane, with subordinate kaolinitic clays, gibbsitic material or a mixture of 1:1 and 2:1 layer silicate clays; in contrast to the allophane-poor soils of East Java, these soils have extreme variable charge characteristics, creating a net ‘positive’ variable surface charge at soil pH. Differences in mineralogical composition of the clay fraction are attributed mainly to more pronounced seasonality in East Java, with variations in parent ash composition, becoming more acidic from east to west, as subordinate factor. The more severely leaching environment in West Java results in a higher degree of desilication, which led to a higher point of zero net charge (PZNC) and pHo in the allophane-rich soils. This study demonstrates how a climatic gradient can affect regional variations in charge properties, through the impact of climate on the mineralogical composition of the clay fraction. Regional patterns of this type must be understood to correctly assess of variations in soil fertility status and to make correct soil management choices for sustainable crop production.

Preparation and characterization of poly(ethylene-vinyl acetate) based nanocomposites using radiation-modified montmorillonite

Polymer/clay nanocomposites were prepared by melt intercalation using torque rheometer. Poly (ethylene-vinyl acetate) (EVA 18) with 18% wt. vinyl acetate was used as polymer, unmodified clay (Na+ montmorillonite, MMT), organo-modified clays I44 P, I31 PS and clays modified by in-situ radiation polymerization of charged monomer were used as the nanofiller. Unmodified clay was interacted with a charged monomer [2-(Methacryloloxy) ethyl]-trimethyl ammonium chloride in presence of water and irradiated to 10 kGy, 20 kGy, 30 kGy to load the clay with polymer. The maximum opening of 2.29 nm between the silicate layers of clay was obtained for 30 kGy irradiated clay as compared to 1.27 nm of untreated clay measured by X-ray diffraction (XRD) analysis. Structures of nanocomposites were characterized by ATR-FTIR, TEM (Transmission Electron Microscopy), XRD (X-Ray Diffraction) and PALS (Positron Annihilation Lifetime Spectroscopy). Close to 50% improvement in E-modulus and Tensile strength values was reached for nanocomposite prepared with 30 kGy irradiated clay, much better that the other nanocomposites except with organomodified clay I31PS all compared in equal loading. The improvement in mechanical as well as thermal properties was explained by structural analysis via XRD, TEM and PALS measurements.

Recent Developments in the Fabrication, Characterization, and Properties Enhancement of Polymer Nanocomposites: A Critical Review

During the last few decades, significant progress in developing polymer nano-composites and their wide scope in extensive engineering applications such as packaging, sports equipment, automobile sector and bio-medical, has been the result of continuous developments in polymer science and nanotechnology. Moreover, the polymer nano-composites can be tailored to meet the widespread engineering accomplishments due to unique combination of mechanical properties, electrical properties, corrosion resistance, thermal stability and high reliability in rigorous environments. The present research study significantly reviews the various theories and models used to fabricate the polymer nano-composites. Furthermore, the paper also emphasizes the impact of nanofillers dispersion on morphology, thermal, water barrier, flame retardant and mechanical properties of nanocomposites. Earlier research unveils that addition of different nano-particle, for instance, carbon nanotubes, nanofibers, layered silicate clays and metallic nanoparticles into thermosetting or thermoplastic polymers acquire high surface area to volume ratio of the spherical nanofiller and high aspect ratio which results in properties enrichment. Therefore, this analysis would discover several key research gaps and to discuss the future scope for the synthesis of advanced polymer nanocomposites with tunable mechanical, thermal and electrical properties.

Structure – Impact properties relationships of carbon fiber reinforced poly(methyl methacrylate) composite

In the present study, the relationships between poly(methyl methacrylate) (PMMA) structure modified by nanoparticles and the impact behavior of carbon fiber (CF) reinforced PMMA (CF/PMMA) thermoplastic nanocomposite were explored. CF/PMMA composite was prepared by nanofiller‐containing methyl methacrylate monomer impregnation of fibers followed by in‐situ polymerization in the mould. Composite matrix PMMA was modified by halloysite, multiwalled carbon nanotubes, and organically modified and unmodified layered silicate clays. The structure of modified PMMA was investigated by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) analysis. SEM results show that nanotubes are uniformly distributed in the PMMA matrix without formation of aggregates. XRD studies of PMMA with layered silicates indicate poor unmodified clay exfoliation in polymer monomer. A low‐velocity impact test was performed and an air‐coupled ultrasonic non‐destructive testing technique was used to size delamination type defects in the composite samples after impact. The impact damage behavior was explained by microstructural parameters of composites obtained by optical microscopy. It was obtained that CF/PMMA composite modified by nanotubes both multiwalled carbon and halloysite absorbs 10 % more energy at the low velocity impact compared to that of unmodified one, due to high interaction of the nanotubes and PMMA. Layered silicate clays adversely affected the composite impact properties compared with unmodified CF/PMMA. Organic modifications of clays slightly improve their dispersion into the monomer, but does not have an observed effect on the impact properties of the composite. POLYM. COMPOS., 40:E333–E341, 2019. © 2017 Society of Plastics Engineers

Metal Nanoparticle Growth within Clay-Polymer Nacre-Inspired Materials for Improved Catalysis and Plasmonic Detection in Complex Biofluids.

Recent studies have shown that layered silicate clays can be used to form a nacre-like bioinspired layered structure with various polymer fillers, leading to composite films with good material strength, gas-barrier properties, and high loading capacity. We go one step further by in situ growing metal nanoparticles in nacre-like layered films based on layered silicate clays, which can be used for applications in plasmonic sensing and catalysis. The degree of anisotropy of the nanoparticles grown in the film can be controlled by adjusting the ratio of clay to polymer or gold to clay and reducing agent concentration, as well as silver overgrowth, which greatly enhances the surface enhanced Raman scattering activity of the composite. We show the performance of the films for SERS detection of bacterial quorum sensing molecules in culture medium, and catalytic properties are demonstrated through the reduction of 4-nitroaniline. These films serve as the first example of seedless, in situ nanoparticle growth within nacre-mimetic materials, and open the path to basic research on the influence of different building blocks and polymeric mortars on nanoparticle morphology and distribution, as well as applications in catalysis, sensing, and antimicrobial surfaces using such materials.

Novel strategic approach for the thermo- and photo- oxidative stabilization of polyolefin/clay nanocomposites

Polyolefin/clay nanocomposites were prepared by melt mixing and their oxidative stability was studied under long-term thermo- and photo-oxidative test conditions in the absence and presence of a modified organo montmorillonite clay (OM-MMt) containing a chemically-bound hindered phenol antioxidant function, (AO)OM-Mt. It was found that nanocomposites based on both polyethylene (PE) and polyethylene-grafted-maleic anhydride (PEgMA) containing the (AO)OM-Mt gave a higher oxidative stability, along with better clay dispersion, compared to analogous PE or PEgMA-based nanocomposites containing an added (free) conventional antioxidant with a similar hindered phenol function (using the commercial hindered phenol Irganox® 1076). These findings can be explained in terms of the ability of the organo-modifier containing the in-built antioxidant function to act locally at the interface between the clay silicate layers and the polymer macromolecules thus contributing to the improved stability of the polymer observed both during long-term thermal- and photo-oxidative treatments.