Engineering new layered solids from exfoliated inorganics: a periodically alternating hydrotalcite-montmorillonite layered hybrid

Simultaneous removing algal and its extracellular organic matters by Mg/Al-layered double hydroxide /La-montmorillonite

Rapid and effective simultaneous removal of algal and extracellular organic matter (EOM) is essential for algal blooms water emergency treatment. In this study, a composite material was prepared by physical and chemical interaction between La-montmorillonite (La-MMT) and Mg/Al-layered double hydroxide (LDHs), and its removal effect of algal and extracellular organic matters (EOM) was investigated. The results showed that the removal rate of chlorophyll a (chl-a) was 96.8% within 2 h when the LDHs/La-MMT2:1 dosage was 1.0 g/L. Three-dimensional fluorescence characteristic spectra and parallel factor analysis showed that the removal of EOM by composite material mainly reflected in the removal of humus-like substances. The reaction heat of composite material for the algal solution was -32.7 J/g. Zeta potential changed from -25.7 mV to -16.9 mV, the main treatment mechanisms of composite material were surface adsorption, complexation precipitation, charge neutralisation, and ion exchange. These findings herein proposed that composite material was a potential and proper treating agent for removing algal cells and EOM from algal blooms water.

Empirical Modeling of Electron Transport in Fe/Ti Layered Double Hydroxide Using Exponential, Gaussian and Mixed Gauss-Exponential Distribution

Fe/Ti-layered double hydroxide (LDH) has been hydrothermally prepared and characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and UV-visible diffuse reflectance spectroscopy for evaluation of its structure, morphology, and optical properties. The purpose of doping Ti⁴⁺ with Fe³⁺ toward the synthesis of Fe/Ti LDH is to extend the absorption of the nanomaterial to longer wavelength, which is known to exhibit higher electron transport performance. To provide a practical realization, electron transport modeling across the band gap has been interpreted using exponential, Gaussian, and mixed Gauss-exponential distribution. The conduction band energy (E _C) has been calculated by using the observed values of band gap (E _g) and ξ-potential of the LDH. A detailed study has been undertaken to investigate the pattern of theoretical density of the LDH on the basis of unknown (E _C = 0) and known (calculated) values of E _C. Fermi-Dirac statistics has been used extensively for estimating the occupancy probability of electron (e^-)-hole (h⁺) pair formation within the valence and conduction bands, respectively, with different temperatures, as well as for given energy levels. Monte Carlo simulations have also been performed to evaluate the suitability of the choice of the model, on the basis of the probability of availability of e^-s within the conduction band. To provide a practical realization of the suggested models, electronic transition across the band gap of Fe/Ti LDH has been extensively investigated.

Structure-controlled Co-Al layered double hydroxides/reduced graphene oxide nanomaterials based on solid-phase exfoliation technique for supercapacitors

High-efficient nanosheets exfoliation and ordered controlled stacking are in urgent need of work for electrochemistry application. Here, we have developed a high-efficient and environmentally-friendly solid-phase method for the exfoliation of Co-Al layered double hydroxide (Co-Al LDH) and graphene oxide (GO). Meanwhile, we found that there is a dynamic structure evolution in the self-assembly process between Co-Al LDH-NS and GO-NS and new theoretical structure models were proposed. With the reduction treatment, the electrochemical test results show that Co-Al LDH/rGO-3 with ideal tiling structure has better electrochemical performance, which provides a specific capacitance of 1492 F g^-1 at 1 A g^-1 and remains the capacitance retention at approximately 94.3% after 5000 cycles. Moreover, an energy density of 44.6 Wh kg^-1 is obtained at a power density of 799.6 W kg^-1. The proposed method and the structure-relationship are practically applicable for other 2D materials in the asymmetric supercapacitors.

Aqueous-phase synthesis of layered double hydroxide nanoplates as catalysts for the oxygen evolution reaction

Transition metal layered double hydroxide (LDH) nanomaterials have been considered as good catalytic materials for various applications; however, there has been a limit in the economic efficiency and convenience of the synthetic method. In this work, we report a facile aqueous-phase route to the synthesis of transition metal LDH nanoplates including Mn-Ni and Zn-Ni. Electrochemical characterization of the synthesized Mn-Ni LDHs with different intercalated halogen anions was carried out for the oxygen evolution reaction (OER) and a Tafel slope of about 80 mV per decade was obtained which is comparable to those of the previously reported LDH nanoplates.

Complex Formation via Hydrogen bonding between Rhodamine B and Montmorillonite in Aqueous Solution

This study investigates the adsorption mechanism differences among four nitrogenous dyes, sulforhodamine G (SRG), uncharged/deprotonated rhodamine B (RhB), orange II (Or II) and methyl blue (MB) by montmorillonite (MMT). MMT adsorption capacity for cationic MB was three times that of uncharged RhB and anionic SRG, while anionic Or II was not absorbed. Colloidal MMT particles have two types of surfaces, basal and edge, that interact with nitrogenous dyes very differently. The surface acidity of MMT was characterized with the pyridine adsorption method using in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS). Adsorption of cationic MB was compared with the adsorption of RhB. In-situ attenuated total reflectance Fourier transform infrared (in-situ ATR-FTIR) spectroscopy indicated that a nitrogen atom on RhB complexes with a metal hydroxyl on an MMT edge through a water bridge. The highly polar edge hydroxyl is important to hydrogen bond formation. Cation ion exchange and washing experiments, as well as studies on the effect of temperature, pH and ionic strength on adsorption further clarified the adsorption mechanism. Our results provide insights into the effects of molecular structure on the adsorption of nitrogenous dyes by clay and the role of edge surfaces in the adsorption process.

Spontaneous assembly of a hybrid crystal-liquid phase in inverse patchy colloid systems

Materials with well-defined architectures are heavily sought after in view of their diverse technological applications. Among the desired target architectures, lamellar phases stand out for their exceptional mechanical and optical features. Here we show that charged colloids, decorated on their poles with two oppositely charged regions possess the unusual ability to spontaneously assemble in different morphologies of (semi-)ordered, layered particle arrangements which maintain their structural stability over a surprisingly large temperature range. This remarkable capacity is related to a characteristic bonding mechanism: stable intra-layer bonds guarantee the formation of planar aggregates, while strong inter-layer bonds favor the stacking of the emerging planar assemblies. These two types of bonds together are responsible for the self-healing processes occurring during the spontaneous assembly. The resulting phases are characterized by parallel, densely packed, particle layers connected by a relatively small number of intra-layer particles. We investigate the properties of the (semi-)ordered phases in terms of static and dynamic correlation functions, focusing in particular on a novel hybrid crystal-liquid phase that prevails at intermediate temperatures where the inter-layer particles form a mobile, fluid phase.

Designing Supported Ionic Liquids (ILs) within Inorganic Nanosheets for CO₂ Capture Applications

A new methodology was developed for the immobilization of ionic liquids (ILs) on α-zirconium phosphate (ZrP) and montmorillonite (MMT) single-layer nanosheets via a facile coassembly process. The coassembled inorganic nanosheet/1-n-butyl-3-methylimidazolium chloride (BMIMCl) hybrids were systematically characterized. The results showed that the ILs were successfully assembled with ZrP or MMT single-layer nanosheets to form an intercalated structure. The inorganic nanosheet/IL hybrids can serve as efficient CO2 absorbents. The CO2 sorption of BMIMCl could be made up to 21 times more efficient because of the high exposure of the functional groups of BMIMCl in the coassembled hybrids. CO2 was physically absorbed by the hybrids with a slow equilibrium time at lower temperatures, whereas higher temperatures allowed for faster diffusion and chemical absorption of CO2. The best CO2 capture capacities of the hybrids were 0.73 mmol/g at 60 °C for ZrP/BMIMCl and 0.42 mmol/g at 70 °C for MMT/BMIMCl.

Energy and structure of bonds in the interaction of organic anions with layered double hydroxide nanosheets: A molecular dynamics study

The application of hybrid and hierarchical nanomaterials based on layered hydroxides and oxyhydroxides of metals is a swiftly progressing field in biomedicine. Layered double hydroxides (LDH) possess a large specific surface area, significant surface electric charge and biocompatibility. Their physical and structural properties enable them to adsorb various kinds of anionic species and to transport them into cells. However, possible side effects resulting from the interaction of LDH with anions of the intercellular and intracellular medium need to be considered, since such interaction can potentially disrupt ion transport, signaling processes, apoptosis, nutrition and proliferation of living cells. In the present paper molecular dynamics is used to determine the energies of interaction of organic anions (aspartic acid, glutamic acid and bicarbonate) with a fragment of layered double hydroxide Mg/Al-LDH. The average number of hydrogen bonds between the anions and the hydroxide surface and characteristic binding configurations are determined. Possible effects of LDH on the cell resulting from binding of protein fragments and replacement of native intracellular anions with delivered anions are considered.

Hemicelluloses/montmorillonite hybrid films with improved mechanical and barrier properties

A facile and environmentally friendly method was introduced to incorporate montmorillonite (MMT) as an inorganic phase into quaternized hemicelluloses (QH) for forming hemicellulose-based films. Two fillers, polyvinyl alcohol (PVA) and chitin nanowhiskers (NCH), were added into the hemicelluloses/MMT hybrid matrices to prepare hybrid films, respectively. The hybrid films were nanocomposites with nacre-like structure and multifunctional characteristics including higher strength and good oxygen barrier properties via the electrostatic and hydrogen bonding interactions. The addition of PVA and NCH could induce changes in surface topography, and effectively enhance mechanical strength, thermal stability, transparency, and oxygen barrier properties. The tensile strengths of the composite films F_PVA(0.3), F_PVA(0.5), and F_NCH(0.8) were 53.7, 46.3, and 50.1 MPa, respectively, which were 171%, 134%, and 153% larger than the F_QH-MMT film (19.8 MPa). The tensile strength, and oxygen transmission rate of QH-MMT-PVA film were better than those of quaternized hemicelluloses/MMT films. Thus, the proper filler is very important for the strength of the hybrid film. These results provide insights into the understanding of the structural relationships of hemicellulose-based composite films in coating and packaging application for the future.