Lateral Bilayer Research Articles

Controllable Photocurrent Generation in Lateral Bilayer MoS2–WS2 Heterostructure

AbstractLaterally epitaxial two‐dimensional (2D) transition metal dichalcogenides (TMDs) heterojunctions are of considerable interest in recent years due to atomically sharp interfaces and tunable band alignment, which have potential applications in novel functional electronics and optoelectronics. However, the studies of 2D lateral heterostructures have mainly focused on the synthesis methods and pristine performance of the fabricated heterojunctions. Herein, the controllable photocurrent generation and enhanced performances of the lateral bilayer (LBL) MoS2–WS2 heterojunctions are reported. A tunable and abrupt built‐in field forms at the interface, and the gate‐tunable rectifying behavior and photovoltaic effect are realized. It is demonstrated that the generation of the photocurrent in the device can be highly controlled to realize ultrahigh responsivity of 1.06 × 104 A W−1 and detectivity of 1.14 × 1013 Jones at a 638 nm incident light. The lateral TMDs heterostructures are expected to constitute the ultimate functional elements of novel electronics and optoelectronics.

A Novel Process for Intercalating Alkylammonium Ions in a Thai Bentonite and its Effect on Adsorption Performance

AbstractThe organization of organic species on the ordered structures of clays and clay minerals is one way to produce inorganic-organic hybrids with controlled microstructures and properties. The reactions of the adsorbed species and their arrangement on the clay surfaces can be guided by the choice of clay and of adsorbed species. The purpose of the present study was to intercalate alkylammonium ions into a Thai bentonite and to study the effect on dye-adsorption efficiency. A series of alkylammonium ions, CnH2n+1NH3+ (n = 8, 10, 12, or 18), was incorporated into the interlayer spaces of a natural bentonite by mixing an aqueous dispersion of bentonite with an aqueous solution of protonated alkylamines at room temperature. The basal spacings of the intercalation compounds varied depending on the alkyl chain lengths and the amount of alkylammonium ions. The alkylammonium ions adsorbed formed lateral monolayer, bilayer, pseudo-trimolecular layer, paraffin-type monolayer, and/or paraffin-type bilayer structures. The adsorption efficiency of alkylammonium-bentonites was determined using batch adsorption experiments of rhodamine 6G from a water-ethanol solution; the greatest efficiency was 87% while that of the bare bentonite was 47%. The loading amount and the arrangement of the intercalated alkylammonium ions in the interlayer spaces, as well as the specific surface area and pore volume, played important roles in the adsorption efficiency of alkylammonium-bentonite. The adsorption equilibrium data for rhodamine 6G on the best adsorbent were interpreted using the Langmuir isotherm model and a pseudo-second order kinetics model. The adsorption efficiency of the adsorbent decreased by only 17% after five runs.

Multimodal Nanoscopic Study of Atomic Diffusion and Related Localized Optoelectronic Response of WS2/MoS2 Lateral Heterojunctions.

The atomic diffusion in transition metal dichalcogenides (TMDs) van der Waals heterojunctions (HJs) strongly modifies their optoelectronic properties in the nanoscale. However, probing such localized properties challenges the spatial resolution and the sensitivity of a variety of analytic tools. Herein, a multimodal nanoscopy (based on tip enhanced Raman spectroscopy (TERS) and photoluminescence (TEPL)) combined with the Kelvin probe force microscopy (KPFM) method was used to probe such nanoscale localized optoelectronic properties induced by atomic diffusion. Chemical vapor deposition (CVD)-grown lateral bilayer (2L) WS2/MoS2 HJs were imaged with a spatial resolution better than 40 nm via TERS and TEPL mapping by using intrinsic Raman and photoluminescence (PL) peaks. The contact potential difference (CPD), capacitance, and PL variation in a nanoscale vicinity of the HJ interface can be correlated to the local stoichiometry variation determined by TERS. The diffusion coefficients of W and Mo were obtained to be ∼0.5 × 10-12 and ∼1 × 10-12 cm2/s, respectively, by using Fick's second law. The obtained results would be useful to further understand the localized optoelectronic response of the TMDs HJs.

The adsorption and mechanism of benzothiazole and 2-hydroxybenzothiazole onto a novel ampholytic surfactant modified montmorillonite: Experimental and theoretical study

A novel ampholytic surfactant (cationic panthenol, CP) modified montmorillonite (CPMMt) was firstly prepared and investigated its removal effect and mechanism for a class of emerging pollutants such as benzothiazole (BTH) and 2-hydroxybenzothiazole (2-OH-BTH) in water. Batch experiments were conducted to probe the effects of various conditions on the adsorption. The results showed CPMMt-1.0 had greater adsorption performance for BTH and 2-OH-BTH than Na-AMt (acidified Na-Mt), and the maximum equilibrium adsorption capacities of CPMMt-1.0 for BTH and 2-OH-BTH were three times that of Na-AMt. Zeta potential analysis, the effect experiments of solution pH combined with Multiwfn wave function program were carried out to inspect the electrostatic interaction. Furthermore, molecular dynamics simulation was applied to investigate the dynamics behavior of cationic panthenol (CP) and BTH or 2-OH-BTH in the interlamellar of montmorillonite. The results demonstrated that CP molecules presented a lateral bilayer structure, which was in good agreement with XRD experimental data, and the interaction between BTH and the surface of montmorillonite was stronger than that of 2-OH-BTH, which implies that the CPMMt-1.0 had better adsorption performance for BTH than 2-OH-BTH, which was consistent with the experimental results. The adsorption mechanism involved electrostatic interaction and hydrophobic partitioning.

Laterally Resolved Small-Angle Scattering Intensity from Lipid Bilayer Simulations: An Exact and a Limited-Range Treatment.

When combined, molecular simulations and small-angle scattering experiments are able to provide molecular-scale resolution of structure. Separately, scattering experiments provide only intermingled pair correlations between atoms, while molecular simulations are limited by model quality and the relatively short time scales that they can access. Their combined strength relies on agreement between the experimental spectra and those computed by simulation. To date, computing the neutron spectra from a molecular simulation of a lipid bilayer is straightforward only if the structure is approximated by laterally averaging the in-plane bilayer structure. However, this neglects all information about lateral heterogeneity, e.g., clustering of components in a lipid mixture. This paper presents two methods for computing the scattering intensity of simulated bilayers with in-plane heterogeneity, enabling a full treatment of both the transverse and lateral bilayer structure for the first time. The first method, termed the Dirac Brush, computes the exact spectra including spurious artifacts resulting from using information from neighboring periodic cells to account for the long-range structure of the bilayer. The second method, termed PFFT, applies a mean-field treatment in the field far from a scattering element, resulting in a correlation range that can be tuned (eliminating correlations with neighboring periodic images), but with computational cost that prohibits obtaining the exact (Dirac Brush) spectra. Following their derivation, the two methods are applied to a coarse-grained molecular simulation of a bilayer inhomogeneity, demonstrating the contributions of lateral correlations to the resulting spectra.

Titania:Graphdiyne nanocomposites for high-performance deep ultraviolet photodetectors based on mixed-phase MgZnO

Approachable graphdiyne (GDY), characterized by discrepancy hybridized carbon atoms of inhomogeneous π-bonding and carbon 2pz overlapping of orbitals, reveals versatility applications. Previously, interfaces high density between different structure materials induce the high response of photodetector, but the ratio of photocurrent to dark current is restricted for either limited materials properties or lattice mismatch when junctions formed. In this work, titania (TiO2) nanocrystals with a rational phase of anatase are encapsulated on GDY particles, further, the TiO2:GDY nanocomposites are synthesized. High specific surface area GDY, as a proper sustaining material optimizes the characters of TiO2 nanocrystals. Then TiO2:GDY nanocomposites cooperate with Mg0.3Zn0.7O (MZO) are mean to fabricate lateral bilayer ultraviolet photodetector. Because of the formed heterojunction between TiO2:GDY nanocomposites and MZO, the ultraviolet photodetector is highly sensitive to deep ultraviolet light, when optical band gap of MZO is as high as 3.8 eV. The responsivity of TiO2:GDY/MZO bilayer photodetector is also increased by more than one order of magnitude to 76 mA W−1 compares to the MZO device without TiO2:GDY nanocomposites while the photocurrent rejection is about three orders of magnitude from 254 nm to 365 nm. Meanwhile, signal-to-noise ratio is calculated as high as 1.5 × 105 in this work.

Efficient inhibition of montmorillonite swelling through controlling flexibly structure of piperazine-based polyether Gemini quaternary ammonium salts

Currently, it remains a great challenge to maintain clay stability in water and prevent shear dispersion of the clay lamellae. Herein, a series of piperazine-based polyether Gemini quaternary ammonium salts (QAs) with different alkyl chains and linker groups were synthesized as the novel intercalator candidates. We established the correlations between their structures and inhibition swelling behavior of montmorillonite (MMT), a representatively hydratable and expansive clay. Upon loading saturated QAs, the lateral bilayer intercalation aligning parallelly to lamella surface was validated by X-ray diffraction (XRD), namely a monolayer adsorption on MMT platelets, agreeing well with Langmuir isotherm model. By combining Fourier transform infrared (FT-IR) spectroscopy and zeta potential, electrostatic attraction and hydrogen bonding were confirmed as the crucial multiple driving forces of adsorption and intercalation. The increased water contact angles (WCAs) demonstrated the formation of protective coating for hindering the entrance of water into the interlayers of MMT. XRD and field emission scanning electron microscope (FE-SEM) indicated that, when the carbon number of “tail” groups in QAs molecules was greater than 12, the platelets of organo-MMT (OMMT) were prone to be exfoliated and aggregated parallelly to sheet surface. This study provides a unique foundation for designing the molecular structure of clay modifier.

Lateral Bilayer MoS2–WS2 Heterostructure Photodetectors with High Responsivity and Detectivity

Abstract2D heterostructures combining different layered semiconductors have received great interest due to their intriguing electrical and optical properties. However, the arbitrary growth of layers in a lateral heterostructure remains a challenge. Here, the synthesis of large‐scale lateral bilayer (LBL) WS2–MoS2 heterostructures is reported by a two‐step chemical vapor deposition route. Raman, photoluminescence, and second‐harmonic generation images show the sharp boundaries between WS2 and MoS2 domains in the heterostructure. Atomically resolved scanning transmission electron microscopy further reveals that sharp boundaries are formed by seamless connections via a lateral zigzag epitaxy between WS2 and MoS2. Notably, the photodetector device based on the LBL WS2–MoS2 heterostructure exhibits ultrahigh photoresponsivity and detectivity (6.72 × 103 A W−1 and 3.09 × 1013 Jones for 457 nm laser light, respectively), orders of magnitude higher than those of MoS2 and WS2 monocrystals. These excellent performances render LBL WS2–MoS2 heterostructures as promising candidates for next‐generation optoelectronics.

Graphene Quantum Dots-Mediated Theranostic Penetrative Delivery of Drug and Photolytics in Deep Tumors by Targeted Biomimetic Nanosponges.

Dual-targeted delivery of drugs and energy by nanohybrids can potentially alleviate side effects and improve the unique features required for precision medicine. To realize this aim, however, the hybrids which are often rapidly removed from circulation and the piled up tumors periphery near the blood vessels must address the difficulties in low blood half-lives and tumor penetration. In this study, a sponge-inspired carbon composites-supported red blood cell (RBC) membrane that doubles as a stealth agent and photolytic carrier that transports tumor-penetrative agents (graphene quantum dots and docetaxel (GQD-D)) and heat with irradiation was developed. The RBC-membrane enveloped nanosponge (RBC@NS) integrated to a targeted protein that accumulates in tumor spheroids via high lateral bilayer fluidity exhibits an 8-fold increase in accumulation compared to the NS. Penetrative delivery of GQDs to tumor sites is actuated by near-infrared irradiation through a one-atom-thick structure, facilitating penetration and drug delivery deep into the tumor tissue. The synergy of chemotherapy and photolytic effects was delivered by the theranostic GQDs deep into tumors, which effectively damaged and inhibited the tumor in 21 days when treated with a single irradiation. This targeted RBC@GQD-D/NS with the capabilities of enhanced tumor targeting, NIR-induced drug penetration into tumors, and thermal ablation for photolytic therapy promotes tumor suppression and exhibits potential for other biomedical applications.

First Example of Kinetic Modelling of Multi-state Membrane Binding, Exapnsion and Disruption for an Antimicrobial Peptide

Antimicrobial peptide disruption of the membrane bilayer involves a series of defined states during binding and insertion, and are all associated with significant changes in the bilayer structure. We recently identified a complex series of bilayer state changes for the binding of an analogue of magainin 2, (Ala-8,13,18)-Magainin 2-amide (MagA), to lipid bilayers. However, the presence of multiple structural states of the membrane prevented the determination of kinetic constants using currently available kinetic models, but this information is necessary to allow the full definition of the mechanism of action. In this study the binding and dissociation of MagA to lipid bilayers with different charge and fluidity properties was studied with dual polarization interferometry, an optical technique capable of measuring real-time simultaneous changes in mass and birefringence (an optical parameter representing bilayer order). The dependence of birefringence vs. mass were categorised into several discrete mechanistic profiles and new multiple-state kinetic models were developed and fitted to the experimental data, with a three-state model with lateral bilayer expansion providing distinctly superior fits to simpler model types. Overall this is the first study to quantitatively analyse complex peptide-membrane binding data in terms of specific states of membrane disruption by an antimicrobial peptide.

Structure and Dynamics of Nonionic Surfactant Aggregates in Layered Materials.

The aggregation of surfactants on solid surfaces as they are adsorbed from solution is the basis of numerous technological applications such as colloidal stabilization, ore flotation, and floor cleaning. The understanding of both the structure and the dynamics of surfactant aggregates applies to the development of alternative ways of preparing hybrid layered materials. For this purpose, we study the adsorption of the triethylene glycol mono n-decyl ether (C10E3) nonionic surfactant onto a synthetic montmorillonite (Mt), an aluminosilicate clay mineral for organoclay preparation with important applications in materials sciences, catalysis, wastewater treatment, or as drug delivery. The aggregation mechanisms follow those observed in an analogous natural Mt, with the condensation of C10E3 in a bilayer arrangement once the surfactant self-assembles in a lamellar phase beyond the critical micelle concentration, underlining the importance of the surfactant state in solution. Solid-state 1H nuclear magnetic resonance (NMR) at fast magic-angle spinning (MAS) and high magnetic field combined with1H-13C correlation experiments and different types of 13C NMR experiments selectively probes mobile or rigid moieties of C10E3 in three different aggregate organizations: (i) a lateral monolayer, (ii) a lateral bilayer, and (iii) a normal bilayer. High-resolution 1H{27Al} CP-1H-1H spin diffusion experiments shed light on the proximities and dynamics of the different fragments and fractions of the intercalated surfactant molecules with respect to the Mt surface. 23Na and 1H NMR measurements combined with complementary NMR data, at both molecular and nanometer scales, precisely pointed out the location of the C10E3 ethylene oxide hydrophilic group in close contact with the Mt surface interacting through ion-dipole or van der Waals interactions.

Adsorption of switchable surfactant mixed with common nonionic surfactant on montmorillonite: Mechanisms and arrangement models

To improve understanding of adsorption behavior of mixed surfactants on typical clay components in soil for potential applications of surfactant-enhanced remediation (SER) technologies during remediation of hydrophobic organics-contaminated soil, the adsorption mechanisms and arrangement models of an electrochemical switchable cationic surfactant (11-Ferrocenylundecyl) trimethylammonium bromide (FTMA), mixed with the nonionic surfactant Tween 80 on montmorillonite were investigated. The mixed system in the presence of Tween 80 remains electrochemically reversible. The adsorption isotherms of the pure FTMA and FTMA-Tween 80 mixed system on montmorillonite were Langmuir type. The major mechanism of pure FTMA adsorption is via cation exchange as the total capacity is close to the cation exchange capacity (CEC) of montmorillonite. With the addition of Tween 80, the cation exchange of FTMA would be weakened by the function of hydrogen bonding. As the added concentration of FTMA and Tween 80 are 2874mg/L and 50 times of critical micelles concentration of Tween 80, adsorption capacity of FTMA and mixed surfactants decrease from 280.6 to 235.2mg/g and 400 to 298mg/g. Moreover, the adsorption capacity of Tween 80 linearly decreases from 118.7 to 62.7mg/g. Meanwhile, as the amount of FTMA increases from 0.4 to 1.0 times CEC of montmorillonite, the arrangement model of FTMA in the interlayer of montmorillonite changes from a flat monolayer, lateral bilayer to pseudotrilayer. When mixed with Tween 80, the interlayer space of montmorillonite increased significantly, and it showed a gradual increasing trend of interlayer space as the concentration of Tween 80 increased. The results of the present study show that the combined use of cationic and nonionic surfactants can reduce the adsorption loss of surfactants during remediation of polluted soil and then be conducive to the application of SER technologies.

Tuning electrochemical catalytic activity of defective 2D terrace MoSe2 heterogeneous catalyst via cobalt doping

Defective 2D terrace MoSe2/CoMoSe lateral and vertical heterostructures nanolayers electrocatalyst via metal cobalt doping displays ameliorative HER activity.

Roles of Interleaflet Coupling and Hydrophobic Mismatch in Lipid Membrane Phase-Separation Kinetics.

Characterizing the nanoscale dynamic organization within lipid bilayer membranes is central to our understanding of cell membranes at a molecular level. We investigate phase separation and communication across leaflets in ternary lipid bilayers, including saturated lipids with between 12 and 20 carbons per tail. Coarse-grained molecular dynamics simulations reveal a novel two-step kinetics due to hydrophobic mismatch, in which the initial response of the apposed leaflets upon quenching is to increase local asymmetry (antiregistration), followed by dominance of symmetry (registration) as the bilayer equilibrates. Antiregistration can become thermodynamically preferred if domain size is restricted below ∼20 nm, with implications for the symmetry of rafts and nanoclusters in cell membranes, which have similar reported sizes. We relate our findings to theory derived from a semimicroscopic model in which the leaflets experience a “direct” area-dependent coupling, and an “indirect” coupling that arises from hydrophobic mismatch and is most important at domain boundaries. Registered phases differ in composition from antiregistered phases, consistent with a direct coupling between the leaflets. Increased hydrophobic mismatch purifies the phases, suggesting that it contributes to the molecule-level lipid immiscibility. Our results demonstrate an interplay of competing interleaflet couplings that affect phase compositions and kinetics, and lead to a length scale that can influence lateral and transverse bilayer organization within cells.

Effect of Lipid-Based Nanostructure on Protein Encapsulation within the Membrane Bilayer Mimetic Lipidic Cubic Phase Using Transmembrane and Lipo-proteins from the Beta-Barrel Assembly Machinery.

A fundamental understanding of the effect of amphiphilic protein encapsulation on the nanostructure of the bicontinuous cubic phase is crucial to progressing biomedical and biological applications of these hybrid protein-lipid materials, including as drug delivery vehicles, as biosensors, biofuel cells and for in meso crystallization. The relationship between the lipid nanomaterial and the encapsulated protein, however, remains poorly understood. In this study, we investigated the effect of incorporating the five transmembrane and lipo-proteins which make up the β-barrel assembly machinery from Gram-negative bacteria within a series of bicontinuous cubic phases. The transmembrane β-barrel BamA caused an increase in lattice parameter of the cubic phase upon encapsulation. By contrast, the mainly hydrophilic lipo-proteins BamB-E caused the cubic phase lattice parameters to decrease, despite their large size relative to the diameter of the cubic phase water channels. Analysis of the primary amino acid sequence was used to rationalize this effect, based on specific interactions between aromatic amino acids within the proteins and the polar-apolar interface. Other factors that were found to have an effect were lateral bilayer pressure and rigidity within the lipid bilayer, water channel diameter, and size and structure of the lipo-proteins. The data presented suggest that hydrophilic bioactive molecules can be selectively encapsulated within the cubic phase by using a lipid anchor or aromatic amino acids, for drug delivery or biosensing applications.

The Ternary Lipid Phase Diagram by AFM

Understanding the physical properties and lateral structure of lipid bilayers is the subject of continuing interest, not least due to its emerging role in modifying the function of membrane proteins. A wide variety of experimental techniques have been used to determine phase diagrams of relevant ternary lipid mixtures that exhibit properties of the cell membrane. However, there are still many open questions and ambiguities. We use a variety of modes of atomic force microscopy (AFM) to study domain formation in ternary lipid mixtures. AFM has the unique advantages of having high lateral resolution, of being label free, and of being able to simultaneously measure membrane mechanical properties. A commonly stated disadvantage is that it is necessarily limited to supported bilayers, and that the proximity of the substrate will alter the phase behaviour of membrane. Various strategies have been employed over the years to obviate this effect, such as forming membrane stacks, tethering, and polymer cushioning. In this work we show that a model cell membrane on a mica substrate exhibits the same phase transitions as that observed in GUV's. We use temperature control and Fast-scan AFM across the whole phase diagram to study phase transitions, from binary systems to ternary mixtures exhibiting 2-phase (Ld-Lo, Ld-gel and Lo-gel) and 3-phase regions, and hence construct a complete ternary phase diagram. Dynamics previously undetected on support bilayers have been observed, such as Ostwald ripening and domain coalescence, domain boundary fluctuations and critical fluctuations. Nucleation (including tree-ring growth) and spinodal decomposition mechanisms are characterised. Our work demonstrates that AFM is not only a valid approach to studying phase separation in bilayers but that it is able to complement existing techniques and theories and provide new insights by directly visualizing lateral lipid bilayer structure.

Structural, thermal, morphological and surface charge properties of dodecyltrimethylammonium-smectite composites

The present investigation was undertaken to obtain information about the structural, thermal, morphological, surface charge and textural properties of the synthesized dodecyltrimethylammonium-smectite composites at various surfactant concentrations by means of powder X-ray diffraction, attenuated total reflection Fourier transform infrared, thermal analyses, scanning electron microscopy, electrophoretic mobility and surface area measurement techniques. The basal spacing values of organo-smectites varied between 13.55 and 17.00 Å that point out the successful intercalation of the surfactant cations into smectite layers with different molecular arrangements either lateral monolayer or lateral bilayer. Intercalation of surfactant cations led to appreciable decreases in the intensities of the bands at 3402 and 1635 cm−1 which originate from OH stretching and bending vibration of sorbed water molecules, respectively. Thermal analysis data showed that all organo-smectites had lower adsorbed water losses than raw and sodium-smectite and the removal of surfactant species occurred in the temperature range of 130–720 °C. The specific surface areas, pore volumes and micropore surface areas of organo-smectites decreased while the average pore width of these species increased with respect to that of raw smectite. The surfactant cations located in the interlayer spaces caused significant alterations in electrophoretic mobility values and morphology of raw smectite.

Lateral organization, bilayer asymmetry, and inter-leaflet coupling of biological membranes

Understanding of cell membrane organization has evolved significantly from the classic fluid mosaic model. It is now recognized that biological membranes are highly organized structures, with differences in lipid compositions between inner and outer leaflets and in lateral structures within the bilayer plane, known as lipid rafts. These organizing principles are important for protein localization and function as well as cellular signaling. However, the mechanisms and biophysical basis of lipid raft formation, structure, dynamics and function are not clearly understood. One key question, which we focus on in this review, is how lateral organization and leaflet compositional asymmetry are coupled. Detailed information elucidating this question has been sparse because of the small size and transient nature of rafts and the experimental challenges in constructing asymmetric bilayers. Resolving this mystery will require advances in both experimentation and modeling. We discuss here the preparation of model systems along with experimental and computational approaches that have been applied in efforts to address this key question in membrane biology. We seek to place recent and future advances in experimental and computational techniques in context, providing insight into in-plane and transverse organization of biological membranes.

Surfactant-modified montmorillonite by benzyloctadecyldimethylammonium chloride for removal of perchlorate

Abstract A high adsorption capacity (0.90 mmol/g) of perchlorate was achieved on organo-montmorillonites (organo-MMTs) through modification by benzyloctadecyldimethylammonium chloride (BODMA-Cl), which typically possesses a long alkyl chain and a benzene ring. With increase in the amount of BODMA-Cl added, the XRD and FTIR results showed that the BODMA+/BODMA-Cl achieved a lateral bilayer, pseudo-trilayer and tilted paraffin-like bilayer configurations in the MMT interlayer space with improvement of ordered arrangement, and the formation of bilayers and/or micelles on the external surface also was demonstrated by TG-DTA and zeta potential curves. The EDX spectra of resultant products and adsorption isotherms of perchlorate on organo-MMTs suggested that a larger content of BODMA-Cl resulted in synthesized adsorbent with a greater adsorption capacity, because neutral BODMA-Cl is predominantly responsible for ion exchange with perchlorate. The maximum adsorption capacity was attained not only by enhanced affinity between BODMA+ and metallic layer of MMT, but also by increasing density of intercalated BODMA-Cl which is caused by hydrophobic interactions through long alkyl chains and π–π interactions through benzene rings among BODMA+/BODMA-Cl. It was also emphasized that the high adsorption capacity of perchlorate on organo-MMTs was achieved with a rapid adsorption rate and stably maintained against variations in temperature, initial solution pH and co-existing competitive anion.

Modification of bentonite with cationic surfactant for the enhanced retention of bisphenol A from landfill leachate.

Bentonite was modified with cationic surfactant hexadecyl trimethyl ammonium bromide (HTAB) as landfill liner to retard the transportation of bisphenol A (BPA) for the first time. The modification was confirmed to form a lateral bi-layer in the interlayer space of bentonite by scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy. The introduction of HTAB into the internal position of bentonite led to an increased interlayer space of bentonite from 15.0 to 20.9Å and a higher sorption affinity for BPA (10.449mg/g of HTAB-bentonite and 3.413mg/g of raw bentonite). According to the Freundlich model, the maximum adsorption capacity of the HTAB-bentonite was found to be 0.410mg/g. The sorption capacity of raw bentonite and HTAB-bentonite both decreased at alkaline conditions. Although the hydraulic conductivity of HTAB-bentonite was higher than that of raw bentonite, results of laboratory permeability and column tests indicated that HTAB-bentonite obviously extended the BPA breakthrough time by 43.4%. The properties of the HTAB-bentonite revealed its notable advantages as components of landfill liners material to retain BPA in leachate.