Increase In Interlayer Distance Research Articles

Microstructures of Starch Granules with Different Amylose Contents and Allomorphs as Revealed by Scattering Techniques.

In this study, as-is (ca. 12% moisture by mass) and hydrated (50% water by mass) granules of waxy potato (WP), waxy wheat (WW), waxy maize, normal maize, and high-amylose maize (HAM) starches were investigated by using small-angle neutron and X-ray scattering (SANS and SAXS), wide-angle X-ray scattering, and ultra-small-angle neutron scattering. The SANS and SAXS data were fitted using the two-phase stacking model of alternating crystalline and amorphous layers. The partial crystalline lamellar structures inside the growth rings of granules were analyzed based on the inter-lamellar distances, thicknesses of the crystalline lamellae and amorphous layers, thickness polydispersities, and water content in each type of layer. Despite having a longer average chain length of amylopectin, the WP and HAM starches, which had B-type allomorph, had a shorter inter-lamellar distance than the other three starches with A-type allomorph. The WP starch had the most uniform crystalline lamellar thickness. After hydration, the amorphous layers were expanded, resulting in an increase of inter-layer distance. The low-angle intensity upturn in SANS and SAXS was attributed to scattering from interfaces/surfaces of larger structures, such as growth rings and macroscopic granule surfaces. Data analysis methods based on model fitting and 1D correlation function were compared. The study emphasized─owing to inherent packing disorder inside granules─that a comprehensive analysis of different parameters was essential in correlating the microstructures with starch properties.

A facile single‐step approach to achieve in situ expanded g‐C3N4 for improved photodegradation performance

AbstractImproved graphitic carbon nitride (g‐C3N4) was synthesized through a unique one‐step cost‐effective technique involving a dynamic gas bubbling phenomenon using ammonium chloride (NH4Cl) as a bubbling agent. An extensive investigation was carried out to optimize the weight ratio of NH4Cl and melamine during the thermal pyrolysis process. Here, we report an improved form of g‐C3N4 namely “expanded g‐C3N4” with increased interlayer distance and remarkable volume expansion. The surface area of this improved version has notably increased leading to higher photocatalytic efficiency as compared with its counterpart, an synthesized without adding NH4Cl. Synthesized photocatalyst materials were further used to study the Rhodamine B photodegradation under visible light. It was observed that the expanded g‐C3N4 showed a 2.4 times higher photodegradation rate than its counterpart and degraded 94% of the dye in just 30 min.

A note on using expanded graphite for achieving energy‐ and time‐efficient production of graphene nanoplatelets via liquid phase exfoliation

AbstractAlthough easily scalable, the production of graphene nanoplatelets (GNP) by the means of liquid‐phase exfoliation of graphite flakes (GF) remains an energy‐ and time‐intensive process. In this work, we demonstrate that significant time and energy can be saved in GNP production when employing expanded graphite (EG) in a surfactant‐assisted liquid phase exfoliation process. Owing to its increased interlayer distance, the exfoliation of EG can be accomplished in a much shorter time (<30 min) compared to GF (approximately 7 h in the present case). Moreover, the energy required for the EG exfoliation is close to 80‐fold lower than that for GF exfoliation. Monitoring of the mean lateral dimension, specific surface area, and graphite flake‐to‐GNP transition during exfoliation was performed experimentally using several analytical techniques. The EG‐derived GNPs are produced much faster and require less energy for exfoliation compared to GF, thus making it a more efficient alternative technique.

Unveiling the potential of MXenes for H2 purification and CO2 capture as an emerging family of nanomaterials

AbstractMXenes have gained deep interest in various applications since the discovery of their first member, Ti3C2Tx, in 2011 due to their exceptional properties. They are accepted as promising candidates for gas separation applications. Here, we aimed to identify CO2/H2 adsorption‐based separation performances of blooming MXene family including 730 members under various process conditions via molecular simulations. We reported that 62% and 83% of MXenes revealed percent regenerability (R%) >90% for single gas adsorption under pressure and vacuum swing adsorption conditions, respectively while these percentages reached 98% and 95% with the increase in interlayer distance. Ti0.4Nb1.6C, V2Ti2C3, Ti2VC2, and Ti1.2Nb0.8C are best MXenes in single gas adsorption whereas for CO2/H2:25/75 mixture, top MXenes dominantly consist of Cr, Mo, and W. We reported an online MXene database (https://mem-ces.com/mxenes/) which covers simulated adsorbent metrics of MXenes for CO2/H2 separations. Examining this MXene database would be beneficial to conceptually understand MXene design for CO2/H2 separation.

Revealing the effects of terminal groups of MXene on the water desalination performance

The hydrophilicity as well as the charge nature can be tuned by manipulating the surface termination of MXene, which significantly affects the desalination of MXene membrane. However, the effects of termination group of MXene membrane on its water desalination performance are poorly understood. In this work, we adopted classic molecular dynamics (MD) simulation to systematically explore the influences of termination group, including fluorine (F), oxygen (O), and hydroxyl groups (OH), on the desalination performance of Ti 3 C 2 T x membrane. The simulation results showed the surface charge features as well as the hydrogen bond interactions significantly influence the interactions between termination group and water. The water permeability through MXene channel with different surface terminations follows the order, F > O > OH. The charge nature of surface terminations also plays a vital role in their interactions with ions. The negative charge of surface terminations traps Na + ion both near the mouse and inside the channel of MXene membranes. As a result, MXene membranes possess distinctive Na + ion rejection performance. After comparison, we conclude the desalination performance of Ti 3 C 2 F 2 is much better than traditional desalination membranes. Our work revealed the mechanisms responsible for the effects of termination type of MXene on water desalination performance, which might provide useful suggestions for the optimization of MXene membranes for water desalination. • The increase of interlayer distance will promote water permeability but deteriorate ion rejection efficiency. • Water molecules travel fastest in MXene nanochannel with termination of F. • MXene membrane carrying negative charge is benefited for Na + rejection. • The desalination performance of Ti 3 C 2 F 2 is much better than traditional desalination membranes.

Correlating surface structures and nanoscale friction of CVD Multi-Layered graphene

Surface structures on chemical vapor deposition (CVD) grown graphene determine its functional properties, and thus, in-depth understanding about the relationship between the structures and the properties is essential to investigate CVD graphene in a variety of scientific and engineering applications. Here, we correlate surface structures with nanoscale friction of a multi-layered graphene island. By cleaning graphene surface utilizing mechanical scratching of polymeric surface contamination, we unveiled the surface structures such as small-scale and large-scale (folded) wrinkles on graphene using atomic force microscopy (AFM) and investigated their effect on nanoscale friction. The formation of such surface structures induced twisting of the top-most graphene layer as confirmed by Raman spectroscopic analysis, and the twisted top-most graphene layer influenced the layer dependency of nanoscale friction depending on the applied normal load as revealed by friction force microscopy (FFM) measurements. No identifiable layer-dependency was observed at the low normal load due to the increased interlayer distance between the twisted top-most graphene layer and the underlying AB-stacked layers. Increasing the normal load resulted in the decrease of the interlayer distance and made the contribution of different lateral bending stiffness more dominant to nanoscale friction, resulting in the strong layer-dependency of nanoscale friction on multi-layered graphene.

Interlayer alkali ion governs robustness, reactivity, and dielectric properties of sintered lepidocrocite titanate

We investigate the structure across different length scales including the dielectric properties of Cs0.7Zn0.35Ti1.65O4, Rb0.75Zn0.375Ti1.625O4, and K0.8Zn0.4Ti1.6O4 sintered at TS ​= ​900–1100 ​°C, where the lepidocrocite-type crystal structure is preserved. The increasing interlayer distance in the Rb-/K-analog is explained by the alkali loss which reduces the electrostatic attraction between the sheets and the interlayer ion. Meanwhile, the interlayer contraction in the Cs-analog is rather unusual. The increasing (decreasing) interlayer distances correlate to upshift (downshift) of the Ti-O vibration in the Raman spectra. The three compositions show varied grain orientation depending on the interlayer ion and TS. The dielectric permittivity differs by one order of magnitude in the order Cs0.7Zn0.35Ti1.65O4 « Rb0.75Zn0.375Ti1.625O4 « K0.8Zn0.4Ti1.6O4, suggesting the interlayer ion as the dominating dipole. The influences of TS, pellet density (i.e., alkali loss), and grain size/morphology/orientation on the dielectric permittivity are discussed. The understanding of the response to a high temperature treatment would be beneficial not only to specimen fabrications for physical properties measurements, but also to applications where the thermal stability is of concern.

Effect of methyl orange as the modifier on the mechanical, thermal, and thermo‐mechanical properties of clay/epoxy composites

AbstractIn this study, bentonite clay/epoxy composites were simply and successfully produced via conventional casting method for 0.5, 1, and 2 wt% filler content. Previously modified clay (surfactant and silane agent applied) was treated with methyl orange (MO) and its effects on composites were investigated in terms of crystallographic, thermal, thermo‐mechanical, morphologic, and topographic aspects as well as quasi‐static characteristics. According to XRD graphs, MO presence led to the increase of interlayer distance and resulted in partial intercalation for modified clay (MC) based mixture, while an opposite case was seen in neat clay (NC) blend. The 2 wt% MO/MC loaded composite achieved the highest tensile modulus, flexural stiffness, and hardness values among all samples—increase of 14%, 40%, and 3%, respectively. Same composite system exhibited improved results for both glass transition temperature (~7%↑) and storage modulus (~35%↑), in spite of insufficient thermal characteristics. Irregular particles/tactoids were present in the fracture images, which probably promoted the stress concentration and caused the reduction of strength parameter for all composites. Furthermore, independent of clay type (MC or NC) whole structures showed similar surface roughness values but different topographic textures in terms of surface profiles.

Doubling the cyclic stability of 3D hierarchically structured composites of 1T-MoS2/polyaniline/graphene through the formation of LiF-rich solid electrolyte interphase

MoS2 has been viewed as a unique anode material for lithium-ion batteries; however, its electrochemical performance is usually restrained by poor conductivity of 2H phase and an uneven solid-electrolyte interphase (SEI). To tackle the above issues, the ternary composite is synthesized by self-assembling MoS2 2D sheets with higher percentage of metallic 1T-phase on polyaniline functionalized reduced graphene oxide (PANI-rGO) through an electrostatic interaction. The flower-like aggregate of 1T-MoS2 having increased interlayer distances is beneficial for diffusion and intercalation of lithium ions. Furthermore, the graphene substrate facilitates the electron transportation. At the current density of 0.1 and 2 A g−1, the ternary composite has the specific capacities of 812 and 333 mAh g−1 respectively. On the other hand, the cyclic stability of ternary composite can be further improved when 10 wt% fluoroethylene carbonate (FEC) is added into the traditional carbonate-based electrolyte. The capacity retention of ternary composite cycled in a FEC-mixed electrolyte is two times higher than that in a traditional electrolyte after 400 charge–discharge cycles. This is attributed to the fact that the use of FEC enables the formation of active LiF-rich SEI.

Exfoliation of Nanosized α-Zirconium Phosphate in Methanol

The exfoliation of microcrystalline α-zirconium phosphate (α-ZrP) in an organic solvent is very difficult to achieve. Surprisingly, the addition of tetra(n-butyl)ammonium hydroxide (TBAOH) into a methanol dispersion of a nanosized α-ZrP brings about the complete exfoliation of nanosheets. To understand the mechanism, we examined the stepwise intercalation/exfoliation of the nanosized α-ZrP using TBAOH in four different solvents (water, methanol, ethanol, and butanol). Propionate groups on the edge of the nanosized α-ZrP prevent TBA cations from entering the galleries. Due to the formation of unstable solvent-intercalated α-ZrP with an increased interlayer distance in methanol and ethanol, TBA cations can overcome the steric hindrance and move into nanosheet layers to exchange with solvent molecules. However, the movability of the cations into the center of the galleries is preferred at a certain interlayer distance range, which leads to exfoliation of α-ZrP in methanol but intercalation only in ethanol. In water, in the beginning, neither intercalation nor exfoliation by TBA cations occurs. An additional amount of TBAOH causes the deformation of propionate groups and removes the barriers on the edges, followed by late intercalation and then exfoliation. On the other hand, butanol, as the solvent, is bulky and effectively limits the intercalation behavior of TBA cations. The weaker polarity of ethanol and butanol, compared with water and methanol, lowers the ion interactions in the solvent, which is another reason why they do not lead to exfoliation.

Tailoring superficial morphology, defect and functional group of commercial carbon cloth for a flexible, stable and high-capacity anode in sodium ion battery

Developing a flexible hard carbon-based anode is very important for the flexible sodium ion battery. Here, a porous carbon cloth with lots of defects and C=O functional groups is prepared by combining the thermal etching with oxidation-exfoliation method. The partial graphitization and N and S codoping improve the conductivity and electrochemical properties. Multi-step modifications stabilize the defects, which is proved by in situ Raman and leads to the enhanced initial coulombic efficiency. Benefiting from the increased interlayer distance, C=O functional group, pore and defect, the Na+ adsorption (sloping region in discharging curve) plays an important role in Na+ storage process specially at high current density. In comparison with other hard carbon materials (0.40 V), the low midpoint voltages in sloping region of carbon cloth-derived electrodes (0.11 V) promote the energy density of full cell. The optimized electrode based on the total weight of electrode exhibits a high discharging capacity (0.983 mAh cm−2 at 0.2 mA cm−2 or 98.3 mAh g−1 at 20 mA g−1) and a long-term cycling performance (91.6% capacity retention after 1000 cycles at 0.6 mA cm−2). The high reversible capacity of coin-type full cell (≈0.515 mAh cm−2 at 0.2 mA cm−2) and the outstanding flexibility of pouch cell further reveal its potential.

Hollow opening nanoflowers MoS2-CuS-EG cathodes for high-performance hybrid Mg/Li-ion batteries

Hybrid Mg/Li-ion Batteries (MLIBs) combine both the advantages of fast alkali metal ions intercalation cathode and dendrite-free Mg anode that exhibits satisfactory electrochemical performance. However, achieving superior comprehensive battery performance is still a main challenge for MLIBs. Novel hollow opening nanoflower MoS2-CuS-EG (HONF-MoS2-CuS-EG) cathode with unique structure as MLIBs cathode was firstly fabricated via a facile hydrothermal method and superior comprehensive electrochemical performances are presented. Constructed by increased interlayer distance MoS2, metallic-like conductivity CuS and superior electrical conductivity EG, high discharge capacity and superior rate performance are demonstrated by HONF-MoS2-CuS-EG electrode. The volume expansion/contraction during charge-discharge cycles can be effectively buffered by EG and superior cycle stability. The discharge capacity at 10th cycle is as high as 240.6 mAh·g−1, which increases over the 1st cycle by 8.6% at 50 mA·g−1. The discharge capacities at 200 and 1000 mA·g−1 are 201.4 and 117.5 mAh·g−1. The capacity retention rates after 100 cycles (172.4 mAh·g−1) and 200 cycles (73.5 mAh·g−1) for HONF-MoS2-CuS-EG electrode at 50 mA·g−1 are 47.43% and 22.22%, which are much higher than those of hollow close nanoflower MoS2 (HCNF-MoS2) cathode (2.81% and 1.95%). As high as 262.5 mAh·g−1 discharge capacity with 91.6% capacity retention of HONF-MoS2-CuS-EG at 500 mA·g−1 and 150 cycles is presented, indicating that increasing current density is favor to cycle performance of HONF-MoS2-CuS-EG cathode. The electrochemical mechanism of HONF-MoS2-CuS-EG electrode in MLIBs is also elaborated. This work provides a practical approach to construct advanced MoS2-based cathode materials for MLIBs.

Nitrogen-doped nanoporous graphene induced by a multiple confinement strategy for membrane separation of rare earth.

SummaryRare earth separation is still a major challenge in membrane science. Nitrogen-doped nanoporous graphene (NDNG) is a promising material for membrane separation, but it has not yet been tested for rare earth separation, and it is limited by multi-complex synthesis. Herein, we developed a one-step, facile, and scalable approach to synthesize NDNG with tunable pore size and controlled nitrogen content using confinement combustion. Nanoporous hydrotalcite from Zn(NO3)2 is formed between layers of graphene oxide (GO) absorbed with phenylalanine via confinement growth, thus preparing the sandwich hydrotalcite/phenylalanine/GO composites. Subsequently, area-confinement combustion of hydrotalcite nanopores is used to etch graphene nanopores, and the hydrotalcite interlayer as a closed flat nanoreactor induces two-dimensional space confinement doping of planar nitrogen into graphene. The membrane prepared by NDNG achieves separation of Sc3+ from the other rare earth ions with excellent selectivity (∼3.7) through selective electrostatic interactions of pyrrolic-N, and separation selectivity of ∼1.7 for Tm3+/Sm3+.

Organo-montmorillonite modified by polyionenes for polymer composites

The technology for producing montmorillonite modified with polyionenes has been developed. It was shown that macromolecular polymer intercalation of the quaternary ammonium salt of montmorillonite intercrystalline space is accompanied by an increase in interlayer distances from 1.08 to 1.67 nm. A method for the synthesis of montmorillonite modified with polyionenes is proposed. The optimal conditions for the sorption of polymeonene molecules by montmorillonite were found: the concentration of the aqueous dispersion of montmorillonite is 1%, the temperature of the reaction medium is 40 ° C, the ratio of montmorillonite-polyionene is 3: 1, the processing time is 24 hours.

Enhanced activity and stability of MoS2 through enriching 1T-phase by covalent functionalization for energy conversion applications

The selective enrichment of a highly active form/phase of material is essential for the development of potential candidates for specific applications. Herein, we demonstrate the first example of the covalent functionalization of a highly active 1T phase of outstanding 2D material, such as MoS2, and its enrichment (>94%) using a solvent extraction technique. Covalent functionalization stabilizes the metastable 1T phase with increased interlayer distance, which makes it a more suitable candidate for energy applications. The enriched functionalized 1T-MoS2 with n-butyl groups (en-Bu-1T-MoS2) shows a lower overpotential of 169 mV (vs. Reversible Hydrogen Electrode, RHE) with the loading mass of 0.9 mg cm−2 toward the hydrogen evolution reaction (HER). The continuous HER of en-Bu-1T-MoS2-based electrode for >200 h showed only <11% increment in the overpotential of HER, which suggests the ultra-long term stability of en-Bu-1T-MoS2 compared to the covalently functionalized 1T-MoS2-based HER electrocatalysts reported thus far. Interestingly, the semi-transparent en-Bu-1T-MoS2 film also served as an excellent counter electrode for dye-sensitized solar cells (DSSCs) with the higher power conversion efficiency (PCE) of 9.11% and 82% of PCE retention even after 200 h. The unprecedented method presented in this work is a unique example, which shows the possibility of improving material properties with the help of a novel approach.

Two-step synthesis of well-ordered layered graphite oxide with high oxidation degree

Chemical oxidation of graphite by strong oxidant in strong acid medium produces graphite oxide (GO) with a plausible oxidation degree, however the precursor is susceptible to exfoliation and structural deformations. In this work, we present a two-step preparation method of highly oxidized GO flakes with well-ordered layered structure. Firstly, graphite was electrooxidized in HClO4 electrolyte yielding electrochemically gathered graphite oxide (EGO). Next, EGO was chemically overoxidized by modified Hummers method to prepare overoxidized electrochemically gathered graphite oxide (OEGO). Due to the increased interlayer distances of EGO, MnO3+ ions are able to penetrate the interlayer spaces and oxidize the unreacted graphitic domains. Hence, the synthesized OEGO is characterized by minor structure deformation and high oxidation degree. In case of our investigations most of well-ordered layered domains have been preserved, in contrast to the GO obtained directly from graphite. It is also noted that the overoxidation of EGO mainly results in formation of hydroxyl and epoxy groups. Additionally, rinsing OEGO with acetone helps prevent the tearing of oxidized graphene layers by O2 evolution arising from the reaction of H2O2 with MnO2 precipitated on the surface of water-washed samples.

Synthesis and characterization of conducting aniline and o-anisidine nanocomposites based on montmorillonite modified clay

A study on clay mineral polymer nanocomposites (CPN), namely polyaniline/montmorillonite-cetyltrimethylammonium bromide (PANI/Mt-CTAB), poly o-anisidine/montmorillonite-cetyltrimethylammonium bromide (poly(o-ANIS)/Mt-CTAB) and poly o-anisidine-co-aniline/montmorillonite-cetyltrimethylammonium bromide (poly(o-ANIS-co-ANI)/Mt-CTAB), synthesized by oxidative chemical polymerization method is presented. The nanocomposites have been characterized by Fourier transform infrared spectroscopy, UV–vis spectroscopy, and cyclic voltammetry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and thermogravimetry and differential scanning calorimetry analysis. By UV–vis measurements different electronic transitions for the CPNs were pointed out. The voltammograms indicate that the synthetized materials are electroactive. The FTIR analysis reveals the characteristic bands of the polymers and of the Mt-CTAB. The shift of the bands to higher/lower wavenumbers demonstrate the interaction between the pristine polymers macromolecular chains and the montmorillonite (Mt). The intercalation of the polymers inside the mineral clay was confirmed by the increased interlayer distance connected with the position of the 011 diffraction plane of the Mt., and the intercalation and exfoliation states were highlighted in the scanning and transmission electron microscopy images.The obtained results are encouraging in respect with the purpose to use them in the field of photovoltaic applications.

Intercalation compounds of a smectite clay with an ammonium salt biocide and their possible use for conservation of cultural heritage

Ordered intercalation compounds between a smectite mineral clay (montmorillonite, Mt) and the ammonium salt mainly used for stone material disinfection procedures (i.e. N-Alkyl-N-benzyl-N,N-dimethylammonium chloride, shortly known as benzalkonium chloride, BAC), leading to an increase of interlayer distance from 1.3 nm up to 3.4 nm, have been prepared. The used clay/ammonium salt ratios are close to (or higher than) those often used for stone materials disinfection procedures for the conservation in cultural heritage. The prepared intercalated compounds have been studied as for their possible cation release in suitable aqueous media. Mt/BAC intercalate compounds are able to release only a fraction (if any) of the intercalated cations, eventually leading to a stable intermediate intercalate structure with interlayer distance not far from 1.9 nm, with a Mt/BAC ratio roughly equal to 4/1. The overall results indicate that Mt/BAC intercalates are possibly suitable for biocide applications in stone conservation procedures requiring both fast antimicrobial release and long-term biostatic effect.

Interlayer decoupling in twisted bilayers of [formula omitted]-phosphorus and arsenic: A computational study

We investigate magnetism and band structure engineering in Moiré superlattice of blue phosphorus (β-P) and grey arsenene (β-As) bilayers, using ab initio calculations. The electronic states near the valence and conduction band edges have significant pz character in both the bilayers. Thus, twisting the layers significantly reduce the interlayer orbital overlap, leading to a decrease in the binding energy (up to ∼33%) and an increase in interlayer distance (up to ∼10%), compared to the most stable AA-stacking. This interlayer decoupling also results in a notable increase (up to ∼25–50%) of the bandgap of twisted bilayers, with the valance band edge becoming relatively flat with van-Hove singularities in the density of states. Thus, hole doping induces a Stoner instability, leading to ferromagnetic ground state, which is more robust in Moiré superlattices, than that of AA-stacked β-P and β-As.

TiO2-pillared magadiite and its arsenic adsorption capacity

The structural and chemical interactions of magadiite with TiO2 pillars were examined along with arsenic adsorption potential of TiO2-pillared magadiite. The interlayer space of magadiite accommodated TiO2 in the form of moieties rather than discrete particles, which led to a slight increase in interlayer distance and consequently a remarkable formation of micropores (a specific surface area of 270 m2/g). High thermal stability up to 800 °C and increased interlayer space were attributed to the formation of Ti–O–Si bonding (966 cm−1) between interlayered silanol groups and TiO2 pillars. TiO2-pillared magadiite removed up to 100% of As(V) from aqueous solution at the initial concentrations of 0.5–1.0 mg L−1. These unique structural and textural evolutions of magadiite upon pillaring with TiO2 provide new insights to understand the pillaring behaviors of hydrated layered polysilicates and to fabricate pillared materials applicable to arsenate adsorption.