Regular Layered Structure Research Articles

Fabrication of nacre-like polymer/clay nanocomposites with water-resistant and self-adhesion properties

HypothesisNacre-like polymer/clay nanocomposites are a fascinating material thanks to its superior mechanical property. However, it has been a great challenge to incorporate hydrophobic polymer components due to highly hydrophilic nature of clay, which limits further improvement of water-resistance and addition of various functionalities. To overcome this problem, we developed a method to form regular nacre-like layered structure from a hydrophobic polymer and hydrophilic clay by a combination of surface modification of clay and selective click reaction between the polymer and clay surfaces. ExperimentsNatural clay, montmorillonite, was modified with a hydrophobic surfactant bearing an ethenyl group and subsequently reacted in situ with a thiol-functionalized hydrophobic polysiloxane. The layered structure, as well as its formation process, mechanical property, physical stability in water, and self-adhesion property of the nanocomposites were investigated. FindingsIn situ thiol-ene click reaction between surface-modified clay and polymer led to self-alignment of clay platelets into a regular layered structure. The resultant nacre-like nanocomposites not only showed the good mechanical property but also had excellent stability in water and self-adhesion ability, both of which originated from the characteristics of the polymer used. These findings widen the possibility of functional nacre-like nanocomposites by expanding the range of applicable polymers to hydrophobic ones.

Two-Dimensional Transition Metal MXene-Based Photocatalysts for Solar Fuel Generation.

The exploration of advanced and novel photocatalytic materials has been widely investigated in recent years. MXene, a new two-dimensional (2D) transition metal material, is gaining attention as a suitable alternative for promoting photocatalytic performance because of its flexible adjustability of elemental composition, regular layered structure, and excellent electrical conductivity. This Perspective summarizes the recent significant advancements in 2D MXene-based photocatalysts for solar fuel conversion. The rational design and specific effects of MXene-based photocatalysts for photocatalytic solar fuel generation are described. Moreover, the different roles of MXene in MXene-based photocatalysts, such as functional group provider, photocatalytic electronic acceptor, substrate, and cocatalyst, for improving photocatalytic performance are discussed. Further discussion about the challenges and optimizations for improvements of 2D MXene and MXene-based photocatalysts in the context of promising solar fuel generation is also presented.

Synthesis of benzenesulfonated PANI/RGO as cathode material for rechargeable lithium-polymer batteries

Graphene oxide (GO) was synthesized by the modified Hummers method and then reduced with NaBH4 to form RGO with a regular layered structure. The graphene oxide is benzenesulfonated to obtain a functionalized graphene material (RGO-BS). The benzenesulfonated polyaniline/RGO composite (PANI/RGO-BS) was prepared by adsorption double oxidation method using RGO as template. Some physical characterization methods (X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy) were used to analyze the morphology and crystallinity of the composite. The electrochemical properties were characterized by cyclic voltammetry, impedance spectroscopy, galvanostatic charge/discharge, and rate capability. The initial discharge specific capacities of oxidized PANI/RGO-BS and reduced PANI/RGO-BS were 165.4 and 176 mAh/g. After 100 cycles, the capacity retention rates were 92.6% and 96%, the coulombic efficiency of the battery is close to 100%. These results indicate functionalized composite has exciting potentials for the cathode material of lithium-ion battery.

Enhanced photocatalytic dye degradation activity of carbonate intercalated layered Zn, ZnNi and ZnCu hydroxides

Carbonate intercalated layered Zn, ZnNi and ZnCu hydroxides were synthesized by a facile hydrothermal method for the visible light driven photocatalytic methylene blue dye degradation. The crystalline phase, surface states, optical and morphological properties were studied by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) measurements. The XRD measurement demonstrated that all the synthesized materials were in a regular layered structure. Optical spectra of the samples were revealed that layered ZnNi hydroxide showed the visible light absorption property. The photocatalytic activities of the prepared layered materials examined by the degradation of methyl blue (MB) dye solution under visible light illumination. Among the prepared layered hydroxide, ZnNi hydroxide exhibited the 90% removal rate for MB under visible light illumination. The enhanced photocatalytic activity of ZnNi hydroxide is due to combined visible light absorption nature and hierarchical flower-like structure with a large number of active sites. Moreover, the ZnNi hydroxide has very good recyclability until remain active after the complete fourth degradation cycle.

Preparation of Regenerated Cathode Material Lithium Nickel Cobalt Oxide LiNi<sub>0.7</sub>Co<sub>0.3</sub>O<sub>2</sub> Form Spent Lithium-Ion Battery

With the development of new energy vehicles, urgent issues have attracted considerable attention. Some power batteries have entered the scrapping period, with the imperative recycling of used power batteries. Some studies have predicted that by 2020, the amount of power lithium battery scrap will reach 32.2 GWh, corresponding to ~500,000 tons, and by 2023, the scrap will reach 101 GWh, corresponding to ~1.16 million tons. In this study, nickel-cobalt-lithium LiNi0.7Co0.3O2cathode materials are regenerated from spent lithium-ion battery cathode materials as the raw material, which not only aids in the reduction of pressure on the environment but also leads to the recycling of resources. First, extraction is employed using extracting agent p204 to remove aluminum ions from an acid leaching solution. Extraction conditions for aluminum ions are: include a phase ratio of 1:2,a pH of 3, an extractant concentration of 30%, and a saponification rate of 70%.Next, the precursor was prepared by co-precipitation using sodium hydroxide and ammonia water as the precipitant and complexion agents, respectively; hence, the cathode material can be uniformly mixed at the atomic level. The precursor and lithium hydroxide were subjected to calcination at high temperature using a high-temperature solid-phase method. The Calcination conditions include an air atmosphere ; a calcination temperature of 800° °C ; a calcination time of 15 h, an n (precursor): n (lithium hydroxide) ratio of 1:1.1.The Thermogravimetric analysis revealed that the synthesis temperature should not exceed 850°C. X-ray diffraction analysis, scanning electron microscopy, and energy spectrum analysis of the cathode material revealed a composition comprising Li, Ni, and Co oxides. After analysis, the material obtained is lithium nickel-cobalt-oxide, LiNi0.7Co0.3O2, which is a positive electrode material with good crystallinity and a regular layered structure.

Synthesis of PANI/rGO composite as a cathode material for rechargeable lithium-polymer cells

Graphene oxide (GO) was synthesized by an improved Hummers method and then reduced with NaBH4; GO became rGO with regular layered structure. Polyaniline (PANI)/rGO composite was prepared by a adsorption double oxidant method with rGO as a template. Some physical characterization methods (Fourier transform infrared spectroscopy analysis, X-ray diffraction, scanning electron microscope, and transmission electron microscope) were used to analyze the morphology and crystallinity of the composite. The electrochemical properties were characterized by cyclic voltammetry, impedance spectroscopy, galvanostatic charge/discharge, and rate capability. The first discharge specific capacity of the rPANI/rGO and PANI/rGO was 181.2 and 147.8 mAh/g. After 100 cycles, the capacity retention rate was still 90.2 and 88.9% separately, and the coulombic efficiency of batteries is close to 100%. These results demonstrate the composite has exciting potentials for the cathode material of lithium-ion battery.

Higher alcohol synthesis via syngas over CoMn catalysts derived from hydrotalcite-like precursors

A series of CoMn catalysts derived from hydrotalcite precursors with different Co/Mn molar ratios were prepared and applied for higher alcohols synthesis (HAS) via syngas. The physical and chemical properties of as-prepared catalysts were investigated by various characterization methods such as BET, XRD, TPR, TG, SEM, HRTEM and EDS. The results showed that the proper Co/Mn molar ratio can increase the specific surface area, improve the reducibility, and form regular layered structure to provide more uniform distribution of active sites, thereby enhancing the catalytic activity and alcohol selectivity. When the Co/Mn ratio of catalyst reached 2, the highest space time yield (STY) and selectivity of alcohol were obtained. Moreover, the CoMn catalyst with layered structure showed higher activity and yield of alcohol under high reaction temperature than that without layered structure. Characterization results indicated that the layered structure catalyst can provide larger surface area, smaller particles size, and stronger interaction between Co and Mn, as well as resist the separation of Co, Mn and prevent the aggregation, thus improving the catalytic performance of CoMn catalysts for higher alcohols synthesis. In addition, the CoMn catalyst obtain derived from hydrotalcite precursors presented great stability for keeping active site highly disperse on the layer during the long reaction time.

Refined Deformation Model for Metal-Composite Plates of Regular Layered Structure in Bending Under Conditions of Steady-State Creep

The problem of the mechanical behavior of metal-composite plates of regular layered structure in bending under conditions of steady-state creep of all phase materials is formulated. Equations describing, with various degrees of accuracy, the stress and viscous creep states of such plates with account of their weakened resistance to transverse shears are obtained. The relations of the classical Kirkhoff theory, the nonclassical Reissner theory results, and the second variant of Timoshenko theory result as special cases of these equations. For asymmetrically loaded annular plates with one edge clamped and statically loaded other one, a simplified variant of the refined theory, whose complexity in practical realization is comparable to that of the Reissner theory, is developed. The bending deformations of such annular plates at different levels of thermal actions are calculated. It is shown that, with increasing temperature, the accuracy of calculations within the framework of the traditional theories decreases sharply and neither of them provides an accuracy for the calculated compliance of the structure even within 20%.

High density ultrashort relativistic positron beam generation by laser-plasma interaction

A mechanism of high energy and high density positron beam creation is proposed in ultra-relativistic laser-plasma interaction. Longitudinal electron self-injection into a strong laser field occurs in order to maintain the balance between the ponderomotive potential and the electrostatic potential. The injected electrons are trapped and form a regular layer structure. The radiation reaction and photon emission provide an additional force to confine the electrons in the laser pulse. The threshold density to initiate the longitudinal electron self-injection is obtained from analytical model and agrees with the kinetic simulations. The injected electrons generate γ-photons which counter-propagate into the laser pulse. Via the Breit–Wheeler process, well collimated positron bunches in the GeV range are generated of the order of the critical plasma density and the total charge is about nano-Coulomb. The above mechanisms are demonstrated by particle-in-cell simulations and single electron dynamics.

Fluidic behaviours in a 2D folded-graphene aerogel monolith

Conduction of pressurized water through two-dimensional (2D) layers in monolithic folded-graphene aerogels (FGA) is investigated experimentally. The synthesized FGA has a regular layered structure with a uniform d-spacing around 20 nm. Compared with one-dimensional nanofluidics in carbon nanotube arrays that have a similar characteristic length scale, the conduction pressure of FGA is much lower by nearly 2/3. The reduction in pressure may be attributed to the more energetically favourable molecular configurations in the 2D nanoenvironment, associated with the relaxation of lateral constraints of water molecules. The water conduction pressure through FGA rises exponentially with the sample thickness, due to the interlayer resistance. This finding may find wide applications in nanotransportation, nanofiltration, and nanofluidic energy management.

Self-Assembly of Nanoclusters into Mono-, Few-, and Multilayered Sheets via Dipole-Induced Asymmetric van der Waals Attraction.

Two-dimensional (2D) nanomaterials possessing regular layered structures and versatile chemical composition are highly expected in many applications. Despite the importance of van der Waals (vdW) attraction in constructing and maintaining layered structures, the origin of 2D anisotropy is not fully understood, yet. Here, we report the 2D self-assembly of ligand-capped Au15 nanoclusters into mono-, few-, and multilayered sheets in colloidal solution. Both the experimental results and computer simulation reveal that the 2D self-assembly is initiated by 1D dipolar attraction common in nanometer-sized objects. The dense 1D attachment of Au15 leads to a redistribution of the surface ligands, thus generating asymmetric vdW attraction. The deliberate control of the coordination of dipolar and vdW attraction further allows to manipulate the thickness and morphologies of 2D self-assembly architectures.

Intercalation assembly, characterization and luminescent properties of novel composite material, Tb(III) complex-montmorillonite

Tetrapodal ligand L (2, 2, 2', 2'-tetra[N-benzyl-N-phenyl (acetamide)-2-oxymethyl] n-butyl ether) and complex [TbL] (ClO4)3 are synthesized. The complex ion with tetrapodal ligand L, [TbL]3+ is intercalated into the interlayer space of montmorillonite (MMT) by ion exchanging. The obtained luminescent supramolecular composite material, [TbL]3+-MMT is characterized by elemental analysis, X-ray diffraction, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroseopy. At the same time, the luminescent properties of the material are also studied. The results show that the intercalated material with regular layered structure and the interlayer spacing (d001) approximate to the diameter of the complex ion arranged in the interlayer space of the MMT in the formation of a monolayer emit characteristic green emission of Tb3+ strongly under the excitation of ultraviolet light. It is also found that the relative luminescence intensity, the luminescence monochromatic index and the light stability of the intercalated material are distinctly improved after the [TbL]3+ has been intercalated into the MMT. And the excitation wavelength of the complex is modulated till the red shift occurs in the composite material.

Preparation of hydrotalcite-supported potassium carbonate catalyst by microwave for removing acids from crude oil by esterification

Potassium carbonate was supported on hydrotalcite by microwave radiation and used as catalyst to remove acids from crude oil. To better understand the influence of the preparation method on the properties and activity of the catalyst, a series of catalysts with the same K 2CO 3 content were prepared by impregnation, ultrasonic, microwave radiation and mechanical mixing methods, respectively. Their properties were characterized by XRD, N 2 adsorption–desorption and Hammett indicator-benzene carboxylic acid titration. Moreover, their catalytic activity was tested by esterification deacidification reaction between high-acid crude oil and glycol. In addition, the effect of microwave radiation time and the K 2CO 3 content was also investigated. The presence of carboxyl acid in crude oil and ester in deacidified oil was characterized by FT-IR. It was found that the catalyst with high hydrotalcite crystallinity, well-dispersed K 2CO 3 and more basic sites shows the best deacidification activity. Among the four methods, microwave radiation can provide adequate energy to disperse K 2CO 3 species on the surface of hydrotalcite homogeneously and rapidly, and thus can greatly reduce the contacting time of hydrotalcite and basic K 2CO 3 solution to keep the regular layer structure of hydrotalcite. Furthermore, microwave radiation can produce a high temperature instantaneously, which strengthens the interaction of K + and hydrotalcite to promote the formation of more basic sites. The catalyst loading 15% K 2CO 3 and radiated by microwave for 5 minutes showed superior activity, which can increase the deacidification ratio from 89.2% to 97.7% and decrease the acid number of Suizhong high-acid crude oil from 3.72 to 0.08 mgKOH/g at 200°C, at a reaction time of 2 h and at catalyst and glycol mass ratios to crude oil of 1% and 2%, respectively.

Anwendung der optischen Kohärenztomographie (OCT) bei der Darstellung von Urothelerkrankungen der Harnblase

The technique of optical coherence tomography (OCT) has significantly improved over the last few years. This new diagnostic procedure allows imaging of tissue structure of the bladder wall during cystoscopy with high resolution. The penetration depth of OCT is limited to 2.5 mm. The resolution is approximately 15 microm. Fifty patients with different clinical conditions of the bladder were examined. Altogether 488 OCT images were generated. OCT of normal bladder mucosa clearly shows a differentiation between urothelium, lamina propria, and smooth muscle. Cystitis and metaplasia are characterized by blurring of the laminated structure and thickening of the epithelial layer. In malignant areas there is complete loss of the regular layered tissue structure. OCT improves the diagnosis of flat lesions of the urothelium. It has the potential for facilitating intraoperative staging of malignant areas in the bladder.

Formation of lead sulfide nanoparticles via Langmuir–Blodgett technique

Perovskite type thin films are constructed on hydrophilic quartz substrates from monolayers of long chain alkyl ammonium chloride on the subphase containing a mixture of Pb 2+ and CH 3NH 3 + ions via Langmuir–Blodgett (LB) technique. The deposited film shows typical PbCl-based layered perovskite exciton absorption at about 331 nm. Lead sulfide nanoparticles are formed by reacting these films with H 2S gas. UV–visible absorption spectroscopy and transmission electron microscopy are used respectively to observe the formation and morphology of the nanoparticles with sizes in the range of 10–30 nm. Obtained results indicate an effective way to prepare functional inorganic nanoparticles from regular layered structures.

IN VIVO OPTICAL COHERENCE TOMOGRAPHY FEASIBILITY FOR BLADDER DISEASE

Optical coherence tomography is a new imaging modality capable of imaging luminal surface of biological tissue in the near infrared range with a spatial resolution close to the cellular level. We identified characteristic optical coherence tomography patterns for nonproliferative and proliferative inflammation, and malignant alterations of the bladder. Optical coherence tomography was performed to image the bladder of 66 patients. The probe passed through the operating channel of a cystoscope and was pressed onto the mucosal site of interest. A mucosal biopsy of the image site was obtained. Optical coherence tomography was used to construct 680 images of the bladder and the images were compared with histology slides. Optical coherence tomography images of normal bladder showed 3 layers, namely the mucosa or transitional epithelium, submucosa and smooth muscle. In exudative processes there were poor light scattering areas in the connective tissue layer. Images of bladders with proliferative cystitis revealed nonuniform thickening of the epithelium or hyperplasia. Squamous metaplasia appeared as thicker and less transparent epithelium with a jagged boundary. Images of transitional cell carcinoma were characterized by the complete loss of a regular layered structure of the bladder wall and the penetration depth of optical imaging was slight. This study provides the characteristic optical coherence tomography pattern of nonproliferative and proliferative inflammation, and the characteristic appearance of severe dysplasia and transitional cell carcinoma. This technique may be useful as a guide for biopsy and for assisting in establishing resection margins.

In Situ Coordination of Coumarin 7 with Ag(I) at the Air/Water Interface: Characterization and Function of the Monolayers and Langmuir−Schaefer Films

In situ coordination of coumarin 7 (3-(2‘-benzimidazolyl)-7-N,N-diethylaminocoumarin, CUM7), which has no substituted long alkyl chain, was found to form stable monolayers at the air/water interface with the presence of AgNO3 in the subphase. The monolayers can be transferred onto solid substrates by a Langmuir−Schaefer (LS) method. Surface pressure−area isotherms, UV−vis spectra, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, and X-ray diffraction were used to characterize the monolayer formation and the transferred LS films. The LS film showed regular layer structure. Different color changes were observed for the transferred LS films upon photoirradiation with UV and visible light. The LS films showed a conductivity of ca. 0.1 S cm-1, which is relative large for ultrathin films. It is found that although the metal complex of CUM7 and Ag(I) can be synthesized in homogeneous solutions as a precipitate, it cannot be fabricated into ultrathin films due to its insolubility in organic solvents. The in situ coordination reaction at the air/water interface makes it possible to fabricate and investigate the functional ultrathin film of this metal complex.

Monolayer formation and Langmuir–Blodgett films of benzimidazole derivatives without alkyl chain

The monolayer formation and morphology of two benzimidazole derivatives, 2-phenylbenzimidazole (PhBz) and 2-(2′-pyridyl)benzimidazole (PyBz), which have no alkyl chains, have been investigated. These compounds can form monolayers on subphases containing concentrate AgNO 3. No monolayers are formed on water or subphases containing other ions. Differences are found in the behaviors of the two compounds owing to the different hydrophilicity of the pyridyl and phenyl rings. Similar iceberg-like domains are observed in both the monolayers immediately after spread using a Brewster angle microscopy. The monolayers can be transferred onto solid substrates as X-type LB films. X-ray diffraction shows the regular layer structure of the LB films with long spacings of 1.19 and 1.33 nm for PhBz and PyBz, respectively.

Formation of mono- and multilayers of metal complexes of 4-(((10,12-pentacosadiynoyl)oxy)methyl)pyridine

The monolayer properties of the amphiphile, 4-(((10,12-pentacosadiynoyl)oxy)methyl)pyridine have been studied by measuring the surface pressure–area isotherms. The amphiphile forms stable monolayers at the air–water interface and protonation of the monolayers occurs at pH values of 3.00 or lower. Addition of Cu(II) to the subphase (0.5–50 mM) causes an increase of the pressure ( Π c) at which the phase transition from the liquid-expanded (LE) to liquid-condensed (LC) phase appeared, suggesting that complexation in the monolayer has occurred. This complexation behaviour is strongly influenced by the Cu(II) concentration, the kind of counterion, and the ionic strength of the subphase. Multilayers of the amphiphile can only be built up when the subphase contained Cu(II) ions. The presence of Cu(II) ions is confirmed by means of X-ray photoelectron spectroscopy measurements, from which it can be concluded that indeed complexation in the monolayer has taken place. Fourier transform infrared spectroscopy and small-angle X-ray reflection measurements revealed that the multilayers have a regular layer structure with a bilayer spacing of 41.3 Å. Upon polymerisation by means of exposure to UV light, the regular layer structure of the multilayers is preserved but decreased to 40.5 Å. A maximum degree of polymerisation is reached after 30 min of UV irradiation.

Adhesive liquid‐crystalline polymers

AbstractThe synthesis and characterization of liquid‐crystalline polymers with possible good adhesive properties is reported. These polymers are prepared by alternating copolymerization of maleic anhydride and mesogenic alkenes. The spacer length m is varied (m = 2, 3, 4, 6, 8 and 9) and methoxybiphenyl is used as the mesogenic group. The glass transition temperature decreases and the isotropization temperature increases with spacer length. Depending on the spacer length and temperature, SB and SAd mesophases can be observed. After annealing, spin‐coated films of these polymers show very regular layered structures with a layer spacing similar to that in the bulk.