Rational phase transformation and morphology design to optimize oxygen evolution property of cobalt tungstate.

In this work, a facile and feasible soft template method with the aid of buffer solution is successfully applied to synthesize high-order mesoporous cobalt tungstate for the first time. Attributing to the regulation of reaction solution's pH value and the existence of template, the phenomenon of phase transformation occurs, and high-order mesoporous structure is formed. Because of the variation of phase and morphology, only 448 mV can deliver a current density of 10 mA cm-2 with a small Tafel slope (61 mV dec-1) for mesoporous cobalt tungsten oxide hydroxide, while the cobalt tungstate nanoparticles cannot satisfy the basic demand of electrocatalysts. Herein, rational phase transformation and morphology design can significantly affect the property of oxygen evolution, which can provide vast opportunities to turn into candidates for the novel oxygen evolution catalyst.

Facile Synthesis of Flower-Like Copper-Cobalt Sulfide as Binder-Free Faradaic Electrodes for Supercapacitors with Improved Electrochemical Properties.

Supercapacitors have been one of the highest potential candidates for energy storage because of their significant advantages beyond rechargeable batteries in terms of large power density, short recharging time, and long cycle lifespan. In this work, Cu-Co sulfides with uniform flower-like structure have been successfully obtained via a traditional two-step hydrothermal method. The as-fabricated Cu-Co sulfide vulcanized from precursor (P-Cu-Co sulfide) is able to deliver superior specific capacitance of 592 F g-1 at 1 A g-1 and 518 F g-1 at 10 A g-1 which are surprisingly about 1.44 times and 2.39 times higher than those of Cu-Co oxide electrode, respectively. At the same time, excellent cycling stability of P-Cu-Co sulfide is indicated by 90.4% capacitance retention at high current density of 10 A g-1 after 3000 cycles. Because of the introduction of sulfur during the vulcanization process, these new developed sulfides can get more flexible structure and larger reaction surface area, and will own richer redox reaction sites between the interfaces of active material/electrolyte. The uniform flower-like P-Cu-Co sulfide electrode materials will have more potential alternatives for oxides electrode materials in the future.

Novel Luminescent Multilayer Films with Magnetic and Electronic Microenvironment.

Luminescent multilayer thin films (MTFs) based on exfoliated magnetic layered double hydroxides (LDHs) with/without oppositely-charged montmorillonite (MMT) nanosheets were fabricated via layer-by-layer self-assembly method. In this work, we chose transition metal-bearing LDHs nanosheets to offer magnetic field for the chromophores. At the same time, the oppositely-charged nanosheets can provide additional electronic microenvironment (EME). As a result, both EME and magnetic field have remarkable influences on enhancing the luminescent lifetimes of chromophores, which suggests a new pathway to develop the novel light-emitting materials and optical devices.

Assembly of luminescent ordered multilayer thin-films based on oppositely-charged MMT and magnetic NiFe-LDHs nanosheets with ultra-long lifetimes.

In this present report, luminescent ordered multilayer thin films (OMFs) based on oppositely-charged inorganic nanosheets and the different oppositely-charged chromophores were fabricated via layer-by-layer assembly method. Exfoliated layered double hydroxides (LDHs) and montmorillonite (MMT) nanosheets with opposite charges can be expected to provide a pseudo electronic microenvironment (PEM) which has not been declared in previous literatures, and transition metal-bearing LDHs nanosheets can offer an additional ferromagnetic effect (FME) for the chromophores at the same time. Surprisingly, the luminescent lifetimes of those OMFs with PEM and FME are significantly prolonged compared with that of the pristine chromophores, even much longer than those of OMFs without oppositely-charged and ferromagnetic architecture. Therefore, it is highly expected that the PEM and FME formed by oppositely-charged and transition metal-bearing inorganic nanosheets have remarkable influence on obtaining better optical property, which suggests a new potential way to manipulate, control and develop the novel light-emitting materials and optical devices.

Binding sites of chlorpheniramine on 1:1 layered kaolinite from aqueous solution.

Interactions between chlorpheniramine (CP), an antihistamine drug used to treat allergy, and kaolinite in aqueous solution were investigated under batch studies and molecular simulations. The CP adsorption was relatively fast with a large rate constant. The CP adsorption capacity on kaolinite was 25 mmol/kg, about the same magnitude of the cation exchange capacity of kaolinite. Molecular dynamic simulation showed that the edges of kaolinite were responsible for the uptake of CP, while a net repulsive interaction between the basal plane and CP molecules was obtained. As the broken bond effect of kaolinite was strongly affected by solution pH via protonation-deprotonation of kaolinite edges, a higher CP adsorption was achieved under neutral to weak alkaline solution. It was the charge density, rather than the surface area, that ultimately controlled the amount of CP adsorption on kaolinite.

Probing the interactions between chlorpheniramine and 2:1 phyllosilicates.

Interactions between chlorpheniramine (CP), an antihistamine drug used to treat allergy, and 2:1 phyllosilicates were studied under batch kinetic and different solution conditions to investigate the effect of charge density of the substrates on CP removal from solution. The CP removal by Na-montmorillonite was instantaneous, with a very large rate constant and a fast rate, reaching a capacity of 0.64 mmol/g, compared to its cation exchange capacity of 0.85 mmol(c)/g. In contrast, CP removal by talc was 10 times lower at 0.06 mmol/g. Stoichiometric desorption of exchangeable cations accompanying CP removal by Na-montmorillonite confirmed cation exchange as the dominant interaction mechanism. Solution pH had a minimal effect on CP removal by Na-montmorillonite until pH 11. On the contrary, a slight increase in CP removal by talc was observed as the solution pH increased, due to increased negative charges on the pH-dependent surfaces of talc. Interactions between CP and Na-montmorillonite occurred on both external and interlayer sites, resulting in a d-spacing expansion from 12.5 Å to 15.2 Å. In contrast, interactions between CP and talc were only limited to the external surfaces. It was the charge density that ultimately controlled the amount of CP removal by 2:1 phyllosilicates. Thus, montmorillonite offers a superior option for the removal of cationic drugs from aqueous solution.

Theoretical analyzing of monomers adsorbing in nano-slits.

A revised model based on Aranovich-Donohue Theory was built in this paper and was used to indicate the adsorbing behaviors of monomers in nano slits. This work tried to establish a theoretical model and get the fundamental mechanisms of the in situ-monomer-intercalation process which is the most common production method of polymer-layer silicate intercalated nanocomposite. According to the results, the multilevel adsorption and 3D phase transition phenomenon in nano slits predicted by Aranovich-Donohue Theory do not exit in reality. They are probably aroused by system errors caused by simple mean field approximation treatments. The nano slits have obvious boundary effects on density profile distribution of monomers. When the pore size increase, the density differences will be diminished. The adsorbing amounts will go up sharply in a narrow low-bulk-concentration region and will decrease rapidly at most bulk-concentration-regions accompanied by the increasing of interaction energies of adsorbates. This should attribute to the capillary condensation phenomenon. The newly established model will be definitely helpful to reveal the fundamental mechanisms of in situ-monomer-intercalation process for polymer-layer silicate intercalated nanocomposite.

Modeling of microorganisms transport in a cylindrical pore.

A mathematical model accounting for key parameters as microbial propagation, metabolite formation, dispersion, microbial chemotaxis and water flooding has been proposed to simulate the transport of microorganisms and their metabolites in a cylindrical pore with oil adhered to its inside surface. The model focuses on the transport and the concentration distributions of microorganisms and their metabolites in the cylindrical pore, especially the concentrations that on the oil-water interface. Results from the present model indicate that microorganisms and their metabolites assembled on the oil-water interface during the water flooding process, and the concentration gradients of microorganisms and their metabolites from the pore center region up to the oil-water interface in radial direction of the cylindrical pore were consequently formed. Equilibrium concentrations of microorganisms and their metabolites in the cylindrical pore were obtained when water flow rate within a certain scope, and there existed a critical water flow rate at which the maximum equilibrium concentration of microorganisms on the oil-water interface was developed. Investigations carried out in this study may provide better understanding on the transport mechanism of microorganisms in porous media.