Yongjuan Wang

Template-controlled fabrication of hierarchical porous Zn–Al composites with tunable micro/nanostructures and chemical compositions

The properties of materials are largely determined by the microstructures and components of materials. The design of layered double hydroxide (LDH) based composites has garnered much interest as a way of fabricating novel multiscale architectures with tunable micro/nanostructures and chemical compositions. The present study aims at exploiting the Zn–Al composites for controlled synthesis of multi-scale structures and multi-component materials. Firstly, microscaled Al2O3 fibers are successfully fabricated via a simple, convenient, and cost-effective biotemplate method employing paper fibers as bio-templates. Then, the multi-scale architectures are designed by an in situ growth method, which involves direct growth of nanoscaled LDH platelets on the surfaces of Al2O3 fibers. Finally, the multi-component LDH based materials are prepared based on the controlled crystal growth of LDHs and ZnO. The microstructure, morphology, and textural properties of the as-prepared samples are characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption/desorption. The experimental results show that the longer reaction times are favorable for the crystal growth of LDHs, and the higher hydrothermal temperatures are favorable for the formation of ZnO. This study shows that the design of multi-scale structures and multi-components Zn–Al composites can be extended for the preparation of other hierarchical LDH based materials with controlled morphological and tunable chemical compositions for separation, catalysis, adsorption, sensor, and optical applications.

Two-dimensional ultrathin nanosheets of Ni–In-layered double hydroxides prepared in water: enhanced performance for DNA adsorption

This work describes a facile approach for the delaminating of Ni–In-layered double hydroxides (LDHs) by the intercalation of acetate anions in the LDHs gallery using co-precipitation method. The acetate-intercalated Ni–In LDHs exhibited swelling behavior in water and delaminated into semitransparent suspensions on the action of water. The transmission electron microscopy (TEM) and atomic force microscopic (AFM) observations revealed the formation of unilamellar LDHs nanosheets. This simple method did not need reflux at high temperatures, overcoming the deficiency of using organic solvents, resulting in a steady colloidal suspension of 2D nanosheets. The unique properties of 2D ultrathin nanosheets with full access to the positively charged activity sites make them attractive in terms of the improvement of DNA adsorption. The effect of dosage on the adsorption of DNA and the adsorption isotherm were investigated in detail. The equilibrium data were found to be well described by both the Langmuir and Freundlich models. Based on the mechanism of adsorption, the adsorption sites of exfoliated nanosheets can be easily occupied by highly negatively charged small anions through electrostatic interactions. The adsorbed DNA can be released via the addition of a hydrogen phosphate solution.