Xinglong Luan

Fabrication and enhanced dielectric properties of graphene–polyvinylidene fluoride functional hybrid films with a polyaniline interlayer

Graphene–polyvinylidene fluoride hybrid films (GPNs–PVDF) with a polyaniline (PANI) interlayer are fabricated by a facile and effective process. The morphology of the graphene–polyaniline nanoflakes (GPNs) is examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and the interaction between graphene and PANI is investigated by Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The GPNs have a layered structure resembling a cake with the graphene sheets sandwiched between the PANI layers. The GPNs have a uniform morphology which can be controlled by adjusting the ratio of PANI to graphene. The PANI inter-layer plays an active role in the dielectric properties of the GPNs–PVDF composites which have low dielectric loss, high breakdown field, and large energy density. The enhanced dielectric performance originates from the insulating PANI layer which not only ensures good dispersion of graphene sheets in the PVDF but also acts as an inter-particle barrier to prevent direct contact with the graphene sheets.

Molecularly Selective Regulation of Delivery Fluxes by Employing Supramolecular Interactions in Layer-by-Layer Films

The molecularly selective regulation of molecular fluxes in a biomaterial that delivers multiple chemical species simultaneously is still beyond the reach of materials scientists. A delivery material was developed by means of the layer-by-layer (LbL) technique. This material discriminatively regulates the delivery flux of bioactive small molecules, as represented by a peptide containing the RGD fragment and the chemotherapy drug doxorubicin (DOX). Molecularly selective flux regulations in LbL films are realized through fast, reversible supramolecular interactions between cyclodextrin and its guests. The mechanism underlining the delivery strategy is that supramolecular interactions promote molecular loading and slow down diffusion-dependent release. In a preliminary survey of materials parameters, a maximum difference in cell viability between healthy human bronchial epithelial cells and cancer cells (A549) was realized.

Bio-inspired Dynamic Gradients Regulated by Supramolecular Bindings in Receptor-Embedded Hydrogel Matrices

Abstract The kinetics of supramolecular bindings are fundamentally important for molecular motions and spatial–temporal distributions in biological systems, but have rarely been employed in preparing artificial materials. This report proposes a bio‐inspired concept to regulate dynamic gradients through the coupled supramolecular binding and diffusion process in receptor‐embedded hydrogel matrices. A new type of hydrogel that uses cyclodextrin (CD) as both the gelling moiety and the receptors is prepared as the diffusion matrices. The diffusible guest, 4‐aminoazobenzene, quickly and reversibly binds to matrices‐bound CD during diffusion and generates steeper gradients than regular diffusion. Weakened bindings induced through UV irradiation extend the gradients. Combined with numerical simulation, these results indicate that the coupled binding–diffusion could be viewed as slowed diffusion, regulated jointly by the binding constant and the equilibrium receptor concentrations, and gradients within a bio‐relevant extent of 4 mm are preserved up to 90 h. This report should inspire design strategies of biomedical or cell‐culturing materials.