Defect-mediated nonradiative recombination in traditional semiconductors, such as porous graphene, tremendously lowers the fluorescence emission, thus greatly restricting their applications in more extensive fields. Here, we report that the fluorescence emission of porous graphene with a high defect density has a giant enhancement (about two orders of magnitude) by a direct and simple fluorination strategy, showing a fine defect-tolerance characteristic. Meanwhile, the corresponding fluorocarbon bonds with excellent thermostability (over 500 °C in N even air) also bring about good stability.
View Article and Find Full Text PDFInspired by the gradient structure of articular cartilage, a poly(vinyl alcohol) (PVA)-based composite hydrogel with a biomimetic gradient structure as an artificial cartilage replacement was constructed by an extrusion 3D printing technique. The influence of the concentration and composition of the PVA-based solution on its rheological behavior and printability was studied, and the improvement mechanism for the 3D printing accuracy of the hydrogel was explored: introduction of GO or GO-HA gave rise to weakened inter-molecular hydrogen bonds and reduced entanglement density simultaneously, and the dynamic viscosity was highly improved. Therefore, the solution exhibited enhanced shear-thinning behavior in the printing shear rate range and a reduced Barus effect, thus highly improving the printability and printing accuracy of the samples.
View Article and Find Full Text PDFBackground: In order to develop starch-based superabsorbent polymers (SAPs) with high water absorbency, both acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were graft copolymerized onto cassava starch, and St-g-AA-AMPS SAP was successfully synthesized. The effect of AA/AMPS molar ratio on the structure and swelling property of SAP was investigated.
Results: Introduction of AMPS units improved the storage modulus and crosslinking density of St-g-AA-AMPS SAP, and was beneficial in forming a perfect network structure.