Well-designed Ag/ZnO/3D graphene structure for dye removal: Adsorption, photocatalysis and physical separation capabilities.

In this research, adsorption and photocatalytic degradation process were utilized to remove organic dye from wastewater. To accomplish that, a newly-designed ternary nanostructure based on Ag nanoparticles/ZnO nanorods/three-dimensional graphene network (Ag NPs/ZnO NRs/3DG) was prepared using a combined hydrothermal-photodeposition method. The three-dimensional structure of graphene hydrogel as a support for growth of ZnO nanorods was characterized using field emission scanning electron microscopy (FESEM). In addition, diameter of silver nanoparticles grown on the ZnO nanorods with the average aspect ratio of 5 was determined in the range of 30-80 nm by using transmission electron microscopy (TEM). The X-ray diffraction (XRD) pattern was revealed hexagonal Wurtzite structure of ZnO nanorods and the (1 1 1) lattice plane of the face-centered cubic (FCC) of the silver nanoparticles. The dye adsorption capacity of the synthesized 3DG was evaluated at about 300 mg/g using kinetic study. The photocatalytic dye degradation under both UV and visible light irradiation exhibited an enhanced activity of the prepared ternary Ag/ZnO/3DG sample in comparison to ZnO/3DG and 3DG structures. Different charge-carrier scavengers were utilized to elucidate the synergistic effect of adsorption and visible-light photocatalytic degradation mechanism for dye removal. The facile photocatalyst recovery as well as the high elimination rate of dye is promising for future applications such as efficient removal of organic contaminants from industrial wastewater under solar irradiation.

In situ forming interpenetrating hydrogels of hyaluronic acid hybridized with iron oxide nanoparticles.

Four derivatives of hyaluronic acid (HA) bearing thiol (HA-SH), hydrazide (HA-hy), 2-dithiopyridyl (HA-SSPy), and aldehyde groups (HA-al) respectively were synthesized. Thiol and 2-dithiopyridyl as well as hydrazide and aldehyde make up two chemically orthogonal pairs of chemo-selective functionalities that allow in situ formation of interpenetrating (IPN) disulfide and hydrazone networks simultaneously upon the mixing of the above derivatives at once. The formation of IPN was demonstrated by comparing it with the formulations of the same total HA concentration but lacking one of the reactive components. The hydrogel composed of all four components was characterized by a larger elastic modulus than those of the control single networks (either disulfide or hydrazone) and the three component formulations gave the softest hydrogels. Moreover, a hydrazone cross-linkage was designed to contain a 1,2-diol fragment. This allowed us to partially disassemble one type of network in the IPN leaving another one unaffected. In particular, treatment of the IPN with either sodium periodate or dithiothreitol resulted in disassembly of the hydrazone and disulfide networks respectively and thus softening of the hydrogel. Contrarily, the single network hydrogels completely dissolved under the corresponding conditions. In corroboration with this, enzymatic degradation of the IPN by hyaluronidase was also substantially slower than the degradation of the single networks. In order to further improve the mechanical properties of the elaborated injectable IPN, it has been in situ hybridized with iron oxide nanoparticles (IONPs). The mesh size of the IPN was smaller than the size of the IONPs resulting in the retention of nanoparticles in the matrix under equilibrium swelling conditions. However, these nanoparticles were released upon enzymatic degradation suggesting their use as MRI tags for non-invasive tracking of the hydrogel material in vivo. Additionally, this injectable hybridized hydrogel with encapsulated IONPs can be used in hyperthermia cancer therapy.