Green Assembly of Covalently Linked BiOBr/Graphene Composites for Efficient Visible Light Degradation of Dyes.

A novel high-performance BiOBr@graphene (BiOBr@G) photocatalyst with a new assembly structure had been demonstrated using a facile hydrothermal method through chemical bonding of reduced graphene oxide and structure-defined BiOBr flakes for improving charge separation and transfer performance, which were first synthesized at room temperature in immiscible solvents without corrosive acids. The prepared samples were characterized, and the BiOBr@G composite realized an efficient assembly portfolio of graphene and BiOBr flakes with defined structures, verified by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman and X-ray photoelectron spectroscopy (XPS), in which BiOBr flakes were covalently linked with the assembled graphene sheets through the Bi-C bond. This composite exhibited remarkable visible light absorbance and efficient photoinduced charge splitting characteristics in comparison with those of pure BiOBr, as established by DRS absorption, photoluminescence radiation, and photocurrent study. Hence, a very small amount (5 mg) of the BiOBr@G composite displayed a complete photodegradation effect on the rhodamine B dye under only 15 min of visible light excitation, which was three times faster than that of pure BiOBr and extremely superior to that of commercial P25. This was probably ascribed to the well-defined BiOBr structure itself, elevated light absorbance, and Bi-C chemical bond inducing quick charge separation and transfer in the BiOBr@G composite. Additionally, investigations on the photocatalytic mechanism displayed that the photogenerated holes in the BiOBr valence band and derivative superoxide radicals played vital roles in the photodegradation of RhB dyes, as reinforced by the electron spin resonance method, where the covalent linking of BiOBr and graphene served as an effective pathway for charge transportation.

Exogenous l-ascorbic acid regulates the antioxidant system to increase the regeneration of damaged mycelia and induce the development of fruiting bodies in Hypsizygus marmoreus.

Hypsizygus marmoreus is an important commercial edible fungus, but the lack of basic studies on this fungus has hindered further development of its commercial value. In this study, we found that the treatment of damaged vegetative mycelia with 1 mM l-ascorbic acid (ASA) significantly increased the antioxidant enzyme activities (GPX, GR, CAT and SOD) and antioxidant contents (GSH and ASA) and reduced the ROS levels (H2O2 and O2-) in mechanically damaged mycelia. Additionally, this treatment increased mycelial biomass. At the reproductive stage, our results demonstrated that the treatment of damaged H. marmoreus mycelia with 2.24 mM ASA significantly increased the antioxidant enzyme activities (GPX, GR, GST, TRXR and CAT), endogenous ASA contents and GSH/GSSG ratios in different developmental stages and significantly decreased the MDA and H2O2 contents. Furthermore, this study showed that the expression levels of the antioxidant enzyme genes were consistent with the enzyme activities. Damaged mycelia treated with ASA regenerated 2-3 d earlier than the control group and showed significantly enhanced fruiting body production. These results suggested that exogenous ASA regulated mycelia intracellular ASA content to increase mycelial antioxidant abilities, induce the regeneration of damaged mycelia and regulate the development of fruiting bodies in H. marmoreus.