Single-crystalline Ag_(2)Se complex nanostructures have been synthesized via a solvothermal route in which selenophene(C4H4Se)as a selenylation source reacts with AgNO3 at a temperature of 240°C.An orthorhombic phaseβ-Ag_(2)Se nanostructure was identified by X-ray diffraction(XRD),Raman spectroscopy,field emission scanning electron microscopy(FE-SEM),high resolution transmission electron microscopy(HRTEM),and photoluminescence(PL)spectroscopy.The wettability of the as-synthesizedβ-Ag_(2)Se nanostructure was studied by measurement of the water contact angle(CA).Static water CA values of over 150°were obtained,which can be attributed to theβ-Ag_(2)Se complex nanostructure having a combination of micro-and nanostructures.The superhydrophobic Ag_(2)Se nanostructure may find applications in self-cleaning.Additionally,the photocatalytic activity of the as-synthesizedβ-Ag_(2)Se nanostructure was evaluated by photodegradation of rhodamine B(RhB)dye under ultraviolet(UV)light irradiation.
Brassica chinensis L. was chosen and exposed to different concentrations of Cd exposure to evaluate its Cd-accumulating capacity and its potential cellular defensive mechanisms. Cd accumulation in the shoots and roots of B. chinensis was up to 1348.3±461.8 and 3761.0±795.0 mg per killogram of dry weight, respectively, under 200 μmol/L of Cd exposure. Increasing Cd accumulation in the plant was accompanied by rapid accumulation of phytochelatins (PCs), and the sequestration of Cd by PCs provided a primary cellular mechanism for Cd detoxification and tolerance of B. chinensis. Furthermore, malondialdehyde formation, hydrogen peroxide content and antioxidative enzyme activities such as superoxide dismutase, catalase, guaiacol peroxidase and ascorbate peroxidase were observed in the shoots of Cd-stressed B. chinensis. Increasing enzyme activities in response to concentrations of 5 to 50 μmol/L Cd showed an efficient defense against oxidative stress, suggesting that the antioxidative system was a secondary defensive mechanism. These resulted in reduced free Cd damage and enhanced Cd accumulation and tolerance. Glutathione plays a pivotal role in these two detoxification pathways. In general, these results suggested that PCs and the antioxidative system are synergistic in combatting Cd-induced oxidative stress and that they play important roles in Cd detoxification of B. chinensis, and also give a deep understanding of the natural defensive mechanisms in plants under heavy metal stress.
