No abstract

Chromium present in the forms of Cr(VI) or Cr(III) in soils. Since the toxicity and mobility of Cr(VI) are higher than those of Cr(III), it would be important to estimate soil Cr(VI) accurately in order to assess the phytotoxicity of Cr. Soil redox potential can influence the distribution of Cr between Cr(VI) and Cr(III) forms, and thus an in situ method which is not affected by the soil redox condition is needed for determining Cr(VI) availability in paddy fields. In this study, the Cu-saturated selective ion exchange resin (DOWEX M4159), serving as an infinite sink, was embedded in soils to extract available Cr(VI) from three representative saturated soils with different amounts of Cr(VI). The results suggested that Cr(VI) reduction occurred in the flooded soils, and the acid environment favored the adsorption and reduction of Cr(VI). There was a significant dose-response relationship between the soil resin-extractable Cr(VI) and the plant height of rice seedlings for test soils. The experimental results suggested that the embedded selective ion exchange resin method could be a suitable in situ method for assessing the phytotoxicity of Cr in flooded soils.

We demonstrate a molecular approach of tuning the magnetic properties of ferromagnetic ͑FM͒ thin films by reversing the functional groups of the organic underlayer. For the CoFe/Langmuir-Blodgett ͑LB͒ film system, we find that the coercivity of CoFe thin films ͑from 4 to 10 nm͒ made on hydrophobic surfaces is significantly enhanced whereas that on hydrophilic surfaces remains unchanged, as compared with the films directly on glass substrates. These findings suggest an alternative way for tuning the magnetic properties of the FM layer by LB film in which the functional groups play an important role.

Applying molecular-level technique to the construction of molecular spin valves is a challenging issue in organic spintronics, in which the magnetoresistive performance is highly sensitive to the device's local contact geometry. Here, we propose a molecular spin-valve design of largearea molecular junction to reduce the geometrical impact. Room-temperature tunneling magnetoresistance and well-defined parallel/antiparallel states are achieved in the spin valve with a molecular spacer. The results hold promise for the development of future molecular-level nonvolatile electronic devices.