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The aim of this work was to evaluate effects of endophytic bacterium inoculation on plant growth and assess the possible mechanism of endophyte in heavy metal phytoremediation. Seeds of Solanum nigrum L. were inoculated with endophyte Serratia nematodiphila LRE07 and were subjected to Cd in the growing medium. Cd produced a significant inhibition on plant growth and a reduction in the content of photosynthetic pigments. The inoculation of endophytic bacterium alleviated the Cd-induced changes, resulting in more biomass production and higher photosynthetic pigments content of leaves compared with non-symbiotic ones. The beneficial effect was more obvious at relatively low Cd concentration (10 μM). Based on the alteration of nutrient uptake and activated oxygen metabolism in infected plants, the possible mechanisms of endophytic bacterium in Cd phytotoxicity reduction can be concluded as uptake enhancement of essential mineral nutrition and improvement in the antioxidative enzymes activities in infected plant.

Ethylene polymerization was performed with the TiO2 nanotube supported metallocene catalytic system. The effects of Al/Zr molar ratio and time in polymerization on the catalytic behavior of the catalysts and the morphologies of the polyethylene were investigated. The nanofibers, floccules and nanosheets of polyethylene were obtained by controlling the polymerization conditions. Because the nanotubes confined the direction of propagation of the polyethylene chains, nanofibers were attained by extrusion polymerization, while the amount of floccules increased with extended polymerization time and nanosheets were mainly produced at high Al/Zr molar ratios. The possible correlation between the polymerization conditions and polyethylene morphologies was elucidated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011.

Heavy metal bioremediation by a multi-metal resistant endophytic bacteria L14 (EB L14) isolated from the cadmium hyperaccumulator Solanum nigrum L. was characterized for its potential application in metal treatment. 16S rDNA analysis revealed that this endophyte belonged to Bacillus sp. The hormesis of EB L14 were observed in presence of divalent heavy metals (Cu (II), Cd (II) and Pb (II)) at a relatively lower concentration (10 mg/L). Such hormesis was the side effect of abnormal activities increases of ATPase which was planned to provide energy to help EB L14 reduce the toxicity of heavy metals by exporting the cations. Within 24 h incubation, EB L14 could specifically uptake 75.78%, 80.48%, 21.25% of Cd (II), Pb (II) and Cu (II) under the initial concentration of 10 mg/L. However, nearly no chromium uptake was observed. The mechanism study indicated that its remediation efficiencies may be greatly promoted through inhibiting the activities of ATPase. The excellent adaptation abilities and promising remediation efficiencies strongly indicated the superiority of this endophyte in heavy metal bioremediation at low concentrations, which could be useful for developing efficient metal removal system.

Trinitrotoluene, usually known as TNT, is a kind of chemical explosive with hazardous and toxic effects on the environment and human health. National and societal security concerns have dictated an increasing need for the analytical detection of TNT with rapidity, high sensitivity and low cost. This work demonstrates a novel method using L-cysteine-capped CdTe quantum dots (QDs) to assay TNT, based on the formation of a Meisenheimer complex between TNT and cysteine. The fluorescence (FL) of quantum dots quench because electrons of the QDs transfer to the TNT molecules via the formation of a Meisenheimer complex. TNT can be detected with a low detection limit of 1.1 nM. Studies on the selectivity of this method show that only TNT can generate an intense signal response. The synthesized QDs are excellent nanomaterials for TNT detection. In addition, TNT in soil samples is also analyzed by the proposed method.

We report a novel method for biological thiols detection using ssDNA/silver nanoparticles system. The adsorbing ssDNA supplies silver nanoparticles high density charge to rescue nanoparticles from aggregation induced by salt. However, homocysteine (cysteine or glutathione) is conjugated more powerfully than ssDNA to AgNPs via Ag-S bond, which holds back ssDNA binding to AgNPs surface. When salt is added, AgNPs aggregation occurs and the corresponding color changes from yellow to brown after these biological thiols is introduced. A high sensitivity can be achieved using salt as an amplifier to assay thiols. In our study, a favorable linear correlation between the A(0)/A(x) ratio and homocysteine concentration was obtained in the range of 10 to 500 nM with a low detection limit of 10 nM, indicating that homocysteine could be analyzed at low concentration. A concentration as low as 300 nM homocysteine caused a visible color change. As well as, cysteine and glutathione can be detected at a detection limit of 50 nM and 100 nM, respectively. In addition, study on the selectivity of this method shows that only homocysteine, cysteine and glutathione can generate signal response.