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Nanoscaled Ti1-xSixN/CrAlN multilayers combining the cutting edges of Ti1-xSixN and CrAlN coatings are currently the focus of attention of researchers. Here, the structural, mechanical, and thermal properties of Ti1-xSixN/CrAlN multilayers with varied Si content were investigated. The hardness values of Ti1-xSixN/CrAlN multilayers are individually enhanced to 30.7 ± 1.0 GPa for x = 0, 36.0 ± 1.3 GPa for x = 0.13, and 35.9 ± 1.5 GPa for x = 0.22 from the 27.4 ± 0.3 GPa for CrAlN due to interfacial strengthening effect. Ti1-xSixN insertion layers retard the thermal decomposition process of CrAlN. After annealing at 1200 °C, the hardness of Ti1-xSixN/CrAlN (x = 0, 0.13, 0.22) multilayers is individually enhanced by ∼6.9, 12.9 and 13.6 GPa from the 18.7 ± 1.1 GPa for Cr0.32Al0.68N. However, Ti1-xSixN insertion layers lead to a drop in the oxidation resistance of CrAlN coatings due to their inferior oxidation resistance. Noticeable is that increasing Si content of Ti1-xSixN/CrAlN multilayers causes a decline in the thickness of oxide scales.

Alloying a fourth element and multilayer architecture are efficient methods to tailor the structure and properties of aluminum-containing transition metal nitrides coatings. Here, we combine Si-addition and multilayer structure to improve the properties of TiAlN coating. Incorporation of Si into TiAlN leads to a nanocomposite structure with TiAlN nanocrystalline encapsulated by amorphous SiNx, and thereby an increased hardness from 29.1 ± 1.0 GPa for Ti0.52Al0.48N to 33.1 ± 1.2 GPa for Ti0.53Al0.38Si0.09N. In order to avoid the formation of undesired wurtzite (w) AlN in Ti0.53Al0.38Si0.09N, the c-Ti0.52Al0.48N template layer (∼5.2 nm) is used to stabilize Ti0.53Al0.38Si0.09N layer (∼7.5 nm) in its metastable cubic structure based on epitaxial growth. The Ti0.52Al0.48N/Ti0.53Al0.38Si0.09N multilayer with an overall cubic structure shows a hardness value of 35.6 ± 0.7 GPa. All coatings exhibit an age-hardening ability due to the spinodal decomposition. A peak hardness value of 36.7 ± 0.8 and 38.2 ± 0.5 GPa is achieved by Ti0.53Al0.38Si0.09N and Ti0.52Al0.48N/Ti0.53Al0.38Si0.09N, respectively, upon annealing at 1000 °C. In contrast, Ti0.52Al0.48N coating exhibits a maximum hardness increase to 33.5 ± 0.8 GPa at 800 °C. Furthermore, the Ti0.53Al0.38Si0.09N and Ti0.52Al0.48N/Ti0.53Al0.38Si0.09N coatings show oxide scales of ∼2.1 and 1.0 μm at 1000 °C for 10 h after exposure to air atmosphere, respectively, whereas the Ti0.52Al0.48N coating has already been completely oxidized at 850 °C.

The toxicity of Rac-metolachlor and S-metolachlor on rice (IIYou92, Oryza sativa L.) seedlings was determined and compared in a hydroponics experiment. The elongation of shoot, main root, and the number of lateral roots were inhibited in both Rac- and S-metolachlor treatments. The 96 h- IC50 of Rac- and S-metolachlor were 12.32 and 9.44 μM for shoot, and 4.69 and 1.75 μM for root, respectively. The content of chlorophyll a, chlorophyll b and total chlorophyll of leaf treated by Rac-metolachlor was higher than that treated by S-metolachlor. The activities of superoxide dismutase, peroxidase, cytochrome P450 2E1, glutathione S-transferase, and the content of glutathione increased after herbicide exposure, and the activities or the content was higher in the S-metolachlor treatment than in the exposure to Rac-metolachlor. Ultrastructural studies revealed that Rac- and S-metolachlor had adverse effects on leaf cells, and S-metolachlor treatment caused higher damage.

Cyclodextrins (CDs) possess a variety of chiral centers and are capable of recognizing enantiomeric molecules through the formation of inclusion complexes. Two types of CDs, α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD), were selected to evaluate the effects of the enantioselective ecotoxicity of racemic metolachlor (Rac-metolachlor) and its S-enantiomer (S-metolachlor) on the freshwater algae Scenedesmus obliquus (S. obliquus) by acute toxicity test. The results showed that the aquatic toxicity of S-metolachlor was higher than Rac-metolachlor and that CDs enhanced the toxicity of metolachlor enantioselectively by increasing the aquatic toxicity of Rac-metolachlor rather than that of S-metolachlor to S. obliquus. The equilibrium constant for Rac-metolachlor-CD complexes was higher than that of S-metolachlor-CDs, which was responsible for the greater aquatic toxicity shift effect of Rac-metolachlor. Thermodynamic studies of CD complexes showed that inclusion for all of the complexes was primarily a spontaneous, enthalpy-driven process. These results will help to understand the preliminary mechanism of shifting aquatic toxicity of metolachlor by CDs and the CDs mediated environmental processes of metolachlor, to correctly apply CDs to chiral pesticides formulation and environmental remediation of chiral contaminants. Chirality, 2012. © 2011 Wiley Periodicals, Inc.

Metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] is a chiral acetanilide herbicide. We investigated its enantioselective interactions, and that of its (S)-isomer, with Penicillium expansum alkaline lipase and phosphatase. UV differential spectroscopy and fluorescence spectrophotometry studies were conducted in phosphate buffered solution at pH 7. Chiral differences in the UV absorption and fluorescence spectra of lipase and phosphatase with metolachlor and its (S)-isomer were detected. The results showed that the interactions of metolachlor and its (S)-isomer with lipase and phosphatase occur statically through complex formation, and enantioselectivity was clearly observed. In addition, both UV absorption and fluorescence spectrophotometry showed that the (S)-isomer interacted more strongly with lipase and phosphatase than metolachlor.