Effect of a new hydrophobically modified polyampholyte on the formation of inverse microemulsions and the preparation of gold nanoparticles

A new regular polyampholyte, namely poly-(N,N-dially-N,N-dimethylammonium-alt-N-octyl-maleamic carboxylate), was synthesized by alternating free radical copolymerization. The influence of the added polymer on the range of the inverse micellar region (L(2) phase) of a SDS-based system was investigated. The phase behavior as well as conductivity measurements indicate that the polymer, which forms hydrophobic microdomains, is located more in the water core of the microemulsion droplets rather than at the interface of the surfactant film. The polyampholyte proved to be an efficient reducing and stabilizing agent for the formation of gold colloids. The process of nanoparticle formation was investigated in the absence of any other reducing agent, in water as well as in the microemulsion template phase. In both cases, nanoscalic gold particles can be synthesized, while the adsorption of the polymer on the particle surface prevents their aggregation due to electrosteric stabilization.     

Open‐Pore Two‐Dimensional MFI Zeolite Nanosheets for the Fabrication of Hydrocarbon‐Isomer‐Selective Membranes on Porous Polymer Supports

Two‐dimensional zeolite nanosheets that do not contain any organic structure‐directing agents were prepared from a multilamellar MFI (ML‐MFI) zeolite. ML‐MFI was first exfoliated by melt compounding and then detemplated by treatment with a mixture of H₂SO₄ and H₂O₂ (piranha solution). The obtained OSDA‐free MFI nanosheets disperse well in water and can be used for coating applications. Deposits made on porous polybenzimidazole (PBI) supports by simple filtration of these suspensions exhibit an n‐butane/isobutane selectivity of 5.4, with an n‐butane permeance of 3.5×10^?7 mol m^?2 s^?1 Pa^?1 (ca. 1000 GPU).     

Transfer assessment of fipronil residues from feed to cow milk

Fipronil, a phenylpyrazole insecticide introduced for pest control on a broad range of crops, can also affect non-target insects such as honeybees. More widely, non-target environment such as milk produced by dairy cows fed with maize silage from treated seeds (=silage T) can be affected. To assess the potential transfer of fipronil residues (sulfone, sulfide, fipronil, desulfinyl and amide), a methodology including gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) analysis was developed and validated according to the 2002/657/EC decision, in order to reach a level of quantification below 0.1 μg L⁻¹ in milk and 0.1 μg kg⁻¹ in plants. Twelve dairy cows were fed with silage T during 4 months. Concentration of fipronil in treated seeds was estimated at 1 g kg⁻¹, whereas silage from these seeds contained 0.30 ± 0.05 μg kg⁻¹ of dry material of fipronil, 0.13 ± 0.03 μg kg⁻¹ of dry material of sulfone. Sulfide residues were below the limit of quantification. Silage from untreated seeds (=silage U) presented traces of fipronil and sulfone, respectively at 0.04 ± 0.06 and 0.02 ± 0.03 μg kg⁻¹ of dry material. Contribution of fipronil residues from supplies was insignificant. During administration of silage T, only sulfone residues were quantified in milk. The average concentration was 0.14 ± 0.05 μg L⁻¹. Before and after administration, sulfone residues were detected but not quantifiable (<0.025 μg L⁻¹). Our results suggest a transfer of fipronil from feed to milk under its sulfone form. Moreover, traces of fipronil residues in maize U, soya, wheat and straw show a diffuse contamination of this pesticide in the environment.     

Validity limits of the superposition principle when applied to reactions the kinetics of which is diffusion controlled

The superposition principle which is commonly used to solve the Smoluchowsky equation can be proved to be unreliable by elementary calculations applied to a particular example. But the practical kinetic consequences are small and usually hidden whithin experimental errors.

---

, , , , . , .