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The design of heme and non-heme active centers, which resemble peroxidase enzymes, has recently received a significant attention. Herein, a cystein-metal complex was designed and encapsulated in a vesicular mixture (1:4; SDS/DTAB) in order to imitate a chloroperoxidase (CLP) enzyme via chlorination of thionine at pH 3. This artificial enzyme behaved both as a catalase and CLP at pH 3, and as a peroxidase at pH 1. The shape of the metallo-vesicular catalyst at each pH value was obtained by dynamic light scattering, and was confirmed by transmission electron microscopy (TEM). The different fluidities as interior structure property of catalyst aggregates at pH 3 and 1 were obtained by differential scanning calorimetry (DSC). IR, 1 H and 13 C NMR spectroscopies were utilized to investigate the structural properties of the vesicular catalyst. These studies demonstrated that the cysteine/iron (III) center acted as a multifunctional catalyst. In addition, the sulfur and ammonium moieties of L-Cys interacted in the presence of metal ion at pH 1. However, the ammonium side chain was replaced with the carboxylate group at pH 3. Collectively, we engineered two distinct vesicular cysteinate-Fe 3+/2+ complexes, which functioned as a pH-switchable catalyst.

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KCl-induced high-temperature corrosion behavior of four HVAF-sprayed Ni-based coatings (Ni21Cr, Ni5Al, Ni21Cr7Al1Y and Ni21Cr9Mo) under KCl deposit has been investigated in ambient air at 600°C up to 168 h. The coatings were deposited onto 16Mo3 steel-a widely used boiler tube material. Uncoated substrate, 304L and Sanicro 25 were used as reference materials in the test environment. SEM/EDS and XRD techniques were utilized to characterize the as-sprayed and exposed samples. The results showed that the small addition of KCl significantly accelerated degradation to the coatings. All coatings provided better corrosion resistance compared to the reference materials. The alumina-forming Ni5Al coating under KCl deposit was capable of forming a more protective oxide scale compared to the chromia-forming coatings as penetration of Cl through diffusion paths was hindered. Both active corrosion and chromate formation mechanisms were found to be responsible for the corrosion damages. The corrosion resistance of the coatings based on the microstructure analysis and kinetics had the following ranking (from the best to worst):

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