Four sulfur-oxidizing bacteria (Thiobacillus thioparus, Acidithiobacillus thiooxidans PTCC1717, Acidithiobacillus ferrooxidans PTCC1646, and Acidithiobacillus ferrooxidans PTCC1647) were used as biorecognition elements in a hydrogen sulfide biosensing system. All the experiments were performed in 0.1 M phosphate buffer solution containing 1-20 ppm H2S with optimum pH and temperature for each species. Although H2 S was applied to the biosensing system, the dissolved O2 content decreased. Dissolved O2 consumed by cells in both free and immobilized forms was measured using a dissolved oxygen sensor. Free bacterial cells exhibit fast response (<200 Sec). Immobilization of the cells on polyvinyl alcohol was optimized using an analytical software. Immobilized A. ferrooxidans and A. thiooxidans retained more than 50% of activity after 30 days of immobilization. According to the data, A. thiooxidans and A. ferrooxidans are appropriate species for hydrogen sulfide biosensor.

No abstract

Analcime shell-nickel ferrite core microspheres were decorated with Pd and Pt nanoparticles with the aid of an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6). The samples thus prepared were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), nitrogen adsorption-desorption isotherms, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) methods. The XRD patterns confirmed the growth of a zeolitic layer on the surface of the magnetic cores. The thermogravimetric analysis (TGA) curve clearly indicated the thermal decomposition of the loaded IL, which confirmed the presence of BMIM-PF6 in the structures. In addition, EDX analysis indicated that the samples contained 2.5 mass % of noble metal. The metallic species can be adsorbed on the modified surface and/or penetrate into the zeolitic channels in the structures. The results indicate that the X-IL/An/S/NF (X = Pt or Pd) metallic nanoparticles supported core-shell catalystssamples were able to catalyse the selective oxidation of cyclohexene to 2-cyclohexene-1-ol under the induced conditions. The catalysts continued to be active after recycling up to 5 times. Eventually, a suitable mechanism was proposed for the selective oxidation of cyclohexene over the catalysts.