Multicomponent nanoparticles containing two or more different types of functionalities show unique physical and chemical properties, leading to significantly enhanced performance. In this study, we have developed a new one-pot method to prepare Fe/FeS nanoparticles using dithionite at room temperature. The FeS precipitates on the Fe surface are formed by the interaction between dissolved iron species and hydrogen sulfide, one of the decomposition products of dithionite in solution. The resulting Fe/FeS nanoparticles have high surface area, good electrical conductivity, and strong magnetic responsivity. In addition, the Fe/FeS shows a much higher reactivity toward contaminants than the pure Fe nanoparticles. The above synthesized nanoparticles are successfully applied for the rapid removal of trichloroethylene (TCE) from water. The study reveals that Fe/FeS nanoparticles are a promising candidate for the efficient removal of pollutants.

During the past three decades, gas sensors based either on the surface characteristics or the bulk electrolytic properties of ceramics, have been the subject of extensive research and development. The application of these sensors range from air-to-fuel ratio control in combustion processes such as in automotive engines and industrial furnaces to the detection of leakage of inflammable and toxic gases in domestic and industrial environments. While the solid-state physical sensors, measuring pressure, temperature, and other physical parameters have been commercially successful, less success has been achieved by their chemical analogs, to measure moderate to very low concentrations of gases of importance. These gases include: 02, H2, CO, CO2, NOx, SO=, propane, methane, ethanol, and so on. The semiconductor-based chemical sensors owe their popularity to their small size, simple operation, high sensitivity, and relatively simple associated electronics. However, most of them still suffer from nonselectivity. They also have poor shelf-life and are relatively less stable at higher temperatures. The sensing characteristics and performance of some of the solid-state gas sensors are reviewed in this paper, together with their sensing mechanism, which still is a gray area and has not been fully understood.

The chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) processes are attractive solutions for efficient combustion with direct separation of carbon dioxide. In this work, the feasibility of CuO supported on Al 2 O 3 and MgAl 2 O 4 for CLC and CLOU processes are investigated. The oxygen carriers were produced by freeze-granulation and calcined at 950 and 1050°C. The chemical-looping characteristics were evaluated in a laboratoryscale fluidized bed at 900 and 925°C under alternating reducing and oxidizing conditions. Tendencies towards agglomeration, defluidization and loss of active phase were analyzed by changing the experimental process variables, such as reaction time, temperature and reducing and inert environments. Complete conversion of methane was obtained for all oxygen carriers investigated in this work. Three out of four oxygen carriers also featured the rapid release of oxygen in an inert environment (CLOU). In case of Al 2 O 3 as support, a CLC and a CLOU oxygen carrier were obtained depending on the calcination temperature. In addition, analyses of the CuO-Al 2 O 3 phase equilibria system under oxidizing and reducing conditions has been carried out. At the investigated temperatures, it is inferred for the case of Al 2 O 3 as support that part of the active phase (either CuO or CuAl 2 O 4) is bound as CuAlO 2 during incomplete reduction with slow kinetics for re-oxidation. However, when complete reduction is attained, the original active phase composition is rejuvenated upon oxidation. As a result, the use of CuAl 2 O 4 is suggested for CLC processes from the point of agglomeration and attrition-free functioning of the oxygen carrier. In case of MgAl 2 O 4 as support, the oxygen carrier exhibited a stable oxygen releasing behavior due to the existence of relatively intact CuO. Together with the absence of agglomeration and major morphological changes, the use of MgAl 2 O 4-supported CuO is suggested as a suitable oxygen carrier for CLOU processes.

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