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SM ISO690:2012 CREŢU, Vasilii, POSTICA, Vasile, ABABII, Nicolai, TROFIM, Viorel, RAILEAN, Sergey, LUPAN, Oleg. Gas sensor performances of α-MoO3 belts nanostructured with Pd. In: Health Technology Management: 3rd International Conference, Ed. 3, 6-7 octombrie 2016, Chișinău. Chișinău, Republica Moldova: Technical University of Moldova, 2016, Editia 3, pp. 82-83. |
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Health Technology Management Editia 3, 2016 |
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Conferința "Health Technology Management" 3, Chișinău, Moldova, 6-7 octombrie 2016 | |||||||
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Pag. 82-83 | |||||||
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Molybdenum trioxide (MoO3) due to its unique physical and chemical properties is one of the most attractive candidates for different promising technological applications [1]. -MoO3 has a unique morphology that resembles a structure of layered graphene [2]. Due to the layered structure and high chemical stability MoO3 is used for such applications as gas sensors, recording or storage materials, lubricants, electrochromism, and fotochromism [3]. Meanwhile, MoO3 is a promising material for catalysts [4], the field emission, light emitting diode, and energy storage elements [5], etc., because of its electrical and optical propierties. Nanobelts shaped nanostructures of MoO3 are of major interest due to various gas properties and simple integration technology for bottom-up and the possibility of obtaining cost-effective technologies. Their major drawback is the high surface-to-volume ratio. The increased gas response was obtained by nanostructuration of -MoO3 nanostructure surface with an aqueous solution of PdCl2 presented in our previous work [6]. Figure 1. (a) The SEM images of the nanogranulate belts Pd / α-MoO3 with scale bar of 200 nm; (b) The SEM images of the nanogranulate belts Pd / α-MoO3 after the application of hydrogen gas tests; (c) Gas response measurements to hydrogen gas of nanostructured Pd / α-MoO3. In Figure 1 (a) is provided the surface after the chemical reaction with aqueous PdCl2 solution. The belts surface of α-MoO3 becomes nanostructured by forming nanocrystallites or nanogranulates. Layered morphology of the belts is not modified by reaction with PdCl2 and obvious changes in morphology of α-MoO3 belts was not observed. It was observed that after the reduction with hydrogen in Figure 1 (b), the surface concentration of the Mo6+, decreases greatly by reducing of Mo5+ and the Mo4+. H+ ions interact mainly with oxygen atoms double coordinated from network, leading to the formation of hydrogen molibdenum bronze (HxMoO3) and MoO3 substoichiometric (MoO3-x). Response to H2 gas is calculated using the formula S=((Igaz-Iair)/Iair)*100% thereby obtaining a response of 141% at operating temperature of 150 °C, response time 17 s and the partial recovery time is 9 s. The samples did not demonstrate a full recovery of the signal due to changes in surface morphology. |
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