Nanosized Nb-TiO/sub 2/ gas sensors derived from alkoxides hydrolization

Abstract

Abstract-Nanocrystalline TiO 2 modified with Nb has been produced through the sol-gel technique. Nanopowders have been obtained by means of the hydrolysis of pure alkoxides with deionized water and peptization of the resulting hydrolysate with diluted acid nitric at 100 C. The addition of Nb stabilizes the anatase phase to higher temperatures. XRD spectra of the undoped and the Nb-doped samples show that the undoped sample has been almost totally converted to rutile at 600 C, meanwhile the doped samples present still a low percentage of rutile phase. Nanocrystalline powders stabilized at 600 C with grain sizes of about 17 nm have successfully been synthesized by the addition of Nb with a concentration of 2% at., which appears to be an adequate additive concentration to improve the gas sensor performances, such as it is suggested by the catalytic conversion efficiency experiments performed from FTIR measurements. FTIR absorbance spectra show that catalytic conversion of CO occurs at lower temperatures when niobium is introduced.The electrical response of the films to different concentrations of CO and ethanol has been monitored in dry and wet environments in order to test the influence of humidity in the sensor response. The addition of Nb decreases the working temperature and increases the stability of the layers. Also, large enhancement of the response time is obtained even with lower working temperatures. Moreover, humidity effects on the gas sensor response toward CO and ethanol are less important in Nb-doped samples than in the undoped ones.

Effect of Nb Doping on Chemical Sensing Performance of Two-Dimensional Layered MoSe2

“…We believe that the strong oxidation of the nondoped MoSe 2 device caused the considerable change in its gas sensing response. Addition of Nb along the grain boundaries can meditate defects such as a large number of dangling bonds and vacancies which are more vulnerable to the oxidation . Thus, by doping 2D layered MoSe 2 with Nb, a stable gas response as well as a long-term stability can be achieved.…”

“…Addition of Nb along the grain boundaries can meditate defects such as a large number of dangling bonds and vacancies which are more vulnerable to the oxidation. 34 Thus, by doping 2D layered MoSe 2 with Nb, a stable gas response as well as a long-term stability can be achieved. This approach paves a new path for the realizing high-performance gas sensing devices.…”

Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials

“…Thus, by doping 2D layered MoSe 2 with Nb, a stable gas response as well as a long-term stability can be achieved. 585 However, high Nb doping concentration deteriorated the response to NO 2 which might be attributed to a considerable increase in the number of metallic NbSe 2 regions that did not respond to gas molecules (Figure 24b,c). 586 At relatively low Nb dopant concentrations, MoSe 2 showed enhanced device durability, as well as improved response to NO 2 , attributed to both its small grains and stabilized grain boundaries.…”

“…Addition of Nb along the grain boundaries can meditate a large number of dangling bonds and vacancies which are more vulnerable to the oxidation. Thus, by doping 2D layered MoSe 2 with Nb, a stable gas response as well as a long-term stability can be achieved . However, high Nb doping concentration deteriorated the response to NO 2 which might be attributed to a considerable increase in the number of metallic NbSe 2 regions that did not respond to gas molecules (Figure b,c) .…”

Enhanced ethanol sensing response from nanostructured MoO3:ZnO thin films and their mechanism of sensing

“…31,33 Similar observations have been reported in the case of other metal oxides too. [48][49][50] The recovery process of the sensing layers aer withdrawal of ethanol involves kinetics of desorption of the reaction product from the oxide surface and subsequent adsorption kinetics of oxygen molecules from the atmosphere. The oxygen vacancies in MoO 3 could be replenished by re-oxidation of the oxide surface with gaseous oxygen through the reaction.…”