Gas sensing with Nb(V) doped nanocrystalline TiO2: Sensitivity and long-term stability study

Effect of Donor Nb(V) Doping on the Surface Reactivity, Electrical, Optical and Photocatalytic Properties of Nanocrystalline TiO2

“…As the niobium concentration increases, the activation energy decreases monotonically to 0.4 eV for the TiO 2 -Nb-4 material due to the formation of donor levels. In this case, there is no switching from the semiconductor type of conductivity to the metallic one due to the formation of charge traps (oxygen vacancies that localize conduction electrons on themselves), as we established in a previous article reporting our EPR study [20].…”

“…It was found that doping does not affect the band gaps of the phases. The values of two optical transitions with energies of approximately 3.10 eV and 3.33 eV obtained regardless of the analysis method used can be attributed to the band gap of TiO2 phases, As was demonstrated in our previous article [20], during XRD and paramagnetic resonance spectroscopy, Nb(V) doping leads to the formation of substitution-type solid solutions according to the quasi-chemical Equation (1):…”

“…It has been shown that with an increase in Nb content up to 5%, there is a decrease in resistivity from 5850 to 630 µΩcm, an increase in carrier density from 6.5 to 130•10 19 cm −3 as well as a decrease in charge carrier mobility from 16.3 to 7.5 cm 2 V −1 s −1 [19]. An increase in the concentration of surface oxygen vacancies, which are adsorption centers, as well as a quantitative and qualitative change in the content of surface oxygen forms involved in oxidation reactions have also been shown [17,20]. The mechanism of the oxidation reaction of VOCs on the surface of semiconductor oxides was studied using the DRIFTs method [21], and acetone oxidation in particular with pure TiO 2 [22].…”

“…In our previous work [20], it was found that an increase in the Nb(V) concentration leads to an increase in the TiO2 sensor response when detecting the volatile organic…”

“…In our previous work [20], it was found that an increase in the Nb(V) concentration leads to an increase in the TiO 2 sensor response when detecting the volatile organic compounds (VOCs), especially in the case of acetone. To determine the cause of this effect, the processes responsible for the sensor response during the interaction of pure TiO 2 and TiO 2 -Nb4 were investigated in situ using the DRIFT method.…”