Stoichiometry, Length, and Wall Thickness Optimization of TiO₂ Nanotube Array for Efficient Alcohol Sensing

Abstract

The present study concerns development of an efficient alcohol sensor by controlling the stoichiometry, length, and wall thickness of electrochemically grown TiO2 nanotube array for its use as the sensing layer. Judicious variation of H2O content (0, 2, 10 and 100% by volume) in the mixed electrolyte comprising ethylene glycol and NH4F resulted into the desired variation of stoichiometry. The sensor study was performed within the temperature range of 27 to 250 °C for detecting the alcohols in the concentration range of 10-1000 ppm. The nanotubes grown with the electrolyte containing 2 vol % H2O offered the maximum response magnitude. For this stoichiometry, variation of corresponding length (1.25-2.4 μm) and wall thickness (19.8-9 nm) of the nanotubes was achieved by varying the anodization time (4-16 h) and temperatures (42-87 °C), respectively. While the variation of length influenced the sensing parameters insignificantly, the best response magnitude was achieved for ∼13 nm wall thickness. The underlying sensing mechanism was correlated with the experimental findings on the basis of structural parameters of the nanotubes.

Metal Chelation Assisted In Situ Migration and Functionalization of Catalysts on Peapod-Like Hollow SnO2toward a Superior Chemical Sensor

“…In the case of the 1D SnO 2 NTs, it is formed by oxidation of residue Sn in CNFs, not Sn spheres. When the residual Sn precursors in CNFs form the 1D tube structures driven by Ostwald ripening, the suitable amount of Sn precursors in CNFs is an important parameter for stable formation of tubular structures. The lack of Sn precursors in CNFs could not manufacture the clear 1D nanotubular structures (Figure S6, Supporting Information).…”

“…We also clearly confirm that the radius of exterior SnO 2 spheres is larger than that of interior SnO 2 spheres. The wall thickness of hollow spheres and nanotubes is under ≈20 nm, which can play an effective role in gas detection layers through the sensitive change of thickness of electron depletion layers . The selected area electron diffraction (SAED) pattern analysis using TEM clearly shows the presence of rutile SnO 2 crystallites and Pt catalysts (Figure c).…”

Highly sensitive NO2 sensors based on core‐shell array of silicon nanowires/polypyrrole and new insight into gas sensing mechanism of organic/inorganic hetero‐contact

“…Jae-Hun et al ever reported that the CuO-ZnO C-S nanowires sensor showed the highest response to CO and C 6 H 6 at a shell thickness close to Debye length (λ D ) of ZnO [32]; while according to the investigation from Park et al, the critical thickness for the shell in In 2 O 3 -ZnO C-S nanowires sensor was very close to 2λ D of ZnO [33]. The sensing mechanism of these metal oxide C-S structures has been demonstrated with several models such as the potential barrier-controlled carrier transport and the radial modulation effect in the electrondepleted shell [34][35][36][37][38]. For LNWs/PPy C-S nanowires sensors in this work, different correlation between gas response and shell thickness is revealed.…”

Improving Hydrogen Sensing Performance of TiO2 Nanotube Arrays by ZnO Modification

“…The relatively high sensitivity of pristine TiO 2 toward H 2 can be attributed to the unique hierarchical morphology of the nanotubes. The small half-tube-wall thickness is comparable to that of the space charge layer, which favors hydrogen adsorption and its reaction with surface oxygen (Paulose et al, 2005;Hazra et al, 2015). The improved H 2 response of TiO 2 @ZnO may be a result of the synergistic contribution from two effects.…”