Room temperature alcohol sensing by oxygen vacancy controlled TiO2 nanotube array

Abstract

Oxygen vacancy (OV) controlled TiO2 nanotubes, having diameters of 50–70 nm and lengths of 200–250 nm, were synthesized by electrochemical anodization in the mixed electrolyte comprising NH4F and ethylene glycol with selective H2O content. The structural evolution of TiO2 nanoforms has been studied by field emission scanning electron microscopy. Variation in the formation of OVs with the variation of the structure of TiO2 nanoforms has been evaluated by photoluminescence and X-ray photoelectron spectroscopy. The sensor characteristics were correlated to the variation of the amount of induced OVs in the nanotubes. The efficient room temperature sensing achieved by the control of OVs of TiO2 nanotube array has paved the way for developing fast responding alcohol sensor with corresponding response magnitude of 60.2%, 45.3%, and 36.5% towards methanol, ethanol, and 2-propanol, respectively.

Hybrid Fabrication of Highly Rectifying <inline-formula> <tex-math notation="LaTeX">$p$ </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> Homojunction Based on Nanostructured TiO₂

“…The electrolyte was prepared with 0.5 wt% NH 4 F, 25 vol% ethylene glycol (Merck) and 75 vol% of H 2 O. The grown TiO 2 nanotube array was annealed at 300°C for 4 hours in air [4], [6]. Hybrid synthesis of the p-n homojunction device was carried out by using a controlled dip coating technique where the n-TiO 2 nanotube/Ti sample was dipped into the sol prepared for the p-TiO 2 synthesis.…”

Vertical Mode Gas Sensing Performance of TiO2 Nanotube Array by Tuning of Surface Area and Carrier Transport Length

“…MONG the various gas and vapor sensing device structures, viz., resistive [1], homojunction [2], heterojunction [3], Schottky [4], Metal-Insulator-Semiconductor (MIS) [5] and Metal-Insulator-Metal (MIM) [6], the last one (MIM) attracted strong interest owing to the unique advantage of vertical electron (e -) transport in such devices. It has recently been established that employment of 1D nanoforms like nanorods and nanotubes of semiconducting oxide sensing layer is beneficial for extremely fast sensor response due to 1D channel assisted unhindered electron transport between the Manuscript received March10 th , 2015.…”

“…Recently, tuning of gas and vapor sensing performance by judicious tailoring of nanotube properties (structural and electronic) was investigated [1,6]. The variation of stoichiometry and wall separation of the nanotube array and its effect on various targets species has already been reported [1,6,7].…”

TiO2/Pt/TiO2 Sandwich Nanostructures: Towards Alcohol Sensing and UV Irradiation-Assisted Recovery

“…The nanostructured materials, such as nanoparticle, nanowire, nanorod, and nanotube have demonstrated excellent sensing performance compared to conventional thin films [8][9][10][11][12][13][14][15][16][17][18][19][20]. The high selectivity of the sensors has been improved by surface modification with noble metals such as Pt and Pd [21,22].…”

“…In this work, the TiO 2 /Pt/TiO 2 sandwich nanostructures were prepared by sputtering technique and were used as sensing material for ethanol, methanol, and 2-propanol detection in the sensor response results of the TiO 2 /Pt/TiO 2 sandwich nanostructures to the recent researches on ethanol sensing which are mostly based on ZnO, SnO 2 , and TiO 2 with various structures, such as nanoparticle, nanosphere, core-shell, nanotube and thin film, and various doping conditions [12][13][14][15][16][17][18]; it was found that the TiO 2 /Pt/TiO 2 sandwich nanostructures show advantages in terms of 10 ppm level sensitivity, roomtemperature operation, and stability. However, Ag@TiO 2 core-shell nanoparticles show the highest sensitivity down to 0.15 ppm ethanol with a fast response time and a fast recovery time but its fabrication process relies on wet process, which is time-consuming [15].…”