Pd/TiO2 nanosheet/Ti sensor towards propanol sensing: Influence of edge energy and defect states

Frequency-tuned selectivity enhancement of Mg@ZnO–TiO2 nanoflake-based heterojunction sensor devices

“…A comparison of 2-butanone, acetone, 2-propanol, ethanol, and methanol sensing by various materials in capacitive structures is provided in Table 1. Chowdhury et al 3 prepared TiO 2 nanosheets for 2-propanol sensing in the capacitive mode, and revealed the optimum capacitive change was at 0.5 kHz and at 150 °C. Homayoonnia et al 12 developed a capacitive sensor based on CuBTC nanoparticles for detecting methanol at room temperature.…”

“…By accepting electrons out of the conduction band of ZnO–TiO 2 , the oxygen molecules that have been adsorbed on its surface are changed into single or double ionized species following eqn (6)–(9). 3 The reaction and transformation of O 2 to different species (O 2 − , O − , O 2− ) mainly depends on the operating temperature. Below 100 °C, the molecular form O 2 − was found to be dominant, and above 100 °C and below 300 °C, oxygen was chemically adsorbed in the ionic form O − ; while above 300 °C, it was chemically ionized in O 2− .…”

“…1,2 The inhalation of air containing alcohol (methanol, ethanol, 2-propanol) can affect human health and may cause headache, stomach pain, nausea, eye irritation, drowsiness, dizziness, etc . 1–3,5 Acetone can also result in fire when it is mixed in air at a level as low as 2.5%–12.8% at a temperature more than its flash point of −20 °C. 2 The exposure of high concentration of n -butanol to eye can cause blurred vision and photophobia.…”

“…The bandgap energy of anatase TiO 2 is 3.2 eV. 3,6 The two main drawbacks of TiO 2 are its (i) wide bandgap ( E g ) and (ii) the fast recombination of electron–hole pairs, which can be eliminated by various strategies, including suitable doping with metals or non-metals. 7 In this regard, the present study selected Mg doping and ZnO nanoflakes on a TiO 2 thin film for the suitable fabrication of a Mg@ZnO–TiO 2 heterojunction.…”

“…The porous form of ZnO nanoflakes facilitates the easy diffusion of vapour molecules at ZnO–TiO 2 heterojunction interfaces, resulting in effective dielectric changes in the device. 3 In the present study, the dielectric change and hence capacitance in the presence and absence of VOCs were taken into consideration to measure the sensor parameters. The capacitive change was recorded in vertical mode (metal–insulator–metal) device configuration considering ZnO nanoflakes and TiO 2 thin film as the dielectric medium between the two electrodes.…”