Synthesis Methods, Microscopy Characterization and Device Integration of Nanoscale Metal Oxide Semiconductors for Gas Sensing

Abstract

A comparison is made between SnO2, ZnO, and TiO2 single-crystal nanowires and SnO2 polycrystalline nanofibers for gas sensing. Both nanostructures possess a one-dimensional morphology. Different synthesis methods are used to produce these materials: thermal evaporation-condensation (TEC), controlled oxidation, and electrospinning. Advantages and limitations of each technique are listed. Practical issues associated with harvesting, purification, and integration of these materials into sensing devices are detailed. For comparison to the nascent form, these sensing materials are surface coated with Pd and Pt nanoparticles. Gas sensing tests, with respect to H2, are conducted at ambient and elevated temperatures. Comparative normalized responses and time constants for the catalyst and noncatalyst systems provide a basis for identification of the superior metal-oxide nanostructure and catalyst combination. With temperature-dependent data, Arrhenius analyses are made to determine activation energies for the catalyst-assisted systems.

Metal-oxide nanostructure and gas-sensing performance

“…Such dissociative chemisorption can be described by a single-step Arrhenius activation energy. In fact, this is consistent with comparative analysis values found for nascent SnO 2 and that with catalyst, the latter having a substantially lower E a , as will be reported elsewhere [21].…”

Controlled Fabrication of Nanostructure Material Based Chemical Sensors

“…The SnO 2 nanorods are produced using a thermal evaporation-condensation (TEC) approach [8]. Tin (IV) oxide is evaporated within a small flow of argon and 5% oxygen in a tube furnace from 700-1000 o C. While in the vapor phase, the oxide self-assembles into coherent rods several micrometers in length along with other geometries.…”

Biological, Chemical, and Electronic Applications of Nanofibers

“…Nanofibers employed for detecting target species of gas molecules in field‐effect transistor (FET) type gas sensors are shown in Figure 7. Metal oxides such as TiO 2 , WO 3 , ZnO, SnO 2 and MoO 3 are widely used for detecting trace concentrations 443, 444. Metal oxide nanofibers made of Molybdenum oxide (MoO 3 ) is used for detecting ammonia 445.…”