Abstract
Humidity is a critical environmental parameter for several production processes and its control/monitoring is of great importance in maintaining the quality of goods and products. In this context, metallic oxide ceramic nanostructures are materials of great technological interest in the fabrication of moisture sensors because they have good chemical/structural stability and high surface area/volume ratio. The electrical response of these sensors relates to the chemisorbed and physisorbed layers of water molecules on the surface of the ceramic particles and to the capillary condensation of water in the microscopic pores between the particles. Based on these aspects, this work presents the fundamentals, electrical/electronic properties, influence of dopants, novel preparation procedure by electrospinning and perspectives of application of TiO2:WO3 metal oxide heteronanostructures as humidity sensors.
Highlights
Humidity is a parameter of great importance for the better quality in the production, storage and transport of food, goods and medicines by the industry [1]
This work presents basic concepts that define the class of semiconductor materials and their functional heteronanostructures based on titanium dioxide (TiO2), tungsten trioxide (WO3) and selective dopants produced by electrospinning for potential application as moisture sensors
The change of these parameters promotes changes in the impedance that the semiconductor material experiences when exposed to a certain concentration of humidity, which may qualify it as a relative humidity (RH) sensor
Summary
Humidity is a parameter of great importance for the better quality in the production, storage and transport of food, goods and medicines by the industry [1]. Three conduction regimes can be adopted in these systems: 1) with only a small water coverage of the chemisorbed hydroxyl groups, the hopping conduction of protons is dominant; 2) with a fractional coverage of water (less than one physisorbed layer), diffusion conduction of hydronium in the hydroxyl groups stands out; and 3) when water is abundant, the proton transfer process (Figure 2) is the dominant one In this way, the metal oxide sensors can be treated as semiconductor materials, since the electric conduction occurs through moving electrons and electronic holes (load carriers) from one grain to the overcoming the potential barrier between the grains [7] [8]. This work presents basic concepts that define the class of semiconductor materials and their functional heteronanostructures based on titanium dioxide (TiO2), tungsten trioxide (WO3) and selective dopants produced by electrospinning for potential application as moisture sensors
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