Development of gas sensors using ZnO nanostructures

Abstract

Different ZnO nanostructures such as nanowires, nanobelts and tetrapods have been grown and used for preparation of thick film (with random grain boundaries) as well as isolated nanowire/nanobelt gas sensors. Sensitivity of different type of sensors has been studied to H 2 S and NO gases. The results show that the response of ZnO sensors to H 2 S arises from grain boundary only whereas both grain boundaries and intragrain resistances contribute towards response to NO. In addition, oxygen vacancies in the lattice were also seen to help in improvement of sensor response. Room temperature operating H 2 S and NO sensors based on ZnO nanowires have been demonstrated. Further, sensors based on isolated nanobelts were found to be highly selective in their response to NO.

Electrophoretic fabrication of ZnO/ZnO-CuO composite for ammonia gas sensing

“…Consequently, the resistivity of the suspension increases which is manifested by the apparent decrease in the deposition current. This observation is consistent to some reported studies that a high ionic concentration will cause instability of the suspension thereby inhibiting the movement of ceramic particles 24,25 .The stability of the suspension in EPD dictates the success and quality of the material formation in the substrate. Qualitative investigation of the deposits implies that the suspension current is proportional to the deposition yield.…”

“…The more open the structure and the smaller the particles are, the larger the surface area will be available for gas molecules to react with to significantly change the bulk charge concentration. Since NH 3 is a reducing gas, it is expected that when gas molecules penetrate an n-type material such as ZnO, they attach themselves to the vacant lattice holes which in effect increases the conductivity of the material 25 . This widely accepted theory in gas sensing mechanism is validated in this experiment.…”

ZnO Tetrapods: Synthesis and Applications in Solar Cells

“…ZnO has wide-ranging applications in electronic and optoelectronic devices, such as piezoelectric sensors, ultraviolet (UV)/blue light-emitting diodes, transistors, field emission displays, gas sensors, UV detectors, transparent conductive films, hybrid solar cells, etc. ZnO is also inexpensive, relatively abundant, chemically stable, easy to prepare, and nontoxic [1,2] In addition, ZnO is amenable to processing into variegated morphologies in terms of nanostructure synthesis, owing to its hexagonal wurtzeit (WZ) crystal structure and different growth rates of the diverse crystal planes. To date, a variety of morphologies have been achieved, including nanopowders, nanobelts, nanobows, nanodiscs, nanoplatelets, nanoflowers, nanowires, nanotetrapods and nanorods [3][4][5].…”

Recent developments on nano-ZnO catalyzed synthesis of bioactive heterocycles

“…Among these, ZnO-nanoparticles were used in various areas, such as optoelectronics [32,33], ferromagnetism [34], piezoelectric transducers [35], solar cell [36], gas sensors [37], etc. [38].…”