Abstract
A gas nanosensor is an instrument that converts the information of an unknown gas (species, concentration, etc.) into other signals (for example, an electrical signal) according to certain principles, combining detection principles, material science, and processing technology. As an effective application for detecting a large number of dangerous gases, gas nanosensors have attracted extensive interest. However, their development and application are restricted because of issues such as a low response, poor selectivity, and high operation temperature, etc. To tackle these issues, various measures have been studied and will be introduced in this review, mainly including controlling the nanostructure, doping with 2D nanomaterials, decorating with noble metal nanoparticles, and forming the heterojunction. In every section, recent advances and typical research, as well mechanisms, will also be demonstrated.
Highlights
In our life, we have contact with various harmful and flammable gases, some of which cause air pollution and affect our physical health
Al. [41] prepared zinc oxide (ZnO) microflowers assembled by nanosheets with the modification of Pd nanoparticles, which were applied to fabricate gas sensors exhibiting enhanced selectivity, Li et al [40] synthesized hollow dodecahedrons built by Co O nanosheets via a controllable two step self-templated process
VOCs were tested and the results indicated that the gas sensor could satisfy gas sensors showed a fast response to ethanol gas, including a response time within 25 s and a
Summary
We have contact with various harmful and flammable gases, some of which cause air pollution and affect our physical health. The operation temperature is the temperature at which sensors obtain an optimal response and generally, the response will increase first and decrease with the increasing of the temperature Apart from these parameters, other indices are defined to indicate the gas sensing properties of sensors. Sensors 2019, 19, 1495 time is the period from when aimed gas is injected to when the resistance reaches a stable value in aimed gas; so, recovery time is the period from when aimed gas is removed to when the resistance reaches a stable value in air These parameters determine the application of gas sensors. To tackle the disadvantages of gas sensors, such as their low response, poor selectivity, high operation temperature, and long response/recovery time, approaches to more sensitive material have been studied widely over a long period in the past. As more investigations have continued, it has been found that a regular and ordered nanostructure and morphology, decorating or doping with other materials, and forming a heterojunction could exert additional influences on materials and further improve their gas sensing properties, which will be introduced
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