Development of Zinc Oxide Sensors for Detecting Ammonia Gas in the Ambient Air: A Critical Short Review

Abstract

Ammonia (NH3) is emitted into the atmosphere by various industries and other sources and causes environmental pollution. Considering the hazards of ammonia, detecting leakage from vessels and pipes demands the use of sensors. Therefore, the development of NH3 gas sensors assumes considerable importance to researchers and regulators and to industry, businesses, and facilities that make, store, or use ammonia. The use of metal oxide sensors (MOS) for detecting NH3 gas, such as zinc oxide (ZnO), has been a topic of interest to researchers seeking methods to detect NH3 gas, even at low concentrations. In this article, an attempt has been made to review the research thus far published on the synthesis of ZnO‐based NH3 gas sensor materials, their characterization, and analyses of their performance. Finally, we make several recommendations regarding the scope of future research. For example, the kinetics of the sensor materials shouldbe determined. Furthermore, extensive studies of gas–solid (NH3–ZnO) adsorption are proposed to ascertain the exact adsorption mechanism in terms of isotherm, kinetics, and diffusive mass transport, and to determine “reversibility” and “recovery” of sensor materials so they can continue sensing and activating alarms when necessary for practical applications.

Two-Dimensional Zinc Oxide Nanostructures for Gas Sensor Applications

“…However, it is acutely toxic if inhaled above a moderate quantity as low as 25-35 ppm [82]. Numerous studies have been focused to the use of pure and doped ZnO thin films as NH 3 sensitive materials [83][84][85].…”

Carbon nanotubes-based sensor for ammonia gas detection – an overview

“…The CNTs-based NH 3 gas sensors described by researchers showed a wide range of response times from a few seconds to thousands of seconds. Other factors that positively influence response time are the flow of NH 3 gas, the pressure of the gas, and the gas temperature [55].…”

A Simple Route to Prepare Polypyrrole-Coated Filter Papers via Vapor Phase Polymerization and Their Gas Sensing Application

“…The increasing air pollution in recent years is a major concern for the global environment protection. Various organic and inorganic chemicals used in the industries along with the volatile organic compounds (VOC) are the major sources of air pollution. , Ammonia is a toxic gas having extensive applications in fertilizers, pesticides, petrochemical, textile, and dye industries. − A very low concentration of ammonia can also act as a threat to the human eye, skin, and respiratory systems and also affects the animals and the environment. , The exposure limits of ammonia for 15 min and 8 h exposure times are 35 and 25 ppm, respectively, as reported by the American Conference of Governmental Industrial Hygienists and National Institute for Occupational Safety and Health . Exposure above these limits can cause severe damage to the health of humans, and a very long-time exposure can even cause death.…”

“…6,7 The exposure limits of ammonia for 15 min and 8 h exposure times are 35 and 25 ppm, respectively, as reported by the American Conference of Governmental Industrial Hygienists and National Institute for Occupational Safety and Health. 8 Exposure above these limits can cause severe damage to the health of humans, and a very long-time exposure can even cause death. Therefore, the development of different techniques to detect such pollutants is highly desirable.…”