Abstract
The development of a highly sensitive gas sensor for toxic gases is an important issue in that it can reduce the damage caused by unexpected gas leaks. In this regard, in order to make the sensor accurate and highly responsive, we have investigated which morphology is effective to improve the sensitivity and how the deposited nanoparticle affects the sensitivity by controlling the morphology of semiconductor oxides—either nanorod or nanoplate—and depositing metal nanoparticles on the semiconductor surface. In this study, we compared the CO gas sensitivity for sensors with different morphology (rod and plate) of ZnO nanostructure with metal nanoparticles (gold and copper) photodeposited and investigated the correlation between the gas sensitivity and some factors such as the morphology of ZnO and the properties of the deposited metal. Among the samples, Au/ZnO nanorod showed the best response (~86%) to the exposure of 100 ppm CO gas at 200 °C. The result showed that the electrical properties due to the deposition of metal species also have a strong influence on the sensor properties such as sensor response, working temperature, the response and recovery time, etc., together with the morphology of ZnO.
Highlights
Carbon monoxide (CO) is a dangerous byproduct derived from the incomplete combustion of petroleum-based fuels
A considerable study has been reported about the synthesis and application of the CO gas sensor in the form of ZnO nanostructures, p-type semiconductor/ZnO, metal-deposited ZnO composites, etc
There have been few comparative studies relating to the effect of the morphology of ZnO on CO gas sensitivity [7,8]
Summary
Carbon monoxide (CO) is a dangerous byproduct derived from the incomplete combustion of petroleum-based fuels. According to the WHO reports, it has been reported that humans die within an hour when exposed to 800 ppm of carbon dioxide, and the recommended safety level is 30 ppm to exposure of CO for an hour [2] These standards call for an accurate and rapidly responsive sensor for CO gas. In this work, considering practical application, we wanted to find other metal of high electrical conductivity and stability with the price competitiveness to alternate noble metals. In this aspect, altogether with Au nanoparticle, Cu one was chosen as one of the candidate materials. The correlation between CO gas sensitivity and some possible factors, such as morphology of semiconductor, electrical properties, intrinsic properties of metal, and surface characteristics, was discussed
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