Copper Phthalocyanine Chemiresistors as Industrial NO<sub>2</sub> Alarms
We present a chemiresistor sensor for NO<sub>2</sub> leaks. The sensor uses the organometallic semiconductor copper(II)phthalocyanine (CuPc), and is more easily manufactured and characterised than previously described organic transistor gas sensors. Resistance R is high but within the ra...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-05-01
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| Series: | Sensors |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1424-8220/25/9/2955 |
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| Summary: | We present a chemiresistor sensor for NO<sub>2</sub> leaks. The sensor uses the organometallic semiconductor copper(II)phthalocyanine (CuPc), and is more easily manufactured and characterised than previously described organic transistor gas sensors. Resistance R is high but within the range of modern voltage buffers. The chemiresistor weakly responds to several gases, with either a small increase (NH<sub>3</sub> and H<sub>2</sub>S) or decrease (SO<sub>2</sub>) in R. However, the response is low at environmental pollution levels. The response to NO<sub>2</sub> also is near-zero for permitted long-term exposure. Our sensor is, therefore, not suited for environmental monitoring, but acceptable environmental pollutant levels do not interfere with the sensor. Above a threshold of ~87 ppb, the response to NO<sub>2</sub> becomes very strong. This response is presumably due to the doping of CuPc by the strongly oxidising NO<sub>2</sub>, and is far stronger than for previously reported CuPc chemiresistors. We relate this to differences in the film morphology. Under 1 ppm NO<sub>2</sub>, R drops by a factor of 870 vs. non-polluted air. An amount of 1 ppm NO<sub>2</sub> is far above the ‘background’ environmental pollution, thereby avoiding false alarms, but far below immediately life-threatening levels, thus giving time to evacuate. Our sensor is destined for leak detection in the nitrogen fertiliser industry, where NO<sub>2</sub> is an important intermediate. |
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| ISSN: | 1424-8220 |