In a recent article published in the journal Sensors, researchers presented a comprehensive study on the development of a gas sensor utilizing polyaniline-coated laser-induced graphene (PANI@LIG) for the detection of ammonia (NH3) at room temperature. The research aims to enhance the sensitivity and selectivity of gas sensors, addressing the limitations of existing technologies.
Study: Room-Temperature Ammonia Sensing Using Polyaniline-Coated Laser-Induced Graphene. Image Credit: saoirse2013/Shutterstock.com
Background
Gas sensors have evolved significantly over the years, with various materials being explored for their sensing capabilities. Among these, conductive polymers and carbon-based materials have gained attention due to their unique properties. Laser-induced graphene (LIG) is a promising candidate for gas sensing applications due to its high surface area, porosity, and electrical conductivity.
When combined with polyaniline, a conductive polymer, the resulting composite (PANI@LIG) exhibits enhanced gas sensing performance. Previous studies have indicated that LIG can effectively detect multiple gas species, including nitrogen oxides and volatile organic compounds. However, the specific detection of ammonia using LIG-based sensors has been less explored, highlighting the need for further investigation into this area.
The Current Study
The experimental setup for evaluating the gas sensor's performance involved a series of well-defined procedures. The gas sensing performance was characterized in a controlled humid atmosphere using a Bronkhorst controller evaporator mixer, which was integrated into the gas mixing system. A temperature and humidity sensor (SHT85, SENSIRION) were placed at the chamber outlet to monitor environmental conditions during measurements. The gas sensor was tested against various reducing gases, including carbon monoxide, hydrogen, ethanol, and aromatic volatile organic compounds, as well as nitrogen dioxide as an oxidizing gas.
The materials were characterized using several techniques. Raman spectroscopy was performed with a Renishaw InVia confocal Raman Spectrometer to analyze the molecular structure of the materials. The surface morphology of the PANI@LIG composite was analyzed using a Scios 2 DualBeam field emission scanning electron microscope (FESEM), enabling the capture of high-resolution images of its structural features. Additionally, infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to further characterize the materials.
For the gas sensing experiments, the prepared PANI@LIG sensors were positioned inside a sealed Teflon chamber to prevent exposure to ambient humidity. The chamber was designed to accommodate four sensors, allowing for simultaneous measurements. The electrical resistance of the sensors was measured at a sampling rate of 0.2 Hz with the help of a data acquisition system.
Gas concentrations were delivered into the chamber using a mass-flow controller system, which ensured precise control over the gas flow rates. The sensors were initially stabilized under dry air before being exposed to cyclic concentrations of ammonia, with varying levels from 5 to 100 ppm, to assess their response and recovery times.
Results and Discussion
The results demonstrated that the PANI@LIG gas sensor exhibited significant sensitivity to ammonia, with a clear response observed at concentrations as low as 5 ppm. The sensor's response time was measured at approximately 18.0 minutes, while the recovery time was recorded at 51.0 minutes. These times are considered adequate for real-time monitoring applications, particularly since the concentrations tested were below the short-term exposure limits defined by the European Chemical Agency.
The study also highlighted the importance of the sensor's selectivity. The PANI@LIG composite showed a distinct response to ammonia compared to other gases tested, indicating its potential for specific gas detection. The enhanced performance of the gas sensor can be attributed to the unique structural and morphological characteristics of the PANI@LIG composite. The porous network of LIG, combined with the conductive properties of polyaniline, creates a favorable environment for gas adsorption and interaction, leading to improved sensitivity.
Furthermore, the long-term stability of the gas sensor was evaluated, revealing consistent performance over extended periods. This stability is crucial for practical applications, as it ensures reliable monitoring without frequent recalibration or replacement. The findings suggest that the PANI@LIG gas sensor could be effectively utilized in various settings, including industrial environments, agricultural monitoring, and environmental assessments.
Conclusion
In conclusion, the study successfully demonstrates the development of a novel gas sensor based on polyaniline-coated laser-induced graphene for the detection of ammonia at room temperature. The PANI@LIG composite exhibited significant sensitivity and selectivity, making it a promising candidate for real-time gas sensing applications. The research highlights the potential of combining conductive polymers with advanced carbon-based materials to enhance gas sensor performance.
Future work may focus on optimizing the sensor design and exploring its applicability in diverse environments, further contributing to the advancement of gas sensing technologies. The findings underscore the importance of continued innovation in the field of gas sensors, particularly for monitoring hazardous gases like ammonia, which pose risks to health and the environment.
Journal Reference
Santos-Ceballos J. C., Salehnia F., et al. (2024). Room-Temperature Ammonia Sensing Using Polyaniline-Coated Laser-Induced Graphene. Sensors, 24(23), 7832. DOI: 10.3390/s24237832, https://www.mdpi.com/1424-8220/24/23/7832