Plasma-Polymerized Thiophene-Reduced Graphene Oxide Composite Film Sensor for Ammonia/Amine Detection at Room Temperature

Abstract

Industrialization has led to an increasing need for specific and selective gas sensors in the past few decades. Environmental monitoring of certain volatile compounds such as ammonia is necessary. Advancements in the food storage sector have created the need for cheap and effective amine chemosensors. Classical chemosensors still face several issues, such as a lack of selectivity and low sensitivity toward ammonia and amines. Sensitivity is defined as the relative change in response expressed in percentage. In this work, we have resolved a few issues associated with the ammonia and amine sensors, such as low selectivity, long-term instability, and unreliability under higher temperatures using plasma-polymerized thiophene (PPTh) reduced graphene oxide (rGO) composite films. PPTh films were prepared using RF plasma polymerization with optimized deposition parameters. Several samples were evaluated for their sensing response to understand the optimal PPTh and rGO ratio in the PPTh-rGO composite. These composite PPTh-rGO films have shown 4 times higher sensitivity for ammonia/amines than individual PPTh and rGO films. Ammonia, methylamine (MA), dimethylamine (DMA), and trimethylamine (TMA) were primary analytes and tested for sensing response of the PPTh-rGO composite. The sensitivity measured ranges from 1328 for trimethylamine to 2354 for methylamine at 1000 ppm. The order of sensitivity was found to be MA > Ammonia > DMA > TMA. Polymer swelling, reduced charge carriers, and disruption of conductive pathways can explain possible sensing mechanisms. PPTh-rGO composite films have shown selectivity as high as 110 for ammonia/amine over other commonly used volatile organic compounds. The sensing response of these films is stable for any temperature fluctuations from 30 °C to 150 °C. Additionally, films showed stable sensitivity for over 4 months. Thus, composite films of PPTh-rGO can be effectively used to develop highly selective and stable gas sensors for the environmental monitoring of ammonia/amines.

Methylamine Gas Sensor Based on Fluorescent Perovskite Nanocrystal Nanofibers Incorporating Aggregation-Induced Emission Materials

“…Detecting low concentrations of MA is also crucial for assessing fish freshness during cold chain transportation. − Given these applications, the development of sensors capable of effectively detecting MA is particularly critical. Among optical sensors, fluorescent sensors exhibit attractively advantageous characteristics compared to electrical sensors, which rely on conductive polymers, − metal–organic framework nanomaterials, − and chromatographic techniques. , These characteristics include ease of detection, nondestructive testing capabilities, resistance to electromagnetic interference, operational compatibility at room temperature, and reduced energy consumption. However, in previous research, materials proposed for fluorescent gas sensing often exhibit several shortcomings, including weak signals, high detection limits, and instability. − …”

Achieving Molecular-Level Selective Detection of Volatile Organic Compounds through a Strong Coupling Effect of Ultrathin Nanosheets and Au Nanoparticles

“…The activation energy required for the reaction of formaldehyde is lower than that of other VOCs on the MOS surface . Accordingly, some studies succeeded to design the sensors that could exclusively detect formaldehyde by reducing the optimal working temperature of the chemiresistive sensor. , For example, noble metal modification and carbon-based materials of the MOS surface, the construction of organic conductive polymer gas sensors, and transition metal vulcanization modification and photoactivation can significantly reduce the operating temperature of MOS sensors. − Particularly, introducing precious metals, such as Pt, Au, Pd, etc., on the semiconductor surfaces has been typically applied to decrease the optimal working temperature due to a strong metal–support interaction. − As an example, the catalyst effect and unfilled 4d-orbital of Au can significantly alter the surface properties and adsorption-activation ability of MOS-based sensors . Therefore, maximizing efficiency by coupling ultrathin nanosheets with Au nanoparticles is crucial for sensor applications.…”