Rapid, Trace‐Level Ammonia Gas Sensor Based on Surface‐Engineered Ag Nanoclusters@Polyaniline/Multiwalled Carbon Nanotubes and Insights into Their Mechanistic Pathways

Abstract

An ultrasensitive and selective chemiresistive sensor interface based on Ag nanocluster integrated polyaniline functionalized multi-walled carbon nanotubes (AgNC@PANI/MWCNTs) has been developed for trace-level detection of NH 3 gas at room temperature. AgNC@PANI/MWCNTs was synthesized using surfactant-free, one-pot wet-chemical process, by controlled integration of active Ag sites onto MWCNTs. The structure and morphology of AgNC@PANI/MWCNTs nanocomposite have been extensively studied by various characterization techniques. The gas sensing properties of AgNC@PANI/MWCNTs nanocomposite towards trace-level concentrations NH 3 (2-10 ppm), an important biomarker in exhaled human breath, was systematically evaluated. The sensor exhibited dramatic enhancement in the sensor response (26 %), fast response (5 s) and recovery (~4 s) characteristics with good reproducibility and selectivity upon exposure to NH 3 gas. The excellent performance of the sensor towards NH 3 could be attributed to the rapid electronic sensitization of surface engineered active AgNC sites in the composite in which oxidized AgNC were found to play a critical role. Effect of humidity and the kinetics of the NH 3 gas adsorption on nanocomposite were analyzed. The possible interactions between NH 3 and AgNC@PANI/ MWCNTs nanocomposite were discussed. This investigation can pave the way to novel strategies for designing and fabricating low-cost, high performance NH 3 gas sensors for clinical breath analyzer application.[a] S.

Vapor-phase impregnation decomposition technique as an alternativeto decorate MWCNTs withPt and PdNPs for ammonia gas detection

“…It is worthy to mention that the sensors containing Pt/MWCNT are better for the NH 3 detection than these made with Pd/MWCNT because their response time are lower, compare their response time at room temperature in Table 2. According to Abdulla et al [22], the high binding energy (E b ) between the ammonia gas molecules, the defects present on the MWCNTs surface, and the absorbed oxygen could considerably increase the recovery time of the sensor at room temperatures. Furthermore, Van et al [18] found that composites of SnO 2 /MWCNTs increase their sensitivity for the detection of the ammonia gas when high operating temperatures are employed, since this causes the desorption of the gas molecules from the surface of the MWCNTs.…”

“…MWCNTs decorated with Pt-Ag NPs showed up to 5% more sensitivity than the MWCNTs without NPs, which have only 1.5%. Nanoparticles such as Au, Pt [15][16][17] SnO 2 [18], Ag [14,19], Co [20], ITO [21], Ag/ polyaniline [22] Pd [23] and CdS [10] have been also used on MWCNTs, for ammonia gas detection. So far, techniques such as electron beam evaporation, plasma treatment, sputtering coating, precipitation from the metal salt solution, and thermal evaporation have been employed to decorate MWCNTs [15][16][17][18][19][20][21][22][23].…”

“…Nanoparticles such as Au, Pt [15][16][17] SnO 2 [18], Ag [14,19], Co [20], ITO [21], Ag/ polyaniline [22] Pd [23] and CdS [10] have been also used on MWCNTs, for ammonia gas detection. So far, techniques such as electron beam evaporation, plasma treatment, sputtering coating, precipitation from the metal salt solution, and thermal evaporation have been employed to decorate MWCNTs [15][16][17][18][19][20][21][22][23]. Even though interesting efforts have been made to increase sensitivity and selectivity on MWCNTs, it remains a constant need to find better techniques to gain a large response with a lower response and recovery times.…”

Recent Advances in Ammonia Gas Sensors Based on Carbon Nanomaterials

“…The creation of various composites based on MWCNTs, a matrix of conducting polymers (e.g., poly(3,4-ethylenedioxythiophene)–polystyrene sulfonic acid [ 134 ], polyaniline [ 135 , 136 ], polythiothene [ 137 ], etc. ), and metal oxides (TiO 2 [ 138 ], Al 2 O 3 [ 139 ]) made it possible to significantly improve the sensing behavior toward ammonia.…”

Composition of CNT and WO₃ nanoplate: synthesis and NH₃ gas sensing characteristics at low temperature

“…Ammonia (NH3) is a hazardous, colorless gas and is widely used in industry, agriculture, and breeding. In the human breath, NH3 concentration is in the range of 50-2000 ppb and could be used as an indicator of kidney, liver dysfunctions as well as stomach diseases [1]. Nowadays, most of the NH3 gas sensor are conductometric sensors and are based on metal oxide semiconductors such as SnO2, WO3, ... which have high working temperatures (normally higher than 200°C) [2].…”