NH3 Sensor Based on ZIF-8/CNT Operating at Room Temperature with Immunity to Humidity

Humidity effects on resistive gas sensors operating at room temperature remain a serious bottleneck. In this work, we introduce a resistive gas sensor based on a zeolitic imidazolate framework-8/carbon nanotube (ZIF-8/CNT) composite for the detection of ammonia gas at room temperature. The composite was prepared using a facile solution method. In this sensor, the basic mechanism was the charge transfer between ammonia molecules and CNTs; meanwhile, the ZIF-8 facilitated the adsorption of ammonia molecules as a preconcentrator, and prevented the adsorption of H2O molecules due to its hydrophobicity; CNTs were threaded through the ZIF-8 to form a great conductive network for charge transfer. The obtained sensor showed good ammonia sensing, especially at room temperature, with great selectivity and immunity to humidity under moderately humid conditions (45–70 % RH). However, the ammonia response was reduced at very high humidity (90% RH) due to the competitive adsorption of H2O molecules. This proved that the NH3 sensor based on ZIF-8/CNT could be suitable for practical applications under moderately humid conditions.