Chemoresistive Room-Temperature Sensing of Ammonia Using Zeolite Imidazole Framework and Reduced Graphene Oxide (ZIF-67/rGO) Composite

Abstract

The present work demonstrates the application of a composite of the zeolite imidazole framework (ZIF-67) and reduced graphene oxide (rGO), synthesized via a simple hydrothermal route for the sensitive sensing of ammonia. The successful synthesis of ZIF-67 and rGO composite was confirmed with structural and spectroscopic characterizations. A porous structure and a high surface area (1080 m 2 g –1 ) of the composite indicate its suitability as a gas sensing material. The composite material was coated as a thin film onto interdigitated gold electrodes. The sensor displays a change in its chemoresistive property (i.e., resistance) in the presence of ammonia (NH 3 ) gas. A sensor response of 1.22 ± 0.02 [standard deviation (sd)] is measured for 20 ppm of NH 3 , while it shows a value of 4.77 ± 0.15 (sd) for 50 ppm of NH 3 . The fabricated sensor is reproducible and offers a stable response, while also providing tolerance against humidity and some other volatile compounds. The average response and recovery times of the sensor, for 50 ppm NH 3 concentration, are found to be 46.5 ± 2.12 (sd) and 66.5 ± 2.12 (sd) s, respectively. The limit of detection of the sensor was found to be 74 ppb.

Borate Anion Dopant Inducing Oxygen Vacancies over Co3O4 Nanocages for Enhanced Oxygen Evolution

“…The peak at 1580 cm −1 can be associated with the stretching vibration of the C=N bond in 2-methylimidazole ligand [52]. Moreover, the peak at 2929 cm −1 and 3134 cm −1 are caused by the C-H stretching vibration of the aromatic ring and the aliphatic methyl group in 2-methylimidazole, respectively [47]. The above results demonstrate the successful synthesis of the ZIF-67 precursor.…”

“…Careful observation demonstrates the appearance of the diffraction peak assigned to the (511) crystal plane of Co FT-IR spectra were also performed to investigate the surface functional groups and the skeleton changes of the resultant catalysts [46]. For ZIF-67 precursor, there is the apparent stretching vibration at 425 cm −1 related to the characteristic peak of Co-N (Figure S10), which confirms the bonding between the cobalt atom and the N atom in the 2-methylimidazole linker in ZIF-67 [47]. The peaks in the region of 600-1500 cm −1 contribute to the bending and stretching modes of the imidazole ring in ZIF-67 [48].…”

“…In addition, UV-Vis absorption spectra were also carried out by dispersing the resultant catalysts into ethanol with a constant concentration in the range of 400 to 700 nm. As displayed in Figure S12, the ZIF-67 precursor has characteristic transitions of tetrahedral Co 2+ at 539 nm and 596 nm, respectively [47]. Moreover, the characteristic transition peak can be well-retained after reaction with different boron sources and potassium hydroxide, and the intensity of the B-Co 3 O 4 -2@ZIF-67 peak is much lower than that of the ZIF-67 precursor, indicating that there remain ZIF-67 residues in the resultant B-Co 3 O 4 -2@ZIF-67, which is consistent with the above mentioned FESEM and TEM analysis results.…”

Ultra-Sensitive Bimetallic Alloy Loaded with Porous Architecture MOF for Ammonia Detection at Room Temperature

“…Therefore, it is necessary to detect ammonia accurately and rapidly. Compared with other detection approaches for ammonia, such as chromatography [6], spectrophotometry [7], chemiluminescence [8] and capillary electrophoresis [9], chemical methods have gain much interest due to their low cost, high sensitivity and simple operation [10].…”

“…Recently, chemical sensors for detection of hazardous gases were successfully synthesized using some porous crystalline materials [10,11]. Amongst them, metal organic frameworks (MOFs), a new class of porous crystalline networks, have received remarkable attention [12,15].…”