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. 2020 Oct 13;5(42):27492-27501.
doi: 10.1021/acsomega.0c03981. eCollection 2020 Oct 27.

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

Naini Garg  1   2 , Mukesh Kumar  1 , Neelam Kumari  1 , Akash Deep  1   2 , Amit L Sharma  1   2
Affiliations

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

Naini Garg et al. ACS Omega. .

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 m2 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 (NH3) gas. A sensor response of 1.22 ± 0.02 [standard deviation (sd)] is measured for 20 ppm of NH3, while it shows a value of 4.77 ± 0.15 (sd) for 50 ppm of NH3. 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 NH3 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.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
XRD patterns of rGO, ZIF-67, and ZIF-67/rGO. [Inset shows an enlarged view of the (101) peak of rGO in the composite].
Figure 2
Figure 2
N2 adsorption–desorption isotherms for rGO, ZIF-67, and ZIF-67/rGO. [P = equilibrium pressure, P0 = saturate pressure of adsorbate (N2 gas), Va = volume of gas adsorbed].
Figure 3
Figure 3
(a) FT-IR spectra of rGO, ZIF-67, and ZIF-67/rGO; (b) UV–visible (UV–vis) light absorption spectra of ZIF-67 and ZIF-67/rGO.
Figure 4
Figure 4
(a–c) Field-emission SEM micrographs and (d–f) high-resolution TEM images of ZIF-67 and ZIF-67/rGO composite.
Figure 5
Figure 5
(a) EDX and (b) contact angle measurement of the ZIF-67/rGO composite.
Figure 6
Figure 6
(a) Response of a sensor against different NH3 concentrations varying from 20 to 50 ppm at RT; (b) response and recovery time as a function of varying NH3 concentrations (term “gas on” indicates that the valve is opened to allow the diffusion of gas inside the chamber; term “gas off” indicates the opening the lid of the chamber and flushing with fresh air so as to evacuate the residual gas).
Figure 7
Figure 7
Schematic of mechanism of NH3 sensing with the ZIF-67/rGO electrode. (a) Absorption of gas molecules by ZIF-67 and charge transfer across the rGO sheets and (b) energy band diagram.
Figure 8
Figure 8
Comparative response of the ZIF-67/rGO sensor for NH3 and RH. (a) Response with different concentrations of NH3; (b) response of the sensor against humid conditions [(i) 300 and 750 μL water, which are equivalent to the volume of NH3 solution introduced in the chamber to produce 20 and 50 ppm NH3 vapors, respectively; (ii) 55 and 75% RH inside the sensing chamber]. Inset in (b) shows the enlarged portion of the curve marked with a circle. Note that all the experiments were conducted at RT.
Figure 9
Figure 9
Schematic of the ammonia sensing setup.
See this image and copyright information in PMC

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