Impact of Oxygen Functional Groups on Reduced Graphene Oxide-Based Sensors for Ammonia and Toluene Detection at Room Temperature

Abstract

The chemically reduced graphene oxide (rGO) was prepared by the reduction of graphene oxide by hydrazine hydrate. By varying the reduction time (10 min, 1 h, and 15 h), oxygen functional groups on rGO were tremendously controlled and they were named RG1, RG2, and RG3, respectively. Here, we investigate the impact of oxygen functional groups on the detection of ammonia and toluene at room temperature. Their effect on sensing mechanism was analyzed by first-principles calculation-based density functional theory. The sensing material was fabricated, and the effect of reduction time shown improved the recovery of ammonia and toluene sensing at room temperature. Structural, morphological, and electrical characterizations were performed on both RG1 and RG3. The sensor response toward toluene vapor of 300 ppm was found to vary 4.4, 2.5, and 3.8% for RG1, RG2, and RG3, respectively. Though RG1 shows higher sensing response with poor recovery, RG3 exhibited complete desorption of toluene after the sensing process with response and recovery times of approximately 40 and 75 s, respectively. The complete recovery of toluene molecules on RG3 is due to the generation of new sites after the reduction of oxygen functionalities on its surface. It could be suggested that these sites provided anchor to ammonia and toluene molecules and good recovery under N 2 purge. Both theoretical and experimental studies revealed that tuning the oxygen functional groups on rGO could play a vital role in the detection of volatile organic compounds (VOCs) on rGO sheets and was discussed in detail. This study could provoke knowledge about rGO-based sensor dependency with oxygen functional groups and shed light on effective monitoring of VOCs under ambient conditions for air quality monitoring applications.

Simple Synthesis of Large Graphene Oxide Sheets via Electrochemical Method Coupled with Oxidation Process

“…The reason for this may be the structural dominance of graphene sheets over the disordered areas, which causes lowering of the intensity of D-band. 42−45 For GO batch prepared using Marcano’s approach, the I D / I G ratio was determined as 1.18, which is lower compared to the I D / I G ratio for the GO (6 h) batch.…”

Nanomechanical Gas Sensing with Laser Treated 2D Nanomaterials

“…Defect sites on graphene and graphene oxide act as suitable adsorption sites for various analytes, and it was reported that an increase in the I D /I G ratio generally results in improved gas sensing ability for graphene-based sensors. [20,49,50] The interplanar distance of the stacked GO sheets was determined by X-ray diffraction (XRD) as shown in Figure 4b. The 1.5 h GO has a slightly larger interplanar distance of 0.887 nm compared to 0.845 nm of the 1 h GO.…”

Graphene-based Materials in Gas Sensor Applications: A Review

“…(28) The advantage of rGO over monolayer defect-free graphene is the presence of dangling oxygen functional groups on the graphene surface and edges. (65) Both theoretical and experimental results revealed that tuning of the oxygen functional groups on rGO plays a vital role in the detection of several organic compounds. Experimentally, oxygen functional groups can be tuned by adjusting the reduction time, the type of reducing agent, and the environment of reduction.…”

“…As reported by Minitha et al, the concentration of oxygen functional groups of rGO can be controlled by the aging time during the reduction process with hydrazine hydrate. (65) A higher concentration of oxygen functional groups yields a higher sensing response but poor recovery of the sensor. The sensor has difficulty in recovering its initial state since there are now more anchored functional groups in the graphene sheet, thus the recovery treatment should be several times higher.…”