N-Doped Graphene Quantum Dot-Decorated Three-Dimensional Ordered Macroporous In₂O₃ for NO₂ Sensing at Low Temperatures

Abstract

Nitrogen dioxide (NO2) detection is of great importance because the emission of NO2 gas profoundly endangers the natural environment and human health. However, a few challenges, including lowering detection limit, improving response/recovery kinetics, and reducing working temperature, should be further addressed before practical applications. Herein, a series of N-doped graphene quantum dot (N-GQD)-modified three-dimensional ordered macroporous (3DOM) In2O3 composites are constructed and their NO2 response properties are studied. The results show that compared to pure 3DOM In2O3, reduced graphene oxide (rGO)/3DOM In2O3, and N-doped graphene sheets (NS)/3DOM In2O3, the N-GQDs/3DOM In2O3 sensing materials exhibit higher NO2 responses with fast response and recovery speed and low working temperature (100 °C). In addition, the detection limit of NO2 response for the optimal N-GQDs/In2O3 sensor is as low as 100 ppb. Upon exposure to CO, CH4, NH3, acetone, ethanol, toluene, and formaldehyde, only very weak responses could be observed, indicating good selectivity for the synthesized material. More attractively, the responses of the optimized N-GQDs/In2O3 sensor exhibit no obviously big fluctuation over 60 days, implying good long-term stability. We suggest that the formation of heterojunctions between 3DOM In2O3 and N-GQDs and the doping N atoms in N-GQDs play crucial roles in improving the NO2 sensing properties.

Indium Oxide Based Nanomaterials: Fabrication Strategies, Properties, Applications, Challenges and Future Prospect

“…In the hydrothermal method, water is generally taken as solvent whereas organic solvent instead of water is used in solvothermal method. In these methods, aqueous solutions of metal nitrates, chlorides and acetates are generally used as precursor materials for the synthesis of metal oxides [8,10]. In this method, the precursor materials and solvents are taken in a particular stoichiometric ratio and stirred for a particular time period to obtain a homogeneous solution.…”

“…It is noteworthy that these materials are suitable for different applications such as photovoltaic devices, liquid crystal displays, transparent conductive electrode in electronic devices, solar cells and flat panel displays, photodetectors, gas sensors, heat reflecting windows etc. [2,8,10]. On the other hand, different nanostructured IO based bulk nanomaterials such as nanosheets, nanowires, nanoparticles, quantum dots, single crystals are found to have potential applications [8,[11][12][13].…”

“…In this regard, Wang et al [18] reported hierarchically structured ZnO decorated with IO nanoparticles synthesized by one-pot sol-gel process towards improvement in n-butanol sensing performance. Moreover, N-doped graphene quantum dots modified three-dimensional ordered macroporous IO based nanocomposites had been fabricated for NO 2 gas sensing application [10]. On the other hand, IO based nanomaterials are largely used for microelectronics and optoelectronic applications [2,7,19] and also found in significantly improved stability of solar cells without negotiating the performance of IO/ZnO electron transporting bilayer, synthesized by solution-process as reported by Kirmani et al [20].…”

Resistive-Based Gas Sensors Using Quantum Dots: A Review

“…A N-GQDs-modified, 3D-ordered macroporous In 2 O 3 composite was fabricated for NO 2 sensing applications [102]. The sensor showed an improved response relative to the pristine In 2 O 3 gas sensor at 100 • C. The generation of N-GQDs/In 2 O 3 heterojunctions was a major contributor to the sensing signal.…”

Chemical and Electronic Modulation via Atomic Layer Deposition of NiO on Porous In2O3 Films to Boost NO2 Detection

“…NO 2 , mainly released from industrial production and automobile exhaust emissions, is one of the most harmful gases in environment. In atmosphere, it will form nitric acid aerosol, which is the main source of acid rain and photochemical smog. , In addition, NO 2 is seriously harmful to human health; continued exposure to even ultra-low concentrations will lead to an increase in the incidence of respiratory diseases. − According to the National Institute of Occupational Safety and Health of the United States, the exposure threshold of NO 2 is 1 ppm . Therefore, fast and accurate NO 2 sensors with low concentration capabilities are highly required to for the sake of environmental protection and human health …”