Room-temperature NO2 Detection Research Articles

Room temperature gas sensor based on rGO/Bi2S3 heterostructures for ultrasensitive and rapid NO2 detection

Bismuth sulfide (Bi2S3) is a promising material for detecting NO2 molecules at room temperature thanks to its narrow and tunable bandgap. However, pure Bi2S3 suffers from some sensing blemish because of its low electroconductivity and poor charge transfer efficiency. Herein, we synthesized the high sensing response room temperature NO2 detection materials composed of Bi2S3 nanoflowers and reduced graphene oxide (rGO). The formed conductive network and heterojunctions between Bi2S3 nanoflowers and rGO nanosheets dramatically improve the conductivity and electron transfer efficiency. The excellent rGO/Bi2S3 sensor shows a high sensing response of 9.8 (approximately two times higher than that of the pure Bi2S3) and rapid response speed of 22 s (almost half of the pure Bi2S3) upon exposure to 1 ppm NO2 at room temperature. Meanwhile, the rGO/Bi2S3 sensor displays superb humidity-independent, selectivity, and stability. These improved NO2 sensing behaviors can be attributed to the heterointerfaces and the hybrid effects, which accelerate charge transfer efficiency between NO2 molecules and the surface of rGO/Bi2S3 heterostructure. To enable on-line detection of ambient hazardous gas, we designed a portable wireless NO2 detector based on rGO/Bi2S3 heterostructure. This study offer an insightful guidance for improving the NO2 sensing behaviors of metal chalcogenides.

Facile preparation of flower-like NiO/In2O3 composite for sensitively and selectively detecting NO2 at room and lower temperatures

As a typical n-type semiconductor, In2O3 is often used in gas sensors due to the wide band gap, adjustable morphology and good electrical conductivity. However, the pristine In2O3 has some disadvantages, such as higher operating temperature, poor sensing performance to low concentrations of gases. In this work, we fabricated flower-like NiO/In2O3 composites via a facile one-pot hydrothermal method, and investigated their gas sensitivity to various concentrations of NO2 at different temperatures. The responses (Rg/Ra) of NiO/In2O3-0.2 composite to 0.1–80 ppm NO2 are 2.5 ∼ 5.8 times higher than those of pristine In2O3 at the optimum temperature of 150 °C, respectively. The room-temperature response of the NiO/In2O3-0.2 composite to 20 ppb NO2 is 1.82 with the limit of detection (LOD) of 5 ppb, indicating great application potential for NO2 detection. Moreover, the NiO/In2O3-0.2 composite has the excellent reproducibility, good long-term stability and selectivity. The specific morphology with larger surface area and the formation of p-n heterojunction synergistically enhance the sensing properties of NiO/In2O3 composite, demonstrated by DFT calculation and experiments. This work provides a facile fabrication of flower-like In2O3–based composites for room-temperature detection of ppb-level NO2.

Detection of NO2 at ppm-level using Al-doped CeO2 based gas sensor with high sensitivity and selectivity at room temperature

Nanostructured metal oxides have gained significant attraction in the field of gas sensors because of their size-dependent, superior catalytic capabilities with better gas adsorption and desorption behaviour. However, their high operating temperature limits their scalability in real-time applications. In this work, we fabricated the pristine and Al-doped CeO2 nanoparticles for Room-Temperature (RT) NO2 detection. Compared to other interfering gases, the fabricated sensor shows a strong preference for detecting NO2, indicating a high level of selectivity. Interestingly 5% Al-doped CeO2 exhibited a remarkable 247% response to 25 ppm of NO2, which is three times greater than the pristine. Furthermore, the sensor exhibits improved response and recovery times of 64 s and 52 s, respectively. It also demonstrates excellent repeatability and stability of 91% over the period of 56 days. Thus, the significant improvement in the sensing performance is attributed to the increase in oxygen vacancies, charge imbalance and enhancement in specific surface area due to the effect of Al doping. Furthermore, these findings will provide a new approach to develop real-time gas sensors for room temperature applications.

Sulfur filling in oxygen vacancy and modulating surface active site on molybdenum-based transition metal oxides/sulfides heterostructure for room-temperature chemiresistive NO2 detection

Constructing distinctive heterogeneous structures and surface site activation represents an effective strategy for enhancing the gas identification capability with reinforced strength. In the previous study, it has been demonstrated that the formation of oxygen vacancies (VO) in heterostructure can significantly enhance metal oxide-based gas sensing. However, developing techniques that effectively modulate VO while simultaneously increasing active sites is a critical yet challenging endeavor. Herein, we designed a hierarchical hollow MoO3 @CoMoO4@CoMoS3.13 heterostructure through post-calcination and vulcanization methods. The results of X-ray adsorption spectroscopy and density functional theory show that the obtained hierarchical heterostructure can significantly accelerate the transport of electrons. Also, the introduction of S atom can modulate VO by tuning the local electronic structure and simultaneously inducing charge compensation at the unsaturated coordination site of cobalt around VO. The reduction of charge density at the exposed Co sites further imparts the heterostructure prominent target gas adsorption properties. Thus, the MoO3@CoMoO4 @CoMoS3.13 sensor exhibits high-efficient NO2 gas sensing performance at room temperature with an impressive response value of 35.42 (50 ppm, S = Ra/Rg), speedy response time of less than 1.1 s, as well as a remarkable long-term stability for at least 60 days.

Highly responsive room-temperature NO2 sensor based on oxygen vacancies-rich SnO2-RGO hybrids

The development of graphene-based room-temperature NO2 sensors with high sensitivity remains a challenge. Herein, a wet-chemical etching strategy is investigated to introduce oxygen vacancies onto SnO2-RGO using ethanolamine (EA) as etching agent, thereby improving the NO2 response of room-temperature NO2 sensors. The oxygen vacancies-rich SnO2-RGO (EA-SnO2-RGO) is simply prepared by stirring SnO2-RGO in EA solution at room temperature, which not only decreases the size of SnO2 particles in EA-SnO2-RGO, but also introduces additional oxygen vacancies onto SnO2 particles surface. Notably, EA-SnO2-RGO sensor presents a high response value of 5.8 (1 ppm NO2) at room temperature, that is 2.1-fold larger than the response value for SnO2-RGO. Simultaneously, EA-SnO2-RGO sensor also demonstrated short response time (95 s) and good selectivity, indicating huge potential applications for room-temperature NO2 detection. This study provides new strategy to fabricate high-performance gas sensors operated at room-temperature.

One-pot hydrothermal synthesis of self-assembled MoS2/WS2 nanoflowers for chemiresistive room-temperature NO2 sensors

Transition metal dichalcogenides (TMDs) based heterostructures are becoming hotspots of gas-sensing applications due to the high electronic mobility, high surface-volume ratio, and abundant adsorption sites. However, the preparation of TMDs-based heterostructures is usually required multiple steps or higher synthesis temperatures (≥ 500 °C). Herein, the flower-like MoS2/WS2 composites were firstly prepared by a facile one-pot hydrothermal method to effectively detect NO2 at room temperature. The WS2 molecules prefer to grow on the edge of as-nucleated MoS2 to form the MoS2/WS2 nanosheets, and then they can grow by layer-by-layer self-assembly to form the MoS2/WS2 heterostructure. The optimized MoS2/WS2 heterostructured composite exhibits the very high sensitivity to NO2 at room temperature, involving high response, good reproducibility, excellent selectivity and long-term stability. Specially, the responses (ΔR/Rg) of MoS2/WS2-0.5 composite to 5 and 100 ppb NO2 are 6.1% and 23.1%, respectively. Moreover, a plausible gas sensing mechanism was proposed from viewpoints of electron transfer and gas adsorption by combining multiple experiments and DFT calculations. This work provides a facile process for synthesis of TMDs-based heterostructures, but also a prospective gas sensing material for room-temperature NO2 detection.

Near-infrared enhanced SnO2/SnSe2 heterostructures for room-temperature NO2 detection: Experiments and DFT calculations

A photo-activated semiconductor gas sensor presents a promising strategy for detecting highly toxic nitrogen dioxide (NO2) gases at room temperature. Near-infrared enhanced gas sensor may offer a new strategy for room-temperature NO2 detection. In this work, MOF-based SnO2/SnSe2 heterostructures prepared by a solvothermal method were used to probe NO2 gas at room temperature. Under near-infrared irradiation, the SnO2/SnSe2 sensor exhibits a response/recovery time of 23/7 s and a sensitivity value of 1500 for NO2 at room temperature. In addition, the adsorption behavior between SnO2/SnSe2 and gas molecules was further studied by first-principles calculations. The optimization of the gas-sensing performance was explored by considering the photoexcited electrons and the heterostructure. This work highlights the potential of SnO2/SnSe2 heterostructures as high-performance NO2 sensors operating at room temperature, as well as the enhanced activation effect of near-infrared irradiation on semiconductor gas sensors.

2D/0D SnSe2/TiO2 nanocomposites for trace NO2 detection under H2S interference at room temperature

Complex gas environments and the demand for room temperature detection will provide challenges for chemo-resistive-type gas sensors in a variety of applications. In this work, 2D/0D SnSe2/TiO2 composite is used as a sensing material, displaying good sensitivity and specificity to ppb-level NO2 at ambient temperature (25 °C). The response value and time of the SnSe2/TiO2 sensor are 207 % and 139s when exposed to 100 ppb NO2, as opposed to 62 % and 183s for the pristine SnSe2 sensor. The composite sensor also offers great long-term stability for NO2 and good gas selectivity. Notably, the SnSe2/TiO2 sensor's mixed gases (NO2+H2S) measurement is done to examine its NO2 detection capacity in the presence of interfering gas. The constructed composite sensor can accurately detect NO2 even if the concentration of the reductive interfering H2S is 66.7 times higher than that of the oxidative target NO2. The effective usage of SnSe2 modified by TiO2 for low-concentration, room-temperature NO2 detection in a complex gas environment is shown by the composite sensor's pleasing gas detection results.

The synergy of Pd nanoparticles and oxygen vacancy to modulate SnO2 modified reduced graphene oxide hybrids for room-temperature ppb-level NO2 detection

Reduced graphene oxides (RGO)-based materials exhibit high carrier mobility and selective recognition ability to NO2, making them constitute promising platform for room-temperature NO2 detection. However, the low sensitivity becomes the main bottleneck for their further development. Here, we demonstrate that synergy of Pd nanoparticles (NPs) and oxygen vacancies can modulate the surface active sites over SnO2 NPs modified RGO hybrids (labeled as SR), leading to improving the sensitivity of room-temperature NO2 sensors. Experimentally, a wet-chemical method was used to introduce oxygen vacancies onto SR, leading to forming SR with rich oxygen vacancies (labeled as SR-Vo), which were subsequently deposited with Pd NPs, resulting in preparing Pd NPs loaded SR-Vo hybrids (labeled as Pd-SR-Vo). Impressively, the response value to 1 ppm NO2 of Pd-SR-Vo hybrids reaches to 9.8, which is much higher than that of R-Vo hybrids (5.6) and SR hybrids (3.3). The improvement of sensitivity toward NO2 for Pd-SR-Vo hybrids is attributed to the synergy effect of Pd NPs and oxygen vacancies, including shortening the band gap of Pd-SR-Vo hybrids with raising conduction band level, widening the width of electron depletion layer between SnO2-Vo and RGO, introducing Schottky contact between Pd and SnO2-Vo, improving efficiency for gas sensing reaction. This work not only provides an efficient approach to fabricate high-performance NO2 sensors, but also opens a new avenue for sensing materials design and modification.

In2O3/g-C3N4/Au ternary heterojunction-integrated surface plasmonic and charge-separated effects for room-temperature ultrasensitive NO2 detection

Light-activated gas sensors based on semiconducting metal oxides (SMOs) hold great promise for next-generation gas sensing application, due to their unique superiority including room-temperature operation, intrinsic safety, and simple device structure. However, poor visible-light absorption and fast carrier recombination of SMOs sensing film are two main barriers that seriously restrict their sensing performance of light-activated gas sensors. Herein, a visible-light activated gas sensor based on Au nanoparticles modified In2O3/g-C3N4 heterojunction nanofibers is developed. Excellent sensing response (Rg/Ra = 17.2 to 1 ppm NO2, where Ra and Rg represent the resistance of sensors when exposed to air or target gas) and fast response/recovery kinetics at room temperature are obtained, which is markedly better than the sensors based on pristine In2O3 nanofibers and In2O3/g-C3N4 nanofibers. Through the discussion and estimation of experimental results, the improved gas sensing properties of In2O3/g-C3N4/Au-based sensors are speculated to be related to the enhanced visible light utilization benefiting from localized surface plasmon resonance (LSPR) effect of Au nanoparticles, and the efficient separation of photo-generated carriers enabled by heterojunctions between In2O3, Au, and g-C3N4 components. The current work will provide a universal strategy to develop high-performance light-activated gas sensor and a deep understanding about the sensing principle of this novel type of gas sensor.

2H-MoS2/Ti3C2Tx MXene composites for enhanced NO2 gas sensing properties at room temperature

Nitrogen dioxide (NO2) is a toxic gas species that poses a great threat to the environment and human health. There are still significant challenges in detecting NO2 gas at room temperature. In this work, 2H-MoS2 nanosheets with controlled morphology were grown on the surface of the few-layer Ti3C2Tx MXene by hydrothermal synthesis and formed unique micro architecture, which aims to complete room temperature detection of NO2. The gas sensors based on the 2H-MoS2/ Ti3C2Tx MXene composites have achieved a high response (65.6%) to 100 ppm NO2 gas at room temperature, which is significantly improved compared with the pure MoS2. The excellent NO2 response and selective properties of 2H-MoS2/Ti3C2Tx MXene composites are attributed to the fast channels for carrier transporting and abundant active sites between 2H-MoS2 and few-layer Ti3C2Tx MXene. The improved sensing performance of the two-dimensional (2D) nanocomposite also provides novel avenues for the modification of other 2D materials and the future development of room temperature gas sensors.

Edge-enriched MoS2 nanosheets modified porous nanosheet-assembled hierarchical In2O3 microflowers for room temperature detection of NO2 with ultrahigh sensitivity and selectivity

Nitrogen dioxide (NO2) is one of the most hazardous toxic pollutants to human health and the environment. However, deficiencies of low sensitivity and poor selectivity at room temperature (RT) restrain the application of NO2 sensors. Herein, the edge-enriched MoS2 nanosheets modified porous nanosheets-assembled three-dimensional (3D) In2O3 microflowers have been synthesized to improve the sensitivity and selectivity of NO2 detection at RT. The results show that the In2O3/MoS2 composite sensor exhibits a response as high as 343.09–5 ppm NO2, which is 309 and 72.5 times higher than the sensors based on the pristine MoS2 and In2O3. The composite sensor also shows short recovery time (37 s), excellent repeatability and long-term stability. Furthermore, the response of the In2O3/MoS2 sensor to NO2 is at least 30 times higher than that of other gases, proving the ultrahigh selectivity of the sensor. The outstanding sensing performance of the In2O3/MoS2 sensor can be attributed to the synergistic effect and abundant active sites originating from the p-n heterojunction, exposed edge structures and the designed 2D/3D hybrid structure. The strategy proposed herein is expected to provide a useful reference for the development of high-performance RT NO2 sensors.

CTAB Enhanced Room-Temperature Detection of NO2 Based on MoS2-Reduced Graphene Oxide Nanohybrid

A new NO2 nanohybrid of a gas sensor (CTAB-MoS2/rGO) was constructed for sensitive room-temperature detection of NO2 by 3D molybdenum disulfide (MoS2) and reduced graphene oxide (rGO), assisted with hexadecyl trimethyl ammonium bromide (CTAB). In comparison with MoS2 and MoS2/rGO, the BET and SEM characterization results depicted the three-dimensional structure of the CTAB-MoS2/rGO nanohybrid, which possessed a larger specific surface area to provide more active reaction sites to boost its gas-sensing performance. Observations of the gas-sensing properties indicated that the CTAB-MoS2/rGO sensor performed a high response of 45.5% for 17.5 ppm NO2, a remarkable selectivity of NO2, an ultra-low detection limit of 26.55 ppb and long-term stability for a 30-day measurement. In addition, the response obtained for the CTAB-MoS2/rGO sensor was about two to four times that obtained for the MoS2/rGO sensor and the MoS2 sensor toward 8 ppm NO2, which correlated with the heterojunction between MoS2 and rGO, and the improvement in surface area and conductivity correlated with the introduction of CTAB and rGO. The excellent performance of the CTAB-MoS2/rGO sensor further suggested the advantage of CTAB in assisting a reliable detection of trace NO2 and an alternative method for highly efficiently detecting NO2 in the environment.

Exploring the possibility of using MWCNTs sheets as an electrode for flexible room temperature NO2 detection

In the last few years, significant progress has been made in nanotechnology, especially in the fabrication of sensors. Generally, metal electrodes are used in devices. Here, carbon nanotubes sheet has been used as an electrode and tin oxide nanoparticles made by the sol-gel method as the sensing material. The combination was used for sensing NO2 in the atmosphere at room temperature. For the MWCNT ​+ ​SnO2 (modified MWCNT) case, there was no immediate recovery for 14 ​ppm gas, and for 28 ppm and 56 ​ppm, recovery times were 13 ​s and 6 ​s, respectively. Using modified MWCNTs sheets as an electrode for flexible devices is the novelty of this work.

Elucidating the Ambient Stability and Gas Sensing Mechanism of Nickel-Decorated Phosphorene for NO2 Detection: A First-Principles Study.

In the field of layered two-dimensional functional materials, black phosphorus has attracted considerable attention in many applications due to its outstanding electrical properties. It has experimentally shown superior chemical sensing performance for the room temperature detection of NO2, highlighting high sensitivity at a ppb level. Unfortunately, pristine black phosphorus demonstrated an unstable functionality due to the fast degradation of the material when exposed to the ambient atmosphere. In the present work, a deepened investigation by density functional theory was carried out to study how nickel decoration of phosphorene can improve the stability of the material. Further, an insight into the sensing mechanism of nickel-loaded phosphorene toward NO2 was given and compared to pristine phosphorene. This first-principles study proved that, by introducing nickel adatoms, the band gap of the material decreases and the positions of the conduction band minimum and the valence band maximum move toward each other, resulting in a drop in the conduction band minimum under the redox potential of O2/O2–, which may result in a more stable material. Studying the adsorption of O2 molecules on pristine phosphorene, we also proved that all oxygen molecules coming from the surrounding atmosphere react with phosphorus atoms in the layer, resulting in the oxidation of the material forming oxidized phosphorus species (POx). Instead, by introducing nickel adatoms, part of the oxygen from the surrounding atmosphere reacts with nickel atoms, resulting in a decrease of the oxidation rate of the material and in subsequent long-term stability of the device. Finally, possible reaction paths for the detection of NO2 are given by charge transfer analyses, occurring at the surface during the adsorption of oxygen molecules and the interaction with the target gas.

MXene modulated SnO2 gas sensor for ultra-responsive room-temperature detection of NO2

Continuous exposure to high concentration of nitrogen dioxide (NO2) severely affects the human respiratory system. Besides, NO2 has been recently observed to foster COVID-19, resulting in increased fatality rate; thus highly selective gas sensors are required for detecting NO2 at sub-ppb level. In this direction, we have synthesized two-dimensional MXene-based tin oxide (SnO2) heterostructures with varying MXene wt% (10–40 wt%) using a facile hydrothermal method for room-temperature NO2 detection. The synthesized heterostructures have been structurally, optically, and electrically characterized using a suite of characterization techniques, namely, X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and Brunauer–Emmett–Teller techniques. The optimal incorporation of MXene in SnO2 nanoparticles effectively decumulates them, increasing the specific surface area of heterostructures and thereby exposing large number of adsorption sites. 20-wt% SnO2/MXene heterostructures-based sensor exhibits nearly five times higher response (231%) toward 30-ppb NO2 at room temperature with shorter response time (146 s) and recovery time (102 s) than pristine SnO2. Moreover, the sensor showed high selectivity, sensitivity, repeatability, reproducibility, and stable sensing response under humid conditions. The assembly of these results suggests that SnO2/MXene platform provides a pathway for realizing highly responsive NO2 sensors. Herein, possible gas sensing mechanism based on the formation of SnO2/MXene heterostructures has been discussed.

Liquid phase exfoliated WS2 nanosheet-based gas sensor for room temperature NO2 detection

Liquid phase exfoliated WS2 nanosheet-based gas sensor for room temperature NO2 detection

High Performance Acoustic Wave Nitrogen Dioxide Sensor with Ultraviolet Activated 3D Porous Architecture of Ag-Decorated Reduced Graphene Oxide and Polypyrrole Aerogel.

Surface acoustic wave (SAW) devices have been widely explored for real-time monitoring of toxic and irritant chemical gases such as nitrogen oxide (NO2), but they often have issues such as a complicated process of the sensing layer, low sensitivity, long response time, irreversibility, and/or requirement of high temperatures to enhance sensitivity. Herein, we report a sensing material design for room-temperature NO2 detection based on a 3D porous architecture of Ag-decorated reduced graphene oxide-polypyrrole hybrid aerogels (rGO-PPy/Ag) and apply UV activation as an effective strategy to further enhance the NO2 sensing performance. The rGO-PPy/Ag-based SAW sensor with the UV activation exhibits high sensitivity (127.68 Hz/ppm), fast response/recovery time (36.7 s/58.5 s), excellent reproducibility and selectivity, and fast recoverability. Its enhancement mechanisms for highly sensitive and selective detection of NO2 are based on a 3D porous architecture, Ag-decorated rGO-PPy, p-p heterojunction in rGO-PPy/Ag, and UV photogenerated carriers generated in the sensing layer. The scientific findings of this work will provide the guidance for future exploration of next-generation acoustic-wave-based gas sensors.

Nickel-Decorated Black Phosphorus for Room Temperature NO2 Detection

Introduction In the rapidly emerging field of layered two-dimensional (2D) functional materials, bP, the all P-counterpart of graphene, is a potential candidate for various applications e.g., nanoscale optoelectronics, rechargeable ion batteries, electrocatalysts, thermoelectrics, solar cells, and sensors [1]. bP has been reported to exhibit superior chemical sensing performance. In particular, bP is selective for the detection of paramagnetic molecules, e.g., NO2, in addition to high sensitivity at a limit of detection (LOD) of ppb levels.[2] In this work, by applying a multiscale characterization approach we demonstrated a stability and functionality improvement of Nickel-decorated bP (Ni/bP) films for gas sensing prepared by a simple, reproducible and affordable deposition technique. Furthermore, we studied pos-sible electrical activity of these films for their employment as functional layers in gas sensors by exposing them to different gaseous compounds (NO2, CO2, H2, NH3, CO, Benzene, etha-nol, ethylene, Formaldehyde) in different relative humidity (RH%) conditions. Moreover, the influence in sensing perfor-mance of nickel nanoparticle (NP) dimensions in related to the decoration technique and the film thickness were investigated. Materials and Methods Black phosphorus microcrystals were suspended in dimethylsulfoxide and kept under ultrasonication for several hours. The exfoliated bP nanosheets were decorated with nickel nanoparticles following two different procedures: 1) preformed Ni NPs were immobilized on bP, 2) Ni NPs were grown directly on bP flakes. Electrical conductance measurements have been performed on Ni/bP flakes deposited via spin coating on Al2O3 substrates with built-in interdigitated gold electrodes, in order to better control the film thickness. Electrical conductance measurements have been performed at RT (25±2°C) by exposing the sensing film to certified mixtures of NO2 diluted in dry air (20% O2 and 80% N2) with different NO2 concentration ranging from 200 ppb to 1 ppm. Results and Conclusions Exfoliated black phosphorus nanoflakes decorated with nickel nanoparticles (Ni/bP) have been prepared and characterized with particular attention to the role of Ni nanoparticle dimension in the sensing mechanism. Electrical activity towards different concentrations of NO2 at room temperature in a dry air environment highlighted fast and stable response over the time. This latter characteristic is particularly relevant since environmental instability of exfoliated BP has been an issue so far, under ambient conditions few-layer bP degrades completely in less than a week, preventing its applications in several fields. In situ grown Ni/bP (2) shows stable response during all the four weeks measurements period with no dependence of the response on the film thickness. Ni decoration effectively suppress ambient degradation, for at least 1 week in Ni/bP (1) and over 4 weeks in Ni/bP (2) in ambient conditions. This result highlighted that Ni/bP (2) sensor can be practically used under ambient conditions for a reasonable period without performance degradation of the devices.The obtained results pave the way for the use of chemically exfoliated bP flakes for gas sensing applications, avoiding the use of a time-consuming technique for the exfoliation and for the fabrication of the metallic contacts, like electron beam lithography, focused ion beam lithography, etc.

Engineering SnO2 nanorods/ethylenediamine-modified graphene heterojunctions with selective adsorption and electronic structure modulation for ultrasensitive room-temperature NO2 detection

Ever-increasing concerns over air quality and the newly emerged internet of things (IoT) for future environmental monitoring are stimulating the development of ultrasensitive room-temperature gas sensors, especially for nitrogen dioxide (NO2), one of the most harmful air pollution species released round-the-clock from power plants and vehicle exhausts. Herein, tin dioxide nanorods/ethylenediamine-modified reduced graphene oxide (SnO2/EDA-rGO) heterojunctions with selective adsorption and electronic structure modulation were engineered for highly sensitive and selective detection of NO2 at room temperature. The modified EDA groups not only enable selective adsorption to significantly enrich NO2 molecules around the interface but also realize a favorable modulation of SnO2/EDA-rGO electronic structure by increasing the Fermi level of rGO, through which the sensing performance of NO2 is synergistically enhanced. The response of the SnO2/EDA-rGO sensor toward 1 ppm NO2 reaches 282%, which exceeds the corresponding SnO2/rGO sensor by a factor of 2.8. It also exhibits a low detection limit down to 100 ppb, enhanced selectivity, and rapid response/recovery kinetics. This approach to designing a novel heterojunction with significantly enhanced chemical and electric effects may shed light on the future engineering of gas-sensing materials.