NO2 Gas Sensor Research Articles

A Cone-Like TSV Structured ZnO NO2 Gas Sensor that is Produced Using Room-Temperature Laser Drilling and Radio-Frequency Sputtering

Abstract A typical through-silicon via (TSV) has vertical and high aspect ratio holes, making special equipment required to deposit the film on the vertical hole walls. This study used room-temperature laser drilling to fabricate a cone-like TSV structure so that no special process equipment was required. Radio-frequency sputtering was used to deposit SiNx, ITO, and ZnO films on the cone-like TSV structure to form a ZnO NO2 gas sensor. Scanning electron microscopy and focused ion beam results show that the ZnO film connects the front and back sides of the substrate, enabling sensing on both sides. If the concentration of NO2 gas is increased, the sensor response increases and the average sensor response is 34,7%, with an inaccuracy of <± 1% for five 5 consecutive measurements using a NO2 concentration of 3ppm. Reactions with NH3, CO, CO2, and SO2 gases are almost insignificant, giving the cone-like TSV structure ZnO gas sensor good selectivity, stability, and reproducibility for NO2 gas.

Engineering an Ultrafast Ambient NO2 Gas Sensor Using Cotton-Modified LaFeO3/MXene Composites.

This work presents a room-temperature (RT) NO2 gas sensor based on cotton-modified LaFeO3 (CLFO) combined with MXene. LaFeO3 (LFO), CLFO, and CLFO/MXene composites were synthesized via a hydrothermal method. The fabricated sensor, utilizing MXene/CLFO, exhibits a p-type behavior and fully recoverable sensing capabilities for low concentrations of NO2, achieving a higher response of 14.2 times at 5 ppm. The sensor demonstrates excellent performance with a response time of 2.7 s and a recovery time of 6.2 s, along with notable stability. The sensor's sensitivity is attributed to gas interactions on the material's surface, adsorption energy, and charge-transfer mechanisms. Techniques such as in situ FTIR (Fourier transform infrared) spectroscopy, GC-MS (gas chromatography-mass spectroscopy), and near-ambient pressure X-ray photoelectron spectroscopy were employed to verify gas interactions and their byproducts. Additionally, finite-difference time-domain simulations were used to model the electromagnetic field distribution and provide insight into the interaction between NO2 molecules and the sensor surface at the nanoscale. A prototype wireless IoT (Internet of Things)-based NO2 gas leakage detection system was also developed, showcasing the sensor's practical application. This study offers valuable insight into the development of room-temperature NO2 sensors with a low detection limit.

Study the Structural and Optical Properties (Energy Gap) of Polythiophene/MWCNT/SnO2 Nanocomposite as an NO2 Gas Sensor

The polythiophene (PTh) is of great interest in various applications due to its unique electrical, mechanical and structural. In this work, PTh was synthesized using the oxidation method by employing ferric chloride (FeCl3) as an oxidizing agent, Then the nanocomposite polythiophene: Multi walled carbon nanotubes: Tin (IV) oxide (PTh/MWCNT/SnO2) was prepared by adding constant weight ratio of MWCNT(0.7g) and different weight ratios of SnO2 (0.1, and 0.5g) using the oxidation method. The FE-SEM images of the pure PTh and the nanocomposite showed an apparent change in the morphological composition of the surface. The X-ray diffraction (XRD) pattern of PTh/ MWCNT/SnO2 nanocomposites show the appearance of clear peaks for SnO2, while there are broad peaks for MWCNT. As for the polymer, its behavior is random. The morphology of these nanocomposites shows that the nanotubes were not well aligned and were randomly entangled. The Fourier transformer infrared (FT-IR) spectra of the pure and nanocomposite samples prepared by chemical method in the range of 450-4000 cm-1 wave number are recognized the chemical pledges (bonds) as well as functional groups in the compound. The band gap energy decreased from 3.53 into 2.78 and 2.97 when SnO2 was added. The sensitivity of the two nanocomposites shows a good enhancement 14.6% and 62% at temperature 150oC as gas sensor.

Surface Modification and Decoration of Nano-Honeycombed ZnO Structure With Gold-Black Nanoparticles for High Responsivity Detection of NO₂ Gas Sensors

Surface Modification and Decoration of Nano-Honeycombed ZnO Structure With Gold-Black Nanoparticles for High Responsivity Detection of NO₂ Gas Sensors

Study of the Sensitivity of Carbon Quantum Dots for NO2 Gas Sensor and improve it using Graphene

Gas sensors are essential for detecting noxious gases that have a detrimental effect on people's health and welfare. Carbon quantum dots (CQDs) are the fundamental component of gas detectors. CQDs and graphene (Gr) were prepared using the electrochemical method. The gas sensitivity of these materials was evaluated at different temperatures (150, 200, 250 °C) to assess their effectiveness. Subsequently, experiments were conducted at different temperatures to ascertain that the combination of CQDs and Gr, with various percentages of Gr and CQDs, exhibited superior gas sensitization properties compared to CQDs alone. This was evaluated based on criteria such as sensitivity, recovery time, and reaction time. Interestingly, the combination was highly responsive. The quantum dots on glass substrates could detect NO2 gas at the abovementioned temperatures. Experimental evidence showed that the gas sensor can only detect graphene at low temperatures.

MoS2-xSex lamellae assembled with lotus-leaf-like structures for sensitive NO2 gas sensors at room temperature

MoS2-xSex lamellae assembled with lotus-leaf-like structures for sensitive NO2 gas sensors at room temperature

Highly responsive gas sensors based on grain boundary–rich polycrystalline few-layer MoS2 films for NO2 detection

Abstract This study addresses the issues of insufficient sensitivity and poor reversibility for NO2 detection by successfully fabricating a sensor based on uniform and high-quality few-layer MoS2 polycrystalline material using chemical vapor deposition. This approach aims to improve the response of the sensor by exploiting the abundance of grain boundary (GB) defects in polycrystalline MoS2 membranes. Comprehensive surface morphology analysis of the few-layer MoS2 polycrystalline films was conducted using microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy to characterize their chemical composition and properties. Subsequently, evaluation of 1–100-ppm NO2 was conducted at room temperature (25 °C). The results show excellent performance of the sensor, with a response range of 11–82.24. Notably, under ultraviolet excitation at room temperature, this sensor exhibits a response time of only 41 s to 50 ppm of NO2 with complete recovery and improved sensitivity, maintaining reliable stability over eight weeks. Furthermore, the findings reveal that the sensor demonstrates high selectivity toward NO2 gas with limit of detection and limit of qualification values of 10 and 34 ppb, respectively. Owing to the abundant adsorption sites provided by GB defects in polycrystalline thin films, the response performance of the sensor is effectively enhanced. This study provides valuable insights into the future design and development of high-performance NO2 gas sensors.

Highly Sensitive and Selective Room Temperature NO2 Gas Sensor Based on 3D BiFeO3 − x Microflowers

Highly Sensitive and Selective Room Temperature NO2 Gas Sensor Based on 3D BiFeO3 − x Microflowers

Development and Performance of ZnO/MoS2 Gas Sensors for NO2 Monitoring and Protection in Library Environments

The presence of harmful oxidizing gases accelerates the oxidation of cellulose fibers in paper, resulting in reduced strength and fading ink. Therefore, the development of highly sensitive NO2 gas sensors for monitoring and protecting books holds significant practical value. In this manuscript, ZnO/MoS2 composites were synthesized using sodium molybdate and thiourea as raw materials through a hydrothermal method. The morphology and microstructure were characterized by X-ray diffraction analysis (XRD), energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The ZnO/MoS2 composite exhibited a flower-like structure, with ZnO nanoparticles uniformly attached to the surface of MoS2, demonstrating advantages such as high specific surface area and good uniformity. The gas sensitivity of the ZnO/MoS2 nanocomposites reached its peak at 260 °C, with a sensitivity value around 3.5, which represents an improvement compared to pure ZnO, while also enhancing sensitivity. The resistance of the ZnO/MoS2 gas sensor remained relatively stable in air, exhibiting short response times during transitions between air and NO2 environments while consistently returning to a stable state. In addition to increasing adsorption capacity and improving light utilization efficiency, the formation of hetero-junctions at the ZnO-MoS2 interface creates an internal electric field that effectively promotes the rapid separation of photo-generated charge carriers within ZnO, thereby extending carrier lifetime.

Carborazine doped nanographene (CBNG) sheet as a promising NO2 gas sensor: A theoretician’s approach

Nanographenes (NGs) are a distinct section of graphene in which the dangling bonds are saturated with hydrogen atoms (C42H18). This confinement in size results in unique properties and potential applications. The density functional theory (DFT) is used to investigate the reactivity and electronic sensitivity of a model carborazine (B2C2N2) ring doped nanographene (CBNG) for detecting NO2 gas. In CBNG/NO2 complex, one oxygen atom of the NO2 molecule is positioned at a distance of 2.93Ả from the center of the B2C2N2 ring, with an adsorption energy −6.2 kcal/mol. The adsorption energy of NO2 on CBNG is apparently larger than those of other gas molecules, which fall between the suitable range of strong physical adsorption and weak chemical adsorption. Upon NO2 adsorption, the band gap of CBNG sheet reaches 62.4 %. The outcome of the present study may be exploited in the industry, particularly in the synthesis of effective NO2 gas sensors.

A room-temperature NO2 gas sensor based on Zn2+ doped Cu2O/CuO composites with ultra-high response

Metal oxide semiconductors (MOS) have attracted increasing interest in gas sensors recently due to their exceptional design flexibility and superior gas sensing capabilities. However, the high operating temperatures and reliance on light activation in MOS-based gas sensors limit their potential applications. In this work, the Zn2+ doped Cu2O/CuO composites were successfully fabricated by one-step hydrothermal method for the detection of NO2 gas at room temperature. The experimental results show that the optimal Zn-Cu2O/CuO composite presents responses that are 2.9, 3.4, 3.1 times higher than those of the pure Cu2O/CuO composite to 10, 5 and 1 ppm NO2. Additionally, the response and recovery times are shortened by factors of 3.1 and 1.4, respectively. Notably, the detection limit of the Zn-Cu2O/CuO composite is 2 ppb at room temperature, significantly below China's annual average NO2 concentration limit of ∼18 ppm. Furthermore, the Zn-Cu2O/CuO based sensor demonstrates the great selectivity, repeatability and long-term stability for NO2 detection. The gas sensitivity enhancement mechanism is thoroughly discussed. This result provides a new approach for the effective detection of ppb-level NO2 by CuO-based gas sensing materials at room temperature.

Flexible and highly selective NO2 gas sensor based on direct-ink-writing of eco-friendly graphene oxide for smart wearable application

Nitrogen dioxide (NO2) is a major cause of respiratory disorders in outdoor and indoor environments. Real-time NO2 monitoring using nonintrusive wearable devices can save lives and provide valuable health data. This study reports a room-temperature, wearable, and flexible smart NO2 gas sensor fabricated via cost-effective printing technology on a polyimide substrate. The sensor uses alkali lignin with edge-oxidised graphene oxide (EGO-AL) ink, demonstrating a sensitivity of 1.70% ppm⁻1 and a detection limit of 12.70 ppb, with excellent selectivity towards NO2. The high sensing properties are attributed to labile oxygen functional groups from GO and alkali lignin, offering abundant interacting sites for NO2 adsorption and electron transfer. The sensor fully recovers to the baseline after heat treatment at 150 °C, indicating its reusability. Integration into lab coats showcased its wearable application, utilising a flexible printed circuit board to wirelessly alert the wearer via cell phone to harmful NO2 levels (>3 ppm) in the environment. This smart sensing application underscores the potential for practical, real-time air quality monitoring, personal safety enhancement, and health management.

Insights into the Effects of Co-doping on the Electronic Properties of Armchair Graphene Nanoribbon-based NO2 Gas Sensors

Insights into the Effects of Co-doping on the Electronic Properties of Armchair Graphene Nanoribbon-based NO2 Gas Sensors

Synthesis and Characterization of TiO2 Nanotubes for High-Performance Gas Sensor Applications

In this study, we investigated the fabrication, properties, and sensing applications of TiO2 nanotubes. A pure titanium metal sheet was used to demonstrate how titanium dioxide nanotubes can be used for gas-sensing applications through the electrochemical anodization method. Subsequently, X-ray diffraction indicated the crystallization of the titanium dioxide layer. Scanning electron microscopy and transmission electron microscopy then revealed the average diameter of the TiO2 nanotubes to be approximately 100 nm, with tube lengths ranging between 3 and 9 µm and the thickness of the nanotube walls being about 25 nm. This type of TiO2 nanotube was found to be suitable for NO2 gas sensor applications. With an oxidation time of 15 min, its detection of NO2 gas showed a good result at 250 °C, especially when exposed to a NO2 gas flow of 100 ppm, where a maximum NO2 gas response of 96% was obtained. The NO2 sensors based on the TiO2 nanotube arrays all exhibited a high level of stability, good reproducibility, and high sensitivity.

Enhanced NO2 Gas Sensing in Nanocrystalline MoS2 via Swift Heavy Ion Irradiation: An Experimental and DFT Study.

Nanostructured transition metal dichalcogenides (TMDs) like MoS2 hold promise for gas sensing applications due to their exceptional properties. However, limitations exist in maximizing sensor performance, such as limited active sites for gas interaction and sluggish response/recovery times. This study explores swift heavy ion (SHI) irradiation as a strategy to address these challenges in MoS2-based NO2 gas sensors. MoS2 nanoflakes were fabricated and subsequently irradiated with 120 MeV silver (Ag) ions to induce structural and morphological modifications. Characterization techniques confirmed the formation of Mo and S vacancies within the MoS2 lattice due to irradiation. Significantly, SHI irradiation resulted in a remarkable enhancement of approximately 3 times improvement in sensing response compared to pristine MoS2 sensors. Additionally, the irradiated sensors exhibit substantial improvements in both response and recovery times for NO2 detection. SHI irradiation resulted in the formation of self-affine nanostructures and increased grain fragmentation as fluence rises. This enhanced surface area is hypothesized to promote gas-sensor response. To gain deeper insights into the underlying mechanism, first-principles calculations were employed. These calculations suggest that electron transfer occurs from the MoS2 surface to the NO2 molecule during interaction. Furthermore, the irradiation-induced vacancies facilitate stronger NO2 adsorption on the MoS2 surface compared to the pristine sample. This work demonstrates the effectiveness of SHI irradiation in engineering defects within MoS2 nanoflakes, leading to significantly improved NO2 gas-sensing performance. This approach offers a promising avenue for developing next-generation TMD-based gas sensors with enhanced sensitivity, response times, and stability.

Theoretical insights of 2D Fe3GeTe2/In2Se3 multiferroic vdW heterostructure based gas sensors for high-performance NO detecting

The impact of the harmful gas NO on the atmospheric environment cannot be ignored, so it is necessary to develop efficient gas sensors to detect and absorb NO at room temperature. In this work, we systematically explored the electron transport properties and gas sensing properties of Fe3GeTe2, In2Se3 monolayers and its multiferroic van der Waals (vdW) heterostructures of Fe3GeTe2/In2Se3 for detecting NO by using density functional theory and nonequilibrium Green's function methods. The calculated adsorption energies, electron localisation functions, band structures and density of states indicate that its a chemisorption for the adsorption of NO on Fe3GeTe2 and a physisorption on In2Se3, while the specific adsorption style is highly dependent on the stacking and molecular adsorption sites of different Fe3GeTe2/In2Se3 structures. In addition, the pristine Fe3GeTe2 monolayer and Fe3GeTe2/In2Se3 based nanodevices realized a significant anisotropy for electron transport along the zigzag and armchair directions, and their anisotropic maximum current ratios in the zigzag to armchair directions were 1.90 and 1.89. Meanwhile, the NO sensitivity ratio of Fe3GeTe2 and Fe3GeTe2/In2Se3 based gas sensors can be up to 79 % and 107 %, respectively. This highlights a notably superior gas-sensitive performance of the Fe3GeTe2/In2Se3 heterostructure compared to the Fe3GeTe2 monolayer gas devices. These findings provide valuable references for the application of multiferroic heterostructures in the field of gas sensors.

Spectroscopic, structural characterization, along with DFT calculation, of a new cadmium(II) acetato meso-arylporphyrin: Theoretical study on NO2, CO2, N2, NO2, and SO2 gas-sensing and analysis of electrical conductance and dielectric properties

The paper presents a combined experimental and computational investigation of the cadmium(II) (acetato)‑meso-tetra(para-methoxyphenyl)porphyrin ion complex [Cd(TMPP)(OAc)]- (complex 1), which was prepared by the reaction of [Cd(TMPP)] with an excess of NaOAc and crysptand-222 in chloroform. This new Cd(II) meso‑arylporphyrin was characterized by elementary analysis and UV–Vis, IR, and 1H NMR spectroscopic techniques along with single crystal X-ray diffraction. This later study shows that the Cd2+center ion adopts a distorted square pyramidal geometry and is coordinated by the four nitrogens of the TMPP porphyrinate and the oxygen atom of the acetato axial ligand. The intermolecular interactions in the crystal lattice of [Cd(TMPP)(OAc)]-, determined using the PLATON program and Hirshfeld surfaces analysis, are of types O__H…O, C__H…H, C__H…Cl, C__H…Cg and C__Cl…Cg (Cg is the centroid of a phenyl or a pyrrole ring) involving the [Cd(TMPP)(OAc)]- ion complex, the [Na(crypt-222)]+ counterion, and the chloroform and water molecules found in the crystal lattice of complex 1. Using DFT calculations at the DFT/B3LYP-D3/lanL2DZ level of theory HOMO–LUMO orbitals of 1 and several global reactive parameters of this compound were calculated. The 3D-MEP plots of [Cd(TMPP)(OAc)]- were also determined. This theoretical study includes the sensing properties of complex 1 and the NO2, CO2, N2, and SO2 gas molecules. Furthermore, experimental tests have been carried out concerning the impedance and dielectric spectroscopy of the InGa/[Cd(TMPP)(OAc)]/InGa device.

N-n type In2O3@-WO3 heterojunction nanowires: enhanced NO2 gas sensing characteristics for environmental monitoring.

Solvothermal synthesis of 1D n-In2O3@n-WO3 heterojunction nanowires (HNWs) and their NO2 gas sensing characteristics arereported. The n-In2O3@n-WO3 HNWs have been well-characterised using XRD, Raman spectroscopy, XPS, SEM and HRTEManalyses. The NO2 sensing performance of n-In2O3@n-WO3 HNWs showed superior performance compared withpristine WO3 NWs. Due to the distinctive configuration of WO3-In2O3 heterojunctions, the n-In2O3@n-WO3 HNWs demonstrated remarkable sensitivity reaching 182% in response towards 500ppb of NO2 gas at operating temperature of 200°Cwhich is nearly 3.5 times greater than the response observed with pristine WO3 (50%). Moreover, the n-In2O3@n-WO3 HNWs also exhibited fast response (8-13s)/recovery (54-62s) time characteristics. A plausible sensing mechanism has been discussed. The enhancement in sensor characteristics shows that n-In2O3@n-WO3 HNWs could serve as a promising material for high-performance NO2 gas sensors for real-time environmentalmonitoringapplications. This work could provide new understandings of the sensing mechanism of n-In2O3@n-WO3-based heterojunction nanowires, which can be applied to the design of novel n-n type MOS heterojunction materials for the application of low-temperature real-time high-performance NO2 sensors.

Humidity-independent NO2 gas sensors based on ZnO-NiOFx nanocomposites and the synergistic humidity-immune effect of fluorine doped NiO

Clean, alternative energy sources, especially fuel cells, are gradually attracting global attentions while the produced toxic nitrogen dioxide (NO2) is a greatly hazardous chemical impacting their energy efficiencies. Metal oxide semiconductors (MOS) hold significant promise as NO2 sensors. However, intensive humidity interaction intensifies signal drifts and reliable response inhibitions under variable humidity conditions. In this study, we present a novel approach to address this issue by engineering in-situ F-doped NiO nanocomposites (NiOFx) decorated on ZnO snowflakes achieved through decomposition modulation of ZnOHF precursors. The optimized NO2 sensor demonstrates unparalleled humidity-independence across a wide operating temperature range with prime sensitivity, low detection limit and rapid response/recovery. Matrix algorithm is also implemented in highly precise NO2 identification under complicated atmospheric and humid conditions. Mechanism studies based on temperature programmed desorption (TPD), quasi in-situ X-ray photoelectron spectroscopy (Quasi in-situ XPS) reveal that F− dopants facilitate interfacial electron transferring and inhibit oxygen activity. In-situ diffuse reflectance infrared Fourier transform spectroscopy (In-situ DRIFTS) demonstrates that hygroscopic NiO and electronegative F− synergistically obstruct hydroxyl adsorptions on sensing materials. The innovative approach offers a promising solution for enhancing moisture resistance of MOS sensors for real-time NO2 concentration monitoring in fuel cells and provides valuable insights into anti-humidity mechanisms.

TiO2@ZrO2 p-n heterostructured nanocomposites for enhanced NO2 gas sensing

Hydrothermal approach was used to synthesize pure TiO2, ZrO2 and 2.5–10 % TiO2-ZrO2 p-n type nanocomposite heterojunctions. Morphological and structural features of heterostructures were established by XRD, TEM/HRTEM and SEM investigations. Band gap energy calculations revealed a reduction in band structure from 4.96 eV of pure ZrO2 to 3.50 eV of 7.5 % TiO2-ZrO2 heterostructures. BET surface area characterization displayed large surface area of the nanocomposites which performed an essential part in the enhanced sensing activity of the nanocomposite heterostructures. 7.5 % TiO2-ZrO2 sensor exhibited enhanced response to NO2 gas possessing excellent response and recovery times. The maximum sensitivity of 991 was shown by 7.5 % TiO2-ZrO2 sensor to 100 ppm NO2 gas that was nearly four folds compared to pristine ZrO2 nanospheres (263). The improved NO2 gas sensing of the nanocomposites was stemmed to the construction of p-n heterostructures that resulted in the emancipation of more reactive sites and thus led to the better sensing result of the nanocomposites. The gas sensing mechanism and improved sensing characteristics have been also elaborated. The strategy thus suggested in this report may offer considerably to the understanding of more sensitive NO2 gas sensors.