Fast detection of NO2 by porous SnO2 nanotoast sensor at low temperature

Self-assembled peptide nanotubes (SPNTs)/SnO2nanocomposites for high-performance NO2sensing at room temperature

Nitrogen dioxide (NO2) is a major pollutant that poses significant risks to sustainable human life. As a result, a growing focus has been placed on the development of highly selective and sensitive gas sensors for NO2. Traditional cutting-edge non-organic NO2gas detectors often necessitate stringent production conditions and potentially harmful materials, which are not environmentally friendly, and these shortcomings have limited their widespread practical use. To overcome these challenges, we synthesized self-assembled peptide nanotubes (SPNTs) through a molecular self-assembly process. The SPNTs were then combined with SnO2in varying proportions to construct NO2gas sensors. The design of this sensor ensured efficient electron transfer and leverage the extensive surface area of the SPNTs for enhanced gas adsorption and the effective dispersion of SnO2nanoparticles. Notably, the performance of the sensor, including its sensitivity, response time, and recovery rate, along with a lower detection threshold, could be finely tuned by varying the SPNTs content. This approach illustrated the potential of bioinspired methodologies, using peptide self-assemblies, to develop integrated sensors for pollutant detection, providing a significant development in environmentally conscious sensor technology.

MOF-derived xPd-NPs@ZnO porous nanocomposites for ultrasensitive ppb-level gas detection with photoexcitation: Design, diverse-scenario characterization, and mechanism

Metal-organic frameworks (MOFs) have been regarded as a potential candidate with great application prospects in the field of gas sensing. Although plenty of previous efforts have been made to improve the sensitivity of MOF-based nanocomposites, it is still a great challenge to realize ultrafast and high selectivity to typical flammable gases in a wide range. Herein, porous xPd-NPs@ZnO were prepared by optimized heat treatment, which maintained the controllable morphology and high specific surface area of 471.08 m2g-1. The coupling effects of photoexcitation and thermal excitation on the gas-sensing properties of nanocomposites were systematically studied. An ultrafast high response of 88.37 % towards 200 ppm H2 was realized within 1.2 s by 5.0Pd-NPs@ZnO under UV photoexcitation. All xPd-NPs@ZnO exhibited favorable linearity over an extremely wide range (0.2-4000 ppm H2) of experimental tests, indicating the great potential in quantitative detection. The photoexcited carriers enabled the nanocomposites a considerable response at lower operating temperatures, which made diverse applications of the sensors. The mechanisms of high sensing performances and the photoexcitation enhancement were systematically explained by DFT calculations. This work provides a solid experimental foundation and theoretical basis for the design of controllable porous materials and novel photoexcited gas detection.

Synergy of Active Sites and Charge Transfer in Branched WO3/W18O49 Heterostructures for Enhanced NO2 Sensing

Achieving reliable detection of trace levels of NO2 gas is essential for environmental monitoring and protection of human health protection. Herein, a thin-film gas sensor based on branched WO3/W18O49 heterostructures was fabricated. The optimized WO3/W18O49 sensor exhibited outstanding NO2 sensing properties with an ultrahigh response value (1038) and low detection limit (10 ppb) at 50 °C. Such excellent sensing performance could be ascribed to the synergistic effect of accelerated charge transfer and increased active sites, which is confirmed by electrochemical impedance spectroscopy and temperature-programmed desorption characterization. The sensor exhibited an excellent detection ability to NO2 under different air quality conditions. This work provides an effective strategy for constructing WO3/W18O49 heterostructures for developing NO2 gas sensors with an excellent sensing performance.

Overall perspective of electrospun semiconductor metal oxides as high-performance gas sensor materials for NOx detection

Gas sensors based on nanostructured semiconductor metal oxide (SMO) materials have been extensively investigated as key components due to their advantages over other materials, namely, high sensitivity, stability, affordability, rapid response and simplicity. However, the difficulty of working at high temperatures, response in lower concentration and their selectivity are huge challenges of SMO materials for detecting gases. Therefore, researchers have not stopped their quest to develop new gas sensors based on SMOs with higher performance. This paper begins by highlighting the importance of nitrogen monoxide (NO) and nitrogen dioxide (NO2) detection for human health and addresses the challenges associated with existing methods in effectively detecting them. Subsequently, the mechanism of SMO gas sensors, analysis of their structure and fabrication techniques focusing on electrospinning technique, as well as their advantages, difficulties, and structural design challenges are discussed. Research on enhancing the sensing performance through tuning the fabrication parameters are summarized as well. Finally, the problems and potential of SMO based gas sensors to detect NOx are revealed, and the future possibilities are stated.

Size-Dependent Response of Hydrothermally Grown SnO2 for a High-Performance NO2 Sensor and the Impact of Oxygen

A NO2 sensor with a detection limit down to the ppb level based on pristine SnO2 has been developed through a facile poly(acrylic acid)-mediated hydrothermal method. SnO2 particles of solid microsphere, hollow microsphere, and nanosphere morphologies were synthesized, with respective constitutional crystallite of size ∼2 μm in length and 10-20 nm and ∼7 nm in diameter. All sensors show great selectivity to NO2. The hollow microsphere sensor exhibits the best performance, with medium specific surface area (SSA), followed by the nanosphere sensor with the largest SSA. This is attributed to the superposition of two opposite effects on sensor response with increased SSA: more adsorption sites and fewer electrons to be taken out with overly small crystallite that may reach complete depletion. O2 is found to speed up the response and recovery times but reduce the response because O adsorbates facilitate the adsorption/desorption of NO2 thermodynamically, and the two oxidizing gases compete in harvesting electrons from SnO2. The adverse effect of humidity can be minimized by operating the sensor at 110 °C. The response of the hollow microsphere sensor to 50 ppb of NO2 is 8.8 (Rg/Ra) at room temperature, and it increases to 15.1 at 110 °C. These findings are useful for developing other oxidizing gas semiconductor sensors.

Oxidation-enabled SnS conversion to two-dimensional porous SnO2 flakes towards NO2 gas sensing

Tin dioxide (SnO2)-based electronic materials and gas sensors have attracted extensive attention from academia and industry. Herein we report the preparation of two-dimensional (2D) porous SnO2 flakes by thermal oxidation of 2D SnS flakes that serve as a self-sacrificial template. An oxidation-enabled, temperature-dependent matter conversion from SnS through three-phase SnS-SnS2-SnO2 (400 °C) and two-phase SnS2-SnO2 (600 °C) to pure-phase SnO2 (≥800 °C) is disclosed by means of combined XRD, TG-DSC and XPS studies. Meanwhile, the associated chemical reactions and the mass and heat changes during this solid-state conversion process are clarified. The as-prepared 2D SnO2 flakes exhibit structural porosity with tunable pore sizes and crystallite sizes/crystallinity, resulting in superior potential for NO2 sensing. At the optimized operating temperature of 200 °C, the prototype gas sensors made of porous SnO2 flakes show competitive sensing parameters in a broad NO2 concentration range of 50 ppb-10 ppm in terms of high response, faster response/recovery speeds, and good selectivity and stability. A sensing mechanism involving the adsorption and desorption of NO2/O2 molecules and the possible surface reactions is further rationalized for the SnO2 NO2 gas sensors.

Sodium titanate: A proton conduction material for ppb-level NO2 detection with near-zero power consumption

Constrained by the traditional charge transfer sensing mechanism, it is quite challenging to fabricate NO2 sensors that simultaneously exhibit high sensitivity, rapid response/recovery, and low power consumption. Herein, sodium titanate (NTO), a layered material with abundant surface-rooted OH groups (OHR), is demonstrated to be a promising NO2 sensing material. To understand the sensing behavior of NTO, the influences of operating temperature, applied voltage, and relative humidity are investigated, and a novel OHR-enabled proton conduction sensing mechanism is proposed. The sensing process mainly involves selective NO2 adsorption on OHR, thereby lowering the activation energy for proton transportation along the NTO surface. Meanwhile, the moderate intermolecular interaction makes NO2 both easily adsorbed and desorbed at room temperature. Hence, NTO exhibits a highly sensitive, rapid, and fully recoverable response (∼5.7-1 ppm NO2 within 3 s), wide detection range (1 ppb-20 ppm), good stability (>2 months), and near-zero power consumption (0.5 nW). Finally, we demonstrate that NTO has an excellent practical indoor/outdoor NO2 sensing ability. This work offers a new pathway to resolve the inherent conflicts in available NO2 sensors by using NTO via the OHR-enabled proton conduction sensing mechanism, which may also provide insight into designing high-performance sensors for other gases.

Synergistic Effect of Electron Scattering and Space Charge Transfer Enabled Unprecedented Room Temperature NO2 Sensing Response of SnO2

Metal oxide gas sensors have long faced the challenge of low response and poor selectivity, especially at room temperature (RT). Herein, a synergistic effect of electron scattering and space charge transfer is proposed to comprehensively improve gas sensing performance of n-type metal oxides toward oxidizing NO2 (electron acceptor) at RT. To this end, the porous SnO2 nanoparticles (NPs) assembled from grains of about 4 nm with rich oxygen vacancies are developed through an acetylacetone-assisted solvent evaporation approach combined with precise N2 and air calcinations. The results show that the as-fabricated porous SnO2 NPs sensor exhibits an unprecedented NO2 -sensing performance, including outstanding response (Rg /Ra  = 772.33 @ 5 ppm), fast recovery (<2 s), an extremely low detection limit (10 ppb), and exceptional selectivity (response ratio >30) at RT. Theoretical calculation and experimental tests confirm that the excellent NO2 sensing performance is mainly attributed to the unique synergistic effect of electron scattering and space charge transfer. This work proposes a useful strategy for developing high-performance RT NO2 sensors using metal oxides, and provides an in-depth understanding for the basic characteristics of the synergistic effect on gas sensing, paving the way for efficient and low power consumption gas detection at RT.

Conductometric Gas Sensor Based on MoO3 Nanoribbon Modified with rGO Nanosheets for Ethylenediamine Detection at Room Temperature

An ethylenediamine (EDA) gas sensor based on a composite of MoO3 nanoribbon and reduced graphene oxide (rGO) was fabricated in this work. MoO3 nanoribbon/rGO composites were synthesized using a hydrothermal process. The crystal structure, morphology, and elemental composition of MoO3/rGO were analyzed via XRD, FT-IR, Raman, TEM, SEM, XPS, and EPR characterization. The response value of MoO3/rGO to 100 ppm ethylenediamine was 843.7 at room temperature, 1.9 times higher than that of MoO3 nanoribbons. The MoO3/rGO sensor has a low detection limit (LOD) of 0.235 ppm, short response time (8 s), good selectivity, and long-term stability. The improved gas-sensitive performance of MoO3/rGO composites is mainly due to the excellent electron transport properties of graphene, the generation of heterojunctions, the higher content of oxygen vacancies, and the large specific surface area in the composites. This study presents a new approach to efficiently and selectively detect ethylenediamine vapor with low power.

In-situ mechanochemically tailorable 2D gallium oxyselenide for enhanced optoelectronic NO2 gas sensing at room temperature

The adverse effects of NO₂ on the environment and human health promote the development of high-performance gas sensors to address the need for monitoring. Two-dimensional (2D) metal chalcogenides have been considered an emerging group of NO₂-sensitive materials, while incomplete recovery and low long-term stability are the two major hurdles for their practical implementation. The transformation into oxychalcogenides is an effective strategy to alleviate these drawbacks, but usually requires multiple-step synthesis and lacks controllability. Here, we prepare tailorable 2D p-type gallium oxyselenide with the thicknesses of 3-4 nm, through a single-step mechanochemical synthesis that combines the in-situ exfoliation and oxidation of bulk crystals. The optoelectronic NO₂ sensing performances of such 2D gallium oxyselenide with different oxygen contents are investigated at room temperature, in which 2D GaSe_0.58O_0.42 exhibits the largest response magnitude of 82.2% towards 10 ppm NO₂ at the irradiation of UV, with full reversibility, excellent selectivity, and long term stability for at least one month. Such overall performances are significantly improved over those of reported oxygen-incorporated metal chalcogenide-based NO₂ sensors. This work provides a feasible approach to prepare 2D metal oxychalcogenides in a single-step manner and demonstrates their great potential for room-temperature fully reversible gas sensing.

Synergy of S-vacancy and heterostructure in BiOCl/Bi2S3-x boosting room-temperature NO2 sensing

The special physicochemical properties of Bi₂S₃ nanomaterial endow it to be exceptional NO₂ sensing properties. However, sensors based on pure Bi₂S₃ cannot detect trace NO₂ at room temperature effectively due to the scanty active sites and poor charge transfer efficiency. Herein, vacancy defect and heterostructure engineering are rationally integrated to explore BiOCl/Bi₂S_3-x heterostructure with rich S vacancies to enhance NO₂ sensing performance. The optimized sensor based on S-vacancy-rich BiOCl/Bi₂S_3-x heterostructure exhibited a high response value (R_g/R_a = 29.1) to 1 ppm NO₂ at room temperature, which was about 17 times compared to the pristine Bi₂S₃. Meanwhile, the BiOCl/Bi₂S_3-x sensor also exhibited a short response time (36 s) towards 1 ppm NO₂ and a low theoretical detection limit (2 ppb). The superior response value of S-vacancy-rich BiOCl/Bi₂S_3-x heterostructures was ascribed to the improved electron migration at the heterointerface and the additional exposed active sites caused by the S vacancies in Bi₂S_3-x. Additionally, the sensors based on S-vacancy-rich BiOCl/Bi₂S_3-x heterostructures showed good long-term stability, outstanding selectivity, and good flexibility. This study offers an effective method for synergistically engineering defect and heterostructure to enhance gas sensing properties at room temperature.

Selective detection of trace carbon monoxide at room temperature based on CuO nanosheets exposed to (111) crystal facets

In recent years, carbon monoxide (CO) intoxication incidents occur frequently, and the sensitive detection of CO is particularly significant. At present, most reported carbon monoxide (CO) sensors meet the disadvantage of high working temperature. It is always a challenge to realize the sensitive detection of carbon monoxide at room temperature. In this study, CuO nanosheets exposed more (111) active crystal facets and oxygen vacancy defects were synthesized by a simple and environmentally friendly one-step hydrothermal method. The sensor has good comprehensive gas sensing performance, compared with other sensors that can detect CO at room temperature. The response value to 100 ppm CO at room temperature is as high as 39.6. In addition, it also has excellent selectivity, low detection limit (100 ppb), good reproducibility, moisture resistance and long-term stability (60 days). This excellent gas sensing performance is attributed to the special structural characteristics of 2D materials and the synergistic effect of more active crystal facets exposed on the crystal surface and oxygen vacancy defects. Therefore, it is expected to become a promising sensitive material for rapid and accurate detection of trace CO gas under low energy consumption, reduce the risk of poisoning, and then effectively protect human life safety.

Atmospheric Pressure Solvothermal Synthesis of Nanoscale SnO2 and Its Application in Microextrusion Printing of a Thick-Film Chemosensor Material for Effective Ethanol Detection

The atmospheric pressure solvothermal (APS) synthesis of nanocrystalline SnO₂ (average size of coherent scattering regions (CSR)-7.5 ± 0.6 nm) using tin acetylacetonate as a precursor was studied. The resulting nanopowder was used as a functional ink component in microextrusion printing of a tin dioxide thick film on the surface of a Pt/Al₂O₃/Pt chip. Synchronous thermal analysis shows that the resulting semiproduct is transformed completely into tin dioxide nanopowder at 400 °C within 1 h. The SnO₂ powder and the resulting film were shown to have a cassiterite-type structure according to X-ray diffraction analysis, and IR spectroscopy was used to establish the set of functional groups in the material composition. The microstructural features of the tin dioxide powder were analyzed using scanning (SEM) and transmission (TEM) electron microscopy: the average size of the oxide powder particles was 8.2 ± 0.7 nm. Various atomic force microscopy (AFM) techniques were employed to investigate the topography of the oxide film and to build maps of surface capacitance and potential distribution. The temperature dependence of the electrical conductivity of the printed SnO₂ film was studied using impedance spectroscopy. The chemosensory properties of the formed material when detecting H₂, CO, NH₃, C₆H₆, C₃H₆O and C₂H₅OH, including at varying humidity, were also examined. It was demonstrated that the obtained SnO₂ film has an increased sensitivity (the sensory response value was 1.4-63.5) and selectivity for detection of 4-100 ppm C₂H₅OH at an operating temperature of 200 °C.

Controllable construction of ZnFe2O4-based micro-nano heterostructure for the rapid detection and degradation of VOCs

Micro-nano heterogeneous oxides have received extensive attention due to their distinctive physicochemical properties. However, it is a challenge to prepare the hierarchical multicomponent metal oxide nanomaterials with abundant heterogeneous interfaces in a controllable way. In this work, the effective construction of the heterogeneous structure of the material is achieved by regulating the ratio of metal salts under thermal solvent condition. Three-dimensional spheres (ZnFe₂O₄) constructed by zero-dimensional ultra-small nanoparticles, in particular three-dimensional hollow sea urchin spheres (ZnO/ZnFe₂O₄) constructed by one-dimensional nanorods and three-dimensional hydrangeas (α-Fe₂O₃/ZnFe₂O₄) assembled by two-dimensional nanosheets were obtained. The two composite materials contain a large number of heterojunctions, which enhances the sensitivity of material to volatile organic compounds gas. Among them, the α-Fe₂O₃/ZnFe₂O₄ composite shows the best sensing performance for VOCs. For example, its response to 100 ppm acetone reaches 142 at 170 °C with the response time shortened to 3 s and the detection limit falling to 10 ppb. Meanwhile, the composite material presents a degradation rate of more than 90% for VOCs at a flow rate of 20 mL/min at 170 °C. In addition, the sensing and sensitivity mechanism of the composite material are studied in detail by combining GC-MS, XPS with UV diffuse reflectance tests.

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.

Multifunctional Sensors Based on Doped Indium Oxide Nanocrystals

There is an increasing need for multifunctional sensors that can detect radiation, biological activity, gas, etc. for efficient health monitoring, neurological medical devices, and human-machine interfaces in recent years. Herein, we demonstrated a multifunctional Sn-doped In₂O₃ nanocrystal (ITO NC) based device for ulyoutraviolet (UV)/infrared (IR) dual-band photodetection and light-activated efficient nitrogen dioxide (NO₂) gas sensing at room temperature (RT). The effects of different surface ligands and annealing process of ITO NCs on their photodetection performance were investigated. The ITO NCs capped with 1,2-ethanedithiol (EDT) show a responsivity of 31.3/177.7 mA W^-1 and normalized detectivity of ∼1 × 10¹⁰/10⁹ cm Hz^1/2 W^-1 under UV/IR illumination at 375/2200 nm at RT. The potential of the ITO NCs sensors to monitor low concentrations of NO₂ is activated by light illumination. The sensor has a higher response (4.2) to 1 ppm of NO₂, shorter response/recovery time (156.8/554.2 s), and a lower detection limit (LOD) (219 ppb) under UV illumination compared within a dark environment. The LOD of the sensor is lower than the allowable exposure limit of NO₂ specified in "Air Pollutant Limits" of the Occupational Safety and Health Administration (OSHA). Our work paves an alternative platform for the development of low-cost, integration-friendly multifunctional devices.

A Flexible and Wearable Nylon Fiber Sensor Modified by Reduced Graphene Oxide and ZnO Quantum Dots for Wide-Range NO2 Gas Detection at Room Temperature

Reduced graphene oxide (rGO) fiber as a carbon-based fiber sensor has aroused widespread interest in the field of gas sensing. However, the low response value and poor flexibility of the rGO fiber sensor severely limit its application in the field of flexible wearable electronics. In this paper, a flexible and wearable nylon fiber sensor modified by rGO and ZnO quantum dots (QDs) is proposed for wide-range NO₂ gas detection at room temperature. The response value of the nylon fiber sensor to 100 ppm NO₂ gas is as high as 0.4958, and the response time and recovery time are 216.2 s and 667.9 s, respectively. The relationship between the sensor's response value and the NO₂ concentration value is linear in the range of 20-100 ppm, and the fitting coefficient is 0.998. In addition, the test results show that the sensor also has good repeatability, flexibility, and selectivity. Moreover, an early warning module was also designed and is proposed in this paper to realize the over-limit monitoring of NO₂ gas, and the flexible sensor was embedded in a mask, demonstrating its great application potential and value in the field of wearable electronics.

Wool-Based Carbon Fiber/MoS2 Composite Prepared by Low-Temperature Catalytic Hydrothermal Method and Its Application in the Field of Gas Sensors

Under the background of the Paris Agreement on reducing greenhouse gases, waste wools were converted into wool carbon fiber (WCF) and WCF–MoS₂ composites by low-temperature catalytic hydrothermal carbonization. Their structures and gas-sensing performances were studied for the first time. Due to the existence of heterojunctions, the responses of the WCF–MoS₂ composite to the five analytes were 3–400 times those of MoS₂ and 2–11 times those of WCF. Interestingly, because of the N, P, and S elements contained in wools, the WCF prepared by the hydrothermal method was realized the doping of N, P, and S, which caused the sensing curves of WCF to have different shapes for different analytes. This characteristic was also well demonstrated by the WCF–MoS₂ composite, which inspired us to realize the discriminative detection only by a single WCF–MoS₂ sensor and image recognition technology. What’s more, the WCF–MoS₂ composite also showed a high sensitivity, a high selectivity, and a rapid response to NH₃. The response time and the recovery time to 3 ppm NH₃ were about 16 and 5 s, respectively. The detection of limit of WCF–MoS₂ for NH₃ was 19.1 ppb. This work provides a new idea for the development of sensors and the resource utilization of wool waste.

Exogenous melatonin alleviates NO2 damage in tobacco leaves by promoting antioxidant defense, modulating redox homeostasis, and signal transduction

Nitrogen dioxide (NO2) is a common outdoor air pollutant, which has adverse effects on the environment and human health. Herein, NO2 inhibited photosynthesis and antioxidant capacity in plants. Melatonin (Mel) is a neurohormone found in the pineal gland. Exogenous Mel alleviated chlorophyll degradation and increased the expression of key proteins and genes in the process of chlorophyll synthesis in tobacco leaves exposed to NO2. Additionally, the activities of photosystem II (PSII) and photosystem I (PSI) were enhanced. PSII and PSI reaction center proteins and genes were upregulated. Mel pre-treatment enhanced enzyme activities and expression of proteins related to the ascorbic acid-glutathione cycle and thioredoxin-peroxiredoxin pathway in leaves exposed to NO2, thus regulating their redox balance. Furthermore, exogenous Mel mediated the polyamine synthesis pathway and increased the expression of the key enzyme proteins SAMS1, SAMS2, and SAMS3 in the polyamine synthesis pathway in leaves under NO2 stress. Mel regulated ABA signal transduction and calmodulin binding transcription factors CAMTA12 and NtCaM calmodulin NtCaM2 in Ca2+ signal transduction. Collectively, these results elucidate that Mel can alleviate high-concentration NO2, thus suitable for agricultural application.

Synergistic approach to simultaneously improve response and humidity-independence of metal-oxide gas sensors

The chemiresistive response of metal-oxide gas sensors depends on ambient conditions. Humidity is a strongly influential parameter and causes large deviations in signals and, consequently, an inaccurate detection of target gases. Developing sensors unaffected by humidity, as documented by extensive works of research, comes at the cost of response - a significant drop in sensor response inevitably accompanies an increase in humidity-independence. This trade-off between humidity-independence and gas response is one of the major obstacles that limit practical applications of metal-oxide gas sensors. This study presents a novel approach to improve both the features by incorporating the rare-earth element, yttrium, into the host SnO₂ sensor. The Y-doped SnO₂ nanofibers are highly stable across relative humidity values ranging from 0% to 87%, and show improved selectivity and sensitivity in the detection of up to 20 ppb of NO₂ target gas with the limit of detection at 103.71 ppt. Based on experimental results and van der Waals (vdW)-corrected DFT calculations, these improvements can be attributed to the synergistic effect of oxygen vacancy created by the introduction of aliovalent Y and the formation of Y₂O₃ nanoparticles that play a critical role in making the sensor surface hydrophobic.