Acetone Sensor Research Articles

The Jahn–Teller distortion‐induced electronic structure regulation of Mn‐doped Co3O4 for enhanced acetone detection

AbstractThe modulation of the electronic structure of metal oxides is crucial to enhance their gas‐sensing performance. However, there is lacking in profound study on the effect of electronic structure regulation on sensing performance. Herein, we propose an innovative strategy of Jahn–Teller distortion‐induced electronic configuration regulation of Co3O4 to improve acetone sensing performance. After the introduction of Mn3+ into Co3O4 (Mn‐Co3O4), the Jahn–Teller distortion of high‐spin Mn3+ (t2g3eg1) conversed to low‐spin Mn4+ (t2g3eg0), resulting in conversion of Co3+ (t2g6eg0) into Co2+ (t2g6eg1). As expected, Mn‐Co3O4 exhibits a high response value of 46.7 toward 100 ppm acetone, low limit of detection of 0.75 ppb, high selectivity, and high stability, which are overwhelmingly superior to previous Co3O4‐based acetone sensors. The dynamics and thermodynamics analysis demonstrate that the Mn doping improves sensing reaction rate, reduces reaction barrier, and promotes the charge transfer. The theoretical calculations further prove the charge transfer from Mn to Co derived from Jahn–Teller distortion and support promoting the adsorption of acetone on Co3O4 by Mn dopant. Moreover, we demonstrated the substantial potential application of Mn‐Co3O4 sensor as a monitoring gas sensor in pest resistance of Arabidopsis. This work provides a new strategy to design sensing materials from electronic configuration perspective.image

Vitalizing Perovskite Oxide-Based Acetone Sensors with Metal-Organic Framework-Derived Heterogeneous Oxide Catalysts.

Perovskite oxides are promising candidates for chemiresistive-type gas sensors owing to their exceptional thermal and chemical stability during solid-gas reactions. However, perovskites suffer from critical issues such as low surface area and poor surface activity, which negatively influence the sensing characteristics. While metal nanoparticles can be incorporated in perovskites to improve their reactivity, the fundamental incompatibility between catalytic metals and perovskite oxides often leads to substantial structural degradation as well as phase instability. Herein, we overcome this challenge through the introduction of an intermediary phase that forms coherent interfaces with both the perovskite phase and catalyst metals. Specifically, we present the case study of p-type La0.8Ca0.2Fe0.98Pt0.02O3 perovskite, whose hole accumulation layer was modulated by the incorporation of metal-organic framework (MOF)-derived n-type α-Fe2O3 nanoparticles decorated with highly dispersed Pt catalysts. The resulting composite exhibited significantly improved surface activity over the nonmodified La0.8Ca0.2FeO3 perovskite, leading to exceptional chemiresistive sensing performance toward acetone gas (Rg/Ra = 39.8 toward 10 ppm of acetone at 250 °C) with high cross-sensitivity against interfering gases. Importantly, our findings reaffirm the critical influence of interfacial engineering in facilitating surface chemical reactions on perovskite oxides and, by doing so, effectively provide a general synthetic guideline to the design of perovskite-based chemiresistors.

Temperature-modulated acetone monitoring using Al2O3-coated evanescent wave fiber optic sensors

This paper presents an experimental study of a fiber-optic-based acetone sensor and its temperature effects for use as a breath analyzer to detect acetone in exhaled breath. The study employs fiber optic evanescent wave-based acetone sensing, utilizing sputter coated Aluminium Oxide (Al2O3)-coated probes fabricated via clad modification technique. The optical fibers were coated with Al2O3 to achieve thicknesses of 247.03 nm, 334.05 nm, and 468.75 nm. The sensor probes were characterized using, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Ultraviolet-Visible (UV-Vis) Spectroscopy, and Spectroscopic Ellipsometry for uniformity, elemental, optical constants, and thickness of the Al2O3. The spectral responses of the probes were analyzed for acetone concentrations ranging from 0 to 100 ppm, with temperature modulation from room temperature to 100 °C. The probe with a ∼334 nm thick Al2O3 coating exhibited the highest response, reaching 6.2 % at 100 °C in 100 ppm acetone. Linear regression revealed that the ∼334 nm coated probe had the highest sensitivity at 5.98 counts/ppm. The sensor showed response and recovery times of approximately 12 and 17 seconds, respectively. This study underscores the stability and repeatability of temperature-modulated Al2O3-coated fiber optic sensors for selective acetone detection in various non-invasive applications.

Acetone Sensors Based on Al-Coated and Ni-Doped Copper Oxide Nanocrystalline Thin Films.

Acetone detection is of significant importance in various industries, from cosmetics to pharmaceuticals, bioengineering, and paints. Sensor manufacturing involves the use of different semiconductor materials as well as different metals for doping and functionalization, allowing them to achieve advanced or unique properties in different sensor applications. In the healthcare field, these sensors play a crucial role in the non-invasive diagnosis of various diseases, offering a potential way to monitor metabolic conditions by analyzing respiration. This article presents the synthesis method, using chemical solutions and rapid thermal annealing technology, to obtain Al-functionalized and Ni-doped copper oxide (Al/CuO:Ni) nanostructured thin films for biosensors. The nanocrystalline thin films are subjected to a thorough characterization, with examination of the morphological properties by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analysis. The results reveal notable changes in the surface morphology and structure following different treatments, providing insight into the mechanism of function and selectivity of these nanostructures for gases and volatile compounds. The study highlights the high selectivity of developed Al/CuO:Ni nanostructures towards acetone vapors at different concentrations from 1 ppm to 1000 ppm. Gas sensitivity is evaluated over a range of operating temperatures, indicating optimum performance at 300 °C and 350 °C with the maximum sensor signal (S) response obtained being 45% and 50%, respectively, to 50 ppm gas concentration. This work shows the high potential of developed technology for obtaining Al/CuO:Ni nanostructured thin films as next-generation materials for improving the sensitivity and selectivity of acetone sensors for practical applications as breath detectors in biomedical diagnostics, in particular for diabetes monitoring. It also emphasizes the importance of these sensors in ensuring industrial safety by preventing adverse health and environmental effects of exposure to acetone.

Group VIII Transition Metal (Fe, Ru & Os) Embedded Graphitic Carbon Nitride as an Acetone Sensor: A First Principle Investigation

This study investigates the acetone sensing behavior of pristine graphitic carbon nitride (gCN) and group VIII transition metal (Fe, Ru & Os) embedded gCN monolayer using DFT calculations. Key structural and electronic properties such as adsorption energy, band structure, and density of states (DOS) have been examined. The calculated adsorption energy of pristine gCN is −1.32 eV, which improves to –3.52, −2.75, and −1.73 eV for Fe, Ru, and Os embedded gCN, respectively. The band structure also indicates a reduction in the band gap of gCN after acetone adsorption due to the introduction of Fe, Ru, and Os. Furthermore, after the adsorption of acetone, the DOS values exhibit a significant increase from 13.48 eV−1 for pristine gCN to 439, 423, and 332 eV−1 for Fe, Ru, and Os embedded gCN, respectively.

Liquid crystal gel-based acetone sensor using correlated laser speckles

Acetone, a common volatile organic compound (VOC), poses health risks even at low concentrations. Current acetone sensors are costly and require specialized equipment and expertise. This work develops a novel vapor sensor for determining acetone vapor concentration using the speckle patterns generated by liquid crystal gels (LCGs). The vapor sensor comprises a LCG film prepared by the phase separation of a mixture containing polystyrene microspheres and liquid crystals (LCs). The orientation of the LC molecules changes when the LCG film is exposed to an acetone vapor environment, altering the equivalent refractive indices of the LC domains. This leads to a change in the scattering state of the LCG film under laser illumination, forming different speckle patterns. The concentration of acetone vapor is determined by calculating the correlation coefficient of the speckle images, where the sensitivity and limit of detection of the sensor are 4×10-4 ppm-1 and 754.05 ppm, respectively. The developed correlated laser speckle-based optical system is simpler, less expensive, and more stable than traditional LC film vapor sensors. This acetone gas sensor has potential applications in industrial and indoor air quality testing.

Construction of a novel Mott-Schottky heterostructure gas sensor g-C3N4/SnO2 with layered nanorods array for high-sensitivity acetone detection

Developing exhaled acetone sensors with high performance can be effectively applied to the medical diagnosis and the health monitoring. Herein, a two-dimensional (2D) layered graphitic carbon nitride (g-C3N4) with tunable electronic structure, abundant edge sites, and high stability is proposed, and it is further coupled with stannic oxide (SnO2) by one-step hydrothermal approach to construct a Mott-Schottky heterostructure with layered nanorods array. The exceptional response of the as-fabricated g-C3N4/SnO2 gas sensor to 50 ppm acetone at 100 °C is four times higher than that of the pristine SnO2 sensor. Additionally, the g-C3N4/SnO2 sensor’s remarkable selectivity, long-term stability against acetone gas, and detection limit of 250 ppb are exhibited. The unique hierarchical design and the Mott-Schottky heterostructure creation which validated by electrochemical study, may be in charge of the enhanced acetone sensing capabilities of g-C3N4/SnO2 gas sensor. This work will provide a concise and effective avenue to construct hierarchical composite with Mott-Schottky heterostructure for high-performance acetone gas sensor.

Development of a high property acetone sensor based on TiO2 core-shell spheres and their sensing mechanism analysis

Development of a high property acetone sensor based on TiO2 core-shell spheres and their sensing mechanism analysis

Hierarchical ultra-thin porous Co3O4 nanosheets derived from mixed phase α- and β-Co(OH)2 for high sensitivity and ppb-level acetone sensing

Addressing the energy loss of carriers during transmission and achieving high sensitivity detection of target gases facilitates the synthesis of trace-level acetone sensors, which is of great significance in the fields of air quality early warning, health monitoring, and industrial safety monitoring. Here, we propose a strategy where, under hydrothermal conditions, the content of mixed-phase α- and β-Co(OH)2 is regulated by varying the protonation level of 2-methylimidazole in different solutions, leading to the formation of porous monocrystalline Co3O4 microflower structure. The microflower is assembled from ultrathin nanosheets, and the 3D-interconnected macroporous and mesoporous structure provides high surface area and gas diffusion channels. The monocrystalline and two-dimensional structures favor high carrier mobility, enhancing the signal-to-noise ratio. Furthermore, the thickness of the Co3O4 nanosheets is less than twice the Debye length, making their electrical properties completely dependent on surface. DFT calculations also indicate that the few layers Co3O4 model is conducive to acetone adsorption. The Co3O4 sensor exhibits exceptional gas sensing performance towards acetone, with favourable sensitivity (16.83 to 10 ppm), selectivity, and stability, as well as an ultra-low practical detection limit of 10 ppb. Rich point defects and line defects play a significant role in improving the surface activity of the sensitive material as well. This research offers a pathway for designing sensors with exceptional gas sensitivity by employing a straightforward method to control the morphology of sensitive materials, combined with defect engineering to enhance sensing activity.

A highly sensitive and fully flexible Fe-Co metal-organic framework hydrogel based gas sensor for ppb level detection of acetone

Most nanomaterials based gas sensors are established on rigid substrates which require operation at elevated temperature and involve long recovery times, thus, limiting their practical applications. Addressing these issues, we demonstrate a fully flexible Fe/Co metal organic framework hydrogel (Fe/Co MOF HG) based gas sensor that detects ultra-low concentrations of acetone at room temperature. This hydrogel is synthesized using optimized concentration (3:1 M ratio) of Co:Fe with benzene dicarboxylic acid (BDC) in Fe/Co MOF via solvothermal method followed by lyophilization. Detailed morphological evaluation reveals 3-dimentional porous structure with multiple voids which largely enhances the specific surface area. Upon exposure to acetone, the Fe/Co MOF HG with Cu metal contacts based sensor exhibits a sensing response (S%) of 12.28 % to 500 ppb of acetone with a wide dynamic range of 200 ppb to 4 ppm. This remarkable sensitivity can be attributed to the abundance of water-adsorbed oxygen (Oc% = 24.58 %) in hydrogel as confirmed by XPS technique, which helps in the increase of the adsorption of a large proportion of acetone molecules on the surface of hydrogel. The limit of detection (LOD = 3σ/s) is found to be 103 ppb which is significantly lower than the other reported MOF-based acetone sensors. Further, the sensor demonstrates excellent selectivity against other common VOCs such as ammonia, benzene, toluene, and formaldehyde. Finally, the sensor’s outstanding stability (upto one-month), mechanical robustness when subjected to 230 cycles of bending and resilience to changes in humidity opens up new possibilities for the use of MOF-based hydrogels as gas sensors in several wearable device domains, such as health care and environmental monitoring.

Efficient mixed-potential acetone sensor with yttria-stabilized zirconia and porous Co3O4 nanofoam sensing electrode for hazardous gas monitoring and breath analysis

For hazardous gas monitoring and non-invasive diagnosis of diabetes using breath analysis, porous foams assembled by Co3O4 nanoparticles were designed as sensing electrode materials to fabricate efficient yttria-stabilized zirconia (YSZ)-based acetone sensors. The sensitivity of the sensors was improved by varying the sintering temperature to regulate the morphology. Compared to other materials sintered at different temperatures, the porous Co3O4 nanofoams sintered at 800 °C exhibited the highest electrochemical catalytic activity during the electrochemical test. The response of the corresponding Co3O4-based sensor to 10 ppm acetone was –77.2 mV and it exhibited fast response and recovery times. Moreover, the fabricated sensor achieved a low detection limit of 0.05 ppm and a high sensitivity of –56 mV/decade in the acetone concentration range of 1–20 ppm. The sensor also exhibited excellent repeatability, acceptable selectivity, good O2/humidity resistance, and long-term stability during continuous measurements for over 30 days. Moreover, the fabricated sensor was used to determine the acetone concentration in the exhaled breaths of patients with diabetic ketosis. The results indicated that it could distinguish between healthy individuals and patients with diabetic ketosis, thereby proving its abilities to diagnose and monitor diabetic ketosis. Based on its excellent sensitivity and exhaled breath measurement results, the developed sensor has broad application prospects.

Study on the acetone adsorption mechanism of In2O3/SnO2 heterocomposite fibers

A heterocomposite structure offers significant advantages for enhancing the gas sensing performance of metal oxide-based sensors. In this study, In2O3/SnO2 heterocomposite fibers were fabricated by electrospinning. In2O3/SnO2 heterocomposite fibers show excellent gas sensing performance for acetone. The response of the In2O3/SnO2 sensor is 9.3–100 ppm acetone, markedly outperforming sensors made solely of SnO2 or In2O3. To clarify the improved mechanism, the adsorption behavior of In2O3/SnO2 for acetone was studied based on Density Functional Theory (DFT). The adsorption energy of In2O3/SnO2 for acetone at the optimal adsorption site is 0.89 |eV|, which is 0.18 |eV| and 0.04 |eV| higher than that of SnO2 and In2O3, respectively. Additionally, the electron transfer numbers of acetone to In2O3/SnO2 are also 0.08|e| and 0.05|e| greater than those of SnO2 and In2O3, respectively. The n-n heterojunction of In2O3/SnO2 alters the material's barrier, significantly enhancing carrier concentration and electron transfer. This n-n heterojunction is key to the improved gas sensing performance of the In2O3/SnO2 sensor for acetone. Therefore, In2O3/SnO2 heterocomposite fibers have great application potential in the field of gas sensors.

Unlocking Co3O4–ZnO p-n heterojunction for superior acetone gas sensing detection

In this study, we synthesized pure ZnO and Co3O4–ZnO precursors with varied Co, Zn ratios via solvothermal method, and then the precursors were calcined at 400 ​°C for 2 ​h in a muffle furnace under air to obtain composites for acetone detection. The structure, morphology, elemental composition, microstructure and chemical state of these materials were systematically studied by various characterization techniques. Additionally, we also evaluated the gas sensing performance of the composites-based sensors, focusing on optimal operating temperature, baseline resistance, repeatability, stability, selectivity, response/recovery time, and resistance under varying relative humidity. The findings reveal that 3 ​% Co3O4–ZnO-based sensor exhibit the highest response value to 100 ​ppm acetone (74), showing an enhancement of approximately 9.3 times compared to the pure ZnO-based sensor (8). Furthermore, the 3 ​% Co3O4–ZnO-based sensor demonstrate the advantages of rapid response/recovery times (15 ​s/2 ​s), outstanding selectivity, and remarkable stability. The gas sensing mechanism of the composite material is also discussed in detail, which provides insights into the observed enhancement of gas sensing performance. It provides an idea for the follow-up study on gas sensing performance of acetone sensors.

Enhanced acetone detection performance of mechanically-mixed WO3:ZnO composites

In recent years, the potential use of mixed metal oxide WO3:ZnO is widely sought in photocatalytic application due to its excellent electrical and optical properties, but is less explored for chemiresistive sensor. The heterojunction effect in WO3:ZnO is of particular interest to eradicate common issues suffered by the pristine metal oxide sensors, such as limited sensitivity, poor selectivity, and high operating temperature. In addition, the acetone detection study based on heterostructured WO3:ZnO is quite limited. Herein, we demonstrate that the mechanically-mixed WO3:ZnO sensor exhibits comparable reducing gas sensing performance as other doped WO3:ZnO and relative improvement compared with the undoped composites, without the need of catalyst. In this work, WO3:ZnO thin-film based chemiresistive sensors were fabricated through straightforward methods comprising mechanical mixing and drop casting of sensor materials onto gold interdigitated alumina substrates. Structural and morphological properties of the prepared WO3, ZnO, and WO3:ZnO composites were examined through the X-ray diffraction (XRD), Raman spectroscopy, photoluminescence spectroscopy (PL), field-emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDX) analyses, respectively. Sensor performance parameters including operating temperature and response were determined. The sensing properties of WO3:ZnO composites with different weight compositions (1:1, 1:2, and 1:3) were evaluated against the pristine ZnO and WO3. The weight ratio of 1:2 was the optimal composition for the WO3:ZnO composite to achieve the highest sensor response of 53.8 % towards 300 ppm acetone at 200 ºC compared to the pristine ZnO with a response of 23.5 %. The WO3:ZnO (1:2) thin film displayed granular morphology with uniform particle dispersion and porosity, enhancing the gas diffusion. The WO3:ZnO (1:2) thin-film composite sensor exhibited improved sensing performance and good repeatability towards acetone compared with that of ZnO and WO3. The enhanced response to acetone was possibly contributed by the development of n-n heterojunctions, porous morphology, and surface defects in the WO3:ZnO composite. The underlying sensing mechanism of WO3:ZnO composite is also discussed extensively with the aid of energy band diagrams. This study presents a foundation for future development of cost-effective acetone sensors through mechanical mixing with great potential for practical and scalable implementation in various industries.

Room temperature ultrasensitive detection of acetone vapours via noble metal anchored reduced graphene oxide

Developing a low-cost, realistic room temperature operable acetone sensor is highly desirable in industrial and medical sectors for environmental monitoring and diagnostic purposes. The present study focuses on the simple co-reduction route to synthesize noble metal nanoparticle decorated reduced graphene oxide (rGO) and investigating the acetone sensing ability by using them as sensing materials to fulfil the requirements. Various spectroscopic and microscopic tools were employed to probe the structural and morphological details of the prepared materials. Gas sensing tests demonstrated the selective identification of acetone by the developed sensors, with the sensing materials exhibiting remarkable response at room temperature. The decoration of gold nanoparticles on reduced graphene oxide (AurGO) notably enhanced the response (1.87%) compared to pure rGO (0.65%). Despite a decrease in response with silver loading on rGO (AgrGO) (0.20%), sensors based on AgrGO exhibited rapid response and recovery times (49/38 seconds) compared to those of rGO (90/116 seconds) and AurGO (136/150 seconds). The acetone sensing mechanism is discussed in detail by predicting the band structure modification under the acetone exposure. The superior selectivity, repeatability, and long-term stability displayed by all the sensing materials suggest their cutting-edge applicability for real-world applications.

YSZ-based mixed-potential acetone sensor with LaBaCo2O5+δ sensitive electrode for diabetic diagnosis

The acetone concentration in exhaled breath can be utilized for the noninvasive diagnosis of diabetes. In this study, to fulfil the requirements of breath analysis for diabetes diagnosis, high-performance mixed-potential acetone sensors based on yttria-stabilized zirconia were successfully developed by employing a novel sensitive electrode (SE) material, namely, LaBaCo2O5+δ. Electrochemical measurement results revealed that the LaBaCo2O5+δ SE, sintered at 1000 ℃, exhibited outstanding electrochemical catalytic activity toward acetone. The device incorporating this SE demonstrated a peak response of −46 mV to 100 ppm acetone at 655 ℃. Sensitive performance assessments indicated the capability of the sensor to detect acetone concentrations ranging from 200 ppb to 100 ppm. Based on the mixed-potential model, the sensitivities of the current device were quantified as −1.3 and −53.7 mV/decade within the acetone concentration ranges of 0.2−5 and 10−100 ppm, respectively. Furthermore, the fabricated sensor exhibited exceptional selectivity, repeatability, humidity resistance, and long-term stability. In addition, simulated expiratory experiments showed that the developed sensor has substantial potential for application in breath analysis for diabetes diagnosis and noninvasive monitoring of a patient’s physical status.

A solid state electrolyte based enzymatic acetone sensor

This paper introduces a novel solid-state electrolyte-based enzymatic sensor designed for the detection of acetone, along with an examination of its performance under various surface modifications aimed at optimizing its sensing capabilities. To measure acetone concentrations in both liquid and vapor states, cyclic voltammetry and amperometry techniques were employed, utilizing disposable screen-printed electrodes consisting of a platinum working electrode, a platinum counter electrode, and a silver reference electrode. Four different surface modifications, involving different combinations of Nafion (N) and enzyme (E) layers (N + E; N + E + N; N + N + E; N + N + E + N), were tested to identify the most effective configuration for a sensor that can be used for breath acetone detection. The sensor's essential characteristics, including linearity, sensitivity, reproducibility, and limit of detection, were thoroughly evaluated through a range of experiments spanning concentrations from 1 µM to 25 mM. Changes in acetone concentration were monitored by comparing currents readings at different acetone concentrations. The sensor exhibited high sensitivity, and a linear response to acetone concentration in both liquid and gas phases within the specified concentration range, with correlation coefficients ranging from 0.92 to 0.98. Furthermore, the sensor achieved a rapid response time of 30–50 s and an impressive detection limit as low as 0.03 µM. The results indicated that the sensor exhibited the best linearity, sensitivity, and limit of detection when four layers were employed (N + N + E + N).

Synthesis of self-assembled spherical ZnFe2O4 nanomaterials by the premixed stagnation flame method for highly sensitive acetone sensor

The efficient and reliable detection of acetone is critical for industrial safety, environmental monitoring, and human health. Separately, ZnFe2O4 particles were synthesized by using the premixed stagnation flame method and the co-precipitation method. The premixed stagnation flame method was used to create self-assembled spherical ZnFe2O4 nanoparticles with uniform morphology, polycrystalline morphology, and excellent phase purity. The effect of the gas-sensitive performance of these sensors for two routes on acetone vapor was compared. The sensor synthesized using the premixed stagnation flame method had a response value of up to 26 at 235°C for 100 ppm acetone vapor. It revealed outstanding reproducibility, stability, and selectivity for acetone vapor, which is attributed to the 10 nm "lychee-like" particle structure uniformly dispersed on the surface of the 400–500 nm spherical particles, forming a unique self-assembled structure. The self-assembled spherical structure has a large specific surface area, abundant oxygen adsorption, and oxygen vacancies, which effectively increases the reaction sites and electron mobility inside and outside the nanoparticles. The premixed stagnation flame method of producing spherical ZnFe2O4 nanoparticles presents a viable method for developing extremely sensitive, fast-responding, and selective acetone vapor sensors.

Low palladium content CeO2/ZnO composite for acetone sensor with sub-second response prepared by ultrasonic method

Low palladium content CeO2/ZnO composite for acetone sensor with sub-second response prepared by ultrasonic method

Silver nanoparticle functionalized heterojunction NiO/SnO2 nanotubes for comprehensive sensitization of acetone sensor

Acetone detection with a good sensitivity and a low operating temperature is crucial owing to the serious harm that acetone can cause to the environment and humans and its importance as a marker of diabetes in human exhalation. One-dimensional (1D) semiconductor metal oxides with easily accessible active sites are potential candidates for use in gas sensors; however, the facile synthesis of 1D nanotubes (NTs) remains a challenge. Herein, Ag–NiO/SnO2 NTs are synthesized via an electrospinning process, followed by spin-coating permeation and subsequent annealing and chemical reduction; furthermore, the gas-sensing properties of the Ag–NiO/SnO2 NTs are investigated. The Ag–NiO/SnO2 NT-based sensor exhibits a rapid response to acetone (12 s) with excellent sensitivity and selectivity at a low operating temperature (190 °C). The lower acetone detection limit of the Ag–NiO/SnO2 NT-based sensor is 50 ppb. The 1D porous NTs efficiently promote gas diffusion during reversible resistance signal cycling and provide numerous active sites. Furthermore, the conjunction of NiO nanograins with SnO2 nanograins forms a heterogeneous construction, enhancing the gas sensitivity of the sensing layers. In addition, Ag nanoparticles homogeneously incorporated onto the surface of the 1D NTs enhance substantially the acetone detection capability based on noble-metal sensitization.