Ppb-level Acetone Research Articles

Synergistic effect of NiFe2O4 and MWCNTs for ppb-level acetone detection at 150oC

Synergistic effect of NiFe2O4 and MWCNTs for ppb-level acetone detection at 150oC

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.

Bimetallic PtAu-Decorated SnO2 Nanospheres Exhibiting Enhanced Gas Sensitivity for Ppb-Level Acetone Detection.

Acetone is a biomarker found in the expired air of patients suffering from diabetes. Therefore, early and accurate detection of its concentration in the breath of such patients is extremely important. We prepared Tin(IV) oxide (SnO2) nanospheres via hydrothermal treatment and then decorated them with bimetallic PtAu nanoparticles (NPs) employing the approach of in situ reduction. The topology, elemental composition, as well as crystal structure of the prepared materials were studied via field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The findings revealed that bimetallic PtAu-decorated SnO2 nanospheres (PtAu/SnO2) were effectively synthesized as well as PtAu NPs evenly deposited onto the surface of the SnO2 nanospheres. Pure SnO2 nanospheres and PtAu/SnO2 sensors were prepared, and their acetone gas sensitivity was explored. The findings demonstrated that in comparison to pristine SnO2 nanosphere sensors, the sensors based on PtAu/SnO2 displayed superior sensitivity to acetone of 0.166-100 ppm at 300 °C, providing a low theoretical limit of detection equal to 158 ppm. Moreover, the PtAu/SnO2 sensors showed excellent gas response (Ra/Rg = 492.3 to 100 ppm), along with fast response and recovery (14 s/13 s to 10 ppm), good linearity of correlation, excellent repeatability, long-term stability, and satisfactory selectivity at 300 °C. This improved gas sensitivity was because of the electron sensitization of the Pt NPs, the chemical sensitization of the Au NPs, as well as the synergistic effects of bimetallic PtAu. The PtAu/SnO2 sensors have considerable potential for the early diagnosis and screening of diabetes.

Room temperature acetone gas sensing performance of ZnS-NiO nanocomposite sensor enhanced by UV activation for diabetes detection

Metal oxide semiconductors are popular in gas sensor applications.Current metal oxide-based acetone sensors struggle to deliver ppb-level acetone sensing at low temperatures for biological use. This study synthesizes 4mol% ZnS combined with NiO for acetone sensing. Nanoparticles were studied using FE-SEM, XPS, XRD, and UV-Vis spectroscopy. Mixed ZnS and NiO resulted in rapid gas channel movement and n-p heterojunction development, which increased acetone sensitivity. ZnS-NiO showed a gas sensing response of 163% for 20 ppm acetone at room temperature under UV irradiation, which is 2.3 times higher than pristine NiO (70% at 180 ∘C). ZnS improves sensor selectivity. Heterojunction sensor reaction and recovery times were 20 and 14 seconds, respectively. The composite sensor detection limit was 0.1 ppm. The increased sensitivity validates the n-p heterojunction. The sensor’s higher response values and lower detection limit point to breath analyzer applications such as diabetes detection.

Pd/PdO doped WO3 with enhanced selectivity and sensitivity for ppb level acetone and ethanol detection

Ethanol and acetone sensors have a wide variety of applications across different industries. However, it is necessary to improve the performance of such sensors and to understand the underlying mechanisms. In this study, Pd/PdO-WO3 nanoblocks are synthesized via hydrothermal growth and calcination. The Pd and PdO contents of the materials are tuned by varying the Pd doping concentration and annealing temperature. The gas sensing performance of the nanoparticles is investigated, which shows that Pd doping increases the sensitivity and reduces the optimum operating temperature. At 200 °C, Pd/PdO-WO3 nanoblocks with different PdO ratios exhibit good sensitivity to acetone and ethanol. However, because PdO is an active catalyst for ethanol oxidation, the oxygen sensitivity increases as the PdO ratio increases. The prepared sensors exhibit good stability and excellent selectivity against a variety of interferents, and the detection limit of the target gas is 100 ppb. The chemical and electronic sensitization of Pd/PdO lowers the activation barrier and improves the gas sensing response. This study demonstrates that the selectivity of a gas sensor can be regulated by controlling the electronic states of the active species.

Facile synthesis of novel YbFeO3–BiFeO3 composite for highly sensitive ppb-level acetone sensing at low temperature

Facile synthesis of novel YbFeO3–BiFeO3 composite for highly sensitive ppb-level acetone sensing at low temperature

A bottom-up sonication-assisted synthesis of Zn-BTC MOF nanosheets and the ppb-level acetone detection of their derived ZnO nanosheets

Two-dimensional metal-organic framework nanosheets, as a new member of the two-dimensional family, are attracting increasing research interest in various fields. Herein, a uniform two-dimensional Zn-BTC MOF nanosheet with a thickness of 14 ± 2 nm was synthesized through a simple, efficient, and scalable sonication-assisted bottom-up strategy. The ZnO nanoparticles were used as the Zn source, which can be corroded by H3BTC to form Zn-BTC MOFs under sonication conditions. The morphologies of Zn-BTC MOFs can be modulated from nanosheets to nanorods by changing the content of H3BTC. The crystal growth process is dominated by the thermodynamics of sonication and the stoichiometric ratio of the generated Zn2+ and H3BTC, and the crystal growth mechanism was elaborated by the oriented attachment. Consequently, a chemiresistive gas sensor based on Zn-BTC nanosheet derivatives was fabricated to detect ppb-level acetone. Notably, the experimental detection limit of concentration could reach as low as 100 ppb of acetone due to the functional surface, and the dynamic response linearity reached 99 %. Our work explored a new method of synthesizing two-dimensional Zn-BTC MOF, and the fabricated gas sensing device demonstrated promising potential in gas sensing fields.

Behavioral remodeling of perovskite BiFeO3 by Ag-doping strategies for enhanced and ppb level acetone sensing performance: An advanced enlightenment for selectivity and sensing mechanism

Improvement of the catalytic reactions on the sensing surface or modulation of charge carriers of the sensing material are the most favorable ways to enhance sensing performance for a chemi-resistive sensor. Incorporation of noble metals can enhance the sensing features of chemi-resistive type sensors by synergistic effect of chemical (catalytic effect) or electronic (tuning of charge carrier concentration) sensitization. In this view, the present study performs a behavioral remodeling of sol-gel synthesized BiFeO3 (BFO) chemi-resistive sensor by low-cost Ag-doping strategies to enhance its acetone sensing performance with removal of irreversibility. The Ag-doped BFO (Bi0.9Ag0.1FeO3) sensor can selectively detect acetone vapor (Rcross = RAcetone/RXylene: 17; RAcetone/RHexane: 08; RAcetone/RToluene: 05; RAcetone/RMethanol: 2.5; RAcetone/REthanol: 2.2) operating at 350°C. Ag-BFO sample shows an enhancement (1.8-fold) in response (R∼22) value with 5-fold faster response time (τres∼8s) for 50 ppm acetone exposure compared to pristine BFO (R∼12, τres∼45s). Excellent repeatability over 09 loop character with high degree of long-term stability for 300 days and ppb level detection (500 ppb) favorable to biomarker recognition for critical diseases confirms the commercial viability of Ag-doped BFO sample. The ion-dipole (highest interaction energy, Ei-d = -1.02 × 10−19 J for acetone)/dipole-dipole coupling, the ferroelectric nature of BiFeO3 and sensitization effect (by metallic Ag-phase) has paved the path for revealing the selectivity and sensing mechanism for the prepared prototype in an innovative way.

Polyoxometalate-assisted in situ growth of ZnMoO4 on ZnO nanofibers for the selective detection of ppb-level acetone

One-dimensional (1D) semiconductor composite nanofibers (NFs) with large specific surface areas, high length-to-diameter ratios, and abundant interfacial active sites have received widespread attention. In this work, a rationally designed 1D composite NFs architecture for detecting acetone is synthesized via a two-step process based on electrospinning followed by a thermal oxidation method. Utilizing the polyoxometalate (POM) as a molecular platform with high negative charges to combine transition metal ions precursors, highly dispersed ZnMoO4 can be in situ grown on the ZnO. By adjusting the content of POM (H3PMo12O40, denoted as PMo12) in the precursor solution, we can obtain a series of ZnMoO4 decorated ZnO NFs (ZnMoO4-ZnO NFs). Compared with the pristine ZnO NFs, the ZnMoO4-ZnO NFs sensor exhibited excellent sensing characteristics over a wide range of acetone concentrations (50 ppb-50 ppm), such as high sensitivity , relatively low detection concentration, and high selectivity. The primary mechanism for the improved acetone gas sensing properties of the ZnMoO4-ZnO NFs could be ascribed to the available charge transfer and unique structure within ZnMoO4-ZnO NFs.

Phosphorus-doped porous perovskite LaFe1-xPxO3-δ nanosheets with rich surface oxygen vacancies for ppb level acetone sensing at low temperature

• O v defect-rich phosphorus-doped porous perovskite LaFeO 3-δ nanosheets were prepared. • Characterizations and DFT results indicate that doping with P induces O v defects. • Perovskite LaFe 1-x P x O 3-δ sensor has excellent acetone sensing properties at 180 °C. • O v defects reconfigure electron distribution and promote gas adsorption. Perovskite-type oxide semiconductors (ABO 3 ) with defective conduction properties have been regarded as highly promising gas-sensitive materials due to their abundant structural types. However, pure ABO 3 gas sensors usually have suboptimal sensing response due to low specific surface area and few adsorption sites. Recently, surface oxygen vacancies (O v ) defects have been shown to be a remarkably effective way to enhance the sensing response of gas sensors by increasing the number of adsorption sites and changing the energy level structure. In view of the above, herein, P-doped perovskite LaFe 1-x P x O 3-δ (x = 0.005, 0.01, 0.03, 0.05) with abundant O v defects were prepared by sol–gel method and fabricated as sensors for the acetone detection. Characterization and test results show that LaFe 0.99 P 0.01 O 3-δ with porous nanosheet structure has excellent acetone gas-sensitive performance. Compared to pure LaFeO 3 gas sensor, the optimal operating temperature of LaFe 0.99 P 0.01 O 3-δ is reduced to 180 °C and response value is improved nearly twofold, whose limit of detection is even at the ppb level. Crucially, the results of electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) verify that the sensing characteristics of the LaFe 1-x P x O 3-δ sensor are strongly correlated with the O v defect. In addition, further theoretical analysis shows that P doping in LaFeO 3 induces O v defects and modulates frontier electron orbital energy levels of the material, thus increasing the chemisorbed oxygen species and enhancing the intermolecular interactions. In this work, the vital function of O v defects in perovskite-type gas sensors is highlighted, which also provides an effective and feasible way to improve the performance of gas sensors.

Conductometric ppb-level acetone gas sensor based on one-pot synthesized Au @Co3O4 core-shell nanoparticles

Detection of acetone is of paramount significance in many fields including self-medical diagnosis, indoor air quality monitoring and other industries. In this study, we assess the acetone sensing capability of novel Au@Co3O4 core-shell nanoparticles (NPs) fabricated using a simple, low temperature (70 °C), in-situ, self-assembly process. The fabricated core-shell nanostructure was sized 70–180 nm, with pomegranate-type morphology and consisted of multi-core Au NPs (5–10 nm in size) inside the Au@Co3O4 core-shell system. P-type Au@Co3O4 core-shell NPs sensor indicated a high response of 27.05–10 ppm acetone at 250 °C. The Au@Co3O4 core-shell NPs sensor also possessed excellent selectivity towards acetone among other interfering gases. The influence of varying levels of relative humidity (RH) on the Au@Co3O4 core-shell NPs were examined, rendering a 60% of response to 2 ppm acetone at 80% RH, and no significant reduction in response at 10–40% RH. The sensor also displayed a low limit of detection (20 ppb), the concentration which is much below the detectable range (1.8 ppm) for a type-I diabetic patient. The Au@Co3O4 core-shell NP sensor developed in this study is considered to open the doors for preparation of other varieties of metal-oxide core-shell systems sensors in a facile approach.

Two-dimensional self-assembled network structure of Co3O4 quantum-dot-decorated ZnO nanobeads for ppb-level acetone sensors

A two-dimensional self-assembled network structure of ZnO nanobeads (NBs) decorated with Co3O4 quantum dots (QDs) was fabricated by an alcohol-assisted Langmuir–Blodgett method for a highly sensitive acetone sensor. Owing to the formation of a p–n junction between the Co3O4 QDs and ZnO NBs and the catalytic activity of Co3O4 QDs for acetone oxidation, the operating temperature of the sensor decreased from 350 to 250 °C, and the response to 1 ppm acetone increased from 5.3 to 7.2. The response was 1.5 even to 40 ppb acetone. Furthermore, the sensor was applied to a commercial breath analyzer, and ppb-levels of acetone were successfully detected in the exhalation of an adult.

Fluoride-assisted highly-active tungsten oxide with modulating exposed facets and defect sites for efficient ppb-level acetone detection

Defect engineering is currently one of the most effective strategies to improve material sensing performance, which always need to be processed under harsh and complicated experimental conditions. Herein, a simple fluoride-assisted hydrothermal method is reported for preparing highly defective and active WO3. The obtained WO3 shows an urchin-like morphology and a mixed crystal structure. The optimized sensor based on the WO3 exhibits a high response, excellent selectivity, and good reproducibility to acetone at 200 °C. More precisely, the response to 0.5 ppm acetone attains 3.3 and the detection limit reaches the ppb-level, showing a potential application in noninvasive diagnosis of diabetes. The unique sensing performance can be attributed to the dominated h-WO3 with preferential exposed (002) facets and the increased structural defects in the synthesized WO3, resulting in an extent of local electric polarization on the surface and an easier and selective chemical adsorption to acetone molecules. The abundant oxygen vacancies act as preferential adsorption sites for absorbing oxygen species that can react with acetone molecules. The sensing mechanism for the unique sensing performance was further proved by a semi-in-situ controlled experiment. It is believed that the present work provides a simple and controllable approach to prepare highly active nanomaterials for application in various fields.

Realization of ppb-level acetone detection using noble metals (Au, Pd, Pt) nanoparticles loaded GO FET sensors with simultaneous back-gate effect

In the current study, graphene oxide (GO), uniformly loaded with different noble metal nanoparticles (Au, Pd and Pt) were synthesized by spray coating technique and implemented in field effect transistor (FET) sensors. The morphology, structure, composition and electronic properties of the synthesized materials were characterized. The sensing results indicated that the incorporation of noble metals can greatly enhance the VOC sensing properties of a few layers of GO by using their chemical and electrical sensitization effect. At optimized gate potential, GO FET exhibited outstanding sensing properties at low operating temperature i.e. 50 °C. Specifically, the FET sensor based on Pd loaded GO exhibited the highest response, quickest response/recovery (37 s/91 s) characteristics, best selectivity and low operating temperature towards low concentration of acetone. Almost five times higher sensitivity towards acetone (400 ppb) was achieved in Pd/GO as compared to the pure GO channel nanoparticles under a suitable back gate bias.

Ultrasensitive acetone gas sensor can distinguish the diabetic state of people and its high performance analysis by first-principles calculation

Detecting the acetone in human exhaled breath sensitively and selectively plays an important role in the noninvasive diagnosis of diabetes. However, obtaining a reliable response to ppb level acetone in exhaled breath directly is still a big challenge. Here, an ultrasensitive acetone gas sensor based on p-Rh2O3-n-ZnO porous heterostructure has been fabricated. The detection limit of the sensor reaches to 50 ppb. The sensor exhibits well repeatability, selectivity and linear response. A good linear relationship between the response and ambient relative humidity is observed. Without removing the water vapor of the exhaled gas, it can distinguish the acetone concentration of the diabetic patients from that of healthy people, implying that the sensor could be used in the diagnosis of diabetes. The synergistic effect of p-Rh2O3-n-ZnO porous heterostructure makes the sensor own ultrasensitive detecting ability towards acetone. Theoretical models have been built by first-principles calculation to reveal the possible reasons for its ultrasensitivity. It should be pointed out that the much lower adsorption energy (− 1.03 eV) of the acetone molecule on Rh2O3 may be the chief cause of the lower detection limit of the sensor.

Highly sensitive and selective sub ppb level acetone sensing platform based on Co3O4–ZnO heterojunction composites

In this work, a three-dimensional fusiform-like Co3O4–ZnO material with different Co3O4 concentrations (0.25, 0.5, 0.75 and 1 at% Co3O4) was successfully synthesized via a simple coprecipitation method. A variety of microscopic characterizations (SEM, XRD, XPS, EDS, HRTEM) were used to observe the microstructure and crystallization of the as-prepared samples. The gas sensing results showed that Co3O4 greatly improved the acetone gas sensing properties of ZnO based gas sensors. And compared with pure ZnO, 0.5 at% Co3O4–ZnO sensing material exhibited the highest response to acetone at an operating temperature of 290 °C; the sensitivity was about 113–100 ppm acetone, with a fast response and recovery time. Also, the sensor based on 0.5 at% Co3O4-ZnO had a low detection limit of 0.5 ppm (response=1.954). The corresponding gas sensing mechanism was discussed in detail.

Preparation and Application of 2D MXene-Based Gas Sensors: A Review

Since MXene (a two-dimensional material) was discovered in 2011, it has been favored in all aspects due to its rich surface functional groups, large specific surface area, high conductivity, large porosity, rich organic bonds, and high hydrophilicity. In this paper, the preparation of MXene is introduced first. HF etching was the first etching method for MXene; however, HF is corrosive, resulting in the development of the in situ HF method (fluoride + HCl). Due to the harmful effects of fluorine terminal on the performance of MXene, a fluorine-free preparation method was developed. The increase in interlayer spacing brought about by adding an intercalator can affect MXene’s performance. The usual preparation methods render MXene inevitably agglomerate and the resulting yields are insufficient. Many new preparation methods were researched in order to solve the problems of agglomeration and yield. Secondly, the application of MXene-based materials in gas sensors was discussed. MXene is often regarded as a flexible gas sensor, and the detection of ppb-level acetone at room temperature was observed for the first time. After the formation of composite materials, the increasing interlayer spacing and the specific surface area increased the number of active sites of gas adsorption and the gas sensitivity performance improved. Moreover, this paper discusses the gas-sensing mechanism of MXene. The gas-sensing mechanism of metallic MXene is affected by the expansion of the lamellae and will be doped with H2O and oxygen during the etching process in order to become a p-type semiconductor. A p-n heterojunction and a Schottky barrier forms due to combinations with other semiconductors; thus, the gas sensitivities of composite materials are regulated and controlled by them. Although there are only several reports on the application of MXene materials to gas sensors, MXene and its composite materials are expected to become materials that can effectively detect gases at room temperature, especially for the detection of NH3 and VOC gas. Finally, the challenges and opportunities of MXene as a gas sensor are discussed.

Pd-Doping-Induced Oxygen Vacancies in One-Dimensional Tungsten Oxide Nanowires for Enhanced Acetone Gas Sensing.

Metal oxide semiconductors (MOS) with different nanostructures have been widely used as gas sensing materials due to the tunable interface structures and properties. However, further improvement of the sensing sensitivity and selectivity is still challenging in this area. Constructing appropriate heterogeneous interface structures and oxygen vacancies is one of the important strategies to tune the sensing properties of MOS. In the present study, interfacial heterostructures in PdxW18O49 nanowires (PdxW18O49 NWs) were fabricated and manipulated by doping different Pd contents through a simple hydrothermal process. Relevant characterization proved that the structure and composition of the one-dimensional (1D) nanomaterial can be effectively changed by Pd doping. It was found that the oxygen vacancy concentration increases first with the increase of Pd content, and when the Pd content increases to 7.18% (Pd7.18%W18O49 NWs), the oxygen vacancy content reaches the maximum (52.5%). If the Pd content continues to increase, the oxygen vacancy ratio decreases. The gas sensing investigations illustrated that the PdxW18O49 NWs exhibited enhanced sensing properties than pure W18O49 NWs toward acetone. Among the as-prepared catalysts, the Pd7.18%W18O49 NWs showed the best sensing response and the fastest response-recovery speeds (5 and 10 s, respectively) at a working temperature of 175 °C. In addition, this 1D nanostructure with fabricated heterostructures also delivers a good sensing selectivity and a wide detection range from 100 ppb to 300 ppm, with maintaining excellent performance in the presence of high concentrations of ethanol and carbon dioxide. The excellent gas sensing behavior could be attributed to the generated oxygen vacancies and the heterostructures upon Pd doping. This study offers a novel strategy for the design of high-performance gas sensors for ppb-level acetone sensing.

Ultra-highly sensitive detection of ppb-level acetone gas using novel multicore-shell porous zinc oxide microspheres

In this study, novel multicore-shell ZnO microspheres were synthesized via a simple solvothermal method based on the coordination of salicylic acid under the protection of polyvinylpyrrolidone (PVP). In this process, as an organic acid, salicylic acid with a benzene ring structure rich in hydroxyl and carboxyl functional groups can not only play a structure-oriented role, but also can etch materials to form a hollow structure. Compared with traditional basic synthesis methods, the diversity of coordination forms makes the structure more abundant. The multicore-shell ZnO was annealed at 450, 600, and 750 °C respectively. Under the driving force of reducing the surface free energy, part of the multi-nucleus inside the microspheres aggregated to form large particles, and the other part adhered to the shell layer to grow. The crystallinity, morphology and surface composition of the ZnO microspheres were characterized by XRD, SEM, TEM, XPS, BET and FT-IR analyses. The multicore-shell ZnO-based sensor that exhibited excellent sensitivity to acetone (2 ppm, SRa/Rg = 8.6) at an optimal working temperature of 240 °C, with a low limit of detection of 100 ppb with a SRa/Rg = 2.9. The annealed ZnO-based sensors also performed well, among them, the product annealed at 750 °C (ZnO-750) is the best, with a response of 6.4 to 2 ppm acetone. The sensors exhibited satisfactory selectivity and can detect acetone in the presence of other interfering gases, including NO, CO, NH3, HCHO, CH3OH and C2H5OH. The outstanding sensitivity of the multicore-shell ZnO sensor to acetone can be attributed to its large specific surface area and pore volume, which favors gas adsorption, penetration and diffusion. For the annealed ZnO, we speculated that the specific exposed crystal plane (002) plays a decisive role in the good adsorption and reaction of acetone.

Metal-organic frameworks derived hierarchical flower-like ZnO/ Co3O4 heterojunctions for ppb-level acetone detection

ABSTRACT The demand of acetone gas sensors with great response value and fast response/recovery time to low concentration acetone is increasing in practical diagnosis for diabetes. In this work, metal-organic frameworks (MOFs) derived flower-like ZnO/Co3O4 heterojunctions based sensor is prepared by a simple solution mixing method at room temperature. The sensor shows high acetone response value, short response/recovery time, excellent selectivity and good stability. For example, the response value of ZnO/Co3O4 heterojunctions based sensor is up to 120 % towards 500 ppb acetone at 300 ℃, which is about 30-fold enhancement than these of intrinsic ZnO and Co3O4. Moreover, its minimal detection limitation is 100 ppb acetone and it shows ultra-fast response/recovery time for ppb-level acetone (22 s/27 s@500 ppb). The excellent acetone sensing properties of flower-like ZnO/Co3O4 heterojunctions based sensor is attributed to the sharp resistance variation of heterojunction interface between ZnO and Co3O4 and the ultra-fast gas transport channel provided by ZnO nanosheets. This finding provides important insights and useful guidance for the detection of ppb-level acetone.