Lower Limit Research Articles

Searching for Neutral Hydrogen Escape from the 120 Myr Old Sub-Neptune HIP94235b using HST

HIP94235 b, a 120 Myr old sub-Neptune, provides us the unique opportunity to study mass loss at a pivotal stage of the system’s evolution: the end of a 100 Myr old phase of intense XUV irradiation. We present two observations of HIP94235 b using the Hubble Space Telescope’s Space Telescope Imaging Spectrograph in the Lyα wavelength region. We do not observe discernible differences across either the blue and red wings of the Lyα line profile in and out of transit, and report no significant detection of outflowing neutral hydrogen around the planet. We constrain the rate of neutral hydrogen escaping HIP94235 b to an upper limit of 1013 gs−1, which remains consistent with energy-limited model predictions of 1011 gs−1. The Lyα nondetection is likely due to the extremely short photoionization timescale of the neutral hydrogen escaping the planet’s atmosphere. This timescale, approximately 15 minutes, is significantly shorter than that of any other planets with STIS observations. Through energy-limited mass loss models, we anticipate that HIP94235 b will transition into a super-Earth within a timescale of 1 Gyr.

Hive-shaped carbon nanotubes coated with MoSe2as an electrochemical sensor for cholesterol.

The study utilized transition metal chalcogenide, molybdenum diselenide (MoSe2), for application in the field of bioelectrochemical sensing. The MoSe2was combined with carbon nanotubes (CNTs) by chemical vapor deposition to enhance the specific surface area and improve the detection sensitivity. To further increase the contact area between the electrolyte and the electrode, photolithography techniques were employed to fabricate hive-shaped CNTs, thereby enhancing the specific surface area. Next, cholesterol oxidase (ChOx) was coated onto the electrode material, creating a cholesterol biosensor. Cyclic voltammetry was utilized to detect the concentration of cholesterol. The experiment involved segmented testing for cholesterol concentrations ranging from 0μM to 10 mM. Excellent sensitivity, low detection limits, and high accuracy were achieved. In the cholesterol concentration range of 0μM-100μM, the experiment achieved the highest sensitivity of 4.44μAμM⋅cm-2. Consequently, all data indicated that ChOx/MoSe2/CNTs functioned as an excellent cholesterol sensor in the study.

Rational Design of A-Site Cation for High Performance Lead-Free Perovskite X-Ray Detectors.

Design of hypotoxic lead-free perovskites, e.g. Bismuth(Bi)-based perovskites, is much beneficial for commercialization of perovskite X-ray detectors due to their strong radiation absorption. Nevertheless, the design principles governing the selection of A-site cations for achieving high-performance X-ray detectors remain elusive. Here, seven molecules (methylamine MA, amine NH3, dimethylbiguanide DGA, phenylethylamine PEA, 4-fluorophenethylamine p-FPEA, 1,3-propanediamine PDA, and 1,4-butanediamine BDA) and calculated their dipole moments and interaction strength with metal halide (BiI3) are selected. The first-principles calculations and related spectroscopy measurements confirm that organic molecules (DGA) with large dipole moments can have strong interactions with perovskite octahedron and improve the carrier transport between the organic and inorganic clusters. Consequently, zero-dimensional single crystal (SC) (DGA)BiI5∙H2O is synthesized. The (DGA)BiI5∙H2O SCs demonstrate an exceptional carrier mobility-lifetime product of 6.55×10-3cm2V-1, resulting in the high sensitivity of 5879.4µCGyair -1cm-2, featuring a low detection limit (4.7nGyairs-1) and remarkable X-ray irradiation stability even after 100 days of aging at a high electric field (100Vmm-1). Furthermore, the (DGA)BiI5∙H2O SCs for imaging, achieving a notable spatial resolution of 5.5lpmm-1 are applied. This investigation establishes a pathway for systematically screening A-site cations to design low-dimensional SCs for high-performance X-ray detection.

Quantum Confinement and End-Sealing Effects for Highly Sensitive and Stable Nitrogen Dioxide Detection: Homogeneous Integration of Ti3C2Tx-Based Flexible Gas Sensors.

The real-time and room-temperature detection of nitrogen dioxide (NO2) holds significant importance for environmental monitoring. However, the performance of NO2 sensors has been hampered by the trade-off between the high sensitivity and stability of conventional sensitive materials. Here, we present a novel fully flexible paper-based gas sensing structure by combining a homogeneous screen-printed titanium carbide (Ti3C2Tx) MXene-based nonmetallic electrode with a MoS2 quantum dots/Ti3C2Tx (MoS2 QDs/Ti3C2Tx) gas-sensing film. These precisely designed gas sensors demonstrate an improved response value (16.3% at 5 ppm) and a low theoretical detection limit of 12.1 ppb toward NO2, which exhibit a remarkable 3.5-fold increase in sensitivity compared to conventional Au interdigital electrodes. The outstanding performance can be attributed to the integration of the quantum confinement effect of MoS2 QDs and the conductivity of Ti3C2Tx, establishing the main active adsorption sites and enhanced charge transport pathways. Furthermore, an end-sealing effect strategy was applied to decorate the defect sites with naturally oxygen-rich tannic acid and conductive polymer, and the formed hydrogen bonding network at the interface effectively mitigated the oxidative degradation of the Ti3C2Tx-based gas sensors. The exceptional stability has been achieved with only a 1.8% decrease in response over 4 weeks. This work highlights the innovative design of high-performance gas sensing materials and homogeneous gas sensor techniques.

Fabrication of Nanobioengineered Interfaces Utilizing Quaternary Nanocomposite for Highly Efficient and Selective Electrochemical Biosensing of Urea.

Nanobioengineered interfaces have gained attention owing to their small size and high surface area-to-volume ratio for utilization as a platform for highly selective and sensitive biosensing applications owing to the integration of biological molecules with engineered nanomaterials/nanocomposites. In this work, a novel Ag-complex, [(PPh3)2Ag(SCOf)]-based quaternary Ag-S-Zn-O nanocomposites (NCs), was synthesized through an environmentally-friendly process. The results revealed the formation of the NCs with an average crystallite size and particle size of 36.08 and 40.22 nm, respectively. In addition, this is the first study to utilize such NCs synthesized via a single-source precursor method, offering enhanced sensor performance due to their unique structural properties. Further, these NCs were used to fabricate a urease (Ur)/Ag-S-Zn-O NCs/ITO nanobioengineered electrode for precise and sensitive electrochemical biosensing of urea. The interfacial kinetic studies revealed quasi-reversible processes with high electron transfer rates and linear current responses, indicating efficient reaction dynamics. A high diffusion coefficient and low surface concentration suggested a fast diffusion-controlled process, affirming the electrode's potential for rapid and sensitive urea detection. The biosensor demonstrated notable sensing properties such as high sensitivity (12.56 μA mM-1 cm-2) and a low detection limit (0.54 mM). The fabricated bioelectrode was highly selective and reproducible and demonstrated stability for up to 60 days. These results validate the potential of this nanobioengineered interface for next-generation biosensing applications, paving the way for advanced point-of-care diagnostics and real-time health monitoring.

A Novel, Selective, and Fast Electrochemical Sensor Based on an 8-Nitroquinoline-Coated Pencil Graphite Electrode for Rutin Determination in Orange Juice

In this study, we developed a facile and low-cost method to prepare a modified electrode by coating the pencil graphite electrode (PGE) surface with 8-nitroquinoline (8-NQ). The surface modification process was carried out by electrochemical reduction of 8-NQ on the PGE surface in ethanol solution. The optimum conditions were determined for the experimental studies. The differential pulse voltammetry was used to determine rutin with the modified electrode (8-NQ/PGE). The developed electrode showed excellent performance for rutin oxidation in a pH 3.0 Britton Robinson buffer (BR). In this media, linearly increasing anodic peak currents were observed with the concentration of rutin in two wide concentration ranges (i.e., 0.016–0.96 μM and 0.96‒19.73 μM), the sensor showed a low detection limit (i.e., 4.14 nM) (3 s m−1). It displayed good stability and selectivity. Also, it was used successfully for the determination of rutin in orange juice samples.

Pd Nanoparticles Loaded on Cu Nanoplate Sensor for Ultrasensitive Detection of Dopamine.

The detection of dopamine is of great significance for human health. Herein, Pd nanoparticles were loaded on Cu nanoplates (Pd/Cu NPTs) by a novel liquid phase reduction method. A novel dopamine (DA) electrochemical sensor based on the Pd NPs/Cu/glass carbon electrode (Pd/Cu NPTs/GCE) was constructed. This sensor showed a wide linear range of 0.047 mM to 1.122 mM and a low limit of detection (LOD) of 0.1045 μM (S/N = 3) for DA. The improved performance of this sensor is attributed to the obtained tiny Pd nanoparticles which increase the catalytic active sites and electrochemical active surface areas (ECSAs). Moreover, the larger surface area of two-dimensional Cu nanoplates can load more Pd nanoparticles, which is another reason to improve performance. The Pd/Cu NPTs/GCE sensor also showed a good reproducibility, stability, and excellent anti-interference ability.

Monte Carlo calculations of cryogenic photodetector readout of scintillating GaAs for dark matter detection

The recent discovery that GaAs(Si,B) is a bright cryogenic scintillator with no apparent afterglow offers new opportunities for detecting rare, low-energy, electronic excitations from interacting dark matter. This paper presents Monte Carlo calculations of the scintillation photon detection efficiencies of optical cavities using three current cryogenic photodetector technologies. In order of photon detection efficiency these are: (1) Ge/TES: germanium absorbers that convert interacting photons to athermal phonons that are readout by transition edge sensors, (2) KID: kinetic induction detectors that respond to the breaking of cooper pairs by a change in resonance frequency, and (3) SNSPD: superconducting nanowire single photon detectors, where a photon briefly transitions a thin wire from superconducting to normal. The detection efficiencies depend strongly on the n-type GaAs absolute absorption coefficient KA, which is a part of the narrow beam absorption that has never been directly measured. However, the high cryogenic scintillation luminosity of GaAs(Si,B) sets an upper limit on KA of 0.03/cm. Using that value and properties published for Ge/TES, KID, and SNSPD photodetectors, this work calculates that those photodetectors attached to opposing faces of a 1 cm3 cubic GaAs(Si,B) crystal in an optical cavity with gold mirrors would have scintillation photon detection efficiencies of 35%, 25%, and 8%, respectively. Larger values would be expected for lower values of KA.

Command filtered‐based fixed‐time fault‐tolerant tracking control for nonlinear systems

AbstractAs for a class of strict‐feedback nonlinear systems with simultaneous sensor and actuator faults, the article focuses on the problem of fixed‐time fault‐tolerant control. Both fixed‐time command filters and a compensation mechanism are utilized to cope with these issues of differential explosion and filter errors. Meanwhile, through the fusion of fixed‐time control, fuzzy logic systems, adaptive control and the backstepping technology, a ‐step design scheme is presented. Our proposed controller ensures the fixed‐time convergence of all the signals in the system even with sensor/actuator faults, and allows the designers to acquire the upper limit value of the fixed convergence time only by tuning the design parameters. And this scheme takes into account rapidity, adaptability and fault tolerance of the system simultaneously. Based on the numerical simulation analysis, it is shown that the better tracking performance can be achieved. So it is concluded that our strategy is effective.

Cardiovascular risk and its influencing factors during exercise in apparently healthy Chinese adult population

BackgroundThere are few studies on the safety of sub-maximal exercise testing of aerobic exercise in apparently healthy Chinese populations. The purpose of this study was to explore the frequency of exercise electrocardiography (ECG) abnormalities and the corresponding exercise intensities, as well as the associated influencing factors, during a symptom-limited stepwise incremental cardiopulmonary exercise test (CPET) in an apparently healthy Chinese population.MethodsA cross-sectional study was done in four communities, one urban and one rural in the North (Beijing) and in the South (Hezhou, Guangxi) of China from 1 January 2017 to 31 December 2018, respectively. Total of 1642 participants was recruited, 918 were eligible and completed demographic indicators, routine blood indicators, physical activity status, symptom-limited CPET and exercise ECG were included in the analysis.ResultsOf the exercise ECG outcomes, 10 (1.1%) were positive and occurred at exercise intensities ≥ 62.50% heart rate reserve (HRR); 44 (4.8%) were equivocal and 864 (94.1%) were normal. Individuals with Cardiovascular Disease Risk Factor (CVDRF) = 3–4 were 2.6 times more likely to have a equivocal and abnormal exercise ECG than those with CVDRF = 0–2. Exercise ECGs of individuals with CVDRF = 5–7 were 5.4 times more likely to be positive and abnormal than exercise ECGs of individuals with CVDRF = 0–2.ConclusionsThe exercise intensity of 62.5% HRR can be used as a safe upper limit for safe participation in exercise in apparently healthy Chinese population; the greater the number of CVDRFs, the greater the likelihood of cardiovascular risk during exercise.

Can millicharge be probed at future Super Tau Charm Facility via mono-π0 searches?

We propose a new channel to search for millicharged particles at the future Super Tau Charm Facility (STCF) via mono-π0 signature. For the first time, we compute the mono-π0 signal events at the future STCF due to millicharged particle production, as well as due to standard model irreducible/reducible backgrounds. By utilizing the assumed 20 ab−1 luminosity for each running energy with s=2 GeV, 4 GeV and 7 GeV, we derive the corresponding upper limits on millicharge, respectively. Via mono-π0 searches at the future STCF with s=2 GeV, the upper limits on millicharge can be improved than ArgoNeuT when the mass of millicharged particle is less than about 500 MeV, but are not very competitive compared to a latest derivation from a past BEBC experiment and a new SENSEI experiment. Regardless, the mono-π0 searches could be an important complement to investigate the invisible particles, such as dark matter.

Research on upper bound limit analysis of slope stability in open-pit mine based on least square principle

So as to extend the application of upper bound limit analysis for slope stability in open-pit mine, this paper analyzed failure mechanism of rock mass when shear failure occured based on plastic mechanics principles, and combined with discrete mathematical theory and least square principle to propose a visualization method of logarithmic spiral. At the same time, the visualization method was applied to engineering practice for slope stability in open-pit mine, and cycle algorithm of stability analysis for open-pit mine slope was proposed through energy balance conditions, then stability analysis results were evaluated reasonably through uniting with limit equilibrium method. The results show that visualization method of logarithmic spiral proposed in this paper is highly consistent with original curve, and can ensure correlation coefficient square is greater than 0.9995. What is more, upper bound limit analysis method has a superhigh accuracy in slope engineering. At the same time, the most dangerous sliding surface obtained by this method can satisfy the requirements of velocity separation, which solved velocity problems during the process of slope evolution. Therefore, the method proposed in this paper has a stronger application in the field of open-pit mining.

Insight of low flammability limit on sustainable aviation fuel blend and prediction by ANN model

Sustainable aviation fuel (SAF) blend has been confirmed to benefit for greenhouse gases reduction, and thus the property of blend fuel should be understanded the detail to support the utilization in aircraft. Low flammability limit (LFL) is a key property of jet fuel which should be sufficiently flammable to burn in combustor of aeroengine and meanwhile should be non-flammable for safety storage in fuel tank of aircraft. LFL of fuel could be influenced by integrating effects including molecule structure, intramolecular chemical bond energy and binding energy of molecule to molecule. Three types of theoretical models, based on different individual view including LFL of every pure hydrocarbon, stoichiometric concentration, and combustion enthalpy, present unsatisfactory simulation results, which can be deduced without integrating all potential influence factors together. The artificial neural network (ANN) approaches have been involved to bridge the relationship of the complex compositions in jet fuels with LFL. For providing adequate and available composition input, the boundary of fuel compositions has been extracted based on constrains of boiling point, flash point and freeze point coupling with statistic petroleum-based jet fuels. By clustering analysis, 43 critical classes of compositions, extracted as surrogate hydrocarbons based on with similar LFL within 1% deviation, have been deployed as input matrix. ANN-LFL model, trained by only drop-in fuel with feature of Sigmoid function as an activation function, can distinguish drop-in fuel with non-drop-in fuel. ANN LFL model can predict LFL of drop-in fuel with 0.988 accuracy. The predict output value of non-drop-in fuel could present obvious deviation with traditional jet fuel. The optimization methodologies of ANN-LFL model could be improved the understanding of LFL and extend ANN in SAF utilization.

JWST NIRSpec Spectroscopy of the Remarkable Bright Galaxy GHZ2/GLASS-z12 at Redshift 12.34

We spectroscopically confirm the M UV = −20.5 mag galaxy GHZ2/GLASS-z12 to be at redshift z = 12.34. The source was selected via NIRCam photometry in GLASS-JWST Early Release Science data, providing the first evidence of a surprising abundance of bright galaxies at z ≳ 10. The NIRSpec PRISM spectrum shows detections of N iv, C iv, He ii, O iii, C iii, O ii, and Ne iii lines and the first detection at high redshift of the O iii Bowen fluorescence line at 3133 Å rest frame. The prominent C iv line with rest-frame equivalent width (EW) ≈ 46 Å puts GHZ2 in the category of extreme C iv emitters. GHZ2 displays UV lines with EWs that are only found in active galactic nuclei (AGNs) or composite objects at low/intermediate redshifts. The UV line-intensity ratios are compatible with both AGNs and star formation in a low-metallicity environment, with the low limit on the [Ne iv]/[N iv] ratio favoring a stellar origin of the ionizing photons. We discuss a possible scenario in which the high ionizing output is due to low-metallicity stars forming in a dense environment. We estimate a metallicity ≲0.1 Z/Z ⊙, a high ionization parameter log U > −2, a N/O abundance 4–5 times the solar value, and a subsolar C/O ratio similar to the recently discovered class of nitrogen-enhanced objects. Considering its abundance patterns and the high stellar mass density (104 M ⊙ pc−2), GHZ2 is an ideal formation site for the progenitors of today's globular clusters. The remarkable brightness of GHZ2 makes it a “Rosetta stone” for understanding the physics of galaxy formation within just 360 Myr after the Big Bang.

The 𝒯ℛ𝒪𝒴 project

Context. Co-orbital objects, also known as trojans, are frequently found in simulations of planetary system formation. In these configurations, a planet shares its orbit with other massive bodies. It is still unclear why there have not been any co-orbitals discovered thus far in exoplanetary systems (exotrojans) or even pairs of planets found in such a 1:1 mean motion resonance. Reconciling observations and theory is an open subject in the field. Aims. The main objective of the 𝒯ℛ𝒪𝒴 project is to conduct an exhaustive search for exotrojans using diverse observational techniques. In this work, we analyze the radial velocity time series informed by transits, focusing the search around low-mass stars. Methods. We employed the α-test method on confirmed planets searching for shifts between spectral and photometric mid-transit times. This technique is sensitive to mass imbalances within the planetary orbit, allowing us to identify non-negligible co-orbital masses. Results. Among the 95 transiting planets examined, we find one robust exotrojan candidate with a significant 3-σ detection. Additionally, 25 exoplanets show compatibility with the presence of exotrojan companions at a 1-σ level, requiring further observations to better constrain their presence. For two of those weak candidates, we find dimmings in their light curves within the predicted Lagrangian region. We established upper limits on the co-orbital masses for either the candidates and null detections. Conclusions. Our analysis reveals that current high-resolution spectrographs effectively rule out co-orbitals more massive than Saturn around low-mass stars. This work points out to dozens of targets that have the potential to better constraint their exotrojan upper mass limit with dedicated radial velocity observations. We also explored the potential of observing the secondary eclipses of the confirmed exoplanets in our sample to enhance the exotrojan search, ultimately leading to a more accurate estimation of the occurrence rate of exotrojans.

Polarization Study of Swift J151857.0–572147 with IXPE Observation

We present an analysis of the Imaging X-ray Polarimetry Explorer observation from a newly discovered transient source: Swift J151857.0–572147. The obtained polarization degree (PD) and angle are 0.3% ± 0.3% and −24° ± 26° respectively in 2–8 keV within 68% confidence level errors, and polarization results are below MDP99 in all energy bins, with the upper limit on PD of 0.8% in the 2–8 keV energy range. No quasi-periodic oscillations (QPOs) are detected in this observation. The polarization and QPO analyses support the hypothesis that the source was in the high soft state, and the results are consistent with predictions for a thin accretion disk model.

A Swift X-Ray View of the SMS4 Sample. II. X-Ray Properties of 17 Bright Radio Sources

Based on a proposal to observe 18 bright radio sources from the SMS4 catalog with the Neil Gehrels Swift Observatory (hereafter Swift), we obtained X-ray observations of 17 targets (one target was not observed). Following up our first paper that discussed 31 sources (see Maselli et al.; 20 sources detected as point sources and one very extended source), we present results for this final sample of 17 radio sources that previously lacked dedicated, pointed narrow-field-of-view (FOV) X-ray observations. One of these 17 sources, undetected by Swift due to a very short exposure, was instead detected by eROSITA, and given in the Data Release 1 (DR1) Catalog. No 1eRASS source was found in the DR1 for the remaining source, unobserved by Swift. The new Swift observations led to 11 X-ray source detections in the 0.3–10 keV band and six upper limits. We investigated the extent of the X-ray emission and the hardness ratio, and when statistics allowed, we carried out a spectral analysis. The X-ray emission of eight sources is consistent with pointlike emission, while three sources show clear evidence of extent, each with peculiar properties. We used the X-ray determined positions and uncertainties of the 12 detected sources to establish associations with infrared and optical sources from the AllWISE and the GSC 2.4.2 catalogs. Requiring a detection in both the infrared and the optical bands to establish a candidate counterpart for our X-ray detections, we identify counterparts for all 12 sources. Following this X-ray-based approach to derive the position of the active nucleus, we are able to confirm the same IR counterparts previously proposed by White et al. for eight sources, and provide four new IR candidates. In the optical, we identify counterparts that match the candidates previously given by Burgess & Hunstead for all sources. We discuss the interesting structure of MRC B0344−345 and PKS B2148−555, two of the six extended X-ray sources that we detected in both our Swift campaigns, and suggest they are very promising for further X-ray and radio investigations. For the 38 SMS4 sources that lack pointed, narrow-FOV X-ray telescope observations, after our Swift campaigns, we list 18 likely counterparts from the eROSITA DR1 catalog.

A heat-measurement-free strategy for Economic Model Predictive Control of hydronic radiators

Cost-efficient measurement of room-level heat output from hydronic radiators is a major barrier to large-scale implementation of Economic Model Predictive Control (EMPC) in residential space heating for demand-side management. This paper therefore presents a novel EMPC strategy for hydronic radiators that relies on measurements of radiator pipe temperatures as a proxy for the radiator heat output, thus eliminating the need for costly flow-based meters at each radiator in a building. Simulation-based experiments indicate that the proposed proxy-based EMPC matches the performance of its heat-based counterpart. The proxy-based EMPC achieved a 16.6 % cost reduction compared to the heat-based EMPC's 16.8 %, with no comfort violations in both cases. Furthermore, the strategy shows resilience towards uncertainties in the user-estimated radiator exponent and maximum heating capacity. The proposed EMPC scheme also allows system operators to fine-tune the balance between cost savings and return temperatures using the proxy's upper limit. The findings presented in this paper suggest that the proposed proxy-based EMPC scheme provides a practical pathway for broader applications of EMPC in hydronic-based space heating with the prospect of unlocking significant load shifting potential, cost savings for end-users, and enhanced efficiency in individual and collective energy systems.

Molecular Oxygen Abundance in Galactic Massive Star Formation Regions Based on SWAS Observations

Molecular oxygen abundance is a key parameter in understanding the chemical network of the interstellar medium. We estimate the molecular oxygen column density and abundance for a sample of Galactic massive star formation regions based on observations from the Submillimiter Wave Astronomy Satellite (SWAS) survey. We obtained an averaged O2 spectrum based on this sample using the (SWAS) survey data (O2, 487.249 GHz, N = 3–1, J = 3–2). No emission or absorption feature is seen around the supposed central velocity with a total integration time of t total = 8.67 × 103 hr and an rms noise per channel of 1.45 mK. Assuming a kinetic temperature T kin = 30 K, we derive the 3σ upper limit of the O2 column density to be 3.3 × 1015 cm−2, close to the lowest values reported in Galactic massive star formation regions in previous studies. The corresponding O2 abundance upper limit is 6.7 × 10−8, lower than all previous results based on SWAS observations and is close to the lowest reported value in massive star formation regions. On a galactic scale, our statistical results confirm a generally low O2 abundance for Galactic massive star formation regions. This abundance is also lower than results reported in extragalactic sources.

Ir doping improved oxygen activation of WO3 for boosting acetone sensing performance at low working temperature

Thermally excited oxygen activation is the key to realize gas sensing by semiconductor. However, the relevant strategies and mechanisms are rarely studied. Herewith, the model material of highly oxygen catalytic active Ir doped WO3 (Ir-WO3) is prepared to elucidate the impact of enhanced oxygen activation on sensing performance. Interestingly, the 0.5 wt% Ir doped WO3 successfully reduced the working temperature of WO3 from 370 to 260 ℃ and significantly enhanced the response from 25.1 to 127.9 (at 50 ppm) for acetone. Meanwhile, the sensor also has fast response/recovery times (∼8.3/3.8 s), long-term stability, low detection limit (19 ppb) and high selectivity. Gas sensitive performance tests, in situ-DRIFTS and DFT calculations reveal that the Ir doping facilitates the oxygen adsorption and activation, which can significantly weaken the activation energy of acetone at low temperatures and contribute to enhance sensing performance. Our work paves a new pathway to improving metal oxide-based gas sensors at lower operating temperatures.