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Transition metal dichalcogenides (TMDs) have attracted significant interest as gas‐sensing materials due to their unique crystal structure and surface. However, there are still issues when it comes to expanding the types of sensing gases for the TMD gas sensors. To extend gas‐sensing selectivity for the TMD gas sensors in this study, a monolayer (ML) 2D metal–organic framework (MOF) is introduced on top of the PtSe2 gas sensor, thereby tuning the major sensing analyte of PtSe2 from NO2 to H2S. Density functional theory calculations elucidate that the metal species of ML MOFs are attributed to the tuned selectivity of the analytes, based on the difference in binding energies. It is also demonstrated that ML MOF maintained the high responsivity of the pristine PtSe2 even at a low concentration of gas (200 ppb). This is further confirmed through the molecular dynamics simulations, which reveal that the ML feature of the ML MOF is highly essential to preserve the intrinsic ultra‐low limit detection properties of pristine PtSe2. [ABSTRACT FROM AUTHOR]

Activation of metal oxides by light is a robust yet facile approach to manipulating their surface chemistry for favorable reactions with target molecules in heterogeneous catalysis and gas sensors. However, a limited understanding of interface chemistry and the involved mechanism impedes the development of a rational design of oxide interfaces for light‐activated gas sensing. Herein, the TiOx‐assisted photosensitization of In2O3 toward NO2 sensing is investigated as a case study to elucidate the detailed mechanism of light‐activated surface chemistry at the metal/gas interface. The resultant heterogeneous oxides exhibit outstanding NO2 sensing performance under light irradiation thanks to abundant photoexcited electrons and holes that serve as adsorption and desorption sites, respectively, to accelerate both surface reactions. Furthermore, the facile transfer of electrons and holes across the TiOx‐In2O3 interface contributes to improving the reversibility of sensing kinetics. Through this study, the mechanistic understanding is established of how the surface chemistry of metal oxide surfaces can be tuned by light activation providing an effective route to the design fabrication of high‐performance gas sensors. [ABSTRACT FROM AUTHOR]

Flexible and mechanically robust gas sensors are the key technologies for wearable and implantable electronics. Herein, the authors demonstrate the high-performance, flexible nitrogen dioxide (NO2) chemiresistors using a series of n-type conjugated polymers (CPs: PNDIT2/IM-x) and a polymer dopant (poly(ethyleneimine), PEI). Imine double bonds (C = N) are incorporated into the backbones of the CPs with different imine contents (x) to facilitate strong and selective interactions with NO2. The PEI provides doping stability, enhanced electrical conductivity, and flexibility. As a result, the NO2 sensors with PNDIT2/IM-0.1 and PEI (1:1 by weight ratio) exhibit outstanding sensing performances, such as excellent sensitivity (𝚫R/Rb = 240%@1 ppm), ultralow detection limit (0.1 ppm), high selectivity (𝚫R/Rb < 8%@1 ppm of interfering analytes), and high stability, thereby outperforming other state-of-the-art CP-based chemiresistors. Furthermore, the thin film of PNDIT2/IM-0.1 and PEI blend is stretchable and mechanically robust, providing excellent flexibility to the NO2 sensors. Our study contributes to the rational design of high-performance flexible gas sensors. [ABSTRACT FROM AUTHOR]

Abstract: Edges of 2D transition metal dichalcogenides (TMDs) are well known as highly reactive sites, thus researchers have attempted to maximize the edge site density of 2D TMDs. In this work, metal‐organic framework (MOF) templates are introduced to synthesize few‐layered WS2 nanoplates (a lateral dimension of ≈10 nm) confined in Co, N‐doped hollow carbon nanocages (WS2_Co‐N‐HCNCs), for highly sensitive NO2 gas sensors. WS2 precursors are assembled in the surface cavity of Co‐based zeolite imidazole framework (ZIF‐67) and subsequent pyrolysis produced WS2_Co‐N‐HCNCs. During the pyrolysis, the carbonized ZIF‐67 are doped by Co and N elements, and the growth of WS2 is effectively suppressed, creating few‐layered WS2 nanoplates functionalized Co‐N‐HCNCs. The WS2_Co‐N‐HCNCs exhibit outstanding NO2 sensing characteristics at room temperature, in terms of response (48.2% to 5 ppm), selectivity, response and recovery speed, and detection limit (100 ppb). These results are attributed to the enhanced adsorption and desorption kinetics of NO2 on abundant WS2 edges, confined in the gas permeable HCNCs. This work opens up an efficient way for the facile synthesis of edge abundant few‐layered TMDs combined with porous carbon matrix via MOF templating route, for applications relying on highly active sites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of atomically thin 2D metal oxide NSs by a chemical exfoliation process. • A comparative study on the humidity sensing performances of 2D Ru oxide and Mn oxide NSs. • Demonstration of real-time breath humidity monitoring using a wearable sensing module. Collecting real-time breath humidity data is important for calibrating gas sensors from interfering signals in breath components, ultimately for accurately monitoring a patient's physiological information for applications in non-invasive and point-of-care diagnostics. In this work, atomically thin 2D metal oxide nanosheets (NSs) were synthesized by a liquid phase exfoliation process and their humidity sensing properties were investigated. Interestingly, Opposite humidity sensing responses (R D /R H) were observed between semiconducting oxide and metallic oxide NSs. For the semiconducting manganese (Mn) oxide NSs, decreasing resistance transitions were obtained with the response of 24.01 at 44.5% RH at low humidity levels (i.e., 6.1–45% RH), which was governed by proton (H+) conduction. On the other hand, the metallic ruthenium (Ru) oxide NSs exhibited increasing resistance transitions with the response of 0.28 at 96.3% RH at a high humidity range (i.e., 50–99.9% RH) as a result of proton trapping by accepting electrons upon the exposure to excess water molecules. Ru oxide NSs exhibited the response and recovery times of 68 sec and 8 sec, respectively, at 96.3% RH. Real-time breath humidity monitoring is demonstrated by integrating Ru oxide NSs with a wristband-type wireless sensing module, which can transmit the sensing data to a mobile device. [ABSTRACT FROM AUTHOR]

Abstract: Three different compositions of ZnO–In2O3 composite nanofibers were prepared by electrospinning, and their gas sensing characteristics were compared to those of pure ZnO and In2O3 nanofibers. All ZnO–In2O3 composite nanofibers showed high response to trimethylamine (TMA), relatively low cross-response to C2H5OH, and negligible cross-responses to CO and H2; pure ZnO or In2O3 nanofibers did not show selective detection of TMA. The maximum responses to 5ppm TMA of the ZnO–In2O3 composite nanofibers with the compositions of [Zn]:[In]=67:33, 50:50, and 33:67 by at% were 133.9 at 300°C, 82.9 at 350°C, and 119.4 at 375°C, respectively. Considering all the sensing characteristics such as gas response, selectivity, and sensing/recovering kinetics together, the operation of the ZnO–In2O3 nanofiber sensor with the composition of [Zn]:[In]=33:67 by at% at 375°C was determined to be in optimal condition to detect TMA. The significant enhancement of gas response and selectivity by the formation of composite nanofibers is discussed in relation to the variation of particle size, the formation of hetero-interfaces between ZnO and In2O3, and the combination of two sensing materials with different catalytic properties, gas adsorption behaviors, and acid–base properties. [Copyright &y& Elsevier]

Abstract: Gas sensors are employed in many applications including detection of toxic and combustible gases, monitoring emissions from vehicles and other combustion processes, breath analysis for medical diagnosis, and quality control in the chemicals, food and cosmetics industries. Many of these applications employ miniaturized solid-state devices, whose electrical properties change in response to the introduction of chemical analytes into the surrounding gas phase. Key challenges remain as to how to optimize sensor sensitivity, selectivity, speed of response and stability. The principles of operation of such devices vary and a brief review of operating principles based on potentiometric/amperometric, chemisorptive, redox, field effect and nanobalance approaches is presented. Due to simplicity of design and ability to stand up to harsh environments, metal oxide-based chemoresistive devices are commonly selected for these purposes and are therefore the focus of this review. While many studies have been published on the operation of such devices, an understanding of the underlying physicochemical principles behind their operation have trailed behind their technological development. In this article, a detailed review is provided which serves to update progress made along these lines. The introduction of nanodimensioned materials has had a particularly striking impact on the field over the past decade. Advances in materials processing has enabled the fabrication of tailored structures and morphologies offering, at times, orders of magnitude improvements in sensitivity, while high-resolution analytical methods have enabled a much improved examination of the structure and chemistry of these materials. Selected examples, illustrating the type of nanostructured devices being fabricated and tested, are discussed. This review concludes by highlighting trends suggesting directions for future progress. [Copyright &y& Elsevier]

Abstract: One-dimensional (1D) amorphous InGaZnO4 (a-IGZO) submicron-tubes were synthesized in a method involving an electrospun polymeric fiber template and the direct RF-sputter-coating of a-IGZO films combined with subsequent calcination at 450°C. The a-IGZO hollow fibers with a diameter of 300nm and a shell thickness of 20–30nm showed an amorphous structure, as confirmed by XRD and HR-TEM analyses. Gas sensors using semiconducting a-IGZO tube networks exhibited n-type gas sensing characteristics and a 3.7-fold higher gas response (R gas /R air =109.5 at 2ppm NO2) compared to (R gas /R air =29.4) planar a-IGZO thin films at an operating temperature of 300°C. The enhanced gas response of a-IGZO tubes is attributed to the greater space charge modulation depth associated with the thin shell structures and the porous networks which are readily accessible by gas. [Copyright &y& Elsevier]

Microstructural evolution of spinel Zn2SnO4nanofibers was manipulated viaan in situphase separation process of inorganic precursors and a matrix polymer during electrospinning and calcination. Chemiresistive gas sensors using porous Zn2SnO4fibers exhibited superior C2H5OH sensing response. [ABSTRACT FROM AUTHOR]

Close packed arrays of hollow SnO2hemispheres were prepared using PMMA microspheres as sacrificial templates for subsequent sputter-deposition of SnO2films, leading to a threefold enhancement in gas sensitivity compared to non-templated (flat) films. [ABSTRACT FROM AUTHOR]

A NO2 sensor based on optically sintered 2D Ru oxide nanosheets applied to a flexible heating substrate composed of a colorless polyimide film with embedded Ag nanowires is described by Hee Jung Park, Il‐Doo Kim, and co‐workers in article number 1606026. A sensitivity of 1.124% at 20 ppm and a wearable wireless sensor is demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrodeposition and electropolymerization have emerged as versatile tools for the fabrication of chemical and biosensors. The literature in this area, published since 2017, is the main focus of this review. Electropolymerization has played a particularly prominent role in sensor development since its discovery in 1980 by Diaz at IBM. The ability to entrain receptors such as antibodies, engineered virus particles, and metal chelating agents into a conductive polymer sensing element during electropolymerization has proven to be a powerful means of preparing chemiresistors for a variety of analyses. Electrodeposition has also been used to prepare nanostructured metal indicator microelectrodes, enabling of a new modality for transducing biosensors. Electrodeposited metal nanowires have formed the basis for rapid and sensitive sensors for hydrogen gas. Electrodeposition has also been exploited as a powerful means for amplifying weak biosensor signals, extending their dynamic range. Opportunities for the application of electrodeposition and electropolymerization for chemical and biological sensor fabrication and function are discussed. [ABSTRACT FROM AUTHOR]

Highly selective and sensitive detection of trimethylamine (TMA) was achieved by the decoration of discrete p-type Cr2O3 nanoparticles on n-type ZnO nanowire (NW) networks. Semielliptical Cr2O3 nanoparticles with lateral widths of 3–8 nm were deposited on ZnO NWs by the thermal evaporation of CrCl2 at 630 °C, while a continuous Cr2O3 shell layer with a thickness of 30–40 nm was uniformly coated on ZnO NWs at 670 °C. The response (Ra/Rg: Ra, resistance in air; Rg, resistance in gas) to 5 ppm TMA of Cr2O3-decorated ZnO NWs was 17.8 at 400 °C, which was 2.4 times higher than that to 5 ppm C2H5OH and 4.3–8.4 times higher than those to 5 ppm p-xylene, NH3, benzene, C3H8, toluene, CO, and H2. In contrast, both pristine ZnO and ZnO (core)–Cr2O3 (shell) nanocables (NCs) showed comparable responses to the different gases. The highly selective and sensitive detection of TMA that was achieved by the deposition of semielliptical Cr2O3 nanoparticles on ZnO NW networks was explained by the catalytic effect of Cr2O3 and the extension of the electron depletion layer via the formation of p–n junctions. [ABSTRACT FROM AUTHOR]

In this work, a novel catalytic synthesis and functionalization method using apoferritin is used to fabricate RuO 2 nanoparticles (NPs) loaded WO 3 nanofibers (NFs) for potential diagnosis of diabetes. Catalytic ruthenium (Ru) NPs with very small average diameters of 1.8 ± 0.9 nm were synthesized using apoferritin which is a hollow protein cage, and were easily functionalized on WO 3 NFs by introducing electrospinning solution with W precursor and polyvinylpyrrolidone (PVP). As-spun Ru NPs-loaded W precursor/PVP composite NFs were calcined at 600 °C for 1 h in air atmosphere to achieve RuO 2 -functionalized WO 3 NFs. The small size and uniform distribution of catalytic RuO 2 NPs were well maintained due to hollow nature of apoferritin cages after calcination. The chemo-resistive sensors using RuO 2 -functionalized WO 3 NFs showed significantly enhanced acetone (CH 3 COCH 3 ) sensing response (R air /R gas = 78.61–5 ppm), which was 7.4 times higher than the response (R air /R gas = 10.61–5 ppm) of pristine WO 3 NFs at highly humid atmosphere (95% RH). In addition, the RuO 2 -functionalized WO 3 NFs showed outstanding selectivity toward acetone gas in comparison with other gases such as hydrogen sulfide (H 2 S), toluene (C 6 H 5 CH 3 ), ethanol (C 2 H 5 OH), pentane (C 5 H 12 ), ammonia (NH 3 ), hydrogen (H 2 ), and water vapor (H 2 O) at 5 ppm. These results represent potential feasibility for the detection of acetone in exhaled breath for diagnosis of diabetes. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2D-MOF is connected to 3D-MOF with coordination bond to form Ni-HHTP@UiO-66NH 2. • 2D-MOF@3D-MOF affords porosity, conductivity, and active interface for sensing. • Ni-HHTP@UiO-66NH 2 shows superior sensitivity and low detection limit toward H 2 S. • A plausible mechanism is proposed from the joint experimental/computational data. Research to develop ideal sensing devices for toxic gases is on the rise, and amongst various materials, metal–organic frameworks (MOFs) have opened up promising vistas as chemiresistive sensors due to their high structural and functional tunability. Here, we report the composites of dimensionally (2D and 3D) and functionally (conductive and porous) different two MOFs in the form of a well-integrated core–shell structure. The hierarchically assembled 2D-MOF@3D-MOF exhibits new interfacial properties that are responsible for synergetically enhanced sensing performances toward toxic H 2 S gas with the lowest recorded limit of detection (1.4 ppb), superior sensitivity (ΔR/R 0 = 3.37), and outstanding selectivity at room temperature in air. The sensing mechanisms are proposed by combinational studies of experiments and calculation, which indicates that multiple changes (e.g., local structural change of the shell MOF, secondary binding sites generation from the core MOF, and free radicals formation) play a critical role in achieving synergetic chemiresistive sensing. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple but powerful solution to overcome the chronic bottleneck of the nanocatalyst delivery on oxide support: the carbothermal shock driven nanocatalyst formation on carbon nanofibers (CNFs) with small sizes and fine distribution can be delivered to oxide structures of choice while retaining high uniformity. • Fabrication of catalyst delivered porous oxide structures: the asymmetric sputtering of oxide on CNFs can induce the formation of openly porous hemi-tubular structures with tunable porosity and thickness. A simple subsequent calcination results in the transfer of catalysts from the CNF template to the porous oxide structures. • Superior hydrogen sulfide sensing properties: Uniform distribution of Pt nanoparticles on SnO 2 hemitubes showed superior H 2 S sensing performances (Response Rair/Rgas > 1500 at 5 ppm H 2 S) compared to state-of-the-art H 2 S sensors. To achieve powerful gas sensors oxide semiconductor chemiresistors, the uniform functionalization of nanocatalysts on the desired metal oxides is considered as a key strategy. However, still, it is challenging to achieve the nanocatalysts decoration on desired oxides without deterioration of target materials. In this study, thermal-shock (rapid joule-heating method) was applied to uniformly decorate Pt nanoparticles (NPs) on the surface of carbon nanofibers (CNFs) to achieve the uniform distribution of Pt NPs on one-dimensional structures. And then, SnO 2 was physically deposited on the Pt NPs loaded CNFs and continuous heat-treatment was conducted to transfer the Pt NPs to desired SnO 2 porous hemitubes. Thanks to the well-distributed Pt NPs on porous SnO 2 hollow structures, the Pt laoded SnO 2 hemitubes showed an exceptional sensitivity (R air /R gas = 1500 at 5 ppm) in H 2 S. Also, it showed high selectivity for H 2 S and high stability even under continuous gas exposure, confirming its potential as an effective H 2 S sensor. [ABSTRACT FROM AUTHOR]

We report on facile synthesis of SnO2 nanofibers (NFs) functionalized by Pt nanoparticles (NPs) with various loading contents (0.05–0.4wt%) and their gas response toward H2, NO2, NH3, CO, and SO2 gases as a function of the operation temperature (100–450°C) and gas concentration (0.125–2.5ppm). Mesoporous SnO2 NFs with large surface-to-volume ratio, which facilitates sensitive gas response, were synthesized by electrospinning followed by subsequent calcination at 500°C for 2h. Colloidal Pt NPs synthesized by simple polyol method were immobilized on SnO2 NFs as a catalytic sensitizer to H2 oxidation. The gas sensing properties and response kinetics were significantly affected by the Pt NPs and the operation temperature. It was found that 0.1wt% Pt-loaded SnO2 sensor showed the highest H2 response (I gas/I air =16.6 at 2.5ppm) at 300°C. A remarkably high NO2 response (I air/I gas =57.0 at 2.5ppm) was achieved in the case of pristine SnO2 sensor at 150°C. This work demonstrates that sensitive and selective detection of H2 and NO2 gases with negligible cross-response to interfering gases such as NH3, CO, and SO2 can be obtained by decoration with Pt NPs on metal oxide NFs in conjunction with manipulation of the operation temperature. [ABSTRACT FROM AUTHOR]

Abstract: The response characteristics of amorphous-InGaZnO4 (a-IGZO4) thin films toward reducing/oxidizing gases (H2/NO2), at sensor operating temperatures, are reported for the first time. The lack of grain boundaries eliminates a major source of electrical, microstructural and chemical inhomogeneities associated with polycrystalline semiconducting metal oxides (SMOs), rendering a-IGZO4 a highly promising model sensor system. Gas sensor tests were carried out in the temperature range of 200–400°C by monitoring changes in DC resistance during cyclic exposure to trace concentrations (between 1.25 and 50ppm) of H2 or NO2 in dry air. The response (S) to H2 was found to go through a temperature maximum (e.g. S ∼0.7 at 350°C for pH2 =12.5ppm) that value being a function of pH2. The response to NO2, on the other hand, decreased with increasing temperatures with the highest recorded values at 200°C (e.g. S ∼33 at 200°C for pNO2 =5ppm). The response followed an approximate power law dependence on gas partial pressure (p), S = Ap β , with β taking on values of ∼0.5–1.0 as temperature increased from 200 to 400°C. Response times were found to range from 10s to greater than 1000s as temperature decreased. The hysteretic behavior exhibited by a-IGZO films between 150 and 400°C, under temperature sweep conditions, is attributed to kinetically limited adsorption/desorption and reaction rates. [Copyright &y& Elsevier]

Abstract: SnO2 hollow nanofibers (HNFs) with diameters of 300–500nm were fabricated via electrospinning of templating nanofibers and RF-sputtering of SnO2 thin overlayers (15–20nm thick and comparable grain size) followed by heat-treatment at 450°C. Gas sensors using these HNFs exhibited n-type gas sensing characteristics and an enhanced gas response to 2ppm NO2 (R gas /R air =81.4) as compared to that (R gas /R air =19.9) of planar SnO2 thin films. The enhanced response to NO2 is attributed to the greater accessible active area and the greater space charge modulation depth associated with the hollow thin walled structures. [Copyright &y& Elsevier]

Abstract: This work presents a simple and versatile route to produce macroporous p-type metal oxide thin films. Two-dimensional arrays of p-type NiO films with a hollow hemisphere structure were fabricated by colloidal templating and RF-sputtering followed by a subsequent heat treatment. The diameter and shell thickness of the NiO hemisphere were 800nm and 20nm, respectively. X-ray diffraction and high-resolution transmission electron microscopy analysis indicate that the pure NiO phase with grain size of 10nm was obtained at calcination temperatures that exceeded 450°C. Close-packed arrays of hollow NiO hemispheres were found to exhibit p-type gas sensing properties against (CO, H2, C3H8, CH4, NO2, and C2H5OH), leading to significantly enhanced responses to C2H5OH (R gas /R air =5.0 at 200ppm). [Copyright &y& Elsevier]

Abstract: This work presents a new route to enhance the sensitivity of nanocrystalline TiO2 fibers based gas sensors. Pure and Pd-doped TiO2 nanofiber mats were synthesized by electrospinning and subsequent calcination. Highly porous fibrillar morphology was observed in the resultant nanocrystalline TiO2 fibers. In addition to anatase TiO2 crystallites, tiny (∼2nm) PdO crystallites were observed in the Pd-doped TiO2 fibers. The sensors using Pd-doped TiO2 fibers showed promising gas sensing characteristics, such as low operation temperature (180°C) and sufficient gas response (R/R o =38 to 2.1ppm NO2). The techniques outlined here offer new means for preparing novel metal-oxide nanofibers with catalytic dopants. [ABSTRACT FROM AUTHOR]

Abstract: To enhance the sensitivity of a metal oxide-based gas sensor, we introduce a novel electrical method that relies jointly on the use of impedance and an applied DC bias. We used polycrystalline ZnO–NiO composite thin films prepared by pulsed layer deposition as CO gas sensor material. The applied DC bias lowers the interface barrier between oxide grains and thereby enhances the sensitivity. Our approach enhances the sensitivity to CO gas by approximately 200% more than a conventional DC method. The enhancement effect is more pronounced when the CO concentration is lowered. This method offers an efficient characterization tool for modulating the sensitivity of gas sensors using semiconducting metal oxides. [Copyright &y& Elsevier]

• The non-noble metals are introduced on graphene-based fiber as a sensitizer for the high-performance chemiresistor. • Metal oxides on graphene fibers naturally are converted into metals at a relatively low temperature annealing (under 700 °C) due to catalytic effect of graphene. • The graphene fiber acts as a flexible conductive support as well as a catalyst for the deoxidation of metal oxide. • The metal/metal oxide/graphene fibers exhibited a 16 times higher response to NO 2 gas and recovery than metal oxide/graphene fiber without metal. • The proposed strategy opens a new avenue for the realization of high-performance devices, such as chemical catalysts, photoactive devices. [Display omitted] Noble metal/metal-oxide-based hybrid gas sensors exhibit a low operating temperature, remarkable sensitivity, and fast recovery. As additives, noble metals induce a catalytic sensitization effect, which promotes charge transfer from the metal oxide to the analyte molecules, the so-called spillover mechanism. This suggests that metal catalysts can improve gas sensing performance. Herein, for the first time, non-noble metals are introduced on hybrid metal oxide/graphene fibers as sensitizers to fabricate high-performance chemiresistive sensors. The formation of metal components can be effectively controlled by annealing the metal oxide on graphene. Remarkably, compared with the corresponding metal oxide/graphene fiber sensors without metal components, the metal/metal oxide/graphene fiber sensors exhibit over a 16-fold higher response to NO 2 gas as well as effective recovery characteristics. Specifically, the Cu/Cu 2 O/graphene and Ni/NiO/graphene fiber sensors operating at 150 °C exhibit sensitivities of 18.90 % and 0.82 %, respectively, for 5 ppm NO 2 gas. The proposed strategy to achieve flexible graphene fiber chemiresistors by decorating them with non-noble metal and metal oxide nanoparticles opens a new avenue for realizing high-performance devices, such as photovoltaic devices, photocatalysts, and chemical catalysts. [ABSTRACT FROM AUTHOR]

• Porosity control of nanofibers: The high porosity of the metal oxide nanofibers is the key to achieving the dual sensitization owing to their high gas permeability and numerous active sites. Both saponin and water-ethanol co-solvent play critical roles in modifying morphology of nanofibers into elliptical nanofibers during electrospinning. Additionally, saponin forms numerous pores in the nanofibers when being burnt out during calcination. These porous, elliptical nanofibers possess a larger surface area and porosity.Saponin and water-ethanol co-solvent enabled porous, elliptical nanofibers to emerge. • Bifunctional Ga doping: Ga dopants enhanced sensing performance via conductivity improvement and grain growth inhibition. • Functionalization of Pt catalysts : Spill-over effects and chemical sensitization of remarkably improved C 2 H 2 sensitivity. Herein, we demonstrate a sensitization strategy via solid-solution doping and catalytic metal nanoparticles (NPs) onto porous metal oxide nanofibers (NFs) for superior acetylene (C 2 H 2) sensing capabilities. The introduction of dopants and catalysts not only increases the inherent reactivity of metal oxides, but also induces the spillover of C 2 H 2 onto metal oxides, significantly improving the sensing properties. We elucidate that the high porosity of the metal oxide NFs, prepared by electrospinning and utilizing saponin as a sacrificial template, is the key to achieving high gas permeability and numerous active sites. Consequently, Ga-doped ZnO porous NFs functionalized with Pt catalysts exhibited the highest C 2 H 2 sensing responses among the current state-of-the-art C 2 H 2 sensors (R a /R g = 26.2 at 400 °C) with a fast response time (10.2 s), at a particularly low concentration of 5 ppm. Moreover, these NFs showed excellent selectivity against the interfering gas (H 2 , C 7 H 8 , CO, CH 4 , C 8 H 10 , CH 3 COCH 3 , HCHO and C 2 H 5 OH) and outstanding stability up to 20 sensing cycles to 0.4 ppm of C 2 H 2. These results provide an efficient strategy to tailor composites of metal oxide nanostructures, dopants, and catalysts for highly sensitive gas sensors. [ABSTRACT FROM AUTHOR]