Gd-modified In2O3 for the enhanced xylene sensing

Gd-modified In2O3 for the enhanced xylene sensing | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Gd-modified In 2 O 3 for the enhanced xylene sensing Zhengxin ZHANG, Deqi ZHANG, Li YANG, Ming HOU, Jiyun GAO, Yi XIA, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3795548/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 12 Mar, 2024 Read the published version in Journal of Porous Materials → Version 1 posted You are reading this latest preprint version Abstract Modifying with rare earth elements has been proven to be an effective means of enhancing the gas-sensing properties of oxides. In this work,Gd-In 2 O 3 based sensor was developed, which showed high response to 100 ppm xylene gas (Ra/Rg = 17.8) fast response time (11 s) at 350°C, this response value was 5.4 times higher compared to the unmodified In 2 O 3 sensor (Ra/Rg = 3.3). The introduction of the rare earth element not only improves the electrical properties of the sensitive material to provide a more suitable resistance, but also strengthens the gas adsorption ability and the catalytic effect on the surface of the sensitive material, leading to the enhanced sensing performance. rare earth elements In2O3 gas sensor xylene Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction The effects of volatile organic compounds (VOCs) air pollutants on indoor and outdoor environments deserve special consideration because of their ability to damage human health and the environment which have become a primary worldwide concern for various scientific communities[ 1 , 2 ]. Among these VOC pollutants, BTEX (benzene, toluene, ethylbenzene, and xylenes), a subclass of VOCs, is inherently highly toxic and carcinogenic[ 3 , 4 ],which can severely damage the liver, kidneys, spleen, and stomach[ 5 – 8 ].BTEX is typically present in everyday essentials such as thinners, degreasers, detergents, lubricants, and liquid fuels[ 5 , 6 ]. Therefore, it is very necessary to develop gas sensor for effective BETX detection. In 2 O 3 , a typical n-type semiconductor, has been widely used to detect hazardous gases because of its wide band gap, fast saturation electron migration, and low resistivity[ 11 , 12 ]. When volatile organic compound (VOC) molecules stick to the surface of In 2 O 3 , it not only impacts the electron concentration on the surface of indium oxide, which affects its conductivity, but also alters the electronic state of the surface of indium oxide, which subsequently affects its electrical resistivity properties. However, the original In 2 O 3 still has problems with high energy consumption and poor selectivity, which cannot meet the current increasingly high environmental monitoring requirements. In 2 O 3 can be modified with noble metal elements,building heterojunction structures or modifying its surface to enhance the gas-sensitive response. But noble metal modification of In 2 O 3 is relatively expensive, and the high electrical resistance due to the heterostructure can lead to electrical noise that hinders the use of portable devices.[ 13 ]. Rare earth materials, known as "industrial vitamins", have been widely used as surface modifiers due to their high electrical conductivity, magnetic, electrochemical, and luminescent properties based on 4f electron leaps. [ 14 – 19 ]. Zhang et al[ 20 ] reported that the addition of Yb significantly improved the gas-sensitive performance of In 2 O 3 on formaldehyde. Hong et al[ 21 ] reported that 3 mol% Pr-doped In 2 O 3 nanoparticle-based sensors showed good sensing performance on xylene. Thus it can be seen that surface modification is an effective and straightforward way to improve gas sensing performance.However, most reported xylene gas sensors still suffer from slow response rates and poor reversibility. Herein, Gd-modified In 2 O 3 was successfully obtained via physical vapor deposition method and used to detect xylene. With the introdution of Gd, the In 2 O 3 based sensor exhibited improved electrical property and catalytic effect, leading to the enhanced sensing performance. 2. Experimental 2.1Material Preparation This experiment used analytical grade reagents purchased from Aladdin Chemical Group Company Ltd, China, and the materials were used without further purification.In 2 O 3 nanoparticles were prepared by hydrothermal method[ 22 ]. First, 1.5 mmol In(NO 3 ) 3 ·5H 2 O, 5 mL glycerol, and 10 mL ethylene glycol were added into 5 mL deionized water to form a homogeneous solution. Then, it was transferred to a 50 mL Teflon-lined autoclave for hydrothermal treatment at 180 ◦ C for 12 h. After the reaction was completed, the autoclave was cooled to room temperature and then taken out, the white precipitate was cleaned by centrifugation with deionized water and ethanol several times, and dried in a vacuum oven at 60°C for 2 h. Finally, the white powder was calcined at 500°C for 2h to obtain a light yellow powder. The indium oxide nanopowder was dissolved in deionized water and dispersed in a ball mill for 4 h to prepare 0.09 g/ml raw material solution. Indium oxide gas-sensitive films modified with 0.5 mol% rare earth elements were prepared using a gas-sensitive film parallel synthesizer. First, the premixing function of the platform was set to mix the indium oxide raw material solution and different rare earth element additives homogeneously, and then the transferring function of the platform was set to deposit the mixed solution in the premixing vials on the prepared substrates, to obtain the indium oxide gas-sensitive films modified by different components. Then the film substrates printed with different materials were annealed in a tube furnace at 350°C for 2h to remove the organic solvent, and then heated up to 550°C for 2h to make the films dense. Finally, the substrates were prepared into eight-array gas sensors for high-throughput testing. The indium oxide sensor modified with 0.5mol% Gd was named Gd 0.5 In, and the unmodified indium oxide sensor was used as a blank control group. 2.2Characterization The crystalline phase of In 2 O 3 was investigated by X-ray diffractometer (XRD, Rigaku D/max-2500) with Cu Kα (λ = 1.5418 Å) in the range of 2θ = 10◦-90◦. The microstructure of the Gd 0.5 In gas-sensitive thin films was observed and analyzed using a field emission scanning electron microscope (FESEM JSM-7100F, JEOL). The distribution of Gd on the indium oxide gas-sensitive films was determined by a spectrometer (Hitachi S-4800). The elemental composition of the gas-sensitive films and the chemical states of the modifying elements in the gas-sensitive materials were analyzed by X-ray photoelectron spectroscopy (PHI5000 Versaprobe-II). 2.3Gas sensing tests Table 1 Modifies the type of element and its added proportions Modifying Elements Additive Surface Mole Ratio (%) Ce CeCl 3 ·7H 2 O Er Er(NO 3 ) 3 ·5H 2 O Eu EuCl 3 ·6H 2 O Gd Gd(NO 3 ) 3 Ho HoCl 3 ·6H 2 O La LaCl 3 ·6H 2 O 0.5 Nd Nd(NO 3 ) 3 ·6H 2 O Pr Pr(NO 3 ) 3 Sm SmCl 3 Y YCl 3 ·6H 2 O Yb Yb(NO 3 ) 3 ·5H 2 O Benzene, toluene, xylene, ethylbenzene, and other gases required in the experiments were equilibrated by the headspace method with self-contained air. Firstly, dry air was used as the carrier gas, and the cylinder was heated to 120°C several times to clean the cylinder. The required liquid injection volume was calculated by the formula PV = nRT, and a micro-sampler was used to inject the calculated volume of the target liquid into the valve chamber for heating and evaporation, and finally the target gas vaporized in the vacuum gas-tight gas distribution chamber was brought into the cylinder to complete the gas distribution. The gas-sensitive performance was tested by the high-throughput gas-sensitive material performance screening platform and the steady-state response of the prepared gas sensors to 100 ppm xylene was tested at 200°C, 250°C, 300°C and 350°C, respectively, to determine the optimal operating temperature. After determining the optimal operating temperature, the prepared sensors were tested at 5 ppm, 10 ppm, 50 ppm, and 100 ppm xylene respectively, to obtain the optimal concentration, each group of tests was repeated three times, and the average value of the response was taken. The formula for calculating gas sensitivity is S = R gas /R air , R gas is the stable resistance value of the test gas, R air is the stable resistance value in air, and the response recovery time is the time for the gas-sensitive material to adsorb and desorb the target gas to 90% of the stable value. 3. Results and Discussion 3.1 Morphology and Structure Characterization of pure In 2 O 3 and Gd- In 2 O 3 by XRD and FE-SEM are shown in Fig. 1 . The XRD peaks of In 2 O 3 nanoparticles in Fig. 1 (a) are consistent with the peaks of cubic phase In 2 O 3 (JCPDS NO. 65-3170). In 2 O 3 nanoparticles with diameter of 30-40nm were uniformly fabricated by hydrothermal method shown in Fig. 1 (b),then Gd(NO 3 ) 3 aqueous solution provides Gd 2+ ion, Gd 2+ ion film was coated on the surface of the indium oxide nanoparticles via physical vapor deposition deposition. No diffraction peaks of Gd are detected because of its low amount in In 2 O 3 . To further characterize the successful modification of Gd on the surface of In 2 O 3 , EDS testing was conducted on the gas sensitive film surface. Figure 2 shows the microscopic and macroscopic scanning electron micrographs of a single gas-sensitive film prepared by a high-throughput gas-sensitive material membrane parallel synthesizer. The prepared Gd 0.5 In gas-sensitive film is approximately circular, with good film-forming properties and no macroscopic cracks in Fig. 2 (a). Figure 2 (b) shows the microscopic cross-section which can be seen that the thickness of the gas-sensitive film prepared by the parallel synthesizer is relatively uniform and the film thickness is 3.51 µm. In addition,the composition of the samples was determined by EDS elemental mapping analysis which determined Gd successfully modified into In 2 O 3 .Due to the electrostatic interaction between Gd 2+ ions and negatively charged indium oxide, Gd 2+ ions are reduced and uniformly deposited on the surface of In 2 O 3 in Fig. 2 (c). The chemical composition and bonding state of the Gd 0.5 In microstructure were investigated using XPS analysis. The fully measured spectrum in Fig. 3 (a) shows that the sample consists of the elements In 2 O 3 , and Gd, and no obvious impurity peaks appear, indicating the high purity of Gd 0.5 In. The In3d energy state spectrum consists of two symmetric peaks corresponding to In3d 5/2 and In3d 3/2 , located at 444.15 eV and 451.75 eV, respectively, which is due to the coexistence of trivalent indium and metallic indium. The spectra of the O1s peaks in Fig. 3 (b) have peaks at 530.2 eV and 532.5 eV corresponding to lattice oxygen and oxygen vacancies, respectively. As seen in Fig. 3 (c), the Gd 4d spectrum consists of Gd 4d 5/2 and Gd 4d 3/2 band energy peaks at 142.9 eV and 151.5 eV. The Gd 3d spectrum consists of Gd 3d 5/2 and Gd 3d 3/2 band energy peaks at 1188.6 eV and 1194.3 eV in Fig. 3 (d). They correspond to Gd 0 and Gd 3+ (Gd 2 O 3 ). The binding energy of Gd 3d in the prepared material is negatively shifted compared to the standard Gd 3d binding energy position, indicating the electronic interaction between Gd ions and In 2 O 3 , which is benifit for the gas-sensing performance. Based on the above results, the successful modification of Gd nanoparticles in In 2 O 3 was demonstrated. 3.2 Gas-sensitive performance analysis Temperature is an important factor in the performance of gas sensors. To determine the optimal operating temperature of the fabricated sensors, 16 fabricated sensors were subjected to high throughput tests at 200°C, 250°C, 300°C and 350°C for 100 ppm xylene. The x-axis in Fig. 4 (a) represents 11 different rare earth elements, with the intersection of Ce and 200°C as an example, and the value of the z-axis represents the response value of the 0.5mol% Ce-modified indium oxide sensor to benzene at 200°C. The response value exhibits an upward trend with the increase in temperature, and for gas-sensitive materials, increasing temperature can provide more energy to prompt gas molecules to react with the material and produce a stronger signal response, so the optimal operating temperature of the prepared rare earth element modified In 2 O 3 is determined to be 350°C. Figure 4 (c) shows that 11 rare earth elements modified with 0.5mol% concentration of indium oxide were tested against 5, 10, 50, and 100 ppm xylene gas at 350°C, and the response values increased with the increase of gas concentration, among which the Gd-modified In 2 O 3 sensor had the highest response value. A performance comparison between the pure In 2 O 3 sensor and the Gd 0.5 In sensor indicated that the Gd 0.5 In sensor outperformed the pure indium oxide sensor significantly in Fig(b)(d). Gd significantly improves the performance of indium oxide gas sensors compared to other rare earth elements. Figure 5 (a) High-throughput material screening of In 2 O 3 modified with different concentrations of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5mol% Gd. At the same temperature, the response value increased with the enhancement of the modification content of the rare earth elements, and the best performance was achieved by the 0.5mol% Gd-modified In 2 O 3 . Rare earth element modification can provide effective catalytic active sites by enhancing the adsorption and dissociation of gas molecules on the material surface which helps to complete the gas reaction process faster and improve the gas-sensitive response. Figure 5 (b) Gd 0.5 In was tested against different xylene gas concentrations, and it was found that 0.5mol% Gd-modified In 2 O 3 was the most sensitive to 100 ppm xylene gas response at the optimal operating temperature. The response value of Gd 0.5 In to 100 ppm xylene gas was 17.8, which is 5.4 times higher than that of unmodified indium oxide (Ra/Rg = 3.3). The inset shows a function-fitting plot of gas sensitivity response to different concentrations at 350°C, with a correlation coefficient of R 2 > 0.952, indicating a good linear relationship between the 0.5mol% Gd surface modified In 2 O 3 sensor and xylene gas concentration[ 23 ]. The sensor is capable of detecting deep low gas concentrations with a minimum detection limit concentration of 0.2ppm. Even if the environment contains only 0.2ppm of the target gas, the sensor will still send out a detection signal. Accurate detection of low concentrations of xylene gas is crucial for human health and environmental safety.To evaluate the adaptability and stability of the gas-sensitive materials in multiple gas environments, the response performance of Gd 0.5 In to benzene, toluene, xylene, ethylbenzene, methanol, ethanol, and formaldehyde was tested under the same conditions. Figure 5 (c) demonstrates the response values of Gd 0.5 In to different target gases at 100 ppm at 350°C. The response values of Gd 0.5 In to xylene are significantly higher than those of other gases, in which the response values of methanol, benzene, ethylbenzene, toluene, ethanol, and formaldehyde are 3.6, 3.9, 4.1, 8.3, 3, and 2.7, respectively. The sensitivities of Gd 0.5 In to xylene are about 4.5 times higher than that of alcohol, benzene, and ethylbenzene, 2 times higher compared to toluene and 5.9 times higher compared to ethanol and formaldehyde. The results indicate that the selectivity of the sensor with 0.5mol% Gd surface-modified modified In 2 O 3 for xylene gas is superior to that of the other tested gases in similar operating conditions. In order to compare the performance of unmodified and modified indium oxide sensors, the study measured the resistance change of both sensors. Figure 6 (a)(b) shows the recovery characteristics of the responses of Gd 0.5 In and In 2 O 3 to 100 ppm of xylene gas sensors at 350°C, respectively. As the target gas is introduced, the resistance of all sensors rapidly decreases and stabilizes. When the target gas is stopped, the resistance value increases and returns to the initial resistance. It can be seen that the resistance of the indium oxide sensor modified by Gd is significantly lower than that of the indium oxide sensor. After the Gd modified indium oxide sensor, the baseline resistance decreased from 150 kiloohms to 6 kiloohms, making it more suitable for the sensor.The sensor decrease in resistance after modification of Gd is beneficial for capturing more electrons on the surface, resulting in the generation of more oxygen atoms and active sites, and improving the gas sensing performance of metal oxide gas sensors. During testing at 350°C, the Gd 0.5 In gas sensor showed a response time of 11.1 s and a recovery time of 201.2 s for 100 ppm xylene gas. In comparison, the unmodified In 2 O 3 gas sensor exhibited a response time of 156 s and a recovery time of 220 s. These results indicate the Gd 0.5 In gas sensor significantly reduces the sensor's response time, which is advantageous for detecting and recovering xylene in real-life situations. This feature facilitates the early detection and warning of xylene, providing a practical solution for real-life applications. To evaluate the long-term stability of the sensor, the sensor was tested periodically over 50 days. In Fig. 7 (a), the Gd 0.5 In was tested continuously at 350°C for 100 ppm xylene gas, and the reversible cyclic curve for three cycles maintained the original response value without any significant degradation. Figure 7 (b) shows that the response of Gd 0.5 In to xylene gas maintains a 3.4% absolute deviation fluctuation within 50 days. Owing to the modification of Gd, the Gd 0.5 In sensor exhibits stability, good reproducibility, and fatigue resistance. 3.3 Gas-sensing mechanism analysis of rare earth-modified In 2 O 3 To date, the most widely accepted mechanism for gas sensing is based on the change in electrical resistance due to chemisorption and de-attraction of oxygen and xylene molecules on the surface of gas sensors[ 24 , 25 ]. The chemical reactivity consists of the adsorption-oxidation-desorption process which is influenced by the surface depletion layer and surface diffusion. When oxygen molecules in the air contact with the sensing film, they react with the electrons present on the In 2 O 3 conductive band, creating a thicker electron-loss layer, which increases the electrical resistance and generates reactive oxygen species (Fig. 8 (a))[ 26 ]. When the sensor of In 2 O 3 is exposed to xylene gas, the xylene molecules adsorb to the active sites on the sensor surface to interact with chemisorbed oxygen ions(O 2− , O − , O 2− ). Adsorption of xylene may lead to electron transfer from indium oxide to adsorbed molecules, resulting in changes in conductivity and resistivity[ 27 ]. As shown in Fig. 8 (b), the electrons released could react with xylene gas on the surface of the rare earth element-modified In 2 O 3 sensor, leading to a decrease in the Fermi energy level which in turn lowers the resistance of the In 2 O 3 -based gas sensor. As disscussed in Fig. 6 , the introduction of rare earth elements on the surface of In 2 O 3 dcreased the resistance of the sensor, leading to the formation of more free electrons [ 28 ], resulting in the generation of more active oxygen species [ 29 ]. First, when modifying In 2 O 3 with rare earth elements, more oxygen molecules can be transferred from the rare earth elements to the In 2 O 3 surface due to the spillover effect of the rare earth elements [ 30 , 31 ].In addition, the electron sensitization effect of rare earth elements [ 32 ] enables the surface to adsorb oxygen molecules and generate oxygen atoms. This is why Gd-In 2 O 3 composites have a better response than pure In 2 O 3 sensors. 4 Conclusions In this study, a high-performance xylene sensor was developed based on indium oxide modified with Gd. The modification of Gd could boost the concentration of free electrons, which on the one hand could react with oxygen molecules to form surface-active oxygen species to enhance surface catalysis, and on the other hand strengthen the electron-transferring ability of the sensor. This study provide a effective route to develop high performance semiconductor based VOCs sensors. Declarations Ethical Approval Not applicable. Funding This work acknowledges the support from the National Natural Science Foundation of China (62101225, 52304400), the Yunnan Fundamental Research Project (202201AT070072, 202201AU070156). This work is also supported by the open project (KJS2306) of Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University. Conflict of interest The authors declare that they have no competing financial interests exist. Consent for publication All authors approved the final manuscript and the submission to this journal. Availability of data and materials The datasets generated and analyzed during the current study are publicly available. Authors’ contributions Zhengxin Zhang wrote the main manuscript text. Deqi ZHANG, Li YANG, Ming HOU, Jiyun GAO,Yi XIA and Shenghui GUO:conceptualization, methodology, validation, formal analysis, writing—review and editing, visualization and supervision. References W.-T. Tsai, Environments, 3, 23 (2016) T.Z. Maung, J.E. Bishop, E. 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Interfaces. 8 , 10367 (2016) Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 12 Mar, 2024 Read the published version in Journal of Porous Materials → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3795548","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":263988533,"identity":"e05f5e4d-f3b0-4852-abf9-97a92475bb45","order_by":0,"name":"Zhengxin ZHANG","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Zhengxin","middleName":"","lastName":"ZHANG","suffix":""},{"id":263988534,"identity":"b568b82b-9fb2-4616-8371-3220cbf8dc4b","order_by":1,"name":"Deqi ZHANG","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Deqi","middleName":"","lastName":"ZHANG","suffix":""},{"id":263988535,"identity":"118f7329-96db-4dd4-8be6-afcad4853ab0","order_by":2,"name":"Li YANG","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Li","middleName":"","lastName":"YANG","suffix":""},{"id":263988536,"identity":"7fc80abd-8310-479d-8729-782ad2bfc0f4","order_by":3,"name":"Ming HOU","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0ElEQVRIiWNgGAWjYBACAxCRAKUZPhjY2JGkhbFxRkFaMnFaoDRjM8+HQ4wNhLSYs/eYbni4o9ZYd0b688c2BgeYGdgPH92AT4tlzxmzG4lnjpuZ3cgxbM4xuMPHwJOWdgOvw27kALW0HbMBamEEannGzCDBY0aslvSHzRYGhxkbiNRSA3RYgmEzA1FazhwrA2o5YGx25o3hzB6DtGQ2gn453rzt5s+2OsNtx9MffPjxx8aOn/3wMbxaoOAwgslGhHIQqCNS3SgYBaNgFIxIAADXGVMz8+y/GAAAAABJRU5ErkJggg==","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Ming","middleName":"","lastName":"HOU","suffix":""},{"id":263988537,"identity":"e20577b5-8b18-48ef-b930-2bcf9dbf35f8","order_by":4,"name":"Jiyun GAO","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Jiyun","middleName":"","lastName":"GAO","suffix":""},{"id":263988538,"identity":"d5a7620f-867b-4598-9d20-b4ede2776692","order_by":5,"name":"Yi XIA","email":"","orcid":"","institution":"Kunming University of Science and Technology, and Analytic \u0026 Testing Research Center of Yunnan","correspondingAuthor":false,"prefix":"","firstName":"Yi","middleName":"","lastName":"XIA","suffix":""},{"id":263988541,"identity":"1f829765-dedb-4b6f-8c28-151e3f136205","order_by":6,"name":"Shenghui GUO","email":"","orcid":"","institution":"Kunming University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Shenghui","middleName":"","lastName":"GUO","suffix":""}],"badges":[],"createdAt":"2023-12-23 08:44:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3795548/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3795548/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10934-024-01582-z","type":"published","date":"2024-03-12T21:44:50+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":49017813,"identity":"06e7cfe5-e510-4dec-9d2a-e2b6d8469999","added_by":"auto","created_at":"2024-01-01 06:12:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":273991,"visible":true,"origin":"","legend":"\u003cp\u003eCharacterization. (a) XRD pattern of the In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Gd-In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e composite; (b) FESEM picture of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nano-powder\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-3795548/v1/8cd480341fa5c14f0ba81827.png"},{"id":49017819,"identity":"7cc3a145-4aa7-469e-b35b-12d21cc319f6","added_by":"auto","created_at":"2024-01-01 06:12:22","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1040237,"visible":true,"origin":"","legend":"\u003cp\u003eSEM and EDS images of gas-sensitive material films. (a) Macro and microphotographs; (b) Micro-sectional view; (c) EDS diagram of Gd\u003csub\u003e0.5\u003c/sub\u003eIn gas-sensitive film\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-3795548/v1/e7a5f7b8be52873d095c4edc.png"},{"id":49018051,"identity":"f8b9a8b5-0c51-4536-af53-b4fc89892b47","added_by":"auto","created_at":"2024-01-01 06:20:22","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":200570,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectra of Gd\u003csub\u003e0.5\u003c/sub\u003eIn. (a) full survey scan spectrum; (b) O 1s; (c) Gd 4d; (d) Gd3d\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-3795548/v1/a7448f9f9dfa8786832058f9.png"},{"id":49017817,"identity":"278ba552-dc79-4cdf-9d7c-898adf185603","added_by":"auto","created_at":"2024-01-01 06:12:22","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":260886,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Plot of the gas response of the rare-earth modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e gas sensor to 100 ppm xylene at different temperatures. (b) Response values of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Gd\u003csub\u003e0.5\u003c/sub\u003eIn to 100ppm xylene at different temperatures. (c) Rare-earth modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e gas sensor tested at 350 °C for different concentrations of xylene gas-sensitive performance. (d) Response values of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Gd\u003csub\u003e0.5\u003c/sub\u003eIn to different concentrations of xylene at 350°C Celsius\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-3795548/v1/0bab9355f8a5f5a840440ffc.png"},{"id":49018049,"identity":"6c8c2ddc-5e93-44f0-838d-975758e3b639","added_by":"auto","created_at":"2024-01-01 06:20:22","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":105854,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Response values of different concentrations of Gd modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e to xylene gas at different temperatures. (b) Response values of Gd\u003csub\u003e0.5\u003c/sub\u003eIn to different concentrations of xylene gas at 350 °C over time and the inset shows the functional fit of the gas-sensitive response of Gd\u003csub\u003e0.5\u003c/sub\u003eIn to different concentrations of xylene gas at 350 °C. (c) Response values of the Gd\u003csub\u003e0.5\u003c/sub\u003eIn sensor to different gases at 100 ppm at 350 °C\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-3795548/v1/1d3f1262adee3b339d43e9a3.png"},{"id":49018050,"identity":"662d2124-5c96-470b-a41c-b46a05480fe3","added_by":"auto","created_at":"2024-01-01 06:20:22","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":61680,"visible":true,"origin":"","legend":"\u003cp\u003eResponse recovery characteristics for 100 ppm Xylene Gas at 350 °C (a) Gd\u003csub\u003e0.5\u003c/sub\u003eIn sensor and (b) In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e sensor\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-3795548/v1/65a4dc59cfce5c65f8dbafdd.png"},{"id":49017814,"identity":"3a7c521b-839b-4442-bde8-1632ef3b3c6a","added_by":"auto","created_at":"2024-01-01 06:12:22","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":59377,"visible":true,"origin":"","legend":"\u003cp\u003eRepeatability and long-term stability of xylene gas sensors. (a) Reversible cycling curves for three consecutively tested reaction processes. (b) long-term stability test over 50 days\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-3795548/v1/6b4d4c012ab9b0fb05020e0c.png"},{"id":49018241,"identity":"dcc8cfc0-5420-4a2e-9e6a-615517173b1f","added_by":"auto","created_at":"2024-01-01 06:28:22","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":122120,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the xylene sensing mechanism of the rare earth element modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e sensor. (a) Air; (b) xylene gas\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-3795548/v1/54492f1319cc87785d667cc0.png"},{"id":52795595,"identity":"8207d24d-19b8-4880-9d38-f12c71793c6d","added_by":"auto","created_at":"2024-03-15 21:44:55","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2449288,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3795548/v1/462625af-ba4d-402a-9a5c-301f9c915fa3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eGd-modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e for the enhanced xylene sensing\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe effects of volatile organic compounds (VOCs) air pollutants on indoor and outdoor environments deserve special consideration because of their ability to damage human health and the environment which have become a primary worldwide concern for various scientific communities[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Among these VOC pollutants, BTEX (benzene, toluene, ethylbenzene, and xylenes), a subclass of VOCs, is inherently highly toxic and carcinogenic[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e],which can severely damage the liver, kidneys, spleen, and stomach[\u003cspan additionalcitationids=\"CR6 CR7\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].BTEX is typically present in everyday essentials such as thinners, degreasers, detergents, lubricants, and liquid fuels[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Therefore, it is very necessary to develop gas sensor for effective BETX detection.\u003c/p\u003e \u003cp\u003eIn\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, a typical n-type semiconductor, has been widely used to detect hazardous gases because of its wide band gap, fast saturation electron migration, and low resistivity[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. When volatile organic compound (VOC) molecules stick to the surface of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, it not only impacts the electron concentration on the surface of indium oxide, which affects its conductivity, but also alters the electronic state of the surface of indium oxide, which subsequently affects its electrical resistivity properties. However, the original In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e still has problems with high energy consumption and poor selectivity, which cannot meet the current increasingly high environmental monitoring requirements. In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e can be modified with noble metal elements,building heterojunction structures or modifying its surface to enhance the gas-sensitive response. But noble metal modification of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e is relatively expensive, and the high electrical resistance due to the heterostructure can lead to electrical noise that hinders the use of portable devices.[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Rare earth materials, known as \"industrial vitamins\", have been widely used as surface modifiers due to their high electrical conductivity, magnetic, electrochemical, and luminescent properties based on 4f electron leaps. [\u003cspan additionalcitationids=\"CR15 CR16 CR17 CR18\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Zhang et al[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] reported that the addition of Yb significantly improved the gas-sensitive performance of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e on formaldehyde. Hong et al[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] reported that 3 mol% Pr-doped In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticle-based sensors showed good sensing performance on xylene. Thus it can be seen that surface modification is an effective and straightforward way to improve gas sensing performance.However, most reported xylene gas sensors still suffer from slow response rates and poor reversibility.\u003c/p\u003e \u003cp\u003eHerein, Gd-modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e was successfully obtained via physical vapor deposition method and used to detect xylene. With the introdution of Gd, the In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e based sensor exhibited improved electrical property and catalytic effect, leading to the enhanced sensing performance.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1Material Preparation\u003c/h2\u003e \u003cp\u003eThis experiment used analytical grade reagents purchased from Aladdin Chemical Group Company Ltd, China, and the materials were used without further purification.In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles were prepared by hydrothermal method[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. First, 1.5 mmol In(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e \u0026middot;5H\u003csub\u003e2\u003c/sub\u003eO, 5 mL glycerol, and 10 mL ethylene glycol were added into 5 mL deionized water to form a homogeneous solution. Then, it was transferred to a 50 mL Teflon-lined autoclave for hydrothermal treatment at 180 \u003csup\u003e◦\u003c/sup\u003eC for 12 h. After the reaction was completed, the autoclave was cooled to room temperature and then taken out, the white precipitate was cleaned by centrifugation with deionized water and ethanol several times, and dried in a vacuum oven at 60\u0026deg;C for 2 h. Finally, the white powder was calcined at 500\u0026deg;C for 2h to obtain a light yellow powder.\u003c/p\u003e \u003cp\u003eThe indium oxide nanopowder was dissolved in deionized water and dispersed in a ball mill for 4 h to prepare 0.09 g/ml raw material solution. Indium oxide gas-sensitive films modified with 0.5 mol% rare earth elements were prepared using a gas-sensitive film parallel synthesizer. First, the premixing function of the platform was set to mix the indium oxide raw material solution and different rare earth element additives homogeneously, and then the transferring function of the platform was set to deposit the mixed solution in the premixing vials on the prepared substrates, to obtain the indium oxide gas-sensitive films modified by different components. Then the film substrates printed with different materials were annealed in a tube furnace at 350\u0026deg;C for 2h to remove the organic solvent, and then heated up to 550\u0026deg;C for 2h to make the films dense. Finally, the substrates were prepared into eight-array gas sensors for high-throughput testing. The indium oxide sensor modified with 0.5mol% Gd was named Gd\u003csub\u003e0.5\u003c/sub\u003eIn, and the unmodified indium oxide sensor was used as a blank control group.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2Characterization\u003c/h2\u003e \u003cp\u003eThe crystalline phase of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e was investigated by X-ray diffractometer (XRD, Rigaku D/max-2500) with Cu Kα (λ\u0026thinsp;=\u0026thinsp;1.5418 \u0026Aring;) in the range of 2θ\u0026thinsp;=\u0026thinsp;10◦-90◦. The microstructure of the Gd\u003csub\u003e0.5\u003c/sub\u003eIn gas-sensitive thin films was observed and analyzed using a field emission scanning electron microscope (FESEM JSM-7100F, JEOL). The distribution of Gd on the indium oxide gas-sensitive films was determined by a spectrometer (Hitachi S-4800). The elemental composition of the gas-sensitive films and the chemical states of the modifying elements in the gas-sensitive materials were analyzed by X-ray photoelectron spectroscopy (PHI5000 Versaprobe-II).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3Gas sensing tests\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eModifies the type of element and its added proportions\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModifying Elements\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdditive\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSurface Mole Ratio (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCe\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCeCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;7H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEr\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEr(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;5H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEu\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEuCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGd(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHoCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLa\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLaCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNd(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePr\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePr(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSmCl\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eY\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYb\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYb(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u0026middot;5H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eBenzene, toluene, xylene, ethylbenzene, and other gases required in the experiments were equilibrated by the headspace method with self-contained air. Firstly, dry air was used as the carrier gas, and the cylinder was heated to 120\u0026deg;C several times to clean the cylinder. The required liquid injection volume was calculated by the formula PV\u0026thinsp;=\u0026thinsp;nRT, and a micro-sampler was used to inject the calculated volume of the target liquid into the valve chamber for heating and evaporation, and finally the target gas vaporized in the vacuum gas-tight gas distribution chamber was brought into the cylinder to complete the gas distribution.\u003c/p\u003e \u003cp\u003eThe gas-sensitive performance was tested by the high-throughput gas-sensitive material performance screening platform and the steady-state response of the prepared gas sensors to 100 ppm xylene was tested at 200\u0026deg;C, 250\u0026deg;C, 300\u0026deg;C and 350\u0026deg;C, respectively, to determine the optimal operating temperature. After determining the optimal operating temperature, the prepared sensors were tested at 5 ppm, 10 ppm, 50 ppm, and 100 ppm xylene respectively, to obtain the optimal concentration, each group of tests was repeated three times, and the average value of the response was taken. The formula for calculating gas sensitivity is S\u0026thinsp;=\u0026thinsp;\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003egas\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/R\u003c/em\u003e\u003csub\u003e\u003cem\u003eair\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003egas\u003c/em\u003e\u003c/sub\u003e is the stable resistance value of the test gas, \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003eair\u003c/em\u003e\u003c/sub\u003e is the stable resistance value in air, and the response recovery time is the time for the gas-sensitive material to adsorb and desorb the target gas to 90% of the stable value.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Morphology and Structure\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCharacterization of pure In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Gd- In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e by XRD and FE-SEM are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The XRD peaks of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a) are consistent with the peaks of cubic phase In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (JCPDS NO. 65-3170). In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanoparticles with diameter of 30-40nm were uniformly fabricated by hydrothermal method shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b),then Gd(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e aqueous solution provides Gd\u003csup\u003e2+\u003c/sup\u003e ion, Gd\u003csup\u003e2+\u003c/sup\u003e ion film was coated on the surface of the indium oxide nanoparticles via physical vapor deposition deposition. No diffraction peaks of Gd are detected because of its low amount in In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003eTo further characterize the successful modification of Gd on the surface of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, EDS testing was conducted on the gas sensitive film surface. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the microscopic and macroscopic scanning electron micrographs of a single gas-sensitive film prepared by a high-throughput gas-sensitive material membrane parallel synthesizer. The prepared Gd\u003csub\u003e0.5\u003c/sub\u003eIn gas-sensitive film is approximately circular, with good film-forming properties and no macroscopic cracks in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a). Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b) shows the microscopic cross-section which can be seen that the thickness of the gas-sensitive film prepared by the parallel synthesizer is relatively uniform and the film thickness is 3.51 \u0026micro;m. In addition,the composition of the samples was determined by EDS elemental mapping analysis which determined Gd successfully modified into In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e.Due to the electrostatic interaction between Gd\u003csup\u003e2+\u003c/sup\u003e ions and negatively charged indium oxide, Gd\u003csup\u003e2+\u003c/sup\u003e ions are reduced and uniformly deposited on the surface of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(c).\u003c/p\u003e \u003cp\u003eThe chemical composition and bonding state of the Gd\u003csub\u003e0.5\u003c/sub\u003eIn microstructure were investigated using XPS analysis. The fully measured spectrum in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a) shows that the sample consists of the elements In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, and Gd, and no obvious impurity peaks appear, indicating the high purity of Gd\u003csub\u003e0.5\u003c/sub\u003eIn. The In3d energy state spectrum consists of two symmetric peaks corresponding to In3d\u003csub\u003e5/2\u003c/sub\u003e and In3d\u003csub\u003e3/2\u003c/sub\u003e, located at 444.15 eV and 451.75 eV, respectively, which is due to the coexistence of trivalent indium and metallic indium. The spectra of the O1s peaks in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(b) have peaks at 530.2 eV and 532.5 eV corresponding to lattice oxygen and oxygen vacancies, respectively. As seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c), the Gd 4d spectrum consists of Gd 4d\u003csub\u003e5/2\u003c/sub\u003e and Gd 4d\u003csub\u003e3/2\u003c/sub\u003e band energy peaks at 142.9 eV and 151.5 eV. The Gd 3d spectrum consists of Gd 3d\u003csub\u003e5/2\u003c/sub\u003e and Gd 3d\u003csub\u003e3/2\u003c/sub\u003e band energy peaks at 1188.6 eV and 1194.3 eV in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d). They correspond to Gd\u003csup\u003e0\u003c/sup\u003e and Gd\u003csup\u003e3+\u003c/sup\u003e (Gd\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e). The binding energy of Gd 3d in the prepared material is negatively shifted compared to the standard Gd 3d binding energy position, indicating the electronic interaction between Gd ions and In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, which is benifit for the gas-sensing performance. Based on the above results, the successful modification of Gd nanoparticles in In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e was demonstrated.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Gas-sensitive performance analysis\u003c/h2\u003e \u003cp\u003eTemperature is an important factor in the performance of gas sensors. To determine the optimal operating temperature of the fabricated sensors, 16 fabricated sensors were subjected to high throughput tests at 200\u0026deg;C, 250\u0026deg;C, 300\u0026deg;C and 350\u0026deg;C for 100 ppm xylene. The x-axis in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a) represents 11 different rare earth elements, with the intersection of Ce and 200\u0026deg;C as an example, and the value of the z-axis represents the response value of the 0.5mol% Ce-modified indium oxide sensor to benzene at 200\u0026deg;C. The response value exhibits an upward trend with the increase in temperature, and for gas-sensitive materials, increasing temperature can provide more energy to prompt gas molecules to react with the material and produce a stronger signal response, so the optimal operating temperature of the prepared rare earth element modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e is determined to be 350\u0026deg;C. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(c) shows that 11 rare earth elements modified with 0.5mol% concentration of indium oxide were tested against 5, 10, 50, and 100 ppm xylene gas at 350\u0026deg;C, and the response values increased with the increase of gas concentration, among which the Gd-modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e sensor had the highest response value. A performance comparison between the pure In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e sensor and the Gd\u003csub\u003e0.5\u003c/sub\u003eIn sensor indicated that the Gd\u003csub\u003e0.5\u003c/sub\u003eIn sensor outperformed the pure indium oxide sensor significantly in Fig(b)(d). Gd significantly improves the performance of indium oxide gas sensors compared to other rare earth elements.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a) High-throughput material screening of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e modified with different concentrations of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5mol% Gd. At the same temperature, the response value increased with the enhancement of the modification content of the rare earth elements, and the best performance was achieved by the 0.5mol% Gd-modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. Rare earth element modification can provide effective catalytic active sites by enhancing the adsorption and dissociation of gas molecules on the material surface which helps to complete the gas reaction process faster and improve the gas-sensitive response. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(b) Gd\u003csub\u003e0.5\u003c/sub\u003eIn was tested against different xylene gas concentrations, and it was found that 0.5mol% Gd-modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e was the most sensitive to 100 ppm xylene gas response at the optimal operating temperature. The response value of Gd\u003csub\u003e0.5\u003c/sub\u003eIn to 100 ppm xylene gas was 17.8, which is 5.4 times higher than that of unmodified indium oxide (Ra/Rg\u0026thinsp;=\u0026thinsp;3.3). The inset shows a function-fitting plot of gas sensitivity response to different concentrations at 350\u0026deg;C, with a correlation coefficient of R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.952, indicating a good linear relationship between the 0.5mol% Gd surface modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e sensor and xylene gas concentration[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The sensor is capable of detecting deep low gas concentrations with a minimum detection limit concentration of 0.2ppm. Even if the environment contains only 0.2ppm of the target gas, the sensor will still send out a detection signal. Accurate detection of low concentrations of xylene gas is crucial for human health and environmental safety.To evaluate the adaptability and stability of the gas-sensitive materials in multiple gas environments, the response performance of Gd\u003csub\u003e0.5\u003c/sub\u003eIn to benzene, toluene, xylene, ethylbenzene, methanol, ethanol, and formaldehyde was tested under the same conditions. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(c) demonstrates the response values of Gd\u003csub\u003e0.5\u003c/sub\u003eIn to different target gases at 100 ppm at 350\u0026deg;C. The response values of Gd\u003csub\u003e0.5\u003c/sub\u003eIn to xylene are significantly higher than those of other gases, in which the response values of methanol, benzene, ethylbenzene, toluene, ethanol, and formaldehyde are 3.6, 3.9, 4.1, 8.3, 3, and 2.7, respectively. The sensitivities of Gd\u003csub\u003e0.5\u003c/sub\u003eIn to xylene are about 4.5 times higher than that of alcohol, benzene, and ethylbenzene, 2 times higher compared to toluene and 5.9 times higher compared to ethanol and formaldehyde. The results indicate that the selectivity of the sensor with 0.5mol% Gd surface-modified modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e for xylene gas is superior to that of the other tested gases in similar operating conditions.\u003c/p\u003e \u003cp\u003eIn order to compare the performance of unmodified and modified indium oxide sensors, the study measured the resistance change of both sensors. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(a)(b) shows the recovery characteristics of the responses of Gd\u003csub\u003e0.5\u003c/sub\u003eIn and In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e to 100 ppm of xylene gas sensors at 350\u0026deg;C, respectively. As the target gas is introduced, the resistance of all sensors rapidly decreases and stabilizes. When the target gas is stopped, the resistance value increases and returns to the initial resistance. It can be seen that the resistance of the indium oxide sensor modified by Gd is significantly lower than that of the indium oxide sensor. After the Gd modified indium oxide sensor, the baseline resistance decreased from 150 kiloohms to 6 kiloohms, making it more suitable for the sensor.The sensor decrease in resistance after modification of Gd is beneficial for capturing more electrons on the surface, resulting in the generation of more oxygen atoms and active sites, and improving the gas sensing performance of metal oxide gas sensors. During testing at 350\u0026deg;C, the Gd\u003csub\u003e0.5\u003c/sub\u003eIn gas sensor showed a response time of 11.1 s and a recovery time of 201.2 s for 100 ppm xylene gas. In comparison, the unmodified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e gas sensor exhibited a response time of 156 s and a recovery time of 220 s. These results indicate the Gd\u003csub\u003e0.5\u003c/sub\u003eIn gas sensor significantly reduces the sensor's response time, which is advantageous for detecting and recovering xylene in real-life situations. This feature facilitates the early detection and warning of xylene, providing a practical solution for real-life applications.\u003c/p\u003e\u003cp\u003eTo evaluate the long-term stability of the sensor, the sensor was tested periodically over 50 days. In Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(a), the Gd\u003csub\u003e0.5\u003c/sub\u003eIn was tested continuously at 350\u0026deg;C for 100 ppm xylene gas, and the reversible cyclic curve for three cycles maintained the original response value without any significant degradation. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(b) shows that the response of Gd\u003csub\u003e0.5\u003c/sub\u003eIn to xylene gas maintains a 3.4% absolute deviation fluctuation within 50 days. Owing to the modification of Gd, the Gd\u003csub\u003e0.5\u003c/sub\u003eIn sensor exhibits stability, good reproducibility, and fatigue resistance.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Gas-sensing mechanism analysis of rare earth-modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eTo date, the most widely accepted mechanism for gas sensing is based on the change in electrical resistance due to chemisorption and de-attraction of oxygen and xylene molecules on the surface of gas sensors[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The chemical reactivity consists of the adsorption-oxidation-desorption process which is influenced by the surface depletion layer and surface diffusion. When oxygen molecules in the air contact with the sensing film, they react with the electrons present on the In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e conductive band, creating a thicker electron-loss layer, which increases the electrical resistance and generates reactive oxygen species (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(a))[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. When the sensor of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e is exposed to xylene gas, the xylene molecules adsorb to the active sites on the sensor surface to interact with chemisorbed oxygen ions(O\u003csub\u003e2\u0026minus;\u003c/sub\u003e, O\u003csup\u003e\u0026minus;\u003c/sup\u003e, O\u003csup\u003e2\u0026minus;\u003c/sup\u003e). Adsorption of xylene may lead to electron transfer from indium oxide to adsorbed molecules, resulting in changes in conductivity and resistivity[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(b), the electrons released could react with xylene gas on the surface of the rare earth element-modified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e sensor, leading to a decrease in the Fermi energy level which in turn lowers the resistance of the In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e-based gas sensor. As disscussed in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the introduction of rare earth elements on the surface of In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e dcreased the resistance of the sensor, leading to the formation of more free electrons [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], resulting in the generation of more active oxygen species [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. First, when modifying In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e with rare earth elements, more oxygen molecules can be transferred from the rare earth elements to the In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e surface due to the spillover effect of the rare earth elements [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].In addition, the electron sensitization effect of rare earth elements [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] enables the surface to adsorb oxygen molecules and generate oxygen atoms. This is why Gd-In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e composites have a better response than pure In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e sensors.\u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusions","content":"\u003cp\u003eIn this study, a high-performance xylene sensor was developed based on indium oxide modified with Gd. The modification of Gd could boost the concentration of free electrons, which on the one hand could react with oxygen molecules to form surface-active oxygen species to enhance surface catalysis, and on the other hand strengthen the electron-transferring ability of the sensor. This study provide a effective route to develop high performance semiconductor based VOCs sensors.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical Approval\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work acknowledges the support from the National Natural Science Foundation of China (62101225, 52304400), the Yunnan Fundamental Research Project (202201AT070072, 202201AU070156). This work is also supported by the open project (KJS2306) of Jiangsu Key Laboratory for Carbon-Based Functional Materials \u0026amp; Devices, Soochow University.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing financial interests exist.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors approved the final manuscript and the submission to this journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and analyzed during the current study are publicly available.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eZhengxin Zhang wrote the main manuscript text. Deqi ZHANG, Li YANG, Ming HOU, Jiyun GAO,Yi XIA and Shenghui GUO:conceptualization, methodology, validation, formal analysis, writing\u0026mdash;review and editing, visualization and supervision.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eW.-T. Tsai, Environments, 3, 23 (2016)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eT.Z. Maung, J.E. Bishop, E. Holt, A.M. Turner, C. Pfrang, IJERPH 19, 8752 (2022)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eD. Zhang, Y. Fan, G. Li, Z. Ma, X. Wang, Z. Cheng, J. Xu, Sens. Actuators B \u003cb\u003e293\u003c/b\u003e, 23 (2019)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eN.J. Gentner, L.P. Weber, Arch. Toxicol. \u003cb\u003e85\u003c/b\u003e, 337 (2011)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. F\u0026ouml;ldešiov\u0026aacute;, A. Bal\u0026aacute;ži, Ľ. Chrastinov\u0026aacute;, J. Pivko, J. Kotwica, A.H. Harrath, P. Chrenek, A.V. 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Interfaces. \u003cb\u003e8\u003c/b\u003e, 10367 (2016)\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"rare earth elements, In2O3, gas sensor, xylene","lastPublishedDoi":"10.21203/rs.3.rs-3795548/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3795548/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eModifying with rare earth elements has been proven to be an effective means of enhancing the gas-sensing properties of oxides. In this work,Gd-In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e based sensor was developed, which showed high response to 100 ppm xylene gas (Ra/Rg\u0026thinsp;=\u0026thinsp;17.8) fast response time (11 s) at 350\u0026deg;C, this response value was 5.4 times higher compared to the unmodified In\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e sensor (Ra/Rg\u0026thinsp;=\u0026thinsp;3.3). The introduction of the rare earth element not only improves the electrical properties of the sensitive material to provide a more suitable resistance, but also strengthens the gas adsorption ability and the catalytic effect on the surface of the sensitive material, leading to the enhanced sensing performance.\u003c/p\u003e","manuscriptTitle":"Gd-modified In2O3 for the enhanced xylene sensing","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-01 06:12:17","doi":"10.21203/rs.3.rs-3795548/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d5c4d783-9c71-4320-becb-45c96bd563a7","owner":[],"postedDate":"January 1st, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-03-15T21:44:50+00:00","versionOfRecord":{"articleIdentity":"rs-3795548","link":"https://doi.org/10.1007/s10934-024-01582-z","journal":{"identity":"journal-of-porous-materials","isVorOnly":false,"title":"Journal of Porous Materials"},"publishedOn":"2024-03-12 21:44:50","publishedOnDateReadable":"March 12th, 2024"},"versionCreatedAt":"2024-01-01 06:12:17","video":"","vorDoi":"10.1007/s10934-024-01582-z","vorDoiUrl":"https://doi.org/10.1007/s10934-024-01582-z","workflowStages":[]},"version":"v1","identity":"rs-3795548","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3795548","identity":"rs-3795548","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}