Low Temperature NO2 Gas Sensing by Delafossite-Structured AgFeO2 Nanograins

Low Temperature NO2 Gas Sensing by Delafossite-Structured AgFeO2 Nanograins | 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 Low Temperature NO2 Gas Sensing by Delafossite-Structured AgFeO2 Nanograins Neha More, Rahul Bhise, Maheshwari Zirpe, Mukesh Padvi, Jyotsna Thakur This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3870485/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Nitrogen Dioxide (NO 2 ) gas monitoring has become increasingly important to ensure the safety of human lives and the environment. The present study investigates the potential of low-cost delafossite-structured AgFeO 2 nanoparticles to detect NO 2 gas at low temperature. Highly porous, grain-like AgFeO 2 nanoparticles were prepared by simple co-precipitation method and characterized using XRD, FESEM-EDS, TEM and BET analysis.AgFeO 2 nanograins synthesized by conventional method, demonstrated gas-sensing performance with respect to sensitivity (1.89%), short response (51s) and, selectivity at low temperature of 50 o C, towards 8 ppm NO 2 gas. AgFeO2 gas sensor NO2 low temperature delafossite Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction The advent of industrial development revamped the pattern of life. It accelerated not only the pace of urbanization and economic growth but also, electrification, deforestation, unbalanced climate, and environmental deterioration [ 1 ]. Industrial releases, overuse of electric power plants and automobile sources are contributing seriously to the release of NO x in the environment. Especially, NO 2 poses many detrimental effects on human and environmental health such as acid rain, photochemical smog, ozone layer destruction etc. [ 2 ], NO 2 exposure to humans may cause serious health hazards such as headache, lung inflammation, eye and throat burning etc. [ 3 ]. According to World Health Organisation (WHO) (2021) recommendation for atmospheric NO 2 is 25 µg/m 3 per day [ 4 ]. Therefore, to ensure environmental safety, it becomes necessary to monitor air quality with respect to pollutant gases including NO 2 and their control [ 3 ]. Recent progress in emission control technology has led to the creation of effective monitoring and measuring systems, including sensor-based systems that can help to comply with strict emission regulations [ 2 ]. In this regard, various types of systems based on optical [ 5 ], photoacoustic [ 6 ], chromatographic [ 7 ] and Nanostructured metal oxide-based sensors [ 8 ] were developed for monitoring NO 2 level in the air. Nanostructured metal oxides are emerging as a promising gas-sensing material because of their low cost, controllable size, stability, safety, and availability. [ 8 – 9 ]. Additionally, they may have a wide band gap, a large number of active sites and a high surface area which facilitates the adsorption of Oxygen ions and NO 2 molecules on the surface [ 10 – 11 ]. The research on the nanostructured metal oxides-based gas sensor is mainly focused on the manipulation in grain size, morphology, and structural properties for enhancing their gas sensing performance [ 12 – 13 ]. Also, lots of efforts were invested in developing n-type, p-type semiconducting material and heterojunction sensitization to improve the sensing properties [ 14 ]. Metal oxides with a variety of morphologies and surface properties such as CuO [ 15 ], SnO 2 /rGO [ 16 ], TiO 2 /ZnO [ 17 ] have been already reported in gas sensing. They are resistive and their electrical conductivity changes with concentration at specified operating temperature. The operating temperature is always a crucial factor for any Metal oxide-based gas sensor, as it influences surface electron conductivity, mobility, and overall surface reaction kinetics, significantly affecting Metal oxide nanoparticles' sensing performance. [ 18 ] Traditionally used metal oxides-based gas sensors typically requiring higher temperature, usually within 150–500°C range. This is because sufficient thermal energy is required to overcome the activation energy barrier of surface redox reaction and to increase the free carrier concentration in metal oxides for the sensing measurement [ 19 – 20 ]. The main drawback of operating the sensors at high temperatures is the risk of explosion which recommends restricting their usage in numerous applications. Also, high operating temperature leads to increased power consumption, which is a crucial consideration for the latest battery-powered wireless sensors [ 20 ]. Therefore, there is a great demand for gas sensors that are efficient and reliable and operate at a low temperature [ 21 – 25 ]. AgFeO 2 is delafossite structured semiconductor material [ 26 – 27 ]. Its unique structure, electronic features semiconducting and magnetic behaviour made it an attractive material for many applications including battery [ 28 ] and electrochemical applications [ 29 ]. In our previous work, we have successfully used it as an adsorbent for dye removal [ 27 , 30 ] However, its sensing applications have not been much explored. Wang et al used AgFeO 2 nanoparticles for ethanol sensing after irradiating them with γ radiation [ 31 ]. The present study reports the facile synthesis of AgFeO 2 nanoparticles via a simple co-precipitation method and examines their efficiency as a working electrode in NO 2 gas sensor. We are reporting first time gas sensing performance of delafossite-structured AgFeO 2 nanoparticles towards NO 2 gas at low temperature. 2. Materials and methods 2.1 Materials AgNO 3 , Fe(NO 3 ) 3 , Ammonium hydroxide purchased from Sigma-Aldrich. All the chemicals used in the study were of Analytical grade. Gas cylinders of NO 2 , LPG, NH 3 , SO 2 gas of 1000 ppm concentration were purchased from M/s. Shreya Enterprises Pvt. Ltd, India. 2.2 Methods AgFeO 2 was synthesised by the co-precipitation method [ 27 , 32 ]. 0.01M Silver nitrate and 0.05M Ferric Nitrate were dissolved in 100 ml Deionized water separately and mixed by stirring for 4 h at room temperature. The mixture was then heated at 70°C for 1 hr. pH of the solution was adjusted to 12 using 0.01M Sodium hydroxide solution and further stirred overnight to obtain a red-brown precipitate. Precipitate was filtered, washed and then sonicated for 10 mins with deionized water followed by drying at 70°C. The ruby red powder was then annealed at 400°C for 4 hrs to remove extraneous matter. A smooth and thin film of as-prepared AgFeO 2 was deposited over a glass substrate by using doctor blade method [ 33 ]. 2.3 Characterisation Structural characterization of AgFeO 2 nanoparticles was performed on X-Ray diffractometer (X’pert Pro PANalytical). Average particle size was determined by Debey-Schrrer equation. Morphological characteristics were examined using high-resolution transmission electron microscopy (HRTEM) equipped with selected area electron diffraction (Tecnai G2, F30 HRTEM-300kV) and field emission scanning electron microscopy (FEI-Quanta FEG 200F) along with energy dispersive spectroscopy (EDS). The specific surface areas were measured by the N 2 adsorption/desorption isotherm (Micrometrics ASAP 2020 Porosimeter) Brunauer-Emmett-Teller (BET) technique. 2.4 Gas sensing measurement Gas sensing measurements for NO 2 gas were conducted using a gas sensing unit comprised of a stainless-steel cylindrical chamber with inlet and outlet gas valves. The chamber is airtight with silicone rubber, and a heater is attached to the bottom. The gas sensing element holder with adjustable contacts was arranged inside the 250 cc volume capacity chamber. [ 32 ]. Resistance of the sensing element was measured with respect to time using a RIGOL (DM3058) digital multimeter. AgFeO 2 -coated glass substrate having a 1 cm 2 area was used for the gas sensing measurements. Two electrical contacts of silver paste were drawn on the surface. After stabilizing the resistance of the sensing element at an optimized temperature, the resistance of the sensor was measured with respect to time in the atmospheric air and the targeted gas conditions. The gas response (%) is calculated for the material mentioned as follows.[ 32 ] (Table 1 ) Table 1 Calculation of Gas response for p-type and n-type material for oxidizing and reducing gas Material Gas response (%) formula used for Eq. p-type oxidizing gas \(\frac{{\text{R}}_{\text{a}\text{i}\text{r}}-{\text{R}}_{\text{g}\text{a}\text{s}}}{{\text{R}}_{\text{g}\text{a}\text{s}}} \times 100 \text{%}\) Reducing gas \(\frac{{\text{R}}_{\text{g}\text{a}\text{s}}-{\text{R}}_{\text{a}\text{i}\text{r}}}{{\text{R}}_{\text{a}\text{i}\text{r}}} \times 100 \text{%}\) (1) n-type oxidizing gas \(\frac{{\text{R}}_{\text{g}\text{a}\text{s}}-{\text{R}}_{\text{a}\text{i}\text{r}}}{{\text{R}}_{\text{a}\text{i}\text{r}}} \times 100 \text{%}\) Reducing gas \(\frac{{\text{R}}_{\text{a}\text{i}\text{r}}-{\text{R}}_{\text{g}\text{a}\text{s}}}{{\text{R}}_{\text{g}\text{a}\text{s}}} \times 100 \text{%}\) (2) Here R gas represents the resistance in the presence of the target gas, and R air represents the resistance in ambient air [ 34 ]. 3. Results and discussion 3.1 Material characterization Typical indexed XRD pattern of AgFeO 2 is shown in Fig. 1 . All the reflections matched to the data in JCPDS file 75-2147. None of the reflection indicated presence of impurities like Ag or Fe 2 O 3 in the spectra. The peaks in the pattern were corresponded to the delafossite structure indicating presence of both polytypes rhombohedral, 3R (Space group R-3m ) and hexagonal, 2H (Space group: P6 3 /mmc ) respectively [ 35 – 37 ]. The average crystallite size calculated by Debey Scherrer equation was 47nm. AgFeO 2 This non-stoichiometric compound is unstable at high temperature and decomposed to form secondary phases of Ag and Fe 2 O 3 . This observation is in agreement with the previous published studies by Murthy et al and Siedliska et al [ 32 , 38 ]. FE-SEM micrograph in Fig. 2 a exhibits the dense distribution of slightly elongated nanoparticles of AgFeO 2 . EDS spectra (Fig. 2 b) confirms the elemental composition of AgFeO 2 with a weight percentage of Ag, Fe and O as 23.6%, 30.6% and 45.8% respectively. A typical HRTEM image of AgFeO 2 nanoparticles (Fig. 3 a) represents its microstructure and crystallographic details. Uniform, grain-like nanostructures having a breadth of ~ 50 nm and length of ~ 80 nm were seen in TEM analysis. This observation is consistent with XRD data. Figure 3 b represents SAED pattern of AgFeO 2 nanograins that reveals the polycrystalline nature of the nanoparticles. d-spacing values were calculated using ImageJ software application. The diffraction rings were indexed to the lattice parameters 006, 101, 105 and 110 of rhombohedral/hexagonal crystal planes of the delafossite structure of AgFeO 2 and agreed with the peaks in XRD spectra. Total pore volume and BET surface area are the important features of cathode/anode material. Pore size distribution and pore diameter describe the porous nature of the material. The nitrogen adsorption-desorption isotherms were used to obtain information about the BET specific surface area and pore size distribution. Adsorption isotherm in Fig. 4 a revealed the facts that the hysteresis loop is at relative pressure (P/P 0 ) close to unity, type IV hysteresis ascribed the presence of mesopores, H 1 hysteresis ascribed the presence of well-defined pore structure (IUPAC classification) and specific surface area was found to be 31.9353 ± 0.1551 m²/g. Broad BJH pore size distribution was in the range of 1.7–40 nm indicating the presence of mesoporous nanoparticles. The total pore volume was found to be 0.21 cm³ g − 1 . These results were highly consistent to our previous research work on AgFeO 2 [ 27 , 30 ] 3.2 Gas sensing measurements The gas-sensing properties of AgFeO 2 nanoparticles were evaluated through a change in resistance when exposed to the target gases. Figure 5 (a) shows the gas sensing of the AgFeO 2 sensor at an operating temperature of 50°C with a response time of 51 s. and recovery time of approximately 40% at 1000 s. After stabilizing the resistance of the AgFeO 2 gas sensor, the 8 ppm of NO 2 gas is purged into the gas sensing chamber [i.e., Gas ON]. After the ‘Gas ON’ condition, the change in the resistance of the sensor was measured with respect to time. In this case, when the oxidizing gas [NO 2 ] is used as the targeted gas, the resistance of the film decreases. It shows that the film is a ‘p-type’ in nature, therefore, all calculations were made using Eq. (1). The response time is calculated and schematically represented in Fig. 5 (a). The operating temperature for the AgFeO 2 gas sensor was optimized using gas concentration 8 ppm at different temperatures, 50°C, 75°C, and 100°C viz. The recorded gas responses (%) were observed 1.885%, 1.151%, and 1.149%, respectively. The Eq. (1) is used for the calculation of gas response (%). The highest gas response of 1.885% was achieved at an operating temperature of 50°C with a response time of 51 s. and approximately 40% recovery at 1000 s. This result suggests that the AgFeO 2 gas sensor performs optimally when detecting NO 2 gas at 50°C. Further, all subsequent gas sensing measurements for the AgFeO 2 gas sensor were carried out at the optimum operating temperature of 50°C. Figure 6 (a & b) illustrates the normalized gas response (%) and a histogram showing the performance of the AgFeO 2 gas sensor under varying NO 2 gas concentrations, ranging from 8 to 20 ppm at optimum temperature (50°C). The gas response (%) values for 8, 12, 16, and 20 ppm of NO 2 gas are 1.88%, 3.06%, 5.45%, and 7.77%, respectively. This observed trend clearly indicates that as the concentration of NO 2 gas increases, there is a gradual augmentation in the gas response (%). This phenomenon can be attributed to the behaviour of NO 2 gas molecules when gas is injected on the surface of the AgFeO 2 sensor. Upon contact, these molecules tend to adhere to the sensor's surface. With an escalation in the concentration of NO 2 gas, there is a greater availability of gas molecules for adhesion, resulting in an increased number of interactions between the gas molecules and the sensor's surface. At higher gas concentrations, a larger proportion of active sites on the AgFeO 2 sensor's surface become occupied by the gas molecules. [ 39 ] Consequently, this leads to a higher surface coverage of gas molecules, subsequently producing a stronger gas response from the sensor. [ 40 ] In essence, the sensor exhibits an increase in gas adsorption at elevated concentrations, accompanied by intensified interaction between the targeted gas molecules and the sensor's surface. The response time for the AgFeO 2 gas sensor at various gas concentrations is summarized in Table 2 . It was observed that the response time reduces with the increase in the concentration of NO 2 gas. This behaviour can be attributed to the several factors influencing the sensor's response time. At higher gas concentrations, there can be an accumulation of gas molecules near the sensor, resulting in a quick response time due to enhanced diffusion rates. Additionally, the response time may be contingent upon the degree of active site occupation by gas molecules on the sensor's surface. Variations in gas concentrations can lead to differences in surface coverage, thereby affecting the response time. The longer recovery time is attributed to slow surface reaction. However, there is scope to improve it by introducing metal catalysts through doping. [ 41 ] Table 2 Gas response (%), response time of thin film of AgFeO 2 nanograins at different concentrations of NO 2 gas The concentration of NO 2 gas (ppm). Gas Response (%) Response time (S) 8 1.88 51 12 3.06 50 16 5.45 44 20 7.77 37 Furthermore, the specific properties of the AgFeO 2 sensor, including its size, shape, and surface characteristics, can exert an influence on the adsorption and desorption processes. These sensor attributes contribute to the observed disparities in response times across different gas concentrations. Figure 7 shows the selectivity of the AgFeO 2 gas sensor towards different gases. To assess selectivity, we conducted tests on the AgFeO 2 gas sensor at an operating temperature of 50°C. The sensor's sensitivity to various target gases, including NO 2 , LPG, NH3, acetone and SO 2 , was evaluated, yielding response percentages of 1.88%, 0.14%, 0.0%, 0.0%, and 0.0%, respectively. Among these gases, the AgFeO 2 sensor displayed its highest sensitivity, reaching 1.88%, specifically to NO 2 gas. This response to NO 2 gas was remarkably 12 times greater than its response to LPG. Conversely, the sensor exhibited relatively weak responsiveness to the other targeted gases, rendering them non-measurable. This observation underscores the outstanding selectivity of the AgFeO 2 sensor towards NO 2 gas, particularly at lower operating temperatures. 3.3 Gas sensing mechanism The gas sensing results in a change in resistance because of the chemisorption and desorption process of oxygen present in the air and the target gas on the surface of the sensor. As mentioned in the literature, AgFeO 2 has a narrow band gap. [ 26 , 42 ] During the gas sensing, the electrons are transferred from the conduction band of AgFeO 2 to oxygen resulting in the formation of negative oxygen ions according to the following reactions [ 39 , 43 ]. O 2 (air) → O 2 (ads) (1) O 2 (ads) + e − → O 2 − (ads) (2) O 2 − (ads) + e − → 2O − (ads) (3) O − (ads) + e − → O 2− (ads) (4) As a result, the width of the depletion layer increases which leads to increase in resistance. When NO 2 is injected into the gas chamber, it is adsorbed on the AgFeO 2 surface, and being a strong oxidising gas, it donates holes and accepts both the negative oxygen ions (O 2 − , O − , O 2− ) and electrons from the layer and undergo the following reactions - NO 2 (gas) → NO 2 (ads) (5) NO 2 (ads) + O − (ads) + 2e − → NO 2 − (ads) + O 2− (ads) (6) NO 2 (ads) + e − → NO 2 − (7) This process results in thinning of the electron depletion layer and therefore, decrease in the sensor’s resistance. [ 44 – 47 ] This variation in resistance is used for the detection of NO 2 gas. 4. Conclusions In summary, we first time demonstrated the gas sensing properties of delafossite-structured AgFeO 2 nanoparticles towards NO 2 gas. Grain-like AgFeO 2 nanoparticles were prepared by simple co-precipitation method and well-characterized by XRD, FESEM, HRTEM and BET surface area. The nanoparticles showed high selectivity and excellent sensitivity to NO 2 gas with maximum gas response of 1.885% for 8 ppm of NO 2 gas at an operating temperature of 50°C, with a response time of 51 s. This study presents an approach for utilizing AgFeO 2 nanoparticles as a low-cost, p-type semiconducting material for the development of NO 2 gas sensors at low temperature. Declarations Conflict of interest: The authors report no conflicts of interest. Ethical Approval: Not applicable Funding: Not applicable. Availability of data and material: All pertinent information is presented within the manuscript and material is available upon request from the corresponding author. References Valmik, L. & Sultana, T., Impact of urbanization, industrialization, electrification and renewable energy on the environment in BRICS: fresh evidence from novel CS-ARDL model. Heliyon. 8(11), e11457, (2022). https://doi.org/10.1016/j.heliyon.2022.e11457 . 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Ultrason Sonochem. (2017), 37, 208–215. https://doi.org/10.1016/j.ultsonch.2017.01.010 Mutkule, S. U., Tehare, K. K., Gore, S. K., Krishna Chaitanya, G., & Mane, R. S. Ambient temperature Bi-Co ferrite NO 2 sensors with high sensitivity and selectivity. Materials Research Bulletin (2019), 115, 150–158. doi: 10.1016/j.materresbull.2019.03.012 Kim, H.-J., & Lee, J.-H. Highly sensitive and selective gas sensors using p-type oxide semiconductors: Overview. Sensors and Actuators B: Chemical, (2014), 192, 607–627. doi: 10.1016/j.snb.2013.11.005 Shankar, P. & Rayappan, J. B. B. Gas sensing mechanism of metal oxides: The role of ambient atmosphere, type of semiconductor and gases -A review. Science Letters. (2015). 4, 126. Majhi, S. M., Naik, G. K. Lee, H. J., Song, H. G., Lee, C. R., Lee, I. H. & Yu, Y. T. Au@NiO core-shell nanoparticles as a p-type gas sensor: Novel synthesis, characterization, and their gas sensing properties with sensing mechanism, Sensors and Actuators B: Chemical, (2018), 268, 223–231. Kumar, S., Pavelyev, V., Mishra, P., Tripathi, N., Sharma, P., & Calle, F. A review on 2D transition metal di-chalcogenides and metal oxide nanostructures based NO 2 gas sensors. Materials Science in Semiconductor Processing, (2020), 107, 104865. doi: 10.1016/j.mssp.2019.104865 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 25 Feb, 2024 Reviews received at journal 28 Jan, 2024 Reviewers agreed at journal 28 Jan, 2024 Reviewers invited by journal 27 Jan, 2024 Editor assigned by journal 21 Jan, 2024 Submission checks completed at journal 18 Jan, 2024 First submitted to journal 16 Jan, 2024 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-3870485","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":268377121,"identity":"1c28568d-54f4-4cc6-92f8-2d45a2e25be3","order_by":0,"name":"Neha More","email":"","orcid":"","institution":"Changu Kana Thakur Arts, Commerce and Science College, New Panvel (w)","correspondingAuthor":false,"prefix":"","firstName":"Neha","middleName":"","lastName":"More","suffix":""},{"id":268377122,"identity":"6435acc5-538c-48e1-b199-3f07162649d0","order_by":1,"name":"Rahul Bhise","email":"","orcid":"","institution":"Shivaji University","correspondingAuthor":false,"prefix":"","firstName":"Rahul","middleName":"","lastName":"Bhise","suffix":""},{"id":268377123,"identity":"3a42d8a6-0a3d-46fb-b1ac-4256f526bfe7","order_by":2,"name":"Maheshwari Zirpe","email":"","orcid":"","institution":"Ramsheth Thakur College, of Commerce and Science","correspondingAuthor":false,"prefix":"","firstName":"Maheshwari","middleName":"","lastName":"Zirpe","suffix":""},{"id":268377124,"identity":"8ec455b0-9308-41a8-8ded-06b3143fa178","order_by":3,"name":"Mukesh Padvi","email":"","orcid":"","institution":"Shivaji University","correspondingAuthor":false,"prefix":"","firstName":"Mukesh","middleName":"","lastName":"Padvi","suffix":""},{"id":268377125,"identity":"f3e21fe6-f7de-437f-a866-fecbbb149439","order_by":4,"name":"Jyotsna Thakur","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9klEQVRIiWNgGAWjYDACCQZmIMkG5VUAMTNzA14dPHAtYF1nQFoYidICtYixDcQioMVeuvmxMe8evsR++fZnD37Oq43mbwdq+VGxDbctMseMk3mesSXObOMxN+zddjx3xmHGBsaeM7fxOCzB+DDPAbbEDcd42CR4tx3LbQBqYWZsw6cl/TNUC/szyb9zjuXOJ6wlB+gwsBYGM2nehprcDQS13MgpNpxzgM14ZluOmbTMsQO5G4FaDuLzC/uM9M0Sbw4ck+1nPv5M8k1NXe6884cPPvhRgVsLFBxzbIAwDoPJA4TUA0GNPZRRR4TiUTAKRsEoGGkAAK5YWMdero+OAAAAAElFTkSuQmCC","orcid":"","institution":"Changu Kana Thakur Arts, Commerce and Science College, New Panvel (w)","correspondingAuthor":true,"prefix":"","firstName":"Jyotsna","middleName":"","lastName":"Thakur","suffix":""}],"badges":[],"createdAt":"2024-01-16 16:59:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3870485/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3870485/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":49968890,"identity":"2c75801a-55f0-452e-80c4-86f3eb3d134e","added_by":"auto","created_at":"2024-01-22 12:53:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":227275,"visible":true,"origin":"","legend":"\u003cp\u003eX\u003cstrong\u003e-Ray Diffraction pattern of AgFeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e; inset: Schematic representation of the delafossite structure (AgFeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e). Yellow and red spheres represent edge-shared Fe\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e3+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e and O6 distorted octahedra and linearly coordinated grey Ag\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e+ \u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003ecations\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3870485/v1/eea8dc9bd57332499c80f9d2.png"},{"id":49968893,"identity":"119da05e-9faa-466b-b696-b08c9885021a","added_by":"auto","created_at":"2024-01-22 12:53:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":556092,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) FE SEM image and (b) EDS spectra of AgFeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e nanoparticles\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3870485/v1/b24ca3c5fb2bc0172093fd0b.png"},{"id":49968889,"identity":"06ad0098-05e4-4c06-8016-74710f73cb22","added_by":"auto","created_at":"2024-01-22 12:53:43","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1120979,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) HRTEM image and (b) SAED Pattern of AgFeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2 \u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003enanoparticles\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-3870485/v1/2cf9cdc9a763b0422d8d0d70.png"},{"id":49968887,"identity":"3a4ebc49-557c-4899-b433-9287343a4b9f","added_by":"auto","created_at":"2024-01-22 12:53:43","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":95336,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) BET isotherm plot of surface area analysis and (b) BGH plot of pore size distribution\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-3870485/v1/a8a7e78b5d42209c42f472dc.png"},{"id":49969275,"identity":"30705dbc-21dd-4b55-a029-85e33ae17169","added_by":"auto","created_at":"2024-01-22 13:01:43","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":134893,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) Gas sensing performance of AgFeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e gas sensor for 8 ppm of NO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e at an operating temperature of 50 °C (b) Optimization of the operating temperature of AgFeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2 \u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003egas sensor at 8 ppm of NO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e gas.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-3870485/v1/24c10eea191216ca8bd3897d.png"},{"id":49969277,"identity":"71f1f123-195b-4885-b2db-b23ed1116311","added_by":"auto","created_at":"2024-01-22 13:01:43","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":133008,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) Normalized gas response (%) and (b) Histogram of gas response (%) of the AgFeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2 \u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003egas sensor at various NO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e gas concentrations, ranging from 8 to 20 ppm.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-3870485/v1/03e94a4a32f550802c4e323d.png"},{"id":49969276,"identity":"3732b76b-dc12-4ad7-93b5-579ba450be97","added_by":"auto","created_at":"2024-01-22 13:01:43","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":29708,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSelectivity of AgFeO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e gas sensor\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-3870485/v1/9de4f3b7f4ff03efb569e5bf.png"},{"id":49969633,"identity":"3cf6e8bd-242d-4344-9d9d-a180f650ddb7","added_by":"auto","created_at":"2024-01-22 13:09:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2022884,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3870485/v1/bcdae205-f2df-4b3e-9918-5ddddb6df021.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Low Temperature NO2 Gas Sensing by Delafossite-Structured AgFeO2 Nanograins","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe advent of industrial development revamped the pattern of life. It accelerated not only the pace of urbanization and economic growth but also, electrification, deforestation, unbalanced climate, and environmental deterioration [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Industrial releases, overuse of electric power plants and automobile sources are contributing seriously to the release of NO\u003csub\u003ex\u003c/sub\u003e in the environment. Especially, NO\u003csub\u003e2\u003c/sub\u003e poses many detrimental effects on human and environmental health such as acid rain, photochemical smog, ozone layer destruction etc. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], NO\u003csub\u003e2\u003c/sub\u003e exposure to humans may cause serious health hazards such as headache, lung inflammation, eye and throat burning etc. [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. According to World Health Organisation (WHO) (2021) recommendation for atmospheric NO\u003csub\u003e2\u003c/sub\u003e is 25 \u0026micro;g/m\u003csup\u003e3\u003c/sup\u003e per day [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Therefore, to ensure environmental safety, it becomes necessary to monitor air quality with respect to pollutant gases including NO\u003csub\u003e2\u003c/sub\u003e and their control [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRecent progress in emission control technology has led to the creation of effective monitoring and measuring systems, including sensor-based systems that can help to comply with strict emission regulations [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. In this regard, various types of systems based on optical [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], photoacoustic [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], chromatographic [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and Nanostructured metal oxide-based sensors [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] were developed for monitoring NO\u003csub\u003e2\u003c/sub\u003e level in the air. Nanostructured metal oxides are emerging as a promising gas-sensing material because of their low cost, controllable size, stability, safety, and availability. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Additionally, they may have a wide band gap, a large number of active sites and a high surface area which facilitates the adsorption of Oxygen ions and NO\u003csub\u003e2\u003c/sub\u003e molecules on the surface [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The research on the nanostructured metal oxides-based gas sensor is mainly focused on the manipulation in grain size, morphology, and structural properties for enhancing their gas sensing performance [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Also, lots of efforts were invested in developing n-type, p-type semiconducting material and heterojunction sensitization to improve the sensing properties [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Metal oxides with a variety of morphologies and surface properties such as CuO [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], SnO\u003csub\u003e2\u003c/sub\u003e/rGO [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], TiO\u003csub\u003e2\u003c/sub\u003e/ZnO [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] have been already reported in gas sensing. They are resistive and their electrical conductivity changes with concentration at specified operating temperature.\u003c/p\u003e \u003cp\u003eThe operating temperature is always a crucial factor for any Metal oxide-based gas sensor, as it influences surface electron conductivity, mobility, and overall surface reaction kinetics, significantly affecting Metal oxide nanoparticles' sensing performance. [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eTraditionally used metal oxides-based gas sensors typically requiring higher temperature, usually within 150\u0026ndash;500\u0026deg;C range. This is because sufficient thermal energy is required to overcome the activation energy barrier of surface redox reaction and to increase the free carrier concentration in metal oxides for the sensing measurement [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The main drawback of operating the sensors at high temperatures is the risk of explosion which recommends restricting their usage in numerous applications. Also, high operating temperature leads to increased power consumption, which is a crucial consideration for the latest battery-powered wireless sensors [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Therefore, there is a great demand for gas sensors that are efficient and reliable and operate at a low temperature [\u003cspan additionalcitationids=\"CR22 CR23 CR24\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAgFeO\u003csub\u003e2\u003c/sub\u003e is delafossite structured semiconductor material [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Its unique structure, electronic features semiconducting and magnetic behaviour made it an attractive material for many applications including battery [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] and electrochemical applications [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. In our previous work, we have successfully used it as an adsorbent for dye removal [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] However, its sensing applications have not been much explored. Wang et al used AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles for ethanol sensing after irradiating them with γ radiation [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe present study reports the facile synthesis of AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles via a simple co-precipitation method and examines their efficiency as a working electrode in NO\u003csub\u003e2\u003c/sub\u003e gas sensor. We are reporting first time gas sensing performance of delafossite-structured AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles towards NO\u003csub\u003e2\u003c/sub\u003e gas at low temperature.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Materials\u003c/h2\u003e\n \u003cp\u003eAgNO\u003csub\u003e3\u003c/sub\u003e, Fe(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e, Ammonium hydroxide purchased from Sigma-Aldrich. All the chemicals used in the study were of Analytical grade. Gas cylinders of NO\u003csub\u003e2\u003c/sub\u003e, LPG, NH\u003csub\u003e3\u003c/sub\u003e, SO\u003csub\u003e2\u003c/sub\u003e gas of 1000 ppm concentration were purchased from M/s. Shreya Enterprises Pvt. Ltd, India.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Methods\u003c/h2\u003e\n \u003cp\u003eAgFeO\u003csub\u003e2\u003c/sub\u003e was synthesised by the co-precipitation method [\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e]. 0.01M Silver nitrate and 0.05M Ferric Nitrate were dissolved in 100 ml Deionized water separately and mixed by stirring for 4 h at room temperature. The mixture was then heated at 70\u0026deg;C for 1 hr. pH of the solution was adjusted to 12 using 0.01M Sodium hydroxide solution and further stirred overnight to obtain a red-brown precipitate. Precipitate was filtered, washed and then sonicated for 10 mins with deionized water followed by drying at 70\u0026deg;C. The ruby red powder was then annealed at 400\u0026deg;C for 4 hrs to remove extraneous matter. A smooth and thin film of as-prepared AgFeO\u003csub\u003e2\u003c/sub\u003e was deposited over a glass substrate by using doctor blade method [\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Characterisation\u003c/h2\u003e\n \u003cp\u003eStructural characterization of AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles was performed on X-Ray diffractometer (X\u0026rsquo;pert Pro PANalytical). Average particle size was determined by Debey-Schrrer equation. Morphological characteristics were examined using high-resolution transmission electron microscopy (HRTEM) equipped with selected area electron diffraction (Tecnai G2, F30 HRTEM-300kV) and field emission scanning electron microscopy (FEI-Quanta FEG 200F) along with energy dispersive spectroscopy (EDS). The specific surface areas were measured by the N\u003csub\u003e2\u003c/sub\u003e adsorption/desorption isotherm (Micrometrics ASAP 2020 Porosimeter) Brunauer-Emmett-Teller (BET) technique.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 Gas sensing measurement\u003c/h2\u003e\n \u003cp\u003eGas sensing measurements for NO\u003csub\u003e2\u003c/sub\u003e gas were conducted using a gas sensing unit comprised of a stainless-steel cylindrical chamber with inlet and outlet gas valves. The chamber is airtight with silicone rubber, and a heater is attached to the bottom. The gas sensing element holder with adjustable contacts was arranged inside the 250 cc volume capacity chamber. [\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e]. Resistance of the sensing element was measured with respect to time using a RIGOL (DM3058) digital multimeter.\u003c/p\u003e\n \u003cp\u003eAgFeO\u003csub\u003e2\u003c/sub\u003e-coated glass substrate having a 1 cm\u003csup\u003e2\u003c/sup\u003e area was used for the gas sensing measurements. Two electrical contacts of silver paste were drawn on the surface. After stabilizing the resistance of the sensing element at an optimized temperature, the resistance of the sensor was measured with respect to time in the atmospheric air and the targeted gas conditions. The gas response (%) is calculated for the material mentioned as follows.[\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e] (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e)\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eCalculation of Gas response for p-type and n-type material for oxidizing and reducing gas\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaterial\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003eGas response (%) formula used for\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eEq.\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ep-type\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eoxidizing gas\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\frac{{\\text{R}}_{\\text{a}\\text{i}\\text{r}}-{\\text{R}}_{\\text{g}\\text{a}\\text{s}}}{{\\text{R}}_{\\text{g}\\text{a}\\text{s}}} \\times 100 \\text{%}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\"\u003e\u003cp\u003eReducing gas\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\frac{{\\text{R}}_{\\text{g}\\text{a}\\text{s}}-{\\text{R}}_{\\text{a}\\text{i}\\text{r}}}{{\\text{R}}_{\\text{a}\\text{i}\\text{r}}} \\times 100 \\text{%}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(1)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003en-type\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eoxidizing gas\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\frac{{\\text{R}}_{\\text{g}\\text{a}\\text{s}}-{\\text{R}}_{\\text{a}\\text{i}\\text{r}}}{{\\text{R}}_{\\text{a}\\text{i}\\text{r}}} \\times 100 \\text{%}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\"\u003e\u003cp\u003eReducing gas\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\frac{{\\text{R}}_{\\text{a}\\text{i}\\text{r}}-{\\text{R}}_{\\text{g}\\text{a}\\text{s}}}{{\\text{R}}_{\\text{g}\\text{a}\\text{s}}} \\times 100 \\text{%}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eHere R\u003csub\u003egas\u003c/sub\u003e represents the resistance in the presence of the target gas, and R\u003csub\u003eair\u003c/sub\u003e represents the resistance in ambient air [\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Material characterization\u003c/h2\u003e \u003cp\u003eTypical indexed XRD pattern of AgFeO\u003csub\u003e2\u003c/sub\u003e is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. All the reflections matched to the data in JCPDS file 75-2147. None of the reflection indicated presence of impurities like Ag or Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in the spectra. The peaks in the pattern were corresponded to the delafossite structure indicating presence of both polytypes rhombohedral, \u003cem\u003e3R\u003c/em\u003e (Space group \u003cem\u003eR-3m\u003c/em\u003e) and hexagonal, \u003cem\u003e2H\u003c/em\u003e (Space group: \u003cem\u003eP6\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/mmc\u003c/em\u003e) respectively [\u003cspan additionalcitationids=\"CR36\" citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. The average crystallite size calculated by Debey Scherrer equation was 47nm. AgFeO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003cp\u003eThis non-stoichiometric compound is unstable at high temperature and decomposed to form secondary phases of Ag and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. This observation is in agreement with the previous published studies by Murthy \u003cem\u003eet al\u003c/em\u003e and Siedliska \u003cem\u003eet al\u003c/em\u003e [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFE-SEM micrograph in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea exhibits the dense distribution of slightly elongated nanoparticles of AgFeO\u003csub\u003e2\u003c/sub\u003e. EDS spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) confirms the elemental composition of AgFeO\u003csub\u003e2\u003c/sub\u003e with a weight percentage of Ag, Fe and O as 23.6%, 30.6% and 45.8% respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA typical HRTEM image of AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea) represents its microstructure and crystallographic details. Uniform, grain-like nanostructures having a breadth of ~\u0026thinsp;50 nm and length of ~\u0026thinsp;80 nm were seen in TEM analysis. This observation is consistent with XRD data. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb represents SAED pattern of AgFeO\u003csub\u003e2\u003c/sub\u003e nanograins that reveals the polycrystalline nature of the nanoparticles. d-spacing values were calculated using ImageJ software application. The diffraction rings were indexed to the lattice parameters 006, 101, 105 and 110 of rhombohedral/hexagonal crystal planes of the delafossite structure of AgFeO\u003csub\u003e2\u003c/sub\u003e and agreed with the peaks in XRD spectra.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTotal pore volume and BET surface area are the important features of cathode/anode material. Pore size distribution and pore diameter describe the porous nature of the material. The nitrogen adsorption-desorption isotherms were used to obtain information about the BET specific surface area and pore size distribution. Adsorption isotherm in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea revealed the facts that the hysteresis loop is at relative pressure (P/P\u003csub\u003e0\u003c/sub\u003e) close to unity, type IV hysteresis ascribed the presence of mesopores, H\u003csub\u003e1\u003c/sub\u003e hysteresis ascribed the presence of well-defined pore structure (IUPAC classification) and specific surface area was found to be 31.9353\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1551 m\u0026sup2;/g. Broad BJH pore size distribution was in the range of 1.7\u0026ndash;40 nm indicating the presence of mesoporous nanoparticles. The total pore volume was found to be 0.21 cm\u0026sup3; g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. These results were highly consistent to our previous research work on AgFeO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Gas sensing measurements\u003c/h2\u003e \u003cp\u003eThe gas-sensing properties of AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles were evaluated through a change in resistance when exposed to the target gases. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (a) shows the gas sensing of the AgFeO\u003csub\u003e2\u003c/sub\u003e sensor at an operating temperature of 50\u0026deg;C with a response time of 51 s. and recovery time of approximately 40% at 1000 s. After stabilizing the resistance of the AgFeO\u003csub\u003e2\u003c/sub\u003e gas sensor, the 8 ppm of NO\u003csub\u003e2\u003c/sub\u003e gas is purged into the gas sensing chamber [i.e., Gas ON]. After the \u0026lsquo;Gas ON\u0026rsquo; condition, the change in the resistance of the sensor was measured with respect to time. In this case, when the oxidizing gas [NO\u003csub\u003e2\u003c/sub\u003e] is used as the targeted gas, the resistance of the film decreases. It shows that the film is a \u0026lsquo;p-type\u0026rsquo; in nature, therefore, all calculations were made using Eq.\u0026nbsp;(1). The response time is calculated and schematically represented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (a).\u003c/p\u003e \u003cp\u003eThe operating temperature for the AgFeO\u003csub\u003e2\u003c/sub\u003e gas sensor was optimized using gas concentration 8 ppm at different temperatures, 50\u0026deg;C, 75\u0026deg;C, and 100\u0026deg;C viz. The recorded gas responses (%) were observed 1.885%, 1.151%, and 1.149%, respectively. The Eq.\u0026nbsp;(1) is used for the calculation of gas response (%). The highest gas response of 1.885% was achieved at an operating temperature of 50\u0026deg;C with a response time of 51 s. and approximately 40% recovery at 1000 s. This result suggests that the AgFeO\u003csub\u003e2\u003c/sub\u003e gas sensor performs optimally when detecting NO\u003csub\u003e2\u003c/sub\u003e gas at 50\u0026deg;C. Further, all subsequent gas sensing measurements for the AgFeO\u003csub\u003e2\u003c/sub\u003e gas sensor were carried out at the optimum operating temperature of 50\u0026deg;C.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (a \u0026amp; b) illustrates the normalized gas response (%) and a histogram showing the performance of the AgFeO\u003csub\u003e2\u003c/sub\u003e gas sensor under varying NO\u003csub\u003e2\u003c/sub\u003e gas concentrations, ranging from 8 to 20 ppm at optimum temperature (50\u0026deg;C). The gas response (%) values for 8, 12, 16, and 20 ppm of NO\u003csub\u003e2\u003c/sub\u003e gas are 1.88%, 3.06%, 5.45%, and 7.77%, respectively.\u003c/p\u003e \u003cp\u003eThis observed trend clearly indicates that as the concentration of NO\u003csub\u003e2\u003c/sub\u003e gas increases, there is a gradual augmentation in the gas response (%). This phenomenon can be attributed to the behaviour of NO\u003csub\u003e2\u003c/sub\u003e gas molecules when gas is injected on the surface of the AgFeO\u003csub\u003e2\u003c/sub\u003e sensor. Upon contact, these molecules tend to adhere to the sensor's surface. With an escalation in the concentration of NO\u003csub\u003e2\u003c/sub\u003e gas, there is a greater availability of gas molecules for adhesion, resulting in an increased number of interactions between the gas molecules and the sensor's surface.\u003c/p\u003e \u003cp\u003eAt higher gas concentrations, a larger proportion of active sites on the AgFeO\u003csub\u003e2\u003c/sub\u003e sensor's surface become occupied by the gas molecules. [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] Consequently, this leads to a higher surface coverage of gas molecules, subsequently producing a stronger gas response from the sensor. [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e] In essence, the sensor exhibits an increase in gas adsorption at elevated concentrations, accompanied by intensified interaction between the targeted gas molecules and the sensor's surface.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe response time for the AgFeO\u003csub\u003e2\u003c/sub\u003e gas sensor at various gas concentrations is summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. It was observed that the response time reduces with the increase in the concentration of NO\u003csub\u003e2\u003c/sub\u003e gas. This behaviour can be attributed to the several factors influencing the sensor's response time. At higher gas concentrations, there can be an accumulation of gas molecules near the sensor, resulting in a quick response time due to enhanced diffusion rates. Additionally, the response time may be contingent upon the degree of active site occupation by gas molecules on the sensor's surface. Variations in gas concentrations can lead to differences in surface coverage, thereby affecting the response time. The longer recovery time is attributed to slow surface reaction. However, there is scope to improve it by introducing metal catalysts through doping. [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eGas response (%), response time of thin film of AgFeO\u003csub\u003e2\u003c/sub\u003e nanograins at different concentrations of NO\u003csub\u003e2\u003c/sub\u003e gas\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=\"char\" char=\".\" 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\u003eThe concentration of NO\u003csub\u003e2\u003c/sub\u003e gas (ppm).\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGas Response (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eResponse time (S)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e44\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e37\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFurthermore, the specific properties of the AgFeO\u003csub\u003e2\u003c/sub\u003e sensor, including its size, shape, and surface characteristics, can exert an influence on the adsorption and desorption processes. These sensor attributes contribute to the observed disparities in response times across different gas concentrations.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e shows the selectivity of the AgFeO\u003csub\u003e2\u003c/sub\u003e gas sensor towards different gases. To assess selectivity, we conducted tests on the AgFeO\u003csub\u003e2\u003c/sub\u003e gas sensor at an operating temperature of 50\u0026deg;C. The sensor's sensitivity to various target gases, including NO\u003csub\u003e2\u003c/sub\u003e, LPG, NH3, acetone and SO\u003csub\u003e2\u003c/sub\u003e, was evaluated, yielding response percentages of 1.88%, 0.14%, 0.0%, 0.0%, and 0.0%, respectively.\u003c/p\u003e \u003cp\u003eAmong these gases, the AgFeO\u003csub\u003e2\u003c/sub\u003e sensor displayed its highest sensitivity, reaching 1.88%, specifically to NO\u003csub\u003e2\u003c/sub\u003e gas. This response to NO\u003csub\u003e2\u003c/sub\u003e gas was remarkably 12 times greater than its response to LPG. Conversely, the sensor exhibited relatively weak responsiveness to the other targeted gases, rendering them non-measurable. This observation underscores the outstanding selectivity of the AgFeO\u003csub\u003e2\u003c/sub\u003e sensor towards NO\u003csub\u003e2\u003c/sub\u003e gas, particularly at lower operating temperatures.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Gas sensing mechanism\u003c/h2\u003e \u003cp\u003eThe gas sensing results in a change in resistance because of the chemisorption and desorption process of oxygen present in the air and the target gas on the surface of the sensor. As mentioned in the literature, AgFeO\u003csub\u003e2\u003c/sub\u003e has a narrow band gap. [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e] During the gas sensing, the electrons are transferred from the conduction band of AgFeO\u003csub\u003e2\u003c/sub\u003e to oxygen resulting in the formation of negative oxygen ions according to the following reactions [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eO\u003csub\u003e2\u003c/sub\u003e (air) \u0026rarr; O\u003csub\u003e2\u003c/sub\u003e(ads) (1)\u003c/p\u003e \u003cp\u003eO\u003csub\u003e2\u003c/sub\u003e (ads)\u0026thinsp;+\u0026thinsp;e\u003csup\u003e\u0026minus;\u003c/sup\u003e \u0026rarr; O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e (ads) (2)\u003c/p\u003e \u003cp\u003eO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e (ads)\u0026thinsp;+\u0026thinsp;e \u0026minus; \u0026rarr; 2O\u003csup\u003e\u0026minus;\u003c/sup\u003e(ads) (3)\u003c/p\u003e \u003cp\u003eO \u003csup\u003e\u0026minus;\u003c/sup\u003e (ads)\u0026thinsp;+\u0026thinsp;e \u0026minus; \u0026rarr; O\u003csup\u003e2\u0026minus;\u003c/sup\u003e(ads) (4)\u003c/p\u003e \u003cp\u003eAs a result, the width of the depletion layer increases which leads to increase in resistance. When NO\u003csub\u003e2\u003c/sub\u003e is injected into the gas chamber, it is adsorbed on the AgFeO\u003csub\u003e2\u003c/sub\u003e surface, and being a strong oxidising gas, it donates holes and accepts both the negative oxygen ions (O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e, O\u003csup\u003e\u0026minus;\u003c/sup\u003e, O\u003csup\u003e2\u0026minus;\u003c/sup\u003e) and electrons from the layer and undergo the following reactions -\u003c/p\u003e \u003cp\u003eNO\u003csub\u003e2\u003c/sub\u003e (gas) \u0026rarr; NO\u003csub\u003e2\u003c/sub\u003e (ads) (5)\u003c/p\u003e \u003cp\u003eNO\u003csub\u003e2\u003c/sub\u003e (ads)\u0026thinsp;+\u0026thinsp;O\u003csup\u003e\u0026minus;\u003c/sup\u003e (ads)\u0026thinsp;+\u0026thinsp;2e\u003csup\u003e\u0026minus;\u003c/sup\u003e \u0026rarr; NO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e (ads)\u0026thinsp;+\u0026thinsp;O\u003csup\u003e2\u0026minus;\u003c/sup\u003e (ads) (6)\u003c/p\u003e \u003cp\u003eNO\u003csub\u003e2\u003c/sub\u003e (ads)\u0026thinsp;+\u0026thinsp;e\u003csup\u003e\u0026minus;\u003c/sup\u003e \u0026rarr; NO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e (7)\u003c/p\u003e \u003cp\u003eThis process results in thinning of the electron depletion layer and therefore, decrease in the sensor\u0026rsquo;s resistance. [\u003cspan additionalcitationids=\"CR45 CR46\" citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e] This variation in resistance is used for the detection of NO\u003csub\u003e2\u003c/sub\u003e gas.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn summary, we first time demonstrated the gas sensing properties of delafossite-structured AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles towards NO\u003csub\u003e2\u003c/sub\u003e gas. Grain-like AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles were prepared by simple co-precipitation method and well-characterized by XRD, FESEM, HRTEM and BET surface area. The nanoparticles showed high selectivity and excellent sensitivity to NO\u003csub\u003e2\u003c/sub\u003e gas with maximum gas response of 1.885% for 8 ppm of NO\u003csub\u003e2\u003c/sub\u003e gas at an operating temperature of 50\u0026deg;C, with a response time of 51 s. This study presents an approach for utilizing AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles as a low-cost, p-type semiconducting material for the development of NO\u003csub\u003e2\u003c/sub\u003e gas sensors at low temperature.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflict of interest:\u003c/strong\u003e The authors report no conflicts of interest.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval:\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material:\u003c/strong\u003e All pertinent information is presented within the manuscript and material is available upon request from the corresponding author.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eValmik, L. \u0026amp; Sultana, T., Impact of urbanization, industrialization, electrification and renewable energy on the environment in BRICS: fresh evidence from novel CS-ARDL model. 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Materials Science in Semiconductor Processing, (2020), 107, 104865. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.mssp.2019.104865\u003c/span\u003e\u003cspan address=\"10.1016/j.mssp.2019.104865\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\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":"journal-of-nanoparticle-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nano","sideBox":"Learn more about [Journal of Nanoparticle Research](http://link.springer.com/journal/11051)","snPcode":"11051","submissionUrl":"https://submission.nature.com/new-submission/11051/3","title":"Journal of Nanoparticle Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"AgFeO2, gas sensor, NO2, low temperature, delafossite","lastPublishedDoi":"10.21203/rs.3.rs-3870485/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3870485/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eNitrogen Dioxide (NO\u003csub\u003e2\u003c/sub\u003e) gas monitoring has become increasingly important to ensure the safety of human lives and the environment. The present study investigates the potential of low-cost delafossite-structured AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles to detect NO\u003csub\u003e2\u003c/sub\u003e gas at low temperature. Highly porous, grain-like AgFeO\u003csub\u003e2\u003c/sub\u003e nanoparticles were prepared by simple co-precipitation method and characterized using XRD, FESEM-EDS, TEM and BET analysis.AgFeO\u003csub\u003e2\u003c/sub\u003e nanograins synthesized by conventional method, demonstrated gas-sensing performance with respect to sensitivity (1.89%), short response (51s) and, selectivity at low temperature of 50 \u003csup\u003eo\u003c/sup\u003eC, towards 8 ppm NO\u003csub\u003e2\u003c/sub\u003e gas.\u003c/p\u003e","manuscriptTitle":"Low Temperature NO2 Gas Sensing by Delafossite-Structured AgFeO2 Nanograins","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-22 12:53:38","doi":"10.21203/rs.3.rs-3870485/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-02-25T20:41:21+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-01-29T02:23:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"6031b9c7-b0cd-40c3-a6d1-85733d1919ac","date":"2024-01-28T05:48:18+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-01-28T04:16:06+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-01-21T15:33:36+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-01-19T04:52:37+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Nanoparticle Research","date":"2024-01-16T16:48:48+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-nanoparticle-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"nano","sideBox":"Learn more about [Journal of Nanoparticle Research](http://link.springer.com/journal/11051)","snPcode":"11051","submissionUrl":"https://submission.nature.com/new-submission/11051/3","title":"Journal of Nanoparticle Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"23e54b10-0ab6-4288-939e-41918dec2b76","owner":[],"postedDate":"January 22nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-06-19T02:57:39+00:00","versionOfRecord":[],"versionCreatedAt":"2024-01-22 12:53:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3870485","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3870485","identity":"rs-3870485","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}