Browsing by Author "Subramanian, A."

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    Defects Enriched p-type Zinc Stannate for Selective Detection of ppb-Level NO2 Gas at Ambient Temperature
    (American Chemical Society, 2024) Pawar, N.; Nath, V.G.; Rodney, J.D.; Joshi, S.; Subramanian, A.; Udayashankar, N.K.
    In this study, we explore the synthesis and gas-sensing capabilities of zinc stannate (Zn2SnO4) in three morphologies─spherical nanoparticles, urchins, and octahedrons─aiming to investigate the influence of morphology on sensing properties. The fabricated devices exhibit a significant resistance decrease upon exposure to NO2 at room temperature (24 °C), indicating p-type sensing behavior. Among these morphologies, the spherical nanoparticle-based sensor exhibits the highest sensor response of 57% to 6 ppm of NO2, outperforming urchins and octahedrons by approximately 1.2 and 4.1 times, respectively. This superior performance, with response and recovery times of 6.3 s and 224 s, is attributed to enhanced redox reactions from a larger surface area and a higher proportion of oxygen interstitials. The spherical nanoparticle-based sensor also demonstrates exceptional selectivity for NO2 over SO2, CO, NH3, and CH4, with a detection limit of 200 ppb. Furthermore, the sensor exhibits excellent reversibility with only 2% variation across 20 consecutive test cycles and demonstrates remarkable long-term stability, with a performance fluctuation of approximately 2.3% over 63 days without significant degradation. © 2024 American Chemical Society.
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    Mechanistic insight and first principle analysis of cation-inverted zinc ferrite nanostructure: A paradigm for ppb-level room temperature NOx sensor
    (Elsevier B.V., 2024) Nath, V.G.; Ray, S.; Rodney, J.D.; Prakasha Bharath, S.; Roy, S.; Tarafder, K.; Subramanian, A.; Chul Kim, B.
    Herein, we adopted a new paradigm for developing a high-performance gas sensor by leveraging the mixed spinel ZnFe2O4 structure (mZFO) to enhance the adsorption of NOx molecules. Material characterization reveals the formation of the mZFO due to the cation inversion in lattice sites. The estimated value of the inversion degree is observed to shift from 0.78 to 0.39 with an increase in the calcination temperature. The mZFO nanoparticles calcined at 500 °C show exceptional sensing performance due to their suitable grain size (∼2 times Debye length), neck diameter, and surface area. The sensing studies conducted at various NOx concentrations indicate that the sensor can detect ppb level of NOx with a detection limit of about 9 ppb at room temperature. The detailed sensing mechanism is elucidated based on the density functional theory calculations (DFT) and Bader charge analysis. The outstanding sensor performance is attributed to the formation of a mixed spinel structure, wherein the adsorption energy of NOx (∼-0.6 eV) in the presence of surface adsorbed oxygen is higher than that of the normal spinel structure (∼-0.1 eV). Furthermore, the sensor exhibited a fast response and recovery times (7 and 92 s at 800 ppb NO2), excellent stability, and selectivity. The practical suitability of the mZFO sensor was studied by analyzing the vehicle exhaust emissions. We strongly believe this work would pave a novel approach to developing a high-potential gas sensor by modifying the cation distributions in the spinel ferrites. © 2024 Elsevier B.V.