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<p>This study presents the synthesis and characterization of flower-like zinc oxide (ZnO) hexagonal nanorods developed via the chemical bath deposition (CBD) method at varying precursor concentrations of 0.05, 0.075, 0.1, and 0.125&#xa0;M. X-ray diffraction (XRD) analysis confirmed the formation of a wurtzite hexagonal crystal structure with a preferred orientation along the (002) plane, while scanning electron microscopy (SEM) revealed vertically aligned, flower-like nanorods with well-defined pores. The description of “well-defined pores” refers to inter-rod and intercolumnar voids formed between vertically aligned ZnO nanorods, as directly observed in high-magnification FESEM images. These pores are morphological in origin rather than intrinsic mesopores within individual nanorods. Atomic force microscopy (AFM) indicated a maximum surface roughness of 189.1&#xa0;nm for the 0.1&#xa0;M sample, suggesting an enhanced surface area beneficial for gas interaction. X-ray photoelectron spectroscopy (XPS) further validated the chemical composition through distinct Zn 2p<sub>1/2</sub> and Zn-2p<sub>3/2</sub> spin–orbit peaks at 1044.90 and 1021.81&#xa0;eV, respectively. The gas sensing properties of the synthesized ZnO nanorods were systematically evaluated toward nitrogen dioxide (NO<sub>2</sub>) at various operating temperatures and concentrations. Remarkably, the 0.1&#xa0;M ZnO nanorods exhibited the highest sensitivity, achieving a 29.1% response to 100&#xa0;ppm NO<sub>2</sub> at 200&#xa0;°C, with a rapid response time of 13&#xa0;s and a recovery time of 147&#xa0;s. The material also demonstrated a detection limit of 20&#xa0;ppm, corresponding to the immediately dangerous to life or health (IDLH) threshold. The superior sensing behavior is attributed to the optimized morphology and surface states, as interpreted through the band bending model. Overall, this work underscores the potential of flower-like ZnO hexagonal nanorods as efficient and reliable NO<sub>2</sub> sensors operating at moderate temperatures, offering valuable insights into the structure–property relationship governing their sensing performance.</p>

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Rapid and sensitive NO2 detection using optimized flower-like ZnO nanorods synthesized via chemical bath deposition

  • 期刊论文

  • 发表日期：

    2026年7月17日

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  • Ravishankar R. Ambi,
  • Rohit D. Ghulanavar,
  • Aniket B. Pawar,
  • Moshim G. Mulla,
  • Ajit H. Deshmukh

摘要

This study presents the synthesis and characterization of flower-like zinc oxide (ZnO) hexagonal nanorods developed via the chemical bath deposition (CBD) method at varying precursor concentrations of 0.05, 0.075, 0.1, and 0.125 M. X-ray diffraction (XRD) analysis confirmed the formation of a wurtzite hexagonal crystal structure with a preferred orientation along the (002) plane, while scanning electron microscopy (SEM) revealed vertically aligned, flower-like nanorods with well-defined pores. The description of “well-defined pores” refers to inter-rod and intercolumnar voids formed between vertically aligned ZnO nanorods, as directly observed in high-magnification FESEM images. These pores are morphological in origin rather than intrinsic mesopores within individual nanorods. Atomic force microscopy (AFM) indicated a maximum surface roughness of 189.1 nm for the 0.1 M sample, suggesting an enhanced surface area beneficial for gas interaction. X-ray photoelectron spectroscopy (XPS) further validated the chemical composition through distinct Zn 2p1/2 and Zn-2p3/2 spin–orbit peaks at 1044.90 and 1021.81 eV, respectively. The gas sensing properties of the synthesized ZnO nanorods were systematically evaluated toward nitrogen dioxide (NO2) at various operating temperatures and concentrations. Remarkably, the 0.1 M ZnO nanorods exhibited the highest sensitivity, achieving a 29.1% response to 100 ppm NO2 at 200 °C, with a rapid response time of 13 s and a recovery time of 147 s. The material also demonstrated a detection limit of 20 ppm, corresponding to the immediately dangerous to life or health (IDLH) threshold. The superior sensing behavior is attributed to the optimized morphology and surface states, as interpreted through the band bending model. Overall, this work underscores the potential of flower-like ZnO hexagonal nanorods as efficient and reliable NO2 sensors operating at moderate temperatures, offering valuable insights into the structure–property relationship governing their sensing performance.