Designing a reliable sensor for indoor formaldehyde (HCHO) with high sensitivity and selectivity is crucial for environmental and health protection. This study reported HCHO sensors based on a nanoporous mixed-phase In₂O₃ nanoparticle. A combined cubic and orthorhombic phase In(OH)₃/InOOH [c-In(OH)₃/o-InOOH] precursor, synthesized through a facile solvothermal route at different temperatures, was annealed to prepare the In₂O₃ nanoparticle homojunction. The obtained In₂O₃, calcined at 350 °C, exhibited a porous structure and a large specific surface area of 81.46 cm³·g^–1, facilitating more number of active sites’ exposure for HCHO-sensing reactions. Results showed that the In₂O₃ calcined at 350 °C exhibited the best HCHO-sensing performances at 120 °C with a large response value (330–50 ppm), good selectivity, and a short response time (12 s). Additionally, its detection limit could reach 11 ppb. This HCHO gas sensing behavior was owing to the mixed-phase homojunction structure formed between cubic and rhombohedral In₂O₃, the large specific surface area, and the porous structure with abundant oxygen vacancies. This study indicated that the nanoporous mixed-phase In₂O₃ nanoparticles could be the potential candidates for rapidly detecting HCHO at low concentration levels under low power consumption.

中文翻译：

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用于甲醛传感的纳米多孔混合相 In2O3 纳米粒子同质结

设计具有高灵敏度和选择性的可靠的室内甲醛 (HCHO) 传感器对于环境保护和健康保护至关重要。本研究报告了基于纳米多孔混合相 In ₂ O ₃纳米颗粒的 HCHO 传感器。在不同温度下通过简便的溶剂热途径合成的立方相和正交相 In(OH) ₃ /InOOH [c-In(OH) ₃ /o-InOOH] 前体经过退火以制备 In ₂ O ₃纳米颗粒同质结。所得 In ₂ O _{3在 350 °C 下煅烧，具有多孔结构和 81.46 cm} ³ ·g ^–1的大比表面积，促进更多的活性位点暴露于 HCHO 传感反应。结果表明，在 350 °C 下煅烧的 In 2 O 3 在 120 °C 下表现出最佳的 HCHO 传感性能，具有较大的响应值（330–50 ppm）、良好的选择性和较短的响应时间（12 _s）_。此外，其检测限可达 11 ppb。这种HCHO气敏行为是由于立方和菱面体In ₂ O ₃之间形成的混合相同质结结构、大的比表面积和具有丰富氧空位的多孔结构。该研究表明，纳米多孔混合相 In ₂ O ₃ nanoparticles could be the potential candidates for rapidly detecting HCHO at low concentration levels under low power consumption.