Surface functionalization of semiconducting metal oxides has emerged as a highly effective approach for enhancing their sensing capabilities. In the present work, the surface of randomly oriented zinc oxide (ZnO) nanowires is modified with an optimized thickness (7 nm) of magnesium oxide (MgO), which exhibits an exceptionally sensitive and selective behavior toward NO₂ gas, yielding a response of approximately 310 for 10 ppm concentration at room temperature. The synergistic interplay between ZnO and MgO leads to a remarkable 20-fold improvement in sensor response compared to a pristine ZnO film and allows the detection of concentrations as low as 50 ppb. The ZnO–MgO composite was characterized using X-ray diffraction (XRD), XPS, and SEM-EDS to gain structural, compositional, and morphological insights. The interaction of the NO₂ molecule with the sensor film was investigated using density functional theory (DFT) simulations, revealing that oxygen vacant sites on the MgO surface are most favorable for NO₂ adsorption, with an adsorption energy of −3.97 eV and a charge transfer of 1.74e toward NO₂. The XPS, photoluminescence (PL), and EPR measurements experimentally verified the presence of oxygen vacancies in the sensing material. The introduction of localized levels within the band gap by oxygen vacancies significantly promotes the interaction of gas molecules with these sites, which enhances the charge transfer toward NO₂ gas molecules. This augmentation has a profound influence on the space charge region at the ZnO–MgO interface, which is pivotal for modulating the charge transport in the ZnO layer, resulting in the substantial improvement of NO₂ response at room temperature.

中文翻译：

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释放定制 ZnO-MgO 纳米复合材料的潜力，以增强室温下 NO2 传感性能


半导体金属氧化物的表面功能化已成为增强其传感能力的高效方法。在本工作中，随机取向的氧化锌 （ZnO） 纳米线的表面用优化厚度 （7 nm） 的氧化镁 （MgO） 进行修饰，其对 NO₂ 气体表现出异常敏感和选择性的行为，在室温下对 10 ppm 浓度产生约 310 的响应。与原始 ZnO 薄膜相比，ZnO 和 MgO 之间的协同相互作用使传感器响应显著提高了 20 倍，并且可以检测低至 50 ppb 的浓度。使用 X 射线衍射 （XRD）、XPS 和 SEM-EDS 对 ZnO-MgO 复合材料进行表征，以获得结构、成分和形态学见解。使用密度泛函理论 （DFT） 模拟研究了 NO₂ 分子与传感器膜的相互作用，揭示了 MgO 表面的氧空位点最有利于 NO₂ 吸附，吸附能量为 -3.97 eV，电荷向 NO₂ 转移 1.74e。XPS、光致发光 （PL） 和 EPR 测量通过实验验证了传感材料中存在氧空位。氧空位在带隙内引入局部能级，显著促进了气体分子与这些位点的相互作用，从而增强了向 NO₂ 气体分子的电荷转移。这种增强对 ZnO-MgO 界面的空间电荷区域具有深远的影响，这对于调节 ZnO 层中的电荷传输至关重要，从而在室温下显着改善 NO₂ 响应。