Herein, we report the preparation of well characterized hierarchical CuO/ZnO heterostructures and demonstrate the versatility of this composite as a CO₂ gas sensor and a visible light catalyst for methylene blue (MB) degradation. 3D hierarchical ZnO spheres were decorated with CuO nanoleaves to form the interleaved p-CuO/n-ZnO hetero-surfaces. Subsequently, silver (Ag) functionalized composites were tested for their sensitivity and selectivity towards CO₂ gas as a core application. The nanostructured Ag@CuO/ZnO composite demonstrated an improved sensor response of 34% at 320 °C with response/recovery times of 76 and 265 s compared to the CuO/ZnO composite and control samples. Additionally, the Ag@CuO/ZnO composite displayed excellent recovery (97%), repeatability (96%), accuracy (86%), and lower baseline drifts with a co-efficient of variation (COV) of 4.5% measured over an extended period of 40 days towards 1000 ppm CO₂ gas for 10 individually tested sensors. In a parallel application as a photocatalyst, the CuO/ZnO composite was observed to degrade 98% methylene blue in 180 min with the first order rate constant (κ_app) found to be 6- and 75-fold greater, respectively, when compared to the ZnO and CuO samples under visible light irradiation. The gas sensing mechanism substantiated from in situ diffuse reflectance infra-red Fourier transform spectroscopy (DRIFTS) confirmed the formation of copper carbonate in the presence of CO₂. Interleaved assembly ensured the high mobility of electron–hole pairs with concerted efforts from a high effective surface area, multi-interleaved p/n nano-interfaces and the catalytic role of Ag. The confluence of these factors resulted in an improved CO₂ sensor response and photocatalytic performance.

中文翻译：

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使用CuO纳米叶调节交错式ZnO组件以实现多功能性能：持久的CO ₂气体传感器和可见光催化剂

本文中，我们报告了表征良好的分层CuO / ZnO异质结构的制备，并证明了该复合材料作为CO ₂气体传感器和亚甲基蓝（MB）降解的可见光催化剂的多功能性。用CuO纳米叶装饰3D分层ZnO球体，以形成交错的p-CuO / n-ZnO异质表面。随后，测试了银（Ag）功能化的复合材料对CO ₂的敏感性和选择性天然气为核心应用。与CuO / ZnO复合材料和对照样品相比，纳米结构的Ag @ CuO / ZnO复合材料在320°C时具有34％的改善的传感器响应，响应/恢复时间分别为76和265 s。此外，Ag @ CuO / ZnO复合材料具有优异的回收率（97％），可重复性（96％），准确性（86％）和较低的基线漂移，在长期使用中测得的变异系数（COV）为4.5％对于10个单独测试的传感器，在1000 ppm CO ₂气体下的测试时间为40天。在并行应用作为光催化剂，所观察到的的CuO / ZnO复合物以降解98％亚甲蓝在180分钟与一级速率常数（κ_应用）与可见光照射下的ZnO和CuO样品相比，分别增加了6倍和75倍。由原位漫反射红外红外傅里叶变换光谱（DRIFTS）证实的气体传感机制证实了在存在CO ₂的情况下碳酸铜的形成。交错的组装通过高有效表面积，多重交错的p / n纳米界面和Ag的催化作用共同努力，确保了电子-空穴对的高迁移率。这些因素的融合导致改善的CO ₂传感器响应和光催化性能。