Functional Nanomaterials, Institute for Materials Science, Kiel University , Kaiserstrasse 2, D-24143, Kiel, Germany.
Department of Microelectronics and Biomedical Engineering, Technical University of Moldova , 168 Stefan cel Mare Avenue, MD-2004 Chisinau, Republic of Moldova.
ACS Appl Mater Interfaces. 2017 Feb 1;9(4):4084-4099. doi: 10.1021/acsami.6b11337. Epub 2017 Jan 23.
In this work, the exceptionally improved sensing capability of highly porous three-dimensional (3-D) hybrid ceramic networks toward reducing gases is demonstrated for the first time. The 3-D hybrid ceramic networks are based on doped metal oxides (MeO and ZnMeO, Me = Fe, Cu, Al) and alloyed zinc oxide tetrapods (ZnO-T) forming numerous junctions and heterojunctions. A change in morphology of the samples and formation of different complex microstructures is achieved by mixing the metallic (Fe, Cu, Al) microparticles with ZnO-T grown by the flame transport synthesis (FTS) in different weight ratios (ZnO-T:Me, e.g., 20:1) followed by subsequent thermal annealing in air. The gas sensing studies reveal the possibility to control and change/tune the selectivity of the materials, depending on the elemental content ratio and the type of added metal oxide in the 3-D ZnO-T hybrid networks. While pristine ZnO-T networks showed a good response to H gas, a change/tune in selectivity to ethanol vapor with a decrease in optimal operating temperature was observed in the networks hybridized with Fe-oxide and Cu-oxide. In the case of hybridization with ZnAlO, an improvement of H gas response (to ∼7.5) was reached at lower doping concentrations (20:1), whereas the increase in concentration of ZnAlO (ZnO-T:Al, 10:1), the selectivity changes to methane CH gas (response is about 28). Selectivity tuning to different gases is attributed to the catalytic properties of the metal oxides after hybridization, while the gas sensitivity improvement is mainly associated with additional modulation of the electrical resistance by the built-in potential barriers between n-n and n-p heterojunctions, during adsorption and desorption of gaseous species. Density functional theory based calculations provided the mechanistic insights into the interactions between different hybrid networks and gas molecules to support the experimentally observed results. The studied networked materials and sensor structures performances would provide particular advantages in the field of fundamental research, applied physics studies, and industrial and ecological applications.
在这项工作中，首次展示了高度多孔的三维（3-D）混合陶瓷网络对还原气体的传感性能得到了极大的提高。该 3-D 混合陶瓷网络基于掺杂金属氧化物（MeO 和 ZnMeO，Me=Fe、Cu、Al）和合金氧化锌四足（ZnO-T），形成了许多结和异质结。通过将金属（Fe、Cu、Al）微粒与通过火焰传输合成（FTS）生长的 ZnO-T 以不同的重量比（ZnO-T:Me，例如 20:1）混合，然后在空气中进行后续的热退火，可以实现样品形态的变化和不同复杂微结构的形成。气体传感研究表明，可以通过控制和改变/调整材料的选择性，来控制和改变/调整材料的选择性，这取决于 3-D ZnO-T 混合网络中添加的金属氧化物的元素含量比和类型。虽然原始的 ZnO-T 网络对 H 气体表现出良好的响应，但在与 Fe 氧化物和 Cu 氧化物混合的网络中，观察到选择性向乙醇蒸气变化/调整，同时最佳工作温度降低。在与 ZnAlO 混合的情况下，在较低的掺杂浓度（20:1）下达到了 H 气体响应的提高（至约 7.5），而 ZnAlO 浓度的增加（ZnO-T:Al，10:1），选择性变为甲烷 CH 气体（响应约为 28）。对不同气体的选择性调整归因于杂交后金属氧化物的催化特性，而气体灵敏度的提高主要与内置 n-n 和 n-p 异质结之间的电阻的额外调制有关，在吸附和脱附气体物种时。基于密度泛函理论的计算提供了对不同混合网络与气体分子相互作用的机制见解，以支持实验观察到的结果。所研究的网络材料和传感器结构的性能将在基础研究、应用物理研究以及工业和生态应用领域提供特定的优势。
