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Microstructured single- and double-layered sensor devices based on p-type hydrogen-terminated nanocrystalline diamond (NCD) films and/or n-type ZnO nanorods (NRs) have been obtained via a facile microwave-plasma-enhanced chemical vapour deposition process or a hydrothermal growth procedure. The morphology and crystal structure of the synthesized materials was analysed with scanning electron microscopy, X-ray diffraction measurements and Raman spectroscopy. The gas sensing properties of the sensors based on i) NCD films, ii) ZnO nanorods, and iii) hybrid ZnO NRs/NCD structures were evaluated with respect to oxidizing (i.e., NO2, CO2) and reducing (i.e., NH3) gases at 150 °C. The hybrid ZnO NRs/NCD sensor showed a remarkably enhanced NO2 response compared to the ZnO NRs sensor. Further, inspired by this special hybrid structure, the simulation of interaction between the gas molecules (NO2 and CO2) and hybrid ZnO NRs/NCD sensor was studied using DFT calculations.

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Gas sensors based on a quartz crystal microbalance (QCM) coated with nanocrystalline diamond (NCD) were developed and tested on NH3, CO2, and humidity detection at room temperature and compared with the bare (uncoated) QCM. NCD films were directly grown on the QCM by a large‐area pulsed linear‐antenna microwave plasma CVD process from the CH4/CO2/H2 gas mixture at temperatures below 400 °C. The as‐grown NCD films on QCM and reference Si substrates were characterized by scanning electron and atomic force microscopies as well as Raman and optical spectroscopies. The NCD‐coated QCM gas sensors showed a reasonable performance with a stable repeatability to the tested gases. The response time of the tested diamond‐coated sensor was fast (∼5 s). Moreover, we also observed higher sensitivity and better stability for NCD‐coated QCM than for the bare QCM.

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