Magnetron‐sputtering inert‐gas condensation is an emerging technique offering single‐step, chemical‐free synthesis of nanoparticles with well‐defined morphologies optimized for specific applications. In this study, the authors report a flexible approach to produce Fe nanocubes as building blocks for high‐performance NO2 gas sensor devices, and hybrid FeAu nanocubes with magneto‐plasmonic properties. Considering that nucleation happens within a short distance from the sputtering target, the authors utilize the high‐permeability and resultant screening effect induced by magnetic Fe targets of various thicknesses to manipulate the magnetic field configuration and plasma confinement. The authors thus readily switch from bimodal to single‐Gaussian size distributions of Fe nanocubes by modifying their primordial thermal environments, as explained by a combination of modeling methods. Simultaneously, the authors obtain a material yield increase of more than one order of magnitude compared to experiments using postgrowth mass filtration. The effectiveness of the method is demonstrated by the deposition of Fe nanocubes on microhotplate devices, leading to unprecedented NO2 detection performance for Fe‐based chemoresistive gas sensors. The exceedingly low detection limit down to 3 ppb is attributed to a morphological change in operando from Fe/Fe‐oxide core/shell to specific hollow‐nanocube structures, as revealed by in situ environmental transmission electron microscopy.

We report on local CuO nanowire growth on microhotplates combined with in situ measurement of the electrical resistance for well-controlled integration into conductometric gas sensing devices. Discrete current steps were observed during the CuO nanowire synthesis process, which is attributed to individual nanowire connections being formed. The high gas sensitivity of the CuO nanowire devices was confirmed by detection of carbon monoxide CO in the low ppm-level concentration range. Furthermore, we demonstrate that CuO nanowire growth inside a gas measurement setup allows studies on gas sensor poisoning/deactivation processes. A significant decrease of CO response was found after controlled exposure to humidity, which suggests sensor deactivation by surface hydroxylation. Thus our approach could be a novel and simple way for revealing new insights in various gas sensor degradation mechanisms in the future and might be also adapted for different metal oxide nanomaterials.