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In recent years, the potential use and development of acetone gas sensors in health monitoring and self-diagnostic applications has attracted increasing attention. Thus, accurate sensing of acetone is of crucial importance in the non-invasive diagnosis of diabetes. However, challenges remain in the detection of acetone, such as high concentrations detection limit, high operating temperature and slow response dynamics. Herein, vertically aligned Ce-doped mesoporous NiO nanowalls are prepared on Ag-Pd interdigitated electrode substrate using an in-situ growth method. The gas sensing performances show that the as-made 4 mol% Ce-doped NiO nanowalls has excellent gas response value (3.2) to 10 ppm acetone at a lower operating temperature (175 ℃) with fast adsorption and desorption equilibrium (13 s/7 s). Vertically aligned mesoporous NiO nanowalls doped by Ce element could pave the way for ultra-sensitive and low power consumption acetone gas sensors for breath gas detection. • Simple method: in situ growth method. • Excellent detection conditions: Low lower detection limits at lower temperatures. • The fast equilibrium of adsorption and desorption. [ABSTRACT FROM AUTHOR]

• The flower-like TiO 2 microspheres were synthesized by a tunable tetrabutyl titanate-assisted hydrothermal method. • The as-made gas sensors showed high sensitivity and selectivity to NH 3 at the room temperature. • The underlying mechanism for the high selectivity to NH 3 was discussed using DFT calculations. TiO 2 is proved to be a promising material in the detection of various hazardous gases at the high temperature. However, gas adsorption-diffusion capacity at the room temperature is limited by their insufficient specific surface area and surface active sites. Herein, we report a strategy to synthesis of flower-like TiO 2 microspheres assembled by nanosheets and characterize the selective adsorption of NH 3 by using density functional theory (DFT). The as fabricated flower-like TiO 2 microspheres show an outstanding gas sensitivities (∼122 to 50 ppm NH 3) and high selectivity for NH 3 detection at room temperature. The higher adsorption energy and smaller adsorption distance of NH 3 on TiO 2 (001) indicate the much stronger interaction NH 3 -TiO 2 system. The present studies provide useful gas sensing materials with fine morphologies for the development of high-performance room temperature NH 3 sensors. [ABSTRACT FROM AUTHOR]