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Recently, low-dimensional semiconducting metal oxide (SMO) nanostructures have revolutionized the concept of conventional SMO-based chemiresistive gas sensors owing to their unique catalytic, electrical, and optical properties. The elevated working temperature of SMO-based sensors can be lowered by incorporating carbonaceous materials. Herein, we report for the first time, the superior acetone sensing performance at room temperature (RT, 27 °C) using ceria (CeO2) quantum dots (QDs) (7 ± 1 nm)-decorated carbon nanotube (CNT)-based nanocomposites. A hydrothermally prepared CeO2 QDs/CNT mesoporous heterostructure with a high surface area (152 m2 g–1) exhibits an excellent response (G a/G g) of 10,890 at RT with an ultrafast response/recovery time (56 ms/22 ms) and high selectivity toward acetone. The study unveils that the nanocomposite possesses simultaneous full and partial recovery response transients which is modeled using a heterogeneous adsorption site-based Langmuir–Hinshelwood mechanism. Besides, the mesoporosity of the nanocomposite results in fast diffusion of acetone molecules which reduces the detection time and incorporation of highly conductive CNTs lowers the operating temperature. The presence of Ce3+ states confirms the existence of high oxygen vacancies in CeO2 QDs resulting in enhanced adsorption capabilities of the nanocomposite. Moreover, the multi nanojunctions between CeO2 QDs and CNTs have a strong influence on the enhanced RT acetone response value.

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