Highly responsive for ppb-level NO2 at room temperature

Surface-tunable metal oxides are attractive platforms for gas sensing at room temperature. Herein, a sensitive and selective NO 2 sensor was fabricated by chemically grafting aminopropyltriethoxysilane (APTES) onto CdS quantum dots (CdS QDs) deposited on TiO 2 nanotube arrays (TNTs). Compared with conventional metal-oxide sensing materials, CdS QDs provide abundant surface hydroxyl groups for APTES grafting, while the APTES layer contributes to humidity tolerance and NO 2 capture. Meanwhile, the TNTs/CdS QDs architecture provides shortened pathways for the transport of photogenerated charge carriers toward the APTES-functionalized interface. Consequently, under solar-light irradiation, the TNTs/CdS QDs/APTES sensor detects NO 2 down to 10 ppb (10 nmol mol −1 ) at room temperature, with response and recovery times of 5 s at this concentration. This strategy offers a facile route to the design of high-performance NO 2 sensors based on metal-oxide substrates for room-temperature operation.