Mixed-dimensional heterojunction by 3D CdS nanowire arrays bridged with 2D WSe2 for ultrafast photoelectric gas sensor

Heterojunctions are of essential importance for electronic sensors due to their unique properties at the junctions. However, a planar junction made of two-dimensional (2D) materials commonly suffers from slow response and irreversible recovery because of slow physisorption and desorption rates. Herein, we present a unique design of a mixed-dimensional heterojunction built from patterned growth of 3D n-type CdS nanowire arrays and p-type 2D WSe₂ nanosheets for photoelectric gas sensors. This heterojunction sensor showed highly selective and reversible responses to NO₂ and NH₃ with detection limits of 60 and 54 ppb, respectively, under UV illumination at room temperature. Notably, the sensor exhibited an ultrafast response time of less than 1 s to 1 ppm NO₂ and NH₃, which outperforms most previous reports. The hybrid junction structure proposed herein will pave the way for engineering new electronic devices from a broad selection of materials to achieve improved sensing performances at room temperature.