Progressive NO₂ Sensors with Rapid Alarm and Persistent Memory‐Type Responses for Wide‐Range Sensing Using Antimony Triselenide Nanoflakes

Abstract

Abstract Antimony triselenide (Sb 2 Se 3 ) nanoflake‐based nitrogen dioxide (NO 2 ) sensors exhibit a progressive bifunctional gas‐sensing performance, with a rapid alarm for hazardous highly concentrated gases, and an advanced memory‐type function for low‐concentration (<1 ppm) monitoring repeated under potentially fatal exposure. Rectangular and cuboid shaped Sb 2 Se 3 nanoflakes, comprising van der Waals planes with large surface areas and covalent bond planes with small areas, can rapidly detect a wide range of NO 2 gas concentrations from 0.1 to 100 ppm. These Sb 2 Se 3 nanoflakes are found to be suitable for physisorption‐based gas sensing owing to their anisotropic quasi‐2D crystal structure with extremely enlarged van der Waals planes, where they are humidity‐insensitive and consequently exhibit an extremely stable baseline current. The Sb 2 Se 3 nanoflake sensor exhibits a room‐temperature/low‐voltage operation, which is noticeable owing to its low energy consumption and rapid response even under a NO 2 gas flow of only 1 ppm. As a result, the Sb 2 Se 3 nanoflake sensor is suitable for the development of a rapid alarm system. Furthermore, the persistent gas‐sensing conductivity of the sensor with a slow decaying current can enable the development of a progressive memory‐type sensor that retains the previous signal under irregular gas injection at low concentrations.