Ultrathin coordination polymer nanosheets modified with carbon quantum dots for ultrasensitive ammonia sensors

Exposure to ammonia (NH₃) is known harmful to health, environment and industrial facilities, hence it is important for the trace detection of NH₃. Herein, for the first time, ultrasensitive room temperature NH₃ sensors are realized by assembling carbon quantum dots (CQDs) on free-standing ultrathin coordination polymers (CPs) nanosheets (Co[Ni(CN)₄]) with an average thickness of ∼2.5 nm, which demonstrate excellent sensitivity (R_a/R_g = 87.7 to 30 ppm), fast gas response speed (∼10 s to 30 ppm), remarkable repeatability, high selectivity, good long-term stability and low limit of theoretical detection (∼8 ppb) toward NH₃ gas. The NH₃ gas sensor enhancement through incorporation of CQDs provides a simple and environment-friendly strategy for further improving sensor property of CPs nanosheets. This work provides an effective way to construct new electrode materials for high-performance gas sensor devices via the rational design.