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 (Ra/Rg = 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.