▎ 摘　　要

Two-dimensional (2D) reduced graphene oxide-carbon dot (rGO-CD) hybrids were synthesized via a green one-pot method, in which the reduction of GO is accompanied by in situ generation of CDs with ultra-small sizes of 3-8 nm on its surface. The introduction of CDs enhanced the gas sensing properties by similar to 3.3 times compared to bare rGO, and the rGO-CD hybrids could detect an extremely low NO2 concentration (10 ppb) at room temperature. Upon exposure to 25 ppm NO2 at room temperature, the as-prepared rGO-CDs show a sensitivity of similar to 120% and exhibit excellent selectivity for NO2. After six consecutive gas sensing tests or unencapsulated storage for 90 days, the rGO-CD hybrids still retained their sensing characteristics. The enhanced gas sensing properties of the rGO-CDs can be attributed to the increased hole density on the surfaces of rGO due to the introduction of CDs as well as the formation of all-carbon nanoscale heterojunctions with few residual N atoms, significantly promoting charge transfer. It is believed that this low-cost and environmental strategy provides a facile route to design and fabricate a high sensitivity, stability and repeatability NO2 gas sensor based on 2D materials.