Silica　aerogels　functionalized　with　strongly　fluorescent　carbon　quantum　dots　were　first　prepared　and　used　for　simple,　sensitive,　and　selective　sensing　of　NO2　gas.　In　the　presence　of　ethanol,　homemade　silica　aerogels　with　a　large　specific　surface　area　of　801.17　m(2)/g　were　functionalized　with　branched　polyethylenimine-capped　quantum　dots　(BPEI-CQDs)　with　fluorescence　quantum　yield　higher　than　40%.　The　prepared　porous　CQD-aerogel　hybrid　material　could　maintain　its　excellent　fluorescence　(FL)　activity　in　its　solid　state.　The　FL　of　CQD-aerogel　hybrid　material　could　be　selectively　and　sensitively　quenched　by　NO2　gas,　suggesting　a　promising　application　of　the　new　FL-functionalized　aerogels　in　gas　sensing.