This　paper　reports　a　resonance　energy　transfer-amplifying　fluorescence　quenching　at　the　surface　of　silica　nanoparticles　for　the　ultrasensitive　detection　of　2,4,6-trinitrotoluene　(TNT)　in　solution　and　vapor　environments.　Fluorescence　dye　and　organic　amine　were　covalently　modified　onto　the　surface　of　silica　nanoparticles　to　form　a　hybrid　monolayer　of　dye　fluorophores　and　amine　ligands.　The　fluorescent　silica　particles　can　specifically　bind　TNT　species　by　the　charge-transfer　complexing　interaction　between　electron-rich　amine　ligands　and　electron-deficient　aromatic　rings.　The　resultant　TNT-amine　complexes　bound　at　the　silica　surface　can　strongly　suppress　the　fluorescence　emission　of　the　chosen　dye　by　the　fluorescence　resonance　energy　transfer　(FRET)　from　dye　donor　to　the　irradiative　TNT-amine　acceptor　through　intermolecular　polar-polar　interactions　at　spatial　proximity.　The　quenching　efficiency　of　the　hybrid　nanoparticles　with　TNT　is　greatly　amplified　by　at　least　10-fold　that　of　the　corresponding　pure　dye.　The　nanoparticle-assembled　arrays　on　silicon　wafer　can　sensitively　detect　down　to　similar　to　1　nM　TNT　with　the　use　of　only　10　mu　L　of　solution　(similar　to　2　pg　TNT)　and　several　ppb　of　TNT　vapor　in　air.　The　simple　FRET-based　nanoparticle　sensors　reported　here　exhibit　a　high　and　stable　fluorescence　brightness,　strong　analyte　affinity,　and　good　assembly　flexibility　and　can　thus　find　many　applications　in　the　detection　of　ultratrace　analytes.