Conjugated polymer-grafted silica nanoparticles were prepared by Sonogashira coupling reaction involving a two-step procedure. The resulting conjugated polymer-grafted silica nanoparticles were characterized by infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and absorption and fluorescence spectroscopy. The conjugated polymer-grafted silica nanoparticles are highly fluorescent, and the fluorescent response of the nanoparticles of different size towards electron-deficient trinitrotoluene (TNT) was studied by examining how the steady state fluorescence intensity changes with the concentration of TNT. The conjugated polymer-grafted silica nanoparticles show high sensitivity toward TNT, with a detection limit down to 1 μM.