In this work amine functionalized silicon nanoparticles colloid is utilized to prepare a fluorescent probe for detecting low concentration levels of hypochlorite in water. The sensor is prepared by adding organosilane in silicon nanoparticles colloidal solution which freshly synthesized by laser ablation of silicon target in distilled water. The amine-terminated surface of silicon nanoparticles is confirmed using Fourier transform infrared, UV–vis absorption spectroscopy and transmission electron microscopy methods. The photoluminescence measurements of the functionalized silicon nanoparticles colloid exhibit high photostability and good reproducibility making them ideal fluorescent probes for sensing applications. It shows high sensitivity, excellent selectivity and rapid response (˜6 min) toward hypochlorite. The room temperature fluorescent sensor detects hypochlorite of water in the linear concentration range from 1 to 5 μM with a 0.2 μM detection limit. The sensor properties including high sensitivity, fast response and facile synthesis of the amine-functionalized silicon nanoparticles are compared with other reports in literature for fluorescent detection of hypochlorite in water.