A new phenanthroimidazole-based uorescence probe for selective detection of HClO was synthesized and characterized using 1 HNMR, 13 CNMR, IR, and HRMS. With benzenesulfonohydrazide as the identi cation group, the probe demonstrated a fast uorescence response from yellow-green to blue when the HC = N double bond was oxidized and broken into an aldehyde group. The probe showed high selectivity and sensitivity towards HClO with approximately 4.5-fold uorescence enhancement and has been successfully applied in the molecular logic gates, determination of HClO in environmental water samples, and portable HClO detection.