Rapid and real-time monitoring of food quality plays critical roles in the food industry and for the general public health.Herein,we specially synthesized a new perylene bisimide (PBI) derivative (PCB-EpE) composed of two PBI units and a rigid o-carborane linker,which was further employed in constructing a conceptual fluorescent film sensor for evaluating fish freshness.Photophysical studies indicate that PCB-EpE displays an open “Z-type” molecular configuration in chloroform and a closed “△-type” configuration in methyl cyclohexane.Comparatively,“Z-type” molecular configuration possesses higher fluorescence quantum yield and is more sensitive toward volatile basic nitrogen (VBN).It is noteworthy that the film sensor responds in less than 1 s even in ambient humidity condi-tion.High correlation between the content of total volatile basic nitrogen (TVB-N)in evaluating fish freshness withdifferent storage time and the fluorescence response s ach eved Detect on im t of the f m sensor toward trmethy am ne as an example is lower than 2.6 mg/m3.Comprehensive sensing investigations demonstrate the rapid detection,strong anti-interference capability and ex-cellent reusability of the film sensor toward testing VBN.To our knowledge,this is the first report to accurately predict TVB-N value for the evaluation of fish freshness using a fluorescent film sensor,showing great potential for real-life applications.