A Novel Perovkite Nanocrystals-Based Photochromic Fluorescent Sensor for Facile, Selective, Sensitive, and Visualized Detection of 3,3′-Dichlorobenzidine and for Implicit Application to Real-Time and Visualized Monitoring of Pollutant Photocatalytic Degradation

3,3'-Dichlorobenzidine (DCB) is an important and widely used intermediate in manufacturing various industrial products; however, DCB is a Group 2B carcinogen and its photodegraded product of benzidine is classified as Group 1 carcinogen. So far, there are few sensing strategies aiming to detect DCB remaining in related industrial products and discharged into the human living environment for assessing its impact on human health in an easy, low-cost, and real-time way. In this work, we found that the recently emerging perovskite nanocrystals (PNCs) with many excellent physiochemical properties could act as both photocatalysts and photochromic materials in the photodegradation of DCB. Under UV irradiation, PNCs catalyze the photodegradation of DCB molecules into benzidine molecules and chloride ions (Cl^-), followed by significant fluorescence wavelength (color) change of PNCs due to ion-exchange between PNCs and the photogenerated Cl^-. Based on the catalytic photodegradation of DCB and photochromism of PNCs, a novel, facile, low-cost, and visualized fluorescent sensor has been developed for the real-time detection of DCB with high sensing selectivity and sensitivity. The novel PNCs-based photochromic fluorescent sensing strategy not only greatly improves the sensing selectivity by innovatively introducing photodegradation and photochromism into the construction of sensing interfaces but also may inspire the applications of the photochromic fluorescent sensors in real-time monitoring of the photodegradation of various environmental pollutants.