A novel fluorescent probe, NAP-TPP, derived from 1,4-naphthalic anhydride with an iminophosphorane group, enables sequential detection of Sn²⁺ and moisture. It shows a clear fluorescence/colorimetric response upon Sn²⁺ binding and acts as a ratiometric moisture sensor. NAP-TPP also images Cu²⁺ in cells, highlighting its dual functionality and potential for bioanalytical and environmental applications.

Abstract

A novel small-molecule fluorescent probe, NAP-TPP, derived from 1,4-naphthalic anhydride and incorporating an iminophosphorane functionality, has been developed for the sequential detection of Sn²⁺ ions and moisture. This work represents the first investigation into the metal ion complexation capabilities of fluorescent iminophosphorane derivatives for sensing applications. Upon coordination with Sn²⁺, the probe undergoes a distinct fluorescence change accompanied by a visible colorimetric shift, indicative of complex formation. The probe exhibits excellent aqueous stability and further demonstrates the ability to visualize Cu²⁺ ions in various cultured cell lines. Notably, the Sn²⁺ complex formed under anhydrous conditions functions as a highly sensitive ratiometric fluorescent sensor for trace levels of moisture. Collectively, these findings establish NAP-TPP as an effective dual-purpose sensing platform for detecting Sn²⁺ ions and monitoring moisture.