Buffer‐Selective Rhodamine‐Based Fluorescent Sensor for Selective Cascade Detection of Aluminum, Mercury and Cyanide

ABSTRACT In this study, we present the synthesis and sensing applications of Rh‐BPh , a new rhodamine‐based fluorescent sensor prepared through a simple and efficient synthetic method. The probe Rh‐BPh responded only to aluminum (Al 3+ ) in DMSO/water (v/v:1/1). As the water content increased, it became responsive to both Al 3+ and mercury (Hg 2+ ). Buffer studies across pH 5–8 showed a clear pH dependence: Hg 2 + was detected mainly under acidic buffers, whereas Al 3 + was selectively detected in basic buffers The detection limits are 366 nM for Hg 2+ and 554 nM for Al 3+ . Interestingly, the reversible interactions between the complexes and CN − (with Al 3+ ) or I − (with Hg 2+ ) ions show a reversible ring‐opening/ring‐closure process and enable the creation of a three‐input OR‐INHIBIT molecular logic gate. Additionally, the Rh‐BPh‐Al 3+ complex functions as a “turn‐off” fluorescent probe for cyanide ions in aqueous media, with a detection limit of 497 nM. Complementary colorimetric analyses performed in HEPES and Tris buffers, as well as on filter paper, indicate that the probe can also act as a practical color‐based detection system. Simultaneously, the Rh‐BPh‐Al 3+ complex offers a reversible and specific method for detecting cyanide ions.