Eu3+-ion doped strontium molybdate perovskite quantum dots as a turn-off-on fluorescent sensor for simultaneous detection of hypoxanthine biomarker and Fe3+ ions.

A fluorescence "turn-off-on" nanoprobe is designed by using europium-doped strontium molybdate perovskite quantum dots (Eu3+:SMO PQDs) for the sequential detection of hypoxanthine (Hx) and Fe3+. The Eu3+:SMO PQDs were prepared by the sol-gel method using Sr(NO3)2, (NH4)6Mo7O24.4H2O, and Eu(OCOCH3)3 as precursors. The green fluorescence of Eu3+:SMO PQDs was efficiently reduced (turn-off) in the presence of Hx, then it was restored (turn-on) gradually by introducing Fe3+ due to the competitive formation of Hx@Fe3+, which results to the release of Eu3+:SMO PQDs. In addition, the fluorescent probe exhibits excellent selectivity and sensitivity. Under the optimized experimental conditions, linear ranges and detection limits were 0.25-25 μM and 12.30 nM for Hx and 0.025-50 μM and 10.44 nM for Fe3+ , respectively. Furthermore, the fluorescence method was successfully explored to detect Hx and Fe3+ in plasma and urine samples.