Dye-sensitized lanthanide-doped upconversion nanoprobe for enhanced sensitive detection of Fe³⁺ in human serum and tap water

Iron ion (Fe³⁺) detection is crucial for human health since it plays a crucial role in many physiological activities. In this work, a novel Schiff-base functionalized cyanine derivative (CyPy) was synthesized, which was successfully assembled on the surface of upconversion nanoparticles (UCNPs) through an amphiphilic polymer encapsulation method. In the as-designed nanoprobe, CyPy, a recognizer of Fe³⁺, is served as energy donor and β-NaYF₄:Yb,Er upconversion nanoparticles are adopted as energy acceptor. As a result, a 93-fold enhancement of upconversion luminescence is achieved. The efficient energy transfer from CyPy to β-NaYF₄:Yb,Er endows the nanoprobe a high sensitivity for Fe³⁺ in water with a low detection limit of 0.21 μM. Moreover, the nanoprobe has been successfully applied for Fe³⁺ determination in human serum and tap water samples with recovery ranges of 95 %-105 % and 97 %-106 %, respectively. Moreover, their relative standard deviations are all below 3.72 %. This work provides a sensitive and efficient methodology for Fe³⁺ detection in clinical and environmental testing.