Facile synthesis of magnetic intelligent sensors for the pH-sensitive controlled capture of Cr(vi)

Abstract

In this work, intelligent pH-sensitive sensors (Fe₃O₄/RhB@PAM) for Cr(VI) detection were successfully synthesized based on polyacrylamide (PAM) and Rhodamine B (RhB) co-modified Fe₃O₄ nanocomposites. The characterization results indicated that the sensors had many favorable properties, including suitable size, stable crystal structure and excellent magnetic response performance (47.59 emu g⁻¹). In addition, the fluorescence changes during the detection process indicated that Fe₃O₄/RhB@PAM were “ON–OFF” intelligent sensors. When the Fe₃O₄/RhB@PAM sensors were placed in acidic Cr(VI) solution (pH 4), PAM acted as a pH-responsive “gatekeeper” releasing RhB, and the fluorescence intensity of released RhB was weakened by the complexation of Cr(VI). Furthermore, the fluorescence changes of the magnetic sensors were remarkably specific for Cr(VI) even in the presence of other competitive cations, and the limit of detection (LOD) for Cr(VI) was lower (0.347 μM) than the value recommended by the World Health Organization (0.96 μM). All the results presented in this study showed that the Fe₃O₄/RhB@PAM sensors had significant potential for Cr(VI) detection in acidic environmental samples.