Molecularly imprinted sensor based on Russian Matryoshka structured molecules for enhanced specific identification and double amplification in ultra-trace Tb determination.

The selective and sensitive detection of rare earth elements is thought to be difficult because the concentration of those elements in the sample is commonly at a low level and they normally have severe mutual interference which is caused by homologous chemical properties. In this study, a novel molecularly imprinted polymer (MIP) sensor was fabricated for highly sensitive and selective determination of ultra-trace Tb. The Tb-ethylenediaminetetraacetic acid complex (Tb-EDTA) as the template molecule was incorporated into mono-6-mercapto-β-cyclodextrin (mono-6-SH-β-CD) to form a Russian Matryoshka (RM)-structured molecule (CD/Tb-EDTA). Titanium isopropoxide was utilized in vapor sol-gel polymerization to construct MIP membrane. Moreover, the selectivity of the RM MIP sensor was remarkably enhanced by the "triple-selectivity" recognition of EDTA-to-Tb, β-CD-to-(Tb-EDTA), and 3D cavity-to-(CD/Tb-EDTA), while the sensitivity of the MIP sensor was significantly improved by ECL signal enhancement based on double amplification, in other words, the electrochemiluminescence resonance energy transfer (ECL-RET) between the ECL donor of CD/Tb-EDTA and the ECL acceptor of Ru(bpy), and the ECL enhancement by the co-reactant of CD/Tb-EDTA on Ru(bpy)Cl. When the imprinted cavities were occupied by Tb-EDTA during rebinding, the host-guest inclusion structured complex was formed and the ECL intensities produced by the Ru(bpy)Cl ECL system increased with increasing concentration of Tb-EDTA. The proposed sensor was used for quantitative analysis of Tb with concentrations ranging from 8.00 × 10 mol/L to 4.00 × 10 mol/L and successfully applied to detect Tb in seawater samples. The detection limit of the sensor was found to be 3.90 × 10 mol/L (DL = 3δ/K), which is lower than previously reported values. Thus, the fabricated sensor is feasible for practical applications.