An ionic liquid supported CeO₂ nanoparticles-carbon nanotubes composite-enhanced electrochemical DNA-based sensor for...

An electrochemical sensor incorporating a signal enhancement for the determination of lead (II) ions (Pb²⁺) was designed on the basis of the thrombin-binding aptamer (TBA) as a molecular recognition element and ionic liquid supported cerium oxide (CeO₂) nanoparticles-carbon nanotubes composite modification. The composite comprises nanoparticles CeO₂, multi-wall carbon nanotubes (MWNTs) and hydrophobic room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄). The electrochemical sensors were fabricated by immersing the CeO₂-MWNTs-EMIMBF₄ modified glassy carbon electrode (GCE) into the solution of TBA probe. In the presence of Pb²⁺, the TBA probe could form stable G-quartet structure by the specific binding interactions between Pb²⁺ and TBA. The TBA-bound Pb²⁺ can be electrochemically reduced, which provides a readout signal for quantitative detection of Pb²⁺. The reduction peak current is linearly related to the concentration of Pb²⁺ from 1.0×10^-8 M to 1.0×10^-5 M with a detection limit of 5×10^-9 M. This work demonstrates that the CeO₂-MWNTs-EMIMBF₄ nanocomposite modified GCE provides a promising platform for immobilizing the TBA probe and enhancing the sensitivity of the DNA-based sensors.