High-performance electrochemical mercury aptasensor based on synergistic amplification of Pt nanotube arrays and Fe₃O₄/rGO nanoprobes

In this work, a novel sandwich-type aptasensor was designed for the ultrasensitive recognition of trace mercury ions in water. Numerous oriented platinum nanotube arrays (PtNAs) were in-situ crystallized on a flexible electrode as a sensing interface, while thionine labelled Fe₃O₄/rGO nanocomposites as signal amplifiers. Both PtNAs/CF and nanocomposites were synthesized by easy hydrothermal processes. With their large surface area, it was favorable for electrochemical performance and immobilization of capture DNAs (cDNA) and report DNAs (rDNA). Upon the existence of Hg²⁺, partial linker DNAs were tightly bound with cDNAs through thymine-Hg²⁺-thymine pairing (T-Hg²⁺-T). Then rDNAs attached Fe₃O₄/rGO nanoprobes were fixed on the electrode through the match of remaining linker DNAs and rDNAs. Under the optimal conditions, the Hg²⁺ aptasensor showed a synergistic amplification performance with a wide linear range from 0.1nM to 100 nM, as well as a low detection limit of 30 pM. Moreover, the as-prepared aptasensor also exhibited reliable performance for assay in real lake water samples.