In situ fabrication of urchin-like Cu@carbon nanoneedles based aptasensor for ultrasensitive recognition of trace mercury ion

Mercury ion (Hg²⁺) is a strong toxic heavy ion that causes severe damages to the environment and readily accumulates in the food chain. However, it remains a major challenge to realize a sensitive and precise recognition of Hg²⁺ with a trace concentration for early identifying the pollution source. In this work, a novel electrochemical aptasensor was designed to achieve an ultrasensitive and quantitative detection of trace Hg²⁺, relying on an urchin-like architecture of Cu@carbon nanoneedles (Cu@CNNs) as the electroactive probe. This specific nanostructure was in-situ constructed through a controllable pyrolysis process, serving as a signal magnifier and DNA loading platform owing to its outstanding electrocatalysis and large specific surface areas. Meanwhile, an exonuclease III-assisted cycling amplification strategy was designed to efficiently amplify the signal strength of trace Hg²⁺ via the consecutive release of report probes in nicking reaction. This as-prepared Hg²⁺ aptasensor exhibited an ultralow detection limit of 3.7 fM (7 × 10⁻⁶ ppm) and a wide linear range from 10 fM to 10 μM, together with the satisfactory stability and reusability for assay in real water samples. It is highly expected that this Cu@CNNs based aptasensor will have tremendous potentials in the early warning and efficient pollution monitoring of heavy metal ions.