CuCo alloy-embedded carbon nanocages for simultaneous biosensing of Hg2+ and Cd2+ in environmental water.

Mercury ions (Hg2+) and cadmium ions (Cd2+) are highly toxic heavy metals that can easily accumulate in the food chain and pose serious threats to the environment. However, achieving sensitive and efficient identification and determination of trace Hg2+ and Cd2+ remain a major challenge in real water environment. In this work, we developed an ultrasensitive electrochemical aptasensor for simultaneous recognition and determination of Hg2+ and Cd2+ within 25 min, using a CuCo@C nanocage as a nano-signal amplifier. The well-defined cubic nanocage structure was regulated through precise pyrolysis of PVP-shell-protected CuCo Prussian blue analogues in situ. The resulting architecture features highly dispersed, small-sized CuCo alloys embedded in a carbon framework, which exhibits excellent electrocatalytic activity, high electrical conductivity, and abundant active sites for immobilizing capture DNA. Coupled with a dual-target-induced chain release strategy, the aptasensor achieved simultaneous detection of Hg2+ and Cd2+ with ultralow detection limits (0.033 fM and 0.036 fM, respectively) and wide linear ranges (0.1 fM-0.1 nM for Hg2+ and 0.1 fM-0.01 nM for Cd2+). Moreover, the CuCo@C nanocages-based aptasensor demonstrated good reproducibility, reusability, and was successfully applied to the detection of both heavy metal ions in lake water samples. This work paves the way for rapid and ultrasensitive multiplex detection of pollutants for assessing heavy metal pollution levels, offering a powerful technique for early warning and source tracing of pollutant leakage.