‘On-off-on’ electrochemiluminescent aptasensor for Hg2+ based on dual signal amplification enabled by a self-enhanced luminophore and resonance energy transfer

• A dual signal amplification strategy was developed for ‘on–off-on’ ECL system. • Self-enhaced luminophore of Ru@SiO 2 -NGQDs provided the first ‘switch on’ signal. • The ‘switch off’ signal was obtained by the ERET between Ru@SiO 2 -NGQDs and AuNPs. • Hg 2+ induced the second ‘switch on’ signal with amplified ECL recovery efficiency. • The method exhibited wide linear range, low LOD and good selectivity for Hg 2+ assay. Divalent mercury ion (Hg 2+ ) is widely distributed in the ecological environment and harmful to the human body and the environment. Herein, a highly sensitive and selective ‘on–off-on’ electrochemiluminescence (ECL) aptamer sensing method based on the dual signal amplification strategy of a self-enhanced luminophore and ECL resonance energy transfer (ECL-RET) was developed to detect Hg 2+ . In detail, the first ‘switch-on’ state was obtained by the self-enhanced luminophore of Ru(bpy) 3 2+ -doped silica nanoparticle-nitrogen-doped graphene quantum dots (Ru@SiO 2 -NGQDs) modified glassy carbon electrode, which significantly amplified the ECL intensity compared with the mixture of Ru@SiO 2 and NGQDs. Later, the ‘switch-off’ state was induced by gold nanoparticles (AuNPs), which acted the acceptor in the ECL-RET system between AuNPs and Ru@SiO 2 -NGQDs due to their good spectral overlap. This combination of the self-enhanced luminophore and ECL-RET provided a novel dual signal amplification strategy, which led to a high signal-to-noise ratio and high analysis sensitivity. Finally, upon the addition of Hg 2+ , the formation of a stable T-Hg 2+ -T structure induced the release of AuNPs from the sensing interface and halted the ECL-RET process, resulting in ECL signal recovery (the second ‘switch-on’ state). For the detection of Hg 2+ , the proposed ECL sensor exhibited a wide linear range from 1 × 10 −14 to 1 × 10 −6 M and a highly sensitive detection limit of 3.0 fM. Finally, the feasibility of the developed method in water sample analysis was investigated.