Au–Ag core–shell nanoparticles with controllable shell thicknesses for the detection of adenosine by surface enhanced Raman scattering

• The different shell thicknesses of Au@Ag NPs are grown by seeding-mediated method.
• The concentrations of Au NPs are used to control shell thicknesses of Au@Ag NPs.
• The Au@Ag NPs can be used to detect adenosine by a structures-switch aptamer.
• The fabrication of DNA-based adenosine sensor is facile with high reproducibility.
• The DNA-based adenosine sensor exhibit very low detection limit (1 nM).

In this study, we report a feasible aqueous chemical method to synthesize Au core–Ag shell nanoparticles (NPs) by seeding growth approach. The concentration of Au NPs plays an important role in growing the different thicknesses of Ag shells. The design of signaling aptamer utilizes the target-induced switching between an aptamer/DNA duplex and an aptamer/target complex. The surface enhanced Raman scattering (SERS) signal was enhanced upon the hybridization of the Raman reporter-labeled DNA released from the target-induced displacement with the captured DNA immobilized on the silicon substrate with Au–Ag core–shell NPs. This substrate with 12.4 nm Ag shell shows high reproducibility, strong enhancement, and a low detection limit (1 nM). The enhancement in DNA-based adenosine detection properties shall be advantageous in applications for other aptamer sensing systems.

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