DNAzyme-Based Plasmonic
Nanomachine for Ultrasensitive
Selective Surface-Enhanced Raman Scattering Detection of Lead Ions
via a Particle-on-a-Film Hot Spot Construction
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Abstract
We
propose a highly sensitive and selective surface-enhanced Raman
scattering (SERS) method for determining lead ions based on a DNAzyme-linked
plasmonic nanomachine. A metallic nanoparticle-on-a-film structure
was built through a rigid double-stranded bridge linker composed of
a DNAzyme and its substrate. This DNAzyme could be activated by lead
ions and catalyze a fracture action of the substrate. Thus, the double
chain structure of DNA would turn into a flexible single strand, making
the metal nanoparticles that connected to the terminal of DNAzyme
fall to the surface of the metal film. Hereby, a narrow gap close
to 2 nm generated between metal nanoparticles and the metal film,
exhibiting a similar effect of a “hot spot” and remarkably
enhancing the signal of randomly dispersed Raman-active molecules
on the surface of metal film. By measuring the improvement of SERS
intensity of the Raman-active molecules, we realized the lowest detection
concentration of Pb<sup>2+</sup> ions to 1.0 nM. This SERS analytical
method is highly selective and can be extended universally to other
targets via the accurate programming of corresponding DNA sequences