DNA-guided assembly of three-dimensional nanostructures for surface-enhanced Raman spectroscopy

Surface enhancement Raman spectroscopy (SERS) has drawn much attention in recent years because its ability to greatly enhance Raman signals to allow for the detection of molecules at low concentration. When using metallic nanoparticles as SERS substrates, many studies have shown that the size of the interparticle gap significantly affects the enhancement of the Raman signals. Given that the optimal interparticle gap is as small as a few nanometers, fabricating sensitive, uniform, and reproducible SERS substrates remains challenging. Here we report a three-dimensional SERS substrate created through the assembly of core-shell nanoparticles using DNA. By using DNA of appropriate sequence and length, DNA-functionalized nanoparticles were assembled into ordered and highly packed nanostructures. The interparticle distance was precisely controlled by adjusting the design of the DNA and the thickness of the silver shell coated on the gold nanoparticles. Compared with randomly aggregated nanoparticles, the interparticle distance in the synthesized nanostructures can be more uniform and better controlled. In addition, the DNA-guided assembly process allows us to create precise nanostructures without using complex and expensive fabrication methods. The study demonstrates that the synthesized nanostructures can be used as effective SERS substrates to successfully measure the Raman signals of malachite green, a toxic compound that is sometimes illegally used on fish, as well as Fluorescein isothiocyanate (FITC) at low concentrations.