# 3D DNA Nanostructures: The Nanoscale Architect
## 5 Applications
### Surface Templating
#### 5.2.3 Nanofabrication of Plasmonic and Nanoelectric Devices  
There are numerous strategies for DNA nanostructure templates to bind or interact with inorganic nanomaterials such as gold or carbon nanotubes. Thiol-modified DNA strands are a well-known method for conjugating gold nanoparticles to DNA nanostructures, but so can various peptides and proteins [141]. The geometry of a DNA nanostructure template can provide an unparalleled substrate to pursue the bottom-up assembly of electric and plasmonic nanodevices. Studies involving DNA-templated gold clusters have been numerous in the last decade, but recent work has also drawn attention to a wider variety of inorganic materials such as silica and carbon nanotubes. Considering the breadth of proteins and peptides with specific material affinities that have yet to be used in conjunction with DNA nanostructures, a major paradigm shift in the possible applications of DNA nanostructure templates for nanofabrication could linger in the near future. DNA-templated arrangements of metallic nanoparticles have been a major research focus for realizing a bevy of novel plasmonic nanodevices and phenomena in the last two decades. Some of the earliest demonstrations were with single DNA duplexes acting as tethers to assist the ordered aggregation of gold nanoparticles [142; 143]. Since then, many new techniques have been developed implementing complex geometric arrangements. The intensity and wavelength of plasmonic phenomena is heavily dependent on the geometric arrangement and composition of its metallic components, such as gold, silver, and platinum. In single particles, the geometry is typically constrained by the extent to which crystallographic facets of the material can be chemically restricted for growth beginning from a seed. While this has generated an incredible variety of particles, including spheres, rods, triangles, and stars, arranging them for reproducible cluster or colloidal effects has been much more challenging. Many applications have since demonstrated the advantages of tailored shape design using DNA nanostructures in comparison to existing biological templates such as viral capsids or bacterial scaffolds [144; 145; 141]. Chiral assemblies of gold nanospheres spaced helically along a straight DNA origami bundle emit a distinct circular dichroism signal [146]. Similar effects are also generated by gold nanorods oriented along the edges of an adjoining pair of DNA origami triangles [147], and in general, there have been numerous methods to produce chiral orientations using a DNA nanostructure support [148; 149; 150; 151; 152; 153; 154]. Nanoparticlegeometry can also determine field enhancement effects. For example, gold nanospheres arranged into a square on a flat DNA origami template form a SERS hotspot in the negative space in their middle [155]. The [PERSON] group and collaborators used a DNA origami template to position two gold triangles with nanometer precision in a bowtie shape to generate a high local field enhancement between their tips [156]. The [PERSON] group and collaborators created DNA nanotubes from a honeycomb lattice similar to how carbon nanotubes appear as rolled sheets of graphene, then set gold nanoparticles into specific lattice holes as a strategy for producing plasmonic metamaterials [157]. Recent work by [PERSON] and collaborators demonstrated a construction of a DNA nanoantenna to facilitate detection for bioassays, especially when expensive, highly sensitive detectors are unavailable. Two silver nanoparticles were set across from each other around a DNA bundle. This placement created a plasmonic hotspot within the small gap between the nanoparticles, and the DNA nanoantenna was designed with a small reservoir for capturing analytes that was positioned within this gap such that the fluorescence-labelled signal from detection events would be amplified [158].