DNA origami-templated assembly of plasmonic nanostructures with enhanced Raman scattering

DNA origami have been established as versatile templates to fabricate plasmonic nanostructures in predefined shapes and multiple dimensions. Limited to the size of DNA origami, which are approximate to 100 nm, it is hard to assemble more intricate plasmonic nanostructures in large scale. Herein, we used rectangular DNA origami as the template to anchor two 30-nm gold nanoparticles(Au NPs) which induced dimers nanostructures. Transmission electron microscopy(TEM) images showed the assembly of Au NPs with high yields. Using the linkers to organize the DNA origami templates into nanoribbons,chains of Au NPs were obtained, which was validated bythe TEM images. Furthermore, we observed a significant Raman signal enhancement from molecules covalently attached to the Au NP-dimers and Au NP-chains. Our method opens up the prospects of high-ordered plasmonic nanostructures with tailored optical properties.

Fano resonance boosted cascaded optical field enhancement in a plasmonic nanoparticle-in-cavity nanoantenna array and its SERS application

Cascaded optical field enhancement(CFE)can be realized in some specially designed multiscale plasmonic nanostructures,in which the generation of extremely strong fields at nanoscale volume is crucial for many applications,for example,surface-enhanced Raman spectroscopy(SERS).In this paper,we propose a strategy for realizing a high-quality plasmonic nanoparticle-in-cavity(PIC)nanoantenna array,in which strong coupling between a nanoparticle(NP)dark mode with a high-order nanocavity bright mode can produce strong Fano resonance at the target wavelength.The Fano resonance can effectively boost the CFE in a PIC.A cost-effective and reliable nanofabrication method is developed using room temperature nanoimprinting lithography to manufacture high-quality PIC arrays.This technique guarantees the generation of only one gold NP at the bottom of each nanocavity,which is crucial for the generation of the expected CFE.To demonstrate the performance and application of the PIC array,the PIC array is employed as an active SERS substrate for detecting 4-aminothiophenol molecules.An experimental SERS enhancement factor of 2×10^(7) is obtained,which verifies the field enhancement and the potential of this device.

Selective deposition of a MOF at the spikes of Au nanostars for SERS detection

In the pursuit of advancing molecular sensing through surface-enhanced Raman spectroscopy(SERS),the combination of plasmonic nanoparticles and metal-organic frameworks(MOFs)has emerged as a highly effective approach to enhance the sensitivity and selectivity of SERS substrates.However,most prior investigations have predominantly focused on MOF-coated plasmonic nanoparticles in core@shell or layer-by-layer configurations,leaving a notable knowledge gap in exploring alternative configurations.Herein we present a facile method to construct a particle-on-mirror architecture by selectively coating a MOF,zeolitic imidazolate framework-8(ZIF-8),onto the tips of Au nanostars and subsequently depositing the resultant nanoparticles onto a Au film.This design integrates the electric field enhancement at the sharp tips and nanogaps,along with the molecular enrichment function within the porous MOF immobilized at the tips and nanogaps,leading to a substantial boost in the SERS signal intensity.Such a unique SERS platform enables consistent and outstanding SERS performance for analytes of different sizes.This work opens up a promising strategy for constructing multifunctional nanostructures for sensitive SERS detection in real-life scenarios.