2 research outputs found
DNA Origami Substrates for Highly Sensitive Surface-Enhanced Raman Scattering
DNA nanotechnology holds great promise
for the fabrication of novel
plasmonic nanostructures and the potential to carry out single-molecule
measurements using optical spectroscopy. Here, we demonstrate for
the first time that DNA origami nanostructures can be exploited as
substrates for surface-enhanced Raman scattering (SERS). Gold nanoparticles
(AuNPs) have been arranged into dimers to create intense Raman scattering
hot spots in the interparticle gaps. AuNPs (15 nm) covered with TAMRA-modified
DNA have been placed at a nominal distance of 25 nm to demonstrate
the formation of Raman hot spots. To control the plasmonic coupling
between the nanoparticles and thus the field enhancement in the hot
spot, the size of AuNPs has been varied from 5 to 28 nm by electroless
Au deposition. By the precise positioning of a specific number of
TAMRA molecules in these hot spots, SERS with the highest sensitivity
down to the few-molecule level is obtained
Polarization- and Wavelength-Dependent Surface-Enhanced Raman Spectroscopy Using Optically Anisotropic Rippled Substrates for Sensing
Anisotropic Ag nanoparticle arrays
were created by metal evaporation
on rippled silicon templates for sensing of molecules with surface-enhanced
Raman spectroscopy. Our results show that these substrates can be
used for analysis of complex molecular mixtures and discrimination
of solvent molecules. These properties are due to their polarization
and wavelength dependency that provide enhancement in a wide spectral
range. The dielectric function parallel and perpendicular to the long
axis of the nanostructures was determined via ellipsometry yielding
two different plasmonic resonances. Polarized surface-enhanced raman
scattering (SERS) was subsequently measured as a function of the polarization
angle θ for a 4-mercaptobenzonitrile self-assembled monolayer
covalently attached to the Ag surface. For 514 nm excitation a cos<sup>2</sup> θ-dependence and for 647 nm excitation a sin<sup>2</sup> θ-dependency were found, with the maxima expressing
the resonances perpendicular and parallel to the ripples, respectively.
Those results open the path for using such a substrate as a chemical
sensor providing strong enhancement in a broad range of laser wavelengths
on only one sensing surface and increasing the specificity by matching
resonant Raman conditions