Raman Enhancement of Nanoparticle Dimers Self-Assembled Using DNA Origami Nanotriangles

Abstract

Surface-enhanced Raman scattering is a powerful approach to detect molecules at very low concentrations, even up to the single-molecule level. One important aspect of the materials used in such a technique is how much the signal is intensified, quantified by the enhancement factor (EF). Herein we obtained the EFs for gold nanoparticle dimers of 60 and 80 nm diameter, respectively, self-assembled using DNA origami nanotriangles. Cy5 and TAMRA were used as surface-enhanced Raman scattering (SERS) probes, which enable the observation of individual nanoparticles and dimers. EF distributions are determined at four distinct wavelengths based on the measurements of around 1000 individual dimer structures. The obtained results show that the EFs for the dimeric assemblies follow a log-normal distribution and are in the range of 106 at 633 nm and that the contribution of the molecular resonance effect to the EF is around 2, also showing that the plasmonic resonance is the main source of the observed signal. To support our studies, FDTD simulations of the nanoparticle’s electromagnetic field enhancement has been carried out, as well as calculations of the resonance Raman spectra of the dyes using DFT. We observe a very close agreement between the experimental EF distribution and the simulated values.

Lab-on-a-DNA origami: nanoengineered single-molecule platforms

“…Also, we observed that 633 nm is the optimal laser wavelength for Raman excitation of Au dimers. 59 We also showed graphene as a protection layer covering the AuNP dimers assembled over nanotriangles. The SERS signals of the TAMRA dyes were still observed after 800 s of continuous irradiation, showing that graphene reduced the photobleaching effect, possibly due to protection from the atmospheric oxygen and by enabling efficient heat dissipation.…”

“…Using fully dye-covered nanoparticles arranged on DNA origami nanotriangles, we studied how the enhancement factor is distributed depending on the size of AuNPs, the chosen dye, and the excitation wavelength. 59 The results showed that AuNPs with a diameter of 60 nm is optimal for obtaining SERS spectra of single dimers. Increasing the diameter to 80 nm only increased the signal slightly, but at the same time, 80 nm AuNPs are significantly more challenging to modify and stabilize.…”

The Effect of Nanoparticle Composition on the Surface-Enhanced Raman Scattering Performance of Plasmonic DNA Origami Nanoantennas

“…Roughly 100 DONAs were measured for each nanoparticle dimer design, dye molecule, and excitation wavelength. At the SM level, peak fluctuations have been reported, − and at the same time, spectral variations with excitation wavelengths need to be considered Figure SI4 compares SERS and bulk TAMRA spectra at four different excitation wavelengths.…”

“…EF for DONAs was determined using the following equation E F D O N A = true( I normalS normalE normalR normalS N normalS normalE normalR normalS true) × true( N normalB normalu normall normalk I normalB normalu normall normalk true) where I SERS and I Bulk are the intensities of most pronounced TAMRA bands (at 1651 cm –1 ), and N SERS and N Bulk are the number of molecules that contributed to the signals. N SERS for fully dye-coated DONA was determined by the number of molecules on the surface of NPs in the hot spot, and N SERS for single-molecule DONA was the molecule conjugated to the Nanofork. N Bulk was determined by the number of molecules in the confocal volume of the laser penetration.…”

A switchable DNA origami/plasmonic hybrid device with a precisely tuneable DNA-free interparticle gap

“…18 Remarkably, since the structure of the double helix is known, DNA origami constructs can be addressed with nm-sized accuracy, thus enabling the placement of desired molecules in a predefined spatial arrangement. DNA origami architectures have been combined with plasmonically active nanostructures leading to hybrid nanomaterials for applications in sensing, 19,20,21 spectroscopy, [22][23][24][25] and biomedical detection methods, 26,27 including single-molecule approaches. 13,28,29 In particular, dimerisation of AuNP has been successfully achieved using origami slit 4 or sheet-like designs.…”