Tip-Enhanced Raman Spectroscopy of Combed Double-Stranded DNA Bundles

Abstract

Double-stranded (ds) DNA of a λ-phage virus are combed on octadecyltrichlorosilane (OTS)-modified borosilicate glass substrates and investigated by means of tip-enhanced Raman spectroscopy (TERS) using tips coated with an Ag/Au bilayer. Owing to an enhancement factor higher than 6 × 10 2 and a lateral spatial resolution better than 9 nm (which is below the size of the tip apex radius), cross-sections of nanowire-shaped thin DNA bundles can be spatially resolved. TER spectra reveal vibrational modes typical of DNA nucleobases and backbone, as confirmed by confocal Raman measurements carried out on dense stacks of DNA strands. While the TER signature of nucleobases is congruent with observations in single-stranded (ss) DNA, additional modes tied to the DNA backbone can be discerned in ds DNA. TERS enables ss and ds DNA samples to be distinguished from each other and hence can be exploited for the detection of DNA hybridization. Moreover, no TER contribution of the OTS layer appears, suggesting that functionalized DNA strands could be studied without spectral perturbation from the substrate. This work paves the way toward the nanoscale spectral study of organized DNA-based nanostructures.

Bare and protected sputtered-noble-metal films for surface-enhanced Raman spectroscopy

“…Therefore, the calculated EFs are average values over the probed region, which present a practical interest in the perspective of using these sputtered Ag and Au films like SERS platforms for sensing. In a previous study [23], we evidenced that Au could serve as protective cover to hinder Ag oxidation and sulfuration occurring within hours in ambient conditions [7]. However, such thin Au layer is not expected to be homogeneous at the rough Ag surface.…”

Tip-enhanced Raman spectroscopy: principles and applications

“…Combed double-stranded (DS) DNA immobilised on a glass surface were investigated using TERS by Najjar et al with a resolution ≈ 9 nm [8] (Fig. 6).…”

“…Since then TERS has rapidly progressed to become a non-destructive scanning probe microscopy tool for surface chemical characterisation [6], and opened up the opportunities to study single macro-molecules with sub-nm spatial resolution [7]. Over the last 15 years, the technique has been used to study scientific problems in biology [8], photovoltaics [9], catalysis [10], semiconductors [11], carbon nanotubes [12], graphene [13] and single molecule detection [7].…”

Tip-enhanced Raman scattering—Targeting structure-specific surface characterization for biomedical samples

“…In another experiment, combed double-stranded DNA bundles were investigated by TERS to differentiate DNA constituents form functionalizing agent and from single-strand DNA molecules [99]. A lateral resolution of 9 nm ensured that the thin nanowire bundle was spatially resolved.…”