Plasmonic detection of label free DNA immobilized on Surface Enhanced Raman Spectroscopy (SERS) substrate is a challenge in terms of reproducibility and reliability of spectra. Among several important experimental parameters, the morphology of the metal nanoparticles is crucial.
A new concept of low cost SERS substrate constituted of Ag NPs spread on TiO2 film has been developed and optimized (M. Langlet, LMGP). Thanks to its controlled fabrication, we are able to obtain very well resolved spectra with an excellent reproducibility over mm2 area of single stranded monobase and multibase oligonucleotides sequences as well as double stranded oligonucleotides. The oligonucleotides are lying flat on the Ag NPs with the nucleobase being perpendicular. This is due to the intern nitrogen atoms of the nucleobase which bind to Ag. However some re-orientations of DNA molecules with respect to the Ag NP surface can occur, depending on the DNA concentration.
Elaboration of an Ag°/TiO2 platform for DNA detection by surface enhanced Raman spectroscopy. Langlet M, Sow I, Briche S, Messaoud M, Chaix-Pluchery O, Dherbey-Roussel F, Chaudouët P, Stambouli V. Surface Science. 2011.
Controlled growth of silver nanoparticles through a chemically assisted photocatalytic reduction process for SERS substrate applications. He L, Riassetto D, Bouvier P, Chaix-Pluchery O, Stambouli V, Langlet M. Journal of Photochemistry and Photobiology A: Chemistry. 2014.