Surface-enhanced Raman scattering

DNA origami is a fascinating technique that allows for the precise arrangement of nanoparticles, fluorescent dyes, specific DNA structures (such as aptamers) and proteins into well-defined arrays. Consequently, DNA origami nanostructures have been used to fabricate a variety of plasmonic nanostructures by the controlled arrangement of metallic nanoparticles. Surface-enhanced Raman scattering (SERS) is one of the most promising analytical techniques for bioanalytics, capable of single-molecule detection and true multiplexing. However, the fabrication of efficient SERS substrates remains one of the most difficult challenges in SERS, since SERS relies on the formation of hot spots within Au or Ag nanoparticle aggregates and the placement of analyte molecules specifically into the hot spots.

We use DNA origami nanostructures to fabricate intense Raman scattering hot spots between two Au nanoparticles and to place target molecules precisely into these hot spots to enable highly sensitive detection of analyte molecules down to the single-molecule level.

J. Prinz, B. Schreiber, L. Olejko, J. Oertel, J. Rackwitz, A. Keller, I. Bald, J. Phys. Chem. Lett. 20134, 4140-4145.

J. Prinz, C. Heck, L. Ellerik, V. Merk, I. Bald, Nanoscale 2016, 8, 5612.

Hybrid structures of gold nanoparticles and graphene

The unique electronic, mechanical, and thermal properties of graphene are combined with the plasmonic properties of gold nanoparticle (AuNP) dimers, which are assembled using DNA origami nanostructures. This novel hybrid structure is characterized by means of correlated atomic force microscopy and surface-enhanced Raman scattering (SERS). It is demonstrated that strong interactions between graphene and AuNPs result in superior SERS performance of the hybrid structure compared to their individual components. This is particularly evident in effi cient fl uorescence quenching, reduced background, and a decrease of the photobleaching rate up to one order of magnitude. The versatility of DNA origami structures to serve as interface for complex and precise arrangements of nanoparticles and other functional entities provides the basis to further exploit the potential of the here presented DNA origami–AuNP dimer–graphene hybrid structures.

J. Prinz, A. Matković, J. Pešić, R. Gajić, I. Bald, Small 2016, 12, 5458.

Gold and silver nanolenses

Nanolenses are self-similar chains of metal nanoparticles which theoretically can provide extremely high field enhancements. Yet, the complex structure renders their synthesis challenging and has hampered closer analyses so far.  Here, DNA origami is used to self-assemble 10, 20 and 60 nm gold nanoparticles as plasmonic gold nanolenses (AuNLs) in solution and in billions of copies. Three different geometrical arrangements are assembled and for each of the three designs, surface-enhanced Raman scattering (SERS) capabilities of single AuNLs are assessed. For the design which shows best properties, SERS signals from the two different internal gaps are compared by selectively placing probe dyes. The highest Raman enhancement is found for the gap between the small and medium nanoparticle, which is indicative of a cascaded field enhancement.

C. Heck, J. Prinz, A. Dathe, V. Merk, O. Stranik, W. Fritzsche, J. Kneipp, I. Bald, ACS Photonics 20174, 1123.

PhD theses completed on this topic

Dr. Julia Prinz: DNA origami substrates as a versatile tool for surface-enhanced Raman scattering (SERS)

Dr. Christian Heck