@article{OertelKellerPrinzetal.2016,
  author    = {Oertel, Jana and Keller, Adrian and Prinz, Julia and Schreiber, Benjamin and Huebner, Rene and Kerbusch, Jochen and Bald, Ilko and Fahmy, Karim},
  title     = {Anisotropic metal growth on phospholipid nanodiscs via lipid bilayer expansion},
  series = {Scientific reports},
  volume    = {6},
  journal   = {Scientific reports},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2045-2322},
  doi       = {10.1038/srep26718},
  pages     = {9},
  year      = {2016},
  abstract  = {Self-assembling biomolecules provide attractive templates for the preparation of metallic nanostructures. However, the intuitive transfer of the "outer shape" of the assembled macromolecules to the final metallic particle depends on the intermolecular forces among the biomolecules which compete with interactions between template molecules and the metal during metallization. The shape of the bio-template may thus be more dynamic than generally assumed. Here, we have studied the metallization of phospholipid nanodiscs which are discoidal particles of similar to 10 nm diameter containing a lipid bilayer similar to 5 nm thick. Using negatively charged lipids, electrostatic adsorption of amine-coated Au nanoparticles was achieved and followed by electroless gold deposition. Whereas Au nanoparticle adsorption preserves the shape of the bio-template, metallization proceeds via invasion of Au into the hydrophobic core of the nanodisc. Thereby, the lipidic phase induces a lateral growth that increases the diameter but not the original thickness of the template. Infrared spectroscopy reveals lipid expansion and suggests the existence of internal gaps in the metallized nanodiscs, which is confirmed by surface-enhanced Raman scattering from the encapsulated lipids. Interference of metallic growth with non-covalent interactions can thus become itself a shape-determining factor in the metallization of particularly soft and structurally anisotropic biomaterials.},
  language  = {en}
}
@article{PrinzHeckElleriketal.2016,
  author    = {Prinz, Julia and Heck, Christian and Ellerik, Lisa and Merk, Virginia and Bald, Ilko},
  title     = {DNA origami based Au-Ag-core-shell nanoparticle dimers with single-molecule SERS sensitivity},
  series = {Nanoscale},
  volume    = {8},
  journal   = {Nanoscale},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2040-3364},
  doi       = {10.1039/c5nr08674d},
  pages     = {5612 -- 5620},
  year      = {2016},
  abstract  = {DNA origami nanostructures are a versatile tool to arrange metal nanostructures and other chemical entities with nanometer precision. In this way gold nanoparticle dimers with defined distance can be constructed, which can be exploited as novel substrates for surface enhanced Raman scattering (SERS). We have optimized the size, composition and arrangement of Au/Ag nanoparticles to create intense SERS hot spots, with Raman enhancement up to 10(10), which is sufficient to detect single molecules by Raman scattering. This is demonstrated using single dye molecules (TAMRA and Cy3) placed into the center of the nanoparticle dimers. In conjunction with the DNA origami nanostructures novel SERS substrates are created, which can in the future be applied to the SERS analysis of more complex biomolecular targets, whose position and conformation within the SERS hot spot can be precisely controlled.},
  language  = {en}
}
@misc{PrinzHeckElleriketal.2016,
  author    = {Prinz, Julia and Heck, Christian and Ellerik, Lisa and Merk, Virginia and Bald, Ilko},
  title     = {DNA origami based Au-Ag-core-shell nanoparticle dimers with single-molecule SERS sensitivity},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-89714},
  pages     = {5612 -- 5620},
  year      = {2016},
  abstract  = {DNA origami nanostructures are a versatile tool to arrange metal nanostructures and other chemical entities with nanometer precision. In this way gold nanoparticle dimers with defined distance can be constructed, which can be exploited as novel substrates for surface enhanced Raman scattering (SERS). We have optimized the size, composition and arrangement of Au/Ag nanoparticles to create intense SERS hot spots, with Raman enhancement up to 1010, which is sufficient to detect single molecules by Raman scattering. This is demonstrated using single dye molecules (TAMRA and Cy3) placed into the center of the nanoparticle dimers. In conjunction with the DNA origami nanostructures novel SERS substrates are created, which can in the future be applied to the SERS analysis of more complex biomolecular targets, whose position and conformation within the SERS hot spot can be precisely controlled.},
  language  = {en}
}
@article{PrinzHeckElleriketal.2016,
  author    = {Prinz, Julia and Heck, Christian and Ellerik, Lisa and Merk, Virginia and Bald, Ilko},
  title     = {DNA origami based Au-Ag-core-shell nanoparticle dimers with single-molecule SERS sensitivity},
  series = {Nanoscale},
  journal   = {Nanoscale},
  number    = {8},
  publisher = {RSC Publishing},
  address   = {Cambridge},
  doi       = {10.1039/C5NR08674D},
  pages     = {5612 -- 5620},
  year      = {2016},
  abstract  = {DNA origami nanostructures are a versatile tool to arrange metal nanostructures and other chemical entities with nanometer precision. In this way gold nanoparticle dimers with defined distance can be constructed, which can be exploited as novel substrates for surface enhanced Raman scattering (SERS). We have optimized the size, composition and arrangement of Au/Ag nanoparticles to create intense SERS hot spots, with Raman enhancement up to 1010, which is sufficient to detect single molecules by Raman scattering. This is demonstrated using single dye molecules (TAMRA and Cy3) placed into the center of the nanoparticle dimers. In conjunction with the DNA origami nanostructures novel SERS substrates are created, which can in the future be applied to the SERS analysis of more complex biomolecular targets, whose position and conformation within the SERS hot spot can be precisely controlled.},
  language  = {en}
}
@phdthesis{Prinz2016,
  author    = {Prinz, Julia},
  title     = {DNA origami substrates as a versatile tool for surface-enhanced Raman scattering (SERS)},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-104089},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xviii, 184 Seiten},
  year      = {2016},
  abstract  = {Surface-enhanced Raman scattering (SERS) is a promising tool to obtain rich chemical information about analytes at trace levels. However, in order to perform selective experiments on individual molecules, two fundamental requirements have to be fulfilled. On the one hand, areas with high local field enhancement, so-called "hot spots", have to be created by positioning the supporting metal surfaces in close proximity to each other. In most cases hot spots are formed in the gap between adjacent metal nanoparticles (NPs). On the other hand, the analyte has to be positioned directly in the hot spot in order to profit from the highest signal amplification. The use of DNA origami substrates provides both, the arrangement of AuNPs with nm precision as well as the ability to bind analyte molecules at predefined positions. Consequently, the present cumulative doctoral thesis aims at the development of a novel SERS substrate based on a DNA origami template. To this end, two DNA-functionalized gold nanoparticles (AuNPs) are attached to one DNA origami substrate resulting in the formation of a AuNP dimer and thus in a hot spot within the corresponding gap. The obtained structures are characterized by correlated atomic force microscopy (AFM) and SERS imaging which allows for the combination of structural and chemical information. Initially, the proof-of principle is presented which demonstrates the potential of the novel approach. It is shown that the Raman signal of 15 nm AuNPs coated with dye-modified DNA (dye: carboxytetramethylrhodamine (TAMRA)) is significantly higher for AuNP dimers arranged on a DNA origami platform in comparison to single AuNPs. Furthermore, by attaching single TAMRA molecules in the hot spot between two 5 nm AuNPs and optimizing the size of the AuNPs by electroless gold deposition, SERS experiments at the few-molecule level are presented. The initially used DNA origami-AuNPs design is further optimized in many respects. On the one hand, larger AuNPs up to a diameter of 60 nm are used which are additionally treated with a silver enhancement solution to obtain Au-Ag-core-shell NPs. On the other hand, the arrangement of both AuNPs is altered to improve the position of the dye molecule within the hot spot as well as to decrease the gap size between the two particles. With the optimized design the detection of single dye molecules (TAMRA and cyanine 3 (Cy3)) by means of SERS is demonstrated. Quantitatively, enhancement factors up to 10^10 are estimated which is sufficiently high to detect single dye molecules. In the second part, the influence of graphene as an additional component of the SERS substrate is investigated. Graphene is a two-dimensional material with an outstanding combination of electronical, mechanical and optical properties. Here, it is demonstrated that single layer graphene (SLG) replicates the shape of underlying non-modified DNA origami substrates very well, which enables the monitoring of structural alterations by AFM imaging. In this way, it is shown that graphene encapsulation significantly increases the structural stability of bare DNA origami substrates towards mechanical force and prolonged exposure to deionized water. Furthermore, SLG is used to cover DNA origami substrates which are functionalized with a 40 nm AuNP dimer. In this way, a novel kind of hybrid material is created which exhibits several advantages compared to the analogue non-covered SERS substrates. First, the fluorescence background of dye molecules that are located in between the AuNP surface and SLG is efficiently reduced. Second, the photobleaching rate of the incorporated dye molecules is decreased up to one order of magnitude. Third, due to the increased photostability of the investigated dye molecules, the performance of polarization-dependent series measurements on individual structures is enabled. This in turn reveals extensive information about the dye molecules in the hot spot as well as about the strain induced within the graphene lattice. Although SLG can significantly influence the SERS substrate in the aforementioned ways, all those effects are strongly related to the extent of contact with the underlying AuNP dimer.},
  language  = {en}
}
@article{MatkovicVasicPesicetal.2016,
  author    = {Matkovic, Aleksandar and Vasic, Borislav and Pesic, Jelena and Prinz, Julia and Bald, Ilko and Milosavljevic, Aleksandar R. and Gajic, Rados},
  title     = {Enhanced structural stability of DNA origami nanostructures by graphene encapsulation},
  series = {NEW JOURNAL OF PHYSICS},
  volume    = {18},
  journal   = {NEW JOURNAL OF PHYSICS},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/18/2/025016},
  pages     = {9},
  year      = {2016},
  abstract  = {We demonstrate that a single-layer graphene replicates the shape of DNA origami nanostructures very well. It can be employed as a protective layer for the enhancement of structural stability of DNA origami nanostructures. Using the AFM based manipulation, we show that the normal force required to damage graphene encapsulated DNA origami nanostructures is over an order of magnitude greater than for the unprotected ones. In addition, we show that graphene encapsulation offers protection to the DNA origami nanostructures against prolonged exposure to deionized water, and multiple immersions. Through these results we demonstrate that graphene encapsulated DNA origami nanostructures are strong enough to sustain various solution phase processing, lithography and transfer steps, thus extending the limits of DNA-mediated bottom-up fabrication.},
  language  = {en}
}
@article{PrinzMatkovicPesicetal.2016,
  author    = {Prinz, Julia and Matkovic, Aleksandar and Pesic, Jelena and Gajic, Rados and Bald, Ilko},
  title     = {Hybrid Structures for Surface-Enhanced Raman Scattering: DNA Origami/Gold Nanoparticle Dimer/Graphene},
  series = {Small},
  volume    = {12},
  journal   = {Small},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1613-6810},
  doi       = {10.1002/smll.201601908},
  pages     = {5458 -- 5467},
  year      = {2016},
  abstract  = {A combination of three innovative materials within one hybrid structure to explore the synergistic interaction of their individual properties is presented. 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 efficient fluorescence 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.},
  language  = {en}
}