TY - JOUR A1 - Diehn, Sabrina Maria A1 - Schlaad, Helmut A1 - Kneipp, Janina T1 - Multivariate imaging for fast evaluation of in situ dark field microscopy hyperspectral data JF - Molecules : a journal of synthetic chemistry and natural product chemistry N2 - Dark field scattering microscopy can create large hyperspectral data sets that contain a wealth of information on the properties and the molecular environment of noble metal nanoparticles. For a quick screening of samples of microscopic dimensions that contain many different types of plasmonic nanostructures, we propose a multivariate analysis of data sets of thousands to several hundreds of thousands of scattering spectra. By using non-negative matrix factorization for decomposing the spectra, components are identified that represent individual plasmon resonances and relative contributions of these resonances to particular microscopic focal volumes in the mapping data sets. Using data from silver and gold nanoparticles in the presence of different molecules, including gold nanoparticle-protein agglomerates or silver nanoparticles forming aggregates in the presence of acrylamide, plasmonic properties are observed that differ from those of the original nanoparticles. For the case of acrylamide, we show that the plasmon resonances of the silver nanoparticles are ideally suited to support surface enhanced Raman scattering (SERS) and the two-photon excited process of surface enhanced hyper Raman scattering (SEHRS). Both vibrational tools give complementary information on the in situ formed polyacrylamide and the molecular composition at the nanoparticle surface. KW - localized surface plasmon resonances KW - gold nanoparticles KW - silver nanoparticles KW - dark field microscopy KW - acrylamide KW - hyperspectral imaging KW - non-negative matrix factorization KW - surface-enhanced Raman scattering (SERS) KW - surface-enhanced hyper Raman scattering (SEHRS) Y1 - 2022 U6 - https://doi.org/10.3390/molecules27165146 SN - 1420-3049 VL - 27 IS - 16 PB - MDPI CY - Basel ER - TY - JOUR A1 - Feng, Yiqing A1 - Kochovski, Zdravko A1 - Arenz, Christoph A1 - Lu, Yan A1 - Kneipp, Janina T1 - Structure and interaction of ceramide-containing liposomes with gold nanoparticles as characterized by SERS and Cryo-EM JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Due to the great potential of surface-enhanced Raman scattering (SERS) as local vibrational probe of lipid-nanostructure interaction in lipid bilayers, it is important to characterize these interactions in detail. The interpretation of SERS data of lipids in living cells requires an understanding of how the molecules interact with gold nanostructures and how intermolecular interactions influence the proximity and contact between lipids and nanoparticles. Ceramide, a sphingolipid that acts as important structural component and regulator of biological function, therefore of interest to probing, lacks a phosphocholine head group that is common to many lipids used in liposome models. SERS spectra of liposomes of a mixture of ceramide, phosphatidic acid, and phosphatidylcholine, as well as of pure ceramide and of the phospholipid mixture are reported. Distinct groups of SERS spectra represent varied contributions of the choline, sphingosine, and phosphate head groups and the structures of the acyl chains. Spectral bands related to the state of order of the membrane and moreover to the amide function of the sphingosine head groups indicate that the gold nanoparticles interact with molecules involved in different intermolecular relations. While cryogenic electron microscopy shows the formation of bilayer liposomes in all preparations, pure ceramide was found to also form supramolecular, concentric stacked and densely packed lamellar, nonliposomal structures. That the formation of such supramolecular assemblies supports the intermolecular interactions of ceramide is indicated by the SERS data. The unique spectral features that are assigned to the ceramide-containing lipid model systems here enable an identification of these molecules in biological systems and allow us to obtain information on their structure and interaction by SERS. Y1 - 2022 U6 - https://doi.org/10.1021/acs.jpcc.2c01930 SN - 1932-7447 SN - 1932-7455 VL - 126 IS - 31 SP - 13237 EP - 13246 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Heck, Christian A1 - Kanehira, Yuya A1 - Kneipp, Janina A1 - Bald, Ilko T1 - Placement of Single Proteins within the SERS Hot Spots of Self-Assembled Silver Nanolenses JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - This study demonstrates the bottom-up synthesis of silver nanolenses. A robust coating protocol enabled the functionalization of differently sized silver nanoparticles with DNA single strands of orthogonal sequence. Coated particles 10nm, 20nm, and 60nm in diameter were self-assembled by DNA origami scaffolds to form silver nanolenses. Single molecules of the protein streptavidin were selectively placed in the gap of highest electric field enhancement. Streptavidin labelled with alkyne groups served as model analyte in surface-enhanced Raman scattering (SERS) experiments. By correlated Raman mapping and atomic force microscopy, SERS signals of the alkyne labels of a single streptavidin molecule, from a single silver nanolens, were detected. The discrete, self-similar aggregates of solid silver nanoparticles are promising for plasmonic applications. KW - DNA origami KW - protein analysis KW - SERS KW - silver nanoparticles KW - streptavidin Y1 - 2018 U6 - https://doi.org/10.1002/anie.201801748 SN - 1433-7851 SN - 1521-3773 VL - 57 IS - 25 SP - 7444 EP - 7447 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Heck, Christian A1 - Kanehira, Yuya A1 - Kneipp, Janina A1 - Bald, Ilko T1 - Amorphous Carbon Generation as a Photocatalytic Reaction on DNA-Assembled Gold and Silver Nanostructures JF - Molecules N2 - Background signals from in situ-formed amorphous carbon, despite not being fully understood, are known to be a common issue in few-molecule surface-enhanced Raman scattering (SERS). Here, discrete gold and silver nanoparticle aggregates assembled by DNA origami were used to study the conditions for the formation of amorphous carbon during SERS measurements. Gold and silver dimers were exposed to laser light of varied power densities and wavelengths. Amorphous carbon prevalently formed on silver aggregates and at high power densities. Time-resolved measurements enabled us to follow the formation of amorphous carbon. Silver nanolenses consisting of three differently-sized silver nanoparticles were used to follow the generation of amorphous carbon at the single-nanostructure level. This allowed observation of the many sharp peaks that constitute the broad amorphous carbon signal found in ensemble measurements. In conclusion, we highlight strategies to prevent amorphous carbon formation, especially for DNA-assembled SERS substrates. KW - amorphous carbon KW - DNA origami KW - SERS KW - nanoparticle dimers KW - nanolenses Y1 - 2019 U6 - https://doi.org/10.3390/molecules24122324 SN - 1420-3049 VL - 24 IS - 12 PB - MDPI CY - Basel ER - TY - GEN A1 - Heck, Christian A1 - Kanehira, Yuya A1 - Kneipp, Janina A1 - Bald, Ilko T1 - Amorphous Carbon Generation as a Photocatalytic Reaction on DNA-Assembled Gold and Silver Nanostructures T2 - Mathematisch-Naturwissenschaftliche Reihe N2 - Background signals from in situ-formed amorphous carbon, despite not being fully understood, are known to be a common issue in few-molecule surface-enhanced Raman scattering (SERS). Here, discrete gold and silver nanoparticle aggregates assembled by DNA origami were used to study the conditions for the formation of amorphous carbon during SERS measurements. Gold and silver dimers were exposed to laser light of varied power densities and wavelengths. Amorphous carbon prevalently formed on silver aggregates and at high power densities. Time-resolved measurements enabled us to follow the formation of amorphous carbon. Silver nanolenses consisting of three differently-sized silver nanoparticles were used to follow the generation of amorphous carbon at the single-nanostructure level. This allowed observation of the many sharp peaks that constitute the broad amorphous carbon signal found in ensemble measurements. In conclusion, we highlight strategies to prevent amorphous carbon formation, especially for DNA-assembled SERS substrates. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 732 KW - amorphous carbon KW - DNA origami KW - SERS KW - nanoparticle dimers KW - nanolenses Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-430812 SN - 1866-8372 IS - 732 ER - TY - JOUR A1 - Heck, Christian A1 - Prinz, Julia A1 - Dathe, Andre A1 - Merk, Virginia A1 - Stranik, Ondrej A1 - Fritzsche, Wolfgang A1 - Kneipp, Janina A1 - Bald, Ilko T1 - Gold Nanolenses Self-Assembled by DNA Origami JF - ACS Photonics N2 - Nanolenses are self-similar chains of metal nanoparticles, which can theoretically 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 the 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. KW - plasmonics KW - DNA origami KW - SERS KW - nanolenses KW - gold nanoparticles Y1 - 2017 U6 - https://doi.org/10.1021/acsphotonics.6b00946 SN - 2330-4022 VL - 4 SP - 1123 EP - 1130 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zivanovic, Vesna A1 - Kochovski, Zdravko A1 - Arenz, Christoph A1 - Lu, Yan A1 - Kneipp, Janina T1 - SERS and Cryo-EM Directly Reveal Different Liposome Structures during Interaction with Gold Nanoparticles JF - The journal of physical chemistry letters N2 - The combination of gold nanoparticles with liposomes is important for nano- and biotechnology. Here, we present direct, label-free characterization of liposome structure and composition at the site of its interaction with citrate-stabilized gold nanoparticles by surface-enhanced Raman scattering (SERS) and cryogenic electron microscopy (cryo-EM). Evidenced by the vibrational spectra and cryo-EM, the gold nanoparticles destroy the bilayer structure of interacting liposomes in the presence of a high amount of citrate, while at lower citrate concentration the nanoparticles interact with the surface of the intact liposomes. The spectra of phosphatidylcholine and phosphatidylcholine/sphingomyelin liposomes show that at the site of interaction the lipid chains are in the gel phase. The SERS spectra indicate that cholesterol has strong effects on the contacts of the vesicles with the nanoparticles. By combining cryo-EM and SERS, the structure and properties of lipid nanoparticle composites could be tailored for the development of drug delivery systems. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpclett.8b03191 SN - 1948-7185 VL - 9 IS - 23 SP - 6767 EP - 6772 PB - American Chemical Society CY - Washington ER -