Showing papers by "Sebastian Schlücker published in 2018"
TL;DR: This feature article focuses on the design, synthesis and use of bifunctional NPs with both catalytic and plasmonic activity for in situ SERS detection of reactions catalyzed by metal NPs.
84 citations
TL;DR: An unprecedented structural and plasmonic uniformity at the single-particle level is observed since inhomogeneities resulting from variations in gap morphology are eliminated.
Abstract: Ideal dimers comprising gold nanoparticles with a smooth surface and high sphericity are synthesized by a substrate-based assembly strategy with efficient cetyltrimethylammonium bromide removal. An unprecedented structural and plasmonic uniformity at the single-particle level is observed since inhomogeneities resulting from variations in gap morphology are eliminated. Single ideal dimers are analyzed by polarization-resolved dark-field scattering spectroscopy. Contributions from transverse as well as quadrupolar and octupolar longitudinal plasmon coupling modes can be discriminated because of their orthogonal polarization behavior. The assignment of these higher order coupling modes is supported by computer simulations.
54 citations
TL;DR: In this article, a dual-sensing scheme was proposed to detect surface-enhanced Raman scattering and fluorescence emission of the same probe using a β-carotenal monolayer.
Abstract: A reduction in the number of loss decay channels present in optical nanoantennas could help enhance an emitter’s radiation efficiency. These losses get amplified for emitters in close proximity to metallic surfaces, such as for self-assembled monolayers, reducing the fluorescence rate. However, such a proximity strongly enhances Raman scattering. A dual-sensing scheme should bypass this shortcoming, and switching from metals to high refractive index dielectrics could aid in that direction. In order to show this, we fabricated silicon nanodimers and coated them with a β-carotenal monolayer for detecting surface-enhanced Raman scattering and fluorescence emission of the same probe. We obtained a surface-enhanced Raman scattering (SERS) factor of 1720 ± 300 for the C–C bond stretching of the polyene chain and a surface fluorescence enhancement (SEF) factor of 470 ± 90. Furthermore, our theoretical studies of different materials and emitters located on the surface of nanostructures demonstrate that low-loss d...
47 citations
TL;DR: Different classes of plasmonic nanoparticles functionalized with the non-resonant Raman reporter molecule 4-MBA are tested for their SERS signal brightness at the single-particle level: gold nanoparticles, hollow gold/silver nanoshells, gold nanostars, and gold core/gold satellite particles.
Abstract: Different classes of plasmonic nanoparticles functionalized with the non-resonant Raman reporter molecule 4-MBA are tested for their SERS signal brightness at the single-particle level: gold nanoparticles, hollow gold/silver nanoshells, gold nanostars, and gold core/gold satellite particles. Correlative SERS/SEM experiments on a set of particles from each class enable the unambiguous identification of single particles by electron microscopy as well as the characterization of both their elastic (LSPR) and inelastic (SERS) scattering spectra. Experimental observations are compared with predictions from FEM computer simulations based on 3D models derived from representative TEM/SEM images. Single gold nanostars and single gold core/gold satellite particles exhibit a detectable SERS signal under the given experimental conditions, while single gold nanoparticles and single hollow gold/silver nanoshells are not detectable.
45 citations
TL;DR: It is found that the antigen retrieval method strongly influences the extent of nonspecific binding of the antibody-SERS NP conjugates to the tissue, and PIER is recommended for future NP-based tissue immunostaining such as immuno- SERS microscopy.
Abstract: Immunohistochemical analysis of formalin-fixed paraffin-embedded (FFPE) tissues provides important diagnostic and prognostic information in pathology. Metal nanoparticles (NPs) and, in particular, surface-enhanced Raman scattering (SERS) nanotags as a new class of labeling reagents are promising to be used for multiplexed protein profiling on tissue sections. However, nonspecific binding of NPs onto the tissue specimens greatly hampers their clinical applications. In this study, we found that the antigen retrieval method strongly influences the extent of nonspecific binding of the antibody–SERS NP conjugates to the tissue. Our SERS labels comprised ca. 70 nm Au nanostars coated with ethylene glycol-modified Raman reporter molecules for hydrophilic stabilization and subsequent covalent bioconjugation to antibodies. We systematically investigated the influence of heat- and protease-induced epitope retrieval (HIER and PIER, respectively) on the immunostaining quality of prostate-specific antigen (PSA) on hum...
29 citations
TL;DR: The proof of concept for a rapid and sensitive detection of TNF-α using a magnetic bead pull-down assay in combination with surface-enhanced Raman scattering (SERS) is demonstrated and multiplexing potential of this SERS-based detection scheme is exemplarily demonstrated.
Abstract: Tumor necrosis factor alpha (TNF-α) is a cytokine with significance in early diagnosis of cardiovascular diseases, obesity and insulin resistance. We demonstrate the proof of concept for a rapid and sensitive detection of TNF-α using a magnetic bead pull-down assay in combination with surface-enhanced Raman scattering (SERS). The use of purified and highly SERS-active small clusters of gold nanoparticles (AuNP) provides the high sensitivity of the assay with a limit of detection of ca. 1 pg/mL. Continuous density gradient centrifugation was employed for separating the very bright silica-encapsulated AuNP dimers and trimers from the significantly weaker AuNP monomers. Negative control experiments with other cytokines (IL-6, IL-8) and bovine serum albumin (BSA) confirm the high specificity of the assay, but indicate also space for future improvements by further reducing non-specific binding between proteins and the SERS nanotags. The multiplexing potential of this SERS-based detection scheme is exemplarily demonstrated by using a set of three spectrally distinct and highly SERS-active AuNP clusters with unique spectral barcodes.
22 citations
TL;DR: Investigating the photon conversion efficiency (PCE) as a function of the SiO2 shell thickness, a strong competition between the ELEF and SET effects in the performance of the devices with the NPs embedded in the active layers is found, leading to a maximum PCE enhancement at the shell thickness of 5 nm.
Abstract: Plasmonic metal nanostructures are widely used as subwavelength light concentrators to enhance light harvesting of organic solar cells through two photophysical effects, including enhanced local electric field (ELEF) and antenna-amplified light scattering (AALS), while their adverse quenching effect from surface energy transfer (SET) should be suppressed. In this work, a comprehensive study to unambiguously distinguish and quantitatively determine the specific influence and contribution of each effect on the overall performance of organic solar cells incorporated with Ag@SiO2 core-shell nanoparticles (NPs) is presented. By investigating the photon conversion efficiency (PCE) as a function of the SiO2 shell thickness, a strong competition between the ELEF and SET effects in the performance of the devices with the NPs embedded in the active layers is found, leading to a maximum PCE enhancement of 12.4% at the shell thickness of 5 nm. The results give new insights into the fundamental understanding of the photophysical mechanisms responsible for the performance enhancement of plasmonic organic solar cells and provide important guidelines for designing more-efficient plasmonic solar cells in general.
19 citations
TL;DR: Dense layers of overlapping three-dimensional gold nanodendrites characterized by high specific surfaces as well as by abundance of sharp edges and vertices creating high densities of SERS hotspots are promising substrates for SERS-based sensing and catalysis.
Abstract: Dense layers of overlapping three-dimensional (3D) gold nanodendrites characterized by high specific surfaces as well as by abundance of sharp edges and vertices creating high densities of SERS hotspots are promising substrates for SERS-based sensing and catalysis. We have evaluated to what extent structural features of 3D gold nanodendrite layers can be optimized by the initiation of 3D gold nanodendrite growth at gold particles rationally positioned on silicon wafers. For this purpose, galvanic displacement reactions yielding 3D gold nanodendrites were guided by hexagonal arrays of parent gold particles with a lattice constant of 1.5 μm obtained by solid-state dewetting of gold on topographically patterned silicon wafers. Initiation of the growth of dendritic features at the edges of the gold particles resulted in the formation of 3D gold nanodendrites while limitation of dendritic growth to the substrate plane was prevented. The regular arrangement of the parent gold particles supported the formation of dense layers of overlapping 3D gold nanodendrites that were sufficiently homogeneous within the resolution limits of Raman microscopy. Consequently, SERS mapping experiments revealed a reasonable degree of uniformity. The proposed preparation algorithm comprises only bottom-up process steps that can be carried out without the use of costly instrumentation.
14 citations
TL;DR: This contribution presents an optical setup for performing correlative single-particle imaging using laser light-sheet illumination: the first detection channel records elastic light scattering (Rayleigh/Mie), while the second channel detects inelasticLight scattering (Raman) or fluorescence.
Abstract: Many applications of nano- and microparticles require molecular functionalization. Assessing the heterogeneity of a colloidal sample in terms of its molecular functionalization is highly desirable but not accessible by conventional ensemble experiments. Retrieving this information necessitates single-particle experiments which simultaneously detect both functionalized and nonfunctionalized particles via two separate imaging channels. In this contribution, we present an optical setup for performing correlative single-particle imaging using laser light-sheet illumination: the first detection channel records elastic light scattering (Rayleigh/Mie), while the second channel detects inelastic light scattering (Raman) or fluorescence. The instrument is tested with Raman reporter-functionalized SERS-active metal nanoparticles (core/satellite silver nanoparticles, dimers and monomers of gold nanoparticles) and fluorophore-functionalized colloids (fluorescent polymer microparticles, dye-labeled protein on gold nan...
8 citations
TL;DR: It is demonstrated as proof of concept that UVRR can be used for probing the recognition between a multivalent supramolecular ligand and acidic residues in leucine zipper, an α-helical structural motif of many proteins.
Abstract: Ultraviolet resonance Raman (UVRR) spectroscopy is a selective, sensitive and label-free vibrational spectroscopic technique. Here, we demonstrate as proof of concept that UVRR can be used for probing the recognition between a multivalent supramolecular ligand and acidic residues in leucine zipper, an α-helical structural motif of many proteins.
6 citations
01 Jan 2018
TL;DR: This book chapter will first give a very brief tutorial on the fundamentals of SERS, followed by an introduction into the concept and current designs of target-specific SERS probes based on noble metal NPs.
Abstract: Immuno-SERS (iSERS) microscopy is an emerging imaging technique in tissue-based cancer diagnostics, which is based on antibodies labelled with SERS-active noble metal nanoparticles (NPs) in conjunction with Raman microspectroscopy for localizing target proteins. Advantages of SERS over existing labeling approaches include its high capacity for spectral multiplexing (parallel detection of target molecules), quantification (based on the characteristic SERS signatures), high photostability (no or minimal photobleaching), minimization of autofluorescence from biological specimens (via red to near-infrared excitation), and the technical advantage of using only a single laser excitation line. In this book chapter, we will first give a very brief tutorial on the fundamentals of SERS, followed by an introduction into the concept and current designs of target-specific SERS probes based on noble metal NPs. Next, the fast developing applications of iSERS microscopy for tissue-based cancer diagnostics are highlighted, and finally the challenges and future perspectives of this emerging field are presented.