Showing papers by "Sebastian Schlücker published in 2019"

Rapid, Quantitative, and Ultrasensitive Point-of-Care Testing: A Portable SERS Reader for Lateral Flow Assays in Clinical Chemistry.

Abstract: The design of a portable Raman/SERS-LFA reader with line illumination using a custom-made fiber optic probe for rapid, quantitative, and ultrasensitive point-of-care testing (POCT) is presented. The pregnancy hormone human chorionic gonadotropin (hCG) is detectable in clinical samples within only 2-5 s down to approximately 1.6 mIU mL-1 . This acquisition time is several orders of magnitude shorter than those of existing approaches requiring expensive Raman instrumentation, and the method is 15-times more sensitive than a commercially available lateral flow assay (LFA) as the gold standard. The SERS-LFA technology paves the way for affordable, quantitative, and ultrasensitive POCT with multiplexing potential in real-world applications, ranging from clinical chemistry to food and environmental analysis as well as drug and biowarfare agent testing.

Spectral Screening of the Energy of Hot Holes over a Particle Plasmon Resonance

Abstract: Plasmonic hot carriers have been recently identified as key elements for photocatalysis at visible wavelengths. The possibility to transfer energy between metal plasmonic nanoparticles and nearby molecules depends not only on carrier generation and collection efficiencies but also on their energy at the metal–molecule interface. Here an energy screening study was performed by monitoring the aniline electro-polymerization reaction via an illuminated 80 nm gold nanoparticle. Our results show that plasmon excitation reduces the energy required to start the polymerization reaction as much as 0.24 eV. Three possible photocatalytic mechanisms were explored: the enhanced near field of the illuminated particle, the temperature increase at the metal–liquid interface, and the excited electron–hole pairs. This last phenomenon is found to be the one contributing most prominently to the observed energy reduction.

Surface Plasmon Coupling in Dimers of Gold Nanoparticles: Experiment and Theory for Ideal (Spherical) and Nonideal (Faceted) Building Blocks

Abstract: The surface plasmon (SP) coupling in dimers of spherical and faceted gold nanoparticles was investigated experimentally and computationally at the single-particle level. Individual ideal dimers of two spherical gold nanoparticles with a constant gap, filled by a self-assembled monolayer of 1,8-octanedithiol linker molecules, exhibit highly uniform dark-field (DF) scattering spectra. In contrast, single nonideal dimers of two faceted gold nanoparticles with the same constant gap exhibit a high degree of spectral nonuniformity. We attribute this significant spectral heterogeneity to the many possible gap morphologies, that is, the many possible configurations of the crystal facet orientations at the junction of the two faceted particles in nonideal dimers. This configurational complexity is reduced in so-called hybrid dimers, which comprise an ideal spherical particle and a nonideal faceted particle. Hybrid dimers were therefore investigated theoretically and experimentally for revealing the influence of cr...

Size-selective optical printing of silicon nanoparticles through their dipolar magnetic resonance

Abstract: Silicon nanoparticles possess unique size-dependent optical properties due to their strong electric and magnetic resonances in the visible range. However, their widespread application has been limited, in comparison with other (e.g., metallic) nanoparticles, because their preparation on monodisperse colloids remains challenging. Exploiting the unique properties of Si nanoparticles in nano- and microdevices calls for methods able to sort and organize them from a colloidal suspension onto specific positions of solid substrates with nanometric precision. We demonstrate that surfactant-free silicon nanoparticles of a predefined and narrow (σ < 10 nm) size range can be selectively immobilized on a substrate by optical printing from a polydisperse colloidal suspension. The size selectivity is based on differential optical forces that can be applied on nanoparticles of different sizes by tuning the light wavelength to the size-dependent magnetic dipolar resonance of the nanoparticles.

Dynamics of hot electron generation in metallic nanostructures: general discussion

Abstract: Javier Aizpurua, Michael Ashfold, Francesca Baletto, Jeremy Baumberg, Phillip Christopher, Emiliano Cortés, Bart de Nijs, Yuri Diaz Fernandez, Julian Gargiulo, Sylwester Gawinkowski, Naomi Halas, Ruben Hamans, Bartlomiej Jankiewicz, Jacob Khurgin, Priyank Vijaya Kumar, Jie Liu, Stefan Maier, Reinhard J. Maurer, A Mount, Niclas Sven Mueller, Rupert Oulton, Matteo Parente, Jeong Y. Park, John Polanyi, Jhon Quiroz, Sebastian Rejman, Sebastian Schlücker, Zachary Schultz, Yonatan Sivan, Giulia Tagliabue, Madasamy Thangamuthu, Laura TorrenteMurciano, Xiaofei Xiao, Anatoly Zayats and Chao Zhan

Plasmonic Effects of Au Nanoparticles on the Vibrational Sum Frequency Spectrum of 4-Nitrothiophenol

Abstract: Vibrational sum frequency spectra (vSFS) of 4-nitrothiophenol (4-NTP) have been utilized to study plasmonic effects arising from its interaction with gold nanoparticles (Au NPs). To this end three systems have been studied: 4-NTP adsorbed on deposited Au nanoparticles, a self-assembled monolayer of 4-NTP on flat Au with dispersed Au NPs atop and, as reference, a self-assembled monolayer of 4-NTP. For 4-NTP on 50 and 80 nm Au NPs an enhancement of the SF intensity due to plasmonic effects by less than 1 order of magnitude is inferred in comparison to the monolayer system after taking the particle density into account. The addition of Au NPs to the monolayer system on flat Au also selectively enhances the response to an in-plane field component of the 532 nm upconversion light.

Evaluation of 3D gold nanodendrite layers obtained by templated galvanic displacement reactions for SERS sensing and heterogeneous 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 micrometers obtained by solid-state dewetting of gold on topographically patterned silicon wafers. Initiation of the growth of dendritic features at 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 microscopes. 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 use of costly instrumentation.

New materials for hot electron generation: general discussion

Abstract: ...a general discussion ...in addressing the need for sustainable plasmonic materials. This is particularly relevant for photocatalysis field since we have a limited supply of Pt and Pd on this planet.

Vibrational Spectroscopic Characterization of 2-(2,4-Dinitrobenzyl)-pyridine (α-DNBP) in Solution by Polarization-Resolved Spontaneous Raman Scattering and Broadband CARS.

Abstract: The photochromic molecule 2-(2,4-dinitro-benzyl)-pyridine (α-DNBP) is characterized in solution by a combination of density functional theory employing a polarizable continuum model and polarization-resolved spontaneous and nonlinear Raman spectroscopies. By the comparison of theoretically predicted wavenumber positions and depolarization ratios with the experimental spectra acquired under electronically nonresonant conditions, polarized and depolarized Raman bands are assigned. Specifically, the symmetric stretching vibrations of the two nitro groups in ortho and para positions to the pyridine ring can be experimentally differentiated, mainly because of their different Raman depolarization ratios, which supports our prediction from theory. Compared to the polarization-resolved spontaneous Raman experiments, the vibrational spectroscopic differentiation of the two nitro groups is more pronounced in time-delayed polarization-resolved coherent anti-Stokes Raman scattering experiments. Overall, this linear and nonlinear vibrational spectroscopic characterization of the CH form paves the way for the interpretation of future time-resolved pump/nonlinear Raman probe studies on the ultrafast photoinduced intramolecular proton transfer in α-DNBP involving a nitro group as an intramolecular proton acceptor.

Applications in catalysis, photochemistry, and photodetection: general discussion.

Abstract: (600:[600]600) Sylwester Gawinkowski opened a general discussion of the paper by Jorge Salmon-Gamboa: Why you are using SiO 2 nanoparticles? Do they have any function or are they only the substrate to attach other active nano-particles to? You have shown that only gold nanoparticles attached to silica nanoparticles do not inuence the rate of reaction signicantly. You have also demonstrated that adding platinum decorations on the gold nanoparticles causes a strong increase in the reaction rate. The signicance of the gold nanoparticles would be more clearly shown with a simple experiment in which you have no gold nanoparticles but still have platinum decorations. Jorge Salmon-Gamboa replied: Silica nanoparticles were chosen as a nano-sized inert substrate for Au nanoparticles. This choice of substrate provides a larger surface area covered with the active Au-Pt nanoparticles, in contrast to the situation when the active particles are placed directly onto a at substrate. Aiming for applications, the SiO 2-Au-Pt nanoparticles can then in turn be attached onto a at surface, forming a solid device that can be submerged into water, avoiding the problem of water contamination by nanoparticles. The role of the Au nano-particles was investigated. Under illumination in the LSP spectral band (556-566 nm), SiO 2-Pt did not enhance the reaction rate. In contrast, under the same conditions, SiO 2-Au-Pt showed a considerably enhanced rate, proving that hot carriers were generated in Au (see Fig. 1 below). (601:[601]601) Yuri Diaz Fernandez continued the discussion: I have two questions: (1) Can you comment on the dispersity of the size distribution of metal and SiO 2 particles and how well controlled are these in your system?

Precision Plasmonics with Monomers and Dimers of Spherical Gold Nanoparticles: Nonequilibrium Dynamics at the Time and Space Limits

Abstract: Monomers and dimers of spherical gold nanoparticles (NPs) exhibit highly uniform plasmonic properties at the single-particle level due to their high structural homogeneity (precision plasmonics). Recent investigations in precision plasmonics have largely focused on static properties using conventional techniques such as transmission electron microscopy and optical dark-field microscopy. In this Feature Article, we first highlight the application of femtosecond time-resolved electron diffraction for monitoring the nonequilibrium dynamics of spherical gold NPs after ultrafast optical excitation. The analysis of the transient diffraction patterns allows us to directly obtain quantitative information on the incoherent excitation of the lattice, that is, heating upon electron–lattice equilibration, as well as on the development of strain due to lattice expansion on picosecond time scales. The controlled assembly of two spherical gold NPs into a dimer with a few nanometers gap leads to unique optical properties. Specifically, extremely high electric fields (hot spot) in the gap are generated upon resonant optical excitation. Conventional optical microscopy cannot spatially resolve this unique hot spot due to the optical diffraction limit. We therefore employed nonlinear photoemission electron microscopy to visualize hot spots in single dimers of spherical gold NPs. A quantitative comparison of different single dimers confirms the homogeneity of the hot spots on the single-particle level. Overall, these initial results are highly encouraging because they pave the way to investigate nonequilibrium dynamics in highly uniform plasmonic nanostructures at the time and space limits.

Size-Selective Optical Printing of Silicon Nanoparticles through Their Dipolar Magnetic Resonance

Abstract: Surfactant-free silicon nanoparticles of a predefined and narrow (σ < 10 nm) size range can be selectively immobilized on a substrate by optical printing from a polydisperse colloidal suspension. The size selectivity is based on differential optical forces that can be applied on different sized nanoparticles by tuning the light wavelength to their size-dependent magnetic dipolar resonance.