Showing papers by "Sebastian Schlücker published in 2010"

Synthesis of Glass‐Coated SERS Nanoparticle Probes via SAMs with Terminal SiO2 Precursors

Abstract: Surface-enhanced Raman scattering (SERS) combines the benefits of vibrational Raman scattering with highest sensitivity, using nanostructures that can support localized plasmon resonances. [1‐4] The main application of SERS is the label-free detection of analytes. [5‐8] An alternative and more recent approach uses SERS as a readout method in bioanalytical applications: the selective detection of proteins and oligonucleotides is achieved by employing target-specific SERS nanoparticle probes. [7‐11] The central motivation for this strategy is the option to detect numerous target molecules within a single measurement (multiplexing). The basis of spectral multiplexing in SERS arises from the small linewidth of vibrational Raman bands compared with the significantly broader emission profiles of molecular fluorophores. [12,13] Further important advantages are quantification of target concentration and the extreme sensitivity of SERS, in particular SERRS (surface-enhanced resonance Raman scattering). [14,15] Additionally, the simultaneous excitation of spectrally distinct SERS nanoparticle probes requires only a single laser wavelength. Different designs for nanoparticle-based SERS probes (SERSlabels,SERSnanotags)areavailable,whichdifferinthe plasmonic nanostructure, the Raman reporter molecule, and the optional protective shell. [9,16‐18] Using a self-assembled monolayer(SAM)ofRamanreportermoleculesonthesurface of the nanoparticle has several advantages. [18‐22] Firstly,

Tunable narrow band filter for CARS microscopy

Abstract: In this letter we present an approach to CARS microscopy, which compromises between fast acquisition rates and the amount of chemical information obtained. By using a light modulator as tunable filter in concert with narrowband pump and broadband Stokes pulses, we demonstrate an experimental arrangement, which allows for fast electronic switching between CARS images recorded at different Raman resonances without the need for any optical adjustment.

FT-IR and FT-Raman spectra, ab initio and density functional computations of the vibrational spectra, molecular geometry, atomic charges and some molecular properties of the biomolecule 5-iodouracil

Abstract: Density functional calculations (DFT) by various methods were performed to clarify wavenumber assignments of the experimental observed bands. A comparison with the molecule of uracil was made, and specific scale factors were deduced and employed in the predicted wavenumbers of 5-IU. Comparisons were also performed with other halo-uracil derivatives. The scaled wavenumbers were compared with IR and Raman experimental data. Good reproduction of the experimental wavenumbers is obtained and the % error is very small in the majority of cases. The equilibrium geometry of 5-IU was also calculated at several levels, as well as the atomic charges and several thermodynamic parameters. All the tautomer forms of 5-iodouracil were determined and optimized. Several general conclusions were underlined.

Hydrogen bonding in the pyrimidine/ formamide system: a concentration-dependent Raman and DFT study

Abstract: High-resolution Raman spectra of pyrimidine (PD) and formamide (FA) mixtures with different compositions recorded in the ring breathing region of PD (ν1 ∼ 991 cm−1) are presented. The dilution of PD with FA leads to the appearance of a new band at ν1′ ∼ 994 cm−1, which is assigned to hydrogen-bonded PD:FA species. From a quantitative analysis of the concentration-dependent Raman spectra, the average number of FA molecules in the first solvation sphere of PD is determined as being equal to 2. This value is supported by density functional theory (DFT) calculations: a symmetric 1:2 complex is the most stable species among various hydrogen-bonded PD:FA clusters with stoichiometries ranging from 1:1 to 1:4. A qualitative explanation for the blue shift of the ν1 mode upon complexation is given. Additionally, we have observed not only similarities but also some differences with respect to the PD:water system. Copyright © 2010 John Wiley & Sons, Ltd.

SERS microscopy: plasmonic nanoparticle probes and biomedical applications

Abstract: Nanoparticle probes for use in targeted detection schemes and readout by surface-enhanced Raman scattering (SERS) comprise a metal core, Raman reporter molecules and a protective shell. One design of SERS labels specifically optimized for biomedical applications in conjunction with red laser excitation is based on tunable gold/silver nanoshells, which are completely covered by a self-assembled monolayer (SAM) of Raman reporters. A shell around the SAM-coated metal core stabilizes the colloid and prevents particle aggregation. The optical properties and SERS efficiencies of these plasmonic nanostructures are characterized both experimentally and theoretically. Subsequent bioconjugation of SERS probes to ligands such as antibodies is a prerequisite for the selective detection of the corresponding target molecule via the characteristic Raman signature of the label. Biomedical imaging applications of SERS-labeled antibodies for tumor diagnostics by SERS microscopy are presented, using the localization of the tumor suppressor p63 in prostate tissue sections as an example.

Two Channel Microfluidic CARS for Quantifying Pure Vibrational Contrast of Model Analytes

Abstract: We discuss the combination of a CARS-imaging system with mi crofluidics. Such system is a versatile tool to quantify the relative contributions of resonant and non-resonant scattering at the CARS frequency. We will show that the two-channel microfluidic chip employed in combination with deuter ated isotopomers as an intern al standard allows for fast and quantitative detection of organic molecules by CARS microscopy. The experimental design enables the simultaneous measurement of both the chemically relevant Raman-resonant signal and the non-Raman-resonant background. Keywords: Coherent anti-Stokes Raman microscopy, Raman spectroscopy, microfluidics, nonresonant background, analytical methods, isotopomers 1. INTRODUCTION Over the last decade Raman microspectroscopy 1-17 matured into a powerful widespread technique for biomedical diagnostics. This success is based on th e capability of the technique to record “chemical images” based on intrinsically label-free vibrational