Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Poster Session II (Metals; Nanostructures at surfaces; Surface or interface magnetism; Spin-Orbit Interaction at Surfaces; Electron and spin dynamics; Surface dynamics; Methods; Theory and computation of electronic structure)
O 36.40: Poster
Dienstag, 15. März 2011, 18:30–22:00, P4
Surface-enhanced and tip-enhanced Raman spectroscopy of biological molecules on nanostructured metallic surfaces — •Laura E. Hennemann1, Andreas Kolloch2, Josip Mihaljevic1, Kai Braun1, Alfred J. Meixner1, and Dai Zhang1 — 1Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 8, 72076 Tübingen, Germany — 2Department of Physics, University of Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany
We use a custom built apertureless scanning near-field optical microscope (SNOM) to investigate several kinds of biological molecules. The setup is an extended parabolic mirror based confocal microscope working with higher order laser modes in order to tune the polarization of the light in its focus. We detected the presence of a (sub)monolayer of biological molecules ranging from DNA bases to double stranded DNA by collecting their unique Raman fingerprint spectrum.
In order to detect such small amounts of molecules, we performed surface-enhanced Raman scattering (SERS) or tip-enhanced Raman scattering (TERS). For SERS, either the irregular rough edges of evaporated noble metal grids or regular arrays of gold nano triangles served as enhancing substrates. We compared the plasmonic properties of gold triangles of different aspect ratios and on different substrates to optimize the electromagnetic enhancement for the 632.8 nm laser excitation. The obtained optical patterns were compared to those computed in simulations.
In the case of TERS, an electrochemically etched sharp gold tip (approx. 20 nm tip apex diameter) was approached to the surface, thus acting simultaneously as a scanning probe microscopy tip for topographic measurements and as a near-field antenna collecting optical information. We collected TERS spectra of single calf thymus DNA molecules immobilized on smooth Au (111) surfaces. Strongly enhanced spectra were obtained both in the SERS and in the TERS measurements.
References: [1] "Parabolic mirror-assisted tip-enhanced spectroscopic imaging for non-transparent materials" D. Zhang, X. Wang, K. Braun, H.-J. Egelhaaf, M. Fleischer, L. Hennemann, H. Hintz, C. Stanciu, C.J. Brabec, D.P. Kern, A.J. Meixner, Journal of Raman Spectroscopy 40 (2009) 1371-1376. [2] "Surface- and Tip-Enhanced Raman Spectroscopy of DNA" L.E. Hennemann, A.J. Meixner, D. Zhang, Spectroscopy Biomedical Applications 24 (2010) 119-124.