Article pubs.acs.org/JPCC
Surface Enhancement in Ultrafast 2D ATR IR Spectroscopy at the Metal-Liquid Interface Jan Philip Kraack,*,† Andres Kaech,‡ and Peter Hamm*,† †
Department of Chemistry and ‡Center for Microscopy and Image Analysis, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland S Supporting Information *
ABSTRACT: We investigate surface enhancement in two-dimensional attenuated total reflectance infrared (2D ATR IR) spectroscopy from organic monolayers (MLs) at metal−liquid interfaces. We consider MLs from both aromatic and aliphatic organic samples equipped with nitrile and azide functional groups, both of which are widely used as local vibrational probes in ultrafast spectroscopy. Polarization-dependent 2D ATR IR spectroscopy indicates the excitation of local hot spots formed between gold (Au) nanoparticles as the dominant origin of signal enhancement. The highest enhancement factors (∼50) are observed in the case of aromatic nitrile MLs, whereas modest values (
