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Surface enhancement in ultrafast 2D ATR IR spectroscopy at the metal-liquid interface


Kraack, Jan Philip; Kaech, Andres; Hamm, Peter (2016). Surface enhancement in ultrafast 2D ATR IR spectroscopy at the metal-liquid interface. Journal of Physical Chemistry C, 120(6):3350-3359.

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 (similar to 50) are observed in the case of aromatic nitrile MLs, whereas modest values (<10) are found for aliphatic azide and nitrile groups. Different contributions to signal enhancement are evaluated systematically and indicate the presence of both electromagnetic enhancement and contributions from molecular properties. The obtained enhancement factors are promising to allow 2D ATR IR spectroscopy to become applicable as a versatile technique for the detection of ultrafast structural dynamics in even low-absorbing organic MLs at solid-liquid interfaces.

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 (similar to 50) are observed in the case of aromatic nitrile MLs, whereas modest values (<10) are found for aliphatic azide and nitrile groups. Different contributions to signal enhancement are evaluated systematically and indicate the presence of both electromagnetic enhancement and contributions from molecular properties. The obtained enhancement factors are promising to allow 2D ATR IR spectroscopy to become applicable as a versatile technique for the detection of ultrafast structural dynamics in even low-absorbing organic MLs at solid-liquid interfaces.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
08 University Research Priority Programs > Solar Light to Chemical Energy Conversion
Dewey Decimal Classification:540 Chemistry
Language:English
Date:18 February 2016
Deposited On:23 Jan 2017 14:03
Last Modified:29 Jan 2017 06:58
Publisher:American Chemical Society (ACS)
ISSN:1932-7447
Funders:Swiss National Foundation, University Research Priority Program (URPP) for solar light to chemical energy conversion (LightChEC)
Publisher DOI:https://doi.org/10.1021/acs.jpcc.5b11051

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