questions can be tackled with the existing arsenal of experimental variants of 2D IR
spectroscopy to promote the understanding of fundamentally new aspects in
chemistry, biology and materials science. The final part of the chapter introduces
several concepts of currently performed technical developments, which aim at
exploiting 2D IR spectroscopy as an analytical tool. Such developments embrace
the combination of 2D IR spectroscopy and plasmonic spectroscopy for ultrasensitive analytics, merging 2D IR spectroscopy with ultra-high-resolution microscopy
(nanoscopy), future variants of transient 2D IR methods, or 2D IR in conjunction
with microfluidics. It is expected that these techniques will allow for groundbreaking research in many new areas of natural sciences.
Keywords Ultrafast 2D IR spectroscopy Á Molecular structure Á Spectral
diffusion Á Energy transfer Á Chemical exchange Á Vibrational coupling Á Surface
spectroscopy Á Transient 2D IR spectroscopy Á 2D IR microscopy Á 2D
IR electrochemistry Á 2D IR Nanoscopy
1 Introduction
1.1 Ultrafast Infrared Vibrational Spectroscopy
Time-resolved infrared (IR) vibrational spectroscopy is a powerful method for
tackling a large number of open scientific questions from chemical, biological and
physical perspectives [1–11]. IR molecular spectroscopy has a high level of
chemical specificity, which leads to the possibility of straightforward sample
analysis based on characteristic absorption patterns from a broad range of functional
groups (ca. 600–4000 cm
-1 ). Vibrational frequencies, peak intensities, band shapes
and widths of IR transitions carry manifold information on molecular structure and
intermolecular interactions, thus making IR spectroscopy an incredibly valuable
tool for natural scientists. Adding a high time-resolution to IR spectroscopy even
expands the benefits, since this allows resolving dynamic and kinetic changes in
sample constitutions. Nowadays, a vast range of time scales can be investigated by
pulsed IR spectroscopy, ranging from femtoseconds to milliseconds or longer. In
particular, the field of ultrafast IR spectroscopy deals with vibrational dynamics
predominately on the femto- to nanosecond timescale and has seen a considerable
technological development in the last approximately 20 years. Consequently,
methods from this field are now an almost routinely available analytical tool.
Ultrafast IR spectroscopy allows the direct observation of dynamics on timescales
that closely match molecular motions in real time. This makes it possible to observe
directly the dynamics of vibrational relaxation, interactions of molecules with their
environment (e.g. solvation), vibrational dephasing or the dynamics of vibrational
echoes [8, 12–14]. An often invoked drawback of IR spectroscopy is, however, that
the absorption coefficients of a large range of functional groups are rather low
(\ 1000 M
-1 cm
-1 ). Such weak absorbance values considerably limit the obtainable signal strengths. Despite that undeniable limitation, constant progress in
Top Curr Chem (Z) (2017) 375:86
123
114
Reprinted from the journal
spectroscopy to promote the understanding of fundamentally new aspects in
chemistry, biology and materials science. The final part of the chapter introduces
several concepts of currently performed technical developments, which aim at
exploiting 2D IR spectroscopy as an analytical tool. Such developments embrace
the combination of 2D IR spectroscopy and plasmonic spectroscopy for ultrasensitive analytics, merging 2D IR spectroscopy with ultra-high-resolution microscopy
(nanoscopy), future variants of transient 2D IR methods, or 2D IR in conjunction
with microfluidics. It is expected that these techniques will allow for groundbreaking research in many new areas of natural sciences.
Keywords Ultrafast 2D IR spectroscopy Á Molecular structure Á Spectral
diffusion Á Energy transfer Á Chemical exchange Á Vibrational coupling Á Surface
spectroscopy Á Transient 2D IR spectroscopy Á 2D IR microscopy Á 2D
IR electrochemistry Á 2D IR Nanoscopy
1 Introduction
1.1 Ultrafast Infrared Vibrational Spectroscopy
Time-resolved infrared (IR) vibrational spectroscopy is a powerful method for
tackling a large number of open scientific questions from chemical, biological and
physical perspectives [1–11]. IR molecular spectroscopy has a high level of
chemical specificity, which leads to the possibility of straightforward sample
analysis based on characteristic absorption patterns from a broad range of functional
groups (ca. 600–4000 cm
-1 ). Vibrational frequencies, peak intensities, band shapes
and widths of IR transitions carry manifold information on molecular structure and
intermolecular interactions, thus making IR spectroscopy an incredibly valuable
tool for natural scientists. Adding a high time-resolution to IR spectroscopy even
expands the benefits, since this allows resolving dynamic and kinetic changes in
sample constitutions. Nowadays, a vast range of time scales can be investigated by
pulsed IR spectroscopy, ranging from femtoseconds to milliseconds or longer. In
particular, the field of ultrafast IR spectroscopy deals with vibrational dynamics
predominately on the femto- to nanosecond timescale and has seen a considerable
technological development in the last approximately 20 years. Consequently,
methods from this field are now an almost routinely available analytical tool.
Ultrafast IR spectroscopy allows the direct observation of dynamics on timescales
that closely match molecular motions in real time. This makes it possible to observe
directly the dynamics of vibrational relaxation, interactions of molecules with their
environment (e.g. solvation), vibrational dephasing or the dynamics of vibrational
echoes [8, 12–14]. An often invoked drawback of IR spectroscopy is, however, that
the absorption coefficients of a large range of functional groups are rather low
(\ 1000 M
-1 cm
-1 ). Such weak absorbance values considerably limit the obtainable signal strengths. Despite that undeniable limitation, constant progress in
Top Curr Chem (Z) (2017) 375:86
123
114
Reprinted from the journal