2D attenuated total reflectance infrared spectroscopy reveals ultrafast vibrational dynamics of organic monolayers at metal-liquid interfaces

Kraack, Jan Philip; Lotti, Davide; Hamm, Peter

doi:10.1063/1.4916915

Cited by 31 publications

(103 citation statements)

References 70 publications

(121 reference statements)

Supporting

Mentioning

101

Contrasting

Order By: Relevance

“…Thus, heterogeneity of the CN stretch transition frequency distribution is significantly increased upon adsorption and spectral diffusion of the CN group is slowed down by at least a factor of twenty upon immobilization of the molecules. This deceleration is thus much larger than reported previously for aliphatic azide groups in MLs under similar conditions 18 . The experiments also show that the immersion of the MLs with solvent fastens the spectral diffusion.…”

Section: Resultscontrasting

confidence: 45%

“…18 In brief, self-assembled monolayers (MLs) are generated on Au-coated CaF2 prisms using standard procedures. 30 Thin (nanometer) layers of Au are sputtered onto CaF2 prisms which are then incubated with strongly diluted solutions (1 mM) of para-Mercaptobenzonitrile (abbreviated as PhCN in the following) for 12 h, rinsed with ethanol and water and dried in a stream of nitrogen.…”

Section: Sample Preparationmentioning

confidence: 99%

“…18,19 Here, we explore the capability of the method further by providing evidence that 2D ATR IR spectroscopy can be used to study ultrafast dynamics of samples with intrinsically low IR extinction coefficients (< 200 M -1 cm -1 ) at substantial sub-ML coverage. In particular, we study MLs and mixed MLs (MMLs) of organic nitrile (CN) stretch vibrations covalently attached to thin films of gold (Au).…”

Section: Introductionmentioning

confidence: 99%

“…18,19 . ATR spectroscopy is based on the reflecting properties of interfaces between materials of different refractive indices when certain experimental conditions are fulfilled.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Surface-enhanced, multi-dimensional attenuated total reflectance spectroscopy

2015

Self Cite

View full text Add to dashboard Cite

Ultrafast two-dimensional infrared spectroscopy (2D IR) spectroscopy is performed in attenuated total reflectance (ATR) geometry with the Kretschmann configuration in order to measure femtosecond to picosecond dynamics of selfassembled monolayers on gold-coated solid-liquid interfaces. In the monolayers low-absorbing (<200 M-1 cm-1) nitrile functional groups are used as local vibrational probes to monitor vibrational relaxation and spectral diffusion in dependence of different environments of the nitrile group. By comparing spectral diffusion dynamics of the vibrational probe in bulk solution and in the monolayer we find that the dynamics are slowed down by more than a factor of 20 upon immobilization of the sample. Moreover, spectral diffusion dynamics are affected by the local environment within the monolayers as evidenced by 2D ATR IR experiments on mixed monolayers with different aliphatic and aromatic coadsorbates. The results are interpreted in terms of absent excitation energy-transfer as well as solvation dynamics around the nitrile vibrational probe. Our results demonstrate that 2D ATR IR spectroscopy offers the possibility to obtain ultrafast dynamics from sub-monolayer coverages of even low-absorbing vibrational probes such as nitrile functional groups. ABSTRACTUltrafast two-dimensional infrared spectroscopy (2D IR) spectroscopy is performed in attenuated total reflectance (ATR) geometry with the Kretschmann configuration in order to measure femtosecond to picosecond dynamics of selfassembled monolayers on gold-coated solid-liquid interfaces. In the monolayers low-absorbing (<200 M -1 cm -1 ) nitrile functional groups are used as local vibrational probes to monitor vibrational relaxation and spectral diffusion in dependence of different environments of the nitrile group. By comparing spectral diffusion dynamics of the vibrational probe in bulk solution and in the monolayer we find that the dynamics are slowed down by more than a factor of 20 upon immobilization of the sample. Moreover, spectral diffusion dynamics are affected by the local environment within the monolayers as evidenced by 2D ATR IR experiments on mixed monolayers with different aliphatic and aromatic coadsorbates. The results are interpreted in terms of absent excitation energy-transfer as well as solvation dynamics around the nitrile vibrational probe. Our results demonstrate that 2D ATR IR spectroscopy offers the possibility to obtain ultrafast dynamics from sub-monolayer coverages of even low-absorbing vibrational probes such as nitrile functional groups.

show abstract

Section: Resultscontrasting

confidence: 45%

Section: Sample Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…18,19 . ATR spectroscopy is based on the reflecting properties of interfaces between materials of different refractive indices when certain experimental conditions are fulfilled.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Surface-enhanced, multi-dimensional attenuated total reflectance spectroscopy

2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…By adding infrared pump pulses, a spectrum analogous to a 2D IR spectrum is generated, but with different selection rules. In a separate approach, Hamm and coworkers modified a 2D IR spectrometer to work in an attenuated total reflection geometry (16). They deposited a monolayer onto the attenuated total reflection cell and used an azide reporter group.…”

Section: Methods and Applications Of 2d Ir With Monolayer Sensitivitymentioning

confidence: 99%

Two-dimensional infrared spectroscopy measures the structural dynamics of a self-assembled film only one molecule thick

Zanni

2016

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Since its first demonstration, many comparisons have been made between 2D infrared (2D IR) and NMR spectroscopy (1, 2). Both techniques use a series of pulses to manipulate and measure free induction decays that resolve couplings and dynamics through their characteristic multidimensional plots. The timescales are very different, with 2D IR spectroscopy using femtosecond pulses to measure the picosecond coherence times of vibrational modes, whereas NMR spectroscopy uses microsecond or millisecond pulses to measure nuclear spins that can last seconds. Thus, the two spectroscopies provide vastly different perspectives on structural dynamics. The article by Yan et al. (3), published in PNAS, uses the fast time resolution of 2D IR spectroscopy to study the structural dynamics of a functionalized self-assembled monolayer, providing insights into structural motions that are intimately related to chemistry. However, their experiments are also demonstrating an aspect of the technique that is only now being recognized as exceptional: the sensitivity of the technique to incredibly small amounts of material.NMR spectroscopy is often said to be insensitive (4). Although the level of sensitivity depends on many factors, such as the type of nuclei being measured and the magnetic field strength of the spectrometer, the statement itself refers to the differences in population between the nuclear spin states that create the free induction decays, given by the Boltzman distribution. At room temperature, the energy difference between nuclear spin states is much smaller than kT, resulting in nearly equal populations of states. The difference in population between two 1 H proton states in an 11.7-Tesla magnetic field is about 1 in 10 5 (4). In comparison, the energy difference between the υ = 0 and υ = 1 vibrational states is about eight-times larger than kT, resulting in an enormous difference in population between the states. In other words, vibrational states have almost the entire population in the ground state.Signal strength, and hence the sensitivity, are related to population differences because free induction decays are generated by unequal numbers of transitions between eigenstates (5). An ensemble of molecules with statistically equally populated eigenstates will produce no signal because there are as many absorption as emission transitions. (In fact, a commonly used trick in NMR is to purposely equilibrate eigenstates to eliminate unwanted signals.) Thus, the ultimate sensitivity of 2D IR spectroscopy is inherently much higher than NMR spectroscopy, because nearly all of the molecules in the ensemble are available for excitation. Dynamics of a Self-Assembled Film only One Molecule ThickIn their article, Yan et al. (3) demonstrate and use the sensitivity of 2D IR spectroscopy to measure a monolayer of molecules on a surface. The authors tethered a rhenium carbonyl vibrational probe to a monolayer of undecanethiol alkyl chains. Vibrational modes are sensitive to hydrogen bonding and electrostatics, and so the frequencies of...

show abstract

Ultrafast structural molecular dynamics investigated with 2D infrared spectroscopy methods

Kraack

2017

Top Curr Chem (Z)

View full text Add to dashboard Cite

Ultrafast, multi-dimensional infrared (IR) spectroscopy has been advanced in recent years to a versatile analytical tool with a broad range of applications to elucidate molecular structure on ultrafast timescales, and it can be used for samples in a many different environments. Following a short and general introduction on the benefits of 2D IR spectroscopy, the first part of this chapter contains a brief discussion on basic descriptions and conceptual considerations of 2D IR spectroscopy. Outstanding classical applications of 2D IR are used afterwards to highlight the strengths and basic applicability of the method. This includes the identification of vibrational coupling in molecules, characterization of spectral diffusion dynamics, chemical exchange of chemical bond formation and breaking, as well as dynamics of intra- and intermolecular energy transfer for molecules in bulk solution and thin films. In the second part, several important, recently developed variants and new applications of 2D IR spectroscopy are introduced. These methods focus on (i) applications to molecules under two- and three-dimensional confinement, (ii) the combination of 2D IR with electrochemistry, (iii) ultrafast 2D IR in conjunction with diffraction-limited microscopy, (iv) several variants of non-equilibrium 2D IR spectroscopy such as transient 2D IR and 3D IR, and (v) extensions of the pump and probe spectral regions for multi-dimensional vibrational spectroscopy towards mixed vibrational-electronic spectroscopies. In light of these examples, the important open scientific and conceptual questions with regard to intra- and intermolecular dynamics are highlighted. Such 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.

show abstract

2D attenuated total reflectance infrared spectroscopy reveals ultrafast vibrational dynamics of organic monolayers at metal-liquid interfaces

Cited by 31 publications

References 70 publications

Surface-enhanced, multi-dimensional attenuated total reflectance spectroscopy

Surface-enhanced, multi-dimensional attenuated total reflectance spectroscopy

Two-dimensional infrared spectroscopy measures the structural dynamics of a self-assembled film only one molecule thick

Ultrafast structural molecular dynamics investigated with 2D infrared spectroscopy methods

Contact Info

Product

Resources

About