Surface-Induced Heterogeneity Analysis of an Alkanethiol Monolayer on Microcrystalline Copper Surface Using Sum Frequency Generation Imaging Microscopy

Fang, Ming; Baldelli, Steven

doi:10.1021/acs.jpcc.6b09403

Cited by 28 publications

(27 citation statements)

References 62 publications

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“…[4][5][6][7][8][9][10][11][12] We implemented this phase-stable collinear HD VSFG microscope to study a guest-host molecular self-assembly 42 spin-coated on gold. We found that the self-assembly contains non-centrosymmetric domains at sizes from about 20 to 100 μm 2 , and there are mainly two types of domains, which have opposite molecular alignment relative to each other. This microscope development should pave the way for implementing HD VSFG imaging in a broad range of applications in biophysics, 43 materials 44 and surface sciences.…”

mentioning

confidence: 89%

Self-Phase-Stabilized Heterodyne Vibrational Sum Frequency Generation Microscopy

2017

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Vibrational sum frequency generation (VSFG) spectroscopy has been a powerful technique to probe molecular structures at non-centrosymmetric media. Recent developed heterodyne (HD) detection can further reveal spectral phase and molecular orientations. Adding imaging capability to an HD VSFG signal can bring spatial visualization capability into this non-linear optical technique. However, it has been a challenge to build an HD VSFG microscope that is both easy to align and has good spectral phase stability -two necessary criterions for the broad application of this technique into various areas of science. Here, we report a fully-collinear HD VSFG microscope, which meets both phase stability and optical alignment requirements that can spatially resolve images of molecular interfaces and domains, with chemical and structural sensitivities. The phase stability is more than nine times better than a Michelson Interferometric HD VSFG microscope. Using this HD VSFG microscope, we study the structures of molecular selfassembly films. Because of the superior phase sensitivity, we successfully identify two molecular domains with different molecular orientations, which we show is not possible to extract from an ensemble-averaged VSFG spectrum or homodyne-detected VSFG image.

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mentioning

confidence: 89%

Self-Phase-Stabilized Heterodyne Vibrational Sum Frequency Generation Microscopy

2017

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“…46 The estimated tilt angles are within the reported values. [47][48][49][50][51][52][53][54] Overall, the tilt angles obtained for the CH 3 SS of the different concentration ratios are positioned closer to the surface normal.…”

Section: Orientation and Sensitivity Determination As A Function Of Smentioning

confidence: 70%

Orientational Analysis of Monolayers at Low Surface Concentrations Due to an Increased Signal-to-Noise Ratio (S/N) Using Broadband Sum Frequency Generation Vibrational Spectroscopy

et al. 2019

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Sum frequency generation (SFG) * Equal contributors. spectroscopy was used to deduce the orientation of the terminal methyl (CH3) group of self-assembled monolayers (SAMs) at the air–solid and air–liquid interfaces at surface concentrations as low as 1% protonated molecules in the presence of 99% deuterated molecules. The SFG spectra of octadecanethiol (ODT) and deuterated octadecanethiol (d37 ODT) SAMs on gold were used for analysis at the air–solid interface. However, the eicosanoic acid (EA) and deuterated EA (d39 EA) SAMs on the water were analyzed at the air–liquid interface. The tilt angle of the terminal CH3 group was estimated to be ∼39 ° for a SAM of 1% ODT : 99% d37 ODT, whereas the tilt angle of the terminal CH3 group of the 1% EA : 99% d39 EA monolayer was estimated to be ∼32 °. The reliability of the orientational analysis at low concentrations was validated by testing the sensitivity of the SFG spectroscopy. A signal-to-noise (S/N) ratio of ∼60 and ∼45 was obtained for the CH3 symmetric stretch (SS) of 1% ODT : 99% d37 ODT and 1% EA : 99% d39 EA, respectively. The estimated increase in S/N ratio values, as a measure of the sensitivity of the SFG spectroscopy, verified the capacity to acquire the SFG spectra at low concentrations of interfacial molecules under ambient conditions. Overall, the orientational analysis of CH3 SS vibrational mode was feasible at low concentrations of protonated molecules due to increased S/N ratio. In support, the improved S/N ratio on varying incident power density of the visible beam was also experimentally demonstrated.

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“…We chose VSFG to study mesoscopic ordering in this self-assembly material because, in order to be VSFG active, the SDS@2β-CD needs to maintain ordering and overall chirality. (20) VSFG is a nonlinear optical technique that is widely used for studying structures of non-centrosymmetric systems, (21)(22)(23)(24) such as interfaces (25)(26)(27)(28)(29) and many biological tissues. (8,(30)(31)(32) VSFG and its non-resonant counterpart, second harmonic generation, have recently been developed into microscopes by several groups, which demonstrates the importance of spatially-resolving heterogenous interfaces and non-centrosymmetric materials.…”

Section: Resultsmentioning

confidence: 99%

“…(8,(30)(31)(32) VSFG and its non-resonant counterpart, second harmonic generation, have recently been developed into microscopes by several groups, which demonstrates the importance of spatially-resolving heterogenous interfaces and non-centrosymmetric materials. (19,25,37,38,26,28,30,(32)(33)(34)(35)(36) Here, we report the first transient VSFG microscope, for which the experimental setup was developed based on our previous work (Fig. 1, see Methods and Supporting information S1.1 for details).…”

Section: Resultsmentioning

confidence: 99%

Mesoscopic Ordering of Water Dynamics in Self-Assembled Materials Revealed by Transient VSFG Microscopy

Wang¹,

Chen²,

Wagner³

et al. 2019

Preprint

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<b>We report, for the first time, observations of mesoscopically homogeneous but macroscopically heterogenous water dynamics in self-assembled materials by a new, spatially resolved infrared (IR) pump vibrational sum frequency generation (VSFG) probe microscope. Using this new technique, we spatially resolved dynamics of water bounded by host-guest, self-assembled sheets comprised of sodium dodecyl sulfate (SDS) and β-cyclodextrin (β-CD). We found that the strong hydrogen-bond interactions between β-CD and nearby water not only template nearby water networks to adopt the chirality of β-CD, but also allow resonant energy transfer from β-CD to nearby water. More interestingly, the resonant energy transfer dynamics are heterogeneous among domains, while remaining uniform within domains. This surprising result indicates that the water near self-assembled materials can be templated uniformly across micron domains. Because SDS@2β-CD is a synthetic analogue that parallels the morphology, rigidity and crystallinity of protein assemblies, similar mesoscopic ordering of water structure and dynamics could also exist in biological soft materials. The advancement of adding spatial resolution to ultrafast molecular vibrational spectroscopy opens a new way to probe mesoscopic molecular structure ordering and relaxation dynamics in biological systems, and hydro-responsive self-assembly materials for micro-optics and electronics. </b>

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Surface-Induced Heterogeneity Analysis of an Alkanethiol Monolayer on Microcrystalline Copper Surface Using Sum Frequency Generation Imaging Microscopy

Cited by 28 publications

References 62 publications

Self-Phase-Stabilized Heterodyne Vibrational Sum Frequency Generation Microscopy

Self-Phase-Stabilized Heterodyne Vibrational Sum Frequency Generation Microscopy

Orientational Analysis of Monolayers at Low Surface Concentrations Due to an Increased Signal-to-Noise Ratio (S/N) Using Broadband Sum Frequency Generation Vibrational Spectroscopy

Mesoscopic Ordering of Water Dynamics in Self-Assembled Materials Revealed by Transient VSFG Microscopy

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