Thin film infrared spectroscopy on planar silver halide: a new technology for water and other liquids in the mesoscopic domain

Kosower, Edward M.; Borz, Galina

doi:10.1039/c1ra00443c

Cited by 7 publications

(29 citation statements)

References 38 publications

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“…Using thin film infrared spectroscopy (TFIS), the first stage was the discovery of peaks for six water oligomers using a resolution of 4 cm À1 and naming the peaks ''marker peaks''. 10,11 The second stage was the realization that these peaks derived their intensity from the resonance among a set of identical oligomers excited by low energy phonons as calculated for cyclic pentamers in the gas phase. 12 The third stage was the switch from the ''regular'' resolution (4 cm À1 ) to a higher resolution (0.5 or 1 cm À1 ) producing a dramatic spectra of the water oligomers.…”

Section: Resultsmentioning

confidence: 99%

Low polarity water, a novel transition species at the polyethylene–water interface

Kosower

Borz

2015

Phys. Chem. Chem. Phys.

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The bridge between water repelling and water-attracting regions is recognized here as low polarity water, a novel "neutral" form of water; its identity as a dipole-dipole water dimer is supported by spectroscopic evidence of its presence in thin films of water on a polyethylene surface. High resolution (0.5 cm(-1)), low signal energies (Sg 100) and short scans (0.1 s) are used to ensure that all peaks are detected. Thin films may be trapped between two polyethylene windows, affirming the low polarity of such water; the spectra of the trapped films ("sandwich") are similar to those from a subtraction procedure. Use of the "sandwich" is a new and useful technique in surface studies. In general, intermediate forms might bridge incompatibility between different regimes, from sets of molecules (chemistry and physics) to sets of organisms (biology and sociology). Thin films of water on polyethylene also display strong and transient peaks of water oligomers, cyclic pentamers and cyclic hexamers (chair and boat), bicyclic hexamers (books 1 and 2) and tricyclic hexamers (prism) that have been previously identified in thin films of water on a silver halide surface.

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Section: Resultsmentioning

confidence: 99%

Low polarity water, a novel transition species at the polyethylene–water interface

Kosower

Borz

2015

Phys. Chem. Chem. Phys.

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“…[ [1][2][3][4] N-Methylpivalamide (4 mg, 98 %, Sigma-Aldrich) was placed in a test tube (10 mL) and pentane (60 mL, HPLC grade, 98 %, SigmaAldrich) was added. A perforated polypropylene cap with drying agent (granular silica gel, Sigma-Aldrich) was used to close the tube.…”

Section: Methodsmentioning

confidence: 99%

“…It is important to note that the quality of the spectra arises from the immobilization of polar molecules on polar surfaces, such as the AgX element used for the attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic measurements. [2][3][4] …”

Section: Introductionmentioning

confidence: 98%

N‐Methyl‐trimethylacetamide in Thin Films Displays Infrared Spectra of π‐Helices, with Visible Static and Dynamic Growth Phases, and then a β‐Sheet

et al. 2014

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The simplest (minimal) peptide model is HCONHCH3. An increase in the π-helix content with increased substitution in the acyl portion suggested the examination of N-methyl-trimethylacetamide) (NMT). NMT displays spectra, in which there is evolution of a set of helices defined by their amide I maxima near 1686 (3(10)), 1655 (first π), and, most importantly, at 1637 cm(-1) (π). Expanded thin-film infrared spectroscopy (XTFIS) shows pauses or slow stages, which are identified as static phases followed by dynamic phases with the incremental gain or loss of a helix turn. In addition, absorbance at 1637 cm(-1) suddenly increases at 82.1 s (30% over 0.3 s), indicating a phase change and crystallization of the π-helix, along with a coincidental decrease in the absorbance for the first π-helix. A sharp peak occurs at the maximum of the phase change at 82.5 s, representing a pure NMT π-helix. The spectra then undergo a decreasing general absorption loss over 150 s, with the π-helix evolving further to an antiparallel β-sheet fragment. The spectral quality arises from the immobilization of polar molecules on polar surfaces. The crystal structure is that of an antiparallel β-sheet.

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“…[6] TFIS has been used to make a spectroscopic identification of the oligomers of water [cyclic trimer, cyclic pentamer, cyclic hexamers (boat and chair), and bicyclic hexamers]. [7,8] TFIS utilizes a short acquisition time (revealing transient structures), limited IR energy (low signal, Sg, avoiding disruption of transient species), [5,6] and multiple reflections on planar AgX as the substrate for Fourier transform IR spectroscopy-attenuated total internal reflectance (FTIR-ATR), with limited penetration depth and molecular motion restricted by electrostatic immobilization. [8] .…”

Section: Introductionmentioning

confidence: 99%

“…The TFIS of small molecule films on planar silver bromide–silver chloride (AgX)2 in a special cell3 has exploited the surprising surface enhancement of IR on planar AgX, with studies of the oligomerization of ethanol,4 acetonitrile,5 and the peptide model of NMF 6. TFIS has been used to make a spectroscopic identification of the oligomers of water [cyclic trimer, cyclic pentamer, cyclic hexamers (boat and chair), and bicyclic hexamers] 7. 8…”

Section: Introductionmentioning

confidence: 99%

N‐Alkylacylamides in Thin Films Display Infrared Spectra of 3₁₀‐, α‐, and π‐Helices with Visible Static and Dynamic Growth Phases

Kosower

Borz

2014

ChemPhysChem

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A peptide model is a physical system containing a CONH group, the simplest being HCONHCH3 , N-methylformamide (NMF). We have discovered that NMF and N-methylacetamide (NMA), which form hydrogen-bonded oligomers in thin films on a planar AgX fiber, display infrared (IR) spectra with peaks like those of polypeptide helices. Structures can be assigned by their amide I maxima near 1672 (3(10)), 1655 (3(10)), 1653 (α), 1655 (π), and 1635 cm(-1) (π), which are the first IR data for the π-helix. Sharp peaks are an outcome of immobilization of polar species on the polar surface of silver halides. We report the first use of expanded thin-film IR spectroscopy, in which plots of every spectrum over the amide I-II range show pauses or slow stages in the increase or decrease of absorption. These are identified as static phases followed by dynamic phases, with the incremental gain or loss of a helix turn. A general theory can be stated for such processes. Density functional calculations show that the NMA α-helix pentamer (crystal structure geometry) is transformed into a π-helix-like form. For the first time, an entire sequence (3(10)-helix, α-helix, π-helix, quasiplanar species) of spectra has been recorded for NMA.

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Thin film infrared spectroscopy on planar silver halide: a new technology for water and other liquids in the mesoscopic domain

Cited by 7 publications

References 38 publications

Low polarity water, a novel transition species at the polyethylene–water interface

Low polarity water, a novel transition species at the polyethylene–water interface

N‐Methyl‐trimethylacetamide in Thin Films Displays Infrared Spectra of π‐Helices, with Visible Static and Dynamic Growth Phases, and then a β‐Sheet

N‐Alkylacylamides in Thin Films Display Infrared Spectra of 3₁₀‐, α‐, and π‐Helices with Visible Static and Dynamic Growth Phases

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Thin film infrared spectroscopy on planar silver halide: a new technology for water and other liquids in the mesoscopic domain

Cited by 7 publications

References 38 publications

Low polarity water, a novel transition species at the polyethylene–water interface

Low polarity water, a novel transition species at the polyethylene–water interface

N‐Methyl‐trimethylacetamide in Thin Films Displays Infrared Spectra of π‐Helices, with Visible Static and Dynamic Growth Phases, and then a β‐Sheet

N‐Alkylacylamides in Thin Films Display Infrared Spectra of 310‐, α‐, and π‐Helices with Visible Static and Dynamic Growth Phases

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N‐Alkylacylamides in Thin Films Display Infrared Spectra of 3₁₀‐, α‐, and π‐Helices with Visible Static and Dynamic Growth Phases