Short-Wave near Infrared Spectra of Organic Liquids

Bonanno, Anthony; Griffiths, Peter R.

doi:10.1255/jnirs.2

Cited by 22 publications

(7 citation statements)

References 29 publications

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“…20 The Ðrst overtones of the OH stretching bands due to the free (D7100 cm~1) and associated (6200È6900 cm~1) species are heavily overlapped by the CH combination bands [2l(CH) ] d(CH)] at 7183 and 6980 cm~1 [ Fig. 26 The corresponding overtones of the associated species are too weak to be observed. 24,25 As expected, the intensity of the monomer band increases, whereas that of the polymer band (D6200 cm~1) decreases with increase in temperature.…”

Section: Resultsmentioning

confidence: 99%

The temperature-induced changes in hydrogen bonding of decan-1-ol in the pure liquid phase studied by two-dimensional Fourier transform near-infrared correlation spectroscopy

Czarnecki¹,

Ozaki²

1999

Phys. Chem. Chem. Phys.

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Fourier transform near-infrared (FT-NIR) spectra of decan-1-ol in the pure liquid phase were investigated in the regions of the Ðrst and second overtones of the OH stretching vibration over the temperature range 15È76 ¡C. The dynamics of temperature-induced changes in the hydrogen bonding were explored by the 2D correlation approach. It was found that the Ðrst overtone of the monomer band is split into two peaks (7087 and 7114 cm~1). The peaks originate from the rotational isomerism of the OH group. Although the trans-isomer (at 7114 cm~1) is more stable than the gauche-isomer (at 7087 cm~1), the intensity of the band due to the former is weaker in the pure liquid phase. In dilute solutions the situation is reversed. This e †ect can be explained by higher accessibility of the OH proton in the trans-position. Therefore, the population of the free protons in the trans-position is reduced faster with increase in concentration. The band attributed to the free terminal OH groups in open chain polymers was not observed in the 2D correlation spectra of neat decan-1-ol. As for butanols, studied previously, the populations of the polymers and cyclic dimers vary faster than that of the monomers. When the temperature is raised, the population of the monomers increases faster where that of the polymers decreases more slowly. Hence it is concluded that the growth in the population of the monomeric species comes from dissociation of the intermediate species. These 2D correlation studies on alcohols in the pure liquid state suggest that the degree of association in the saturated straight-chain alcohols decreases with increase in chain length.

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Section: Resultsmentioning

confidence: 99%

The temperature-induced changes in hydrogen bonding of decan-1-ol in the pure liquid phase studied by two-dimensional Fourier transform near-infrared correlation spectroscopy

Czarnecki¹,

Ozaki²

1999

Phys. Chem. Chem. Phys.

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“…10 The second overtone of the monomer band at 10 383 cm 2 1 is surrounded by the third overtone of the CH stretching vibrations (4n(CH)) at 10 757 cm 2 1 and the CH combination bands (3n(CH)1d(CH)) near 9630 cm 2 1 . 5,11 As can be seen, the intensity of the second overtone of the m onomer band strongly increases with an increase in temperature, whereas the third overtone of the CH band does not vary in its intensity. A slight enhancement in intensity of the CH combination bands, not yet as strong as that for the monomer band, suggests that these spectral features are overlapped by another one, associated with the OH stretching vibrations.…”

Section: Experimental and Data Treatm Entmentioning

confidence: 87%

Two-Dimensional Correlation Analysis of the Second Overtone of the v(OH) Mode of Octan-1-ol in the Pure Liquid Phase

Czarnecki

2000

Appl Spectrosc

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The temperature-induced variations in Fourier transform near-infrared (FT-NIR) spectra of pure liquid octan-1-ol were studied by two-dimensional correlation analysis. For the rst time, the second overtone of the OH stretch ing band (3n (OH)) due to the dimeric species and the splitting of the second overtone of the monomer band arising from the presence of two OH conformers have been observed. Fourier self-deconvoluted (FSD) and second-derivative spectra also con rmed the splitting of the monomer band into two components. It has been demonstrated that positions of the peaks appearing in the two-dimensional contour maps correlating the rst-and seco nd-overtone regions can be applied for determination of anharmonicity constants. The results presented in this paper suggest that the rule saying that the less associated species have the stronger overtones holds on going from the rst to the second overtones as well.

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“…5 to previously reported loss spectra of methanol in Te¯ont-AF-based LCOFs, 36 it can be seen that the 2835 cm 2 1 (1010 nm) and 2942 cm 2 1 (1021 nm) Raman C±H stretching peaks which are least enhanced in the LCOF coincide with the peak of an``intense' ' loss feature that can most likely be assigned as a C±H overtone combination band. 51 Similarly the 1450 cm 2 1 (866 nm) Raman CH 3 bend peak is located at the edge of a weaker absorption feature that can probably be assigned as a third-overtone C±H stretching band. 51 The 1033 cm 2 1 (854 nm) Raman CCO stretch peak that experiences greatest enhancement in the LCOF overlaps with the signi® cantly weaker tail of the same third-overtone C±H band.…”

Section: Resultsmentioning

confidence: 96%

“…51 Similarly the 1450 cm 2 1 (866 nm) Raman CH 3 bend peak is located at the edge of a weaker absorption feature that can probably be assigned as a third-overtone C±H stretching band. 51 The 1033 cm 2 1 (854 nm) Raman CCO stretch peak that experiences greatest enhancement in the LCOF overlaps with the signi® cantly weaker tail of the same third-overtone C±H band. By analogy with these results it can be assumed that the broad, intense second-overtone OH absorption band centered near 977 nm in water 52 (Raman shift of approximately 2500 cm 2 1 with 785 nm excitation) will m ore effectively attenuate Raman light in aqueous solutions and potentially render LCOFs less bene® cial in this region.…”

Section: Resultsmentioning

confidence: 96%

Raman Performance Characteristics of Teflon®-AF 2400 Liquid-Core Optical-Fiber Sample Cells

1999

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Several properties of Teflon®-AF liquid-core optical-fiber (LCOF) sample cells relevant to their utility in analytical Raman spectroscopy have been investigated. These include the nature and extent of cladding-related background and its effect on signal-to-noise ratio, and the dependence of intensity enhancement on LCOF length, core diameter, excitation wavelength, and scattering wavelength. Significant improvements in signal-to-noise ratio relative to conventional sampling techniques were demonstrated in LCOFs filled with dilute (6 × 10−2 M and 6 × 10−4 M) aqueous solutions of phenylalanine. A maximum intensity enhancement factor of approximately 120 was measured by using 50 μm i.d. LCOFs filled with methanol and 532 nm excitation. Enhancement in 785 nm-excited spectra was found to vary with Raman shift in a manner consistent with self-absorption by high-overtone vibrational bands in the core liquid.

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Short-Wave near Infrared Spectra of Organic Liquids

Cited by 22 publications

References 29 publications

The temperature-induced changes in hydrogen bonding of decan-1-ol in the pure liquid phase studied by two-dimensional Fourier transform near-infrared correlation spectroscopy

The temperature-induced changes in hydrogen bonding of decan-1-ol in the pure liquid phase studied by two-dimensional Fourier transform near-infrared correlation spectroscopy

Two-Dimensional Correlation Analysis of the Second Overtone of the v(OH) Mode of Octan-1-ol in the Pure Liquid Phase

Raman Performance Characteristics of Teflon®-AF 2400 Liquid-Core Optical-Fiber Sample Cells

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