Study of Disordered Materials by Terahertz Spectroscopy

Šibík, Juraj; Zeitler, J. Axel

doi:10.1002/9783527652693.ch13

Cited by 3 publications

(4 citation statements)

References 133 publications

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“…The dielectric losses of the samples in the glassy state at the lowest temperatures are almost independent of temperature and comprise a microscopic peak at a frequency around 2–3 THz, as seen in Figure and far-infrared spectra . The peak is still evident for T > T g , but the amplitude now increases with increasing temperature.…”

mentioning

confidence: 89%

Thermal Decoupling of Molecular-Relaxation Processes from the Vibrational Density of States at Terahertz Frequencies in Supercooled Hydrogen-Bonded Liquids

Šibík

Elliott

Zeitler

2014

J. Phys. Chem. Lett.

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109

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At terahertz frequencies, the libration-vibration motions couple to the dielectric relaxations in disordered hydrogen-bonded solids. The interplay between these processes is still poorly understood, in particular at temperatures below the glass transition temperature, Tg, yet this behavior is of vital importance for the molecular mobility of such materials to remain in the amorphous phase. A series of polyhydric alcohols were studied at temperatures between 80 and 310 K in the frequency range of 0.2-3 THz using terahertz time-domain spectroscopy. Three universal features were observed in the dielectric losses, ϵ″(ν): (a) At temperatures well below the glass transition, ϵ″(ν) comprises a temperature-independent microscopic peak, which persists into the liquid phase and which is identified as being due to librational/torsional modes. For 0.65 Tg < T < Tg, additional thermally dependent contributions are observed, and we found strong evidence for its relation to the Johari-Goldstein secondary β-relaxation process. (b) Clear spectroscopic evidence is found for a secondary β glass transition at 0.65 Tg, which is not related to the fragility of the glasses. (c) At temperatures above Tg, the losses become dominated by primary α-relaxation processes. Our results show that the thermal changes in the losses seem to be underpinned by a universal change in the hydrogen bonding structure of the samples.

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confidence: 89%

Thermal Decoupling of Molecular-Relaxation Processes from the Vibrational Density of States at Terahertz Frequencies in Supercooled Hydrogen-Bonded Liquids

Šibík

Elliott

Zeitler

2014

J. Phys. Chem. Lett.

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109

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“…The mechanism of interaction between THz radiation and molecules is experimentally linked to the mean squared molecular displacement commonly measured by inelastic neutron scattering (INS), 15−17 and hence, THz-TDS is capable of providing similar insight into the protein dynamics 18−21 and may offer a more accessible benchtop alternative measurement technology to INS. 22 Recently, it was shown that smaller and molecularly more flexible carbohydrates stabilize proteins better than larger and more rigid carbohydrates do, provided they maintain sufficient vitrification. 23 This was explained in terms of the fact that the smaller and more flexible carbohydrates are less affected by steric hindrance and therefore better suited to form hydrogen bonds with the protein.…”

Section: Characterization Of Protein−carbohydrate Interactions Andmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…We were previously able to show that terahertz spectroscopy is sensitive to both primary and secondary relaxations, , with the former reflecting global mobility and the latter local molecular mobility far below T g . The mechanism of interaction between THz radiation and molecules is experimentally linked to the mean squared molecular displacement commonly measured by inelastic neutron scattering (INS), − and hence, THz-TDS is capable of providing similar insight into the protein dynamics − and may offer a more accessible benchtop alternative measurement technology to INS …”

Section: Introductionmentioning

confidence: 99%

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Thermal Gradient Mid- and Far-Infrared Spectroscopy as Tools for Characterization of Protein Carbohydrate Lyophilizates

et al. 2017

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Protein drugs play an important role in modern day medicine. Typically, these proteins are formulated as liquids requiring cold chain processing. To circumvent the cold chain and achieve better storage stability, these proteins can be dried in the presence of carbohydrates. We demonstrate that thermal gradient mid- and far-infrared spectroscopy (FTIR and THz-TDS, respectively) can provide useful information about solid-state protein carbohydrate formulations regarding mobility and intermolecular interactions. A model protein (BSA) was lyophilized in the presence of three carbohydrates with different size and protein stabilizing capacity. A gradual increase in mobility was observed with increasing temperature in formulations containing protein and/or larger carbohydrates (oligo- or polysaccharides), lacking a clear onset of fast mobility as was observed for smaller molecules. Furthermore, both techniques are able to identify the glass transition temperatures (Tg) of the samples. FTIR provides additional information as it can independently monitor changes in protein and carbohydrate bands at the Tg. Lastly, THz-TDS confirms previous findings that protein–carbohydrate interactions decrease with increasing molecular weight of the carbohydrate, which results in decreased protein stabilization.

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2018

Impedance Spectroscopy

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Study of Disordered Materials by Terahertz Spectroscopy

Cited by 3 publications

References 133 publications

Thermal Decoupling of Molecular-Relaxation Processes from the Vibrational Density of States at Terahertz Frequencies in Supercooled Hydrogen-Bonded Liquids

Thermal Decoupling of Molecular-Relaxation Processes from the Vibrational Density of States at Terahertz Frequencies in Supercooled Hydrogen-Bonded Liquids

Thermal Gradient Mid- and Far-Infrared Spectroscopy as Tools for Characterization of Protein Carbohydrate Lyophilizates

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