Terahertz Spectroscopy Applied For Investigation of Water Structure

Nikita Penkov, Nikolay Shvirst, Valery Alexandrovich Yashin, Eugeny Eugenievich Fesenko (Jr.), and Eugeny Eugenievich Fesenko

 Abstract

The absorption spectra of liquid water and different aqueous solutions were analyzed in a terahertz frequency domain (from 6 to 200 cm–1) which characterize the collective dynamics of water molecules. The particular attention was paid to the relaxation process in the range of ~6–80 cm-1. The physical essence of this process on the molecular level is still unclear. We found that the amplitude of this relaxation process correlates with the degree of destruction of water structure. The obtained data allowed us to interpret this process as a monomolecular relaxation of free water molecules. Based on a consideration of the water polarization in the electric field we proposed a method of calculation of the amount of free water molecules in solution.

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Calendering as a direct shaping tool for the continuous production of fixed-dose combination products via co-extrusion

A.-K. Vynckier, H. Lin, J.A. Zeitler, J.-F. Willart, E. Bongaers J. Voorspoels, J.P. Remon, C. Vervaet

European Journal of Pharmaceutics and Biopharmaceutics

Abstract

In this study calendering is used as a downstream technique to shape monolithic co-extruded fixed-dose combination products in a continuous way. Co-extrudates with a metoprolol tartrate-loaded sustained-release core and a hydrochlorothiazide-loaded immediate-release coat were produced and immediately shaped into a monolithic drug delivery system via calendering, using chilled rolls with tablet-shaped cavities. In vitro metoprolol tartrate release from the ethylcellulose core of the calendered tablets was prolonged in comparison with the sustained release of a multiparticulate dosage form, prepared manually by cutting co-extrudates into mini-matrices. Analysis of the dosage forms using X-ray micro-computed tomography only detected small differences between the pore structure of the core of the calendered tablet and the mini-matrices. Diffusion path length was shown to be the main mechanism behind the release kinetics. Terahertz pulsed imaging visualized that adhesion between the core and coat of the calendered tablet was not complete and a gradient in coat thickness (varying from 200 to 600 μm) was observed. Modulated differential scanning calorimetry and X-ray diffraction indicated that the solid-state properties of both drugs were not affected by the calendering procedure.

see http://www.sciencedirect.com/science/article/pii/S0939641115003264

... 2.2.6. Terahertz pulsed imaging (TPI). The calendered tablets from different formulations were
analyzed using a TPI imaga2000 coating scan system (TeraView, Cambridge,UK). ... Images wereanalyzed using TPI View (version 3.0.3, TeraView, Cambridge, UK). ...

Improved terahertz modulation using germanium telluride (GeTe) chalcogenide thin films

Abstract

We demonstrate improved terahertz (THz) modulation using thermally crystallized germaniumtelluride (GeTe) thin films. GeTe is a chalcogenide material that exhibits a nonvolatile, amorphous to crystalline phase change at approximately 200 °C, as well as six orders of magnitude decreased electrical resistivity. In this study, amorphous GeTe thin films weresputtered on sapphire substrates and then tested using THz time-domain spectroscopy (THz-TDS). The test samples, heated in-situ while collecting THz-TDS measurements, exhibited a gradual absorbance increase, an abrupt nonvolatile reduction at the transition temperature, followed by another gradual increase in absorbance. The transition temperature was verified by conducting similar thermal tests while monitoring electrical resistivity. THz transmittance modulation data were investigated between 10 and 110 cm⁻¹ (0.3–3.3 THz). A peak modulation of approximately 99% was achieved at 2.3 THz with a 100 nm GeTe film on a sapphiresubstrate. After isolating the sapphire and the crystalline GeTe (c-GeTe) absorbance contributions, the results showed THz modulations ranging from 88.5% to 91.5% that were attributed solely to the single layer of transitioned c-GeTe. These results strongly motivate using GeTe or other chalcogenide thin films in THz modulators, filters, and metamaterial applications.

http://scitation.aip.org/content/aip/journal/apl/107/3/10.1063/1.4927272

The measurments in this paper were collected with a TeraView THz-TDS spectroscopy system equipped with a variable temperature sample holder.

Teraview's TPS Spectra 3000 used to measure piezoelectric sensor adhesive bonding

http://iopscience.iop.org/1742-6596/628/1/012114/pdf/1742-6596_628_1_012114.pdf

Assessment of piezoelectric sensor adhesive bonding

Abstract

Piezoelectric transducers are widely utilized in Structural Health Monitoring (SHM). They are used both in guided wave-based and electromechanical impedance-based methods. Transducer debonding or unevenly distributed glue underneath the transducer reduce the performance and reliability of the SHM system. Therefore, quality assessment methods for glue layer need to be developed. In this paper, the authors present results obtained from two methods that allow the quality assessment of adhesive bonds of piezoelectric transducers. The electromechanical impedance method is utilized to analyze transducer adhesive bonding. An improperly prepared bonding layer is a source for changes in the electromechanical impedance characteristics in comparison to a perfectly bonded transducer. In the resistance characteristics of the properly bonded transducer the resonance peaks of the structure were clearly visible. In the case when adhesive layer is not equally distributed under sensor, the amplitudes of structural resonance peaks are reduced. In the case of completely detached transducer, the structural resonance peaks disappear and only resonance peaks of the transducer itself are visible. These peaks (peaks of free transducer hanging on wires) are significantly larger than the resonance peaks of the investigated structure in the considered frequency interval. The bonding layer shape is also analyzed using time-domain terahertz spectroscopy in reflection mode. This method allows to visualize the adhesive layer distribution based on C-scan analysis. C-scans of signals or envelope-detected signals can be used to estimate the area of proper adhesion between bonding agent and transducer and hence provides a more quantitative approach towards transducer inspection. 


Teraview's TPS Spectra 3000 was used the investigate the materials used in the paper.

SPIE Photonics West OPTO 2016 Conference - Call For Papers

SPIE Photonics West OPTO 2016 Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications IX conference

Abstracts are accepted now through 3 August 2015

For more information go to http://spie.org/PWO/conferencedetails/thz-rf-mm-submm-wave-technology

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