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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TeraView TPS 3000 unit for time domain spectroscopy was used to investigate spectral properties of nematic liquid crystal mixtures

Article

Spectral Properties of Nematic Liquid Crystal Mixtures Composed with Long and Short Molecules in THz Frequency Range

ABSTRACT In this paper the influence of short and long molecules added to liquid crystal
6CHBT were investigated. Change of refractive indices and absorption coefficients
for 6CHBT mixtures were compared in the 0.3 - 3 THz frequency range. Influence of
temperature on the mentioned parameters of liquid crystal were investigated. Our study
show that even a slight change in shape and the composition of the molecules dopants
affects the macroscopic properties of liquid crystal. These properties depend on the
length of chains, the number of benzene or cyclohexane rings or the spatial distribution
of molecules and the interactions between them in the liquid crystal mixture. Spectra
measurements on the terahertz time-domain spectrometer were performed.
Spectral Properties of Nematic Liquid Crystal Mixtures Composed with Long and Short Molecules in THz Frequency Range (PDF Download Available). Available from: http://www.researchgate.net/publication/235218799_Spectral_Properties_of_Nematic_Liquid_Crystal_Mixtures_Composed_with_Long_and_Short_Molecules_in_THz_Frequency_Range [accessed Jun 23, 2015].

IRMMW-THz 2013

Mainz on the Rhine, September 1st-6th

TeraView will be attending IRMMW-THz 2013.

The 38th Annual International Conference on Infrared, Millimeter, and Terahertz Waves will be held in Mainz, Germany, on September 1 - 6, 2013, at the Congress Center Mainz (Rheingoldhalle). The conference is organized by a Local Organizing Committee under the auspices of the IOC, and with technical co-sponsorship from the IEEE Microwave Theory and Techniques Society (MTT-S).

Dr. Phil Taday will be presenting a paper with title: 

Crystallization Of Sucrose Monitored By Terahertz Pulsed Spectroscopy
Session: Mo. 9 - THz Spectroscopy: Biomolecules
Abstract ID: Mo9-1
Date: 02/09/2013
Time: 2:00:00 PM

If you would like to pre-arrange a meeting, please e-mail Dr. Philip Taday. For more information and to attend the workshop please visit the event webpage.

To view all conferences that TeraView will be attending please visit our website

TeraView will also be exhibiting at this conference.

Impact of Pellet Thickness on Quantitative Terahertz Spectroscopy of Solid Samples in a Polyethylene Matrix

Anal. Chem., 2013, 85 (7), pp 3674–3681
DOI: 10.1021/ac302017d
Publication Date (Web): February 25, 2013
Copyright © 2013 +American Chemical Society

Authors: Hankyu Namkung †, Jaejin Kim †, Hoeil Chung *†, and Mark A. Arnold *‡
† Department of Chemistry and Research Institute for Natural Sciences, Hanyang University, Seoul, Korea 133-791
‡ Department of Chemistry and Optical Science and Technology Center, University of Iowa, Iowa City Iowa 52242, United States

Abstract

Pellets composed of different weight-percent (wt-%) of lactose within a polyethylene (PE) matrix are used to examine how the physical thickness of solid samples impact analytical measurements performed over terahertz (THz) frequencies when using time-domain THz spectroscopy. Results indicate that the thickness of each pellet depends on the mass and physical properties of the individual components that comprise the pellet. Thickness of mixture pellets depends on the porosity of the individual pellet components. Porosity measurements presented here for PE and lactose give values of 25.6 ± 0.3 and 14.5 ± 0.1, respectively, which indicate that more air is trapped within the compressed PE matrix compared to that for lactose. This difference in porosity creates different pellet thicknesses for pellets of the same nominal mass but with different relative amounts of PE and lactose. For this binary matrix, the thickness of each pellet is found to be a linear combination of the compressed densities of the individual components. Analysis of the time-domain THz spectra reveals that thinner samples are confounded by a fringe pattern observed in the frequency-domain spectra. This fringe pattern is created by an etalon corresponding to the air/pellet interfaces for the sample in the optical path. Spectra collected from thicker pellets are confounded by a sloping baseline caused by scattering effects within the pellet matrix. The quantitative impact of pellet thickness is determined by comparing the mean standard error of calibration (MSEC) and mean standard error of prediction (MSEP) for a set of leave-three-out cross validation multivariate calibration models based on the partial least-squares (PLS) algorithm. Results indicate that PLS models are capable of analytical measurements with MSEC and MSEP values between 0.04 and 0.20 wt-%. Analysis of spectral variance captured within the corresponding spectral loadings for each model indicates that spectral variance is lowest for the 300 mg samples where the impact of scattering is minimal under conditions when the sample etalon is nonexistent.

... Each time domain spectrum was collected with a TPI Spectra 1000 spectrometer (TeraView, Cambridge, UK) with a resolution setting of 1.2 cm-1. A detailed description of the instrumentation can ...