New terahertz dielectric spectroscopy for the study of aqueous solutions

Abstract

We present a development of a high precision, tunable far-infrared (terahertz) frequency-domain dielectric spectrometer for studying the dynamics of biomolecules in aqueous solutions in the gigahertz-toterahertz frequency. As a first application we report on the measurement of the absorption and refractive index for liquid water in the frequency range from 5 GHz to 1.12 THz (0.17 to 37.36 cm -1 or 0.268 to 60 mm). The system provides a coherent radiation source with a power up to 20 mW in the gigahertz-toterahertz region. The power signal-to-noise ratio of our instrument reaches 10 15 and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with an error bars of ±0.02 o C from above 0 o C to 90 o C. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.

Recent progress in the science of complex coacervation

“…To date, the majority of approaches rely on indirect phenomenological measurements such as changes in the phase behavior of coacervates, 40,64,139 differences in the amount of water introduced into a sample by different ions, 53 or measurements of "non-freezing," surface-bound water. 89 Experimentally, new techniques such as terahertz dielectric spectroscopy have the potential to help directly access these structural changes, 149,150 and these questions look to be key to future materials design questionseven beyond coacervation.…”

New Insights into the Dynamics of Zwitterionic Micelles and Their Hydration Waters by Gigahertz-to-Terahertz Dielectric Spectroscopy

“…The setup is capable of simultaneously measuring intensity and phase over a large effective dynamical range of fifteen orders of magnitude. 32 Samples were kept in a home built variable path-length cell with submicron (~0.08 microns) precision in changing thickness. Temperature of the sample is controlled with the previously mentioned temperature controller.…”

Terahertz free‐space dielectric property measurements using time‐ and frequency‐domain setups

“…Some free‐space methods comprise a vector network analyzer (VNA) with pairs of vector network analyzer extenders (VNAXs) and standard gain horns (SGHs) . The measurement frequency of these methods can reach up to 1.1 THz, and they should be able to achieve higher frequencies when the corresponding VNAXs and SGHs are available in the future.…”

“…However, the complex relative permittivity is not expressed explicitly, and thus some necessary procedures need to be carried out to resolve the problem. For References , the calculations are carried out using iterative algorithms. The iterative calculations require considerable computational resources and computation time, which grow worse if approximate property values are not known.…”