Anharmonicity-driven redshift and broadening of sharp terahertz features of α-glycine single crystal from 20 K to 300 K: Theory and experiment

 Allen, J. L., T. J. Sanders, Josip Horvat, and R. A. Lewis. "Anharmonicity-driven redshift and broadening of sharp terahertz features of α-glycine single crystal from 20 K to 300 K: Theory and experiment." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 244 (2020): 118635.

Abstract

For the first time, large single crystals of the simplest amino acid, glycine, have been used to determine the temperature dependence of its terahertz spectrum. High-quality spectra with very sharp absorption features are observed at cryogenic temperatures. The α-glycine structure and the purity of the crystals were verified via Raman spectroscopy and X-ray diffraction. Spectral redshift with increasing temperature was observed for all absorption bands in the terahertz region (10–250 cm−1, or 1–8 THz) over the temperature range of 20–300 K. X-ray diffraction revealed expansion in all planes of the crystal lattice over the same temperature range. A Bose-Einstein distribution was used to model the frequency position shift of the two lowest-energy fundamental modes at 50 cm−1 and 69 cm−1. On this basis, we attribute the observed redshift and broadening with increasing temperature to the anharmonic potential associated with the phonon bath.

Terahertz, Infrared, and UV-Vis Spectroscopy Study on Silver@ Polyaniline Core@ Shell Nanocomposites; Optical and Electronic Properties

 Abouelsayed, A., Anis, B., & Eisa, W. H. (2020). Terahertz, Infrared, and UV–Vis Spectroscopy Study on Silver@ Polyaniline Core@ Shell Nanocomposites: Optical and Electronic Properties. The Journal of Physical Chemistry C, 124(33), 18243-18256.

Abstract

We present transmission measurements on silver@polyaniline (Ag@PANI) core@shell nanocomposites over a wide frequency range from terahertz to ultraviolet (0.001–6.2 eV). The Ag@PANI core@shell nanocomposites were prepared using solid-state reaction by mixing aniline sulfate (ANS) with 2.5, 5, 7.5, and 10 wt % AgNO3. The nanocomposites were characterized by transmission electron microscope, ultraviolet/visible spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The optical conductivity σ(ω) was fitted using the localization-modified Drude model together with the Lorentzian function. The incremental loading of AgNO3 leads to an increase in the Drude conductivity (σLMD) and decrease of the scattering rate (γD) due to the increase of electron delocalization of protonated quinoid imine units. In addition, the densities of states NEF at the Fermi level are increased from 1.7 to 2.7 per eV per formula unit, while the conduction bandwidth W is decreased from 0.7 to 0.4 eV with increasing the AgNO3 from 2.5 to 10%. The optically determined band parameters suggest that the addition of AgNO3 modifies the energy state of the Ag@PANI core@shell nanocomposites close to the Fermi energy modifying the half-filled polaron band.

… instrument). Terahertz time domain spectroscopy was used to characterize the Ag@PANI core@shell nanocomposites in the low-frequency range (2-100 cm−1) using a commercial THz- TDS system (TPS spectra 3000 system …

for full paper https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.0c05895

Pulsed THz imaging for thickness characterization of plastic sheets

 Zhai, Min, Alexandre Locquet, and D. S. Citrin. "Pulsed THz imaging for thickness characterization of plastic sheets." NDT & E International 116 (2020): 102338.

Abstract

The thickness of 2, 4, 6, 8, 10, and 12 mm thick polycarbonate (PC) and poly-methyl methacrylate (PMMA) sheets were characterized nondestructively by terahertz time-of-flight tomography in reflection. Due to terahertz attenuation and dispersion in the material, first characterized in transmission, features in the reflected signal associated with structure deep in the sample (i.e., the back interface) may be difficult to identify, and therefore signal processing is employed, namely frequency-wavelet domain deconvolution and a cross-correlation approach in which we account for dispersion. The refractive indices are found to be 

$n\left(\nu \right)=1.67-0.0096v$

for PC and 

$n\left(\nu \right)=1.61-0.0085v$

for PMMA, while the absorption coefficients, which follow the form of the universal dielectric response, are 

$\alpha \left(\nu \right)=0.564+9.075v^{1.669}$

 for PC and 

$\alpha \left(\nu \right)=0.0406+13.66v^{1.776}$

 for PMMA, where ν is measured in THz and the absorption coefficient is in units of cm−1. We show that straightforward analysis techniques that neglect dispersion are limited to measuring layer thicknesses in these materials of less than ~17 mm, while accounting for dispersion results in a factor-of-two improvement, allowing us to measure samples as thick as ~36 mm.

for full paper  and the missing lines see 

https://www.sciencedirect.com/science/article/abs/pii/S0963869519305079

… Tensile strength, ISO 527-2, 60 MPa, 65 MPa. Elongation at break, ISO 527-2, 6%, 4%. THz reflection and transmission spectra were measured with a Teraview TPS Spectra 3000, a broadband THz time-domain system, shown schematically in Fig …

Hydration Shells of DPPC Liposomes from the Point of View of Terahertz Time-Domain Spectroscopy

 Penkov, Nikita V., Valery A. Yashin, and Konstantin N. Belosludtsev. "Hydration Shells of DPPC Liposomes from the Point of View of Terahertz Time-Domain Spectroscopy." Applied Spectroscopy (2020): 0003702820949285.

Abstract

Analysis of structural and dynamic properties of water in suspensions of liposomes composed from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in three phase states (gel, rippled gel, liquid crystalline phase) by means of terahertz time-domain spectroscopy in 0.3–3.3 THz range was conducted in the current work. Fraction of free water molecules in DPPC liposome suspension was shown to decrease with temperature (compared to the analogous aqueous solution without liposomes), and intermolecular water binding was enhanced. The most crucial changes occur during gel-rippled gel phase transition (pretransition): at temperatures below pretransition point, liposomes alleviate water binding degree, while at temperatures above the transition point, they enhance water binding. This study has demonstrated the high information content of the terahertz time-domain spectroscopy method for exploring the hydration properties of phospholipids in water.

… spectra and refractive index spectra of the substance under investigation were measured at the same time with the help of a TPS Spectra 3000 spectrometer (Teraview, UK) in the range of wavenumber 10–110 cm –1 with the … 

Effect of particle size and deformation behaviour on water ingress into tablets

Skelbæk-Pedersen, Anne Linnet, Mohammed Al-Sharabi, Thomas Kvistgaard Vilhelmsen, Jukka Rantanen, and J. Axel Zeitler. "Effect of particle size and deformation behaviour on water ingress into tablets." International Journal of Pharmaceutics 587 (2020): 119645.

Abstract

Drug release performance of tablets is often highly dependent on disintegration, and water ingress is typically the rate-limiting step of the disintegration process. Water ingress into tablets is known to be highly influenced by the microstructure of the tablet, particularly tablet porosity. Initial particle size distribution of the formulation and the predominant powder deformation behaviour during compression are expected to impact such microstructure, making both factors important to investigate in relation to water ingress into tablets. Two size fractions (<125 and 355–500 µm) of plastically deforming microcrystalline cellulose (MCC) and fragmenting di-calcium phosphate (DCP) were compressed into tablets with porosities ranging from 5 to 30% (with 5% increments). The total porosity of the tablets was measured using terahertz time-domain spectroscopy and liquid transport into these tablets was quantified using a flow cell coupled to terahertz pulsed imaging. It was found that tablets compressed from large MCC particles resulted in slower water ingress compared to tablets prepared from small MCC particles. In contrast, no difference in liquid transport kinetics was observed for tablets prepared across both size fractions of DCP particles. These results highlight the complex interplay between material characteristics, the process induced microstructure, and the liquid transport process that ultimately determines the drug release performance of the tablets.

… Terahertz time-domain spectroscopy (THz-TDS) measurements were acquired in a transmission setup using a Terapulse 4000 spectrometer (Teraview Ltd., Cambridge, UK) (n = 3). The chamber was purged with dry nitrogen gas …

For full paper see https://www.sciencedirect.com/science/article/abs/pii/S0378517320306293

Terahertz imaging aids in art restoration

 

TeraView is pleased to announce that it has begun a collaboration with the Russian Museum’s Technology Research Department in St Petersburg, Russia aimed at demonstrating the power and capabilities of terahertz imaging in art restoration. TeraView is the leading supplier of terahertz systems to support a range of applications. Recently, the use of terahertz imaging in art restoration has been demonstrated by different museums and other institutions across the world. In some paintings and other works of art, terahertz imaging is able to detect the sequence and thickness of the different layers of paint, each of which can be imaged separately, effectively producing a 3D image of the artwork. Terahertz imaging can thus help reveal the artist’s technique, as well as authenticate paintings in some instances where the identity of the artist is in question. Additionally, terahertz imaging can assist art conservation and restoration decisions by providing information on cracks, delamination and defects buried below the surface and not visible to the naked eye or readily accessible with other techniques. The full press release is available to view here.

Terahertz Coating thickness analysis

Designed for the coatings industry, the TeraCota sensor can determine the individual thickness of multiple paint layers on both metallic and non-metallic substrates and offers significant benefits over existing techniques.

The sensor is non-contact, suitable for working on curved surfaces and capable of performing horizontal and vertical line scans.

For more information on the TeraCota system visit TeraView's web site at www.teraview.com #terahertz