Complementary optical and neutron vibrational spectroscopy study of bromanilic acid: 2,3,5,6-tetramethylpyrazine (1:1) cocrystal

Katarzyna Łuczyńska, , Kacper Drużbicki, Krzysztof Lyczko, Wojciech Starosta

Abstract

Complementary structural and vibrational spectroscopy study of bromanilic acid:2,3,5,6-tetramethylpyrazine (BrA:TMP) 1:1 cocrystal is reported. The crystallographic structure was determined by means of single-crystal X-ray diffraction and can be described as a stacked net of hydrogen-bonded TMPH⁺⋯BrA⁻⋯BrA⁻⋯TMPH⁺ moieties. The structural analysis was supported by ¹³CP/MAS NMR study. The complementary vibrational analysis was performed by combining optical (infrared, Raman, terahertz) and inelastic neutron scattering spectroscopy with the state-of-the-art solid–state density functional theory (DFT) computations, which have proven to be superior to the hybrid cluster modeling approach. An excellent agreement between theoretical and experimental data was observed over the entire spectral range, allowing for deep understanding of the vibrational properties. While the primary hydrogen-bonding interactions are limited to the above quoted structural units, the system revealed very little dispersion of the phonon branches, manifested mainly in the intermolecular vibrations range. Moreover, the studied phase does not exhibit any mechanical instability, which could suggest a displacive structural transformation tendency.

This study was performed using TeraView's Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://www.sciencedirect.com/science/article/pii/S0924203114001556

Polarization independent broadband terahertz antireflection by deep-subwavelength thin metallic mesh

Lu Ding*, Qing Yang Steve Wu andJing Hua Teng*

Abstract

Broadband antireflection coatings for passive terahertz (THz) components are extremely important in the application of THz technology. Metallic nano-films are commonly used for this purpose. Here a new approach to realize polarization independent broadband antireflection in THz range, based on a meta-surface design is experimentally demonstrated. The internal reflection of a broadband THz pulse (spectral bandwidth of 0.06 – 4 THz) at a Si/air interface can be fully suppressed with a Cr square mesh with deep-subwavelength dimensions. Small nonuniformity of the meta-surface structure can enhance the tolerance on structural parameters for achieving the AR condition. The design concept is applicable to other metals and frequency ranges as well, which opens a new window for future AR coatings.

This study was performed using TeraView's Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://onlinelibrary.wiley.com/

Congressman Tours Electrical Engineering Lab

Earlier this month, Congressman Steve Womack visited the lab of Magda El-Shenawee, professor of electrical engineering, to learn about terahertz imaging research at the College of Engineering.

During his visit, Womack learned about a potential medical application of terahertz imaging for breast cancer treatment. Researchers in El-Shenawee’s lab are developing a process to test tissue from lumpectomies during surgery in order to improve patient outcomes.

A second application of El-Shenawee’s system is in the field of security. Terahertz imaging is not harmful to humans, and it has the potential to identify narcotics, explosives and plastic or ceramic weapons. This makes it ideal for security screening. Researchers demonstrated this capability for Womack, concealing weapons and gun powder on a manikin, then revealing the hidden weapons with the imaging system.

“We are very pleased that Congressman Womack took the time to learn about this timely research,” said Juan Balda, head of the Department of Electrical Engineering. “Dr. El-Shenawee’s work has potential to contribute to advances in several different fields ranging from biomedical to security, and the congressman’s interest shows that he understands the importance of innovative engineering projects like this one to the economic development of our state.”

For the full article visit: http://newswire.uark.edu/articles/25171/congressman-tours-electrical-engineering-lab

High-Speed and Broadband Terahertz Wave Modulators Based on Large-Area Graphene Field-Effect Transistors

Qi-Ye Wen, Qi Mao, wee tian, Tian-Long Wen, Zhi Chen, Qing-Hui Yang, and Huaiwu ZHANG

Abstract

We present a broadband terahertz wave modulator with large modulation depth and fast switch speed by cautiously selecting the gate dielectric materials in a large-area graphene field-effect transistor (GFET). An ultrathin Al2O3 film (~60 nm) is deposited by atomic-layer-deposition technique as a high-ĸ gate dielectric layer, which reduces the Coulomb impurity scattering and cavity effect thus greatly improves the modulation performance. Our modulator has achieved a high modulation depth of 22 % and modulation speed of 170 kHz in a frequency range from 0.4 to 1.5 THz, which is vital for many THz technology applications as well as for fundamental researches.

This study was performed using TeraView's Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://www.opticsinfobase.org/ol/upcoming_pdf.cfm?id=216913

TeraView at IRMMW-THz 2014

TeraView are currently at IRMMW-THz 2014!

Both Dr Philip Taday and Rob May are in attendance and will be at the TeraView booth (#21) throughout the event.

If you would like to arrange a meeting please contact Dr Philip Taday:

Dr Philip Taday
Head of Applications
TeraView Limited
Cambridge

E-mail: philip.taday@teraview.com
Tel: +(44) 1223 435380
Cell: +(44) 7887 994018

www.teraview.com

Terahertz time-domain spectroscopy for measurement of particle sizes of fexofenadine hydrochloride

Anna Sadloňová, Vojtech Kresalek, Tomas Bata

Abstract

Time domain spectroscopy is one of the new methods of terahertz radiation used for wide spectrum of the industry. More extended sector is the security system much like the sector of the medicine. The main focus is orientated to detection and identification of the substances. This study is focused on the measurement of the particle size of pharmaceuticals. The characteristic absorption features will be studied experimentally by Terahertz time-domain spectroscopy. The results are identified for processing by one of the statistical method usable for such variable groups. The three samples of the pharmaceutical– Fexofenadine Hydrochloride (antihistamine) will be compared between themselves. Mentioned samples are supplied by different suppliers. The main focus will be put on the pharmaceutical differences of the same pharmaceutical that are commonly available on the markets. Terahertz time-domain spectroscopy setup was used to measure absorbance spectra of each sample in the range from 1 THz to 3 THz (it was used the device TPS Spectra 3000 produced by TeraView Ltd . The device that belongs to the first commercial machine developed in this company for measurement of the substances by transmission spectroscopy method.). During the testing was used the vacuum for purging the measurement chamber from water vapors.

This study was performed using TeraView's Spectra 3000 system. (TeraView, Cambridge, UK)

TeraView Continues to Make Waves at IRMMW-THz 2014

TeraView invites you to visit us at IRMMW-THz 2014!

Dr. Philip Taday and Rob May will both be attending the event, with Rob May giving a keynote talk on Monday the 15th of September - 11:30 in the Tuscon Room:

Terahertz Car Paint Thickness Sensor: Out of The Lab and Into the Factory

Don't miss out on this opportunity to learn more about TeraView's recent development and applications!

TeraView will be at Booth #21

If you would like to pre-arrange a meeting, please e-mail Dr. Phil Taday.

Broadband Terahertz Sensing on Spoof Plasmon Surfaces

Binghao Ng , Stephen M. Hanham , Jianfeng Wu , Antonio I. Fernández-Domínguez , Norbert Klein , Yun Fook Liew , Mark B.H. Breese , Minghui Hong , and Stefan A. Maier

Abstract

In this paper, we show that broadband spectral data can be experimentally extracted from corrugated metallic surfaces consisting of a linear array of subwavelength grooves supporting tightly confined spoof plasmons. Using a combination of the scattering edge coupling method and short-time Fourier transform, we are able to discern the group velocity characteristics of a spoof plasmon pulse which in turn allows for the extraction of broadband dispersion data from 0.4 THz to 1.44 THz in a single measurement. Refractive index sensing of various fluids is demonstrated at microlitre volume quantities by monitoring changes in not only the dispersion relation but also the frequency dependent attenuation of the spoof plasmons. This gives information about both the real and imaginary part of the refractive index of an analyte, indicating the potential for spoof plasmon surfaces to fully characterise substances in the terahertz regime. Lastly, we show that the strong electromagnetic field confinement near the effective spoof plasmon frequency allows for surface enhanced absorption spectroscopy, demonstrated here with α-lactose monohydrate powder. This allows us to take a more spectroscopic approach to THz sensing whereby substances can be uniquely identified by their spectral fingerprints. The enhanced light-matter interactions that occur in the vicinity of the spoof plasmon surface allows for a more efficient use of the limited power of current terahertz sources. Together with the ability to integrate spoof plasmon surfaces with microfluidics and to freely design its electromagnetic properties, we believe that these surfaces can be a very versatile platform on which chip-scale terahertz sensing can be performed.

This study was performed using TeraView's Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://pubs.acs.org/doi/abs/10.1021/ph500272n