scholarly journals Temperature dependent poly(L-lactide) crystallization investigated by Fourier transform terahertz spectroscopy

2021 ◽  
Author(s):  
Seiichiro Ariyoshi ◽  
Satoshi Ohnishi ◽  
Hikaru Mikami ◽  
Hideto Tsuji ◽  
Yuki Arakawa ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Absorption Spectra ◽  
Terahertz Spectroscopy ◽  
Thz Spectroscopy ◽  
Frequency Range ◽  
Temperature Dependent ◽  
Thz Absorption

Poly(L-lactide) (PLLA) was investigated by Fourier transform terahertz (THz) spectroscopy over the frequency range of 1.0 – 8.5 THz. THz absorption spectra were acquired for PLLA samples isothermally crystallized at...

High-Precision Continuous-Wave Terahertz Spectroscopy Based on a Photomixing Technique for Identifying Pearls

2019 ◽  
Vol 73 (12) ◽  
pp. 1388-1393
Author(s):  
Chihoon Kim ◽  
Taeksoo Ji
Keyword(s):  
Optical Coherence Tomography ◽  
Fourier Transform ◽  
Ir Spectroscopy ◽  
Continuous Wave ◽  
Terahertz Spectroscopy ◽  
Thz Spectroscopy ◽  
Ft Ir ◽  
Thz Absorption ◽  
Ft Ir Spectroscopy ◽  
Cultured Pearls

We present the accurate terahertz spectra of between imitation and cultured pearls using continuous-wave terahertz (CW-THz) spectroscopy. Using Fourier transform infrared (FT-IR) spectroscopy and optical coherence tomography (OCT) measurements, cultured pearls can be distinguished from imitation pearls by observing distinct absorption peaks and discriminative boundaries. The THz absorption spectra up to 0.3 THz obtained from CW-THz spectroscopy show several absorption peaks at specific frequencies with the cultured pearls but no peaks with the imitation pearls, which results from the existence of the nacre polymorph of cultured pearls. Hence, it is expected that the CW-THz system proposed herein will be applicable to fast, nondestructive spectrum analysis including pearl identification.

THz SPECTROSCOPY OF PROTEINS IN WATER: DIRECT ABSORPTION AND CIRCULAR DICHROISM

2007 ◽  
Vol 17 (04) ◽  
pp. 709-718 ◽  
Author(s):  
JING XU ◽  
KEVIN W. PLAXCO ◽  
S. JAMES ALLEN
Keyword(s):  
Circular Dichroism ◽  
Absorption Spectra ◽  
Magnetic Circular Dichroism ◽  
Broad Band ◽  
Thz Spectroscopy ◽  
Direct Absorption ◽  
Frequency Range ◽  
Egg White Lysozyme ◽  
Terahertz Absorption ◽  
Circular Dichroïsm

Many of the functionally relevant collective vibrations of proteins and other biopolymers are expected to occur at terahertz frequencies. Precise absorption measurements combined with careful titration of biopolymers in water have allowed us to directly measure the terahertz absorption spectra associated with these motions, despite the strong background absorption of the solvent. We have also explored the circular dichroism spectroscopy of biomolecules over this same frequency range. Since circular dichroism requires the presence of net chirality in a molecule and chirality is present in nearly all biomaterial, it has the potential to capture the background free spectral features in biopolymers. To undertake these studies we have developed a broad band terahertz spectrometer suitable for both direct absorption and circular dichroism measurements of proteins in water between 0.75 – 3.72 THz. Direct terahertz absorption spectra of prototypical proteins bovine serum albumin (BSA) and hen egg white lysozyme have been documented and are described here. We have also successfully demonstrated the magnetic circular dichroism in semiconductors, and placed an upper bound on the terahertz circular dichroism signature of solvated BSA. In the terahertz frequency range, it appears that circular dichroism signatures are exceedingly small and detection remains a challenge.

Structurally Sensitive Changes in Absorption THz Spectra of Corticosteroids

2010 ◽  
Vol 5 (4) ◽  
pp. 162-167
Author(s):  
Irina N. Smirnova ◽  
Elena V. Fedulova ◽  
Maxim M. Nazarov ◽  
Оlga P. Cherkasova
Keyword(s):  
Steroid Hormones ◽  
Absorption Spectra ◽  
Time Domain ◽  
Spectral Response ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Characteristic Lines ◽  
Pure Substances ◽  
Thz Absorption ◽  
The Given

The series of steroid hormones, such as progesterone, 17α-hydroxyprogesterone, cortisol and other was measured by terahertz time-domain spectroscopy (THz TDS). It was obtained that THz absorption spectra of steroid hormones have characteristic lines of absorption in the frequency range 0.1-3.0 THz. We investigate the relation between the position of side functional groups and THz spectral response. Besides pellets of polycrystalline pure substances, steroids solution in methanol was analyzed. The given method can be applied for express diagnostics of different classes of steroid

scholarly journals A Reliable Method for Identification of Antibiotics by Terahertz Spectroscopy and SVM

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Jin Guo ◽  
Hu Deng ◽  
Quancheng Liu ◽  
Linyu Chen ◽  
Zhonggang Xiong ◽  
...  
Keyword(s):  
Dimensionality Reduction ◽  
Absorption Spectra ◽  
Reliable Method ◽  
Terahertz Spectroscopy ◽  
Principal Component ◽  
Support Vector ◽  
Thz Spectroscopy ◽  
Model Parameters ◽  
Training Time ◽  
Svm Model

Given the extensive use of antibiotics at present, the identification of antibiotics and production quality monitoring are of high importance. However, conventional antibiotic identification methods have a low sensitivity and a long detection time. Here, we propose an identification method that combines terahertz (THz) spectroscopy and chemometric technology. THz time-domain spectroscopy (THz-TDS) was performed for sixteen types of antibiotics, including β-lactam, cephalosporins, macrolides, and tetracyclines. The absorption spectra within the frequency range of 0.2–1.5 THz were calculated. For dimensionality reduction, principal component analysis (PCA) and t-distributed stochastic neighbor embedding (t-SNE) were implemented, respectively. The data after dimensionality reduction were input into a support vector machine (SVM). The model parameters were optimized through grid search (GS), genetic algorithm (GA), and particle swarm optimization (PSO) methods, and the optimal identification results were obtained after comparison across these methods. Experiments indicate a differentiation of the THz absorption spectra among the sixteen types of antibiotics. After dimensionality reduction, the training time of the model significantly decreased. The use of the t-SNE-PSO-SVM model achieved the highest average accuracy on the prediction set, which was 99.91%. Thus, our study does not only confirm that the t-SNE-PSO-SVM model proves to be a reliable method for antibiotics identification, but also confirms that the combination of THz-TDS and chemometric pattern recognition has great potential for drug detection.

scholarly journals Intermolecular vibrational modes of crystalline Poly-(r)-3-Hydroxybutyrate observed at Terahertz frequencies investigated by molecular dynamics

2020 ◽  
Vol 26 (2) ◽  
pp. 21-31
Author(s):  
Md Khorshed Alam ◽  
Md Saif Ishtiaque ◽  
Md Imran Hossain ◽  
Hiromitsu Takaba
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonds ◽  
Absorption Spectra ◽  
Md Simulation ◽  
Vibrational Transition ◽  
Vibrational Modes ◽  
Temperature Dependent ◽  
Terahertz Frequencies ◽  
Thz Absorption ◽  
Oriented Parallel

Terahertz (THz) absorption spectra of poly 3-hydroxyalkanoates (PHB) for different conformations were investigated using molecular dynamics (MD) method. Temperature-dependent THz absorption spectra of PHB were measured over a temperature range of 10 K to 200 K. Peaks around (2.4-2.6THz) and (3.1-3.2THz) were observed due to vibrational transition of PHB, 1stpeaks are polarized perpendicular to c(┴)axis (along a, b axis) and next peaks are oriented parallel to the c(//) axis. The peak around (2.4-2.6THz) was assigned due to vibrational transition of PHB and C-H…O=C hydrogen bonds are oriented perpendicular to the c(┴) axis. We have also investigated orientation of the intermolecular hydrogen bonds by MD simulation and confirmed that it was mainly along the b axis of PHB. THz absorption spectra shifted to the lower frequencies and noticed widening of the absorption peaks that visualized from characteristics of peaks within creasing temperature, which is well reproduce of experimental observation. Bangladesh Journal of Physics, 26(2), 21-31, December 2019

scholarly journals Terahertz Spectroscopy for Characterization of Hydrogen Bonding and Cross-linked Structure Dynamics in Polyurethane

2020 ◽  
Vol 41 (3) ◽  
pp. 265-275 ◽  
Author(s):  
Hiromichi Hoshina ◽  
Yuichi Saito ◽  
Takumi Furuhashi ◽  
Tomomi Shimazaki ◽  
Manabu Sawada ◽  
...  
Keyword(s):  
Dft Calculation ◽  
Terahertz Spectroscopy ◽  
Temperature Dependent ◽  
Absorption Bands ◽  
First Derivative ◽  
Calculation Results ◽  
Thz Absorption ◽  
Reported Data ◽  
Bond Vibration

AbstractTerahertz (THz) absorption spectra of cross-linked polyurethane films were observed at 30–180 °C. The obtained spectra displayed characteristic absorption bands. A band observed at 2.6 THz was assigned to the C=O···N-H hydrogen bond vibration using previously reported data. DFT calculation results confirmed that a band at 7.5 THz arises owing to the torsional vibration of cross-linked molecules containing urethane bonds. The slight changes in the temperature-dependent spectra were analyzed by the first derivative of absorption intensity with temperature. The thermal behavior of absorption intensities indicates the dynamics of hydrogen bonds and cross-linked structures in polyurethane films.

Research on the Terahertz Absorption Spectra of Histidine Enantiomer (L) and its Racemic Compound (DL)

2016 ◽  
Vol 71 (2) ◽  
pp. 194-202 ◽  
Author(s):  
Tao Zhou ◽  
Yidong Wu ◽  
Juncheng Cao ◽  
Liangliang Zou ◽  
Jie Yuan ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Function Theory ◽  
Dft Method ◽  
Density Function Theory ◽  
Vibrational Modes ◽  
Frequency Range ◽  
Racemic Compound ◽  
Terahertz Time Domain Spectroscopy ◽  
Terahertz Absorption ◽  
Thz Absorption

Terahertz time-domain spectroscopy (THz-TDS) is used to investigate the absorption spectra of polycrystalline L- and DL-histidine in the frequency range of 10–100 cm-1. The spectra exhibit distinct differences in peak frequencies between the enantiomer (L-histidine) and racemic compound (DL-histidine). The observed spectral differences are attributed to the intermolecular interactions. With the density function theory (DFT) method, the frequencies of vibrational modes of L-histidine and DL-histidine in the THz range are calculated and well assigned according to the measured spectra. The origin of the observed vibrational modes is found to be non-localized and of a collective (phonon-like) nature, which points to the lattice and skeleton vibrations mediated by the hydrogen bond. Furthermore, we propose and demonstrate a method for determining the composition ratio of histidine mixtures based on the THz absorption spectra.

Feasibility of Using Terahertz Spectroscopy To Detect Seven Different Pesticides in Wheat Flour

2014 ◽  
Vol 77 (12) ◽  
pp. 2081-2087 ◽  
Author(s):  
INHEE MAENG ◽  
SEUNG HYUN BAEK ◽  
HWA YEON KIM ◽  
GYEONG-SIK OK ◽  
SUNG-WOOK CHOI ◽  
...  
Keyword(s):  
Wheat Flour ◽  
High Density Polyethylene ◽  
Terahertz Spectroscopy ◽  
Weight Ratio ◽  
High Density ◽  
Thz Spectroscopy ◽  
Refractive Indices ◽  
Frequency Range ◽  
Specific Absorption ◽  
Effective Medium Model

This study investigated the feasibility of detecting pesticides using terahertz (THz) spectroscopy in high-density polyethylene and/or wheat flour mixtures. The absorption spectra of seven pesticides (dicofol, chlorpyrifos, chlorpyrifos-methyl, daminozide, imidacloprid, diethyldithiocarbamate, and dimethyldithiocarbamate) were measured in the frequency range 0.1 to 3 THz at room temperature. Five of the seven pesticides exhibited specific absorption peaks in the low-energy THz range. The two remaining pesticides had no specific absorption peaks in this frequency range, but they exhibited different frequency-dependent refractive indices. The absorption coefficients of imidacloprid increased with its increasing weight ratio in high-density polyethylene, and the fitted power absorptions and refractive indices using a Maxwell-Garnett effective medium model were comparable to the measured data. Imidacloprid was also identified from its characteristic absorption peaks in wheat flour mixtures, and a linear relationship between the absorption coefficient and the weight ratio was observed. Our results show the potential of detection of selected pesticides in foods, such as wheat flour, using THz spectroscopy.

Conductivity Studies of Schiff Base Ligands Derived from O-Phenylenediamine and Their Co(II) and Zn(II) Complexes

2015 ◽  
Vol 12 (2) ◽  
pp. 13
Author(s):  
Muhamad Faridz Osman ◽  
Karimah Kassim
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Fourier Transform ◽  
Schiff Base ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Impedance Spectroscopy ◽  
Ftir Spectroscopy ◽  
Coordination Complexes ◽  
Frequency Range ◽  
Schiff Base Ligands

The coordination complexes of Co(II) and Zn(II) with Schiff bases derived from o-phenylenediamine and substituted 2-hydroxybenzaldehyde were prepared All compounds were characterized by Fourier transform infrared (FTIR) spectroscopy and Nuclear magnetic resonance (NMR) spectroscopy elemental analyzers. They were analyzed using impedance spectroscopy in the frequency range of 100Hz-1 MHz. LI and L2 showed higher conductivity compared to their metal complexes, which had values of 1.3 7 x 10-7 and 6.13 x 10-8 S/cm respectively. 

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