scholarly journals Terahertz Time-domain Spectroscopy as a Novel Tool for Crystallographic Analysis in Cellulose: Cellulose I to Cellulose Ii, Tracing the Structural Changes Under Chemical Treatment

2021 ◽  
Author(s):  
Han Wang ◽  
Hiroki Kataoka ◽  
Satoru Tsuchikawa ◽  
Tetsuya Inagaki
Keyword(s):  
Absorption Coefficient ◽  
Time Domain ◽  
Structural Changes ◽  
Crystalline Lattice ◽  
Thz Radiation ◽  
Cellulose Ii ◽  
Cellulose I ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Thz Absorption

Abstract Terahertz time-domain spectroscopy (THz-TDS) has expanded possibilities in cellulose crystallography research, as THz radiation detects most intermolecular vibrations and responds to the phonons of crystalline lattices. In this study, we traced the transformation of the cellulose crystalline lattice from cellulose I to cellulose II by THz-TDS and X-ray powder diffraction. Cellulose II was obtained by treating cellulose I with NaOH of different concentrations (0 wt%–20 wt%, at 2 wt% intervals). The THz absorption coefficient spectra of cellulose II showed three characteristic peaks (at 1.32 THz, 1.76 THz, and 2.77 THz). The THz absorption coefficient spectra of cellulose II treated with 20-wt% NaOH and cellulose I without NaOH treatment were fitted by a seventh-order Fourier series. Thus, the THz absorption coefficient spectra of samples treated with NaOH of other concentrations could be considered a combination of these two fitted profiles of cellulose I and cellulose II, multiplied by different coefficients. Furthermore, the coefficients could reflect the relative contents of cellulose I and cellulose II in the samples.

scholarly journals Terahertz Time-Domain Spectroscopy of Graphene Nanoflakes Embedded in Polymer Matrix

2019 ◽  
Vol 9 (3) ◽  
pp. 391 ◽  
Author(s):  
Anton Koroliov ◽  
Genyu Chen ◽  
Kenneth M. Goodfellow ◽  
A. Nick Vamivakas ◽  
Zygmunt Staniszewski ◽  
...  
Keyword(s):  
Polymer Matrix ◽  
Time Domain ◽  
Thz Radiation ◽  
Complex Conductivity ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Graphene Nanocomposites ◽  
Graphene Nanoflakes ◽  
Exfoliated Graphene

The terahertz time-domain spectroscopy (THz-TDS) technique has been used to obtain transmission THz-radiation spectra of polymer nanocomposites containing a controlled amount of exfoliated graphene. Graphene nanocomposites (1 wt%) that were used in this work were based on poly(ethylene terephthalate-ethylene dilinoleate) (PET-DLA) matrix and were prepared via a kilo-scale (suitable for research and development, and prototyping) in-situ polymerization. This was followed by compression molding into 0.3-mm-thick and 0.9-mm-thick foils. Transmission electron microscopy (TEM) and Raman studies were used to confirm that the graphene nanoflakes dispersed in a polymer matrix consisted of a few-layer graphene. The THz-radiation transients were generated and detected using a low-temperature–grown GaAs photoconductive emitter and detector, both excited by 100-fs-wide, 800-nm-wavelength optical pulses, generated at a 76-MHz repetition rate by a Ti:Sapphire laser. Time-domain signals transmitted through the nitrogen, neat polymer reference, and 1-wt% graphene-polymer nanocomposite samples were recorded and subsequently converted into the spectral domain by means of a fast Fourier transformation. The spectral range of our spectrometer was up to 4 THz, and measurements were taken at room temperature in a dry nitrogen environment. We collected a family of spectra and, based on Fresnel equations, performed a numerical analysis, that allowed us to extract the THz-frequency-range refractive index and absorption coefficient and their dependences on the sample composition and graphene content. Using the Clausius-Mossotti relation, we also managed to estimate the graphene effective dielectric constant to be equal to ~7 ± 2. Finally, we extracted from our experimental data complex conductivity spectra of graphene nanocomposites and successfully fitted them to the Drude-Smith model, demonstrating that our graphene nanoflakes were isolated in their polymer matrix and exhibited highly localized electron backscattering with a femtosecond relaxation time. Our results shed new light on how the incorporation of exfoliated graphene nanoflakes modifies polymer electrical properties in the THz-frequency range. Importantly, they demonstrate that the complex conductivity analysis is a very efficient, macroscopic and non-destructive (contrary to TEM) tool for the characterization of the dispersion of a graphene nanofiller within a copolyester matrix.

scholarly journals Terahertz Time-Domain Spectroscopy Based on Commercially Available 1550 nm Fabry–Perot Laser Diode and ErAs:In(Al)GaAs Photoconductors

2019 ◽  
Vol 9 (13) ◽  
pp. 2704 ◽  
Author(s):  
Kai-Henning Tybussek ◽  
Kevin Kolpatzeck ◽  
Fahd Faridi ◽  
Sascha Preu ◽  
Jan C. Balzer
Keyword(s):  
Laser Diode ◽  
Time Domain ◽  
Dynamic Range ◽  
Laser System ◽  
Industrial Applications ◽  
Thz Radiation ◽  
Full Potential ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Fabry Perot

THz time-domain spectroscopy (TDS) is a promising tool for quality control purposes in industrial applications, but the high cost and the relatively large laser sources still make it difficult to use the full potential of the technology for a decent price. In this work, a THz TDS system, which uses a commercially available Fabry–Perot laser diode emitting at 1550 nm, is presented. By dispersion compensation, pulses with a duration of 544 fs were generated, resulting in THz radiation with a bandwidth of 1.4 THz and a peak dynamic range of 56 dB with state-of-the-art ErAs:In(Al)GaAs photoconducting antennas. These results are compared with those of a conventional and expensive fiber laser system with a 90 fs pulse duration.

Characteristic fingerprint spectrum of neurotransmitter norepinephrine with broadband terahertz time-domain spectroscopy

The Analyst ◽  
2019 ◽  
Vol 144 (8) ◽  
pp. 2504-2510 ◽  
Author(s):  
Zhongjie Zhu ◽  
Chao Cheng ◽  
Chao Chang ◽  
Guanhua Ren ◽  
Jianbing Zhang ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Time Domain ◽  
Vibrational Modes ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Thz Absorption ◽  
Broadband Terahertz

A broadband THz absorption spectrum of NE corresponds to specific vibrational modes.

scholarly journals Transformation and dehydration kinetics of methylene blue hydrates detected by terahertz time-domain spectroscopy

RSC Advances ◽  
2017 ◽  
Vol 7 (66) ◽  
pp. 41667-41674 ◽  
Author(s):  
Shihan Yan ◽  
Hua Zhang ◽  
Zhongbo Yang ◽  
Mingjie Tang ◽  
Mingkun Zhang ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Time Domain ◽  
Terahertz Spectroscopy ◽  
Dehydration Kinetics ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Thz Absorption ◽  
Kinetics Of ◽  
Absorption Features ◽  
Crystalline Hydrates

Three methylene blue crystalline hydrates were identified by terahertz spectroscopy according to their different THz absorption features.

Investigation of Dielectric Properties of Polymers and their Discrimination Using Terahertz Time-Domain Spectroscopy with Principal Component Analysis

2016 ◽  
Vol 71 (3) ◽  
pp. 456-462 ◽  
Author(s):  
Muhammad Mumtaz ◽  
Ahsan Mahmood ◽  
Sabih D. Khan ◽  
M. Aslam Zia ◽  
Mushtaq Ahmed ◽  
...  
Keyword(s):  
Spectral Range ◽  
Time Domain ◽  
Principal Component ◽  
Component Analysis ◽  
Thz Radiation ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Styrene Acrylonitrile ◽  
Characteristic Features ◽  
First Time

Polymers are among the most commonly used materials in our everyday life. They are generally transparent to terahertz (THz) radiation, but are quite difficult to differentiate using optical techniques as few or no characteristic features exist in the spectral range of <2.0 THz for small and portable radiation systems. In this work, we report experimental measurement of refractive indices and absorption coefficients of styrene acrylonitrile (SAN) and Bakelite in the spectral range of 0.2–2.0 THz for the first time. Additionally, we demonstrate that by combining principle component analysis (PCA) with THz time-domain spectroscopy one can differentiate such polymers. In this analysis, the first three principle components PC1, PC2, and PC3 depict >94% variance with a distribution of 72.45%, 11.52%, and 9.38%, respectively.

scholarly journals Quantification of triglyceride levels in fresh human blood by terahertz time-domain spectroscopy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dan Wang ◽  
Yu Zhang ◽  
Juan Han ◽  
Xiao Li ◽  
Xiaofeng Chen ◽  
...  
Keyword(s):  
Human Blood ◽  
Time Domain ◽  
Ex Vivo ◽  
Pearson Correlation ◽  
Terahertz Time Domain Spectroscopy ◽  
Absorption Coefficients ◽  
Time Domain Spectroscopy ◽  
Pilot Clinical Study ◽  
Biochemical Analyzer ◽  
Thz Absorption

AbstractWe conducted a pilot clinical study to investigate ex vivo fresh human blood from 93 patients with coronary heart disease (CHD). The results indicated that terahertz (THz) time-domain spectroscopy (TDS) can be used to quantify triglyceride (TG) levels in human blood. Based on the TG concentrations and corresponding THz absorption coefficients, the Pearson correlation analysis demonstrated that the THz absorption coefficients have a significant negative linear correlation with TG concentration. Comparisons between the THz measurements at 0.2 THz and an automatic biochemical analyzer were performed using an additional 20 blood samples, and the results confirmed that the relative error was less than 15%. Our ex vivo human blood study indicates that the THz technique can be used to assess blood TG levels in clinical diagnostic practice.

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