Abstract-High-sensitivity identification of aflatoxin B1 and B2 using terahertz time-domain spectroscopy and metamaterial-based terahertz biosensor

Rong Zhao, Bin Zou, Gu-Ling Zhang, Dongqian Xu, Yuping Yang,

https://iopscience.iop.org/article/10.1088/1361-6463/ab6f90/pdf

Aflatoxin B1 and B2 are extremely toxic to humans and commonly found in agricultural and food products. Thus, rapid and accurate detection and identification of these substances is essential to prevent human and animal health problems due to their consumption. Here, we present a metamaterial-based terahertz biosensor that has the potential for high-sensitivity, quantitative identification of aflatoxin B1 and B2 in extremely small amounts. By combining with conventional terahertz time-domain spectroscopy and the Maxwell-Garnett effective medium theory, we directly obtained accurate information of the refractive index, absorption coefficient, and dielectric function of these aflatoxins, which are essential parameters to understand their physical properties for their identification. Furthermore, the resonant frequency of the proposed biosensor was designed in a frequency range wherein the largest difference between the two aflatoxins was observed. In addition, the sensing of aflatoxin B1 and B2 was demonstrated as a function of content, thickness and dielectric constant by the THz biosensor and finite-element simulation. Consequently, a qualitative and quantitative identification of trace aflatoxin B1 and B2 without label was achieved.

Abstract-Experimental demonstration of ultra-large-scale terahertz all-dielectric metamaterials

Ke Bi, Daquan Yang, Jia Chen, Qingmin Wang, Hongya Wu, Chuwen Lan, and Yuping Yang

Microscope images of the fabricated (a) ZrO2${\mathrm{ZrO}}_2$ and (b) Al2O3${\mathrm{Al}}_2{\mathrm{O}}_3$ all-dielectric metamaterials. Photographs of (c) the fabrication process and (d) the fabricated ultra-large-scale flexible all-dielectric metamaterial using the MTAS method. (e) Simulated and measured transmissions for ZrO2${\mathrm{ZrO}}_2$ and Al2O3${\mathrm{Al}}_2{\mathrm{O}}_3$ all-dielectric metamaterials. The insets are simulated magnetic field intensity distributions at the corresponding resonance dips in the H–k plane.

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-7-4-457

All-dielectric metamaterials have emerged as a promising platform for low-loss and highly efficient terahertz devices. However, existing fabrication methods have difficulty in achieving a good balance between precision and cost. Here, inspired by the nano-template-assisted self-assembly method, we develop a micro-template-assisted self-assembly (MTAS) method to prepare large-scale, high-precision, and flexible ceramic microsphere all-dielectric metamaterials with an area exceeding 900  cm×900  cm$900\mathrm{cm}\times 900\mathrm{cm}$. Free from organic solvents, vacuum, and complex equipment, the MTAS method ensures low-cost and environmentally friendly fabrication. The ceramic microsphere resonators can be readily assembled into nearly arbitrary arrangements and complex aggregates, such as dimers, trimers, quadrumers, and chains. Finally, using the heat-shrinkable substrate and dipole coupling effect, a broadband reflector with a bandwidth of 0.15 THz and a reflection of up to 95% is demonstrated. This work provides a versatile and powerful platform for terahertz all-dielectric metamaterials, with potential to be applied in a wide variety of high-efficiency terahertz devices.

© 2019 Chinese Laser Press

Abstract-High-sensitivity and label-free identification of a transgenic genome using a terahertz meta-biosensor

Yuping Yang, Dongqian Xu, and Weili Zhang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-24-31589

A high-sensitivity and label-free method for identifying a transgenic plant genome is highly desirable in plant biotechnology. Here, we present a terahertz (THz) metamaterial (MM)-based biosensor that comprises a planar array of gold split-ring (SR) resonators capable of sensing a considerable shift in the resonance frequency due to the change of the dielectric environment on the MM chip. The meta-sensor is employed to detect transgenic tomato genome DNAs by THz time-domain spectroscopy. The experimental results were confirmed by finite-element modeling through varying the thickness and dielectric constant of the DNA overlayer. Consequently, high-efficiency and label-free discrimination between the wild-type and transgenic genome DNA was achieved.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Identification terahertz spectra for the dyestuffs based on principal component analysis and Savitzky-Golay filter

Haishun Liu, Zhenwei Zhang, Yuping Yang, Tao Chen, Cunlin Zhang,



https://www.sciencedirect.com/science/article/pii/S0030402618310519

Terahertz time-domain spectroscopy (THz-TDS) was employed to measure the absorption spectra for three types of dyestuff at the frequency range of 0.3~2.2 THz. The raw spectra data were implemented dimensionality reduction by using principal component analysis (PCA). Depending on the weak cluster trend determined by the score plot, different levels of Savitzky-Golay (SG) smoothing combined with PCA processing was performed for elevating the recognition rate. The recognition effects were assessed by fuzzy c-means (FCM) and k-means clustering techniques, which consistently demonstrated the combination of polynomial order 1 and window size 5 for SG smoothing achieved the highest accuracy of 94.44%. For k-means and FCM clustering, the identification accuracies of raw spectra were 87.5% and 84.72% respectively, realizing the elevation recognition rate by using SG smoothing with polynomial order 1 and window size 5. Our results suggested SG smoothing coupled with PCA was a potent method to cope with THz spectra recognition for dyestuffs.

Abstract-Dimensionality Reduction for Identification of Hepatic Tumor Samples Based on Terahertz Time-Domain Spectroscopy

 Haishun Liu,  Zhenwei Zhang, Xin Zhang,  Yuping Yang, Zhuoyong Zhang, Xiangyi Liu, Fan Wang,  Yiding Han, Cunlin Zhang

https://ieeexplore.ieee.org/document/8333778/

Terahertz time-domain spectroscopy (THz-TDS) combining with chemometrics methods was proposed for the identification of hepatic tumors. Two linear compression methods, principle component analysis and locality preserving projections (LPPs), and a nonlinear method, Isomap, were used to reduce the dimensionality of the measured dataset. Comparing two-dimensional (2-D) data reduced by these three dimensionality reduction techniques, only 2-D Isomap plot could separate the distances between two classes for the THz time-domain data and LPP had capacity of distinguishing two types of samples building on frequency-domain data. The best classification accuracies from 2-D time-domain data were 99.81±0.30% and 99.69±0.61% given by Isomap probabilistic neural network (PNN) and Isomap support vector machine (SVM), respectively, while the best classification results of 2-D frequency-domain data were 100.00±0.00%, 99.75±0.32% provided by LPP-PNN, LPP-SVM. The results showed that Isomap and LPP are appropriate techniques to reflect the nonlinear manifold of the THz data. The THz technology either in time-domain or frequency-domain coupled with Isomap-PNN or LPP-PNN could offer a potential procedure to identify hepatic tumors.

Abstract-Optical Controlled Terahertz Modulator Based on Tungsten Disulfide Nanosheet

• Zhiyuan Fan, 
• Zhaoxin Geng, 
• Xiaoqin Lv, 
• Yue Su, 
• Yuping Yang, 
• Jian Liu & 
• Hongda Chen

https://www.nature.com/articles/s41598-017-13864-5?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+srep%2Frss%2Fcurrent+%28Scientific+Reports%29

The terahertz (THz) modulator, which will be applied in next-generation wireless communication, is a key device in a THz communication system. Current THz modulators based on traditional semiconductors and metamaterials have limited modulation depth or modulation range. Therefore, a THz modulator based on annealed tungsten disulfide (WS2, p-type) and high-resistivity silicon (n-type) is demonstrated. Pumped by a laser, the modulator presents a laser power-dependent modulation effect. Ranging from 0.25 to 2 THz, the modulation depth reaches 99% when the pumping laser is 2.59 W/cm2. The modulator works because the p-n heterojunction can separate and limit carriers to change the conductivity of the device, which results in a modulation of the THz wave. The wide band gap of WS2 can promote the separation and limitation of carriers to obtain a larger modulation depth, which provides a new direction for choosing new materials and new structures to fabricate a better THz modulator.

Abstract-THz Spectroscopic Identification of Red Mineral Pigments in Ancient Chinese Artworks

Yuping Yang, Dongwei Zhai, Zhenwei Zhang, Cunlin Zhang

https://link.springer.com/article/10.1007%2Fs10762-017-0408-8

Nondestructive analysis of historical objects is of significance for cultural heritage conservation. In this paper, terahertz time-domain spectroscopy (THz-TDS) was used to distinguish seven red mineral pigments used in ancient Chinese artworks. Two absorption features of natural minerals HgS and four highly resolved spectral features of mineral pigment Pb3O4 were observed and identified as their fingerprints in the range 0.2 to 3.0 THz, based on which the spatial distribution of individual chemical substances including cinnabar, vermilion, and red lead were clearly revealed at various frequencies using terahertz spectroscopy imaging. Moreover, a noncontact evaluation of thickness changing and dehydration of a wet painting was monitored by inferring time delay as well as signal amplitude of THz pulses transmitted through the painting. In order to demonstrate the feasibility of THz-TDS and THz imaging for authentic artworks detection, a complete set of THz analysis of two nineteenth century wall paintings discovered in the Fuchen Temple of the Forbidden City, Beijing, was performed and the results indicate that THz measurement techniques provide a noninvasive and nondestructive solution for the care, preservation, and restoration of cultural relics.

Abstract-Optically tuned terahertz modulator based on annealed multilayer MoS2

• Yapeng Cao
• , Sheng Gan
• , Zhaoxin Geng
• , Jian Liu
• , Yuping Yang
• , Qiaoling Bao
•  & Hongda Chen

• Scientific Reports 6, Article number: 22899 
• http://www.nature.com/articles/srep22899

Controlling the propagation properties of terahertz waves is very important in terahertz technologies applied in high-speed communication. Therefore a new-type optically tuned terahertz modulator based on multilayer-MoS2 and silicon is experimentally demonstrated. The terahertz transmission could be significantly modulated by changing the power of the pumping laser. With an annealing treatment as a p-doping method, MoS2 on silicon demonstrates a triple enhancement of terahertz modulation depth compared with the bare silicon. This MoS2-based device even exhibited much higher modulation efficiency than the graphene-based device. We also analyzed the mechanism of the modulation enhancement originated from annealed MoS2, and found that it is different from that of graphene-based device. The unique optical modulating properties of the device exhibit tremendous promise for applications in terahertz switch.

Abstract-Terahertz time-domain spectroscopy combined with support vector machines and partial least squares-discriminant analysis applied to diagnosis of cervical carcinoma

Na Qi,   Zhuoyong Zhang,   Yuhong Xiang,   Yuping Yang,  Xueai Liang and   Peter B Harrington  

Anal. Methods, 2015, Accepted Manuscript

DOI: 10.1039/C4AY02665A
Received 09 Nov 2014, Accepted 20 Jan 2015
First published online 20 Jan 2015
http://pubs.rsc.org/en/Content/ArticleLanding/2015/AY/C4AY02665A?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FAY+%28RSC+-+Anal.+Methods+latest+articles%29#!divAbstract

Coupled with terahertz time-domain spectroscopy (THz-TDS) technology, the feasibility of diagnosis of cervical carcinoma using support vector machines (SVM) and partial least squares-discriminant analysis (PLS-DA) had been studied. The terahertz spectra of 52 specimens of cervix were collected. The performance of preprocessing methods of multiplicative scatter correction (MSC), Savitzky-Golay (SG) smoothing and first derivative, principal component orthogonal signal correction (PC-OSC) and emphatic orthogonal signal correction (EOSC) were investigated for PLS-DA and SVM models, respectively. The effects of the different pretreatments methods with respect to classification accuracy were compared. The PLS-DA and SVM models were validated using the bootstrapped Latin-partition method. The SVM and PLS-DA models optimized with the combination of SG first derivative and PC-OSC preprocessing had the best predictive results with classification rates of 94.0 ± 0.4% and 94.0 ± 0.5%, respectively. The proposed procedure proved that terahertz spectroscopy combined with classifiers provides a technology which has potential as a new diagnosis method for cancer tissue.

Abstract-Probing disaggregation of crude oil in magnetic field with terahertz time-domain spectroscopy

Chen Jiang , Kun Zhao , Li J. Zhao , Wu J. Jin ,

Yuping Yang , and Shao H. Chen

Energy Fuels, Just Accepted Manuscript

DOI: 10.1021/ef401984u

Publication Date (Web): January 3, 2014

Copyright © 2014 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/ef401984u

The magnetic technology can significantly change the characteristics of crude oil, and the physical mechanism has received much attention for several years. To date, there is no accurate conclusion yet. Terahertz time domain spectroscopy is employed in this paper to characterize the optical parameters of selected wax-bearing crude oil under the action of a magnetic field. The corresponding absorption coefficient and extinction coefficient of samples are obtained by fast Fourier transform frequency-domain spectrum, and the aggregation characteristics of particles are analyzed in crude oil under magnetic field. The decrease of extinction coefficient may be suggested as a qualitative proof of a magnetic-field-induced disaggregation of the suspended colloidal particles. Terahertz time domain spectroscopy may be a powerful tool to characterize the particle disaggregation state in crude oil.