Abstract-Optically enhanced terahertz modulation and sensing in aqueous environment with gold nanorods

Ruiyun Zhou, Chen Wang, Yuxin Huang, Wendao Xu, Lijuan Xie, Yibin Ying,

https://www.sciencedirect.com/science/article/abs/pii/S0143816619317348

Terahertz (THz) technique, with plenty attractive properties such as its prominent detecting ability, non-destruction and non-ionization, has been getting increased attention. THz modulator, enabling efficient manipulation, is crucial for THz devices and sensing applications. However, its practical implementation still remains a challenge because of the small modulation depth, slow modulation rate and difficult operation way. Nanomaterials have been constantly creating possibilities for the advancement of THz technology. Considering their excellent optical and electrical characteristics, gold nanorods (GNRs) are integrated with silicon-based materials to improve the performance for THz modulation, so as to promote the possibility of THz sensing in aqueous environment. In this paper, the modulation ability of THz wave based on bare silicon with/without dried GNR film, liquid cell with GNR solutions, and silicon channel with GNR solutions is systematically investigated. According to the results, a six-time larger modulation depth can be realized with the plasmonic effect of GNRs through infrared laser irradiation, which is employed to increase the protein detection sensitivity up to ppm level in water state. It is anticipated that integrating nanomaterials with THz functional devices is meaningful to improve the performance of THz technology, which could facilitate its wide applications in various fields.

Abstract-Temperature-dependent terahertz vibrational spectra of tetracycline and its degradation products

Lijuan Xie, Chen Wang, Min Chen, Biao-Bing Jin, Ruiyun Zhou, Yuxin Huang, Saima Hameed, Yibin Ying

https://www.sciencedirect.com/science/article/pii/S1386142519305694#!

Terahertz (THz) spectroscopy has emerged as an attractive technique for qualitative and quantitative detection. Analysis of these chemicals in the THz range under various temperatures can yield detailed information on molecular vibrational modes, which is of utmost importance for effective detection. Here we report the use of THz time-domain spectroscopy (THz-TDS) to measure tetracyclines hydrochloride (TCH) and its degradation products including epitetracycline hydrochloride (ETCH), anhydrotetracycline hydrochloride (ATCH), and epianhydrotetracycline hydrochloride (EATCH) over the temperature range of 4.5–300 K for the first time. The results showed that these four tetracyclines exhibited numerous distinct spectral features in frequency-dependent absorption spectra, which demonstrated the qualitative capacity of THz-TDS. Through density functional theory (DFT) calculations and analysis of temperature-dependent absorption spectra, the origin of the observed terahertz absorption peaks of these four tetracyclines were well interpreted. This study could lay the foundation for high-performance analysis of biological and chemical molecules by THz spectroscopy, which is essential for sensing application.

Abstract-Terahertz biosensing with a graphene-metamaterial heterostructure platform

Wendao Xu, Lijuan Xie,Jianfei Zhu, Longhua Tang, Ranjan Singh, Chen Wang, Yungui Ma, Hou-Tong Chen, Yibin Ying,

https://www.sciencedirect.com/science/article/pii/S0008622318308662

Terahertz (THz) radiation attracted great interest in the fields of material characterization, nondestructive security screening, clinical diagnostics, and identification of chemicals and molecules. Label-free THz sensing of trace amount of targets including biomolecules is promising because of their rich spectral fingerprint in this electromagnetic region; however, improving the sensitivity remains to be a challenge, partially due to the limitations of THz sources and detectors. The resonantly enhanced electromagnetic fields in metamaterialsand metasurfaces offer a potentially viable solution, although highly complicated decoration process is still needed for biosensing on the surface of metamaterials. Here we demonstrate a simple biosensing platform by integrating a monolayer graphene on a THz metamaterial absorber cavity, where the introduction of sensing targets results in a large change of the metamaterial resonant absorption (or reflection) because of their strong interaction with graphene. We experimentally show its ultrahigh sensitivity through detecting trace amount of chlorpyrifos methyl down to 0.2 ng. Using simple decoration steps and utilizing DNA to capture thrombin, we further show the feasibility of this platform serving as a sensitive biosensor.

Abstract-Terahertz spectroscopic imaging with discriminant analysis for detecting foreign materials among sausages

Chen Wang, Ruiyun Zhou, Yuxin Huang, Lijuan Xie, Yibin Ying,


https://www.sciencedirect.com/science/article/pii/S0956713518305255

The accurate and rapid detection of foreign materials in food products is essential for ensuring food safety and quality. Terahertz (THz) imaging is an emerging technology for non-destructive detection in food industrial with the advantages of non-ionization and spectroscopic fingerprinting. In this study, we have attempted to explore the effectiveness of THz spectroscopic imaging for foreign material detection in food with complicated compositions. The feasibility of locating contaminations in sausages were demonstrated through typical spectral comparison, spectral classification assisted by principal component analysis and discriminant analysis methods, and one-dimensional scanning spectral analysis. Our imaging results indicated THz spectroscopic imaging has the ability to locate metal contaminations in sausages no matter what part of sausages is as the food matrix. This study will provide new knowledge about foreign material detection in food with complicated compositions and a basis for parameters selection of continuous-wave THz imaging for contamination detection in this case

Abstract-Metallic mesh devices-based terahertz parallel-plate resonators: characteristics and applications

Chen Wang, Xinwei Li, Yuxin Huang, Wendao Xu, Ruiyun Zhou, Ruiqian Wang, Lijuan Xie, and Yibin Ying

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-19-24992

The capability to design, fabricate, and optimize metamaterials based on various structures and material platforms has been crucial for the rapid development of modern terahertz (THz) technology. While the detailed structures of artificial unit cells within a metamaterial is certainly worth investigating, there has been increasing demand to integrate novel metamaterials with a traditional functional photonic device to form a hybrid device, whose performance is so significantly improved as to be promising for real-world applications. In this study, we proposed, for the first time, a THz parallel-plate resonator based on metallic mesh devices (MMDs) for chemical sensing applications. We studied the influences of various structural parameters through simulations, fabricated MMD-based resonator devices, and fully characterized the device performance through THz spectroscopy experiments. Furthermore, we experimentally demonstrated that our device can detect a doxycycline hydrochloride aqueous solution whose concentrations is as low as 1 mg L−1 through resonance frequency shifts, evidencing the device sensitivity capable of delicate chemical sensing tasks. Our work presents a practical and low cost architecture for chemical sensing using THz radiation, which opens new avenues for numerous useful THz devices based on metamaterials.

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

Abstract-Discrimination of Transgenic Rice containing the Cry1Ab Protein using Terahertz Spectroscopy and Chemometrics

Wendao Xu,

Lijuan Xie,

Zunzhong Ye,

Weilu Gao,

Yang Yao,

Min Chen,

Jianyuan Qin

& Yibin Ying

• http://www.nature.com/srep/2015/150708/srep11115/full/srep11115.html

Spectroscopic techniques combined with chemometrics methods have proven to be effective tools for the discrimination of objects with similar properties. In this work, terahertz time-domain spectroscopy (THz-TDS) combined with discriminate analysis (DA) and principal component analysis (PCA) with derivative pretreatments was performed to differentiate transgenic rice (Hua Hui 1, containing the Cry1Ab protein) from its parent (Ming Hui 63). Both rice samples and the Cry1Ab protein were ground and pressed into pellets for terahertz (THz) measurements. The resulting time-domain spectra were transformed into frequency-domain spectra, and then, the transmittances of the rice and Cry1Ab protein were calculated. By applying the first derivative of the THz spectra in conjunction with the DA model, the discrimination of transgenic from non-transgenic rice was possible with accuracies up to 89.4% and 85.0% for the calibration set and validation set, respectively. The results indicated that THz spectroscopic techniques and chemometrics methods could be new feasible ways to differentiate transgenic rice.

Abstract-Extraordinary sensitivity enhancement by metasurfaces in terahertz detection of antibiotics

Lijuan Xie,

Weilu Gao,

Jie Shu,

Yibin Ying

& Junichiro Kono

http://www.nature.com/srep/2015/150302/srep08671/full/srep08671.html?WT.ec_id=SREP-639-20150303

We have detected trace amounts of molecules of antibiotics (kanamycin sulfate) dispersed on metasurfaces with terahertz (THz) spectroscopy. Utilizing the extraordinary optical transmission resonance of an array of square-shaped slits on a silicon substrate at ~0.3 THz, we were able to monitor varying concentrations of kanamycin sulfate as low as ~100 picogram/L. In contrast, the lowest detectable concentration of kanamycin sulfate on silicon without any metallic structure was ~1 gram/L. This dramatic ~10¹⁰ times enhancement of sensitivity is due to the near-field enhancement of THz electric fields by the metamaterial structure. This result thus demonstrates the power and usefulness of metamaterial-assisted THz spectroscopy in trace molecular detection for biological and chemical sensing as well as for food product quality and safety inspection and control.