Recent Advances in Terahertz Time-Domain Spectroscopy and Imaging Techniques for Automation in Agriculture and Food Sector

Khushbu, S.; Yashini, M; Rawson, Ashish; Sunil, C. K.

doi:10.1007/s12161-021-02132-y

Cited by 25 publications

(6 citation statements)

References 142 publications

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“…Terahertz (THz) radiation falls in the electromagnetic spectrum, occupying the frequency range between microwaves and infrared, specifically spanning from 0.1 to 10 terahertz (THz) [1,2] . THz-TDS is a low-energy coherent detection technique that effectively extracts a range of optical parameters, encompassing refractive index, absorption coefficient, and dielectric constant, et al, by recording the amplitude and phase information of the transmitted terahertz electric field [3,4] .…”

Section: Introductionmentioning

confidence: 99%

Influences of single mutation and retinal binding on the THz absorption spectra of CRABP-II based rhodopsin mimics

Wang,

Hu,

Meng

et al. 2024

Preprint

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The collective vibration of many biomolecules such as the skeleton vibration, dipole rotation and conformational bending falls in the terahertz (THz) frequency domain. Terahertz time-domain spectroscopy (THZ-TDS), which is very sensitive to the conformational changes, can be used to characterize the collective vibration of biomolecules. In this study, we investigated the low-frequency THz absorption spectra of two rhodopsin mimics using transmission THz-TDS. Using the normal model analysis (NMA), we successfully modelled the experimental terahertz absorption curve and attributed a unique collective motion pattern to each distinctive terahertz absorption frequency. By comparing the terahertz absorption spectra between without and with retinal, we show that the retinal binding can significantly alters the terahertz absorption spectra as well as the vibration modes. Furthermore, by comparing the terahertz absorption spectra between the two mutants, we observed that the single mutation can significantly change the influence of retinal binding on the terahertz absorption spectrum.

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Section: Introductionmentioning

confidence: 99%

Influences of single mutation and retinal binding on the THz absorption spectra of CRABP-II based rhodopsin mimics

Wang,

Hu,

Meng

et al. 2024

Preprint

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“…In recent years, with the increasing maturity of terahertz technology, terahertz waves have been widely used in many application systems, such as terahertz detection [ 1 , 2 ], sensing [ 3 , 4 ], communication [ 5 , 6 ], and radar [ 7 , 8 ]. Especially in the application of 5G communication [ 9 , 10 ] and the technological development of 6G communication [ 11 , 12 ] in the future, terahertz communication technology has been widely considered by countries all over the world.…”

Section: Introductionmentioning

confidence: 99%

Flexible Metamaterial Quarter-Wave Plate and Its Application in Blocking the Backward Reflection of Terahertz Waves

Sun¹,

Liu²,

et al. 2023

Nanomaterials

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A terahertz flexible metamaterial quarter-wave plate (QWP) is designed and fabricated using polyimide as the substrate in this paper, with a 3 dB axial ratio bandwidth of 0.51 THz and high polarization conversion efficiency and transmittance. The effect of the incidence angle on the polarization conversion performance of the QWP is discussed by measuring the transmissions at multiple incidence angles. The blocking effect of this QWP combined with a polarizer on the backward reflection of terahertz waves is investigated by terahertz time-domain spectral transmission experiments. By adjusting the angle of the QWP and polarizer with respect to the incident light in the optical path, a blocking efficiency of 20 dB can be achieved at a 20° incidence angle, with a bandwidth of 0.25 THz, a maximum blocking efficiency of 58 dB at 1.73 THz, and an insertion loss of only 1.4 dB. Flexible terahertz metamaterial QWPs and polarizers can effectively block harmful reflected waves in terahertz communication and other systems. They have the advantages of a simple structure, ultra-thinness and flexibility, easy integration, no external magnetic field, and no low-temperature and other environmental requirements, thus having broad application prospects for terahertz on-chip integrated systems.

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“…Four kinds of green tea were effectively distinguished by establishing the GA-SVM model and conducted PCA on THz-TDS data [19]. SVM and K-means clustering algorithms were used to identify green tea, white tea, and black tea, and the pesticide thiamethoxam residues in tea were measured [20][21][22]. FTIR and THz-TDS were often used to detect the origin, varieties, storage years, and pesticide residues, almost not used to detect the level of oxidation of tea, which is also the meaning of this paper [21,23,24].…”

Section: Introductionmentioning

confidence: 99%

Infrared and Terahertz Spectra of Pu’er White Tea with Different Degrees of Oxidation

Guo

Sun

et al. 2023

Journal of Food Processing and Preservation

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In this work, the Fourier transform infrared spectroscopy (FTIR) and Terahertz time domain spectra (THz-TDS) were employed to study Pu’er white tea with different oxidation levels by changing the withering time. The strongest absorption peak of 3359 cm-1 in FTIR spectra comes from the proteins and polysaccharides. Several intensity ratios of the characteristic absorption peaks with different oxidation levels were analyzed. The white tea with different oxidation levels can be distinguished from the absorbance of THz-TDS in the range of 0.5–1.5 THz. The refractive index calculated from THz-TDS was between 1.42 and 1.44. Principal component analysis (PCA) using FTIR absorbance data showed that the scattered points of PC1 and PC2 can be well distributed in different districts. Hierarchical cluster analysis (HCA) helped to carry out the clustering results of different white tea samples. The sample with overoxidation level can be distinguished by PCA and HCA using THz-TDS absorbance data. Therefore, FTIR might be a convenient, fast, and nondestructive strategy for identifying white tea with different oxidation levels. THz-TDS combined with some software algorithms can be applied to distinguish the different oxidation-processed tea.

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Recent Advances in Terahertz Time-Domain Spectroscopy and Imaging Techniques for Automation in Agriculture and Food Sector

Cited by 25 publications

References 142 publications

Influences of single mutation and retinal binding on the THz absorption spectra of CRABP-II based rhodopsin mimics

Influences of single mutation and retinal binding on the THz absorption spectra of CRABP-II based rhodopsin mimics

Flexible Metamaterial Quarter-Wave Plate and Its Application in Blocking the Backward Reflection of Terahertz Waves

Infrared and Terahertz Spectra of Pu’er White Tea with Different Degrees of Oxidation

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