Quantitative analysis of direct oral anticoagulant rivaroxaban by terahertz spectroscopy

Identification of Panax notoginseng origin using terahertz precision spectroscopy and neural network algorithm

Panax notoginseng (P. notoginseng), a Chinese herb containing various saponins, benefits immune system in medicines development, which from Wenshan (authentic cultivation) is often counterfeited by others for large demand and limited supply. Here, we proposed a method for identifying P. notoginseng origin combining terahertz (THz) precision spectroscopy and neural network. Based on the comparative analysis of four qualitative identification methods, we chose high-performance liquid chromatography (HPLC) and THz spectroscopy to detect 252 samples from five origins. After classifications using Convolutional Neural Networks (CNNs) model, we found that the performance of THz spectra was superior to that of HPLC. The underlying mechanism is that there are clear nonlinear relations among the THz spectra and the origins due to the wide spectra and multi-parameter characteristics, which makes the accuracy of five-classification origin identification up to 97.62%. This study realizes the rapid, non-destructive and accurate identification of P. notoginseng origin, providing a practical reference for herbal medicine.

Quantitative protein sensing with germanium THz-antennas manufactured using CMOS processes

The development of a CMOS manufactured THz sensing platform could enable the integration of state-of-the-art sensing principles with the mixed signal electronics ecosystem in small footprint, low-cost devices. To this aim, in this work we demonstrate a label-free protein sensing platform using highly doped germanium plasmonic antennas realized on Si and SOI substrates and operating in the THz range of the electromagnetic spectrum. The antenna response to different concentrations of BSA shows in both cases a linear response with saturation above 20 mg/mL. Ge antennas on SOI substrates feature a two-fold sensitivity as compared to conventional Si substrates, reaching a value of 6 GHz/(mg/mL), which is four-fold what reported using metal-based metamaterials. We believe that this result could pave the way to a low-cost lab-on-a-chip biosensing platform.

The necessity of periodic boundary conditions for the accurate calculation of crystalline terahertz spectra

Terahertz vibrational spectroscopy has emerged as a powerful spectroscopic technique, providing valuable information regarding long-range interactions - and associated collective dynamics - occurring in solids. However, the terahertz sciences are relatively nascent, and there have been significant advances over the last several decades that have profoundly influenced the interpretation and assignment of experimental terahertz spectra. Specifically, because there do not exist any functional group or material-specific terahertz transitions, it is not possible to interpret experimental spectra without additional analysis, specifically, computational simulations. Over the years simulations utilizing periodic boundary conditions have proven to be most successful for reproducing experimental terahertz dynamics, due to the ability of the calculations to accurately take long-range forces into account. On the other hand, there are numerous reports in the literature that utilize gas phase cluster geometries, to varying levels of apparent success. This perspective will provide a concise introduction into the terahertz sciences, specifically terahertz spectroscopy, followed by an evaluation of gas phase and periodic simulations for the assignment of crystalline terahertz spectra, highlighting potential pitfalls and good practice for future endeavors.

Terahertz signatures and quantitative analysis of glucose anhydrate and monohydrate mixture

Glucose, as the main energy carrier and significant source of nutrition, generally comes in two available forms of anhydrate and monohydrate in commercial production. Considering their respective application occasions, proper identification of glucose in single composition or binary-mixture and quantification of the mixture are crucial in industry monitoring to guarantee merchandise quality. Simultaneously, public confusions of glucose are rather ubiquitous partly due to anhydrate and monohydrate with identical white crystalline appearance. In this paper, utilizing the molecular fingerprints of terahertz (THz) technology that are corresponding to structural characteristics of anhydrous and hydrated form, THz signatures of glucose anhydrate, monohydrate and their mixture, as well as THz spectral transformation from monohydrate to anhydrate with the dehydrating process are systematically studied. Some visible peaks of monohydrate were noted at 1.82 and 1.99 THz signifying the presence of hydrated structure. However, with the dehydrating process, the peaks related to the hydrated structure are not very apparent when the peaks at 1.44 and 2.08 THz appear due to changes in the molecular structure of anhydrate, which provide clear indication for hydrogen-bond network reconstruction at the micro level. Furthermore, characteristic peaks at 1.44 and 1.82 THz can be specified as the main quantitative indicators for quantitative detection. The linear relationships between the amplitudes of characteristic peaks and the percentage compositions of anhydrate and monohydrate are revealed. Three commercially available brands of edible glucose powder A, B, C were effectively identified by THz signatures. While powder C was recognized as binary-mixture and the proportion of anhydrate and monohydrate was further quantified. THz spectroscopy technology has advantages of direct recognition, simple quantitative model based on THz absorption peaks, and no need for complicated chemical treatment. It may be potentially shed light on industrial monitoring of glucose production and other related mixture in the future.

Molecular methylation detection based on terahertz metamaterial technology

Terahertz wave has a good ability to identify biomolecules due to its fingerprint spectrum characteristics. However, the minimum detectable limit of terahertz technology by the conventional tablet pressing method is on the order of milligrams, which cannot meet the application requirements of low concentration detection in the biomedical field-near or below micrograms. Here, we proposed a method to enhance the detection sensitivity by designing a metamaterial chip with the absorption-induced transparency (AIT) effect, which can enhance the interaction between terahertz waves and biomolecules and lower the detectable limit. Taking 7-methylguanine (7-MG) as an example, based on its terahertz characteristic absorption peak, we designed a split-ring resonator (SRR) metamaterial chip, which has the advantages of high sensitivity, unlabeled detection, fast response and simple measurement. Its quantitative detection limit can reach 6.30 μg, which is about 500 times smaller than that of the traditional tablet pressing method (2.95 mg). In addition, for methylated and unmethylated substances, the chip exhibits different frequency shifts, which also realizes the qualitative identification effectively. These results provide a reference for the rapid and accurate diagnosis of diseases associated with molecular methylation in clinical medicine.