Guangxi Normal University

Distinguishing the absorption spectra of isomers is a global challenge, and early methods of detection could not adequately meet the demand. Using infrared spectroscopy is rapid and simple, requiring low technical skills and is easy to perform on-demand tests, but it performs poorly in terms of sensitivity and accuracy. In contrast, molecular spectroscopy analysis offers robust performance but requires multi-step sample preparation, complex detections, long turnaround times, and a lab-based environment. Clearly, there is a need for an absorption spectroscopy detection method for isomers that is portable, requires low technical expertise, and can quickly provide samples to obtain results. This study conducted an in-depth analysis of the THz absorption spectra of dihydrouracil (DHU) and glycine anhydride (GAH) in the frequency range of 0.3-2.0 THz using Terahertz Time-Domain Spectroscopy (THz-TDS). Combine the experimental THz spectral data with theoretical calculation results. THz-TDS was used to obtain the THz absorption spectra of DHU and GAH, and theoretical calculations were performed using Density Functional Theory (DFT), specifically on the Gaussian 16 computational platform using the B3LYP functional and the 6-311G (d, p) basis set. To analyze the THz wave absorption characteristics of DHU and GAH, the potential energy distribution (PED) analysis method was employed to describe the vibrational modes of the absorption peaks, and the energy decomposition analysis based on forcefield (EDA-FF) was used to analyze the weak interaction energies between DHU and GAH. Theoretical contributions of characteristic absorption peaks of DHU and GAH were explained through Electrostatic Potential (ESP) and Van der Waals (vdW) potential distribution analyses. The electromagnetic properties of THz waves enable them to penetrate various materials while being highly sensitive to organic molecules. THz spectroscopy not only holds potential in studying weak molecular interactions but has also proven to be an effective method in identifying biomolecules with similar molecular structures. This study successfully distinguishes between the two isomers, DHU and GAH, providing an important theoretical and experimental basis for the in-depth exploration of other isomeric molecule designs and functions in the future.

This study examined how different bagging types (unbagged, mesh-bagged, and paper-bagged) affect the internal and external quality of fruits. Spectral images of 307 apples were collected using a visible-near infrared hyperspectral imaging system, and differences in color, size, firmness, soluble solids content (SSC), and aroma were analyzed. The effectiveness of various algorithms for extracting effective wavelengths was compared. Developed apple quality inspection models using various machine learning algorithms, achieving the best-performing model, CARS-MLR, with all indicators having an R²_p greater than 0.75. The results revealed significant differences in quality indicators based on bagging type, with paper-bagged apples showing the best overall quality-brighter color, moderate size and firmness, and rich aroma. This suggests that hyperspectral imaging, feature selection algorithms and machine learning methods, is an effective approach for non-destructive quality assessment of apples. This research offers valuable insights for assessing the quality of other fruits with different bagging types.

The abnormal fluctuations of glutathione (GSH) in vivo often reflect disease progression and are closely linked to human metabolism and physiological functions. Highly sensitive and selective detection of GSH is crucial for guiding early diagnosis and treatment; however, achieving this remains a significant challenge. In this study, we developed an enzyme activity sensor platform for the efficient detection of GSH. This platform utilizes Au@CuS core-shell materials loaded with CuO₂ nanoparticles to create a composite nanosensor system. Under slightly acidic conditions, CuO₂ on the nanomaterial's surface decomposes into H₂O₂ and Cu²⁺ ions. The generated H₂O₂ then reacts with tetramethylbenzidine (TMB) in the presence of peroxidase-like CuS to yield oxidized tetramethylbiphenyl (_OXTMB), which generates a distinctive Raman signal. Upon addition of GSH to the system, the unique _OXTMB signal diminishes due to GSH's strong antioxidant capacity and the consequent consumption of _OXTMB. This sensing method enables sensitive detection of GSH, with a detection limit as low as 1.2 × 10^-13 mol∙L^-1. This approach holds promise for providing researchers with rapid and precise in vitro analysis of GSH, serving as an indicator for early disease diagnosis and real-time evaluation of treatment efficacy.