Longjing tea is one of China’s protected geographical indication products with high commercial and nutritional value. The geographical origin of Longjing tea is an important factor influencing its commercial and nutritional value. Hyperspectral imaging systems covering the two spectral ranges of 380–1030 nm and 874–1734 nm were used to identify a single tea leaf of Longjing tea from six geographical origins. Principal component analysis (PCA) was conducted on hyperspectral images to form PCA score images. Differences among samples from different geographical origins were visually observed from the PCA score images. Support vector machine (SVM) and partial least squares discriminant analysis (PLS-DA) models were built using the full spectra at the two spectral ranges. Decent classification performances were obtained at the two spectral ranges, with the overall classification accuracy of the calibration and prediction sets over 84%. Furthermore, prediction maps for geographical origins identification of Longjing tea were obtained by applying the SVM models on the hyperspectral images. The overall results illustrate that hyperspectral imaging at both spectral ranges can be applied to identify the geographical origin of single tea leaves of Longjing tea. This study provides a new, rapid, and non-destructive alternative for Longjing tea geographical origins identification.

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The non-judicious use of pesticides in agro-food poses a severe threat to food safety and human health. As an emerging chromatographic fingerprint provider, surface-enhanced Raman spectroscopy analysis (SERS) sheds bright light on sensitive and nondestructive detection of pesticide residues. This research proposed a novel strategy to detect three-pesticide residues (thiabendazole, carbendazim, and chlorpyrifos) on tomato peel based on the flexible and sticky SERS substrate. After selecting the best commercial adhesive tape (3M9080), the SERS substrate was constructed by optimizing the parameters in the preparation process of AuNPs. Therefore, a new simple “tape-wrapped SERS” way for pesticide residue analysis was established with a simple procedure of “absorption, separation, and drop addition.” Based on chemometrics method, the limit of semiquantitative detection was 20, 36, and 80 ng/cm2 for thiabendazole, carbendazim, and chlorpyrifos, respectively, on tomato surface, which indicated that the proposed method could meet the requirement of actual application with a large prospect in agro-food safety detection.

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The promising prospect of a terahertz metasurface in sensing and detection applications has attracted increasing attention because of its ability to overcome the classical diffraction limit and the enhancement of field intensity. In this work, a novel scheme based on an all-silicon terahertz plasmon metasurface is proposed and experimentally demonstrated to be a highly sensitive biosensor for the Bacillus thuringiensis Cry1Ac toxin. The regression coefficients between Bacillus thuringiensis protein concentrations and the spectral resonance intensity and frequency were 0.8988 and 0.9238, respectively. The resonance amplitude variation and frequency shift of the metasurface were investigated in terms of both thickness and permittivity change of the analyte, which reflected the protein residue in the actual process. Moreover, the reliability and stability of the metasurface chip were verified by time period, temperature, and humidity control. These results promise the ability of the proposed metasurface chip as a Bacillus thuringiensis protein sensor with high sensitivity and stability. In addition, this novel device strategy provides opportunities for the advancement of terahertz functional applications in the fields of biochemical sensing and detection.