Laser-induced breakdown spectroscopy (LIBS) is a promising alternative to conventional methods in classifying citrus huanglongbing (HLB). Mature citrus fruits with similar features were picked and divided into healthy and HLB-asymptomatic groups. LIBS spectra and images were collected by focusing a laser on fresh fruit surfaces without sample preparation. The pH value and soluble solids content of juice as the indicators of acidity and sugar were detected, and the content of Ca, Zn, and K in peel and pulp was analyzed. The characteristic lines from LIBS spectra were extracted by continuous wavelet transform and principal component analysis (PCA). The t -test of these indicators displayed significant difference between the two groups. Fisher discriminant analysis and multilayer perception neural network (MLP) were applied to identify the disease. The classification accuracy reached 100% by PCA-MLP. The results show that LIBS can realize in situ detection of citrus HLB fruits.

This work provides a modified adaptive mutation probability selection genetic algorithm to optimize the SVM model, which improved the accuracy of tea sample classification by LIBS and its recognition accuracy was higher than CV-SVM and PSO-SVM.

The frequent occurrence of quality and safety incidents about agricultural products has intensified consumers' concerns. Since laser-induced breakdown spectroscopy (LIBS) is a promising, versatile atomic spectrum analysis technique for the...

To predict the nutrition and safety of agricultural products by laser-induced breakdown spectroscopy (LIBS), heavy metal Cd in rice was selected as an analytical target. Mature rice grain samples from 40 growing geographical areas around Poyang Lake were picked on-site and processed by grinding to obtain the edible rice. The content of Cd in rice samples was determined by graphite furnace atomic absorption spectrometry, and the rice pellets were detected by LIBS. The risk intake was estimated by the target hazard quotient and Chinese National Standard. Moreover, the samples were classified as clean, slight, and severe ones according to evaluation. The content of Cd was predicted by analyzing LIBS spectra coupled with the partial least square (PLS) model. The correlation coefficients ( R 2 ) reached 0.9036 and 0.9771 for the training and prediction sets, respectively, and the root mean square errors were 0.0487 and 0.027, respectively. It denotes that the PLS model has a higher prediction ability especially after LIBS spectra were processed by smoothing and multiplicative scatter correction. For the clean, slight, and severe rice samples, the LIBS intensity ratio between minerals Mg, K, Na, Si, and Mn to Ca was compared. The ratio was decreased in all samples as Cd stress increased. Correlation analysis results show that Mn displayed a highly significant negative correlation with Cd stress, while Mg, K, and Na displayed a significant negative correlation with Cd stress. The relationship between Si and Cd did not reach a significant level. This work indicated that it was feasible to use LIBS combined with a suitable data process to predict Cd content and the effect of Cd stress on minerals in rice. It is promising to evaluate the nutrition and safety of food products by analyzing LIBS spectra.

In biomedical engineering, optics, and photonics, fluorescent silkworm silk has many potential applications, but its complex preparation process and the environmental pollution of corresponding chemical dyeing methods hinder its development. Herein, we provide a green and effective method for fabricating fluorescent silkworm silk with enhanced mechanical properties. Citric acid and urea were selected as raw materials for synthesizing carbon dots (CDs), which were applied as additives of silkworm feed to produce fluorescent silkworm silks by microwave-assisted methods. The results showed that a diet of mulberry leaf with 0.5 wt% CDs was safe for silkworms and did not affect silk yield. CDs rapidly entered silkworms and accumulated in their blood and silk glands. After feeding for 90 min, the silk gland fluorescence appeared prominent. Compared with ordinary silk, the highest elongation at break of the CD-modified silk was 22.24%, and the breaking strength was 28.07 MPa, which were increases of 5.05 and 22.84%, respectively. The CD-modified silk displayed intrinsic blue fluorescence when exposed to a 405 nm laser, exhibited no cytotoxic effect on L929 cells and had excellent cell adhesion. The strategy proposed in this work is not only environmentally friendly but can also produce high-quality fluorescent silk on a large scale.