Rare earth metals detection and recognition based on laser induced breakdown spectroscopy and machine learning.

The rapid detection and identification of the electronic waste (e-waste) containing rare earth (RE) elements is of great significance for the recycling of RE elements. However, the analysis of these materials is extremely challenging due to extreme similarities in appearance or chemical composition. In this research, a new system based on laser induced breakdown spectroscopy (LIBS) and machine learning algorithms is developed for identifying and classifying e-waste of rare-earth phosphors (REPs). Three different kinds of phosphors are selected and the spectra is monitored using this new developed system. The analysis of phosphor spectra shows that there are Gd, Yd, and Y RE element spectra in the phosphor. The results also verify that LIBS could be used to detect RE elements. An unsupervised learning method, principal component analysis (PCA), is used to distinguish the three phosphors and training data set is stored for further identification. Additionally, a supervised learning method, backpropagation artificial neural network (BP-ANN) algorithm is used to establish a neural network model to identify phosphors. The result show that the final phosphor recognition rate reaches 99.9%. The innovative system based on LIBS and machine learning (ML) has the potential to improve rapid in situ detection of RE elements for the classification of e-waste.

[Study on experiment of fluorescence spectra detection of pesticide residue of imidacloprid in apple juices].

The fluorescence properties of imidacloprid was studied based on the basic theory that organic molecules can emit fluorescence as they are excited by rays. The fluorescence spectra were obtained under the condition of different content of imidacloprid in apple juices and pure apple juices respectively through fluorescence spectrometer, and the relation between their fluorescence intensity and content of imidacloprid was analyzed. The experiment results show that the most intensive fluorescence (373 nm) was found in the spectrum of imidacloprid, while the fluorescence was not found in the pure apple juices with 234 nm as the excitation wavelength. Then the imidacloprid solution was added to the fruit juices increasingly. The best prediction model was obtained for the contend of imidacloprid in the apple juices, the coefficient of determination is 0.99674, and the accuracy is higher than 90%. As a result, it is fast and feasible to carry out the detection and analysis of the pesticide residue of imidacloprid in the apple juices.