In situ rapid classification of rock lithology is crucial in various fields, including geological exploration and petroleum logging. Laser-induced breakdown spectroscopy (LIBS) is particularly well-suited for in situ online analysis due to its rapid response time and minimal sample preparation requirements. To facilitate in situ raw rock discrimination analysis, a portable LIBS device was developed specifically for outdoor use. This device built upon a previous multi-directional optimization scheme and integrated machine learning to classify seven types of original rock samples: mudstone, basalt, dolomite, sandstone, conglomerate, gypsolyte, and shale from oil logging sites. Initially, spectral data were collected from random areas of each rock sample, and a series of pre-processing steps and data dimensionality reduction were performed to enhance the accuracy and efficiency of the LIBS device. Subsequently, four classification algorithms—linear discriminant analysis (LDA), K-nearest neighbor (KNN), support vector machine (SVM), and extreme gradient boosting (XGBoost)—were employed for classification discrimination. The results were evaluated using a confusion matrix. The final average classification accuracies achieved were 95.71%, 93.57%, 92.14%, and 98.57%, respectively. This work not only demonstrates the effectiveness of the portable LIBS device in classifying various original rock types, but it also highlights the potential of the XGBoost algorithm in improving LIBS analytical performance in field scenarios and geological applications, such as oil logging sites.

In this study, the plasmon-enhanced high-order harmonic generation (HHG) of H-terminated finite-sized armchair single-walled carbon nanotubes (SWCNTs) near Ag nanoparticles is investigated systematically. Multiscale methods that combine the real-time time-dependent Hartree–Fock (TDHF) approach at the semi-empirical intermediate neglected differential overlap (INDOS) Hamiltonian level for molecular electronic dynamics with the finite-difference time-domain (FDTD) and solving Maxwell’s equations are used. It is found that for intact CNTs, HHG is significantly enhanced due to plasmon resonance. However, the nonlinear optical properties are saturated when the tube length increases enough in the inhomogeneous near-field. For long CNTs, the large gradient of a near-field is unfavorable for the nonlinear excitation of electrons. But defects can further change the properties of the spectra. The HHG of hybrid systems can be enhanced very clearly by introducing vacancy defects in CNTs. This enhancement is affected by the energy and intensity of the incident light, the near-field gradient, and the number and location of defects.

The transport mechanisms of several finite-sized, graphene nanoribbon-based junctions have been computationally investigated using density functional theory and Green's functional method.

In this paper, the structural and electronic properties of P/SnBr₂ heterojunctions were investigated using the first-principles calculation method based on the density functional theory (DFT). The band alignment of the P/SnBr₂ heterojunction was type I. The bandgap value was 0.71 eV in the DFT calculation. Furthermore, the bandgap of the heterojunction could be efficiently tuned by controlling an electric field and biaxial strain. The bandgap changed linearly with the electric field in a certain range; when the electric field was greater than 0.8 V/Å, the heterojunction was metallic. The bandgap could also be tuned when a biaxial strain was applied. Under tensile or compressive stress, significant effects such as the band alignment shift from type I to type III, and the transition from indirect to direct bandgap occurred. In conclusion, these research findings provide theoretical guidance for designing new heterojunctions based on SnBr₂.

The optical properties of hybrid systems composed of silver nanoparticles (NPs) and azobenzene molecules were systematically investigated by combining the real-time time-dependent density functional theory (RT-TDDFT) approach with the classical electrodynamics finite difference time domain (FDTD) technique for the solution of Maxwell’s equations. In order to reflect the chemical interaction between azobenzene and metal more exactly, except for adsorbed molecules, a Ag cluster separated from NP was also dealt, using RT-TDDFT. We studied the different factors affecting the surface-enhanced absorption spectra. It was found that the electric field amplified by plasmon resonance of Ag NPs can have an overall enhancement to the molecular light absorption throughout the whole energy range. The resonance between the electron and the plasmon excitation results in a larger percentage of enhancement in the absorption spectrum the closer the resonance peak is. The enhancement ratio of the resonance peak is the largest. The plasmon–exciton coupling and the optical properties of different isolate isomers influence the line shape of the absorption spectra. The dipole interaction and electronic transfer between azobenzene molecules and Ag NPs also change the shape of spectroscopy from the absorption enhancement ratio and the location of the peak. Physical and chemical factors lead to photoswitching in these hybrid systems together.

First-principles calculations based on density functional theory (DFT) were carried out to investigate four 25 at.% graphitic N-doped graphene/black phosphorene heterostructures constructed by substituting N atoms at four different sites in the graphene layer. The four models have the same C ₁₂ N ₄ P ₁₂ composition and doping concentration, allowing the influence of the N doping site and the resulting local interfacial environment to be compared directly. After relaxation, all configurations preserve layered van der Waals structures and show metallic or quasi-metallic features near the Fermi level. Density-of-states analysis indicates that the low-energy states are mainly contributed by P-p orbitals, while charge-density-difference results reveal electron transfer from the N-doped graphene layer to the phosphorene layer. The calculated work functions of CPN-1, CPN-2, CPN-3, and CPN-4 are 4.194, 4.214, 4.716, and 4.636 eV, showing clear dependence on the N doping site, respectively. The optical spectra exhibit similar overall profiles but retain pronounced in-plane anisotropy at low photon energies. These results indicate that the N substitution site in graphene is an effective factor for tuning the electronic and optical responses of doped two-dimensional heterostructures.