Journal of Applied Spectroscopy最新文献

To classify and detect the type and content of petroleum hydrocarbon contaminants in the soil surface layer, fluorescence spectrometry is commonly used. The experimental oils were selected from three common engine oils available in the market: Loxson L-CKC220 gear oil, APSIN 10W-40 engine oil and Jaguar 200 SF MA 15W-40 motorcycle oil. The fluorescence spectra of the oils were obtained using the fluorescence-induced technique, the spectral wavelengths were selected using a genetic algorithm (GA), and the detection models were constructed by combining RF (Random Forest), AdaBoost, and Gradient Enhanced Decision Tree (GBDT) regression algorithms for classification, identification, and concentration prediction analysis. The experimental results show that the average accuracy of classification and identification of gear oil, engine oil and motorcycle oil reach 83.9, 97.8, and 92.2%, respectively. Comparative analysis of the prediction results of the three concentration regression models shows that while all algorithms have high model prediction accuracy, GA combined with GBDT regression model has the best prediction performance for gear oils, engine oils and motorcycle oils, and improves the prediction accuracies by 62.7, 42.3, and 48.3% compared to the prediction accuracies of the wavelength selection without the use of GA, respectively. In summary, GA-based spectral wavelength selection combined with machine learning algorithms has high prediction accuracy and precision for the classification and prediction of motor oil contaminants in selected specific soils, and can be used as an effective detection method.

The influence of the architecture of NH₂-peripheral substitution of porphine derivatives on the intersystem T₁ → S₀-transition energy was studied theoretically. The molecular conformations of 15 porphine derivatives and 8 Zn-porphine derivatives in the ground singlet (S₀) and lowest triplet (T₁) states were optimized, the molecular orbital energies were determined, and the energies of the T₁ → S₀ transition were calculated using quantum chemical methods. The T₁ → S₀-transition energy was found to decrease from 11,700 to 6200 cm^–1 upon increasing the number of NH₂ groups in the macrocycle C_m-positions. The T₁ → S₀-transition energy was a linear function of the weighted sum of inductive and resonant Hammett constants 0.2σ_I + 0.8σ_R of the substituents. The ratio of inductive and resonant contributions of the NH₂ groups depended on the method of attachment to the macrocycle, with the contribution of resonant interactions decreasing with increasing spacer length. The main reason for the bathochromic shift of the T₁ → S₀ transition was a significant increase in the energy of the b₁-orbital, which had antinodes on the macrocycle C_m atoms. The dependence also held for Zn-porphyrins with the same peripheral substitution architecture. The energy of the T₁ → S₀ transition was noted to differ for both NH tautomers and conformers differing in the position of NH₂ groups relative to the macrocycle mean plane. The calculations showed that experimental studies of aminoporphyrins were promising for obtaining new phosphors in the IR spectral region. A method for predicting the T₁ → S₀-transition energy for the synthesis of compounds with the required spectral and luminescent characteristics was proposed based on the results.

The correct conditions for measuring the luminescence intensities in fi laments formed by the action of femtosecond laser pulses were found for lithium fluoride crystals. The determined conditions ensured that the measured intensities were proportional to the concentrations of luminescent color centers created in the crystals by the laser radiation and allowed conclusions to be drawn about the processes occurring in the filaments. Near-cluster color centers were found, indicating the presence of nanosized clusters in all areas of the fi laments.

The light pressure of an evanescent electromagnetic wave formed by total internal reflection near the flat interface of a dielectric and a liquid on a dielectric spherical nanoparticle located in a liquid medium is considered. Phase portraits of a two-dimensional system of equations that is equivalent to the equation of nanoparticle transportation under the influence of the force gradient of the light pressure of the evanescent field taking into account the medium resistance force are plotted. Various phase portraits can be realized both without equilibrium points and with one equilibrium point (stable focus, stable node or saddle) on the phase plane, depending on the parameters of the laser radiation and the material of the nanoparticle suspended in the water.

The spectral and bactericidal properties of a number of biodyes including bromophenol blue, amido black 10B, methyl thymol blue, basic fuchsin, chrome dark blue, eosin, indigo dye, and bromophenol red have been characterized. The inclusion of eosin, bromophenol red, indigo, and rifampicin into the internal space of phospholipid nanocontainers was shown to lead to leveling of the characteristic absorption maxima in the visible and ultraviolet regions of the spectra of these compounds taken in aqueous solution. This effect allows visual and spectrophotometric monitoring of the prodrug incorporation into liposomes. The construction of a number of supramolecular forms of prodrugs, which are micelles and liposomes derived from modifications of the bactericidal nucleoside brivudine in various combinations, showed the feasibility of using indigo as a dye marker. This permits the identification of liposomes formed from an equimolar mixture of dimyristoylphosphatidylbrivudine lipoconjugate with dimyristoylphosphatidylcholine as a potential prodrug formulation that most effectively inhibits the growth of Staphylococcus aureus cells.

Plants play an important role in nanoparticle preparation because they are easily accessible, environmentally friendly, and inexpensive. In this study, we used an ethanolic extract of Mangifera indica seed as a reducing and stabilising agent to create zinc oxide (ZnO) nanoparticles (NPs). The ZnO NPs were examined using characterization techniques such as UV-Vis, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The interaction of phytochemical constituents from plant extracts providing the biological reduction of zinc metal ions to ZnO had been identified by the UV-visible absorption studies. According to the FT-IR results, metal oxides exhibited interatomic vibration-driven absorption in the fingerprint area below 1000 cm^–1. Particles appeared to be crystalline and also a rice-grain shape of ZnO NPs was confirmed by XRD, SEM, and TEM, respectively. In addition, the cytotoxic effect of ZnO NPs was checked using the SKMEL-28 cell line, showing an IC50 value of 32.686 μg/mL in the SKMEL-28 cell line, and 49.011 μg/mL in the typical L6 cell line. Furthermore, the synthesized NPs were subjected to (AO/EB) double staining approach to examine the apoptotic activity. The acridine orange/ethidium bromide method made strong evidence for demonstrating chromatin condensation and membrane blebbing.

One of the inherent limitations associated with laser-induced breakdown spectroscopy (LIBS) in the identification of elements lies in the strength of the emission signals. Several approaches exist to enhance the emission capacity of LIBS. In this particular investigation, our focus was on amplifying the signal intensity of LIBS through the utilization of two techniques. These techniques include the application of a low-power electric field within the zone where plasma is formed, in conjunction with the utilization of nanoparticles on the surface of the sample. Specifically, our analysis involved the examination of samples consisting of metallic Zn powder as the matrix element, with the incorporation of small quantities of Ca in the form of CaCO₃. The combination of these two methods resulted in unprecedented outcomes, demonstrating a 3.5-fold increase in samples containing 0.05% w/w of CaCO₃ when subjected to an electric field of 60 V/cm, while bearing nanoparticles on their surface.

Spectroscopic studies of Ho³⁺-doped SrF₂ crystals were performed regarding applications in solid-state lasers. The crystal structure of the Ho:SrF₂ crystal was investigated using single-crystal X-ray diffraction. SrF₂ exists as a cubic structure with an Fm3m space group. A Raman shift of 288 cm^–1 was observed for the Ho:SrF₂ single crystal. SrF₂ hosts with low-frequency vibrational modes are suitable for reducing nonradiative emissions while maximizing radiative emissions. The absorption spectrum was recorded in the visible region from 400 to 800 nm, yielding absorption lines at 416, 450, 468, 473, 484, 536, 638, and 643 nm. The fluorescence spectrum recorded at an excitation wavelength of 450 nm shows two emission bands at 546 and 656 nm, which correspond to green and red emission, respectively. The intensity parameters Ω_λ (λ = 2, 4, and 6) were estimated using the Judd–Ofelt theory. For Ho:SrF₂ single crystal, the calculated Ω_λ are Ω₂ = 0.14 × 10–20 cm², Ω₄ = 3.14 × 10^–20 cm², and Ω₆ = 3.74 × 10^–20 cm². The radiative transition probabilities, radiative lifetimes, and branching ratios β_R for Ho:SrF₂ were determined using the Judd–Ofelt parameters. The ⁵S₂ + ⁵F₄ → ⁵I₈ transition is more effective for population-building processes because of its lifetime (0.26 ms) and higher branching ratios (~82.86%). Ho:SrF₂ is, therefore, a promising solid-state laser crystal for green and red spectral regions.

A process for creating a macroporous silicon substrate on which a layer of titanium dioxide was deposited using the atomic-layer deposition method is described. Electrochemical etching was used to form the macroporous structure of the substrate. TiO₂ was deposited using an SI PEALD setup. The morphology, structure, and optical properties of the deposited TiO₂ film were assessed using scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy, spectral ellipsometry in the range 240–1000 nm, and Raman spectroscopy. Raman spectra revealed peaks at 144, 194, 397, and 639 cm^–1 that were characteristic of the TiO₂ anatase modification. The absorption coefficient and optical band gap width of the deposited film were determined based on the calculated ellipsometric parameters.

Remote detection of trace explosives and hazardous chemicals has been an ongoing challenge and a critical issue in defense science, public safety, and counterterrorism. Raman spectroscopy, a form of inelastic scattering, acts as a "fingerprint" analysis method for substance identification with high confidence in the detection of chemicals based on their vibrational modes. Here, we present a portable stand-off time-gated Raman spectroscopy, which consists of a passive Q-switched pulsed laser, a designed gated ICMOS, a spectrometer, and a telescope, with an overall size of 476.5 × 321.5 × 219.3 mm and a weight of 23.2 kg, which is much more compact and portable than reported previously. To confirm the effectiveness of the designed portable time-gated Raman spectroscopy, detections at different working distances and various amounts of substances are carried out. High levels of Raman identification are acquired even for 0.1 mg at a 10-m distance. Furthermore, we simulate realistic encounters in a possible war-zone scenario by testing the system's ability to recognize urea samples on different substrates such as an aluminum plate, woodblock, cardboard, black cloth, and leaf; good characteristic recognition is shown.