Journal of Applied Spectroscopy最新文献

A series of MnFe_2–xYb_xO₄ powder nanoparticles (for x = 0, 0.025, 0.075, 0.1, and 0.2) of different crystallite sizes were synthesised using the co-precipitation method. The effect of Yb³⁺ dopant on the properties of manganese ferrite was characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman measurements, and photoluminescence spectroscopy (PL). The crystallite size and density of the samples have a cubic structure with an Fd3m space group. Their sizes and densities were found to be in the range of 24.8–34.7 nm and 5.07–5.49 g/cm³. FT-IR analysis indicates the presence of two absorption bands in the range 400–600 cm^–1, which is a fingerprint region of ferrites. The v₂ band (Fe–O stretching mode of the octahedral site) shifts towards the lower wavenumber, which confirms the occupancy of larger-size Yb³⁺ ions at the octahedral site. The Raman peaks were noted at 228, 295, 405, 502, and 634 cm^–1 for undoped manganese ferrite. Based on Raman observations, it has been observed that Mn²⁺ ions exhibit a preference for occupying octahedral (B) sites by substituting Fe³⁺ ions. Additionally, rare earth ions have been preferentially observed to occupy octahedral sites. The primary cause for the displacement of Raman bands was ascribed predominantly to the greater radii of rare earth ions in comparison with Fe³⁺ and Mn²⁺ ions, and the shifting of the peaks indicates the presence of Yb³⁺ at the octahedral site. The PL spectrum shows emission at 560 nm with a rise in intensity with an increase in dopant Yb³⁺, which could be because of the incorporation of Yb³⁺ in the spinel structure, leading to radiative recombination in the yellow region of the electromagnetic spectrum.

The α-nBACoPc/SnO₂ composites were prepared using the in situ synthesis method and characterized by Fourier transform infrared (FT-IR), X-ray powder diff raction (XRD), X-ray photoelectron spectroscopy (XPS), and confirmed by the loading of amino cobalt phthalocyanine on SnO₂. Conduct photocatalytic degradation experiments used rhodamine B as a simulated pollutant. The composite exhibited a photo-catalytic degradation rate of 83.3%, which was higher than that of α-nBACoPc and SnO₂ alone. The Co–O bond in the composite material enhances the transfer of electrons from phthalocyanine to the SnO₂ conduction band, improving light utilization and strengthening the synergistic impact of cobalt phthalocyanine and SnO₂. Furthermore, the composites demonstrated good stability and recyclability.

The influence of interatomic collisions in a gaseous medium on intra-Doppler resonances of absorption of optical radiation in a thin gas cell was theoretically studied and could be recorded by recently developed laser spectroscopy methods. The limitations on the pressure of the gaseous medium at which the influence of such collisions on the width of these resonances was insignificant were determined. The results could find application in ultra-high resolution atomic spectroscopy and in compact optical frequency standards based on the thin gas cells under consideration.

The transmittance, reflectivity, and photoluminescence in the range 0.8–1.7 eV at 300 K and 77 K in the spectral range 0.6–6.0 eV at 300 K of thin films of CdTe synthesized on different substrates by thermal evaporation in a quasi-closed volume were studied. A strong dependence of the intensity and position of the band–band and excitonic luminescence bands on the substrate quality was discovered. The excitonic luminescence bands of films on silicon and glass were shifted by 10 meV to the short-wavelength region because of internal stresses in the films owing to the mismatch between the unit-cell parameters of the substrate and film. The transparency region of films cleaved from glass shifted to the longwavelength region because of the density tails of electronic states in the band gap caused by disordering of the films and the longer wavelength of the light than the roughness of the films on the growth and nucleation side. The best structural perfection was characteristic of films on a CdTe substrate based on the obtained dependences of the intensity and spectral position of the photoluminescence lines.

The effect of irradiation with different doses of 4-MeV electrons on radiative recombination of nonequilibrium charge carriers in Cu(In,Ga)(S,Se)₂ thin films of solar cells was studied. Near-edge photoluminescence (PL) in the energy range ~0.9–1.2 eV in nonirradiated and irradiated direct-gap Cu(In,Ga)(S,Se)₂ solid solutions was caused by optical interband transitions and radiative recombination through energy levels of acceptor- and donor-type structure defects in the presence of strong potential fluctuations. PL spectra measured in the temperature range 5–300 K exhibited energy shifts of the near-edge PL band maxima and redistributions of their intensities in thin films after irradiation with different doses of electrons. The activation energies of nonradiative recombination were determined from the quenching of PL band intensities. The possible nature of structural defects in nonirradiated and electron-irradiated Cu(In,Ga)(S,Se)₂ solid solutions was discussed.

Quantum chemical modeling using the Hartree–Fock theory level HF-3c/MINIS/MINIS11 (d)(Cl)/def2-SV(P) ECP(Pt) considering intermolecular interaction within the ORCA 5.03 software package was employed to study the electronic structure and binding energy of cisplatin, quinine, and fullerenol adducts and their three-component systems. Analysis of the total energies of the systems and the calculated energy diagrams of the highest occupied and lowest unoccupied molecular orbitals for the initial components and the molecular ensembles formed by them indicated the probable stability of their combinations. The synergistic effects were examined and the prospects for using the three-component cisplatin–quinine–fullerenol C₆₀(OH)₂₄ system in cancer chemotherapy were discussed.

The temperature dependences of emission-band positions of the LED heterostructure and the phosphor of white LED lamps were determined to be linear or quasilinear with temperature coefficients K₁ = –0.38 meV/K, K₂ = 0.147 meV/K, and K₃ = 0.27 meV/K for the bands at 2.7, 2.4, and 2.05 eV, respectively. Overheating of the heterostructure active regions during the test time was estimated using data from the spectral measurements. The estimates were compared with the results of direct temperature measurements. The temperature increased by ~20°C during the test time, which was less than the temperature increase of the electronic subsystem (~50°C), in agreement with literature data obtained for other types of LEDs. The main reason for the change in color temperature of the lamp radiation during operation was thermal quenching of luminescence in the phosphor material.

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.