Journal of Applied Spectroscopy最新文献

The effect of sequential formation of protonated and deprotonated forms of 2,3,7,13,17,18-hexamethyl-8,12-di-n-butylcorrole in solution on their photophysical characteristics and spectral-luminescent properties was studied. The spectral characteristics of each of the two forms in the ground electronic state were found to be the same when they formed from the free base and from the antipodal form, while the fluorescence spectra of the two forms differed depending on the method of formation. Based on an analysis of spectral shifts in fluorescence spectra and fluorescence quantum yields, it was concluded that the protonated and deprotonated forms of corroles underwent specific interactions in the lower excited singlet S₁ state due to the formation of a complex solvation shell. These specific interactions were shown to lead to hysteresis of the fluorescence characteristics of the protonated and deprotonated forms of corroles with their mutual transitions caused by (cyclic) changes in the acid–base equilibrium.

A fast and simple method for the synthesis of solid solutions based on erbium-doped yttrium oxide (Y_1–xEr_x)₂O₃ was developed. The crystal structures of the samples were determined by x-ray diffraction methods. The compounds exhibited greenish-yellow upconversion emission upon IR laser excitation (980 nm). An increase in the erbium concentration in (Y_1–xEr_x)₂O₃ caused a color change and a growth in the intensity of the upconversion luminescence. The maximum upconversion luminescence intensity was observed for the oxide with x = 0.05. A two-photon excitation mechanism was determined based on the dependence of the emission line intensities associated with ²H_11/2/⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions on the pumping power. The absolute and relative sensitivities were calculated from the temperature dependences of the ratio of emission lines corresponding to transitions from thermally coupled excited ²H_11/2 and ⁴S_3/2 levels and showed the promise of the oxides as materials for noncontact temperature sensing.

Hydrocortisone is a glucocorticoid-type hormone produced naturally by the organism, such that it maintains the body functional during physical or mental stress episodes. The present work focuses on the UV-Vis spectrophotometric assessment of the chemical stability of hydrocortisone in an aqueous medium during the time of analysis, determination of its acidity constants through a robust methodology that involves the usage of SQUAD software and validation of an analytical method to determine hydrocortisone by means of UV-Vis spectrophotometry, in pharmaceuticals. The acidity constant was determined as pK_a 11.45 ± 0.02 (298 K), and the molar absorptivity coefficients and the molar absorptivity coefficients of the species involved in this acidity equilibrium were also determined as a function of the wavelength. The analytical method developed attained detection and quantification limits of 386 ± 3 and 1280 ± 10 nM, respectively, whereas the validation allows reliable quantification of hydrocortisone in pharmaceuticals.

Different manufacturers do not produce the same quality of children’s Ca–Fe–Zn oral liquid due to different production materials and processes. To improve the phenomenon of counterfeit and imitation oral liquid on the market and effectively monitor its quality, laser-induced breakdown spectroscopy (LIBS) fingerprinting with sample preparation methods can provide a tool for real-time and rapid detection of oral liquids. The sample preparation methods include filter paper adsorption (FPA), filter paper adsorption with elemental Cu (FPA with Cu), adding dropwise to glass slides (ADS), adding dropwise to glass slides with elemental Cu (ADS with Cu), and gel preparation (GP). This work collected LIBS spectrum of oral liquids from eight manufacturers. The model for eXtreme Gradient Boosting (XGBoost) was constructed for classifying oral liquids based on five sample preparation methods. The accuracy was 91.25, 94.17, 55.42, 91.25, and 91.29%, respectively. The results show that the FPA method is more straightforward, efficient, and less affected by the specificity of the color of the sample. Both ADS and GP are susceptible to the color characteristics of the sample and are not well suited to the direct detection of transparent liquids. This work demonstrated that oral liquids could be discriminated by analyzing LIBS spectrum combined with the XGBoost model. Additionally, sample preparation, like the simple FPA method, can improve the accuracy of LIBS classification.

The Cu(II) was found using a quick and uncomplicated procedure that involved reacting it with a freshly synthesized ligand to create an orange complex that had an absorbance peak of 481.5 nm in an acidic solution. The best conditions for the formation of the complex were studied from the concentration of the ligand, medium, the effect of the addition sequence, the effect of temperature, and the time of complex formation. The results obtained are scatter plot extending from 0.1–9 ppm and a linear range from 0.1–7 ppm. Relative standard deviation (RSD%) for n = 8 is less than 0.5, recovery % (R%) within acceptable values, correlation coefficient (r) equal 0.9986, coefficient of determination (r²) equal to 0.9973, and percentage capital R-squared explained variation as a percentage/total variation (R²%) equal to 99.73. The method has been successfully applied for the estimation of Cu(II) ions without the influence of other interfering ions, and it can be applied to estimate Cu(II) in any sample.

We investigated the feasibility of using surface-enhanced Raman scattering (SERS) technology combined with the AdaBoost algorithm to rapidly discriminate cervical cancer patients from hysteromyoma patients. Using Au colloids as the SERS active substrate, we recorded Raman signal measurements on serum RNA samples obtained from 35 patients diagnosed with cervical cancer and 30 patients diagnosed with hysteromyoma. Analysis of RNA SERS spectra using principal component analysis, then three principal components (PC2, PC11, and PC24) with significant differences were chosen using the independent samples t-test (p < 0.05). The distinctive peak intensities of the relevant substance, measured at 448, 519, 698, 1003, and 1076 cm^–1, were found to be correlated with the substance’s alterations during the carcinogenesis process. The ideal AdaBoost classification model was developed by fi ne-tuning its parameters. The model showcased an impressive accuracy of 96.92%, exhibiting a high sensitivity of 94.28% and an exceptional specificity of 100%, as reported in the results. Compared to the linear discriminant analysis, support vector machine models, the effectiveness of classification greatly improved. The current findings indicate that serum SERS technology, combined with the AdaBoost algorithm, is anticipated to be developed into a potent screening tool for cervical cancer.

Employment of an external magnetic field on a frequency-chirped cos² laser pulse envelope for effective electron acceleration is studied. After the electron interacts with the laser pulse, the frequency chirp influences the electron dynamics, betatron resonance, and energy gain of the electron, ensuring effective acceleration of the electron with significant energy gain in the order of GeV. If a suitable external magnetic field is applied, an electron can gain energy and retain the same energy significantly. In this research, we employed the cos² laser pulse envelope to examine the impact of the laser pulse envelope on the investigation of electron acceleration in a vacuum. The front of the tested envelopes had received an axial injection of electrons. In all calculations, it is assumed that the front end of each pulse met the electron at time t = 0 at the position of origin. The relativistic Newton–Lorentz equations of electron motion in the field of the laser pulse have been solved analytically and numerically.

The synthesis and luminescence analysis of Tb³⁺-activated phosphors were reported. Y₂SiO₅ phosphors were synthesized by a modified solid-state reaction method with a variable doping concentration of Tb³⁺ ion (0.5–2.5 mol.%). As synthesized, the phosphors were characterized by X-ray diffraction (XRD) analysis. The XRD pattern confirmed the monoclinic structure of the prepared phosphor. Scanning electron microscopy and High-Resolution Transmission Electron Microscopy (HRTEM) studies revealed nearly uniform particle size distribution in the prepared phosphors. The photoluminescence excitation spectra of the Y₂SiO₅:Tb³⁺ (0.5–2.5 mol.%) phosphor displayed one broad, intense peak at 258–277 nm. When excited at the 258 nm wavelength, the phosphors showed emission peaks at 553 nm (⁵D₄ → ⁷F₅), 544 nm (⁵D₄ → ⁷F₅) and 489 nm (⁵D₄ → ⁷F₆). The 1931 CIE (x,y) chromaticity coordinates showed the distribution of the spectral region calculated from the photoluminescence emission spectra. The values of x = 0.25 and y = 0.46 were very close to light green emission. Therefore, the prepared phosphor is very useful for light-emitting diode (green component) applications.

Focusing on the problem of unclear ray-traced spots and their distribution rules in the design process of the Herriott cell, first, the characteristics of long-optical-path gas absorption cells were analyzed, and the calculation method of basic cavity length and the effective optical path of Herriott gas absorber cells were studied. Second, according to the transmission characteristics of geometric optics, a physical model of light transmission in Herriott cells was established via the LightTools software. Finally, simulation analysis was performed on Herriott cells with 5- and 14.4-m optical paths separately, determining the quantitative relationship between d/f and the number of spots reflected on the concave mirror, and optimizing the effective optical path and output laser energy of the Herriott cells. Through research analysis, the sizes and distribution positions of concave mirror spots in the Herriott cells were identified, as well as the factors affecting the number of reflections. It was also found that the number of reflected spots gradually decreases as d/f increases, revealing the light-tracing results and its spot distribution rule on the mirror surface, as well as verifying the accuracy of the theory. The findings of this study provide a basis for the optical path system design and optimization for Herriott cells with different optical path lengths.

The extended cavity diode lasers were stabilized using the first and third derivatives obtained by the frequency modulation method from the hyperfine resonances of the ⁸⁷Rb D₂ transition line. The frequency stability values were measured as 3.1 × 10^-12, 5.6 × 10^-13, and 1.9 × 10^-12 for integration times of 1, 10², and 10⁴ s, respectively, using the first derivatives of F=1 → F′=1 and F=1 → F′=2 resonances. By use of the third derivatives of F=2 → F′=1,3 and F=2 → F′=2,3 cross-over resonances, 4.0 × 10^-12 − 1 s, 5.7 × 10^-13 − 10² s, 9.3 × 10^-13 − 10⁴ s frequency stability values were obtained. These values compared with the results of the previous study obtained by the Zeeman modulation method.