Journal of Applied Spectroscopy最新文献

We report the synthesis and characterization of Gd³⁺ activated LaCePO₄. The phosphors were synthesized by a modified solid-state reaction method with variable concentrations (0.5–2.5 mol.%) of doping ions of Gd³⁺. Analyses of the sample's structure have shown that it had a monoclinic structure with a single phase. Micro-crystal formation was seen using scanning electron microscopy (SEM) of particles ranging in size from ~100 nm to over 2 μm. FTIR confirmed the formation of LaCePO₄:Gd³⁺ phosphor. Phosphor samples with varying doping ion concentrations were also shown via photoluminescence analysis. LaCePO₄:Gd³⁺ phosphor emits intense near-UV-blue light by 275-nm excitation. The corresponding spectroscopic parameters were calculated using the CIE technique, and the coordinates (x = 0.17 and y = 0.20) were in the visible region. Based on the findings, phosphor produced in such a way might be used in laser applications. Thermoluminescence (TL) glow curve analysis for various UV exposure times (5–20 min) showed a good broad TL glow curve centered at 183°C. The broad TL glow curve was deconvoluted by the CGCD program, and the corresponding trap parameters were calculated.

Purplish red to pink spinel samples from Myanmar, India, and Tanzania (Mahenge and Tunduru mines) were analyzed using gemological tools, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, Raman spectroscopy, synchrotron X-ray absorption spectroscopy, and electron probe microanalyzer (EPMA). While gemological properties did not significantly differ across samples, chemical composition analysis by EPMA revealed distinct characteristics for source determination. Indian pink spinels contained relatively high manganese concentrations, and specific Cr₂O₃/Fe₂O₃ and ZnO/V₂O₅ ratios were characteristic of different sources. The ATR-FTIR spectra were consistent across sources, whereas the Raman spectra revealed variations in the Mg–O and Al–O bond peak ratios. X-ray absorption spectroscopy analysis confirmed the presence of Cr³⁺ in all the samples, with varying Fe²⁺ and Fe³⁺ states. By comparing spinels from Myanmar, India, and Tanzania, this comprehensive study enhances the understanding of regional variations in spinel characteristics, contributing to more accurate origin determination and market classification.

Raman spectroscopy combined with machine learning techniques is a promising approach for quantitative substance analysis. Online Raman spectrometers have intrinsic limits in sampling circumstances, preventing the utilization of surface-enhanced Raman scattering (SERS) approaches and therefore hindering high-precision predictions for low-concentration analytes. This paper introduces an innovative framework that integrates B-spline fitting for feature extraction with a least squares concentration prediction model, which is improved by hyperparameter optimization using a genetic algorithm (GA). The performance of this framework was carefully evaluated against four alternative GA-optimized prediction models: wavelet transform feature extraction with ridge regression, linear regression neural networks, standalone ridge regression, and polynomial fitting using least squares. Experimental validation included Raman spectral datasets obtained from boric acid and nitric acid solutions throughout 11 concentration gradients (0–500 mg/L) that were evenly dispersed within the designated range. A stratified data partitioning approach, which assigned six concentration levels to the test set, while leveraging the remaining five to create three separate training subsets (3, 4, and 5 concentration levels), was employed. A comparative investigation revealed that the B-spline–least-squares model achieved optimal prediction accuracy when it was trained on four concentration levels, resulting in a mean root-mean-square error (RMSE) of 5.83 mg/L for both analytes. The performance hierarchy revealed that the wavelet transform–ridge regression model (5-level training subset, RMSE = 6.02 mg/L) was the second-best method. Linear regression neural networks, ridge regression, and polynomial– least squares models achieved optimal performance with five training concentrations, yielding mean RMSE values of 7.35, 9.17, and 12.21 mg/L, respectively.

The local structure and electron paramagnetic resonance (EPR) parameters (g_i-factors and A_i-constants, i = ||, ⊥) of the tetragonal Cu²⁺ centers in sodium fluoride–sodium borate glasses (80Na₂B₄O₇–19NaF–CuO) are theoretically investigated using a high-order perturbation formula for the parameters of Cu²⁺ ions in tetragonally elongated octahedra. On the basis of the superposition model, relationships between the local structure and the EPR parameters are constructed. By comparing the calculated g-factors and A-constants with experimental data for the [CuO₆]^10– cluster, the local structure parameters of the Cu²⁺ centers were determined. The calculated bond lengths perpendicular and parallel to the C₄ axis were determined to be R_∥ ≈ 2.191 Å and R_⊥ ≈ 1.964 Å, respectively, as a result of the Jahn–Teller distortion effect. These findings are consistent with experimental observations, demonstrating the accuracy of our theoretical model and the validity of the Jahn–Teller effect in describing the structural characteristics of the Cu²⁺ centers in this system.

We introduce a spectral decomposition method by modifying the GMM (Gaussian mixture module) algorithm. The first key point is to circumvent the process of random data generation for less error; the second key point is to replace the Gaussian model with a bi-Gaussian model to overcome the limitations of conventional symmetric Gaussian approximations. Comparative analysis with the Levenberg–Marquardt algorithm and standard GMM approaches demonstrates the superior accuracy of our method, as evidenced by the minimization of spectral reconstruction errors across all tested wavelength regimes. The effectiveness of this decomposition method for chemical oxygen demand (COD) detection was assessed via a series of experiments with real samples of sewage from various plants. The analysis showed less root mean squared error (RMSE) value by using the B-band of the benzene ring after the procedure of decomposition in contrast to the methods of peak searching and fixed wavelengths. The proposed method can improve the environmental suitability of COD detection effectively.

A rare earth complex was synthesized using α-thiophenoyltrifluoroacetone and o-phenanthroline as ligands. The complex was characterized by thermogravimetric analysis, infrared spectra, elemental analysis, and X-ray powder diffraction. The fluorescence spectra showed that the complex produced the characteristic fluorescence emission of Eu³⁺ ions at 615 nm, highly overlapping with the absorption peak of malachite green to cause fluorescence quenching. Fluorescence lifetime confirmed that the quenching mechanism is a fluorescence resonance energy transfer at low concentration, and fluorescence resonance energy transfer and inner filter effect at high concentration. The complex could exclude the interference of other aquaculture fish drugs and has a specific selectivity for malachite green. Response time was within 1 min, and the linear range was 0.1–70 μmol/L. Detection limit was calculated to be 0.023 μmol/L (3σ/k, n = 9). Spiked recoveries of malachite green in water and fish were in the range of 89.2–98.6%, indicating that the complex could be used as a fluorescent probe for the detection of malachite green residues.

Ag/ZnO composite materials were prepared using a hydrothermal method based on the optimal experimental conditions for synthesizing ZnO materials. These composites were utilized in the photodegradation of simulated wastewater containing 50 mg/L ammonium nitrogen. The optimal composite ratio was determined through experimentation, and Ag/ZnO composites were characterized using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicated that the Ag/ZnO composites exhibit microstructural features similar to ZnO materials, characterized by flower-like morphologies composed of clustered porous sheets with high crystallinity. Compared to pure ZnO, the Ag/ZnO-5% composite demonstrated stronger absorption across the visible light spectrum and had a bandgap energy of approximately 3.17 eV. Additionally, the recombination rate of electron–hole pairs in Ag/ZnO composites was lower than that in ZnO. After a 30-min dark reaction, the composite material achieved a degradation efficiency of 71.11% for the 50 mg/L ammonium nitrogen-simulated wastewater under 250 W mercury lamp irradiation for 180 min.

A method for producing a coating with a reduced optical reflectivity based on nanoporous germanium layers by implantation of monocrystalline c-germanium with ²⁰⁹Bi⁺⁺ ions at an energy of E = 72 keV, current density J = μA/cm², and dose interval D = 1.3∙10¹⁵-2.5∙10¹⁶ ions/cm² is proposed. Starting from D = 6.2∙10¹⁵ ions/cm², a swollen spongy Bi:PGe layer is formed with thickness of about 100 nm. This layer, which does not undergo change in morphology with increasing D, consists of thin interwoven germanium nanowires. The layer has a low optical reflectivity (<3%) in the visible spectral range.

Changes in the phosphorescence intensity of acenaphthene in supercooled toluene during heating at a rate of 0.04 K/s at concentrations of 2∙10^–3 and 2∙10^–2 M are studied. It is shown that when the glass-transition temperature of toluene T_g = 117 K is reached, effective quenching of phosphorescence by oxygen begins for both solution concentrations. The intensity increases at T = 130 K because of the appearance of a crystalline phase. The values of these temperatures are the same for both concentrations. An “explosive” intensity increase is observed at T = 140 K for the solution of concentration 2∙10^–3 M because of self-acceleration of toluene crystallization. Such changes are not observed for the solution of concentration 2∙10^–2 M. Possible causes of the established changes in the phosphorescence intensity and the use of this effect to study structural changes in supercooled organic solvents are discussed.

Near-threshold spectra of Rydberg and autoionization states of the thallium atom have been studied by the method of selective stepwise photoionization of atoms with laser radiation. A so-called “transparency window” of width 25 ± 2 cm⁻¹, the center of which was 45 cm⁻¹ higher than the boundary of thallium atom ionization (E_i = 49,266.71 cm⁻¹), was found in the ionization continuum near the threshold. The formation of this window was evidently connected to the sharp and deep asymmetry of the previously discovered Beutler–Fano autoionization resonance having the configuration 6s6p^{2 4}P_3/2, situated 659 cm⁻¹ higher than the ionization boundary (E_0.5 = 49,925.70 cm⁻¹). The autoionization resonance contour had such a profile that Fano parameter (q) on the long-wavelength continuum side approached zero. This probably happened because of the strong interaction of the level with the continuum.