Journal of Applied Spectroscopy最新文献

The electronic and optical properties of the LiV₃O₈ compound have been investigated using first-principles simulations within the density functional theory (DFT) framework. This promising material could be advantageous for battery applications. To better describe its semiconducting character, the Hubbard U correction combined with the generalized gradient approximation (GGA) was employed. Furthermore, the GGA+U approach provides an effective description of the electronic structure arising from the strong localization of 3d electrons in transition metals such as vanadium. The electronic structure results revealed that LiV₃O₈ exhibits a semiconducting behavior with a band gap located in the visible spectrum. Additionally, the optoelectronic properties of LiV₃O₈, including the optical absorption and reflectivity spectra, were computed, revealing an optical anisotropy in the low-energy range up to 12.5 eV. The optical absorption results further illustrated that the threshold light absorption occurs in the visible region, indicating potential applications in optoelectronic devices.

This study aims to develop and validate UV-spectrophotometric techniques for the accurate and reproducible quantification of Flavokawain A in both bulk and in house tablet formulations. The methods include zero-order spectrophotometry (Method I), zero-order area under the curve (AUC) spectrophotometry (Method II), firstorder derivative spectrophotometry (Method III), and first-order derivative AUC spectrophotometry (Method IV). Validation was performed following the International Council for Harmonisation (ICH) guidelines, evaluating parameters such as linearity, accuracy, precision, sensitivity, and robustness. Flavokawain A shows maximum absorbances at 362.80 nm. All methods exhibited excellent linearity over the concentration range of 1–7 μg/mL, with correlation coefficients (R²) exceeding 0.999. The LOD and LOQ values ranged from 0.07 to 0.08 μg/mL and 0.22 to 0.25 μg/mL, respectively, indicating high sensitivity. Precision studies yielded %RSD values below 2.0 across all methods, confirming reproducibility. Accuracy was validated through recovery studies, with mean recoveries ranging from 98.1 to 101.0%. In-house tablet analysis demonstrated the applicability of all methods for routine quality control, with % amount found between 99.7 and 101.8%. Overall, the developed UV spectrophotometric methods are simple, accurate, and precise, making them suitable for the routine quantification of Flavokawain A in pharmaceutical preparations and plant-based matrices.

The formation of silver nanoparticles (AgNPs) as byproducts during the synthesis of silver nanowires (AgNWs) necessitates accurate quantification of their relative abundances for evaluating practical applications. This study introduces a rapid quantitative approach based on UV-Vis spectral peak deconvolution. By modulating the molecular weight (MW) of polyvinylpyrrolidone (PVP), effective control over the diameter and yield of AgNWs was realized. Experimental results show that low-MW PVP (24 kDa) promotes the formation of short nanorods, intermediate-MW PVP (220 kDa) maximizes the aspect ratio to 370, and high-MW PVP (1300 kDa) reduces it to 310 due to steric hindrance. A novel mixed PVP system (1300 kDa:24 kDa = 2:1) significantly optimizes the nanowire morphology, yielding AgNWs with an aspect ratio of 920. However, competitive adsorption kinetics in this system resulted in a minimum AgNW/AgNP ratio of 0.90. A quantitative model correlating the average diameter of AgNWs with their characteristic UV-Vis absorption peak (370–400 nm) was established, enabling rapid diameter estimation through spectral analysis. Gaussian-Lorentzian hybrid functions were used to deconvolute the plasmon resonance peaks of AgNWs (370–400 nm) and AgNPs (450–500 nm), with the ratio of their peak areas employed to determine the proportion of wire-like products. This method shows strong agreement with SEM statistical results (Pearson coefficient = 0.84, R² = 0.75). Without requiring complex separation or machine learning, our approach enables rapid determination of AgNW diameters and yields through UV-Vis spectral deconvolution, providing an efficient and cost-effective solution for optimizing industrial synthesis and quality control.

Characteristics of a developed electric-discharge exciplex XeCl laser featuring a modular pumping system and using a bipolar charging voltage were studied. The pumping system consisted of three pairs of modules connected to a common load, i.e., the laser interelectrode discharge gap. It was shown that the modular transverse discharge excitation system allowed the operating voltage to be reduced to 36 kV with a discharge gap of 7 cm, the duration of the discharge-current pulse to be shortened, and the pumping power of the active medium and the energy input into it to be increased. The laser generation characteristics were studied as a function of the active medium composition and its excitation conditions. A laser output energy of ~3 J was achieved using a working mixture of composition HCl:Xe:Ne = 1:15:3000 under the pressure of 4 atm at a charging voltage of 36 kV. The laser generation pulse length was ~120 ns at half-height.

Functionalized silicon quantum dots (Si-CQDs) were prepared using a hydrothermal method, and the effect of Si-CQDs on vitamin B6 was investigated. Fluorescence characteristics of the Si-CQDs were studied, and the fluorescence intensity of the Si-CQDs exhibited good linearity within the range of different concentrations of vitamin B6, with a regression equation of F/F₀ = 15.3x + 0.91149 (R² = 0.99652). The recovery rate was 94.21% in the spiked recovery experiments, indicating the high sensitivity and selectivity of the Si-CQDs.

Silver nanoparticles (Ag NPs) were synthesized by using the extract of almond kernels as a natural reducing and stabilizing agent. The synthesized Ag NPs were characterized by UV-Vis spectrophotometer, FTIR spectroscopy, XRD characterization, and TEM imaging. As a result, every technique showed that the particle size of Ag NPs was 18–23 nm. It also showed that the synthesized Ag NPs exhibited a moderate cytotoxic effect on normal human fibroblast cell line (BJ1), IC₅₀ was 98.4 μg/mL. According to quantitative PCR (qPCR) data, which evaluate the expression of two virulence-related genes, ALS3 and HWP1, in Candida albicans, it was shown that the synthesized Ag NPs suppresses the expression of the main virulence genes of Candida albicans more effectively (1.5 times for ALS3 and 1.2 times for HWP1) than miconazole cream. In vivo, in rats, it was shown that Ag NPs also effectively reduced the fungal load in infected skin tissues over time.

The nature of the interaction of the dye Sbo {(E)-2-[4-(dimethylamino)styryl]-3-methylbenzo[d]oxazol-3-ium iodide} and its homodimer Dbo-10 with micelles of sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and Triton X-100 (TX-100) was studied using absorption and fluorescence spectroscopy. The fluorescence quenching mechanism of Sbo dye during the formation of complexes with SDS monomers was analyzed. Binding constants (K_S) of dye molecules with surfactants and free energy changes (ΔG⁰) for the probe−micelle binding process were determined. Quantum-chemical calculations of the charge distribution and potential energy of the ground and excited states of the dye molecules were carried out and explained the increase in the values of the quantum yield and the fluorescence lifetime in micelles. Based on the results, it was revealed that dye molecules were localized in the low-polar environment of micelles, where they were isolated from water molecules.

Chemometric-assisted UV-spectrophotometric methods, including least squares support vector machine (LS-SVM) and partial least squares (PLS) as multivariate approaches, were proposed for the quantitative simultaneous determination of levodopa (LEV) and benserazide (BS) in pharmaceutical formulation and urine samples. In the LS-SVM method, the related parameters, named the regularization parameter (γ) and width of the function (σ), were optimized, and the values with the minimum root mean square error (RMSE) were selected. The RMSE values were obtained at 0.9246 and 0.3423 for LEV and BS, respectively, whereas in the PLS model, the RMSE of the test set was found to be 0.3674 and 0.1216 for LEV and BS, respectively. The suggested models disclosed satisfactory recovery related to the synthetic mixtures in the range from 91.21 to 107.90% for LS-SVM and from 94.33 to 101.42% for PLS. The simultaneous determination of the LEV and BS in tablet dosage form and spiked urine samples using the proposed models revealed recovery higher than 94% and 91%, respectively. A comparison was made with the ANOVA test between the proposed methods and high-performance liquid chromatography (HPLC), and no significant difference was shown. These chemometrics methods are fast, facile, inexpensive, precise, and do not require sample pretreatment. Low solvent use, reduced energy consumption, and short time for analysis are other advantages of these methods. Therefore, they can be a safe and stable approach for drug analysis in quality control laboratories instead of expensive and time-consuming chromatographic techniques.

The growing emphasis on green technology has increased interest in cost-effective and environmentally sustainable methods for nanoparticle synthesis. In this study, lithium oxide nanoparticles (LiO NPs) were synthesized via a green route using Trigonella foenum-graecum leaf extract as both a reducing and capping agent. The synthesized nanoparticles were characterized using UV-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The UV-Vis spectra revealed strong absorption corresponding to the characteristic band of LiO NPs, with a red shift observed as the weight fraction increased. XRD confirmed the formation of LiO NPs with a monoclinic structure and an average crystallite size of 29.5 nm. SEM analysis showed nearly spherical, aggregated nanoparticles. The photocatalytic activity of LiO NPs was evaluated through the degradation of methyl orange under UV-Vis irradiation. In addition, the antibacterial activity of LiO NPs was tested against gram-positive bacteria (Staphylococcus aureus, Salmonella abony, and Bacillus subtilis), gram-negative bacteria (Escherichia coli), and the fungal pathogen Candida albicans. At a 50% weight fraction, the nanoparticles exhibited the highest antibacterial activity, with inhibition zones of 16.0, 11.0, 8.0 ± 0.10, 11.0 ± 0.32, and 10.0 ± 0.0 mm against E. coli, S. aureus, S. abony, C. albicans, and B. subtilis, respectively. Overall, this study demonstrates that T. foenum-graecum leaf extract can be effectively utilized as a capping, stabilizing, and reducing agent for the green synthesis of LiO NPs with significant antimicrobial potential. This eco-friendly and low-cost method enhances the antibacterial efficiency of LiO NPs and highlights their potential applications in biomedical fields.

Tb³⁺-activated lanthanum cerium phosphate (LaCePO₄) phosphors are synthesized using the modified solid-state reaction method. X-ray diffraction (XRD) patterns indicate a uniform crystalline structure. Scanning electron microscopy (SEM) images reveal that the samples had a large grain size and irregular, nonhomogeneous shape. The thermoluminescence (TL) glow curve is recorded for an optimized concentration of doping ion, and it shows the broad TL glow curve centred at 370°C for the UV-exposed sample. The corresponding trap parameters are calculated using the computerized glow curve deconvolution (CGCD) technique. CGCD analysis indicates that most of the peaks exhibit first-order and general-order kinetics, with shape factor (μ) values ranging from 0.313 to 0.568. The prepared phosphor may be useful in TL dosimetry applications.