Peer-rewieved journal "Zhurnal Prikladnoii Spektroskopii"
B. I. Stepanov Institute of Physics of the National Academy of Sciences
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D2-Line Spectroscopy of Potassium Atoms in an Optical Nanocell
The features of the transmission spectra of laser radiation through a nanocell with a variable thickness of the potassium atom vapor column in the range of 300–2000 nm of the D2-line are investigated. It is shown that at low laser radiation intensities, a narrowing of the resonance transmission spectrum is observed at thicknesses of L = (2n + 1)λ/2 (n is an integer) and a broadening of the spectrum at thicknesses of L = nλ. With an increase in the laser radiation intensity, velocity selective optical pumping resonances appear in the transmission spectrum of the nanocell. They are located at atomic transitions and have a spectral width 13 times smaller than the Doppler width. A comparison of the resonances in the nanocell with the resonances formed by the known saturated absorption technique is carried out. The obtained results can be used to form narrow optical resonances in miniature devices containing atomic vapors.
Determination of a Purely Electronic Transition in Molecular Electronic Spectra with Screening the Transitions
Determination of pure electronic transition (Е00) for molecular electronic spectra by quantum fluctuation theorem (QFT) is considered under external perturbations, decreasing elementary transition intensity and acting as its screening. To consider this effect “screening coefficient” is introduced into the main QFT relation. Using examples of molecular electronic spectra from the visible, UV, and X-ray regions, it is shown that the introduction of a screening coefficient brings the spectrum into conformity with QFT conditions and, consequently, with the conditions for determining a pure electronic transition using them. It means the reduction of the external excitation energy to the value suitable for QFT due to the screening. The operation of QFT model in molecular electronic UV-Vis and x-ray spectra is given. In proposed model Е00 depends on screening coefficient, but Е00 quantity, which is the closest to the true one, corresponds to the lowest screening coefficient.
Phosphores- cence of In(III)Cl-Etioporphyrin-I at 298 K
Phosphorescence of In(III)Cl-etioporphyrin-I in thin films of polyvinylbutyral was recorded at room temperature and atmospheric conditions. A series of phosphorescence spectra was obtained using the stroboscopic method, on the basis of which the glow duration τР ≈ 42 μs at 298 K was determined. A decrease in τР by almost two orders of magnitude with a change in temperature from 77 to 298 K confirms the quenching effect of atmospheric oxygen in the gas-permeable polymer matrix. With an increase in the excitation power density by ∼300 times, the quantum yield of phosphorescence at 298 K increases by ∼30 times, reaching a value of ϕР ≈ 0.74%.
Bands of Aluminum Monoxide for Alumina Determination in Cryolites by Means of Laser-Induced Breakdown Spectroscopy
Alumina (Al2O3), added to melt of the cryolite (Na3AlF6) in an electrolysis bath to produce metallic aluminum, remains often in the melt and leads to an increase in energy inputs. Therefore, monitoring the aluminum oxide content in cryolite is an important analytical task in aluminum production. In this paper, it is proposed to use the bands of the green system of aluminum monoxide AlO to estimate the alumina content in cryolites using laser-induced breakdown spectroscopy. For this purpose, a series of samples of NaF-Na3AlF6-Al2O3 system with a constant cryolite ratio (1.7) were used. It was found that focusing the radiation below the sample surface to a depth of 3–6 mm provides the minimum RSD values (4-8% for the 0-0 band and 6–10% for the 1–1 band) and the maximum signal-to-background ratio (80–120 for the 0-0 band and 40–75 for the 1–1 band) in the time window of 4–16 μs after the laser pulse. The selected focusing and time window conditions made it possible to detect a dependence between the intensity of the 0–0 and 1–1 bands of AlO and the alumina content, which is characterized by a high background and relatively low sensitivity. Normalization to the background makes it possible to use this dependence for qualitative separation of cryolite systems with high and low alumina content.
Surface Morphology, Optical and Electrophysical Properties of Cobalt-Doped Zinc Oxide Films Produced by Laser Deposition
The studies of thin ZnO+15%Co films, deposited in vacuum (p = 2.2 · 10–2 mm Hg) on the quartz and silicon substrates under multipulse high-frequency (f ∼ 10–12 kHz) laser action on a ceramic target at the laser power density of q = 81 MW/cm2 were conducted. The morphology of the obtained films was studied using atomic force microscopy, the features of the transmission spectra were presented. The analysis of the photoelectrical properties of ZnO+15%Co/Si structure was carried out.
Moving of Fluorine Ions under Dynamic Elastic Deformation in LaF3 Crystals
Using simulation, we studied the features of fluorine ion movement in a superionic lanthanum trifluoride crystal in the dielectric phase under dynamic elastic deformation caused by the propagation of an acoustic wave with a frequency of no more than 100 MHz. It was found that the concentration of fluorine ions in interstitial positions increases significantly in the tensile region and decreases slightly in the compression region. In the tensile and compressive zones, alternating at intervals equal to the half-length of the acoustic wave, the ionic conductivity can differ by an order of magnitude, forming localized regions of the superionic phase.
Synthesis and Structure Study of MAX-Phases (Cr2/3Ti1/3)3AlC2 and Cr1.5Ti0.5AlC Obtained by High-Temperature Sintering in Vacuum
Using vacuum sintering at 1300ºC of Cr, Al, graphite, and TiC or Ti powders, we obtained products consisting of two MAX phases: 312 and 211, the predominant formation of which depends on the type of precursor – TiC or Ti. In the synthesis from Cr:Al:TiC:C, the MAX phase 312 (Cr2/3Ti1/3)3AlC2 predominates, while in the synthesis from Cr:Al:Ti:C, the MAX phase 211 Cr1.5Ti0.5AlC predominates. α-Al2O3, carbides, and chromium oxides are present in the samples as impurities. A combination of X-ray diffraction and X-ray photoelectron spectroscopy methods made it possible to reveal significant differences in the chemical and phase composition of the surface and bulk of the samples. It was established that aluminum and chromium oxides, as well as Cr7C3 carbide, are formed on the surface of MAX phases during synthesis, similar to what occurs during the thermal oxidation of Cr2AlC and the formation of a protective layer of α-Al2O3/Cr7C3 on the surface. Formation of the protective layer is essential for producing Cr–Ti–Al–C-based materials with high thermochemical stability in aggressive environments.
Photoluminescence of Ge/Si Nanostructures with Ge Quantum Dots
Photoluminescence (PL) of Ge/Si nanostructures with Ge quantum dots (QDs) at 5, 78 and 300 K was studied. The nanostructures were grown by molecular beam epitaxy on single-crystal silicon substrates under 2 keV Ge+ ion irradiation and without irradiation. An effect of increasing the intensity of a broad PL band in the energy range of ~0.8 eV was found when the nanostructures were irradiated with Ge+ ions. A comparative analysis of the PL spectra recorded from the side of the silicon substrate and from the side of the formation of Ge/Si nanostructures was performed. It was found that during the growth of multilayer Ge/Si nanostructures with Ge QDs at temperatures of 500—600 °C thermal defects of the structure are formed in silicon, causing the appearance of an electron-vibrational bands with zero-phonon lines P ~ 0.767 eV, C ~ 0.789 eV, and H ~ 0.926 eV.
Studying the Mechanism of Catalytic Sonochemical Synthesis of Nanodispersed Molybdenum, Vanadium, and Tungsten Oxides by Dynamic Light Scattering
The process of the ultrasound-induced nucleation and growing of the particles of hydratated molybdenum, vanadium, and tungsten oxides in the aqueous solutions of corresponding oxo-acids have been investigated using the dynamic light scattering technique. It has been shown that the sonoinduced polycondensation of oxo-anions is catalyzed by nickel and iron through the redox mechanism that permits one to generate monodispersed oxide particles with medium size that varies (depending on the ultrasound exposure dose) from 2 to 526 nm in the case of MoO3, from 15 to 664 nm in the case of V2O5, from 40 to 1098 nm for WO3.
X-Ray Photoelectron Spectroscopy in an Atmosphere of High-Purity Argon as a Method of Studying Functional Materials Using Copper Amalgams as an Example
The composition and oxidized state of metals in copper amalgam samples obtained by direct reduction of metals (copper and mercury) in an aqueous solution were studied with X-ray photoelectron spectroscopy (XPS) in the atmosphere of high-purity argon 6.0. The use of XPS in a high-purity argon medium allowed one to exclude the influence of oxygen admixtures in the residual atmosphere of the spectrometer to the state of the amalgam surface and the investigation results. It is shown that the order of metal ions reduction in an aqueous solution of formaldehyde affects the content of oxidized forms of copper. With simultaneous reduction of copper and mercury, the resulting amalgam contains an impurity of 5–7 at. % copper in the form of copper(I) oxide and 8–10 at. % in the form of copper(II) oxide. During the sequential reduction of copper for the first and then mercury, the resulting amalgam contains an impurity of 11–14 at. % copper in the form of copper(II) oxide. During the reduction of copper by washing the resulting powder with dilute acid and subsequent reduction of mercury, the resulting amalgam contains an impurity of 9–11 at. % copper in the form of copper(I) oxide. The state of mercury in the amalgam does not depend on the order of metal reduction.
Quantum-Chemical Modeling of a Ternary System Carboplatin–Aminolevulinic Acid-Fullerenol
Using the HF-3c/MINIS/def2-SV(P)/ECP(Pt) quantum chemical modeling method, taking into account intermolecular interactions and the ORCA 5.03 software package, the electronic structure and binding energy of carboplatin, aminolevulinic acid, and fullerenol adducts and their ternary systems, both hydrogen-bonded and ester-bonded bioconjugates, were studied. Analysis of the total energies of the systems and calculated energy diagrams of the highest occupied and lowest unoccupied molecular orbitals of both the starting components and the molecular assemblies they form allowed conclusions to be drawn regarding the most likely stable combinations. The synergistic effects of the three-component system carboplatin–aminolevulinic acid–fullerenol C60(OH)24 were identified, and potential applications for chemotherapy in oncology were outlined.
Spectral Response of Hemoproteins to the Effect of Peroxidized Phosphatidylcholine and Its Derivatives
Based on the analysis of spectral changes in 403–423 nm wavelength range of a number of heme-containing proteins (human hemoglobin, equine myoglobin, horseradish peroxidase and bovine cytochrome C), it was found that the effect of UV-irradiated phosphatidylcholine (or oleic acid), expressed in the development of a differential spectrum in the Soret band (ΔD) during their interaction, is characteristic for hemoproteins of both animal and plant origin. It was shown that the intensity of the spectral response under the specified conditions was distributed in the following order: peroxidase ≥ myoglobin ≥ hemoglobin ≥ cytochrome C. The determination of peroxidase as the best indicator for the detection of peroxidized lipids by the spectroscopic method can be used while conducting clinical and biochemical studies with its participation, as well as for the development of new methods for diagnosing the body’s protection ability against oxidative stress and predicting its ability to recover from diseases of varying severity.
Photophysics of Styrylcyanine Molecular Probes in Solutions of Surfactants
The nature of the interaction of the dye Sbо ((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]oxazol-3ium iodide) and its homodimer Dbо-10 with micelles of sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) has been studied using absorption and fluorescence spectroscopy. The mechanism of fluorescence quenching of Sbo dye during the formation of complexes with SDS monomers was analyzed. Binding constants (KS) of dye molecules with surfactants and free energy changes (∆G0) 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, on the basis of which the increase in the values of the quantum yield and the fluorescence lifetime in micelles is explained. Based on the results obtained, it was revealed that dye molecules are localized in the low-polar environment of micelles, where they are isolated from water molecules.
Application of Single-Bubble Sonoluminescence to Determine Gasoline in Water
Single-bubble sonoluminescence spectra were recorded in the mode of a bubble moving near the center of levitation in a liquid for water samples contaminated with commercial gasoline, and they were analyzed. These spectra contained characteristic bands of emitters representing gasoline components: xylenes, terphenyls, anthracene, and C2, as a decomposition product in bubble plasma of other gasoline components (namely benzene, pentane, and hexane). Recording the bands of these emitters against the background of spectral continuum of water sonoluminescence allows the determination of gasoline in water from the most intense band of terphenyls depending on gasoline amount. A relationship between the intensity of this band and gasoline amount in water was constructed. The experimental data obtained in this work may be used to detect and find gasoline that pollutes water.
Powerful Exciplex XeCl Laser with Modular Excitation System
The article presents the results of studying the characteristics of the developed electric-discharge exciplex XeCl laser, which features a modular pumping system and the use of a bipolar charging voltage. The pumping system consists of three pairs of modules connected to a common load, i.e., the laser interelectrode discharge gap. It is shown that the modular transverse discharge excitation system allowed us to reduce the operating voltage to 36 kV with a discharge gap of 7 cm, shorten the discharge current pulse duration, and increase the pumping power of the active medium and the energy input into it. The article presents the results of studying the laser generation characteristics depending on the composition of the active medium and the conditions of its excitation. Using a working mixture of the composition HCl:Xe:Ne – 1:15:3000, under the pressure of 4 atm, at the charging voltage of 36 kV, the laser output energy of ~3 J was achieved. The laser generation pulse duration was ~120 ns at half-height.
Acousto-Optical Modulation of Annular Light Beams at Longitudinal Ultrasonic Waves in Paratellurite Crystals
Peculiarities of acousto-optical modulation of annular light beams with the wavelength of 532 nm on longitudinal ultrasound waves in paratellurite crystals are theoretically and experimentally investigated. Using the two-dimensional related wave theory the dependence of the diffraction efficiency of annular beams on the acousto-optical interaction length and ultrasound power is calculated. For the central ultrasound frequency of 100 MHz the bandwidth of modulator frequency tuning on annular beams of ~42–45 MHz is achieved at the level of 3 dB. It is shown that for the incident light beam of annular and Gaussian shape, the bandwidth differs insignificantly.
Electronic Properties and Optical Anisotropy of LiV3O8 Compound: Density Functional Theory Insight
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.
Numerical Simulation of High-Order-Mode Generation in a Plano-Concave Resonator with a Cavity Mirror Bearing a Non-Reflective Band
A formula based on the Fresnel–Kirchhoff diffraction integral formula, which yields the self-reproducing mode of a plano-concave resonator with a non-reflective band on the cavity mirror, was derived and converted into a discrete numerical integral. The Fox–Li iterative method was then used to obtain the self-reproducing mode of the resonator. The results reveal that the non-reflective band transforms the laser mode from the fundamental Hermite–Gaussian (HG) mode to a distributional characteristic that resembles that of high-order HG modes, albeit with minor differences. Therefore, placement of a straight non-reflective band on the cavity mirror of a plano-concave resonator conveniently generates laser field distributions with features of highorder modes.
High-Resolution Molecular Spectroscopy in Environmental Monitoring: an Experimental Study
Developments of molecular resolution spectroscopy have been key in environmental sensing, where the specificity and accuracy of analysis of the molecules in the atmosphere have been identified with high precision. An experimental analysis of the uses of molecular spectroscopy for the detection and measurement of minor compounds, emissions, and other climatic occurrences is discussed. Thanks to the analysis of changes in the spectra of different molecules, the environmental conditions and evaluation of the dynamics of pollutants with high accuracy is also possible. To track carbon dioxide, methane, nitrous oxide, and other greenhouse gases, aerosols, and toxic chemicals, we have carried out experiments with Fourier-transform infrared spectroscopy, cavity ring-down spectroscopy, and laser-induced fluorescence. It is also demonstrated that the integration of these technologies with drone-based remote sensing is being tested to explore new ways for realtime global environment monitoring. This paper shows how high-resolution spectroscopy revolutionized environmental studies have given policy-makers essential information on sustainable environment management.
Mixed Alkali Effect in Cr3+-Doped Li2O-K2O-B2O3 Glasses: Spectroscopic Investigations
Lithium-potassium-borate (LKB) glass was prepared by varying the concentrations of Cr3+ dopant using the melt-quenching technique. Further, UV-visible absorption, EPR, and FT-IR spectroscopy processes were carried out on the prepared samples. Evaluations were also conducted on a wide range of physical parameters. Nonlinear variations in physical parameters were observed for different glasses, indicating Mixed Alkali Effect (MAE). Various optical parameters, including Urbach energy and optical band gap were derived from the optical absorption data. Data from optical absorption were used to evaluate the crystal field and Racah parameters. The calculated bonding parameters suggest a covalent nature. The EPR spectrum of LKB glass doped with Cr3+ demonstrates significant signals that are characteristic of Cr3+ ions in distorted octahedral symmetry. The FTIR spectrum conveys trigonal BO3 and tetrahedral BO4 structural components that exist in the glass material.
Structural and Thermoluminescence Studies on Tb3+-Activated Lanthanum Cerium Phosphate Phosphor for Dosimetry Application
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.
Structural, Photoluminescence, and Thermoluminescence Studies on Dy3+-Activated Ca3Al2O6 Phosphor
Synthesis and characterization of Dy3+-activated Ca3Al2O6 phosphor are reported. The phosphor was synthesized by a modified solid-state reaction method with variable concentrations of doping ions (0.5–3.0 mol.%). The synthesized phosphors were characterized by X-ray diffraction (XRD) analysis, and it was revealed that the sample is monophased and crystallizes in a cubic structure. Scanning electron microscopy (SEM) results exhibited an irregular grain size distribution, ranging from 1 to 10 ìm. Fourier transform infrared (FTIR) studies confirmed the formation of Ca3Al2O6:Dy3+ phosphor. Photoluminescence (PL) excitation and emission spectra were monitored for variable doping concentrations. Ca3Al2O6:Dy3+ phosphor emits intense emission bands at 481 and 575 nm (excited at 350 nm) when doped with Dy3+ in the host. The corresponding transitions of the doping ion and concentration quenching effect were studied in detail. The 1931 CIE (x, y) chromaticity coordinates (x = 0.26 and y = 0.32) showed the distribution of the spectral region calculated from PL emission spectra. The thermoluminescence (TL) glow curve showed broad peak centres at around 248oC, and it was fitted using the computerized glow curve deconvolution (CGCD) technique. It was found that the deep trapping phenomenon occurs for UV-irradiated samples where the activation energy is high. Trap analysis elucidated the formation of luminescence centres in Dy3+-doped phosphors.
Rapid Identification of the Freshness of Pork Based on Near Infrared Spectroscopy and Back Propagation Neural Network Algorithm
The freshness of pork is a critical factor in determining its quality and value, impacting its economic worth and suitability for consumption. Near-infrared spectroscopy was employed to collect the spectra of pork from day 1 to 9 at 18 ± 2°C. The backpropagation neural network (BPNN) algorithm, in conjunction with the previously mentioned near-infrared (NIR) spectral data, was utilised to construct a predictive model for the assessment of pork freshness, with the duration of storage serving as the primary variable. The model was evaluated in comparison to more traditional approaches, including partial least squares (PLS) and random forest (RF) models. The experimental results demonstrated that the BPNN model exhibited the most optimal test performance, with a determination coefficient (R2) of 0.93; the root mean square error of prediction (RMSEP) was 0.62 days. Furthermore, the mean absolute error of the test set (MAE) for the BPNN model was 0.48 days, indicating satisfactory prediction results. The experimental data demonstrated the feasibility of the proposed method in accurately estimating pork freshness, thus providing a novel technological reference for meat detection.
Eco-Friendly Tandem Validated UV Spectrophotometric Methods for Estimation of Alfuzosin Hydrochloride and Tadalafil in Bulk and Combined Dosage Forms
Tadalafil and alfuzosin hydrochloride are frequently used together to treat benign prostatic hyperplasia. Recent approved combination of these medications was selected because only one study has investigated their synthetic mixture, and no research has examined the pharmaceutical dosage form using UV analysis. The purpose of this study is to create and verify a green UV spectrophotometric technique for the simultaneous measurement of tadalafil and alfuzosin hydrochloride in their combination dose form by developing two methods to ensure the lowest environmental impact, i.e., absorption correction method (method A) and the simultaneous equation method (method B). Tadalafil exhibited zero absorbance at 340 nm in method A, whereas alfuzosin hydrochloride exhibited absorption at 290 and 340 nm. Absorption maxima of 244 nm for alfuzosin hydrochloride and 283 nm for tadalafil are used in method B. A linear relationship in method A was found with correlation coefficient value of 0.999 for alfuzosin hydrochloride and 0.999 for tadalafil. While in method B, correlation coefficient of 0.999 and 0.996, respectively. All the validation parameters for the developed methods were found to be within the ICH guidelines’ limits. The developed UV spectrophotometric method received an AGREEprep score of 0.81, MoGAPI score of 77 and BAGI score of 72.5. For routine quality monitoring of alfuzosin hydrochloride and tadalafil, this approach offers a straightforward, affordable, and environmentally friendly substitute that preserves analytical performance while promoting sustainable pharmaceutical analysis. If successfully implemented, it can help labs lessen their environmental impact without compromising the accuracy of their analyses.
Application of Two Smart Nonlinear Multivariate Calibration Methods for the Concurrent Quantitative Spectrophotometric Determination of Antiparkinson Drugs in Pharmaceutical Formulation and Biological Samples: Comparison with HPLC
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 highperformance 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.
Biogenic Silver Nanoparticles Synthesized Using Almond Extract: Physicochemical Properties and Antifungal Efficacy Against Candida albicans
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 showed 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.
Quantitative Analysis of Flavokawain A by Derivative and Area Under Curve UV-Spectrophotometry
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), first-order 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.
Synthesis and Application of Functionalized Silicon Quantum Dots in the Analysis of Vitamin B6
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.
Rapid Quantitative Analysis of Silver Nanowire Synthesis via UV-Vis Spectral Deconvolution
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 wirelike 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 costeffective solution for optimizing industrial synthesis and quality control.
Green Synthesis and Evaluation of Lithium Oxide Nanoparticles for Antimicrobial and Photocatalytic Applications
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.