Peer-rewieved journal "Zhurnal Prikladnoii Spektroskopii"
B. I. Stepanov Institute of Physics of the National Academy of Sciences
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Effect of Changes in Solution Structure on the Phosphorescence of Acenaphthene in Supercooled Toluene During Heating
Changes in the phosphorescence intensity of acenaphthene in supercooled toluene during solution heating at a rate of 0.04 K/s at concentrations of 2 · 10–3 and 2 · 10–2 mol/L are studied. It is shown that when the glass transition temperature of toluene Tg = 117 K is reached, effective quenching of phosphorescence by oxygen begins for both solution concentrations. At the temperature of T = 130 K, an increase in intensity begins due to the appearance of a crystalline phase. The values of these temperatures are the same for both concentrations. For the solution concentration of 2 · 10–3 mol/L at T = 140 K, an “explosive” increase in intensity is observed due to self-acceleration of toluene crystallization. For the solution concentration of 2 · 10–2 mol/L, such changes are not observed. Possible causes of the established changes in the phosphorescence intensity and using this effect for studies of structural changes in supercooled organic solvents are discussed.
Study of the Mechanism of Formation of Photoaccumulating Titania-Based Heterooxide Composites Using IR Spectroscopy
The IR spectroscopic and photocatalytic studies of thin-film heterooxide composites TiO2-V2O5 obtained by codeposition of TiO2 and V2O5 colloids, chemical deposition of V2O5 shell over TiO2 particles, and thermal decomposition of ammonium vanadate in the presence of TiO2 particles have shown that the disordered V2O5 phase produced via pyrolytic synthetic route forms close heterocontacts with titania particles thus facilitating charge separation, while simultaneously ensuring favorable conditions for accumulation of the photoinduced charges.
Photoluminescence Spectra of Stacking Defects in 4H-SiC Crystals
Cree 4H-SiC single crystal wafers are studied by high-resolution non-destructive photoluminescence at room temperature to experimentally investigate near-band-edge (NBE) and stacking fault photoluminescence. The contribution of stacking fault photoluminescence to the photoluminescence spectrum of the original 4H-SiC crystals allows evaluating the relation of band-to-band, NBE, and stacking fault photoluminescence. The experimental photoluminescence spectrum of 4H-SiC obeys the Lorentzian distribution. Electron-phonon interaction leads to a significant mutual dependence of the intensities of band-to-band, NBE, and stacking fault photoluminescence.
Investigation of the Bleaching Properties of Photochromic Nanocomposites Based on Poly(Vinyl Alcohol) and Tungstophosphoric Acid
We have shown that the discoloration of photochromic poly(vinyl alcohol)–tungstophosphoric acid (PVA-TPA) nanocomposite films and PVA-TPA films containing glycerol (PVA-TPA-GL) colored by UV irradiation can be greatly accelerated by increasing the concentration of GL in the films and the ambient relative humidity. This study resolves the issues of polymer-heteropolyacid nanocomposites associated with their slow bleaching and, thus, makes them potentially applicable as new functional materials for inkless and erasable printing, anti-counterfeiting, sensors, smart windows.
Analysis of Blue Mussel Hydrolyzate Modified with Hypochlorous Acid Using Spectroscopic Methods
Using surface-enhanced Raman and infrared spectroscopy, the composition of blue mussel Mytilus edulis (M. edulis) acid hydrolysate after modification with HOCl has been characterized. It has been shown that the molecular targets for HOCl in M. edulis hydrolysate are methionine, histidine and NH2-group amino acid residues, as well as melanoidins, that provide the antioxidant effect of M. edulis hydrolysate, which is demonstrated in a model system with erythrocytes. Thus, M. edulis hydrolysate at a concentration of 0.05– 0.25% (v/v) dose-dependently inhibited hemolysis initiated by the addition of HOCl (200 μM) to a suspension of erythrocytes, and it completely prevented HOCl-induced hemolysis at a concentration of 0.5% (v/v).
Ligand-Binding Activity of Recombinant Tetracycline Antibiotics Receptor TetR as Determined by Fluorescence Spectroscopy
The ligand-binding activity of recombinant receptor TetR towards tetracycline (Tc) and its analogues (TC) has been studied by fluorescence spectroscopy. The addition of Tc to the functionally active protein in a solution quenched TetR tryptophan fluorescence by 80% and greatly enhanced the emission of Tc. The formation of the TetR-Tc complex was manifested by the appearance of a band in the Tc fluorescence region with a maximum at 510 nm, resulting from non-radiative energy transfer (FRET effect) from an excited tryptophan residue at 280 nm to the ligand. Other TCs (4-epi-Tc and lymecycline) also bound to TetR, exhibiting the properties of fluorescent probes. The spectral effects of complexation were reduced or completely disappeared in cases of partially or completely denatured TetR in the presence of urea. Therefore, fluorescence spectroscopy can serve as a reliable tool for assessing the TC-binding activity of recombinant TetR in the course of its preparation, storage and technological processing for practical use as a key component of bioanalytical systems for the determination of tetracycline antibiotics in food.
Method of Determining the Altitude and Flight Speed of an Unmanned Aerial Vehicle by the Brightness Signature of the Underlying Surface
A method is proposed for determining the altitude and flight speed of an unmanned aerial vehicle (UAV) from the brightness signature of the underlying surface (US), based on an analysis of the time parameters of the dynamics of changes in the intensity of the detected optical flow of the US during the flight of the UAV.
Regularities of Formation of the Visibility Zone by Active-Pulse Television Vision Systems with a Comparatively Short Duration of Backlight Pulses
For the second observation method, a model is proposed for forming the spatial-energy profile (SEP) of the visibility zone for a frequently implemented case in practice, when the duration of the laser illumination pulses of objects ∆tlas is significantly shorter than the duration of the strobe pulses (exposure time) of the photodetector ∆tpd. Based on the proposed model, analytical expressions are obtained that relate the characteristic distances (points) of the SEP of the visibility zone with the durations of the laser illumination pulses, photodetector strobing and internal (technical) delay, as well as the moments of time corresponding to the end of the front and the beginning of the decay of the strobe pulses for their trapezoidal or triangular shape. Numerical calculations confirmed the validity of the obtained analytical expressions. The possibility of controlling the shape, durations of the front and decay of the SEP by changing the corresponding parameters of the strobe pulses is demonstrated. On the other hand, based on the experimentally recorded SEP, it is possible to determine, for example, the front and tail times of strobe pulses with a trapezoid or triangular shape. It is shown that at ∆tlas << ∆tpd, the small distance effect (SDE) also manifests itself, which was previously discovered for systems with comparable values of ∆tlas and ∆tpd. The manifestation of SDE for a rectangular shape of strobe pulses is experimentally demonstrated.
Magnetometer Based on Single-Pass Generation in Alkali Metal Atomic Vapours
A description of a simple magnetometer is given, in which single-pass generation is realized on vapours of rubidium/cesium atoms located in an optical cell of several centimeters long, when resonant laser radiation with a wavelength of 852 nm (in the case of Cs) or 780 nm (in the case of Rb) passes. It is demonstrated that at the degenerate two-level cyclic transition Fe>Fg, an inverse population is realized between the upper and lower Zeeman sublevels. The sensitivity (change) of the output power of the generated radiation with a change in the external magnetic field by ~70 nT is achieved. It is shown that the system can function as a metal detector, and an advantage over commercial metal detectors is noted.
Spectrofluorimeter for Kinetic Spectral Analysis
A laser spectrofluorimeter for spectral-kinetic luminescent analysis has been developed. The spectrofluorimeter allows recording steady-state fluorescence spectra, fluorescence decay kinetics using the time-correlated single photon counting method with a time measurement range of 0.2–10,000 ns. Laser diodes (wavelength 400.7, 451.6, 508.2, 657.9, and 759.3 nm) with the ability to adjust the frequency of 0–20 MHz and the pulse duration at half-height of 70–200 ps or with an increased light power by 50–100 times and a duration of 1.5–3.0 ns, as well as light-emitting diodes (267.5, 305.0, and 368.1 nm) with the pulse duration at halfheight from 1.6 ns are used as fluorescence excitation sources. The optical scheme of the spectrofluorimeter is based on a monochromator-spectrograph with two output ports on which a CMOS detector and a photomultiplier are installed. In the monochromator mode, the spectrofluorimeter allows recording luminescence in the range of 200–900 nm, in the polychromator mode of 200–1000 nm. All main units are controlled from a single software, which includes the developed software module “FluoTau” for analyzing the fluorescence decay kinetics. This module allows approximating the recorded fluorescence decay kinetics with a sum of up to 5 exponents, has wide capabilities for preliminary processing and setting up the data approximation model.
Resonance Model of Self-Pulsation in Quantum Dot Lasers under Conditions of Nonlinear Frequency Chirp
The results of modeling the laser generation for the parameters of the gain elements on semiconductor quantum dots are presented taking into account a number of interrelated nonlinear effects leading to a shift in the frequency of the emitted field and the central frequency of the spectral resonance gain line. A qualitative analysis of the stability of solutions of the approximate model of radiation generation in the form of a system of rate equations is carried out. A special role of the optical Stark effect in the development of instability of the phase relationship of the light radiation field and the resonance response of the medium of the gain elements is established, leading to the spontaneous development of the oscillatory radiation mode at a constant excitation level by pumping.
Analysis of the Regularities of Light Waves Mixing by Phase Holographic Grating in Photorefractive Crystal of 23 Symmetry Class
A new analytical approach is proposed for determining the diffraction efficiency of phase holographic grating and the relative intensity of object wave during two-wave mixing in cubic photorefractive crystal, which is based on the classical theory of light wave propagation in optically active birefringent medium. It is shown that the values of the output energy characteristics of the reflection hologram found using this approach are in good agreement with the numerical data obtained by solving the coupled wave equations. Based on the described physical mechanism of diffraction and mixing of linearly polarized light waves by volume phase hologram, it is possible to establish optimal conditions for holographic experiment, under which the greatest efficiency of diffraction is achieved during the reconstruction and amplification of the object wave.
Formation and Propagation of Needle Light Beams
The field formed by an optical scheme of two axicons with a small difference in cone angles is investigated using analytical and numerical methods. The region of formation of a Bessel beam (BB) with a wide central maximum by this scheme is found. A method for obtaining needle beams characterized by a large diameter is proposed based on diaphragming of indicated BBs at the first minimum of the intensity distribution. It is shown that these beams, in comparison with limited Gaussian beams of the same power, have suppressed diffraction divergence. A comparison is made of the powers of the needle PNB and limited Gaussian PG beams incident on the receiving aperture with its different sizes and locations z, and it is shown that the PNB/PG ratio increases with increasing z. It is established that diaphragming of the BBs at the second or third minimum allows one to form light beams whose diffraction divergence is smaller than in the case of needle beams. The potential of using beams obtained by diaphragming a BB with a wide central maximum at the second minimum of the intensity distribution for probing objects located at a distance of up to tens of meters is shown.
Thin-Film Coating with Reduced Optical Reflection Coefficient Based on Germanium Nanoporous Layer
A method for producing a coating with a reduced optical reflectivity coefficient based on nanoporous Ge layers by implantation of monocrystalline c-Ge with 209Bi++ ions at an energy of E = 72 keV, a current density of J = 5 μA/cm2 and a dose interval of D = 1.3 ꞏ 1015—2.5 ꞏ 1016 ion/cm2 is proposed. It is found that starting from D = 6.2 ꞏ 1015 ion/cm2, an swelling spongy Bi:PGe layer with a thickness of about 100 nm is formed. This layer consists of thin intertwined Ge nanowires, which does not change morphological features with the increasing of values D. The layer is characterized by a low optical reflectivity coefficient (< 3%) in the visible spectral range.
Preparation of Efficient and Stable CsPbI3 Perovskite Active Layers with Vacuum-Dynamic Method
The dynamic vacuum-assisted thermal annealing method was employed to prepare CsPbI₃ perovskite active layers. CsPbI₃ is highly suitable for solar cells due to its high stability and optimal band gap (1.7 eV). Application of this method improved the active layer structure due to the reduction of defect states and nanopores, as well as the increase of crystalline grains size. The dynamic vacuum-assisted thermal annealing method effectively reduced trap-state density and suppressed recombination due to the faster removal of dimethylformamide (DMF). A comparative analysis of the optical and photovoltaic properties was conducted to evaluate the efficiency of perovskite solar cells (PSCs) fabricated using dynamic vacuum-assisted thermal annealing versus ambient-condition processing. As a result, the open-circuit voltage (Voc) of PSCs prepared by the vacuum-assisted method at low temperatures increased from 1.08 to 1.16 V. Additionally, the power conversion efficiency (PCE) of the active layers improved from 16.5 to 18.8%.
Near-Theshold Laser Spectroscopy of Rydberg and Autoionization States of Thallium Atom
Near-threshold spectra of Rydberg and autoionization states of a thallium atom have been studied with the method of selective stepwise photoionization of atoms with laser radiation. During the investigation, within ionization continuum near the threshold a so-called “transparence window” with the width of 25 ± 2 сm–1 was found, the center of which was 45 сm–1 higher than the border of atom ionization (Еi = 49266.71 cм–1). The formation of this window is evidently connected with a sharp and deep asymmetry of the discovered earlier Beutler–Fano autoionization resonance having the configuration of 6s6p2 4P3/2, and placing 659 сm–1 higher than the ionization border (Е0.5 = 49925.70 см–1). The autoionization resonance contour has such profile that Fano parameter (q) in wavelength continuum side turns close to zero. This happens probably due to the strong interaction with the continuum.
Spectroscopic and Elemental Analyses of Purplish Red to Pink Spinels from Myanmar, India, Mahenge, and Tunduru (Tanzania)
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.
Investigation of the Local Structure and Electron Paramagnetic Resonance Parameters of Tetragonal Cu2+ Centers in Sodium Fluoride-Sodium Borate Glasses
The local structure and electron paramagnetic resonance (EPR) parameters (gi factors and Ai 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.
Structural and Optical Properties of Liquid Crystalline Binary Mixtures with Dy3+ Phosphor Nanoparticles
In the current study, the structural and optical characteristics of a binary mixture composed of p-(npropyloxy) benzoic acid (3OBA) and p-(n-butoxy) benzoic acid (4OBA), integrated with varying concentrations (1, 1.5, and 2 wt.%) of Dy3+:Li4Zn(PO4)2 phosphor nanoparticles (NPs), are systematically examined. The synthesized liquid crystalline (LC) nanoparticle mixture was characterized using a range of analytical techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, and polarizing optical microscopy (POM). XRD analysis revealed that the size of the Dy3+-doped phosphor NPs in the LC mixture was approximately 85.23 nm. SEM images confirmed the uniform dispersion of Dy3+-doped phosphor NPs within the LC mixture. FTIR spectroscopy further corroborated the presence of functional groups associated with Dy3+-doped phosphor NPs in the synthesized compound. The optical bandgap determined from Tauc’s plot was increased by 0.62 eV due to doping of nanoparticles. Additionally, POM imaging revealed the phases of both pure and nanoparticledispersed LC mixtures, showing minimal changes in the nematic transition temperatures. Studies confirm that the synthesized liquid crystal nanoparticle mixture is an excellent material useful for microwave applications.
Structural and Thermoluminescence Investigations on γ-Ray Irradiated Limestone Sample
The present study reports the petrographical analysis and trap parameter calculation of γ-ray irradiated limestone sample collected from the Rasmada mines of Chhattisgarh Basin. A limestone sample was collected and preannealed before irradiation and recording of the thermoluminescence (TL) glow curve. The collected limestone sample was then characterized by X-ray diffraction, scanning electron microscopy (SEM), and TL glow curve analysis. The limestone sample revealed a cubic structure and its corresponding planes were calculated. SEM images showed a sound morphology and particle-size distribution above the microlevel. The TL glow curve was recorded for various doses of γ-rays from 0.5 to 2 kGy, and the dual peaks were decomposed with a single intense glow curve. The corresponding trap parameters were calculated using a computerized glow curve deconvolution technique. The findings suggest that the investigated limestone sample holds potential for application in gamma radiation dosimetry.
Spectroscopic and Thermoluminescence Glow Curve Analysis of Gd3+ Activated LaCePO4 Phosphor
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 programme, and the corresponding trap parameters were calculated.
Optimization of Synthesis Process and Photoluminescence of Eu3+-Doped NaSr4(BO3)3
A series of europium Eu3+-doped orange-red emitting phosphors were synthesized through a high-temperature solid-phase reaction using NaSr4(BO3)3 as the host in an atmosphere of air. The effects of calcination temperature and the contents of boric acid and Eu3+ on the photoluminescent properties of the as-prepared phosphors were investigated. In particular, the addition of boric acid in excess of the stoichiometric ratio could significantly improve the single-phase purity of the host. Meanwhile, the synthesis times for the phosphors were also reduced. The crystal phases and fluorescent properties of NaSr4-x(BO3)3:xEu3+ were characterized using X-ray powder diffraction analysis and a fluorescence spectrophotometer, respectively. The luminescent intensity of the phosphor was highest at the calcination temperature of 880℃ for 3 h, which was the optimum condition for forming single-phase NaSr4(BO3)3 hosts. All prepared NaSr4(BO3)3 phosphors belonged to the cubic crystal system. The maximum excitation wavelength was 392 nm. The main emission peaks were observed at 591 nm (orange light) and 615 nm (red light), which corresponded to the 5D0→7F1 and 5D0→7F2 transitions of Eu3+, respectively. Furthermore, NaSr3.92(BO3)3:0.04Eu3+ reached the maximum intensity of the main emission peaks, and the red-emitting performance was outstanding. The ratio (R/O) of the intensities of the emission peaks of red and orange lights could be affected by changes in the contents of Eu3+, so as to enrich and simplify the strategies for improving the red-emitting light purity. This provides a basis for the development of high-brightness and high-color-purity red-emitting phosphors for LED chips excited by near-ultraviolet light.
Detection of Malachite Green Residues in Aquatic Products Based on Fluorescence of Rare Earth Complexes
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.
Preparation and Photodegradation of Ag/ZnO on Low-Concentration Ammonia Nitrogen Wastewater
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 ofsimulated 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-minute 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.
β-Cyclodextrin Phenolphthalein Supramolecular System as Probe for Detecting Trace Tricyclazole by Competitive Host-Guest Inclusion
The extensive use of tricyclazole pesticide poses a serious threat to humans and the ecosystem, thus there is an urgent need to develop a sensitive and rapid detection method. In this study, a novel β-cyclodextrin (β-CD)/phenolphthalein (PP) supramolecular probe was designed for the determination of tricyclazole in water. Tricyclazole and β-CD formed a 1:1 inclusion complex in aqueous solution at 25 °C by using UV-visible spectra according to the Benesi-Hildebrand method. Phenolphthalein and tricyclazole compete to enter the hydrophobic cavity of β-CD due to host-guest recognition, causing changes in absorbance. Based on this principle, the β-CD/PP supramolecular probe exhibits a wide detection scope (1.0×10–5‒3.0×10–4 M) and moderate detection limits of 1.22×10–5 M for tricyclazole detection under the optimal conditions. The optimal geometries for the host and guest molecules were determined by density functional theory (DFT) calculations. Molecular docking analysis demonstrated the optimal PP and tricyclazole orientation inside the cavity of β-CD, and revealed the inherent driving forces of the inclusion reaction between β-CD and the guest molecules. Gibbs free energy change (∆G) values indicate that β-CD/tricyclazole is more stable than β-CD/PP inclusion complex. In addition, the β-CD/PP probe exhibited a high selective performance toward tricyclazole in water, and the β-CD/PP probe can be applied to detect tricyclazole in real water samples with satisfactory recoveries (93.8‒101.8%). This simple strategy establishes the potential for determining other pesticides by host-guest recognition that match the β-CD hydrophobic cavity.
Development and Validation of Tandem UV Spectroscopic Methods for Simultaneous Estimation of Dapagliflozin and Vildagliptin in Its Bulk and Combined Dosage Form
Dapagliflozin and Vildagliptin are type 2 antidiabetic drugs in which Dapagliflozin is a highly selective sodium-glucose cotransporter-2 inhibitor, and Vildagliptin functions as a dipeptidyl peptidase-4 (CD26) inhibitor. This research article proposes a specific tandem spectroscopy approach verified for the assessment of Dapagliflozin and Vildagliptin in their individual and combined pharmaceutical formulations. Method A (absorption correction), where the absorption maximum for Dapagliflozin was 223 nm, also showed absorbance at 276 nm, while the absorption maxima for vildagliptin occur at the same wavelength as the solvent peak, the detection wavelength was thus selected at 223 nm with a zero absorbance at 276 nm. The developed technique exhibited good linearity, ranging from 4–36 µg/mL for Dapagliflozin as well as 40–360 µg/mL for Vildagliptin, exhibiting a high degree of correlation (R2 = 0.9964) for Dapagliflozin and (R2 = 0.9991) for Vildagliptin. Method B (double point standardization method), Vildagliptin shows absorption maxima in the end UV region, thus, for avoiding interference with solvent peaks, the peak of Vildagliptin was shifted to the visible region by using bromocresol green. Ethanol was used as a solvent. The absorption maxima of Dapagliflozin and Vildagliptin were found to be 278 and 622 nm, respectively. The developed method showed good linearity, ranging from 20–52 µg/mL for Dapagliflozin as well as 200–520 µg/mL for Vildagliptin, and it exhibited a high degree of correlation (R2= 0.9989) for Dapagliflozin and (R2= 0.9996) Vildagliptin. Both methods exhibited good linearity, accuracy, and precision, with a low percent relative standard deviation, and they both demonstrated better recovery and reproducibility. A sensitivity test was performed by calculating the LOD and LOQ.
Development and Validation of a UV Spectroscopic Method for the Estimation of Gepirone Hydrochloride in Bulk and Tablet Dosage Form in Dissolution Media
This work focuses on developing and validating an accurate ultra-violet (UV) spectroscopic approach to quantify gepirone hydrochloride for in vitro dissolution studies in its pure drug and pharmaceutical dosage form. The method was designed to be straightforward, cost-effective, efficient, and suitable for routine analysis and quality control in pharmaceutical laboratories. With 0.1N HCl and phosphate buffer(pH-6.8), the gepirone hydrochloride exhibited λmax at 233 and 235 nm, respectively. The UV spectroscopic method showed excellent linearity with a high correlation coefficient of 0.998 and 0.996 for 0.1N HCl and a phosphate buffer(pH-6.8) in the 2–20 μg/mL concentration range. Beer’s principle was followed in the 2–20 μg/mL concentration range. Precision studies revealed minimal variability, both within and between assay runs, while recovery studies confirmed high accuracy. The method’s specificity was validated by the absence of interference from excipients, and its robustness was confirmed through small deliberate variations in experimental conditions, with no significant impact on performance. This UV spectroscopy method presents a practical, highly accurate, and reproducible approach for analyzing gepirone hydrochloride in pharmaceutical formulations, ensuring both regulatory compliance and the maintenance of drug quality.
Spectroscopic, Computational, and Crystallographic Study of Bioactive Hydroxypyrrolidin-2-One Derivatives
Five variants of hydroxypyrrolidine-2-one have been synthesized through a solvent-free one-pot reaction employing n-propylamine, isopropylamine, and ethylenediamine with a 2(3H)-furanone derivative. The reaction products demonstrated exceptionally efficient yield and eco-friendliness. Spectroscopic analysis was applied to fully characterize the samples, complementing single-crystal X-ray diffraction analysis and computational outcomes. The single-crystal diffraction of compound 1 confirmed its crystallization in a monoclinic system. The structure demonstrates a significant density of O–H…O interactions between molecules, which is consistent with the findings of the Hirshfeld investigation. The density functional theory (DFT) results and the observed crystalline structure are compared. A notable correlation was identified between the observed and theoretical geometric values. For bioactivity to occur, the most electrophilic site must be near the hydroxyl group linked to the heterocyclic ring, as indicated by the molecule’s electrostatic potential. The frontier molecular orbitals were examined to determine the energy disparity between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), indicating significant molecular stability. At a dosage of 3.4 µg/mL, compound 1 exhibited potent anticancer efficacy against breast and colon tumors in the HCT-116 and MCF-7 cell lines, respectively. Moreover, compound 5 exhibited substantial antibacterial efficacy.
Spectral Decomposition Method for Water Chemical Oxygen Demand Measurement Based on UV-Vis Absorption Spectroscopy
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.
Genetic Algorithm-Optimized B-Spline Feature Extraction for Accurate Concentration Prediction by Online Raman Spectroscopy: a Comparative Analysis of the Efficacy of Sparse Training Data
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 highprecision 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-ridge regression model (5-level training subset, RMSE = 6.02 mg/L) was the secondbest 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.