A model for forming a range-energy profile (REP) of the visibility zone for an object stationary relative to the system when the duration of the photodetector strobe pulses (exposure time) is significantly shorter than the duration of laser pulses illuminating the objects was proposed. Analytical expressions were derived linking the characteristic distances (points) of the visibility zone REP with the durations of strobe pulses, the uncontrolled technical delay, and the parameters of the laser pulses for different temporal shapes. Numerical calculations confirmed the validity of the obtained analytical expressions. It was established and experimentally confirmed that the REP, taking into account certain patterns, reproduced (displayed) the temporal shape of the laser pulse following from its beginning to its end when moving from the initial point of the visibility zone to the final point.
Constructing heterojunctions is important for improving the photocatalytic performance of materials. In this study, porous Fe2TiO5 was prepared via a sol-gel method, and CuS was grown in situ on its surface through a hydrothermal process, thereby successfully synthesizing CuS/Fe2TiO5 heterojunction composites. The CuS/Fe2TiO5 composites were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-Vis), and Brunauer–Emmett–Teller (BET) analysis. The results indicated that CuS is uniformly loaded on the surface of Fe2TiO5, with lattice spacings of 0.3550 and 0.2972 nm corresponding to CuS and Fe2TiO5, respectively, and no impurity phases were observed. Heterojunction construction induced distortion of the TiO6 octahedra at the interface, resulting in the emergence of a new absorption peak in the ultraviolet region. Among the samples, the 20 wt.
The physical characteristics of several series of marble samples taken from different regions of Morocco were experimentally determined. These characteristics include optical, elemental, and crystalline properties. The marbles and stones analyzed exhibited a variety of colors, including gray, white, black, yellow, and brown. For reference purposes, three white marble samples from Carrara, Italy; Drama; and Kozani, Greece were studied under the same conditions. A white marble sample from the 18th-century Moulay Ismail Mausoleum in Meknes was also studied under the same conditions. Using optical absorption spectroscopy, we identified bands attributed to ferrous and ferric ions (Fe2+ and Fe3+), which play a fundamental role in marble coloring. Other bands alongside long wavelengths were identified in accordance with crystalline and elemental studies and attributed to carbonates. Electron paramagnetic resonance (EPR) spectra revealed varying concentrations of Mn2+ ions in all the marbles studied. EPR lines attributed to Fe3+ ions distinguished ions resulting from Ca2+ substitution in the calcite lattice from those in iron oxides, clay minerals, and silicates. These identified ions are considered chromogenic elements responsible for the marbles' coloration.
Feasibility is demonstrated for obtaining a dielectric material derived from oxidized porous silicon and titanium oxide by depositing the latter onto porous silicon using a sol-gel method followed by high-temperature oxidation. The resulting dielectric material has an enhanced refractive index, making it promising for creating low-loss integrated optical channel waveguides in bulk microassemblies of electronic circuits with optical interconnects.
A green, stability-indicating UV-spectrophotometric method was developed and validated for the quantification of vanillic acid (VA) in bulk and niosomal formulations within a Quality by Design (QbD) framework. This method utilizes a phosphate buffer (pH 6.8) as an eco-friendly solvent, in accordance with the principles of green analytical chemistry. Key analytical variables, such as sonication time and scanning interval, were optimized using a Design of Experiments (DoE) approach to enhance precision and robustness. The optimized method exhibited a maximum absorbance at 251 nm with excellent linearity over a concentration range of 2–16 μg/mL (R2 = 0.999). Validation according to the ICH Q2(R1) guidelines demonstrated high accuracy (recoveries between 99.65–101.41
A new UV-visible spectrophotometric method using the first derivative has been established for the selective measurement of tyramine in fermented food samples, successfully minimizing interference from histamine. This method has been validated following ICH Q2(R2) standards, showing excellent linearity between 10 and 18 μg/mL, with a limit of detection (LOD) at 0.401 μg/mL and a limit of quantification (LOQ) of 1.217 μg/mL, confirming its sensitivity and dependability for routine testing. An evaluation of the method's environmental impact using AGREE (0.66), BAGI (62.5), and MoGAPI (74) tools revealed a favorable level of greenness, particularly regarding energy efficiency, minimal sample preparation, and safe preservation, despite certain less eco-friendly elements associated with methanol and trichloroacetic acid due to their harmful nature. In conclusion, this method offers a simple, accurate, and reproducible way to measure tyramine in fermented foods, providing important insights into environmental performance and supporting sustainable practices in food analysis.
Hydrogen sulfide (H2S), a recognized toxic gas, has emerged as a key indicator of food spoilage and a potential threat to water safety. Herein, a new fluorescent probe PHZ was designed and synthesized for sensing H2S. When added to PBS (10 mM, pH 7.40) solution, the probe PHZ exhibited a remarkable "turn-on" emission response at 450 nm producing a significant blue fluorescence. The probe PHZ demonstrated excellent selectivity and anti-interference performance in complex environments. It also exhibited good sensitivity for the detection of H2S; however, detection was limited to 0.23 μM. Moreover, the probe PHZ was successfully used for the detection of H2S in environmental water samples and monitoring food spoilage process. In summary, this study highlights the potential of fluorescent probes like PHZ for evaluating environmental water pollution and food freshness.
This work describes the development of a fluorescence sensor based on citrate-reduced gold nanoparticles (GNPs) conjugated with 5-aminofluorescein (5AF) using EDC/NHS chemistry to create GNP@5AF nanoparticles. These nanoparticles were used to detect tryptamine (TRYP) by measuring changes in fluorescence intensity upon incubation with various TRYP concentrations. The sensor showed efficient fluorescence quenching with good linearity and a detection limit of 4 ng TRYP. The sensor's applicability was tested in biological and food samples. In cheese and banana samples, a linear fluorescence enhancement allowed quantitative determination of TRYP within certain concentration ranges (2–10 ng in cheese and 2–16 ng in banana). However, nonlinear responses in other matrices limited the method's broader application. Interference studies indicated that GNP@5AF had a high selectivity for TRYP compared to other amine-containing molecules. Overall, the GNP@5AF sensor offers a simple and sensitive fluorescence-based method for detecting tryptamine, with potential for food safety monitoring. The study suggests that further optimization with selective ligands could improve sensor performance and analytical robustness.
Zinc oxide nanocrystals were synthesized in aqueous solutions at low temperatures. Their surface was coated with a thin film of the electrically conductive polymer poly(3-hexylthiophene) (P3HT) to form hybrid heterostructures. The synthesized nanostructures and hybrid heterostructures formed on their basis were subjected to heat treatment at various temperatures both in air and in vacuum (10–5 Pa). Changes in the optical properties of nanostructures and hybrid heterostructures after heat treatment were studied. The emission band corresponding to 0–0 transitions dominated the photoluminescence spectra of ZnO/P3HT heterostructures annealed in air. The photoluminescence spectra were dominated by the emission band corresponding to defects in ZnO and the polymer of heterostructures annealed in vacuum. Heat treatment of heterostructures based on ZnO nanocrystals in air and vacuum at 100°C resulted in an optimal state of the interface layer between ZnO and P3HT polymer.
The fluorescence of graphene quantum dots (GQDs) at various pH values, temperatures, and ionic strengths and in the absence and presence of peroxidases was investigated. Myeloperoxidase and the hypochlorous acid produced by it were found to cause GQD degradation in biological systems. The rate of substrate oxidation by horseradish peroxidase and myeloperoxidase was shown to decrease in the presence of GQDs. Fluorescence, biodegradation, and the ability to be functionalized make GQDs promising components for theranostic platforms.
The effect of reactor neutron irradiation on Raman scattering spectra and electron spin resonance (ESR) signals of monocrystalline CVD diamond films is studied. The presence of superparamagnetic clusters of spin radicals (ferrons) — regions of magnetic ordering of uncompensated electron spins (g-factor ≈4.65) in an external magnetic field — is revealed for the first time in neutron-irradiated (fluence 3·1018 cm−2) diamonds. It is established that thermal annealing at 400°C for 1 h drastically reduces the ESR signal intensity of spin-radical associates of radiation defects, while approximately doubles the amplitude of the ESR signal from single paramagnetic centers and narrows its linewidth by a factor of ≈4.6. Raman spectroscopy data indicate partial recovery of the crystal structure of diamond due to the annealing of both single radiation defects and nanoscale amorphized regions (ferrons). The types of defects responsible for the formation of ferrons in diamonds as a result of their irradiation with reactor neutrons are discussed.
New nontrivial sub-Doppler absorption resonances caused directly by steady-state optical pumping of atoms by evanescent radiation in thin cells with a rarefied gas medium were theoretically established and studied. The dependences of these resonances on the intensity of such evanescent pumping and its penetration depth into the gas were analyzed. The possibility of detecting these resonances using previously developed, well-tested laser spectroscopy methods in such thin gas cells was substantiated. The established sub-Doppler resonances could provide important information about the mechanism of atom–surface interaction and the properties of evanescent waves.
The plasma glow intensity (I), the electron energy distribution function (EEDF), the electron concentration (Ne), and the average electron energy (〈u〉) were measured as functions of the discharge current and the measurement location in a hollow cathode discharge. The EEDF shape near the hollow cathode was found to depend significantly on the discharge current. It exhibited a bi-Maxwellian shape at a current of 50 mA. A local maximum in the EEDF, the position and amplitude of which changed with increasing discharge current, appeared as the current increased. These changes led to a linear increase in the average electron energy. The electron concentration increased linearly with current changes from 50 to 200 mA, after which the value of Ne ceased to depend on the discharge current in the range 200–450 mA. The glow intensities of individual He atomic lines depended linearly on the discharge current.
Laser-induced fluorescence (LIF) in the wavelength range 400–1000 nm was studied using narrow-band laser radiation with a wavelength of 456 nm, resonating with the 6S1/2 → 7P3/2 transition of Cs atoms. A T-shaped cell made entirely of technical sapphire with length L = 1 cm, containing cesium atomic vapors, and capable of operating successfully at temperatures up to 450°C was used. The amount of residual Rb atomic vapors could be estimated by recording the LIF signal. The Cs-based cell could serve as an effective optical filter-converter of blue into red radiation.
The spectral and luminescence characteristics of synthesized europium(III) dimethoxyphenylacetates with nitrogen- and phosphorus-containing ligands were studied. The electronic absorption spectra, luminescence excitation spectra, and the Stark structure of 5D0–7Fj electronic transitions (j = 0–2) in the low-temperature luminescence spectra of europium(III) dimethoxyphenylacetates were analyzed and the quantum yield of the obtained complexes was determined. It was established that excitation energy is transferred to the europium(III) ion from levels of both the dimethoxyphenylacetic acid levels and the nitrogen-containing neutral ligands. The compounds in this study with the greatest thermal stability were identified.
A simple, rapid, sensitive, and economical spectrophotometric method is described for the determination of erbium(III) ions using 3-[2-hydroxy-3-sulfo-5-nitrophenylazo]pentane-2,4-dione (R) in the presence of cetyltrimethylammonium bromide (CTMABr) as a cationic surfactant. Optimal complexation conditions (λopt, pHopt) for homoleptic (Er(III)–R) and mixed-ligand complexes (Er(III)–R–CTMABr) were determined. The Er(III)–R complex exhibits maximum light absorption at 417 nm, while the Er(III)–R–CTMABr complex has maximum absorption at 426 nm. The molar extinction coefficient for the Er(III)–R complex is 0.92·104, while the corresponding value for Er(III)–R–CTMABr is 1.78·104. The optimal pH value for the complex formation of Er(III)–R is 8, while this value for Er(III)–R–CTMABr is 6. In the presence of CTMABr, the optical density of the complex is significantly enhanced, while the optical pH value for complex formation is shifted to the acidic region. The region of conformity to the Bouguer–Lambert–Beer law is linear in the erbium ion concentration range from 1.34 to 5.30 μg/mL for Er(III)–R and from 0.62 to 6.65 μg/mL for Er(III)–R–CTMABr. The stoichiometric ratio fo the components in the complexes was confirmed using the isomolar series method, Starik–Barbanel relative yield approach, and the equilibrium shift method. These methods confirmed the formation of complexes with component ratios Er(III):R = 1:2 and Er(III):R:CTMABr = 1:1:1. The effect of a series of extraneous ions on the formation of the Er(III) complexes was studied. The proposed method was used to determine trace amounts of Er(III) in volcanic rocks.
Composites derived from epoxy resin modified with silicon oxide nanoparticles were studied by spectral and physical-mechanical methods. The effects of the percentage content of the filler and the dose of γ-radiation on the strength of these composites were analyzed. The best procedure for hardening the composites was established. The optimal physical and mechanical characteristics were achieved at 1 mass
The structure of a near-surface plasma formation and plasma spectra were experimentally studied as functions of the time interval between laser pulses and their sequence with two-pulse laser action at radiation wavelengths of 1064 and 532 nm on an yttrium vanadate YVO4 target in air. The dependences of the laser plasma temperature on the parameters of paired laser pulses were established at power densities q1064 = 3.1·109 W/cm2 and q532 = 2.7·109 W/cm2, respectively. The optimal conditions for achieving the maximum temperature Te 1·104 K were shown to be leading action of laser radiation pulses with a wavelength of 1064 nm and a time interval between pulses of 6 μs. The maximum electron density Ne = 1.1·1017 cm–3 was achieved with a time interval of 15 μs.
The absorption of light by two-dimensional arrays of homogeneous spherical and cylindrical nanoparticles in an aluminum oxide matrix under lattice resonance conditions is studied. A semi-analytical statistical method SSM) based on the quasi-crystalline approximation of the theory of multiple scattering of waves is used to model the optical properties of arrays of spherical particles with different types and degrees of order. A numerical finite element method (FEM) is employed to model the optical properties of perfect lattices of cylindrical particles. Calculations for highly ordered imperfect lattices of spherical particles are in excellent agreement with FEM data for perfect lattices of such particles. The spectral dependences of the absorption coefficient of the arrays on the spatial organization, degree of order, size, shape, and concentration of silver, gold, cadmium selenide, and MAPbBr3 perovskite particles are presented.
The optical and photoelectrical properties of active layers of various thicknesses fabricated using the D18 donor polymer and the Y6 acceptor were analyzed. The light-absorption efficiency and charge-carrier separation capability of the D18:Y6 blend were investigated based on the absorption, photoluminescence, and external quantum efficiency spectra. The optimal active-layer thickness was shown to be 90 nm for semi-transparent organic solar cells (ST-OSCs). The D18:Y6 active layer is a highly efficient, stable, and promising material for ST-OSCs.
