Journal of Applied Spectroscopy最新文献

The correct conditions for measuring the luminescence intensities in fi laments formed by the action of femtosecond laser pulses were found for lithium fluoride crystals. The determined conditions ensured that the measured intensities were proportional to the concentrations of luminescent color centers created in the crystals by the laser radiation and allowed conclusions to be drawn about the processes occurring in the filaments. Near-cluster color centers were found, indicating the presence of nanosized clusters in all areas of the fi laments.

The light pressure of an evanescent electromagnetic wave formed by total internal reflection near the flat interface of a dielectric and a liquid on a dielectric spherical nanoparticle located in a liquid medium is considered. Phase portraits of a two-dimensional system of equations that is equivalent to the equation of nanoparticle transportation under the influence of the force gradient of the light pressure of the evanescent field taking into account the medium resistance force are plotted. Various phase portraits can be realized both without equilibrium points and with one equilibrium point (stable focus, stable node or saddle) on the phase plane, depending on the parameters of the laser radiation and the material of the nanoparticle suspended in the water.

The spectral and bactericidal properties of a number of biodyes including bromophenol blue, amido black 10B, methyl thymol blue, basic fuchsin, chrome dark blue, eosin, indigo dye, and bromophenol red have been characterized. The inclusion of eosin, bromophenol red, indigo, and rifampicin into the internal space of phospholipid nanocontainers was shown to lead to leveling of the characteristic absorption maxima in the visible and ultraviolet regions of the spectra of these compounds taken in aqueous solution. This effect allows visual and spectrophotometric monitoring of the prodrug incorporation into liposomes. The construction of a number of supramolecular forms of prodrugs, which are micelles and liposomes derived from modifications of the bactericidal nucleoside brivudine in various combinations, showed the feasibility of using indigo as a dye marker. This permits the identification of liposomes formed from an equimolar mixture of dimyristoylphosphatidylbrivudine lipoconjugate with dimyristoylphosphatidylcholine as a potential prodrug formulation that most effectively inhibits the growth of Staphylococcus aureus cells.

A process for creating a macroporous silicon substrate on which a layer of titanium dioxide was deposited using the atomic-layer deposition method is described. Electrochemical etching was used to form the macroporous structure of the substrate. TiO₂ was deposited using an SI PEALD setup. The morphology, structure, and optical properties of the deposited TiO₂ film were assessed using scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy, spectral ellipsometry in the range 240–1000 nm, and Raman spectroscopy. Raman spectra revealed peaks at 144, 194, 397, and 639 cm^–1 that were characteristic of the TiO₂ anatase modification. The absorption coefficient and optical band gap width of the deposited film were determined based on the calculated ellipsometric parameters.

One of the inherent limitations associated with laser-induced breakdown spectroscopy (LIBS) in the identification of elements lies in the strength of the emission signals. Several approaches exist to enhance the emission capacity of LIBS. In this particular investigation, our focus was on amplifying the signal intensity of LIBS through the utilization of two techniques. These techniques include the application of a low-power electric field within the zone where plasma is formed, in conjunction with the utilization of nanoparticles on the surface of the sample. Specifically, our analysis involved the examination of samples consisting of metallic Zn powder as the matrix element, with the incorporation of small quantities of Ca in the form of CaCO₃. The combination of these two methods resulted in unprecedented outcomes, demonstrating a 3.5-fold increase in samples containing 0.05% w/w of CaCO₃ when subjected to an electric field of 60 V/cm, while bearing nanoparticles on their surface.

Spectroscopic studies of Ho³⁺-doped SrF₂ crystals were performed regarding applications in solid-state lasers. The crystal structure of the Ho:SrF₂ crystal was investigated using single-crystal X-ray diffraction. SrF₂ exists as a cubic structure with an Fm3m space group. A Raman shift of 288 cm^–1 was observed for the Ho:SrF₂ single crystal. SrF₂ hosts with low-frequency vibrational modes are suitable for reducing nonradiative emissions while maximizing radiative emissions. The absorption spectrum was recorded in the visible region from 400 to 800 nm, yielding absorption lines at 416, 450, 468, 473, 484, 536, 638, and 643 nm. The fluorescence spectrum recorded at an excitation wavelength of 450 nm shows two emission bands at 546 and 656 nm, which correspond to green and red emission, respectively. The intensity parameters Ω_λ (λ = 2, 4, and 6) were estimated using the Judd–Ofelt theory. For Ho:SrF₂ single crystal, the calculated Ω_λ are Ω₂ = 0.14 × 10–20 cm², Ω₄ = 3.14 × 10^–20 cm², and Ω₆ = 3.74 × 10^–20 cm². The radiative transition probabilities, radiative lifetimes, and branching ratios β_R for Ho:SrF₂ were determined using the Judd–Ofelt parameters. The ⁵S₂ + ⁵F₄ → ⁵I₈ transition is more effective for population-building processes because of its lifetime (0.26 ms) and higher branching ratios (~82.86%). Ho:SrF₂ is, therefore, a promising solid-state laser crystal for green and red spectral regions.

Plants play an important role in nanoparticle preparation because they are easily accessible, environmentally friendly, and inexpensive. In this study, we used an ethanolic extract of Mangifera indica seed as a reducing and stabilising agent to create zinc oxide (ZnO) nanoparticles (NPs). The ZnO NPs were examined using characterization techniques such as UV-Vis, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The interaction of phytochemical constituents from plant extracts providing the biological reduction of zinc metal ions to ZnO had been identified by the UV-visible absorption studies. According to the FT-IR results, metal oxides exhibited interatomic vibration-driven absorption in the fingerprint area below 1000 cm^–1. Particles appeared to be crystalline and also a rice-grain shape of ZnO NPs was confirmed by XRD, SEM, and TEM, respectively. In addition, the cytotoxic effect of ZnO NPs was checked using the SKMEL-28 cell line, showing an IC50 value of 32.686 μg/mL in the SKMEL-28 cell line, and 49.011 μg/mL in the typical L6 cell line. Furthermore, the synthesized NPs were subjected to (AO/EB) double staining approach to examine the apoptotic activity. The acridine orange/ethidium bromide method made strong evidence for demonstrating chromatin condensation and membrane blebbing.

Results of spectroscopic measurements of the equilibrium electron concentration behind a strong shock wave in argon at a shock-wave velocity of 4.2 km/s and a pressure ahead of the wave front of 5 Torr and in O₂, N₂, and air in the velocity range from 8.3 to 11.3 km/s at an initial pressure of 0.25 Torr are presented. The measurement method was based on an analysis of broadening of the hydrogen-atom H_β line of the Balmer series in the spectrum of the integral radiation density of the studied gas to which a small amount of H₂ was added (~1%). The dependence of the electron concentration on the shock-wave velocity in O₂, N₂, and air was established. The results were compared with available experimental and calculated data.

Remote detection of trace explosives and hazardous chemicals has been an ongoing challenge and a critical issue in defense science, public safety, and counterterrorism. Raman spectroscopy, a form of inelastic scattering, acts as a "fingerprint" analysis method for substance identification with high confidence in the detection of chemicals based on their vibrational modes. Here, we present a portable stand-off time-gated Raman spectroscopy, which consists of a passive Q-switched pulsed laser, a designed gated ICMOS, a spectrometer, and a telescope, with an overall size of 476.5 × 321.5 × 219.3 mm and a weight of 23.2 kg, which is much more compact and portable than reported previously. To confirm the effectiveness of the designed portable time-gated Raman spectroscopy, detections at different working distances and various amounts of substances are carried out. High levels of Raman identification are acquired even for 0.1 mg at a 10-m distance. Furthermore, we simulate realistic encounters in a possible war-zone scenario by testing the system's ability to recognize urea samples on different substrates such as an aluminum plate, woodblock, cardboard, black cloth, and leaf; good characteristic recognition is shown.

Umifenovir, an antiviral drug that is used to treat influenza, has recently been used in regards to COVID-19 infection. According to a literature survey, no UV technique for the estimation of umifenovir has yet been established; hence, there is an imperative need for a simple analytical method. Additionally, we developed an alternative reverse-phase high-performance liquid chromatography (RP-HPLC) method for the estimation of umifenovir. UV spectrophotometry was carried out at 223 nm absorption maxima using the solvent methanol. A concentration range of 2–12 μg/mL was found to obey Beer’s law, with a correlation coefficient (r²) of 0.9995. A C-18 column (250 mm, 4.6 μm, 5 μm) was used for chromatographic separation using the isocratic mode. The mixture consisted of acetonitrile: 0.1% trimethylamine (pH adjusted to 2.7 by the addition of orthophosphoric acid) 60:40 as the mobile phase with a flow rate of 1 mL/min. The temperature was kept at 25°C, and detection at 223 nm was performed using a PDA detector. The estimated percentage of the drug was close to 100%, corresponding to the label claim of the tablet made in the laboratory. The results and statistical study demonstrated the utility of the current methods in the routine evaluation of umifenovir bulk and formulation.