Journal of Applied Spectroscopy最新文献

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.

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.

TiN–Ag@Ag composite substrates were prepared via ammonia reduction nitridation followed by electrochemical deposition. Fabricated TiN–Ag@Ag substrates were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and ultraviolet-visible spectrophotometry. The surface-enhanced Raman spectroscopy activity of these substrates was evaluated using ibuprofen as the probe molecule. The size of the Ag particles prepared via electrochemical deposition was approximately 1 μm, and Ag nanoparticles with an average particle size of 100 nm were uniformly distributed on the surface of TiN–Ag films. The Raman signal of ibuprofen was significantly enhanced, and the minimum detection concentration of ibuprofen was 10^–5 M. The mechanism by which the TiN–Ag@Ag composite substrate enhanced the Raman signals was analyzed using ultraviolet photoelectron spectroscopy and density functional theory implemented in the Gaussian software. Overall, charge transfer and the local electromagnetic field effect enhanced the Raman signals of ibuprofen.

Triple hybrid nanocomplexes based on selenium (Se⁰) nanoparticles, cellulose polymer carrier (CPC), and the photosensitizer fotoditazine (FD) were synthesized with different sequences of component addition and ratios. The spectral characteristics of these triple nanocomplexes were compared with analogous characteristics of FD and double complexes of variable composition (FD/Se⁰, CPC/FD, and CPC/Se⁰) using spectral methods. The synthesized triple hybrid Se-containing nanocomplexes could be promising for photodynamic therapy and diagnostics.

An advanced chemometric model based on ratiometric surface-enhanced Raman scattering (SERS) was developed for the quantification of glucose in serum samples. In the absence of glucose, it was mainly the SERS signal of silver nanoparticles (AgNPs)-o-phenylenediamine (OPD). When glucose was added, glucose oxidase catalyzed glucose to produce hydrogen peroxide (H₂O₂), which oxidized OPD to produce 2,3-diaminophenazine (DAP) in the presence of AgNPs. The generated DAP exhibited a new strong SERS signal and changed the Raman peak ratio between DAP and OPD. Without using any internal standard, the advanced chemometric model mitigated the fluctuations in SERS intensity and achieved accurate concentration predictions for glucose in serum samples with recoveries in the ranges of 92.8–104.8%. The accuracy of the quantitative results obtained using the proposed method is comparable with that of the reference method — glucometer. The proposed sensor showed high sensitivity and selectivity in detecting glucose with a limit of detection (LOD) of 0.28 μM. Additionally, the presented SERS sensor demonstrated great promise in determining H₂O₂-related metabolites in real serum samples.

The vibrational spectra of the natural ammonium sulfates tschermigite NH₄Al(SO₄)₂(H₂O)₁₂, lonecreekite NH₄Fe(SO₄)₂(H₂O)₁₂, ammoniovoltaite (NH₄)₂Fe²⁺₅Fe³⁺₃Al(SO₄)₁₂(H₂O)₁₈, sabieite NH₄Fe(SO₄)₂, ammonioalunite NH₄Al₃(SO₄)₂(OH)₆, and ammoniojarosite NH₄Fe₃(SO₄)₂(OH)₆ were studied to determine the behavior of ammonium in symmetry-inappropriate positions. Disorder of the ammonium cation in salt crystals caused by the need to adjust the tetrahedral cation to the symmetry of the position to preserve the crystal symmetry was revealed. If the symmetry group of the position was not a subgroup of the tetrahedral symmetry group, the NH₄ tetrahedron was distorted by the subgroup Hʹ common for T_d and H, where H is the symmetry group of the position. Then, a polyhedron corresponding to the symmetry of the position was constructed from N = |H|/|Hʹ| (|H| and |Hʹ| are the orders of these groups) distorted tetrahedra. The disordered ammonium cation had several orientations (N), the superposition of which formally gave a polyhedron corresponding to the local symmetry. The maximum common subgroups for the given salts were C_3v and C₃. Distortion of ammonium led to activation of ν₁ and ν₂ [NH₄⁺ ] vibrations in the IR spectrum and splitting of ν₃ and ν₄ [NH₄⁺ ]. However, the effect was barely noticeable for ammonium in a centrosymmetric position, as in ammonioalunite and ammoniojarosite. The ν₄ [NH₄⁺] band was noticeably split and ν₁ and ν₂ [NH₄⁺ ] vibrations were clearly visible in spectra of the ammonium alums, ammoniovoltaite, and sabieite.

A series of Tb³⁺-doped Li₂CaSiO₄ phosphors were prepared by high-temperature solid-state reaction method. The structural studies were done using the X-ray diffraction (XRD) technique. The XRD patterns revealed that the sample was monophased and crystallizes in a cubic structure. Scanning electron microscopy (SEM) was used to obtain information about the morphology of the prepared samples. SEM micrographs clearly indicated that the particles crystallized in inhomogeneous morphology, with the particle size ranging from 1 μm to 100 nm. Also, photoluminescence (PL) analysis of the phosphor samples for different concentrations of doping ions with variable excitations were presented. The PL excitation spectrum of Tb³⁺ ion-doped Li₂CaSiO₄ has many sharp peaks, mainly at 418 nm (⁵D₃ → ⁷F₅), 436 nm (⁵D₃ → ⁷F₄), 456 nm (⁵D₃ → ⁷F₃), 472 nm (⁵D₃ → ⁷F_2,1,0), 487 nm (⁵D₄ → ⁷F₆), 550 nm (⁵D₄ → ⁷F₅), and 590 nm (⁵D₄ → ⁷F₄), assigned to the transitions of Tb- ion respectively (excited at 237 nm). The 1931 CIE (x, y) chromaticity coordinates showed the distribution of the spectral region calculated from PL emission spectra, and found to be (0.19, 0.22) in a bluish-green region of Tb³⁺ (0.01 wt (in grams)) Li₂CaSiO₄ phosphor. Our study shows that as-prepared phosphor may be useful for optical devices, mainly for LEDs, as a bluish-green component.

Aluminum is a widely distributed element and plays an indispensable role in our lives, but excessive intake of Al³⁺ can cause potential harm to human health. Highly selective methods for the rapid detection of Al³⁺ are urgently needed. Here, a novel "turn on" fluorescent probe L based on Schiff-base of 2-hydroxy-1-naphthaldehyde and 8-aminoquinoline was obtained in an excellent yield. Probe L presents significant properties such as rapid response, good stability, wide pH range, simple synthetic operation, and provides an efficient strategy for the highly selective detection of Al³⁺ in an aqueous solution of DMSO/H₂O (7:3, v:v). According to Job's curve and fluorescence titration, probe L with Al³⁺ forms a 2:1 ratio of complex, and the lowest limit of detection is 3.23 × 10⁻⁸ mol/L. The possible combination mode for probe L with Al³⁺ was proposed by comparison with the changes of 1H NMR and FTIR spectra of L and its complex. In addition, the potent applicants for probe L were also investigated, and indicated that it could conveniently be made into a series of sensor strips and applied to rapidly detect trace Al³⁺ in traditional Chinese medicine.

Ultraviolet-emitting phosphors with the formula K_2–xPb_xAl₂B₂O₇ (0.0025 ≤ x ≤ 0.03) were synthesized at 850°C for 6 h in air. The powder X-ray diffraction technique was used to analyze the phases of all prepared borates. The FTIR technique was used to examine the bond structure of K₂Al₂B₂O₇. At room temperature, a spectrofluorometer was used to examine the photoluminescence characteristics of the prepared phosphors. K₂Al₂B₂O₇:Pb²⁺ was found to have emission and excitation bands at 373 and 271 nm, respectively. An extensive investigation was conducted on the correlation between emission intensity and Pb²⁺ content for K_2–xPb_xAl₂B₂O₇. Consequently, 0.01 mol Pb²⁺ was found to be the optimal concentration in K₂Al₂B₂O₇. Eventually, it was found that the Stokes shift of the prepared material K₂Al₂B₂O₇:Pb²⁺ is 10,090 cm⁻¹ using the excitation band at 271 nm and the emission band at 373 nm. As a result of this investigation, a brand-new UVA radiation-emitting material has been established.

A detailed analysis of the previously discovered effect of the concentration of phosphotungstic acid (PTA) on its reduction within nanocomposite films with poly(vinyl alcohol) (PVA) induced by gamma radiation indicated that the molar absorption coefficient of the maximum of the PTA band due to intervalence charge transfer in reduced PTA heteropolyanions at low PTA concentrations is eight times higher than at high concentrations. Only 20% of this increase is attributed to the predominance of two- and one-electron-reduced heteropolyanions at low and high concentrations, respectively. We concluded that the main reason for the concentration effect is associated with a decrease in the size the PTA nanoparticles with decreasing PTA concentration in the films.