Journal of Applied Spectroscopy最新文献

In the current study, the structural and optical characteristics of a binary mixture composed of p-(n-propyloxy) 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 nanoparticle–dispersed 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.

The ligand-binding activity of the recombinant receptor TetR towards tetracycline (Tc) and its analogs (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 indicated by the appearance of a band in the tetracycline fluorescence region with a maximum at 510 nm resulting from nonradiative energy transfer (FRET effect) from a tryptophan residue excited at 280 nm to the ligand. Other tetracyclines (TC) (4-epi-TC and lymecycline) also bind to TetR, exhibiting the properties of fluorescent probes. The spectral effects of complexation were reduced or even completely eliminated in cases of partially or completely denatured TetR in the presence of urea. Thus, fluorescence spectroscopy can serve as a reliable tool for assessing the TC-binding activity of recombinant TetR during its preparation, storage, and processing for practical use as a key component of bioanalytical systems for determining traces of tetracycline antibiotics in food.

A simple magnetometer in which single-pass generation is realized on atomic rubidium/cesium vapors located in an optical cell several centimeters long upon passage of resonant laser radiation with a wavelength of 852 nm (in the case of Cs) or 780 nm (in the case of Rb) is described. It is demonstrated that a population inversion at the degenerate two-level cyclic transition F_e > F_g between the upper and lower Zeeman sublevels is realized. The output power of the generated radiation is sensitive to a change in the external magnetic field by ~70 nT. It is shown that the system can function as a metal detector. An advantage over commercial metal detectors is noted.

A new analytical approach for determining the diffraction efficiency of a phase holographic grating and the relative intensity of an object wave during two-wave mixing in a cubic photorefractive crystal is proposed. It is based on the classical theory of light wave propagation in an optically active birefringent medium. The values of the output energy characteristics of the reflection hologram found using this approach are shown to be in good agreement with numerical data obtained by solving the coupled wave equations. The optimal conditions under which the greatest diffraction efficiency is achieved for a holographic experiment during reconstruction and amplification of the object wave can be established based on the described physical mechanism of diffraction and mixing of linearly polarized light waves by a volume phase hologram.

Results of modeling laser generation for the parameters of gain elements on semiconductor quantum dots are presented considering several interrelated nonlinear effects leading to a frequency shift of the emitted field and the central frequency of the spectral resonance gain line. The stability of solutions of the approximate model of radiation generation in the form of a system of rate equations is qualitatively analyzed. A special role of the optical Stark effect in the development of instability in the phase relationship of the light radiation field and the resonance response of the medium of the gain elements is established and leads to the spontaneous development of the oscillatory radiation mode at a constant excitation level by pumping.

For the second observation method, when a certain value of the delay distance S_del is set on the control panel, a model for the formation of the spatial-energy profile (SEP) of the visibility zone was proposed for the case often realized in practice when the duration of the laser illumination pulses of objects Δt_las is significantly shorter than the duration of the strobe pulses (exposure time) of the photodetector (PD) Δt_PD. Analytical expressions that relate the characteristic distances (points) of the visibility zone SEP to the durations of the laser illumination pulses, photodetector strobing, and internal (technical) delay and the time points corresponding to the end of the strobe-pulse front and the beginning of its decay for their trapezoidal or triangular shape were obtained based on the proposed model. Numerical calculations confirmed the validity of the obtained analytical expressions. The possibility of controlling the shapes and durations of the front and decay of the SEP by changing the corresponding strobe-pulse parameters was demonstrated. On the other hand, it was possible to determine, e.g., the front and tail times of strobe pulses with a trapezoidal or triangular shape based on the experimentally recorded SEP. It was shown that for Δt_las ≪ Δt_PD, the small distance effect (SDE) that was previously discovered for systems with comparable values of Δt_las and Δt_PD also manifested itself. The manifestation of an SDE for rectangular shape strobe pulses was experimentally demonstrated.

Surface-enhanced Raman and infrared spectroscopy techniques were used to characterize the composition of blue mussel Mytilus edulis (M. edulis) acid hydrolysate. The molecular targets of HOCl in M. edulis were found to be methionine and histidine residues as well as amino acid NH₂ groups along with melanoidins, which provide for the antioxidant effect of the M. edulis hydrolysate, which we demonstrated in a model system with erythrocytes. Thus, the hydrolysate of M. edulis at concentrations 0.05–0.25 vol.% provides dose-dependent inhibition of hemolysis after the addition of 200 μΜ HOCl to a suspension of erythrocytes and completely prevents HOCl-induced hemolysis at a concentration of 0.5 vol.%. At higher concentrations (10 vol.%), the M. edulis hydrolysate also protects against acid hydrolysis. Thus, the M. edulis hydrolysate can act as a bioavailable substance for the prevention of hemolysis of various etiologies.

A laser spectrofluorimeter for spectral-kinetic luminescence analysis has been developed. The spectrofluorimeter allowed steady-state fluorescence spectra and fluorescence decay kinetics to be recorded using a 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 to 0–20 MHz and the pulse length at half-height to 70–200 ps or with the light power increased by 50–100 times with a length of 1.5–3.0 ns and LEDs (267.5, 305.0, and 368.1 nm) with a pulse length at half-height from 1.6 ns were used as fluorescence excitation sources. The optical scheme of the spectrofluorimeter was based on a monochromator-spectrograph with two output ports on which a CMOS detector and a photomultiplier were installed. The spectrofluorimeter in the monochromator mode allowed luminescence in the range 200–900 nm to be recorded; in the polychromator mode, 200–1000 nm. All main units were controlled by a single software program that included the developed software module FluoTau for analyzing the fluorescence decay kinetics. This module allowed the recorded fluorescence decay kinetics to be approximated with a total of up to 5 exponents and had wide capabilities for preliminary processing and setting up the data approximation model. It was shown based on experimental results for eight samples that the spectrofluorimeter allowed luminescence decay times in the range 0.2–10,000 ns to be measured with a time resolution of <0.1 ns.

A method for determining the altitude and speed of flight 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 is proposed.

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 by this scheme of a Bessel light beam (BLB) with a wide central maximum is found. A method for obtaining wide-diameter needle beams is proposed based on diaphragming of the indicated BLBs at the first minimum of the intensity distribution. It is shown that these beams have suppressed diffraction divergence as compared to limited Gaussian beams of the same power. The powers of the needle P_NB and limited Gaussian beams P_G incident on the receiving aperture with its different sizes and locations z are compared. It is shown that the P_NB/P_G ratio increases with increasing z. It is established that diaphragming of the BLBs at the second or third minimum allows light beams with diffraction divergence smaller than in the case of needle beams to form. The potential of using beams obtained by diaphragming a BLB with a wide central maximum at the second minimum of the intensity distribution for probing objects at distances up to tens of meters is demonstrated.