Journal of Applied Spectroscopy最新文献

A technique was developed to fabricate a new type of hybrid exciton-plasmonic nanostructures consisting of laterally oriented silver nanoplates electrostatically deposited on polymer films and capped with hydrophobic Zn_xCu_yIn_zS₂/ZnS quantum dot layers via a Langmuir–Blodgett technique. Pronounced photoluminescence quenching and a decrease in the average emission decay times indicated the presence of effective resonance energy transfer in the resulting hybrid plasmonic nanostructures. An approach based on a comparison of the polarization dependences of the photoluminescence bands from monolayers of quantum dots atop the quartz glass and monolayers of laterally oriented silver nanoplates was proposed to clarify the nature of the emission from these nanostructures. The data point toward a secondary emission mechanism due to scattering by transverse surface plasmons of the silver nanoplates excited through resonance energy transfer from the quantum dots.

The possibility of surface passivation of silicon by hyperdoping with Se and laser annealing was evaluated by x-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy. Silicon layers hyperdoped with Se were formed by Si implantation (140 keV, 6.1∙10¹⁵ cm^–2) followed by pulsed laser annealing (PLA) (λ = 694 nm, W = 2.0 J/cm², τ = 70 ns). The Se concentration in the subsurface region (2.0–2.5 nm) was 0.67% (3.35∙10²⁰ cm^–3). The high Se concentration could be attributed to its accumulation in the subsurface region during PLA to form Si–Se bonds. According to XPS, Se–O bonds did not form in the subsurface implanted layer during PLA. The chosen laser pulse energy density of W = 2 J/cm² allowed high structural perfection (>91%) to be achieved and a high Se concentration (>69%) at the Si lattice sites to be attained.

The synthesis and characterization of Dy³⁺-activated CaSi₂O₅ phosphor is reported. The phosphors were synthesized using a modified solid-state reaction method with variable concentrations of doping ions (0.1–2.5 mol.%) of Dy³⁺. The synthesized phosphors were characterized by X-ray diffraction (XRD) analysis and the field emission scanning electron microscopy (FESEM) technique. The XRD pattern revealed that the doped phosphors had a cubic structure. FESEM micrographs clearly indicated that the particles crystallized in inhomogeneous morphology on a micrometer scale with a sporadic and asymmetrical shape. Photoluminescence excitation and emission spectra were monitored for variable doping concentrations and the emission found at 485 and 576 nm (excited at 353 nm). The corresponding transitions of the doping ion and concentration quenching effect were studied in detail. The 1931 CIE (x, y) chromaticity coordinates (x = 0.30 and y = 0.31) showed the distribution of a spectral region calculated from PL emission spectra. On the basis of CIE analysis, the prepared phosphor is useful for white light emission in inorganic light-emitting diodes. As-synthesized phosphor was examined by thermoluminescence glow curve analysis with different doses of gamma and electron beam and corresponding kinetic parameters were calculated using the computerized glow curve deconvolution technique.

A sensitive, easy, and low-cost method used in the determination of pure forms of losartan and mebeverine hydrochloride, also in pharmaceutical preparations with derivative spectrometry using UV-Vis technology. This method depends on measuring the first derivative of the spectrum using zero cross, peak to base line, and peak area. The linear range of concentrations used was equal to 2–14 ppm for losartan, whereas for mebeverine hydrochloride it was equal to 2–16 ppm in a mixture. For losartan, in the presence of mebeverine hydrochloride, 12 ppm by utilizing peak to baseline correlation coefficients 0.9984, 0.9994, and peak area 0.9972, whereas for mebeverine hydrochloride in the presence of losartan, 12 ppm by utilizing peak to fundamental correlation coefficients 0.9952, 0.9966, 0.9957, and peak area 0.9970, 0.9971, 0.9968, 0.9971. The limit of detection for each drug, losartan and mebeverine hydrochloride, is equal to 0.0113 ppm. The accuracy and precision of the method were estimated by calculating relative standard deviation (%RSD) values less than 3% while maintaining a recovery percentage of acceptable value. The proposed method proved effective and efficient at estimating both losartan and mebeverine hydrochloride, in the presence of the other in a mixture of the two without interference, despite the closeness of their spectral absorption peaks. There are no other more accurate methods for estimating the two in a mixture than the proposed method. The proposed method is considered one of the most direct and economical methods that do not require reagents or additional materials for conducting reactions and studying the optimal conditions for those interactions. Thus, it is considered one of the green chemistry techniques that reduce the use of chemicals and reagents in the process of estimating these drugs in a mixture and in a shorter period of time. The proposed method can be used to estimate the different properties in a mixture of the two compounds whose absorption spectra are close.

Resonances of free excitons at energies A ~ 1.0409 eV, B ~ 1.0445 eV, and C ~ 1.2690 eV were detected in reflection spectra of single crystals of the direct-gap compound CuInSe₂ at a temperature of 8.6 K. The appearance of the three reflection resonances A, B, and C could be explained by removal of degeneracy from valence-band energy levels due to the influence of crystal field and spin–orbit interaction on the tetragonal lattice of CuInSe₂ with Δ_CF ~ 5.4 meV and Δ_SO ~ 224 meV. Measurements of the temperature dependence of the reflection spectra in the range 8.6–90 K showed the energies of free-exciton resonances A and B increased because of deformation of the unit cell (tetragonal stretching) of the CuInSe₂ lattice with the chalcopyrite structure. The binding energies of free excitons A and B were determined as 10.7 and 152 meV based on temperature quenching of exciton resonances A ~ 1.0409 eV and B ~ 1.0445 eV

The mechanism of photodamage of E. coli Gram-negative bacterial cells sensitized with indotricarbocyanine dye PK220 was studied upon exposure to radiation from an LED source with emission spectrum maximum wavelength λ_max = 745 nm corresponding to the long-wavelength absorption band of the dye. The intensity of the cells' own (not enhanced by activator additives) light-induced chemiluminescence was used to assess the magnitude of the photobiological effect. The main contribution to their photodestruction immediately after cessation of cell-suspension irradiation came from singlet oxygen and to a lesser extent from H₂O₂. Hydroxyl radicals did not play a significant role in the mechanism of sensitized photochemical processes.

The bactericidal components of air plasma jets generated by a direct-current glow discharge and a dielectric barrier discharge were studied using IR and UV absorption spectroscopy. The mole fractions of bactericidal components with an absorption spectrum band structure were determined by selecting a mole fraction value in the calculated spectrum that ensured correlation with the experimental spectrum. The spectra were calculated using the HITRAN spectral database and the Specair 3.0 program. The error in the mole fractions due to violation of the Bouguer–Lambert–Beer law when using absorption coefficients convoluted with the instrument function was determined. The mole fractions of bactericidal components with a continuous absorption spectrum were calculated using the Bouguer–Lambert–Beer law in a standard way. IR and UV absorption spectroscopy were shown to enable determination of the mole fractions for the full set of bactericidal components in air plasma jets of glow and barrier discharges.

The study investigates the corrosion behavior and microstructural changes in seventeenth-century cast iron cannons exhibited at the Archaeological Museum in Goa. Chipped samples from four cannons underwent analysis for surface morphology, microstructure, and elemental composition using optical microscopy, SEM-EDX, and X-ray diffraction. FTIR spectroscopy was employed to identify the molecular structure of organic compounds, metal oxides, and oxyhydroxides on the surface. The findings reveal that the pearlite matrix of the cast iron contains graphite flakes, leading to a distinctive form of graphitic corrosion on the cannon surface. Highly localized graphitic corrosion areas on the surface have resulted in pits or series of pits, posing a potential risk to the structural integrity of the cannons over time. The study identifies the presence of chloride as a contributing factor to the corrosion process, working in tandem with graphitic corrosion of the cast iron. Understanding these corrosion mechanisms is crucial for developing strategies to ensure the long-term preservation of these historical artefacts.

Nickel nanoparticles were synthesized at room temperature by a one-step method of chemical reduction of Ni ions from NiCl₂∙6H₂O using NaBH₄. The microstructure of the nanoparticles was studied by x-ray diffraction, Raman spectroscopy, and scanning and transmission electron microscopy. An analysis of x-ray diffraction and Raman spectroscopy data showed that the obtained nanoparticles had the cubic metallic Ni structure with a crystallite size (coherent scattering region) of 3–6 nm. Studies of the morphology indicated that the Ni nanoparticles were spherical in shape and in contact with each other to form large agglomerates of nanograins.

To achieve consistent color reproduction of printed products and accurate measurement the content of mixed ink has always been an important research topic in the printing industry. This paper proposes a spectral-based method for measuring the content of dual-color mixed printing ink, aiming to solve the difficulty in determining the specific content of the base color in the same ratio of dual-color ink by using spectral analysis. First, a composite filtering method combining median filtering and wavelet transform was compared and selected for spectral preprocessing. Then, three methods, namely the successive projections algorithm (SPA), competitive adaptive reweighted sampling method (CARS), and stable competitive adaptive weighted sampling method (SCARS), were used to extract feature wavelengths from the preprocessed information. Based on partial least squares regression (PLSR), four models, PLSR, SPA–PLSR, CARS–PLSR, and SCARS, were established for predictive analysis. To further test the model, the SCARS–PLSR model was used for predictive analysis of magenta-cyan, yellow-magenta, and yellowcyan binary samples with a mass fraction ratio of 0.5. The results showed that the SCARS–PLSR model has the best predictive performance, with RMSE and R² values of 0.0052, 0.0002, 0.0004 and 0.9989, 0.9999, 0.9999, respectively. This indicates that this study can accurately determine the content of dual-color ink by spectral analysis.