Journal of Applied Spectroscopy最新文献

An approach based on a combination of elemental, mineralogical and structural analyses is used to characterize several samples of marble and ornamental rocks taken from different regions of Morocco. Each of these rocks has its own characteristics, with a variety of colors (gray, white, pink, black, yellow, red, brown, etc.). Three samples of white marble from Carrara (Italy), Drama and Kozani (Greece) were studied under the same conditions to serve as references. A sample of white marble from the Moulay Ismail Mausoleum in Meknes (18th century) was also studied under the same conditions in order to identify its quarry of origin. These marbles were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), and micro-Raman spectroscopy. XRF was used to determine the elemental composition of the samples. Major and minor crystalline phases were identified using XRD and micro- Raman spectroscopy.

Graphene samples with various numbers of layers and their relative rotation in the graphene plane were obtained by chemical vapor deposition on a copper catalyst. The properties of the obtained graphene structures were revealed by Raman spectroscopy. The position and shape of the main peaks changed depending on the number of layers and their rotation, which indicated a change in the nature of the interaction between the layers. Additional peaks were studied as a function of the twist angle of the graphene layers. Determining the distinctive characteristics of the studied twisted structures is a necessary step in optimizing the scalable synthesis and production of graphene-based nanoelectronic devices.

Multivariate classification models of the geographical origin of herbal medicines are developed based on terahertz time-domain absorption spectroscopy. Four methods of cluster analysis are considered: hierarchical cluster analysis, k-means, k-nearest neighbors, and classification trees. Twelve spectral variables in the frequency range 0.1–0.6 THz have been selected for classification of five geographical locations of Gastrodia roots in decreasing order of their standard deviation in the explored set and transformed to a six-dimensional principal component space with the Mahalanobis metric. Classification of the considered herbal medicines by two nearest neighbors in this space is characterized by an accuracy and precision of 0.98, and a sensitivity of 0.982.

An investigation was carried out on the fluorescent properties of nanoparticles made by a hydrothermal method from an ethanolic extract of mulberry leaves. Our analysis confirmed the presence of carbon dot nanostructures exhibiting fluorescence emission peaking at 670 nm (excited at 405 nm) with a quantum yield of 45%. Photobleaching of the nanoparticles upon quasi-continuous excitation at 405 nm was observed with 10–20 s irradiation. Without illumination, partial fluorescence recovery was detected consisting of several percent within one minute and over 25% after 16 h in darkness. Comparative spectral analysis of the initial leaf extract and the synthesized red-luminescent carbon dot fraction revealed similarities, suggesting the presence of unbound organic molecules with chromophore groups in the medium. The chromophores were found to accumulate in erythrocyte membranes, enabling cell visualization. However, these chromophores were found to be both cytotoxic and phototoxic. Thus, the synthesis of carbon dots from multicomponent plant extracts may result in incomplete carbonization and degradation of the chromophores, which can significantly alter our interpretation of the optical properties of these nanostructures.

X-Ray photoelectron and luminescence spectroscopy was used for studying heteroligand compounds of neodymium(III) with either trifluoroacetic or cinnamic acid as well as nitrogen- and phosphorus-containing neutral ligands. Tendencies toward increased electron density on the neodymium ion and enhanced relative intensity of the band for the ⁴F_3/2–⁴I_11/2 transition are seen upon coordination of the neutral ligands by means of the donor nitrogen atom in similar groups of compounds. The strongest luminescence was found for the complex of neodymium(III) cinnamate with 1,10-pheanthroline.

Zeolite’s possession of Brønsted acid sites and impregnated metals in its pores renders it highly advantageous for catalytic transformations that necessitate the presence of both metallic and acidic active sites such as hydroisomerization and hydrocracking reactions. This study explores the influence of cobalt (Co) and molybdenum (Mo) impregnation on the structural and acidic properties of zeolite Y. A series of CoMo–zeolite Y catalysts was synthesized using the wet impregnation method with varying metal concentrations. Characterization using X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR), and pyridine–FTIR revealed that the introduction of Co and Mo modified the distribution and strength of Brønsted and Lewis acid sites, while the crystallinity of the zeolite Y framework was preserved. Notably, the Co₆Mo catalyst exhibited an optimal Lewis/Brønsted acid ratio, highlighting the potential of these materials for bifunctional catalytic applications. These findings contribute to understanding the interplay between metal loading and acid properties, laying the groundwork for future studies on catalytic performance.

The possibility of applying the quantum fluctuation theorem (QFT) to deep-lying electron orbitals in experimental atomic photon ↔ electron transition cross-section spectra is considered. Such spectra can only be obtained as a function of the difference between the experimentally measured excitation energy and final state energy. It is shown that spectra in this function do not satisfy the QFT. An assumption is made that the cross-section spectra are changed by screening of the transition excitations by an ensemble of neighboring electrons (orbitals). A screening coefficient that is constant across the observed spectrum and accounts for the reduction of the excitation energy (cross section) to the elementary starting state due to the screening is introduced into the QFT relations for such transition cross-sections. The spectra satisfy the QFT relations if screening is considered. Calculations using these assumptions are applied to electron x-ray photoemission spectra, inverse x-ray photoemission spectra, and electron energy loss (absorption) spectra. It is found that screening weakens the non-valence atomic orbital transition cross section by an order of magnitude or more, but only by several times for the outer (valence) ones. It was found that identification of the purely electronic transition position using QFT relations from the observed spectrum depended on the screening coefficient.

Two-dimensional NMR spectroscopy was used to assign the hydrogen and carbon signals in the spectra of glycyrrhizic acid, the monoammonium salt of glycyrrhizic acid, lagochirzine, lagochilin, as well as tetraacetyl and isopropylidene derivatives of lagochilin in various solvents. These compounds were studied by tandem mass spectrometry in ESI and APCI modes.

Mural painting is the earliest independent form of painting and involves the crystallization of ancient traditional painting arts. However, over time, various types of deterioration have influenced murals, among which the most common is the deterioration of the plaster layer. Existing extraction methods largely use the shape features obtained from digital images, which are influenced by the diversity of information on the murals. To overcome this drawback, hyperspectral technology was introduced to achieve accurate deterioration extraction. First, the spectral features of deterioration, with a focus on the plaster layer, were analyzed. The decision tree deterioration index was subsequently constructed to extract deterioration information. Combining the threshold of the near-infrared reflectance and the difference between the reflectance at 440 and 490 nm, our method was effective for complete extraction. The method achieved better visual results than other traditional extraction methods did. The precision, recall, F-measure, and overall accuracy were 0.7244, 0.7581, 0.7409, and 0.9680, respectively. Our method also has high threshold stability, yielding good results for other mural images.

A complex analysis of the antioxidant properties of four epiphytic lichen species from the Parmeliaceae Zenker family with different anthropo-tolerance has been carried out. The antioxidant activity and the contents of phenolic compounds (PC) and carotenoids have been determined in Evernia divaricata (L.) Ach., E. prunastri (L.) Ach., Hypogymnia physodes (L.) Nyl., and H. tubulosa (Schaer.) Hav. using DPPH, FRAP, and ABTS methods. Correlation analysis showed a close relationship between the PC and carotenoids and the antioxidant activity (AOA). A multi-parameter biochemical sensitivity index (MPBSI) based on normalization of the values of these biochemical parameters has been calculated. The tolerance of species resistant to anthropogenic pollution was due to higher concentrations of PC and carotenoids and higher AOA. The MPBSI of Hypogymnia physodes was 8.43; of Evernia prunastri, 6.38. Species sensitive to various anthropogenic impacts were characterized by lower values of these parameters. The MPBSI of Hypogymnia tubulosa was 5.83; of Evernia divaricata, 1.56. The degree of the decrease in the MPBSI correlated with the level of vulnerability due to vegetation transformation resulting from woodland fragmentation, which led to changes in the microclimate. Photoprotection in Evernia species that have a bushy biomorph was due to a higher concentration of carotenoids. An increase in antioxidant activity in Hypogymnia representatives with leafy thalli was due to an increase in the PC content. A complex approach to the assessment of the biochemical parameters related to the antioxidant properties, with the determination of the values of the MPBSI index, was interesting for the further development of biomonitoring studies. This approach would make it possible to delve into the scales of anthropo-tolerance and would help clarify the mechanisms of adaptation of lichens to different types of anthropogenic impacts.