Vibrational Spectroscopy最新文献

Cannabidiolic acid (CBDA) is found in cannabis as genuine phytocompound of the well-known non-psychoactive cannabinoid - cannabidiol (CBD), notable for its various therapeutic purposes. Decarboxylation of CBDA to CBD is commonly used in the production of finished cannabis products, thus increasing its bioavailability, and making it more effective for various therapeutic purposes. Optimization of decarboxylation time and the possibility of monitoring this process in real-time is quite a challenge for the cannabis producers' R&D divisions, since incomplete decarboxylation is associated with quality and efficiency concerns, whereas prolonged reaction time can lead to potentially lower production efficacy. The purpose of this study is to emphasize the use of mid-infrared (MIR) spectroscopy for in-situ real-time monitoring and understanding of the CBDA decarboxylation process. For the first time, the TG/DTG curves of CBDA provided insights into the solid-solid decarboxylation dynamics, process endpoint, and maximal conversion rate temperature, which were used for designing the subsequent infrared experiments. In addition, the DSC curve illustrated the melting point of the pure CBDA. Temperature-controlled infrared spectroscopy studies were performed on CBDA standard and cannabis flowers followed by precise band assignment and spectra-structure correlations based on the idea of functional group vibrations. In order to investigate the spectral regions of major relevance for the CBDA to CBD interconversion process, a principal component analysis (PCA) was used. In the obtained models, PC1 was capable to describe 81.3 %, 77.8 % and 77 % of the total spectral fluctuations in the CBDA standard and two plant samples, respectively. The PC1 score plot of the CBDA standard (as a function of temperature) showed a perfect complementarity to the TG/DTG curve, indicating that PC1 of the MIR spectrum model may quantitatively describe the CBDA decarboxylation dynamics, which allowed for the derivation of decarboxylation rate constants for the CBDA standard and the plant material at prechosen temperatures. The temperature-controlled experiments revealed significantly higher kinetics constants of CBDA decarboxylation in the plant material compared to the CBDA standard and supported the assumption that the complex matrix in cannabis plants accelerates the conversion of CBDA to CBD. In this way, progress in the development and optimization of an efficient and fast approach for monitoring and elucidation of the phytocannabinoid decarboxylation process was made, launching the possibility for further employment in the medical cannabis industry.

The utilization of the soil pedotransfer functions (PTFs) developed based on the basic soil propertied is an alternative, fast, cost-effective and applicable approach for the prediction of field capacity (FC) and permanent wilting point (PWP). In addition, the Visible–Near-Infrared (Vis-NIR) spectra in soil science has gained prominence due to its practicality and relevance. In this paper, we used the data of the soil PWP and FC of 135 soil samples, easily measurable soil properties and Vis-NIR spectroscopy. The multiple linear regression (MLR) model was utilized to formulate PTFs model and Vis-NIR spectroscopy combined with MLR and partial least-squares (PLSR) was used to develop Spectrotransfer Function (STF). Results showed that among the easily measurable soil properties, particle-size diameter (dg) with Beta of −0.72 and −0.63 the most influential parameters for predicting FC and PWP, respectively, followed by the clay content. Developed PTFs for both FC and PWP with a R² of 0.71 and 0.68, respectively, had a better performance than other previous developed PTFs. Results also revealed that the PLSR with a higher R² (0.81) and lower RMSE (4 %) significantly performed better in comparison to STF for both FC and PWP prediction.

To characterize a mixture of powders using several analytical techniques, it is necessary that successive analyses be carried out on well-identified and localized particles, so that each characterization corresponds to a given powder. In this publication, powdered nuclear materials are characterized at the morphological and elemental levels with a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and at the chemical level with a micro-Raman spectrometer (MRS). However, to avoid a time-consuming and insufficiently accurate microparticle relocation process between SEM/EDS and MRS, micro-Raman analyses are carried out inside the SEM using a coupling device. In this way, all three pieces of information are obtained for exactly the same micrometric spot, without moving the sample or relocating the microparticles analyzed. The information can therefore be combined to characterize each component of the mixture. In this article, we describe in detail the methodology we have developed and optimized for morphological, elemental and chemical analysis of microparticles using a combined SEM/EDS and SRM. This methodology has been applied to powdered nuclear materials in two international nuclear forensics exercises. In the first exercise, named CMX-6, the combined use of the two instruments identified the presence of PuO₂ microparticles and several uranium compounds (UO₂, U₃O₈, UO₂F₂) in both materials. In the second exercise, called CMX-7, the methodology developed enabled us to distinguish two chemical phases of uranium, a uranyl oxy-hydroxide and a uranyl nitrate, each characterized by specific morphologies and the detection or non-detection of a minor elemental constituent (calcium).

In this study, the mineralogical composition of 284 sherds obtained from the sites of Yeşilova Höyük and Yassıtepe Höyük, two of the oldest settlements in Western Anatolia, and corresponding to a wide period starting from the Neolithic period to the Chalcolithic and Early Bronze Age (EBA), was studied by attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy. FTIR data was used to classify the sherds and state their firing conditions as a result of determining their mineralogical composition using principal component analysis (PCA), multivariate curve resolution (MCR), and hierarchical cluster analysis (HCA). According to the PCA results, the second-order derivative FTIR spectrum with 19 smoothing points in the range of 1300–400 cm⁻¹ was determined to be the most successful model in classifying sherds. As a result of MCR, which allows comparison of standard minerals obtained within the scope of the study, it was determined that kaolinite, illite, chlorite, and some feldspar types were dominant in the sherds. According to HCA analysis, all sherds except five of them exhibited a similar mineralogical structure. According to the derivative spectra, it was seen that the sherds had a composition consisting of kaolinite, illite, hematite, chlorite, and some feldspar types at different rates. Upon examining the data, it becomes evident that the sherds are composed of nearly identical minerals and might have been fired in an oxidizing atmosphere. Even while 279 sherds had many mineralogical traits, N-061, EB-030, N-043, C-068, and N-059 were found to have distinct proportions of comparable minerals, including more kaolinite, illite, calcite, and chlorite. Regarding color, additives, and the amount of ceramic pastes present, these five sherds differ from the others. This suggests that there might have been attempts at manufacture or pots brought in from outside the Yeşilova Höyük-Yassıtepe Höyük sites. The results provided from the derivative spectra showed that all sherds except five of them have been fired at about at temperatures slightly above 450–500 °C due to their relatively low kaolinite character, but below 800 °C because diopside and similar high-temperature minerals could not be detected. The five sherds may have been fired at a temperature of around 450–500 °C due to the presence of a high character of kaolinite, illite, and chlorite. It was understood that the residents of the sites of Yeşilova Höyük and Yassıtepe Höyük produced their ceramics using the same raw materials and the same production methods from the Neolithic period to EBA thanks to FTIR and chemometrics, which are very good tools for analyzing large numbers of sherds with low cost and fast analysis time.

During the last decades, Fourier-transform infrared spectroscopy (FTIR) with attenuated total reflectance (ATR) has gained a substantial role in monitoring structural changes of proteins. The conformation of the polypeptide backbone, reflecting the pattern of intramolecular hydrogen bonding, affects the vibrational energy of carbonyl groups and, consequently, the absorption of infrared light. Specifically sensitive to the conformational state of a polypeptide is the Amide I region (1700–1600 cm⁻¹), whose individual bands correlate with distinct secondary structures. ATR-FTIR thus provides the possibility to determine secondary structure content by deconvolution of the Amide I region, which makes it a valuable tool for investigating protein structure. Furthermore, the sensitivity of the Amide I band to subtle differences in hydrogen bonding enables discrimination between different β-sheet conformations, including intramolecular and intermolecular β-sheet. Compared to other methods for secondary structure determination, such as circular dichroism, this advantage makes infrared spectroscopy an excellent tool for monitoring aggregation processes. This review is intended to explain the principle of FTIR, the specificities of protein FTIR spectroscopy, to correlate the spectra with the protein secondary structure, and to provide different approaches for spectral analysis. To highlight FTIR contribution as a reliable parameter in protein structural analysis, here we review the data regarding the determination of the secondary structure of native globular proteins, the monitoring of discrete conformational changes upon destabilizing treatments, and the monitoring of structural changes in the aggregation process.

The vibrational spectrum of the vapour phase above YI₃ was measured by infrared spectroscopy. The spectrum revealed four strong bands, three of which could be assigned to the fundamantal infrared active vibrations of the YI₃ monomer molecule. The observed frequencies agree very well with quantum-chemical calculations reported in literature. The presence of dimer molecules, the fraction of which is significant in the vapour according to literature, is also discussed in the context of assigning the fourth strong band in the experimental spectrum. Although its position matches well with a strong fundamental of the dimer, its intensity suggest a dimer fraction that is far outside the range for the other rare-earth triiodides.

Numerous illnesses progress silently, often reaching a critical stage by the time symptoms appear, making medical intervention difficult. While there exist sophisticated clinical techniques for precise disease detection, they are often invasive procedure and as a rule of thumb is used only with definite symptomatic cases. In addition, the extreme clinical costs prevent a large population from taking advantage of contemporary medical facilities. A non-invasive, economically feasible screening method that detects diseases even in their pre-symptomatic stages may overcome many critical challenges in health and medicine. Utilizing vibrational spectroscopy to identify volatile metabolites offers promise as such a non-invasive, cost-effective diagnostic tool. The article outlines the potential of vibrational spectroscopy for non-invasive diagnostics and proposes a method for its clinical implementation.

In near-infrared spectroscopy analysis, the predictive performance of models may degrade due to variations in the measurement environment and sample properties. Maintenance or updates to the model are essential to uphold prediction accuracy. The state-of-the-art approach for model updates involves labeling new samples and incorporating them into the calibration set. However, this strategy leads to an escalating size of the calibration dataset, and the low ratio of new samples renders the model update process inefficient. To enhance update efficiency, a size-stable updating strategy is presented which involves the simultaneous addition of new samples and removal of old samples. This is achieved by utilizing the new set as a basis for identifying and deleting significantly different old labeled samples. To improve labeling efficiency, a batch mode update is employed. Initially, calibration samples are clustered to yield multiple clusters with comparable sizes to the new update set. Subsequently, differences between multiple old sample clusters and the new set are calculated. The old sample cluster that most different are removed, accompanied by the addition of the new sample set to maintain calibration set size stability. In calculating set similarity, a multi-indices fusion method is employed to ensure accurate judgments. The efficacy of this method is validated through simulated and real data.

The synthesis of TiO₂ nanotubes film decorated with Ag nanoparticles (TiO₂NTs/AgNPs) and its potential applicability as a SERRS (Surface-Enhanced Raman Resonance Scattering) substrate for detection and speciation of anthocyanins species in grape skin extracts is reported. Preliminary spectrophotometric analysis in the UV–Vis region allowed to identify the maximum absorption bands at 527 and 620 nm, related to the flavylium cation (AH⁺) and quinoidal base (A^–), respectively. The increase in the ratio AgNPs/extract concentration in colloidal solutions of AgNPs promoted the intensification of the vibrational modes of anthocyanins species, due to the SERRS effect. From deconvolutions of these SERRS spectra, a linear relationship (R² = 0.993) for the intensity ratio of the vibrational modes A^–/AH⁺ (i.e., for the ratio 1631–1640/1648–1659 cm^–1) as a function of the grape skin extract dilutions at colloidal solutions of AgNPs was found. The deposition of the extracts onto TiO₂NTs/AgNPs surface promoted an additional SERRS signal intensification for A^– in detriment to AH⁺. The deconvolution of these SERRS spectra showed again a linear relationship (R² = 0.999) between the intensity bands ratio A^–/AH⁺ and grape skin extract dilutions in the range of 0.1–1.0 %. The SERRS technique using the TiO₂NTs/AgNPs substrate was more sensitive for anthocyanins quantification compared to the spectrophotometric one. The results revealed that the TiO₂NTs/AgNPs films are versatile, efficient, and promising platforms for SERRS quantification and speciation of anthocyanin species in situ.