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Knowledge of the reaction mechanism is key for rational catalyst improvement. Traditionally mechanistic studies focus on structure and the reaction conditions like temperature, pH, pressure, etc. whereas the time dimension is often overlooked. Here, we demonstrate the influence of time on the mechanism of a catalytic reaction. A dual catalytic mechanism was identified for the CO oxidation over Au/TiO2 by time‐resolved infrared spectroscopy coupled with modulation excitation spectroscopy. During the first seconds, CO on the gold particles is the only reactive species. As the reaction proceeds, the redox properties of TiO2 dominate the catalytic activity through electronic metal‐support interaction (EMSI). CO induces the reduction and reconstruction of TiO2 whereas oxygen leads to its oxidation. The activity of the catalyst follows the spectroscopic signature of the EMSI. These findings demonstrate the power of studying short‐time kinetics for mechanistic studies. [ABSTRACT FROM AUTHOR]

Vibrational spectroscopy is one of the most well-established and important techniques for characterizing chemical systems. To aid the interpretation of experimental infrared and Raman spectra, we report on recent theoretical developments in the ChemShell computational chemistry environment for modelling vibrational signatures. The hybrid quantum mechanical and molecular mechanical approach is employed, using density functional theory for the electronic structure calculations and classical forcefields for the environment. Computational vibrational intensities at chemical active sites are reported using electrostatic and fully polarizable embedding environments to achieve more realistic vibrational signatures for materials and molecular systems, including solvated molecules, proteins, zeolites and metal oxide surfaces, providing useful insight into the effect of the chemical environment on the signatures obtained from experiment. This work has been enabled by the efficient task-farming parallelism implemented in ChemShell for high-performance computing platforms. This article is part of a discussion meeting issue 'Supercomputing simulations of advanced materials'. [ABSTRACT FROM AUTHOR]

Water is an ubiquitous liquid that has several exotic and anomalous properties. Despite its apparent simple chemical formula, its capability of forming a dynamic network of hydrogen bonds leads to a rich variety of physics. Here we study the vibrations of water using molecular dynamics simulations, mainly concentrating on the Raman and infrared spectroscopic signatures. We investigate the consequences of the temperature on the vibrational frequencies, and we enter the details of the hydrogen bonding coordination by using restrained simulations in order to gain quantitative insight on the dependence of the frequencies on the neighbouring molecules. Further we consider the differences due to the different methods of solving the electronic structure to evaluate the forces on the ions, and report results on the angular correlations, isotopic mixtures HOD in H2O/D2O and and the dielectric constants in water. [ABSTRACT FROM AUTHOR]

Current screening methods for diabetic kidney disease (DKD), characterized by albumin excretion in urine, are expensive or only identify patients in late disease stages. Hence, there is need for a cost‐effective, quick, and portable screening tool which identifies patients at DKD onset. Here we report that ultracentrifugation coupled with infrared spectroscopy and machine learning can identify and quantify low level microalbuminuria in urine samples from a cohort of diabetic patients (n=155) and controls (n=22). Independent testing of the methods indicated that classification analysis discriminated between normo‐ and micro/macroalbuminuric samples with sensitivity of >91 % and specificity of >99 %. Regression methods quantified albumin concentration in the samples with error values of 17 and 44 mg/L for normo‐ and microalbuminuric patients. Using only 700 μL of sample, this approach identifies patients at an earlier stage of disease than a urinary dipstick, whilst also yielding results cheaper and faster than the albumin to creatinine ratio. [ABSTRACT FROM AUTHOR]

Some problems of vibrational spectroscopy of particles in condensed systems are considered in this work. One of the aspects of theoretical research is the study of the vibrational properties of individual particles in view of the nano-dimension of the molecules of the condensed system surrounding the particle. Using the apparatus of temperature, Green functions of the operators of polarization of condensed systems, two main mechanisms of influence on impurity particles from the medium, solvation and fluctuation, are distinguished. Theoretical results are obtained within the framework of these two mechanisms for calculating changes in the vibrational spectrum of individual particles. The theoretical results are used to analyze the experimental data on the vibrational spectra of the N2O molecule in polar solvents: methanol, ethyl alcohol, acetone, and 1,2-dichloroethane. [ABSTRACT FROM AUTHOR]

The aqueous solubility of solid-state pharmaceuticals can often be enhanced by cocrystallization with a coformer to create a binary cocrystal with preferred physical properties. Greater understanding of the internal and external forces that dictate molecular structure and intermolecular packing arrangements enables more efficient design of new cocrystals. Low-frequency (sub-200 cm−1) Raman spectroscopy experiments and solid-state density functional theory simulations have been utilized together to investigate the crystal lattice vibrations of mycophenolic acid, an immunosuppressive drug, in its pure form and as a cocrystal with 2,2′-dipyridylamine. The lattice vibrations primarily consist of large-amplitude translations and rotations of the crystal components, thereby providing insights into the critical intermolecular forces governing cohesion of the molecular solids. The simulations reveal that despite mycophenolic acid having a significantly unfavorable conformation in the cocrystal as compared to the pure solid, the cocrystal exhibits greater thermodynamic stability over a wide temperature range. The energetic penalty due to the conformational strain is more than compensated for by the strong intermolecular forces between the drug and 2,2′-dipyridylamine. Quantifying the balance of internal and external energy factors in cocrystal formation indicates a path forward in the development of future mycophenolic acid cocrystals. [ABSTRACT FROM AUTHOR]

Abstract Background Oleaginous fungi have versatile metabolism and able to transform a wide range of substrates into lipids, accounting up to 20–70% of their total cell mass. Therefore, oleaginous fungi are considered as an alternative source of lipids. Oleaginous fungi can accumulate mainly acyl glycerides and free fatty acids which are localized in lipid droplets. Some of the oleaginous fungi possessing promising lipid productivity are dimorphic and can exhibit three cell forms, flat hyphae, swollen hyphae and yeast-like cells. To develop sustainable targeted fungal lipid production, deep understanding of lipogenesis and lipid droplet chemistry in these cell forms is needed at multiscale level. In this study, we explored the potential of infrared spectroscopy techniques for examining lipid droplet formation and accumulation in different cell forms of the dimorphic and oleaginous fungus Mucor circinelloides. Results Both transmission- and reflectance-based spectroscopy techniques are shown to be well suited for studying bulk fungal biomass. Exploring single cells with infrared microspectroscopy reveals differences in chemical profiles and, consequently, lipogenesis process, for different cell forms. Yeast-like cells of M. circinelloides exhibited the highest absorbance intensities for lipid-associated peaks in comparison to hyphae-like cell forms. Lipid-to-protein ratio, which is commonly used in IR spectroscopy to estimate lipid yield was the lowest in flat hyphae. Swollen hyphae are mainly composed of lipids and characterized by more uniform distribution of lipid-to-protein concentration. Yeast-like cells seem to be comprised mostly of lipids having the largest lipid-to-protein ratio among all studied cell forms. With infrared nanospectroscopy, variations in the ratios between lipid fractions triglycerides and free fatty acids and clear evidence of heterogeneity within and between lipid droplets are illustrated for the first time. Conclusions Vibrational spectroscopy techniques can provide comprehensive information on lipogenesis in dimorphic and oleaginous fungi at the levels of the bulk of cells, single cells and single lipid droplets. Unicellular spectra showed that various cell forms of M. circinelloides differs in the total lipid content and profile of the accumulated lipids, where yeast-like cells are the fatty ones and, therefore, could be considered as preferable cell form for producing lipid-rich biomass. Spectra of single lipid droplets showed an indication of possible droplet-to-droplet and within-droplet heterogeneity.

From the moment of production, artworks are constantly exposed to changing environmental factors potentially inducing degradation. Therefore, detailed knowledge of natural degradation phenomena is essential for proper damage assessment and preservation. With special focus on written cultural heritage, we present a study on the degradation of sheep parchment employing accelerated aging with light (295–3000 nm) for one month, 30/50/80% relative humidity (RH) and 50 ppm sulfur dioxide with 30/50/80%RH for one week. UV/VIS spectroscopy detected changes in the sample surface appearance, showing browning after light-aging and increased brightness after SO2-aging. Band deconvolution of ATR/FTIR and Raman spectra and factor analysis of mixed data (FAMD) revealed characteristic changes of the main parchment components. Spectral features for degradation-induced structural changes of collagen and lipids turned out to be different for the employed aging parameters. All aging conditions induced denaturation (of different degrees) indicated by changes in the secondary structure of collagen. Light treatment resulted in the most pronounced changes for collagen fibrils in addition to backbone cleavage and side chain oxidations. Additional increased disorder for lipids was observed. Despite shorter exposure times, SO2-aging led to a weakening of protein structures induced by transitions of stabilizing disulfide bonds and side chain oxidations. [ABSTRACT FROM AUTHOR]

Background: Plastic is one of the most widely used materials worldwide in various fields, including packaging and agriculture. Its large quantities require proper disposal and for this reason more and more attention is paid to the issue of degrading plastic. Thanks to the production of non-specific enzymes, fungi are able to attack complex and recalcitrant xenobiotics such as plastics. In recent years, several spectroscopic methods were used to study the plastic degradation ability of different fungal species. Among these, Fourier transform infrared (FT-IR) and FT-Raman spectroscopy techniques are the most used. Surface-enhanced Raman scattering (SERS) spectroscopy is a powerful technique which uses metal nanoparticles (NPs) to enhance the Raman signal of molecules adsorbed on the NPs surface. In this work, the isolation of different fungi from field-collected plastic debris and the ability of these isolates to growth and colonizing the low-density polyethylene (LDPE) were explored by using scanning electron microscope (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and SERS spectroscopies. Results: Forty-seven fungal isolates belonging to 10 genera were obtained; among them only 11 were able to grow and colonize the LDPE film. However, after 90 days trial, only one isolate of Cladosporium cladosporioides (Clc/1) was able to carry out the initial degradation of the LDPE film. In particular, based on SEM observations, small cavities and depressed areas of circular shape were visible in the treated samples. Additionally, ATR-FTIR, normal Raman and SERS analyses supported the structural changes observed via SEM. Notably, ATR-FTIR and normal Raman spectra showed a significant decrease in the relative intensity of the methylene group bands. Similarly, the SERS spectra of LDPE after the fungal attack, confirmed the decrease of methylene groups bands and the appearance of other bands referring to LDPE polyphenolic admixtures. Conclusions: These results suggest that Cladosporium cladosporioides Clc/1 is able to carry out an initial degradation of LDPE. Moreover, combining ATR-FTIR, Raman and SERS spectroscopies with SEM observations, the early stages of LDPE degradation can be explored without any sample pretreatment. [ABSTRACT FROM AUTHOR]

Since their approval for use in aquaculture in 2017, processed insect proteins have been extensively studied for their nutritional quality in animal feed. This new type of meal is highly promising but requires, as for other products used in animal feed, strict sanitary control in accordance with European legislation. Within this legal framework, light microscopy and PCR remain the official methods but have some analytical limitations that other methods could overcome. This paper aims to provide an overview of the European legislation concerning use of processed insect proteins, but also to highlight the advantages and disadvantages of the official methods for their analysis. It also points out other analytical methods, which have already proved their worth for the analysis of processed animal proteins, which could be used as complementary methods. [ABSTRACT FROM AUTHOR]

Ultraviolet-induced photodissociation and photo-isomerization of the three most stable conformers (SSC, GAC, and AAT) of glycolic acid are investigated in a low-temperature solid argon matrix using FTIR spectroscopy and employing laser radiation with wavelengths of 212 nm, 226 nm, and 230 nm. The present work broadens the wavelength range of photochemical studies of glycolic acid, thus extending the understanding of the overall photochemistry of the compound. The proposed kinetic model for the photodissociation of glycolic acid proceeds from the lowest energy conformer (SSC). The model suggests that ultraviolet light induces isomerization only between the SSC and GAC conformers and between the SSC and AAT conformers. The relative reaction rate coefficients are reported for all proposed reactions. These results suggest that the direct photodissociation of GAC and AAT conformer does not occur in an argon matrix. The main photodissociation channel via the SSC conformer produces formaldehyde–water complexes. The proposed photodissociation mechanism emphasizes that the conformers' relative abundancies can significantly affect the photodissociation rate of the molecule. For example, in the case of high relative GAC and AAT concentrations, the ultraviolet photodissociation of glycolic acid requires the proceeding photo-isomerization of GAC and AAT to SSC. [ABSTRACT FROM AUTHOR]

Mullite-type Bi2(FexGa1-x)4O9 (0 ≤ x ≤ 1) oxides, prepared by mecanochemical-thermal synthesis, were investigated by FTIR and Raman spectroscopies. Similarly to other mullite systems, IR (850–400 cm−1) and Raman bands (750–300 cm−1) are attributed to stretching and bending vibrations of tetrahedral and octahedral sites. A shift in the peak positions toward lower wavenumbers with the increase of iron content is observed. High-energy IR modes show only the presence of Ga-O-Ga and Ga-O-Fe/Fe-O-Ga stretching vibrations for x < 0.5. Raman bands between 500 cm−1 and 400 cm−1 revealed double band splitting for x < 0.5. [ABSTRACT FROM AUTHOR]

In order to investigate the effectiveness of vibrational spectroscopy in the characterization of polymer piezoelectric materials, poly(vinylidene fluoride) (PVDF) samples are carefully studied. The characterizations are performed by using different Fourier transform infrared sampling techniques, i.e. transmission (FTIR), attenuated total reflectance (FTIR-ATR) and photoacoustic spectroscopy (FTIR-PAS). The attenuated total reflectance (ATR) and photoacoustic (PAS) sampling methods allow us to study the IR spectra for thick piezoelectric samples. To the best of our knowledge, it has been determined for the first time the relative fractions of the β phase, F(β), in PVDF by FTIR-PAS. [ABSTRACT FROM AUTHOR]

The surface structure of oxide‐supported metal nanoparticles can be determined via characteristic vibrations of adsorbed probe molecules such as CO. Usually, spectroscopic studies focus on peak position and intensity, which are related to binding geometries and number of adsorption sites, respectively. Employing two differently prepared model catalysts, it is demonstrated that polarization‐dependent sum‐frequency‐generation (SFG) spectroscopy reveals the average surface structure and shape of the nanoparticles. SFG results for different particle sizes and morphologies are compared to direct real‐space structure analysis by TEM and STM. The described feature of SFG could be used to monitor particle restructuring in situ and may be a valuable tool for operando catalysis. [ABSTRACT FROM AUTHOR]

Preserving and analytically examining daguerreotypes is particularly challenging because of their multi-material and multi-component structure. Various sensors have been exploited to examine mainly the image plates of the daguerreotypes even though the degradation goes beyond this component. Micro-analyses have been the preferred method due to the nanoscale structure of the image particles. In this work, we propose comprehensive multi-modal non-invasive sensing to investigate the corrosion products present in nine daguerreotypes from the Fondazione Alinari per la Fotografia (FAF, Florence, Italy). The methodology proposed includes chemical and morphological analyses: portable X-ray fluorescence spectrometry (pXRF), Raman microspectroscopy (μ-Raman), and micro-Fourier transform infrared spectroscopy in reflection mode (μ-rFTIR) for the chemical identification. For the first time, optical coherence tomography (OCT) was deployed to record the cross-sectional and morphological data of the relevant corrosion formations on daguerreotypes in a contactless way. The results allowed the characterization, in a non-invasive mode at a microscopic level, of a wide range of degradation products produced by the interaction of the different elements present in the structure of the daguerreotypes. The aim was to verify the performance of the proposed methodology and to link the chemical and physical complexity of the entire structure, disclosed by the state-of-art sensors, to the daguerreotype degradation. The results draw attention to the need to monitor not only the image condition but the whole object as a partially closed system in constant interaction internally and with the environment. [ABSTRACT FROM AUTHOR]

Skin surface lipid (SSL) film is a mixture of sebum and epidermal lipids protecting the skin from the effects of the environment such as solar radiation. SSLs are a suitable target and scavenger for all reactive oxygen species (ROS) generated in the skin. In the SSLs, vitamin E has been identified as one of the main antioxidants that can capture ROS. This paper is the third part of a global study that evaluates the effect of solar radiation on the lipid classes that constitute SSLs. In the first two parts, the effect of solar radiation on fatty acids and triglycerides was studied using vibrational spectroscopy. In this part, the effect on the other lipid classes such as squalene (SQ), cholesterol (Chol), and wax ester (WE) (Palmitoleyl Palmitate) was studied and then the behavior of vitamin E under solar radiation was monitored. Finally, SSLs were irradiated and analyzed using vibrational spectroscopy and HT‐GC/MS to respectively follow the oxidation process and to identify the first target of solar radiation in SSLs. When irradiated alone, SQ oxidation process was detectable only after 2430 J/cm2 dose. Similar observations were obtained for vitamin E (after 1620 J/cm2). No changes were observed on the cholesterol and on the wax ester (Palmitoleyl Palmitate). In contrast, when extracted human SSLs film was irradiated, the more marked modifications were observed on SQ. This confirmed the antioxidant role of SQ by scavenging free radicals generated from the oxidation of polyunsaturated fatty acids (PUFA). [ABSTRACT FROM AUTHOR]

Raman and infrared spectroscopy, used as individual and low-level fused datasets, were evaluated to identify and quantify the presence of adulterants (palm oil, PO; ω-3 concentrates in ethyl ester, O3C and fish oil, FO) in krill oil. These datasets were qualitatively analysed with principal component analysis (PCA) and classified as adulterated or unadulterated using support vector machines (SVM). Using partial least squares regression (PLSR), it was possible to identify and quantify the adulterant present in the KO mixture. Raman spectroscopy performed better (r2 = 0.98; RMSEP = 2.3%) than IR spectroscopy (r2 = 0.91; RMSEP = 4.2%) for quantification of O3C in KO. A data fusion approach further improved the analysis with model performance for quantification of PO (r2 = 0.98; RMSEP = 2.7%) and FO (r2 = 0.76; RMSEP = 9.1%). This study demonstrates the potential use of Raman and IR spectroscopy to quantify adulterants present in KO. [ABSTRACT FROM AUTHOR]

To our knowledge, the study interconnection between inherent chemical functional group spectral features and nutrient utilisation is still limited. The objective of this study was to test the adequacy of vibrational Fourier transform infrared attenuated total reflectance (ATR‐FTIR) spectroscopy as a fast tool to assess the interactive relationship between the nutritive value of the Prairie cool‐season oat (Avena sativa L.) varieties in dairy cows and inherent chemical functional group spectral features. The chemical functional group spectral features of the Prairie cool‐season oat varieties in western Canada were determined by Fourier transform infrared attenuated total reflectance spectroscopy. The protein‐related spectral parameters of chemical functional groups included peak height and peak area intensity of Amide I, Amid II, protein structural α‐helix and β‐sheet, and their ratios. The rumen degradation kinetics were determined using in situ techniques with four rumen‐canulated lactating dairy cows. The intestinal digestion was evaluated using a three‐step in vitro technique with 12 h preincubation. The experiment was an randomized complete block design. The data were analysed using the mixed‐model procedure of the Statistical Analysis System. The results showed that the interconnection between rumen degradation kinetics, intestinal digestion and true nutrient supply to dairy cows and protein‐related chemical functional group spectral features could be revealed by ATR‐FTIR with univariate and multi‐variate spectral analyses. These findings indicate that ruminant relevant nutritive value of cool‐season oats could be rapidly evaluated and predicted using oat‐specific functional group spectral characteristics which could be obtained by a non‐distractive bioanalytical tool of ATR‐FTIR spectroscopy. [ABSTRACT FROM AUTHOR]

This work aims at synthesizing by reaction in the solid state orthophosphate type compounds usable in different applications (electrochemical performances, laser materials, magnetic materials, ionic conductors, potential in optics, catalysts, sensors, ceramics, etc.). The optimal operating conditions have been determined. The characterization of the materials obtained was carried out from a structural point of view by X-ray diffraction, Raman, and infrared spectroscopies, and morphologically, by scanning electron microscopy coupled with analysis by energy dispersive X-ray spectroscopy and transmission electron microscopy. The Rietveld procedure was used for the refinement investigation, and the findings reveal that the observed and calculated patterns are in excellent agreement. In the complete composition range (0 ≤ x ≤ 2), the Ba2 − xPbxSr(PO4)2 compounds crystallize in the hexagonal system at space group R 3 ¯ m with multiple units per crystal lattice Z = 3 and produce a solid solution. In solid solutions, the a and c lattice parameters varied, with a reduction in the a and c parameters proportional to the radius of the corresponding replaced ions. The M(1) and M(2) positions in the lacunar anionic orthophosphate structure were shown to be preferentially occupied by Pb2+/Ba2+/Sr2+ ions in solid solutions. The vibrational spectra of this solid solution series of crystalline orthophosphate are assigned by comparison with other orthophosphate materials and interpreted based on factor group analysis in space group R 3 ¯ m (D3d5). Raman and IR spectroscopy studies give results justifying the crystal symmetry already demonstrated by X-ray diffraction. [ABSTRACT FROM AUTHOR]

In the UK alone, the incidence of cervical cancer is increasing, hence an urgent need for early and rapid detection of cancer before it develops. Spectroscopy in conjunction with machine learning offers a disruptive technology that promises to pick up cancer early as compared to the current diagnostic techniques used. This review article explores the different spectroscopy techniques that have been used for the analysis of cervical cancer. Along with the extensive description of spectroscopic techniques, the various machine learning techniques are also described as well as the applications that have been explored in the diagnosis of cervical cancer. This review delimits the literature specifically associated with cervical cancer studies performed solely with the use of a spectroscopy technique, and machine learning. Although there are several methods and techniques to detect cervical cancer, the clinical sector requires to introduce new diagnostic technologies that help improve the quality of life of patients. These innovative technologies involve spectroscopy as a qualitative method and machine learning as a quantitative method. In this article, both the techniques and methodologies that allow and promise to be a new screening tool for the detection of cervical cancer are covered. [ABSTRACT FROM AUTHOR]

Molecular vibrations play a crucial role in physical chemistry and biochemistry, and Raman and infrared spectroscopy are the two most used techniques for vibrational spectroscopy. These techniques provide unique fingerprints of the molecules in a sample, which can be used to identify the chemical bonds, functional groups, and structures of the molecules. In this review article, recent research and development activities for molecular fingerprint detection using Raman and infrared spectroscopy are discussed, with a focus on identifying specific biomolecules and studying the chemical composition of biological samples for cancer diagnosis applications. The working principle and instrumentation of each technique are also discussed for a better understanding of the analytical versatility of vibrational spectroscopy. Raman spectroscopy is an invaluable tool for studying molecules and their interactions, and its use is likely to continue to grow in the future. Research has demonstrated that Raman spectroscopy is capable of accurately diagnosing various types of cancer, making it a valuable alternative to traditional diagnostic methods such as endoscopy. Infrared spectroscopy can provide complementary information to Raman spectroscopy and detect a wide range of biomolecules at low concentrations, even in complex biological samples. The article concludes with a comparison of the techniques and insights into future directions. [ABSTRACT FROM AUTHOR]

A series of zigzag‐edged polycyclic aromatic hydrocarbons (PAHs) (Z1‐Z3) were synthesized from 2,12‐dibromo‐7,14‐diphenyl‐benzo[m]tetraphene (9) as a versatile building block. Their structures were unambiguously confirmed by laser desorption/ionization time‐of‐flight mass spectrometry, 1H NMR, Raman, and Fourier‐transformed infrared (FTIR) spectroscopies as well as scanning tunneling microscopy. The fingerprint vibrational modes were elucidated with theoretical support. The edge‐ and size‐dependent optical properties were characterized by UV‐Vis absorption and fluorescence spectroscopy and DFT calculations. Moreover, ultrafast transient absorption spectroscopy revealed distinct modulation of the photophysical properties upon π‐extension from Z1 to Z2, the latter having a gulf edge. [ABSTRACT FROM AUTHOR]

In recent years, the disease burden of hyperuricemia has been increasing, especially in high-income countries and the economically developing world with a Western lifestyle. Abnormal levels of uric acid and hypoxanthine are associated with many diseases, and therefore, to demonstrate improved methods of uric acid and hypoxanthine detection, three different bodily fluids were analysed using surface-enhanced Raman spectroscopy (SERS) and high-performance liquid chromatography (HPLC). Gold nanostar suspensions were mixed with series dilutions of uric acid and hypoxanthine, 3 kDa centrifugally filtered human blood serum, urine and saliva. The results show that gold nanostars enable the quantitative detection of the concentration of uric acid and hypoxanthine in the range 5–50 μg/mL and 50–250 ng/mL, respectively. The peak areas of HPLC and maximum peak intensity of SERS have strongly correlated, notably with the peaks of uric acid and hypoxanthine at 1000 and 640 cm−1, respectively. The r2 is 0.975 and 0.959 for uric acid and hypoxanthine, respectively. Each of the three body fluids has a number of spectral features in common with uric acid and hypoxanthine. The large overlap of the spectral bands of the SERS of uric acid against three body fluids at spectra peaks were at 442, 712, 802, 1000, 1086, 1206, 1343, 1436 and 1560 cm−1. The features at 560, 640, 803, 1206, 1290 and 1620 cm−1 from hypoxanthine were common to serum, saliva and urine. There is no statistical difference between HPLC and SERS for determination of the concentration of uric acid and hypoxanthine (p > 0.05). For clinical applications, 3 kDa centrifugal filtration followed by SERS can be used for uric acid and hypoxanthine screening is, which can be used to reveal the subtle abnormalities enhancing the great potential of vibrational spectroscopy as an analytical tool. Our work supports the hypnosis that it is possible to obtain the specific concentration of uric acid and hypoxanthine by comparing the SER signals of serum, saliva and urine. In the future, the analysis of other biofluids can be employed to detect biomarkers for the diagnosis of systemic pathologies. [ABSTRACT FROM AUTHOR]

A laser power-dependent Raman spectroscopic study has been done to explore the phonon shift, electron–phonon coupling, phase change, and surface temperature in hydrothermally prepared bulk 2H-MoS2 nanoflakes with two different laser excitation wavelengths, i.e., 532 nm and 488 nm. The phonon softening and asymmetry in the vibrational modes are attributed to the laser-induced heating and Fano resonance, respectively. Fano resonance happens due to electron–phonon coupling and appears as an asymmetry in the Raman line shape. The fundamental vibrational phonon modes which show asymmetry are fitted using the Fano line shape function, and the laser power-dependent electron–phonon coupling changes are systematically studied. The asymmetry factor for E 2 g 1 and A 1 g modes gave negative and positive values, respectively. The laser-induced surface temperature of the material is calculated using Stokes/anti-Stokes method. [ABSTRACT FROM AUTHOR]

In this review, some physical properties of organic-inorganic perovskites, elastomer blends and glass are discussed; the mechanical behavior, optical bandgap, vibrational spectroscopy and nanostructure of these materials are investigated. The study of the mechanical properties of elastomer blends uses the pulse excitation technique as it is non-contact, easy used and not affecting the sample, reliable, low cost, accurate and suiting a wide variety of rubbery materials and elastomers. The internal friction coefficient is obtained by mathematical analysis and shows as the concentration of N774 black increases the internal friction increases until 90 phr, followed by a sharp increase. This may be due to the enhancement of the aggregations formations, less occlude rubber, the active friction forces in the deagglomeration - agglomeration of the filler vanishing and the special characteristic of N774 black (large particle size and low tendency to form aggregations). The study of the optical bandgap of perovskites and glasses by Schuster-Kubelka-Munk (SKM) remission function is achieved. The studied samples of perovskites show a strong absorption at the UV-Vis light region, so this behavior may find attractive applications as visible light photocatalysis. While these study on ZnO doped phosphate glass system show optical energy gap decrease from 3.68 eV to 3.25 eV with the increasing ZnO content. This can be related to the gradual increase in number of non-bridging oxygen (NBO) atoms. Vibrational spectroscopy is an efficient method to assign the IR/Raman peaks to their modes in the molecule or a part of it. The partial symmetry and Omega-table enhance the group theory character table and correct the meaning of complex quantities in it. The study of nanostructure by X-ray diffraction patterns is useful to determine the crystalline size. More deep theoretical approaches refine the obtained size and show the micro-strain inside the nanoparticle. [ABSTRACT FROM AUTHOR]

Raman spectroscopy (RS) has demonstrated its utility in neurooncological diagnostics, spanning from intraoperative tumor detection to the analysis of tissue samples peri- and postoperatively. In this study, we employed Raman spectroscopy (RS) to monitor alterations in the molecular vibrational characteristics of a broad range of formalin-fixed, paraffin-embedded (FFPE) intracranial neoplasms (including primary brain tumors and meningiomas, as well as brain metastases) and considered specific challenges when employing RS on FFPE tissue during the routine neuropathological workflow. We spectroscopically measured 82 intracranial neoplasms on CaF2 slides (in total, 679 individual measurements) and set up a machine learning framework to classify spectral characteristics by splitting our data into training cohorts and external validation cohorts. The effectiveness of our machine learning algorithms was assessed by using common performance metrics such as AUROC and AUPR values. With our trained random forest algorithms, we distinguished among various types of gliomas and identified the primary origin in cases of brain metastases. Moreover, we spectroscopically diagnosed tumor types by using biopsy fragments of pure necrotic tissue, a task unattainable through conventional light microscopy. In order to address misclassifications and enhance the assessment of our models, we sought out significant Raman bands suitable for tumor identification. Through the validation phase, we affirmed a considerable complexity within the spectroscopic data, potentially arising not only from the biological tissue subjected to a rigorous chemical procedure but also from residual components of the fixation and paraffin-embedding process. The present study demonstrates not only the potential applications but also the constraints of RS as a diagnostic tool in neuropathology, considering the challenges associated with conducting vibrational spectroscopic analysis on formalin-fixed, paraffin-embedded (FFPE) tissue.

The endohedral lithium fulleride, Li+@C60•−, is a potential precursor for new families of molecular superconducting and electronic materials beyond those accessible to date from C60 itself. Solid Li@C60 comprises (Li@C60)2 dimers, isostructural and isoelectronic with the (C59N)2 units found in solid azafullerene. Here, we investigate the structural and vibrational properties of Li@C60 samples synthesized by electrolytic reduction routes. The resulting materials are of high quality, with crystallinity far superior to that of their antecedents isolated by chemical reduction. They permit facile, unambiguous identification of both the reduced state of the fulleride units and the interball C-C bonds responsible for dimerization. However, severe orientational disorder conceals any crystal symmetry lowering due to the presence of dimers. Diffraction reveals the adoption of a hexagonal crystal structure (space group P63/mmc) at both low temperatures and high pressures, typically associated with close-packing of spherical monomer units. Such a situation is reminiscent of the structural behavior of the high-pressure Phase I of solid dihydrogen, H2.

Metabolites are the signature of biochemical reactions that occur in living cells and carry the chemical information of the cell. Analysis of metabolites in biofluids not only provides the information about the internal chemistry of the body but also the body’s state. This can be an efficient route for the development of minimal-invasive or non-invasive diagnosis even in an early disease state if a reliable metabolite detection technique is developed. In particular, volatile metabolites-based breath diagnosis is most attractive since exhaled breath samples can be collected in a fully non-invasive way. Infrared spectroscopy provides a non-destructive, label-free, molecular identification technique, which makes it unbeatable over other existing techniques. It is already applied to the diagnosis of different life-threatening diseases like cancer, diabetes, bacterial infection, and many more. Technical detail of the infrared diagnosis of gaseous biofluids will be presented.

Understanding and classifying inherent tumor heterogeneity is a multimodal approach, which can be undertaken at the genetic, biochemical, or morphological level, among others. Optical spectral methods such as Raman spectroscopy aim at rapid and non-destructive tissue analysis, where each spectrum generated reflects the individual molecular composition of an examined spot within a (heterogenous) tissue sample. Using a combination of supervised and unsupervised machine learning methods as well as a solid database of Raman spectra of native glioblastoma samples, we succeed not only in distinguishing explicit tumor areas—vital tumor tissue and necrotic tumor tissue can correctly be predicted with an accuracy of 76%—but also in determining and classifying different spectral entities within the histomorphologically distinct class of vital tumor tissue. Measurements of non-pathological, autoptic brain tissue hereby serve as a healthy control since their respective spectroscopic properties form an individual and reproducible cluster within the spectral heterogeneity of a vital tumor sample. The demonstrated decipherment of a spectral glioblastoma heterogeneity will be valuable, especially in the field of spectroscopically guided surgery to delineate tumor margins and to assist resection control.

This paper presents far-ultraviolet through mid-infrared (0.12–20 μ m) reflectance spectra of 27 fine-particulate (

Infrared (IR) spectra of vapor-deposited amorphous water at low temperatures show two weak peaks at around 3720 and 3696 cm ^−1 assigned to free-OH stretching modes of two- and three-coordinated water molecules (so-called “dangling” OH bonds), respectively, on the ice surface. A recent JWST observation first succeeded in detection of a potential dangling OH feature at 3664 cm ^−1 for ices in molecular clouds, highlighting the importance of dangling OH bonds in interstellar ice chemistry. A lack of band strengths of these features at low temperatures restricts the quantification of dangling OH bonds from IR spectra, hindering development of a molecular-level understanding of the surface structure and chemistry of ice. Using IR multiple-angle incidence resolution spectrometry, we quantified the band strengths of two- and three-coordinated dangling OH features in amorphous water at 20 K as being 4.6 ± 1.6 × 10 ^−18 and 9.1 ± 1.0 × 10 ^−18 cm molecule ^−1 , respectively. These values are more than an order of magnitude lower than band strengths of bulk-water molecules in ice and liquid water and are similar to those of H _2 O monomers confined in solid matrices. Adsorption of carbon monoxide with dangling OH bonds results in the appearance of a new broad dangling OH feature at 3680–3620 cm ^−1 , with a band strength of 1.8 ± 0.1 × 10 ^−17 cm molecule ^−1 . The band strengths of dangling OH features determined in this study advance our understanding of the surface structure of interstellar ice analogs and recent IR observations of the JWST.

Two fundamental halocarbon ions, CH2Cl+ and CH3ClH+, were studied in the gas phase using the FELion 22-pole ion trap apparatus and the Free Electron Laser for Infrared eXperiments (FELIX) at Radboud University, Nijmegen (the Netherlands). The vibrational bands of a total of four isotopologs, CH235,37Cl+ and CH335,37ClH+, were observed in selected wavenumber regions between 500 and 2900 cm−1 and then spectroscopically assigned based on the results of anharmonic force field calculations performed at the CCSD(T) level of theory. As the infrared photodissociation spectroscopy scheme employed probes singly Ne-tagged weakly bound complexes, complementary quantum-chemical calculations of selected species were also performed. The impact of tagging on the vibrational spectra of CH2Cl+ and CH3ClH+ is found to be virtually negligible for most bands; for CH3ClH+–Ne, the observations suggest a proton-bound structural arrangement. The experimental band positions as well as the best estimate rotational molecular parameters given in this work provide a solid basis for future spectroscopic studies at high spectral resolutions.

The hydration condition of an anion exchange membrane (AEM) in an operating fuel cell significantly affects its performance as well as its lifespan. In this paper, an in-house build coherent anti-Stokes Raman scattering (CARS) vibrational spectroscopy is used to establish the hydration of an AEM in an anion exchange membrane fuel cell (AEMFC) while it generates power. During steady-state operation, water on the anode side increased with current density. On the cathode side and at the center of the membrane, water initially decreased with current density and then started increasing at a slower pace than on the anode side. A deconvolution of the OH peak in the recorded CARS spectra into nine species revealed that only the H-bonded water species underwent variation. The rest of the species experienced a negligible change. A transient study revealed that maximum disturbance to the water distribution was achieved after 5 s of applying a current jump. The distribution of water became stable within 20 s after applying the current jump. The response to the current jump on the anode side was opposite to that on the cathode. These results open the way for a widespread dynamic study of water distribution in different AEMFCs. The technique could also be directly used to evaluate the dynamic degradation of AEMs.

Water is a ubiquitous and vital component of living systems. Hydration, which is the interaction between water and intracellular biomolecules, plays an important role in cellular processes. However, it is technically challenging to study water structure within cells directly. Here, we demonstrate the utility and power of the water bend-libration combination band as a unique Raman spectral imaging probe of cellular hydration. Hydration maps reveal distinct water environments within subcellular compartments (e.g., nucleolus and lipid droplet) due to the spectral sensitivity of this coupled vibrational band. Spectroscopic studies using the water bend-libration are broadly applicable, offering the potential to capture the chemical complexity of hydration in numerous systems. [ABSTRACT FROM AUTHOR]

The reaction of the pyridine adduct of SO3 and tetra‐n‐butyl‐ammonium cyanide, [N(nBu)4][CN] at room temperature leads to the unprecedented cyanido‐sulfate anion [SO3CN]− stabilized in the salt [N(nBu)4][SO3CN]. The anion is a pseudo‐halogen congener of the well‐known fluoro‐ and chloro‐sulfates. The new anion has been studied by vibrational spectroscopy and theoretical calculations. [ABSTRACT FROM AUTHOR]

The reaction of the pyridine adduct of SO3 and tetra‐n‐butyl‐ammonium cyanide, [N(nBu)4][CN] at room temperature leads to the unprecedented cyanido‐sulfate anion [SO3CN]− stabilized in the salt [N(nBu)4][SO3CN]. The anion is a pseudo‐halogen congener of the well‐known fluoro‐ and chloro‐sulfates. The new anion has been studied by vibrational spectroscopy and theoretical calculations. [ABSTRACT FROM AUTHOR]

Ultraviolet resonance Raman (UVRR) spectroscopy is a vibrational technique that reveals structures and dynamics of biological macromolecules without the use of extrinsic labels. By tuning the Raman excitation wavelength to the deep UV region (e.g., 228 nm), Raman signal from tryptophan and tyrosine residues are selectively enhanced, allowing for the study of these functionally relevant amino acids in lipid and aqueous environments. In this chapter, we present methods on the UVRR data acquisition and analysis of the tryptophan vibrational modes of a model β-barrel membrane protein, OmpA, in folded and unfolded conformations.

Abstract Background The allocation of non-structural carbohydrates (NSCs) plays a critical role in the physiology and metabolism of tree growth and survival defense. However, little is known about the allocation of NSC after continuous mechanical wounding of pine by resin tapping during tree growth. Results Here, we examine the NSC allocation in plant tissues after 3 year lasting resin tapping, and also investigate the use of near-infrared reflectance (NIR) spectroscopy to quantify the NSC, starch and free sugar (e.g., sucrose, glucose, and fructose) concentrations in different plant tissues of slash pine. Spectral measurements on pine needle, branch, trunk phloem, and root were obtained before starch and free sugar concentrations were measured in the laboratory. The variation of NSC, starch and free sugars in different plant tissues after resin tapping was analyzed. Partial least squares regression was applied to calibrate prediction models, models were simulated 100 times for model performance and error estimation. More NSC, starch and free sugars were stored in winter than summer both in tapped and control trees. The position of resin tapping significantly influenced the NSCs allocation in plant tissues: more NSCs were transformed into free sugars for defensive resin synthesis close to the tapping wound rather than induced distal systemic responses. Models for predicting NSC and free sugars of plant tissues showed promising results for the whole tree for fructose (R2 CV = 0.72), glucose (R2 CV = 0.67), NSCs (R2 CV = 0.66) and starch (R2 CV = 0.58) estimates based on NIR models. Models for individual plant tissues also showed reasonable predictive ability: the best model for NSCs and starch prediction was found in root. The significance multivariate correlation algorithm for variable selection significantly reduced the number of variables. Important variables were identified, including features at 1021–1290 nm, 1480, 1748, 1941, 2020, 2123 and 2355 nm, which are highly related to NSC, starch, fructose, glucose and sucrose. Conclusions NIR spectroscopy provided a rapid and cost-effective method to monitor NSC, starch and free sugar concentrations after continuous resin tapping. It can be used for studying the trade-off between growth and production of defensive metabolites.

The molecular structure and spectroscopic analysis of the Temozolomide molecule have been performed using the density functional theory in neutral and anion states as well as with the addition of DMSO solvent. The 6-311G(d) basis set was employed to optimize the molecular structure of the TMZ molecule using the DFT/B3LYP method. The HOMO-LUMO energies and MEP map were computed to determine the energy gap and probable sites of electrophilic and nucleophilic reactivity in the 6-311G+(d) basis set. The vibrational frequencies were calculated using a computational method and the major fundamental modes of vibration were assigned to their respective frequencies. The potential of the computational method to explain the vibrational modes was determined by comparing simulated spectra with experimental spectra. On isotope labeling of carbon, the frequency was shifted significantly.

The HBP radical was generated via the reaction of laser ablated boron atom with PH3 in a solid neon matrix, which is identified via IR spectroscopy with isotopic substitutions and quantum chemical calculations. The results show that HBP has a 2Π electronic ground state with a short B−P bond. Bonding analysis indicates that besides an electron‐sharing σ bond, there are two degenerate π bonding orbitals that are occupied by three electrons, resulting in a bond order of two and half between P and B. This is in sharp contrast to the bonding properties of the isovalent HNB, which was characterized to be a N≡B triply bonded σ radical with the unpaired electron locating on the B atom. [ABSTRACT FROM AUTHOR]

Oral malignant and potentially malignant conditions affect several people worldwide each year. The early diagnoses of these conditions play an important role in prevention and recovery. Vibrational spectroscopy techniques such as Raman spectroscopy (RS) and Fourier‑transform infrared (FTIR) spectroscopy are used in the early, non‑invasive, label‑free diagnosis of malignant and pre‑malignant conditions, and are areas of active research. However, there is no conclusive evidence suggesting the translatability of these methods into clinical practice. This systematic review and meta‑analysis presents pooled evidence for RS and FTIR methods in the detection of malignant and potentially malignant conditions of the oral cavity. Electronic databases were searched for published literature on RS and FTIR in the diagnosis of oral malignant and potentially malignant conditions. The pooled sensitivity, specificity, diagnostic accuracy, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), pre‑test, and post‑test probability were then calculated using the random‑effects model. A subgroup analysis was conducted separately for RS and FTIR methods. A total of 12 studies were included (8 of RS; 4 of FTIR) as per the eligibility criteria. The pooled sensitivity and specificity of the vibrational spectroscopy methods were calculated to be 0.99 (95% confidence interval [CI]: 0.90, 1.00) and 0.94 (95% CI: 0.85, 0.98), respectively. The area under the curve (AUC) for the summary receiving operator characteristic curve was found to be 0.99 (0.98–1.00). Therefore, the results obtained in this study suggest that the RS and FTIR methods offer great potential to be used in the early diagnosis of oral malignant and pre‑malignant conditions. [ABSTRACT FROM AUTHOR]

This review focuses on recent advances and future perspectives in the use of Raman spectroscopy for cervical cancer, a global women's health issue. Cervical cancer is the fourth most common women's cancer in the world, and unfortunately mainly affects younger women. However, when detected at the early precancer stage, it is highly treatable. High-quality cervical screening programmes and the introduction of the human papillomavirus (HPV) vaccine are reducing the incidence of cervical cancer in many countries, but screening is still essential for all women. Current gold standard methods include HPV testing and cytology for screening, followed by colposcopy and histopathology for diagnosis. However, these methods are limited in terms of sensitivity/specificity, cost, and time. New methods are required to aid clinicians in the early detection of cervical precancer. Over the past 20 years, the potential of Raman spectroscopy together with multivariate statistical analysis has been shown for the detection of cervical cancer. This review discusses the research to date on Raman spectroscopic approaches for cervical cancer using exfoliated cells, biofluid samples, and tissue ex vivo and in vivo. [ABSTRACT FROM AUTHOR]