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Fingernails can act as important forensic evidence as they can be a source of DNA that may link the victim or accused to the crime scene and may also contain traces of drugs such as cocaine and heroin, in regular users. Moreover, previous studies have shown that analyzing fingernails with various techniques can reveal important information, such as age and sex. In this work, ATR-FTIR spectroscopy with chemometric tools has been used to estimate the age and sex from fingernails by analyzing 140 fingernail samples (70 males, and 70 females) collected from volunteers aged between 10 and 70 years old. The amide bands obtained from spectra confirmed the presence of keratin proteins in the samples. PCA and PLS-R were used for the classification of samples. For sex estimation, samples were divided into four categories based on age groups, followed by the differentiation of sex in each group. Similarly, for age estimation, all samples were divided into two sets based on male and female followed by differentiation of age groups in each set. The result showed that PLS-R was able to differentiate fingernail samples based on sex in groups G1, G2, G3, and G4 with R-square values of 0.972, 0.993, 0.991, and 0.996, respectively, and based on age in females, and males with R-square values of 0.93 and 0.97, respectively. External validation and blind tests were also performed which showed results with 100% accuracy. This approach has proved to be effective for the estimation of sex and age from fingernail samples. Highlights: • Estimation of age and sex using fingernails via ATR-FTIR and chemometrics. • PLS-R successfully estimated age and sex using fingernails with high R-square values. • Blind and external validation tests illustrated 100% accuracy. • The present approach is quick, and non-destructive with minimal or no sample preparation. [ABSTRACT FROM AUTHOR]

During the past few decades, Raman spectroscopy has progressed and captivated added attention in the field of science. However, the application of Raman spectroscopy is not limited to the field of forensic science and analytical chemistry; it is one of the emerging spectroscopic techniques, utilized in the field of forensic science which in turn could be a supporting tool in the law and justice system. The advantage of Raman spectroscopy over the other conventional techniques is that it is rapid, reliable, and non-destructive in nature with minimal or no sample preparation. The quantitative and qualitative analysis of evidence from biological and non-biological origins could easily be performed by using Raman spectroscopy. The forensic domain is highly complex with multidisciplinary branches, and therefore a plethora of techniques are utilized for the detection, identification, and differentiation of innumerable pieces of evidence for the purpose of law and justice. Herein, a systematic review is carried out on the application of Raman spectroscopy in the realm of forensic biology and serology considering its usefulness in practical perspectives. This review paper highlights the significance of modern techniques, including micro-Raman spectroscopy, confocal Raman spectroscopy, surface-enhanced Raman spectroscopy, and paper-based surface-enhanced Raman spectroscopy, in the field of Raman spectroscopy. These techniques have demonstrated notable advancements in terms of their applications and capabilities. Furthermore, to comprehensively capture the progress in the development of Raman spectroscopy, all the published papers which could be retrieved from the available databases from the year 2007 to 2022 were incorporated. [ABSTRACT FROM AUTHOR]

We have approached the construction of an artificial enzyme by employing a robust protein scaffold, lactococcal multidrug resistance regulator, LmrR, providing a structured secondary and outer coordination spheres around a molecular rhodium complex, [RhI(PEt2NglyPEt2)2]−. Previously, we demonstrated a 2–3 fold increase in activity for one Rh-LmrR construct by introducing positive charge in the secondary coordination sphere. In this study, a series of variants was made through site-directed mutagenesis where the negative charge is located in the secondary sphere or outer coordination sphere, with additional variants made with increasingly negative charge in the outer coordination sphere while keeping a positive charge in the secondary sphere. Placing a negative charge in the secondary or outer coordination sphere demonstrates decreased activity by a factor of two compared to the wild-type Rh-LmrR. Interestingly, addition of positive charge in the secondary sphere, with the negatively charged outer coordination sphere restores activity. Vibrational and NMR spectroscopy suggest minimal changes to the electronic density at the rhodium center, regardless of inclusion of a negative or positive charge in the secondary sphere, suggesting another mechanism is impacting catalytic activity, explored in the discussion. [ABSTRACT FROM AUTHOR]

The single crystals of the title compound (1) were grown from a water solution. The compound crystallizes in the centrosymmetric space group P21/c of the monoclinic system with eight molecules per unit cell. Multiple recrystallizations of the crystals from heavy water gives deuterated analogue 1d. The asymmetric unit of 1 contains two salt molecules. Both independent cations interact with anions via N−H...O hydrogen bonds with R22(8) and R21(6) graphs forming 1:1 salt molecules. Both salt molecules are linked by additional N−H...O and O−H...O hydrogen bonds with a graph R22(9). The oppositely charged components of the crystals, i.e., 1-(diaminomethylene)thiouron-1-ium cations and 2,3-pyridine-dicarboxylate anions, interact each other forming three-dimensional supramolecular hydrogen bonded network. The interactions between the components as well as between the 1:1 salt molecules were analysed using the Hirshfeld surface. The compound was also characterized by vibrational spectroscopy. The vibrational bands were interpreted based on the optimized structure and force field calculations of normal coordinates based on the density functional theory (DFT) with the base set 6-31G(d,p). Isotopic frequency shift and potential energy distribution (PED) were used to assign the bands. The electronic absorption spectra of 1 in the gas phase, as well as in polar and non-polar solvents, were calculated. [ABSTRACT FROM AUTHOR]

Bulk composition of kidney stones, often analyzed with infrared spectroscopy, plays an essential role in determining the course of treatment for kidney stone disease. Though bulk analysis of kidney stones can hint at the general causes of stone formation, it is necessary to understand kidney stone microstructure to further advance potential treatments that rely on in vivo dissolution of stones rather than surgery. The utility of Raman microscopy is demonstrated for the purpose of studying kidney stone microstructure with chemical maps at ≤ 1 µm scales collected for calcium oxalate, calcium phosphate, uric acid, and struvite stones. Observed microstructures are discussed with respect to kidney stone growth and dissolution with emphasis placed on < 5 µm features that would be difficult to identify using alternative techniques including micro computed tomography. These features include thin concentric rings of calcium oxalate monohydrate within uric acid stones and increased frequency of calcium oxalate crystals within regions of elongated crystal growth in a brushite stone. We relate these observations to potential concerns of clinical significance including dissolution of uric acid by raising urine pH and the higher rates of brushite stone recurrence compared to other non-infectious kidney stones. [ABSTRACT FROM AUTHOR]

Synthesis and study of the structure and various properties of Na–Cs and Na–Rb aluminoborosilicate model glasses with addition of the alkaline-earth cations have been carried out. Vibrational spectroscopy techniques have been used to establish the high degree of polymerization and noticeable structural similarity of all synthesized glasses at fixed ratio of modifying and network-forming cations. It has been shown that increasing fraction of large cations in the total content of modifying cations leads to changes in distribution of modifying cations between the silicate and borate structural units. The observed homogeneity with the similarity of anionic structure, at different content and various combinations of alkali and alkaline-earth cations, points at promising application of these glasses as a basis for synthesis of matrix materials for high-level radioactive waste disposal. [ABSTRACT FROM AUTHOR]

The characterization of normal mode (CNM) procedure coupled with an adiabatic connection scheme (ACS) between local and normal vibrational modes, both being a part of the Local Vibrational Mode theory developed in our group, can identify spectral changes as structural fingerprints that monitor symmetry alterations, such as those caused by Jahn-Teller (JT) distortions. Employing the PBE0/Def2-TZVP level of theory, we investigated in this proof-of-concept study the hexaaquachromium cation case, [Cr(OH2)6] 3+/[Cr(OH2)6] 2+, as a commonly known example for a JT distortion, followed by the more difficult ferrous and ferric hexacyanide anion case, [Fe(CN)6] 4−/[Fe(CN)6] 3−. We found that in both cases CNM of the characteristic normal vibrational modes reflects delocalization consistent with high symmetry and ACS confirms symmetry breaking, as evidenced by the separation of axial and equatorial group frequencies. As underlined by the Cremer-Kraka criterion for covalent bonding, from [Cr(OH2)6]3+ to [Cr(OH2)6]2+ there is an increase in axial covalency whereas the equatorial bonds shift toward electrostatic character. From [Fe(CN)6]4− to [Fe(CN)6]3− we observed an increase in covalency without altering the bond nature. Distinct π back-donation disparity could be confirmed by comparison with the isolated CN− system. In summary, our study positions the CNM/ACS protocol as a robust tool for investigating less-explored JT distortions, paving the way for future applications. [ABSTRACT FROM AUTHOR]

The degree of DNA compaction in various regions of the cell nucleus determines whether the corresponding genes should be expressed and other crucial cellular processes, such as DNA replication and repair, should occur. Therefore, the development of approaches to the experimental assessment of DNA compactness in cell nuclei, as well as its indicator, dynamic disorder which determines the degree of thermal fluctuation in the position and mutual orientation of molecular fragments, is highly relevant. In this paper, using single-stranded guanine and cytosine oligonucleotides, as well as their double-stranded combination as an example, it is shown that dynamic disorder in DNA can be assessed based on low-frequency Raman scattering (RS) spectroscopy data. For the first time, Raman spectra of oligonucleotides have been measured over a wide frequency range, including the low-frequency (10–200 cm ) and high-frequency (200–2000 cm ) regions. It was found that the low-frequency Raman intensity is maximal in single-stranded oligocytosine and minimal in the double-stranded oligonucleotide, which is in full agreement with the magnitude of dynamic disorder estimated from molecular dynamics simulations. The obtained results indicate the promising application of low-frequency Raman spectroscopy for assessing dynamic disorder and DNA compactness. The use of such a technique is expected to contribute to the understanding of key cellular processes and the physical mechanisms that underlie them, which is necessary for the development of advanced methods in molecular biophysics and cell biology. [ABSTRACT FROM AUTHOR]

We performed 1H and 29Si NMR and infrared measurements, and first-principles calculations to clarify the nature of OH defects in MgSiO3 orthoenstatite. An orthoenstatite sample synthesized at 7 GPa and 1200 °C from a composition of MgSiO3 + 0.1 wt% H2O yielded two 1H MAS NMR peaks near 5.9 and 7.6 ppm that are correlated in 2D NMR spectra, and two infrared bands near 3361 and 3066 cm− 1 that correspond to the previously reported A3 and A4 bands. The first-principles calculations confirmed that they are due to a pair of protons in a Mg (M2) vacancy. The previously reported A1 and A2 infrared bands near 3687 and 3592 cm− 1 for orthoenstatite synthesized at low silica activities were confirmed to arise from four protons in a SiB vacancy. The latter is predicted to give two additional OH stretching bands associated with two strongly hydrogen-bonded O3b-H bonds with frequencies below the spectral range reported thus far. The previously reported infrared absorption coefficients were thus revised to account for the undetected bands. 1H NMR may be used to quantitatively detect all four protons (expected at 1–12 ppm). Other mantle minerals should also be examined for potentially overlooked OH defects with strong hydrogen bonding. [ABSTRACT FROM AUTHOR]

Electrochemical Raman spectroscopy can provide valuable insights into electrochemical reaction mechanisms. However, it also shows various pitfalls and challenges. This paper gives an overview of the necessary theoretical background, crucial practical considerations for successful measurement, and guidance for in situ/in operando electrochemical Raman spectroscopy. Several parameters must be optimized for suitable reaction and measurement conditions. From the experimental side, considerations for the setup, suitable signal enhancement methods, choice of material, laser, and objective lens are discussed. Different interface phenomena are reviewed in the context of data interpretation and evaluation. [ABSTRACT FROM AUTHOR]

The coordination and extraction properties of two related tripodal ligands differed by types of addition of the triazole fragment and linker length in the {2-[(4-Ph-1,2,3-triazol-1-yl)CH2CH2O]C6H4}3P(O) (L1) and {2-[(1-Ph-1,2,3-triazol-4-yl)CH2O]C6H4}3P(O) (L2) are compared. The structures of the complexes [Lа(NO3)3L1] (I) and [Lu(NO3)3L1] (II) are studied in the solid phase (elemental analysis, IR and Raman spectroscopy) and in solutions (IR and multinuclear 1H, 13C, and 31P NMR spectroscopy). A normal coordinate analysis at the TPSS-D4/Def2-SVP level is performed for an isolated molecule of the model complex [La{P(O),N3,N2-L3}(O,O-NO3)3] (L3 = {2-[(4-Me-1,2,3-triazol-1-yl)CH2CH2O]C6H4}3-P(O)). According to the set of spectral and quantum chemical data, ligand L1 exhibits the tridentate P(O),N2,N2 coordination in lanthanide complexes I and II. These are neutral complexes in the solid state and in CD3CN solutions, and the dynamic equilibrium of the neutral and ionic complexes is observed in CDCl3. Unlike ligand L1, ligand L2 exhibits the tetradentate P(O),N3,N3,N3 coordination in the [Ln(NO3)3L2] complexes with the same metals (Ln = La3+, Lu3+) in solutions. The efficiency of extraction of microquantities of f elements from the aqueous phase to 1,2-dichloroethane by compounds L1 and L2 is discussed in comparison with the structures of the complexes of both ligands in solutions. [ABSTRACT FROM AUTHOR]

Food safety and food security are two of the main concerns for the modern food manufacturing industry. Disruptions in the food supply and value chains have created the need to develop agile screening tools that will allow the detection of food pathogens, spoilage microorganisms, microbial contaminants, toxins, herbicides, and pesticides in agricultural commodities, natural products, and food ingredients. Most of the current routine analytical methods used to detect and identify microorganisms, herbicides, and pesticides in food ingredients and products are based on the use of reliable and robust immunological, microbiological, and biochemical techniques (e.g. antigen–antibody interactions, extraction and analysis of DNA) and chemical methods (e.g. chromatography). However, the food manufacturing industries are demanding agile and affordable analytical methods. The objective of this review is to highlight the advantages and limitations of the use of vibrational spectroscopy combined with chemometrics as proxy to evaluate and quantify herbicides, pesticides, and toxins in foods. [ABSTRACT FROM AUTHOR]

The coordination properties of the scorpionate ligand 2-PyCH[P(O)Ph2]2 were studied using complexation with neodymium nitrate as an example. The molecular structure of the [Nd{(2-PyCH[P(O)Ph2]2}(NO3)3(H2O)] complex was determined by X-ray diffraction analysis. The structures of the ligand and the complex were studied in the solid state and in solutions by vibrational and multinuclear (1H, 13C, 31P) NMR spectroscopy. The tridentate O,O,N-coordination of the ligand found in the crystal is retained in solution. [ABSTRACT FROM AUTHOR]

To demonstrate that point-of-care multimodal spectroscopy using Near-Infrared (NIR) and Raman Spectroscopy (RS) can be used to diagnose human heart tissue. We generated 105 spectroscopic scans, which comprised 4 NIR and 3 RS scans per sample to generate a "multimodal spectroscopic scan" (MSS) for each heart, done across 15 patients, 5 each from the dilated cardiomyopathy (DCM), Ischaemic Heart Disease (IHD) and Normal pathologies. Each of the MSS scans was undertaken in 3 s. Data were entered into machine learning (ML) algorithms to assess accuracy of MSS in diagnosing tissue type. The median age was 50 years (IQR 49–52) for IHD, 47 (IQR 45–50) for DCM and 36 (IQR 33–52) for healthy patients (p = 0.35), 60% of which were male. MSS identified key differences in IHD, DCM and normal heart samples in regions typically associated with fibrosis and collagen (NIR wavenumbers: 1433, 1509, 1581, 1689 and 1725 nm; RS wavelengths: 1658, 1450 and 1330 cm−1). In principal component (PC) analyses, these differences explained 99.2% of the variation in 4 PCs for NIR, 81.6% in 10 PCs for Raman, and 99.0% in 26 PCs for multimodal spectroscopic signatures. Using a stack machine learning algorithm with combined NIR and Raman data, our model had a precision of 96.9%, recall of 96.6%, specificity of 98.2% and Area Under Curve (AUC) of 0.989 (Table 1). NIR and Raman modalities alone had similar levels of precision at 94.4% and 89.8% respectively (Table 1). MSS combined with ML showed accuracy of 90% for detecting dilated cardiomyopathy, 100% for ischaemic heart disease and 100% for diagnosing healthy tissue. Multimodal spectroscopic signatures, based on NIR and Raman spectroscopy, could provide cardiac tissue scans in 3-s to aid accurate diagnoses of fibrosis in IHD, DCM and normal hearts. Table 1 Machine learning performance metrics for validation data sets of (a) Near-Infrared (NIR), (b) Raman and (c and d) multimodal data using logistic regression (LR), stochastic gradient descent (SGD) and support vector machines (SVM), with combined "stack" (LR + SGD + SVM) AUC Precision Recall Specificity (a) NIR model Logistic regression 0.980 0.944 0.933 0.967 SGD 0.550 0.281 0.400 0.700 SVM 0.840 0.806 0.800 0.900 Stack 0.933 0.794 0.800 0.900 (b) Raman model Logistic regression 0.985 0.940 0.929 0.960 SGD 0.892 0.869 0.857 0.932 SVM 0.992 0.940 0.929 0.960 Stack 0.954 0.869 0.857 0.932 (c) MSS: multimodal (NIR + Raman) to detect DCM vs. IHD vs. normal patients Logistic regression 0.975 0.841 0.828 0.917 SGD 0.847 0.803 0.793 0.899 SVM 0.971 0.853 0.828 0.917 Stack 0.961 0.853 0.828 0.917 (d) MSS: multimodal (NIR + Raman) to detect pathological vs. normal patients Logistic regression 0.961 0.969 0.966 0.984 SGD 0.944 0.967 0.966 0.923 SVM 1.000 1.000 1.000 1.000 Stack 1.000 0.944 0.931 0.969 Bold values indicate values obtained from the stack algorithm and used for analyses [ABSTRACT FROM AUTHOR]

Quantification and characterization of microplastics, synthetic polymers less than 5 mm in diameter, requires extraction methods that can reduce non-plastic debris without loss or alteration of the polymers. Nitric acid has been used to extract plastic particles from zooplankton and other biota because it completely digests tissue and exoskeletons, thus reducing interferences. While the impact of acid digestion protocols on several polymers has been demonstrated, advice for quantifying microplastic and interpreting their spectra following nitric acid digestion is lacking. Fourier transform infrared (FTIR) and/or Raman spectroscopy was performed on plastics from > 50 common consumer products (including a variety of textiles) pre- and post-nitric acid treatment. The percent match and assigned polymer were tabulated to compare the accuracy of spectral identification before and after nitric acid digestion via two open spectral analysis software. Nylon-66, polyoxymethylene, polyurethane, polyisoprene, nitrile rubber, and polymethyl methacrylate had ≥ 90% mass loss in nitric acid. Other less-impacted polymers changed color, morphology, and/or size following digestion. Thus, using nitric acid digestion for microplastic extraction can impact our understanding of the particle sizes and morphologies ingested in situ. Spectral analysis results were compiled to understand how often (1) the best-hit matches were correct (30–60% of spectra), (2) the best-hit matches exceeding the (arbitrary) threshold of 65% match were correct (53–78% of spectra), and (3) the best-hit matches for anthropogenic polymers were incorrectly identified as natural polymers (12–15% of spectra). Based on these results, advice is provided on how nitric acid digestion can impact microplastics as well as spectral interpretation. [ABSTRACT FROM AUTHOR]

A ternary molybdate with the composition KBаLu(MoO4)3 and a monoclinic scheelite-like structure has been synthesized. Codoping KBаLu(MoO4)3 with Er3+/Yb3+ ions, we have obtained an upconversion phosphor exhibiting anti-Stokes luminescence in the range 400–700 nm under IR excitation. The synthesized phosphor has been characterized by X-ray diffraction, differential thermal analysis, and vibrational spectroscopy, and its IR, Raman, and luminescence spectra have been measured. [ABSTRACT FROM AUTHOR]

Background: Analysis of the glutamine metabolic pathway has taken a special place in metabolomics research in recent years, given its important role in cell biosynthesis and bioenergetics across several disorders, especially in cancer cell survival. The science of metabolomics addresses the intricate intracellular metabolic network by exploring and understanding how cells function and respond to external or internal perturbations to identify potential therapeutic targets. However, despite recent advances in metabolomics, monitoring the kinetics of a metabolic pathway in a living cell in situ, real-time and holistically remains a significant challenge. Aim: This review paper explores the range of analytical approaches for monitoring metabolic pathways, as well as physicochemical modeling techniques, with a focus on glutamine metabolism. We discuss the advantages and disadvantages of each method and explore the potential of label-free Raman microspectroscopy, in conjunction with kinetic modeling, to enable real-time and in situ monitoring of the cellular kinetics of the glutamine metabolic pathway. Key scientific concepts: Given its important role in cell metabolism, the ability to monitor and model the glutamine metabolic pathways are highlighted. Novel, label free approaches have the potential to revolutionise metabolic biosensing, laying the foundation for a new paradigm in metabolomics research and addressing the challenges in monitoring metabolic pathways in living cells. [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]

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]

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]

Fourier transform infrared (FTIR) spectroscopy was used to determine the biochemical changes in date palm leaves which induced different NaCl concentrations (2.5 (control), 5, 10 and 20 dS m−1). It was also used to determine the potential role of selenium nanoparticles (Se NPs) at concentrations of 80 and 160 ppm in alleviating salinity stress of date palm (Phoenix dactylifera L.) trees. Results showed the appearance of a new peak at 2850 cm−1 in the lipid region (2800–3000 cm−1) when date palm trees were exposed to salinity stress. This peak was not observed in the control treatment or when salinity was combined with foliar spraying of Se NPs. Furthermore, a clear and distinct peak at 1735 cm−1 was only seen in plants exposed at 10 or 20 dS m−1 salinity. This peak was attributed to membrane lipid compounds that contain carbonyl ester groups. In addition, the findings demonstrated that the treatments affected the secondary structure of proteins (1500–1800 cm−1) and carbohydrates (1200–1500 cm−1). This was evident by the appearance and disappearance of some characteristic peaks in these regions. [ABSTRACT FROM AUTHOR]

This study aimed to monitor nutritional and chemical changes of oats grain by wet chemistry and Fourier transformed infrared spectroscopy (FTIR). Oats grain fermented with or without inoculants of Aspergillus oryzae (AO), AO + Bacillus subtilis (C + D), Saccharomyces cerevisiae (SC), and Lactobacillus salivarius (LBS) was first analysed by wet chemistry for chemical and nutritional compositions. Then, analysed values were predicted by FTIR spectroscopy based on partial least square regression (PLSR). Crude protein increased with LBS and AO fermentations. AO and SC fermentation reduced dietary fibre, tannin and phytic acid contents. Highest fibre degradation was obtained from LBS fermentation, and highest organic acid production from AO and C + D fermentations. In the determination of chemical and nutrient contents, the method performance characteristics of FTIR-PLSR was better than that of wet chemistry methods, with precision values of 0.15–9.5% and accuracy values of around 100% (R2 of 0.954–0.998 and standard error of prediction of 0.024–0.001). Furthermore, FTIR spectra deconvolution showed that oats starch had an overall 5–13% increased amorphous structure and 6–17% reduced proportion of crystalline structure due to the effect of fermentations. Fermentation lead to increased α-helix and side chain of peptides + amino acids, but decreased β-sheet and β-turn. Fermentation caused nutritionally and chemically valuable oats grain and FTIR-PLSR method produced a fast, non-destructive and robust determination. [ABSTRACT FROM AUTHOR]

Coconut (CO) and virgin coconut oil (VCO) are popular functional oils owing to their health benefits. The fraudsters intentionally blend cheap and poor-quality vegetable oils with CO and VCO for economic benefits. Adulteration causes safety and health issues for consumers. In this context, there is a need for rapid, accurate, and precise analytical techniques to detect adulteration in CO and VCO. Conventional analytical methods are arduous and lengthy processes using toxic chemicals and involve tedious sample preparation. Thus, food researchers are in search of precise, rapid, and green analytical techniques to detect and quantify the adulteration of CO and VCO. The present review focuses on summarizing all the analytical techniques along with chemometric tools developed in recent times. Various techniques, such as chromatographic, spectroscopic, and thermal techniques coupled with chemometrics, have been successfully applied in this field. The NIR-based spectroscopic technique is a very optimisable and practical method for adulteration detection in CO and VCO. The official methods currently used must be upgraded as they are comparatively less sensitive than the latest methods. [ABSTRACT FROM AUTHOR]

Pentafluoridozirconic acid crystallohydrates HZrF5·3H2O and HZrF5·2H2O, as well as the intermediate product of their thermal decomposition ZrF4·H2O, are studied by vibrational spectroscopy and thermogravimetry. It is shown that HZrF5·nH2O (n = 2, 3) crystallohydrates are salts with complex cations H5O and H7O . The bands in the IR and Raman spectra are assigned based on the results of quantum-chemical calculations. [ABSTRACT FROM AUTHOR]

In this work, pure and supersalt-doped graphene is evaluated by the density functional theory (DFT) to explore its optical and electronic properties. The doping of supersalt Al(BH4)3 on graphene reduces the highest occupied molecular orbital and lower unoccupied molecular orbital (HOMO–LUMO) bandgap of graphene@Al(BH4)3 and graphene@2Al(BH4)3 to 3.57 and 3.55 eV from 3.61 eV. The improvement in the optoelectronic properties of the supersalt Al(BH4)3-doped graphene is determined by the upshift of UV absorption peak and dipole moment. Polarizability (α) values of graphene@Al(BH4)3, and graphene@2Al(BH4)3 increase to 14% and 26% in the comparison of pure graphene. The first hyperpolarizability (βo) is increased from 0.44 (graphene) to 1295.4 au in graphene@2Al(BH4)3. Our findings suggest that Al(BH4)3-doped graphene could be an effective method for making graphene an efficient nonlinear optical material. [ABSTRACT FROM AUTHOR]

Our capability to analyse and interpret food complexity is limited when traditional analytical methods are used. On the other hand, the utilisation of vibrational spectroscopy (e.g. near- and mid-infrared, Raman spectroscopy) combined with data analytics has provided with a robust tool that has improved the capacity to link in a swift and consistent method the data created during the production, processes, storage and trade of food ingredients and products. These new tools (e.g. vibrational spectroscopy, mathematical modelling and algorithms, the Internet of Things) are providing with the means to better understand and monitor food in the context of sustainable food systems. [ABSTRACT FROM AUTHOR]

Nuts and peanuts are foods that are rich in minerals, vitamins, fibre and healthy fats in addition to antioxidant compounds. However, these food products can be subject to adulterations and fraud mainly due to their cost or contamination as a result of improper handling. Different types and degrees of damage can be caused to consumers due to food fraud, highlighting the serious consequences that can occur when the adulterant is toxic or allergenic. In this paper, portable near-infrared (NIR) spectroscopy combined with multivariate supervised classification was proposed to detect peanuts, Brazil nuts, macadamia nuts and pecan nuts in cashew nut samples, covering a wide concentration range (10.0 to 0.1 % w/w) of adulterants/contaminants. Methods to predict five classes of samples, cashew nuts unadulterated and adulterated with peanuts, Brazil nuts, macadamia nuts and pecan nuts, were developed. Three variable selection strategies were tested: interval partial least squares (iPLS), genetic algorithm (GA) and the combination of iPLS-GA. Partial least squares discriminant analysis (PLS-DA) and soft independent modelling of class analogy (SIMCA) models were compared, and PLS-DA coupled with iPLS-GA provided the best results, with sensitivity between 81 and 93 % and selectivity between 94 and 100 %. Applicability for the rapid and non-destructive detection of fraud and cross-contamination with different types of allergenic nuts with portable equipment was demonstrated. [ABSTRACT FROM AUTHOR]

This study reports the development of niobium-based electroceramics for electrical, optical and high permittivity applications. The conventional solid-state ceramic method was employed to synthesize the ceramics Ce0.8Ga0.2TiNbO6, Pr0.8Ga0.2TiNbO6, Nd0.8Ga0.2TiNbO6 and Sm0.8Ga0.2TiNbO6. Structural studies of the prepared ceramics were carried out by applying X-ray diffraction technique along with vibrational spectroscopic studies. The pattern of the grains on the surface of the samples developed during the sintering was analysed by scanning electron micrograph. Ultraviolet–visible absorption spectra were used to generate the optical band gap for the samples. In addition, the dielectric properties at radio and microwave frequencies were studied. Grain and grain boundary effects on the electrical properties of the ceramics were assessed by applying impedance spectroscopic analysis. The high Q-factor and high dielectric permittivity of samples make them potential candidates for the dielectric resonator applications in communication systems. The impedance spectroscopic analysis confirms that the prepared ceramics exhibit electrical properties like semiconductors at high temperatures. The presence of gallium atoms in lanthanide titanium niobate system resulted in the lowering of sintering temperature and in the betterment of optical and electrical properties of the ceramics. [ABSTRACT FROM AUTHOR]

This work highlights the investigations on the structure, optical, and dielectric properties of Erbium-substituted Lathanide Titanium Niobate ceramics. The ceramics A0.8Er0.2TiNbO6 (A = Ce, Pr, Nd, and Sm) having aeschynite orthorhombic symmetry were synthesized via conventional solid-state ceramic route method. The symmetry of the samples was determined using XRD and vibrational spectroscopic methods. Surface morphology of the sintered samples was investigated with the help of SEM technique. The optical properties of the samples were studied using UV–Vis absorption spectroscopy and the band gap was estimated using Tauc's plot. Photoluminescence spectra of Erbium-substituted Lathanide Titanium Niobate compounds indicated intense emission lines in the visible region. The studies of dielectric properties at room temperature in microwave and radio frequency regions confirmed the suitability of material in the dielectric resonator applications. Complex impedance spectroscopic studies examined the electrical properties of the samples at different temperatures. The developed samples can be treated as suitable functional ceramics for optical and dielectric applications due to its improved dielectric, optical, and sintering properties. [ABSTRACT FROM AUTHOR]

In this work, we investigated the formation of protonated hydrogen cyanide HCNH+ and methylene amine cation CH 2 NH 2 + (both identified in Titan's upper atmosphere) from three different pathways which stem from the interaction between CH4 and N+(3P). As a mechanistic tool, we used the Unified Reaction Valley Approach (URVA) complemented with the Local Mode Analysis (LMA) assessing the strength of the CN bonds formed in these reactions. Our URVA studies could provide a comprehensive overview on bond formation/cleavage processes relevant to the specific mechanism of eight reactions R1– R8 that occur across the three pathways. In addition, we could explain the formation of CH 2 NH 2 + and the appearance of HCNH+ and CHNH 2 + along these paths. Although only smaller molecules are involved in these reactions including isomerization, hydrogen atom abstraction, and hydrogen molecule capture, we found a number of interesting features, such as roaming in reaction R3 or the primary interaction of H2 with the carbon atom in HCNH+ in reaction R8 followed by migration of one of the H2 hydrogen atoms to the nitrogen which is more cost effective than breaking the HH bond first; a feature often found in catalysis. In all cases, charge transfer between carbon and nitrogen could be identified as a driving force for the CN bond formation. As revealed by LMA, the CN bonds formed in reactions R1–R8 cover a broad bond strength range from very weak to very strong, with the CN bond in protonated hydrogen cyanide HCNH+ identified as the strongest of all molecules investigated in this work. Our study demonstrates the large potential of both URVA and LMA to shed new light into these extraterrestrial reactions to help better understand prebiotic processes as well as develop guidelines for future investigations involving areas of complex interstellar chemistry. In particular, the formation of CN bonds as a precursor to the extraterrestrial formation of amino acids will be the focus of future investigations. [ABSTRACT FROM AUTHOR]

Despite the important role of iron in cellular homeostasis, iron overload (IO) is associated with systemic and tissue deposits which damage several organs. In order to reduce the impact caused by IO, invasive diagnosis exams (e.g., biopsies) and minimally invasive methods were developed including computed tomography and magnetic resonance imaging. However, current diagnostic methods are still time-consuming and expensive. A cost-effective solution is using Fourier-transform infrared spectroscopy (FTIR) for real-time and molecular-sensitive biofluid analysis during conventional laboratory exams. In this study, we performed the first evaluation of the accuracy of FTIR for IO diagnosis. The study was performed by collecting FTIR spectra of plasma samples of five rats intravenously injected with iron-dextran and five control rats. We developed a classification model based on principal component analysis and supervised methods including J48, random forest, multilayer perceptron, and radial basis function network. We achieved 100% accuracy for the classification of the IO status and provided a list of possible biomolecules related to the vibrational modes detected. In this preliminary study, we give a first step towards real-time diagnosis for acute IO or intoxication. Furthermore, we have expanded the literature knowledge regarding the pathophysiological changes induced by iron overload. [ABSTRACT FROM AUTHOR]

Textile waste presents a major burden on the environment, contributing to climate change and chemical pollution as toxic dyes and finishing chemicals enter the environment through landfill leachate. Moreover, the majority of textile waste reaching landfills is discarded clothing, which could be reused or recycled. Here we investigate environmentally benign morphology changing of cotton textiles as a precursor for reintegration into a circular materials economy. At 50 °C using low concentrations of acids and bases, the interfiber structures of woven cotton were successfully degraded when treated with the following sequence of chemical treatment: citric acid, urea, sodium hydroxide, ammonium hydroxide, and sodium nitrate. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) reveal separation of the constituent fibers without depolymerization of the cellulose structure, and streaming potential measurements indicate that surface charge effects play a key role in facilitating degradation. The proposed reaction procedures show feasibility of effective waste-fabric recycling processes without chemically intensive processes, in which staple fibers are recovered and can be re-spun into new textiles. [ABSTRACT FROM AUTHOR]

Crystal structures of five salts of 1H-pyrazole-1-carboxamidine, PyCA, with various inorganic acids were determined, (HPyCA)Cl, (HPyCA)Cl·H2O, (HPyCA)Br, (HPyCA)2(I)I3, and (HPyCA)HSO4. Theoretical calculations of the protonation route of PyCA showed that the cationic form present in the studied crystals is energetically privileged. Tautomeric equilibrium constants indicated two isomers as the most stable neutral forms. Calculations for two other tautomers failed resulting in pyrazole and carbodiimid tautomer of cyanamide. Such decomposition is important in a view of guanylation reaction. Hydrogen bonding patterns were studied by means of the graph-set approach. Similarities of the patterns in different crystal structures were demonstrated by the algebraic relations between descriptors of the patterns. The strength of hydrogen bonding network in the crystals was assessed analyzing vibrational spectra. The bands were assigned on the basis of theoretical calculations for the complex [(HPyCA)2Cl4]2– ion and potential energy distribution analysis. The strength of hydrogen bonds was set in the following ascending series (HPyCA)2(I)I3 (4) < (HPyCA)Br (3) < (HPyCA)Cl (1) < (HPyCA)Cl·H2O (2) < (HPyCA)HSO4 (5). [ABSTRACT FROM AUTHOR]

Pistachio is one of the most expensive nuts with having high economic importance in Turkey. It has become more prone to adulteration because of its high commodity value. Peanut with color additives and green pea are generally used to adulterate ground pistachio. Vibrational spectroscopy is a potential technique to detect adulterations in pistachio. The objective of this study was to generate a non-targeted method for portable FT-IR and UV–Vis spectrometers to authenticate pistachio and detect green pea and peanut adulterations. Pistachio granules were adulterated with green pea and peanut at different concentrations (5 to 40% w/w). Spectra were collected by a portable FT-IR spectrometer and by a conventional UV–Vis spectrometer and analyzed by Soft Independent Modeling of Class Analogy (SIMCA) to generate classification algorithms to authenticate pistachio, and Partial Least Square Regression (PLSR) to predict the concentrations of adulterants. SIMCA showed very distinct clusters for pure samples. Moreover, adulterated pistachio samples were discriminated by SIMCA even in low levels of adulteration (5%). Portable FTIR showed excellent performance (rval > 0.93) of predicting the adulterant levels with a standard error of prediction (SEP) 0.66% and 0.80% for green pea and peanut, respectively. Similarly, UV–VIS predicted (rval > 0.93) the adulterant levels with SEP 0.58% and 0.14% for green pea and peanut, respectively. The results supported that portable FT-IR, and UV–Vis units present great potential for real-time surveillance of green pea and peanut adulteration in pistachio. [ABSTRACT FROM AUTHOR]

Aromatic heterocyclic compounds are commonly used in pharmaceutical and agrochemical products. The usage has been also extended in the production of corrosion inhibitors and electronic, opto-electronic, and NLO devices. The four regioisomers of the aromatic heterocyclic molecule, tetrakis(4-pyridyl)cyclobutane (tpcb), were optimized, and their chemical, electronic, and biological properties were examined. The rctt and rtct isomers were isolated and further characterized by the infrared and Raman spectroscopic techniques, and their vibrational modes with attention on important functional groups were discussed. The theoretical vibrational data obtained by DFT/B3LYP/6-311++G(d,p) were in very good agreement with the experimental ones. The occupancy, bond polarization, hybridization of the N-C bond, bonding characteristics between the pyridyl carbon and cyclobutane moiety, and distribution of electron density for the four tpcb isomers have been explored through NBO analysis. The inversion barrier of the cyclobutane moiety was obtained based on the optimized structures of the planar and puckered configurations of the isomers. The rccc isomer exhibited the least electrophilic character compared to the other tpcb isomers. The chemical significance of tpcb has been further explained by the wave function analyses. Molecular docking results revealed that the tpcb ligand would possess a potential anti-viral and anti-bacterial activity via a membrane-permeable mechanism. [ABSTRACT FROM AUTHOR]

In this work, a simplified formulation of our recently developed generalized subsystem vibrational analysis (GSVA) for obtaining intrinsic fragmental vibrations (J Chem Theory Comput 14:2558, 2018) is presented. In contrast to the earlier implementation, which requires the explicit definition of a non-redundant set of internal coordinate parameters to be constructed for the subsystem, the new implementation circumvents this process by employing massless Eckart conditions to the subsystem fragment paired with a Gram–Schmidt orthogonalization to span the same internal vibration space indirectly. This revised version of GSVA (rev-GSVA) can be applied to equilibrium structure as well as transition state structure, and it has been incorporated into the open-source package UniMoVib (https://github.com/zorkzou/UniMoVib). [ABSTRACT FROM AUTHOR]

Some of the major processed horticultural commodities subjected to adulteration are powders, edible oils and juices. This review covers the recent application in the field of vibrational spectroscopic techniques (near and mid-infrared spectroscopy, Raman spectroscopy and hyperspectral imaging) for the determination of authenticity and adulteration in processed horticultural products with an emphasis on powders, edible oils and juices. The review highlights fundamental concepts, limitations and constraints associated with each spectroscopic technique in evaluating the authenticity and adulteration of processed horticultural products. Our findings suggest that the application of infrared spectroscopy (near and mid) is highly suitable for the assessment of powders, oils and juices, while Raman spectroscopy has shown potential in evaluating powders and edible oils. However, these spectroscopic tools still require improvement on measurement accessories and dynamic analytical methods for modern food inspection. Overall, the review of literature suggests that vibrational spectroscopy has the potential to fulfil the industrial need for quality control and authenticity assessment. [ABSTRACT FROM AUTHOR]

The sub-200 cm−1 (sub-6 THz) vibrations of molecular crystals provide identifying features that are characteristic of each solid sample under study. These distinctive vibrational spectra have driven the development of new techniques and instrumentation in analytical spectroscopy. As terahertz time-domain spectroscopy and low-frequency Raman spectroscopy become increasingly prevalent in non-specialist laboratories, the need for a common set of spectral standards for use across these techniques becomes imperative. To meet this need, α-lactose monohydrate, biotin, and L-cystine are proposed here as molecular standards to evaluate instrument performance with both terahertz and Raman spectroscopies, as well serve as benchmarks for quantum mechanical simulations and analyses of these spectra. These substances all reveal a series of readily discernable peaks across the low-frequency region and also over a range of temperatures (295–50 K) making them even more useful. The often overlooked aspect of detailed spectral interpretation and assignment is directly addressed with rigorous solid-state density functional theory simulations of the three compounds based on a standard computational framework. By investigating these proposed molecular crystal standards with commonly available experimental and theoretical approaches, a set of realistic performance expectations can be achieved for both commercial instrumentation and software being used in low-frequency vibrational spectroscopy. [ABSTRACT FROM AUTHOR]

The low-frequency (terahertz) dynamics of condensed phase materials provide valuable insight into numerous bulk phenomena. However, the assignment and interpretation of experimental results require computational methods due to the complex mode types that depend on weak intermolecular forces. Solid-state density functional theory has been used in this regard with great success, yet the selection of specific computational parameters, namely the chosen basis set and density functional, has a profound influence on the accuracy of predicted spectra. In this work, the role of these two parameters is investigated in a series of organic molecular crystals, in order to assess the ability of various methods to reproduce intermolecular forces, and subsequently experimental terahertz spectra. Specifically, naphthalene, oxalic acid, and thymine were chosen based on the varied intermolecular interactions present in each material. The results highlight that unconstrained geometry optimizations can be used as an initial proxy for the accuracy of interatomic forces, with errors in the calculated geometries indicative of subsequent errors in the calculated low-frequency vibrational spectra, providing a powerful metric for the validation of theoretical results. Finally, the origins of the observed shortcomings are analyzed, providing a basic framework for further studies on related materials. [ABSTRACT FROM AUTHOR]

Hydroquinone (HQ) and its clathrate are materials of growing interests, due to their promising applications in energy related science and industries. Recently, many studies have been performed to understand the properties of these materials. Terahertz (THz) spectroscopy is a powerful tool for studying the properties of these materials by non-destructively probing their low-energy (meV) dynamics. Although terahertz spectra of HQ and its clathrates have been measured, a report on the correspondence between THz spectra and low frequency dynamics is still lacking. In this paper, we measure the temperature-dependent THz spectra of both α-HQ (the non-clathrate form) and β-HQ clathrate, with Ar and CO2 as guest species. We also perform density functional theory (DFT) simulations on these materials, in order to assign the spectral features. We find an excellent match between the experimental and the DFT calculated spectra. Using the simulation result, we build connections between the THz spectra and the atomic motions in these materials. In addition, we also perform DFT simulations on β-HQ-He, β-HQ-Ne, and β-HQ-Kr to study the patterns in the change of THz spectra as the guest species changes. [ABSTRACT FROM AUTHOR]

The interplay between FeC and CO bonding in carboxymyoglobin (MbCO) and the role of potential hydrogen bonding between the CO moiety and the side chains of the surrounding protein amino acids have been the subject of numerous experimental and theoretical studies. In this work, we present a quantitative measure for the intrinsic FeC and CO bond strength in MbCO, as well as for CO⋯H bonding, based on the local vibrational mode analysis, originally developed by Konkoli and Cremer. We investigated a gas phase model, two models of the wild-type protein, and 17 protein mutations that change the distal polarity of the heme pocket, as well as two protein mutations of the heme porphyrin ring. Based on local mode force constants, we could quantify for the first time the suggested inverse relationship between the CO and FeC bond strength, the strength of CO⋯H bonding, and how it weakens the CO bond. Combined with the natural orbital analysis, we could also confirm the key role of π back donation between Fe and the CO moiety in determining the FeC bond strength. We further clarified that CO and FeC normal modes couple with other protein motions in the protein environment. Therefore, normal mode frequencies/force constants are not suited as bond strength descriptors and instead their local mode counterparts should be used. Our comprehensive results provide new guidelines for the fine-tuning of existing and the design of MbCO models with specific FeC, CO, and CO⋯H bond strengths. Graphical abstract [ABSTRACT FROM AUTHOR]

Visualizing vibrational motions calculated with different ab initio packages requires dedicated post-processing tools. Here, we present a PyMOL plugin called PyVibMS for visualizing the vibrational motions for both molecular and solid systems calculated by mainstream quantum chemical computer programs including Gaussian, Q–Chem, VASP, and CRYSTAL. Benefiting from the continuing development of the PyMOL platform, PyVibMS provides powerful functionalities and user-friendly interface. PyVibMS was written in Python and its open-source nature makes it flexible and sustainable. As an example, the motions of the Konkoli-Cremer local vibrational modes are shown in this work for the first time. PyVibMS is freely available at https://github.com/smutao/PyVibMS. [ABSTRACT FROM AUTHOR]

Total internal reflection (TIR) optical spectroscopies have been widely used for decades as non-destructive and surface-sensitive measurements of thin films and interfaces. Under TIR conditions, an evanescent wave propagates into the sample layer within a region approximately 50 nm to 2 μm from the interface, which limits the spatial extent of the optical signal. The most common TIR optical spectroscopies are fluorescence (i.e., TIRF) and infrared spectroscopy (i.e., attenuated total reflection infrared). Despite the first report of TIR Raman spectroscopy appearing in 1973, this method has not received the same attention to date. While TIR Raman methods can provide chemical specific information, it has been outshined in many respects by surface-enhanced Raman spectroscopy (SERS). TIR Raman spectroscopy, however, is garnering more interest for analyzing the chemical and physical properties of thin polymer films, self-assembled monolayers (SAMs), multilayered systems, and adsorption at an interface. Herein, we discuss the early experimental and computational work that laid the foundation for recent developments in the use of TIR Raman techniques. Recent applications of TIR Raman spectroscopy as well as modern TIR Raman instruments capable of measuring monolayer-sensitive vibrational modes on smooth metallic surfaces are also discussed. The use of TIR Raman spectroscopy has been on a rise and will continue to push the limits for chemical specific interfacial and thin film measurements. [ABSTRACT FROM AUTHOR]

The field of organometallic chemistry has tremendously grown over the past decades and become an integral part of many areas of chemistry and beyond. Organometallic compounds find a wide use in synthesis, where organometallic compounds are utilized as homogeneous/heterogeneous catalysts or as stoichiometric reagents. In particular, modifying and fine-tuning organometallic catalysts has been at the focus. This requires an in-depth understanding of the complex metalligand (ML) interactions which are playing a key role in determining the diverse properties and rich chemistry of organometallic compounds. We introduce in this article the metal-ligand electronic parameter (MLEP), which is based on the local vibrational ML stretching force constant, fully reflecting the intrinsic strength of this bond. We discuss how local vibrational stretching force constants and other local vibrational properties can be derived from the normal vibrational modes, which are generally delocalized because of mode-mode coupling, via a conversion into local vibrational modes, first introduced by Konkoli and Cremer. The MLEP is ideally suited to set up a scale of bond strength orders, which identifies ML bonds with promising catalytic or other activities. The MLEP fully replaces the Tolman electronic parameter (TEP), an indirect measure, which is based on the normal vibrational CO stretching frequencies of [RnM(CO)mL] complexes and which has been used so far in hundreds of investigations. We show that the TEP is at best a qualitative parameter that may fail. Of course, when it was introduced by Tolman in the 1960s, one could not measure the low-frequency ML vibration directly, and our local mode concept did not exist. However, with these two problems solved, a new area of directly characterizing the ML bond has begun, which will open new avenues for enriching organometallic chemistry and beyond. [ABSTRACT FROM AUTHOR]

A reversible phase transition in 2-methyl-5-nitroanilinium dihydrogen phosphate, (H2m5na)H2PO4, has been found and characterized. Lattice parameters of (H2m5na)H2PO4 change continuously upon cooling with smooth inflection point at 196 K. The crystal symmetry lowers from orthorhombic, space group Pca21, to monoclinic one, P21. Phase transition to the low-temperature phase features a significant movement of the aromatic ring of H2m5na+ ion assisted by the tilting of a nitro group. Structural modifications of the hydrogen-bonding network in (H2m5na)H2PO4 are identified and described with the use of graph-set descriptors; algebraic equations based on the graph-set descriptors are given. Phase transition was also monitored by temperature-dependent IR spectra, which revealed significant alterations in vibrational characteristics within 1000–950 cm−1 and 830–780 cm−1 spectral ranges. Kurtz-Perry test of (H2m5na)H2PO4 shown that relative SHG efficiency is 0.85 that of KDP at room temperature. Low-temperature phase features over four times weaker SHG than room-temperature one. [ABSTRACT FROM AUTHOR]

Calculations of the structures and energies of intermediates of the enzymatic hydrolysis of guanosine triphosphate, performed by means of quantum mechanics and molecular mechanics (QM/MM), suggest a mechanism for chemical transformations of reaction particles in an active site that assumes an amide-imide tautomerism of the side chain of glutamine residue. Positions of vibrational bands and a corresponding band shift upon isotopic substitution 14N → 15N in the side chain of glutamine residue in the active site are predicted for experimental verification of the given mechanism via IR spectroscopy. [ABSTRACT FROM AUTHOR]

The new organic–inorganic hybrid material (C6H7N2S)2[SbCl4]Cl was synthesized by slow evaporation method and characterized by single-crystal X-ray diffraction, infrared absorption, Hirshfeld surface analysis, optical absorption and photoluminescence measurements. The Centro symmetric compound crystallizes in the triclinic system of space group P 1 ¯ with two formula units cell (Z = 2).The crystal structure is composed of a discrete [SbCl4]− anion and two isolated chloride Cl− anions which carried the same negative charge to balance the total charge of this compound surrounded by the 4 pyridiniumethioamide cations. Organic and inorganic parts which are linked by means of hydrogen bonding contacts N–H···Cl with N···Cl length are varied in the range of 3.221–3.456 Å to form a Zero-dimensional network. The infrared study performed at room temperature charge in the 4000–400 cm−1 frequency regions confirms the existence of the organic cation [C6H7N2S]+ and that of the [SbCl4]− anion. The Photoluminescence spectrum exhibits a broad and strong band of luminescence located at 1.95 eV (635 nm), which can be even observed with the naked eye at room temperature and is due to exaction emission. The various intermolecular interactions of the two independent cations and six chloride atoms were examined via Hirshfeld surface analysis. [ABSTRACT FROM AUTHOR]

The LiNi0.8M0.2PO4·3H2O (M = Mn2+, Fe2+) were successfully synthesized with a simple co-precipitation route to obtain the lithium binary transition metal phosphate hydrates, in which the corresponding calcined products can be used as cathode materials in Li-ion batteries. The hydrates and their calcined products were characterized using FTIR/FT Raman spectrophotometer, atomic absorption/atomic emission spectrophotometer, X-ray powder diffraction and TG/DTG/DTA. The morphologies of the synthesized compounds were investigated by using scanning electron microscope technique and found to be the thick-plate particles, which were changed to small-bead particles after the thermal treatment. The influence of the transition metal doping on the strength of hydrogen bonding in the structure of the studied compounds was investigated by using the FTIR and TG/DTG/DTA techniques. Moreover, the decomposition mechanism and vibrational properties of the products were studied and it was found that the H-bond strength and transformation mechanisms of three studied hydrates, namely LiNiPO4·3H2O, LiNi0.8Mn0.2PO4·3H2O and LiNi0.8Fe0.2PO4·3H2O, were significantly different. In addition, based on the results from both vibrational and kinetic properties, the strength of H-bonding of the title compounds was obtained in order of magnitude as LiNiPO4·3H2O > LiNi0.8Fe0.2PO4·3H2O > LiNi0.8Mn0.2PO4·3H2O. [ABSTRACT FROM AUTHOR]

The structural organization of the surface (active) layer and the state of water in composite ultrafiltration membranes have been investigated by means of the methods of vibrational IR spectroscopy and differential scanning calorimetry (DSC). Analysis of the shape of the absorption band of stretching vibrations of hydroxyl groups at ν = 3366.2 cm–1 with an asymmetry coefficient of ~1 and the activity of vibrations of methyl groups with ν = 2884.02 and 2942.35 cm—1 has demonstrated that the bulk supramolecular structure of a cellulose acetate layer of a dry sample is formed by two types of hydrogen bonds and dipole–dipole interactions of carbonyl groups. The interaction of macromolecules in the equatorial plane is formed by a lattice of hydrogen bonds of the (OH...O) type with participation of the only hydroxyl group of a pyranose ring in cellulose acetates. In the axial direction, the supramolecular structure is organized by hydrogen bonds between methine and carbonyl groups of the (CH...O=C) type and dipole interactions of coplanar ordered dipoles of (C=O) groups. The decrease in the intensity and the coefficient of asymmetry down to 0.81 of the absorption band of hydroxyl groups and the absorption band of methyl groups with frequencies ν = 2884.02–2942.35 cm–1 by 2.56 and 3.3 times in water-saturated samples occurs due to the destruction of the supramolecular structure and the reorganization of hydrogen bonds of active groups of cellulose acetate and water molecules blocking intermolecular interactions of the macromolecules. The manifestation of hydroxyl groups with frequencies of 3302.7 and 33 105 sh cm–1 and ν = 3600.6 and ν = 3598.8 sh cm–1 on the absorption band indicates the interaction of associated water molecules of the bound and capillary forms. The absence of the absorption band with ν = 873.53 cm–1 in the water-saturated sample is explained as an empirical indicator of the conformational transition of macromolecules into a linear form. Deconvolution of the endothermic peak on the DSC curve in the temperature range from 50 to 110°C into five Gaussians has demonstrated the multilevel structural organization of water molecules sorbed in pores and between macromolecules of the amorphous phase. [ABSTRACT FROM AUTHOR]

The steric and electronic structures of 1,3-diaza-5-phoaphacyclohexane with the pyridyl substituent at the phosphorus atom and a series of model 1,3-diaza-5-phosphacyclohexanes (potential ligands for the synthesis of luminescent transition metal complexes) were studied using IR and UV spectroscopy combined with quantum chemical calculations. Relationships between the electronic structures, spectral characteristics, and donor—acceptor properties of the substituents were revealed. The relationships can further be used for the target synthesis of complexes with specified optical properties. [ABSTRACT FROM AUTHOR]