Spectra Of Solutions Research Articles

Identification of Ion Pairs in Aqueous NaCl and KCl Solutions in Combination with Raman Spectroscopy, Molecular Dynamics, and Quantum Chemical Calculations

This work summarizes a theoretical analysis of the perturbation on Raman spectra in aqueous NaCl and KCl solutions with the aim to detect ion pairs. The experimental Raman spectra, both polarized and depolarized, are perturbed by these ions to a comparable extent or somewhat less by KCl than NaCl. This result appears to be contrary to the molecular dynamics (MD) simulation showing that the isolated and separated ions of KCl should have a larger perturbation than NaCl, as the solvation shell of K+ is larger than that of Na+. The apparent discrepancy signifies the ion pair formation which is more substantial for KCl than NaCl. The MD simulations and quantum chemical calculations revealed that KCl forms ion pairs more than NaCl and that the ion pair formation reduces the perturbation on the Raman spectra more for KCl. The present analysis shows that the perturbed Raman spectra provide a useful sign to evaluate the ion pair formation in aqueous solutions.

Near ambient pressure–x-ray photoelectron spectroscopy spectra of lithium hexafluorophosphate in ethylene/dimethyl carbonate

Near ambient pressure–x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 5000 Pa. NAP-XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show the survey, Li 1s, P 2p, C 1s, N 1s, O 1s, and F1s NAP-XPS spectra of a Li-based electrolyte solution, which is a material that would be difficult to analyze by conventional XPS. The measurements were performed at 1000 Pa in ambient gas atmosphere to compensate for surface charging. Peak fits of the C 1s, O 1s, and F 1s narrow scans are presented.

Near ambient pressure–x-ray photoelectron spectroscopy spectra of lithium bis(trifluoromethane-sulfonyl) imide in propylene carbonate

Near ambient pressure–x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 5000 Pa. NAP-XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show the survey, Li 1s, S 2p, C 1s, N 1s, O 1s, and F 1s NAP-XPS spectra of a Li-based electrolyte solution, which is a material that would be difficult to analyze by conventional XPS. The measurements were performed at 200 Pa in ambient gas atmosphere to compensate for surface charging. Peak fits of the C 1s, O 1s, and F 1s narrow scans are presented.

Bayesian Regression for Predicting Price Empirical Evidence in American Real Estate

The two foremost aims of classical regression are to assess the structure and magnitude of the relationship between variables. Despite the aforementioned benefits, unlike classical regression, which only offers a point estimate and a confidence interval, Bayesian regression offers the whole spectrum of inferential solutions. The results of this study demonstrate the Bayesian approach's suitability for regression tasks and its advantage in accounting for additional a priori data, which often strengthens studies. Using data from Boston Housing provided by from UCI ML Repository, this study proves that the prior distributions have the benefit of producing analytical, closed-form conclusions, which eliminates the need to use numerical techniques like Markov Chain Monte Carlo (MCMC). Second, software implementations are offered together with formulas for the posterior outcomes that are supplied, clarified, and shown. The assumptions supporting the suggested approach are evaluated in the third step using Bayesian tools. Prior elicitation, posterior calculation, and robustness to prior uncertainty and model sufficiency are the three processes that are essential to Bayesian inference.

Dispersive Optical Solitons with Differential Group Delay Having Multiplicative White Noise by Itô Calculus

The current paper recovers dispersive optical solitons in birefringent fibers that are modeled by the Schrödinger–Hirota equation with differential group delay and white noise. Itô Calculus conducts the preliminary analysis. The G′/G-expansion approach and the enhanced Kudryashov’s scheme gave way to a wide spectrum of soliton solutions with the white noise component reflected in the phase of the soliton.

In Situ Study the Dynamics of Blade‐Coated All‐Polymer Bulk Heterojunction Formation and Impact on Photovoltaic Performance of Solar Cells

All‐polymer solar cells (all‐PSCs) have achieved impressive progress by employing acceptors polymerized from well performing small‐molecule non‐fullerene acceptors. Herein, the device performance and morphology evolution in blade‐coated all‐PSCs based on PBDBT:PF5–Y5 blends prepared from two different solvents, chlorobenzene (CB), and ortho‐xylene (o‐XY) are studied. The absorption spectra in CB solution indicate more ordered conformation for PF5–Y5. The drying process of PBDBT:PF5–Y5 blends is monitored by in situ multifunctional spectroscopy and the final film morphology is characterized with ex situ techniques. Finer‐mixed donor/acceptor nanostructures are obtained in CB‐cast film than that in o‐XY‐cast ones, corresponding to more efficient charge generation in the solar cells. More importantly, the conformation of polymers in solution determines the overall film morphology and the device performance. The relatively more ordered structure in CB‐cast films is beneficial for charge transport and reduced non‐radiative energy loss. Therefore, to achieve high‐performance all‐PSCs with small energy loss, it is crucial to gain favorable aggregation in the initial stage in solution.

Theoretical Study of the Excited States and Luminescent Properties of (H2O)nUO2Cl2 (n = 1–3)

The low-lying excited-state properties of the water-solvated UO2Cl2 complexes, i.e., (H2O)nUO2Cl2 (n = 1-3), below 33,000 cm-1, are investigated based on the ab initio NEVPT2 and CCSD(T) with inclusion of scalar relativistic and spin-orbit coupling effects. The simulated luminescence spectral curves agree well with the experimental spectrum in aqueous solution at -120 °C. Water coordination is found to significantly affect the character of luminescent state, which is changed from the 3Φg state in UO2Cl2 to the 3Δg state in (H2O)2,3UO2Cl2. This is distinctly different from the observed unchanged nature of luminescent state in the cases of Ar coordination to UO2Cl2 and H2O coordination to UO2F2 in the previous work. Furthermore, by combining with the theoretical results for the solvated UO2F2 system, the reason why water coordination does not remarkably change the spectral shape of UO2Cl2, as opposed to UO2F2, was explained based on the analysis of two key spectral parameters, O-U-O symmetrical vibrational frequency and U-O bond length elongation. The roles of ligand field and spin-orbit coupling in the determination of luminescent state character and spectral shape in uranyl dihalide complexes are deeply discussed and summarized. These results deepen our understanding of the luminescent properties of uranyl complexes in aqueous solution.

A conceptual methodology to screen and adopt circular business models in small and medium scale enterprises (SMEs): A case study on child safety seats as a product service system

While small and medium enterprises are already aware of the increasing benefits of resource efficiency, reducing waste, and closing material loops, the adoption of circular economy principles in small and medium enterprises is still nascent. Despite a large body of academic literature providing numerous definitions and business models to elucidate circular economy, these approaches lack systemic research from a small and medium enterprise's perspective and are often vague and overwhelming. Furthermore, small and medium enterprises lack financial and organizational resources to implement a (systemic) change to their already optimized business models. This paper addresses this knowledge gap by presenting a conceptual approach that not only serves as a decision-making tool and a possible starting point towards circular value creation, but also provides an initial estimation on how well forms of circularity can be achieved within the adapted business models. The developed methodology was applied to a complex product within the plastics sector. Starting with the product-disassembly-workshop, an in-depth analysis to identify various circular concepts was then conducted, using design thinking tools. The results are presented and summarized in the form of a decision tree analysis. Using a contradiction matrix and environment mapping tool, it was then attempted to narrow down the circular solution spectrum to a manageable level. To conclude, a cross impact balance analysis was applied to validate the identified business model scenarios. The presented methodology aims to show small and medium enterprises how to generate business model innovations systematically, narrow down the solution space in a structured manner, and how to evaluate the resultant solution options against each other and weigh their trade-offs. The tools and techniques used were chosen in such a way that they can be applied with as few resources and complexity as possible, and therefore can serve as a guidance for small and medium enterprises in their transition towards circular value creation.

Non-Invasive, Reliable, and Fast Quantification of DNA Loading on Gold Nanoparticles by a One-Step Optical Measurement.

An exquisite, versatile, and reproducible quantification of DNA loading on gold nanoparticles (Au NPs) has long been pursued because this loading influences the analytical, therapeutic, and self-assembly behaviors of DNA-Au NPs. Nevertheless, the existing methods used thus far rely solely on the invasive detachment and subsequent spectroscopic quantification of DNA, which are error-prone and highly dependent on trained personnel. Here, we present a non-invasive optical framework that can determine the number of DNA strands on Au NPs by versatile one-step measurement of the visible absorption spectra of DNA-Au NP solutions without any invasive modifications or downstream processes. Using effective medium theory in conjunction with electromagnetic numerical calculation, the change in DNA loading density, resulting from varying the ion concentration, Au NP size, DNA strand length, and surrounding temperature, can be tracked in situ merely by the one-step measurement of visible absorption spectra, which is otherwise impossible to achieve. Moreover, the simplicity and robustness of this method promote reproducible DNA loading quantification regardless of experimental adeptness, which is in stark contrast with existing invasive and multistep methods. Overall, the optical framework outlined in this work can contribute to democratizing research on DNA-Au NPs and facilitating their rapid adoption in transformative applications.

Structure, Optical and Magnetic Properties of Two Isomeric 2-Bromomethylpyridine Cu(II) Complexes [Cu(C6H9NBr)2(NO3)2] with Very Different Binding Motives.

Two isomeric 2-bromomethylpyridine Cu(II) complexes [Cu(C6H9NBr)2(NO3)2] with 2-bromo-5-methylpyridine (L1) and 2-bromo-4-methylpyridine (L2) were synthesized as air-stable blue materials in good yields. The crystal structures were different with [Cu(L1)2(NO3)2] (CuL1) crystallizing in the monoclinic space group P21/c, while the 4-methyl derivative CuL2 was solved and refined in triclinic P1¯. The orientation of the Br substituents in the molecular structure (anti (CuL1) vs. syn (CuL2) conformations) and the geometry around Cu(II) in an overall 4 + 2 distorted coordination was very different with two secondary (axially elongated) Cu-O bonds on each side of the CuN2O2 basal plane in CuL1 or both on one side in CuL2. The two Br substituents in CuL2 come quite close to the Cu(II) centers and to each other (Br⋯Br ~3.7 Å). Regardless of these differences, the thermal behavior (TG/DTA) of both materials is very similar with decomposition starting at around 160 °C and CuO as the final product. In contrast to this, FT-IR and Raman frequencies are markedly different for the two isomers and the UV-vis absorption spectra in solution show marked differences in the π-π* absorptions at 263 (CuL2) or 270 (CuL1) nm and in the ligand-to-metal charge transfer bands at around 320 nm which are pronounced for CuL1 with the higher symmetry at the Cu(II) center, but very weak for CuL2. The T-dependent susceptibility measurements also show very similar results (µeff = 1.98 µB for CuL1 and 2.00 µB for CuL2 and very small Curie-Weiss constants of about -1. The EPR spectra of both complexes show axial symmetry, very similar averaged g values of 2.123 and 2.125, respectively, and no hyper-fine splitting.

The stability of the b-family of peakon equations

In the present work we revisit the b-family model of peakon equations, containing as special cases the b = 2 (Camassa–Holm) and b = 3 (Degasperis–Procesi) integrable examples. We establish information about the point spectrum of the peakon solutions and notably find that for suitably smooth perturbations there exists point spectrum in the right half plane rendering the peakons unstable for b < 1. We explore numerically these ideas in the realm of fixed-point iterations, spectral stability analysis and time-stepping of the model for the different parameter regimes. In particular, we identify exact, stationary (spectrally stable) lefton solutions for , and for , we dynamically identify ramp-cliff solutions as dominant states in this regime. We complement our analysis by examining the breakup of smooth initial data into stable peakons for b > 1. While many of the above dynamical features had been explored in earlier studies, in the present work, we supplement them, wherever possible, with spectral stability computations.

Structural Features of Monoethanolamine Aqueous Solutions with Various Compositions: A Combined Experimental and Theoretical Study Using Vibrational Spectroscopy.

In this work, we studied aqueous solutions of monoethanolamine (MEA), which are widely used to remove CO2 from flue and oil gases. This study combined experimental and theoretical methods of vibrational spectroscopy, using high-temperature infrared spectroscopy, quantum-chemical calculations of theoretical vibrational spectra, and structural electronic and energy characteristics of model structures. MEA has a propensity to form associations between various compositions and structures with water molecules, as well as those composed solely of water molecules. The structural and energy characteristics of such associates were analyzed in terms of their ability to interact and retain carbon dioxide. The influence of elevated temperatures and concentration of aqueous MEA solution on change in the structure of associates has also been investigated. An analysis of theoretical and experimental vibrational spectra allowed us to examine the IR spectra of MEA solutions, and identify the bands responsible for the formation of associates that would sorb CO2 well, but would delay its desorption from the solution.

Multi-mode enhanced Raman scattering spectroscopy using aggregation-free hybrid metal/metal-oxide nanoparticles with intrinsic oxygen vacancies

Un-aggregated plasmonic nanoparticles with a metal oxide coating display persistent enhanced Raman spectra in solution. Enhancement can be further boosted with UV-irradiation (PIERS) to detect nanomolar concentrations of explosive dinitrotoluene.

Study on qualitative identification of aflatoxin solution based on terahertz metamaterial enhancement.

Aflatoxin is the main carcinogen that contaminates agricultural products and foods such as peanuts and corn. There are many kinds of aflatoxins, mainly including aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1) and aflatoxin G2 (AFG2). Different types of aflatoxins have different toxicity and different levels of contamination to agricultural products as well as food. Therefore, the rapid, non-destructive and highly sensitive qualitative identification of aflatoxin species is of great significance to maintain people's life and health. The conventional terahertz detection method can only qualitatively identify the samples at the milligram level, but it is not suitable for the qualitative analysis of trace samples. In this paper, a terahertz metamaterial sensor with "X" composite double-peak structure was designed based on electromagnetic theory to investigate the feasibility of THz-TDS technology based on a metamaterial sensor for the qualitative identification of trace aflatoxin B2, G1 and G2 solutions. Firstly, the terahertz transmission spectra of eight different concentrations of aflatoxin B2, G1 and G2 were collected respectively, and then the differences of terahertz transmission spectra of different aflatoxin species were investigated. Finally, the terahertz transmission spectra of aflatoxin B2, G1 and G2 solutions were modeled and analyzed using chemometric methods. It was found that there were significant differences in the transmission peak curves of different kinds of aflatoxin. Through the comparative analysis of different models, it was concluded that the prediction accuracy of the CARS-RBF-SVM model was the highest, and the accuracy of the calibration set reached 100%. 119 out of 120 predicted samples were correctly predicted, and the prediction accuracy was 99.17%. This study verified the feasibility of qualitative identification of trace aflatoxin B2, G1 and G2 solutions by a metamaterial sensor based on the "X" composite double-peak structure combined with THz-TDS technology, and provided a theoretical basis and a new detection method for the qualitative identification of trace aflatoxins. This will facilitate the rapid, non-destructive and highly sensitive qualitative detection of different kinds of aflatoxins in food and agricultural products. At the same time, this study has important implications for promoting the qualitative detection of other trace substances.

Smoothing of the Time-Resolved Spectral Matrix Obtained by a Streak Camera: Estimation of the Fluorescence Band Parameters

A new method based on singular value decomposition (SVD) was applied to the denoising of the time-resolved spectral matrix (TRSM), which was obtained by a streak camera. The least informative principal components (PCs) were filtered out using the Tikhonov regularization principle. A method for determining the quasi-optimal regularization parameter was suggested. The SVD method was compared with the moving average time direction (MATD) smoothing of the TRSM. Numerical simulations and experimental study of the 3-aminophthalimide (3AP) solution in acetonitrile showed that the SVD smoothing allowed for accurate measurement of signals in peak maximum. Fitting the polynomial modified Gaussian to the smoothed fluorescent bands decreased the measurement errors of the maximum peak position and its width. This method allowed us to obtain kinetics data of the fluorescence band parameters of the 3AP spectrum in an acetonitrile solution. Flexible selection of the quasi-optimal processing parameters and a better time resolution are the main advantages of the SVD method over MATD.

Computational analysis of the vibrational spectra and structure of aqueous cytosine.

The recently developed efficient protocol for the explicit quantum mechanical modeling of the structure and IR spectra of liquids and solutions [Katsyuba et al., J. Phys. Chem. B, 2020, 124, 6664-6670] is used to describe aqueous solutions of cytosine. The same cluster model of a solute surrounded by the first solvation shell of solvent molecules was shown to be sufficient to reproduce experimental vibrational frequencies and relative IR and Raman intensities. An equally good quality of Raman spectra was provided by B3LYP-D3/def2-TZVP and B3LYP-D3/aug-cc-pVDZ simulations. Computations using the PBE functional were sufficient for modeling of the IR spectra but failed in the simulations of Raman scattering. It is shown that strong changes of frequencies and relative intensities of Raman and IR bands of cytosine, caused by its hydration, cannot be completely assigned to the influence of hydrogen bonds (HBs) with 7 or 8 closest water molecules. They are rather ascribed to the combined effect of solute-solute and solute-solvent HBs with the participation of at least 30 water molecules separating cytosine from the bulk solvent. This suggests that the vibrational modes and derivatives of the polarizability and dipole moment of the solute are mainly locally influenced by its first hydration shell, while the influence of bulk water is rather modest.

Green synthesis of silver nanoparticles using Chrysopogon zizanioides root extract and their antibacterial activities

Nanoparticle synthesis is growing at an exponential rate due to its vast variety of applications in optoelectronics, biosensors, bio-nanotechnology, and biomedicine, among other fields. Several biological methods for producing silver nanoparticles are gaining popularity as a result of the wide range of applications to which they may be put. Synthesizing nanoparticles using plants is an environmentally benign and cost-effective alternative to conventional chemical synthesis. An aqueous extract of Chrysopogon zizanioides's root is used to synthesise silver nanoparticles in this study. Different approaches were used to characterise silver nanoparticles, including transmission electron microscopy, UV–vis absorbance spectroscopy, photoluminescence, and antibacterial activity. When viewed through a transmission electron microscope, the synthesised nanoparticles had a spherical form and measured between 10 and 20 nm in size on average. The existence of silver nanoparticles was confirmed by the UV–vis spectra of an aqueous solution containing it, which revealed an absorbance peak at about 411 nm. Finally, it was shown that the biosynthesized silver nanoparticles had a potent antibacterial impact against gram-negative pseudomonas aeruginosa and gram-positive staphylococcus aureus bacteria, both of which are human pathogens.

A Raman spectroscopic and ab initio investigation of aqueous boron speciation under alkaline hydrothermal conditions: evidence for the structure and thermodynamic stability of the diborate ion.

Raman spectra of aqueous sodium borate solutions, with and without excess NaOH, NaCl, and LiCl, have been obtained from perpendicular and parallel polarization measurements acquired using a custom-built sapphire flow cell over the temperature range 25 to 300 °C at 20 MPa. The solvent-corrected reduced isotropic spectra include a large well-defined band at 865 cm-1 which overlaps with the boric acid B(OH)3 band at 879 cm-1, and becomes increasingly intense at elevated temperatures. This band does not correspond to the spectrum of any other previously reported aqueous polyborate ions, all of which have symmetric stretching bands at frequencies below that of borate, [B(OH)4]-, at 745 cm-1. Based on the classic high-temperature potentiometric titration study by R. E. Mesmer, C. F. Baes and F. H. Sweeton, Acidity measurements at elevated temperatures. VI. Boric acid equilibriums, Inorg. Chem., 1972, 11, 537-543, the new band was postulated to arise from a diborate ion, [B2(OH)7]- or [B2O(OH)5]-. Ab initio density functional theory (DFT), together with chemical modelling studies, suggest that it is most likely [B2(OH)7]-. Thermodynamic formation quotients derived from the peak areas showed variations with ionic strength as well as charge-balance discrepancies, which suggest one or more unidentified minor equilibrium species may also be present. The most likely candidate is the divalent diborate species [B2O2(OH)4]2- which is also predicted to have a band near 865 cm-1 and is postulated to be present as a sodium ion pair. These are the first quantitative Raman spectra ever reported for borate-rich solutions under such conditions and provide the first spectroscopic evidence of a diborate species at PWR reactor coolant temperatures.

Synthesis of octochlorine-substituted complexes of cobalt(II) and copper(II) with phthalocyanine

Приведены модифицированная методика синтеза и результаты элементного анализа комплексов железа(II), кобальта(II), никеля(II), меди(II) с октохлорзамещенными фталоцианинами и отнесения полос в УФ- и ИК-спектрах соединений

Structural evolution of water-in-propylene carbonate mixtures revealed by polarized Raman spectroscopy and molecular dynamics.

The liquid structure of systems wherein water is limited in concentration or through geometry is of great interest in various fields such as biology, materials science, and electrochemistry. Here, we present a combined polarized Raman and molecular dynamics investigation of the structural changes that occur as water is added incrementally to propylene carbonate (PC), a polar, aprotic solvent that is important in lithium-ion batteries. Polarized Raman spectra of PC solutions were collected for water mole fractions 0.003 ≤ χwater ≤ 0.296, which encompasses the solubility range of water in PC. The novel approach taken herein provides additional hydrogen bond and solvation characterization of this system that has not been achievable in previous studies. Analysis of the polarized carbonyl Raman band in conjunction with simulations demonstrated that the bulk structure of the solvent remained unperturbed upon the addition of water. Experimental spectra in the O-H stretching region were decomposed through Gaussian fitting into sub-bands and comparison to studies of dilute HOD in D2O. With the aid of simulations, we identified these different bands as water arrangements having different degrees of hydrogen bonding. The observed water structure within PC indicates that water tends to self-aggregate, forming a hydrogen bond network that is distinctly different from the bulk and dependent on concentration. For example, at moderate concentrations, the most likely aggregate structures are chains of water molecules, each with two hydrogen bonds.