Stretching Vibration Band Research Articles

Potential Recognition Layer in Electrochemical Sensor: A Comparative Characterization of p-Cyano Schiff Base Compounds

The effective conjugation of electrons in aromatic Schiff bases has been utilized as an electrochemical sensor in forensic, pharmaceutical and environmental applications. The use of the Schiff base enhances the sensitivity and selectivity of the sensor. In this study, p-cyano Schiff base derived from 4-(4-aminostyryl)benzonitrile and three different aldehydes were synthesized. The spectroscopic techniques via Fourier transform-infrared spectroscopy (FT-IR), Uv-Vis spectrophotometry and Nuclear Magnetic Resonance (NMR) of 1H and 13C were used for structural elucidation resulted compounds. The targeted p-cyano Schiff base showed a clear imine (C=N) stretching vibration band at 1681-1708 cm-1, n→π* electronic transition at 355-360 nm in UV-Vis and a singlet: 8.34-8.39 ppm and 118.07-119.09 ppm for 1H and 13C NMR, respectively, supporting the formation of Schiff bases. The application of Schiff base as spacer in electrochemical DNA (E-DNA) sensor has not been much research done on it so far. The obtained compounds are potentially valuable for electrochemical-DNA sensor study in the future.

Intra-operative Raman spectroscopy and ex vivo Raman mapping for assessment of cartilage degradation

The development of a label-free, non-destructive and safe analytical method such as Raman spectroscopy for assessing cartilage degradation is highly desirable. Compared to non-optical imaging modalities, Raman mapping offers a more sensitive means of directly assessing the chemical composition of cartilage in three-dimensional space and the potential to monitor cartilage degeneration to inform intervention and treatment strategies. Herein, we report the application of Raman spectroscopic methods ex vivo and at arthroscopy to identify molecular alterations in cartilage specimens containing minor focal lesions characteristic of the early disease phase. Our initial ex vivo analysis, obtained by single-point Raman spectroscopy of cartilage samples, supports previous findings based on S-O stretching vibration bands associated with sulphated glycosaminoglycans (sGAGs). We extended the analyses to the high-wavenumber region where we observed that vibrational bands assigned to C-H and O-H stretching modes discriminated early cartilage alterations from healthy cartilage samples. Furthermore, we performed a proof-of-concept in-clinic study using a custom-built optical probe to acquire Raman spectral measurements for the first time in patients undergoing arthroscopy of knee joints. Spectra were obtained with adequate signal-to-noise ratios that similarly discriminated between lesion and adjacent cartilage sites and identified reductions in sGAGs in apparently healthy cartilage. Building on this, we present initial results from Raman mapping to spatially resolve the molecular constituents of cartilage through its depth and across a lesion. Mapping revealed a non-uniform and reduced sGAG distribution within the lesion and peripheral cartilage that was otherwise visually normal, similar to the in-clinic observations, showing that the degradative influence of the lesion extended beyond its border. This was accompanied by a decreased fluorescence signal intensity, which suggests that fluorescence may provide valuable information as an adjunct to the Raman signal in discriminating normal and degenerating cartilage. This work demonstrates the value of Raman mapping over single-point Raman measurements for the analysis of the anisotropy of articular cartilage and highlights the potential of the technology for in vivo articular joint arthroscopy applications.

Impact of cadmium substitution on the structural, spectral, dielectric and magnetic properties of Z-type hexaferrites synthesized via sol-gel route

Cadmium substituted Z-type hexaferrites are prepared via the sol-gel route. The phase temperature of pre-sintered materials is studied from the thermal analysis. The single-phase of Z-type hexaferrite is found through X-ray diffraction investigation. The Crystallite sizes of the entire samples are evaluated within the range of 14–15 nm. The Fe–O stretching vibration band at 566 cm−1 is confirmed from Fourier transform infrared spectroscopy. Saturation magnetization (Ms) coercivity (Hc) and remanence (Mr) is examined by a vibrating sample magnetometer. The magnitude of Ms has been increased from 45.41 to 56.35 emu/g with an increase of Cd2+ concentration. The magnitude of Hc increased from 950.79 to 2186.95 Oe with an increment of Cd2+ concentration. Small values of squareness ratio (less than 0.5) showed the hard and single magnetic domain nature of the materials. The dielectric properties were analyzed using an impedance analyzer. Dielectric parameters show an increasing trend with the substitution of Cd2+. The maximum values of quality factor up to 17,000 and 10,000 are observed for sample Ba2·85Cd0·15Co2Fe24O41 at 1 GHz and 2.7 GHz, respectively. The high value of the Q-factor shows that these ferrites can be applicable for the formation of resonant circuits and multilayer chip inductors.

In vitro studies of Pluronic F127 coated magnetic silica nanocarriers for drug delivery system targeting liver cancer

In this study we synthesized and characterized iron oxide and mesoporous silica coated with Pluronic F127 nanocarriers using hydrothermal technique. The prepared nanoparticles were used as carriers for doxorubixin (DOX). The dynamic light scattering (DLS) of MNPs, MNPs-SiO2-F127-2% and MNPs-SiO2-F127-4% showed an average particle sizes of about 98.9, 127.6, and 136.2 nm, respectively. Furthermore, X-ray diffraction (XRD) analysis demonstrated that the as-prepared nanocarriers were crystalline, and the diffraction peak at 2θ = 35.44° in the XRD profiles of the nanocarriers corresponded to the (311) plane of Fe3O4. The peaks in the wavenumber range of 1630–1091 cm−1 observed in the Fourier-transform infrared (FTIR) spectra of the synthesized nanocarriers corresponded to the stretching vibration bands of Si–O bonds, demonstrating the successful coating of SiO2 on the surface of MNPs. The X-ray absorption near-edge spectra (XANES) of Fe atoms of MNPs, MNPs-SiO2-F127-2% and MNPs-SiO2-F127-4% revealed the presence of an absorbance peak (7112 eV) characteristic to the 1 s-to-3d transition. Cytotoxicity test confirmed that MNPs, MNPs-SiO2-F127-2% and MNPs-SiO2-F127-4% at different concentrations showed no significant cell toxicity toward the HEK293T and HepG2 cells. Additionally, MTT reduction results revealed that, after DOX was encapsulated in MNPs-SiO2-F127-2% and MNPs-SiO2-F127-4% nanocarriers, cell apoptosis was increased. In vitro analysis of the DOX release profile revealed that drug release was pH-dependent, and more DOX was released in acidic than in neutral microenvironments. In this study, we aimed to develop an advanced and innovative treatment against liver cancer using nanocarriers for DOX delivery. The developed drug delivery system or nanocarriers could improve the targeted DOX delivery for typical cancer treatment.

WITHDRAWN: Formulation & evaluation of β-glycyrrhetinic acid patches with natural bioenhancer

Abstract The main of the present investigation is to prepare and evaluate the patches of 18β-glycyrrhitic acid with synthetic polymers. For reservoir type patch drug and polymer selected were 18 β-glycyrrhetinic acid and carbopol 934. Infrared spectra were recorded using FTIR equipment by the potassium bromide disc method at wavelength range between 4000 and 400 cm−1. 23 factorial design was employed to study the effect of independent variables (gel base, penetration enhancer, rate controlling membrane) on dependent variable (% drug release). The patches were evaluated on the basis of percentage drug content, permeation, skin irritancy test and stability studies. White colour powder, tasteless, odourless. It is freely soluble in ethanol, chloroform. Melting point: 294°C. Infrared absorption spectroscopy (IR) of 18 β- glycyrrhetinic acid showed sharp band at 603, 1380, 1612, 1715 and 1760 cm−1 due to stretching vibration bands of aromatic ring, –CH3, C = C (Cyclic), C = O and –COOH respectively. API (18 β-glycyrrhetinic acid) exhibited peak at 293.9°C accordance with its melting point (292–297°C). CONCLUSION- Reservoir type F4 patch formulated using 5% menthol, 42% ethanol, 50 g carbopol934 gel base with 0.5% piperine as bioenhancer. The present study was one of the few attempts to incorporate phytconstituents in transdermal system and it needs to be further optimized and characterised. These types of herbal formulations possess tremendous potential for the treatment of some of the disease.

Evaluation of interactions of multi-walled carbon nanotubes with benzoic acid and its 2-halogeno derivatives and their cytotoxicity

In this study, interactions of multi-walled carbon nanotubes (MWCNTs) with benzoic acid and 2-halogeno (F−, Cl− and Br−) derivatives were investigated. In addition, these compounds were determined to be cytotoxic on Primary Peripheral Blood Mononuclear cells. Adsorption percentages of MWCNTs exposed to these acids at the same concentration for 24 hours were calculated. Raman spectroscopy, Fourier Transform Infrared Spectrocsopy (FT-IR) and Scanning Electron Microscope (SEM) techniques were used to determine the chemical and physical changes caused by acid species on the structure of MWCNTs. As a result of the investigations, it was determined that 2-bromobenzoic acid (BrBA) was adsorbed most favorably by the structure. The structure adsorbed the benzoic acid derivatives better than benzoic acid (BA). The least defect occurred in the sample subjected to BrBA. It was found that there was no correlation between absorption rates and defect occurrences in the structure. SEM results indicate aggregation, tube curl, and filling in inter-tube spaces in samples where absorption is intense. In FT-IR spectra of all structures obtained, the characteristic vibration band related to MWCNTs, and C = O stretching vibration band of the benzoic acid and its derivatives were observed around 1450 and 1680 cm−1, respectively.

Investigation of phosphate removal mechanisms by a lanthanum hydroxide adsorbent using p-XRD, FTIR and XPS

Macroscopic batch experiments and microscopic spectroscopic characterization by powder X-ray diffraction (p-XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were employed to accurately study the phosphate adsorption process onto lanthanum hydroxide adsorbent. The relatively low La release after phosphate adsorption suggested the formation of surface co-precipitation of lanthanum phosphate beyond the Lewis acid-base interaction under the acidic conditions. The maximum adsorption capacities calculated by the Langmuir isotherm at pH 4.0 and 8.0 were 122.0 mg/g and 109.9 mg/g, respectively. Cl−, SO42– and HCO3– on phosphate removal negligibly impacted on phosphate adsorption, while acetate slightly retarded the adsorption. The fitted FTIR spectra of P−O stretching vibration bands in 900–1200 cm−1 range indicated that diprotonated bidentate binuclear or monoprotonated bidentate mononuclear complexes were the dominant surface configurations at pH 4–9. Diprotonated bidentate binuclear complexes were dominant at pH 3 and monoprotonated bidentate binuclear complexes were the major configurations at pH > 9. The high resolution scans of La 3d, O 1s and P 2p spectra before and after phosphate adsorption and lanthanum phosphate indicated that inner-sphere surface complexes formed through the ligand exchange reaction, which were further determined to be rhabdophane (LaPO4·0.5H2O) by p-XRD analysis.

Hydrogen defects in feldspars: defect properties and implications for water solubility in feldspar

Hydrogen defects can strongly affect mechanical and chemical properties of feldspars. To get insight into the behavior of such defects, alkali feldspar and plagioclase of igneous origin were studied combining IR spectroscopy with heating experiments under well-controlled conditions. Near-infrared spectra show that OH groups are the predominant hydrous species in these feldspars but presence of minor amounts of molecular H2O cannot be excluded. Short-term annealing at 400–800 °C produces a small but significant irreversible change in the OH stretching vibration band which is attributed to relaxation of the feldspar structure. Polarized mid-infrared spectra of sanidine, adularia, and plagioclase recorded in situ at temperatures up to 600 °C show reversible shifts of maxima toward higher wavenumber and an overall decrease in integrated intensities. The pleochroic features of the OH vibration bands, i.e., the predominant orientation of OH dipoles along the crystallographic a axis in all feldspars and the additional band component perpendicular to the (010) plane in sanidine are still present in the high-temperature spectra. Different behavior during long-term annealing at high temperature was found for the alkali feldspars and the plagioclases. At 900–1000 °C, the Eifel sanidines rapidly lost about one quarter of the initial water content which is attributed to a weakly bound hydrogen species in the feldspar structure. The remaining hydrogen is very strongly bound and was still detectable in 0.7–0.9 mm thick sections after annealing for 108 days at 1000 °C in air dried by phosphorus pentoxide. In contrast, a 1-mm-thick section of plagioclase completely lost hydrogen during heating in air within 8 days at 1000 °C. After partial dehydration, the pleochroic behavior of the OH absorption bands of the feldspars was basically preserved except that the 3050 cm−1 band of the sanidine, oriented perpendicular to (010), becomes more pronounced than the 3400 cm−1 band, oriented parallel to the a direction. Annealing experiments at 1000 °C under controlled water pressures indicate equilibrium solubilities of several tens of ppm H2O in the plagioclases and more than 100 ppm H2O in the alkali feldspars already at 1 bar water pressure. The variation of the water content with H2O pressure and spectroscopic observations indicates that the water content in the feldspars is determined not only by the water pressure but also by already existing defects. Vacancies on alkali sites (VA1) may accommodate H2O molecules, possibly with subsequent hydrolysis of network bonds to minimize local stress. A likely explanation for the strongly bound hydrogen in the sanidine is a coupled substitution of H+ + Al3+ for Si4+ (AlOH defect) where the protons are located on interstitial sites. This incorporation model is supported by the complete recovery of the defects in H2O vapor after previous proton/alkali exchange in alkali chloride vapor at 1000 °C.

Comparative investigation of the influence of kaolin and dolomite on the properties of polyurethane foam

This work investigates the influence of kaolin and dolomite on the properties of polyurethane foam. The selected fillers were pulverized and sieved to obtained < 90 μm that were used as reinforcements in the polyurethane matrix in a randomly dispersed mode. The matrix constituents were mixed in the same ratio while fillers were introduced via a one-shot system approach in predetermined proportions of 3–7 wt.%. The work was carried out to identify optimum fillers to be utilized in the production of polyurethane rigid foams given the effect of the fillers on the physical, mechanical, and chemical properties of the foam. FTIR, XRF, and SEM and mechanical property tests were carried out on the filled polyurethane foam. The presence of the fillers in the foam showed a rupture in the structure of the foams with the cells having similar arrangements. The addition of dolomite and Kaolin degrades the sulfonic acid groups and promoted the appearance of Si–O stretching vibration band. The density, hardness, flexural and compressive strengths of the polyurethane foam were enhanced with the the addition of dolomite and kaolin particles.

Structural, magnetic and dielectric study of Fe2O3 nanoparticles obtained through exploding wire technique

We propose an exploding wire technique based facile approach to prepare Fe2O3 nanoparticles in ambient conditions. TG-DSC analysis of the prepared precursor (Fe(OH)3) nanoparticles were done. The phase, lattice parameter and the average crystallite size were evaluated through X-ray diffraction analysis. The morphology of prepared nanoparticles was studied by scanning electron microscopy and Transmission electron microscope. The functional group formation of Fe2O3 nanoparticles and intrinsic stretching vibration bands of Fe–O were estimated through FTIR analysis. The direct band gap of Fe2O3 nanoparticles occurring in conjunction with indirect band gaps was established via Tauc plot. The magnetic parameters were studied through Mössbauer spectroscopy, ESR, M-H and M-T plot analysis. The attributes of dielectric behaviour like dielectric constant (ε′), loss tangent (tan δ), dielectric loss (ε″) and alternating current (AC) conductivity (σAC) were measured at various temperatures in the frequency range of 10 Hz-106 KHz.

Crystal structure and Raman spectroscopic studies of OH stretching vibrations in Zn-rich fluor-elbaite

Abstract Zinc-rich fluor-elbaite from Piława Górna, Poland, was studied by electron microprobe (EPMA), single-crystal X-ray diffraction (SREF), and Raman spectroscopy (RS) to check the possibility of the application of RS to draw crystal-chemical conclusions for Al-rich and Li-bearing tourmalines on basis of the O–H stretching vibrations in the spectral range 3400–3800 cm–1. This tourmaline, forming a thin metasomatic zone around gahnite, features varying compositions with a ZnO content reaching in the studied fragment of 5.70(12) wt%. The crystal structure of this Zn-rich fluor-elbaite [a = 15.921(1), c = 7.127(1) Å] was refined with a R1 value of 1.67%. Its formula was determined on the basis of electron-microprobe and structure refinement as (Na0.84☐0.14Ca0.01)XΣ1.00(Al1.06Li0.84Zn0.69Fe0.322+Mn0.09)YΣ3.00AlZ6(BO3)3(Si6TO18)(OH)3V(F0.65OH0.26O0.09)W. The deconvolution of the O–H stretching vibration bands, performed by fitting of an input model of component bands with Gaussian function shapes for the empirical spectrum, indicates that each of the three maxima assigned for VOH bonded to YAl3+, Y2+, and YLi+ and with the total integral intensity of at least 75% of the total OH content could be resolved into 1 to 3 bands, depending on the X-site occupation (vacancies, Na+, and Ca2+). The deconvolution indicates further that several low intense bands of WO–H modes above a Raman shift of 3600 cm–1, totally reaching ≤25%, are dependent on the occupation of triplets of YYY cations bonded to the hydroxyl. These WO–H modes are also influenced by the X-site occupation. Due to ordering of all octahedral cations (except Al) at the Y site and a complete occupation of the Z site by Al and the V site by OH, it seems possible to evaluate the Li and OH contents in a Al-rich and Li-bearing tourmaline directly from the Raman spectrum. By using the ratio VOHIYAlZAlZAl/(VOHIYZZ + WOHIYYY) as evaluated from RS, corresponding to the ratio YAl/V+WOH in the crystal, the formula of the Zn-rich fluor-elbaite can be calculated as (Na0.85☐0.14Ca0.01)XΣ1.00(Al1.11Y1.112+Li0.78)YΣ3.00AlZ6(BO3)3(Si6O18)(OH)3(F0.65OH0.13O0.22), where Y 2+ = Zn + Fe + Mn. The formula, determined only on basis of EPMA and deconvolution of RS in the O–H stretching bands, corresponds very well (≤1 SD range of EPMA) to the formula determined on basis of EPMA and SREF. This result implicates that the O–H stretching vibrations, measured by Raman spectroscopy, could be applied for Al-rich and Li-bearing tourmalines as a useful tool for providing additional information for determining the crystal-chemical formula. It is also very helpful when crystal structural data are not available.

The Identification of Multiple Crystalline Zinc Soap Structures Using Infrared Spectroscopy.

The formation of crystalline zinc soaps (zinc salts of fatty acids) in oil paint layers is a common sign of paint degradation. In this study, we have used infrared spectroscopy to systematically identify differences in structure and composition of crystalline zinc soap phases, and report data analysis methods for structure attribution in challenging oil paint samples. Supported by reported crystal structures, it was possible to distinguish two distinct types of zinc soap geometry: a highly symmetrical packing for long-chain saturated soaps (type B) and an alternating packing for zinc soaps with short, unsaturated, or dicarboxylic chains (type A). These two types of packing can be identified by a single or split asymmetric COO stretch vibration band. With this new information, we studied the structure and composition of zinc soaps formed in a zinc white model paint and in a cross-section from the painting Equations in Space by Lawren Harris. Using non-negative matrix factorization, band integration and band position maps, it was possible to clearly identify zinc azelate in the model paint and map its spatial distribution. The same methods showed that the paint cross-section contained both types of zinc soap structure within the same paint layer, with the less symmetrical structure appearing only at the interface with the ground layer. The results give valuable information on the internal chemistry of oil paint layers, and the demonstrated methods can find widespread application for in-depth analysis of infrared microscopy data.

Quantitative Anisotropic Analysis of Molecular Orientation in Amorphous N2O at 6 K by Infrared Multiple-Angle Incidence Resolution Spectrometry.

The existence of molecular orientational order in nanometer-thick films of molecules has long been implied by surface potential measurements. However, direct quantitative determination of the molecular orientation is challenging, especially for metastable amorphous thin films at low temperatures. This study quantifies molecular orientation in amorphous N2O at 6 K using infrared multiple-angle incidence resolution spectrometry (IR-MAIRS). The intensity ratio of the weak antisymmetric stretching vibration band of the 14N15NO isotopomer between the in-plane and out-of-plane IR-MAIRS spectra provides an average molecular orientation angle of 65° from the surface normal. No discernible change is observed in the orientation angle when a different substrate material is used (Si and Ar) at 6 K or the Si substrate temperature is changed in the range of 6-14 K. This suggests that the transient mobility of N2O during physisorption is key in governing the molecular orientation in amorphous N2O.

Determination of the total content of aromatic hydrocarbons by Fourier-transform IR spectroscopy in the products of diesel hydrofining

A comparative analysis of current methods for determination of aromatic hydrocarbons in the components of diesel fuel revealed that IR spectrometry appeared to be the most optimal method for operational control of the content of aromatic hydrocarbons in medium distillate products of the hydrogenation process. We developed a procedure for quantitative determination of aromatic hydrocarbons in the components of diesel fuel using IR Fourier spectroscopy. The analysis of absorption spectra of the components of diesel fuel revealed that the optical density of the stretching vibration band of the aromatic ring is proportional to the quantitative content of aromatic hydrocarbons (AHC) in the components of diesel fuel. One of the components for compounding diesel fuels obtained at JSC «ANKhK» during hydrotreating of raw materials under severe conditions (30 MPa, 380 – 400°C) was selected as an object of the study. Conditions of IR spectrometric analysis (wave number — 1606.5 cm–1, cell material — NaCl, absorbing layer thickness — 0.1 cm) were specified after recording of the absorption spectrum of the purified component. To construct a calibration dependence the total AHC content and corresponding optical density of the sample were determined by the methods of HPLC and IR spectrometry, respectively. The samples of hydrogenate under study (taken at different timepoints) contained 1 – 8% AHC on average depending on the parameters of a continuously operating unit. The characteristics of the proposed procedure were evaluated in accordance with the requirements of RMG 76–2014. The correctness of the obtained results of AHC determination was confirmed in comparison with the data of independent (tetrimetric) analysis. The use of the developed method in analysis of other components of diesel fuel, requires additional studies to determine the interfering substances and assess their impact on the accuracy of AHC determination.

Adsorption of a poorly water-soluble drug onto porous calcium silicate by the sealed heating method

To improve the bioavailability of orally-administered drug, solubilization of poorly water-soluble drug is important. The solubility of a drug in its amorphous form is known to be higher than in its crystalline form. In this study, we attempted to adsorb a sublimable drug onto porous calcium silicate (Florite®, FLR) or non-porous calcium silicate (NPCS) by the sealed heating (SH) method and evaporated (EV) method. Ibuprofen (IBU) was used as the poorly water-soluble, sublimable drug. The physicochemical properties of samples were investigated using powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and dissolution test. From the PXRD and DSC results, IBU crystals were adsorbed and amorphized by the SH and EV methods with FLR. From the results of FTIR, the shift to a higher frequency by the carbonyl stretching vibration band of IBU suggests an intermolecular interaction between IBU and FLR. In SH with FLR, improved solubilization was observed. IBU adsorbed onto FLR showed a greater dissolution rate than the IBU crystals or NPCS. Thus, the petal-like structure of FLR may be an effective method to adsorb IBU onto FLR using the SH method.

Synthesis and structure of sodium 1-alkoxy-1,4-dioxo-2-alkenolates and bis-(4-alkyl(aryl)- 1-oxo-1-alkoxyalkane-2,4-dionato) metals (II) based on them

A priority task in contemporary organic chemistry consists in the synthesis of practically useful metal complexes having carbonyl-containing ligands. The present article details the isolation of several new bis-(4-alkyl(aryl)-1-oxo-1-alkoxyalkane-2,4-dionato) metals (II) via complex formation of metal salts of (zinc (II), copper (II) and nickel (II)) with sodium 1-alkoxy-1,4-dioxo-2-alkenolates obtained by condensation of alkyl (aryl) methyl ketones with dialkyl oxalates in the presence of sodium or sodium hydride as a condensing reagent. The structure of the synthesised sodium oxoenolates and metal complexes was confirmed by spectral analysis methods (IR, NMR 1 H-, NMR 13 C-spectroscopy and mass spectrometry). In the IR spectra of the solid samples of the isolated compounds, stretching vibrations bands of ester carbonyl groups were identified, as well as high-intensity ether bands due to the vibrations of С-О-С bonds. For compounds containing aromatic fragments, bands corresponding to vibrations of monosubstituted benzene rings were found in the IR spectra. The NMR spectra of 1 H of sodium oxoenolates and metal complexes recorded in DMSO-d 6 demonstrated characteristic signals of ethoxy and n - butoxy fragments, methine protons, as well as protons of aromatic rings. Chemical shifts of carbon atoms in the NMR spectra 13 C of sodium oxoenolates correspond well to the reference values. In the mass spectra of synthesised compounds recorded in electrospray mode, signals of protonated and cationised molecules were observed [M+H] + , [M+NH 4 ] + , [M+Na] + , [M+K] + . Using quantum chemical methods, the models of the obtained compounds were constructed along with a calculation of the formation energies and dissociation constants. Optimisation of the geometric parameters of the equilibrium states of sodium oxoenolate and metal complexes was carried out using the following two methods: density functional theory (DFT) and self-consistent field (SCF). The relative formation energies indicate high stability of the synthesised substances, while, according to the data obtained, copper complexes are characterised by greater stability in the gas phase as compared to zinc and nickel.

Interactions of CO2 with the homologous series of СnMIMBF4 ionic liquids studied in situ ATR-FTIR spectroscopy: spectral characteristics, thermodynamic parameters and their correlation

In this work, in situ ATR-FTIR spectroscopy was used to study the interaction of CO2 and a series of 1-alkyl-3-methylimidazolium tetrafluoroborate СnMIMBF4 (n = 2, 4, 6, 8, 10) ionic liquids. A detailed analysis of the infrared spectra acquired from ionic liquids and sorbed СО2 was performed as ionic liquids with different the alkyl chain lengths were subjected to changing pressures of СО2 and temperature. With a longer alkyl chain length, an increase in the shift of the CH stretching vibrations bands of alkyl groups and BF stretching vibrations of BF4− anions is observed during CO2 sorption. This indicates the disaggregation of alkyl chains and anions. There is a correlation with the position of the wavenumber of the ν3 asymmetric stretching CO2 band and the length of the alkyl chain. It was found that some of the CO2 adsorbed by ionic liquids does not interact with the ionic liquid but is “free” in the bulk of the alkyl chains. For the first time, ATR-FTIR spectroscopy was used to determine the thermodynamic parameters of CO2 sorption in ionic liquids. It was demonstrated that the values of enthalpy and entropy obtained by analysis of the ATR-FTIR spectra are consistent the data obtained by other methods. A correlation was found between the enthalpy of sorption of CO2 and the wavenumber of the ν3 band. This opens up the possibility of using CO2 as an IR-sensitive probe molecule to characterize the acid-base properties of ionic liquids and determine the enthalpy of CO2 sorption.

Perovskite Nanocrystal Fluorescence-Linked Immunosorbent Assay Methodology for Sensitive Point-of-Care Biological Test

Summary Quantitative fluorescence immunoassay is a vital and convenient method in point-of-care (POC) testing for food safety and clinical healthcare. However, current marking materials, from organic luciferin to quantum dots, still lack the requirement of increasing need for multiple targets of interest because of their too broad emission. Here, a new label material, perovskite nanocrystals (Pe-NCs), with a narrower photoluminescence spectrum is reported, and a sensitive and quantitative immunoassay method named the perovskite nanocrystal fluorescence-linked immunosorbent assay is preliminarily demonstrated. The key point of realizing water-dispersed and stable Pe-NCs was addressed by functionalizing with hydroxyl groups. The fluorescent probes (perovskite antibody) were constructed via electrostatic adsorption with narrow full-width at half-maximum (∼18 nm), laying the foundation for future study of multi-target detection. Both indirect competitive immunity and sandwich immunoassay were successfully demonstrated. This work provides a possible label material for POC tests and may open up a promising avenue of next-generation immunoassay.

Use of Raman spectroscopy to assess nitrate uptake by calcined LDH phases

Layered double hydroxides (LDHs) are natural or synthetic compounds with a layered structure that become mixed oxides of the metals that contain upon calcination at 450–700 °C. The resulting oxides have shown to be excellent solid sorbents for nitrate ions in aqueous solutions. The structure of the original LDH is recovered by rehydration as a result of the so-called “memory effect”. This process, which follows a Lagergren´s pseudo-first order kinetic model, is monitored via the NO stretching vibration band for nitrate ion at 1051 cm–1 in the Raman spectrum. The nitrate uptake is mainly governed by the temperature and the metal ratio in the initial LDH. At higher Mg/Al ratio, the nitrate adsorption rate was lower. Unlike, it was increased with the adsorption temperature with non-linear response, suggesting an endothermic process. The obtained results present Raman spectroscopy a reliable choice for monitoring nitrate uptake, overcoming to many existing alternatives in terms of accuracy and expeditiousness.

Study on degrees of mesomorphic zone of polymer. Ⅲ.Determination of the degree of crystallinity of Eucommia Ulmoides gum by VTFTIR and VTWAXD

Eucommia Ulmoides (EU) gum will crystallize easily at room temperature due to the regular trans-1,4-polyisoprene (TPI) molecular structure. Around the skeleton stretching vibration band of TPI, its FTIR spectrum showed 5 weak crystalline peaks decrease as temperature increase, and there are also two amorphous peaks (845 cm−1 and 668 cm−1) increase as temperature increase. According to this phenomenon, Variable Temperature Fourier Transform Infrared Spectrum (VTFTIR) and Variable Temperature Wide Angle X-ray Diffraction (VTWAXD) have been taken to analyze the degree of crystallinity of EU gum. In addition to the ratio of crystalline zone, the result determined by VTFTIR also involve the mesomorphic zone, which make it higher than the result determined by VTWAXD. Through the comparative analysis of VTFTIR and VTWAXD, it has been proved that the ratio of crystalline zone, mesomorphic zone, amorphous zone in EU gum were respectively 39.8%, 27.6%, 32.6% at room temperature. Based on the Density Measurement and the three-phase model theory, the density gradient function of the mesomorphic zone of EU gum was firstly proposed. Below 60 °C, the density of the mesomorphic does not change with the temperature, approximately 0.931g/cm−3. Above 60 °C, the density of the mesomorphic decreases with the temperature increasing, and finally drops to 0.905g/cm−3 at 80 °C, which is equal to the density of the complete amorphous zone.