IR Spectral Investigations Research Articles

CRYPTOMELANE MODIFIED WITH TRANSITION METAL IONS: STRUCTURE AND CATALYTIC ACTIVITY IN THE REACTION OF OZONE DECOMPOSITION

Cryptomelane, OMS-2, and cryptomelane modified with transition metal ions, M/OMS-2 (M = Cu2+, Co2+, Fe3+), were synthesized by the reaction of KMnO4 reduction with manganous salts (MnCl2 and MnSO4) by the reflux method. The samples thus synthesized were characterized by X-ray diffraction and IR spectroscopic methods and their catalytic activity was tested in the reaction of ozone decomposition. Cryptomelane, OMS-2, is the main phase of the synthesized samples, bixbyite, Mn2O3, and pyrolusite, β-MnO2, are impurity phases presented in OMS-2 and M/OMS-2 at a quantity lower than 10 %. The doped metal ions did not create a new phase however they influenced the size of cryptomelane crystallites and it became almost two times lower. Our IR spectral investigations show that, in the region of stretching vibrations of OH groups in the associated water molecules, the IR absorption is very weak for all M/OMS-2 samples as opposed to OMS-2. IR spectroscopic analysis also showed that incorporation of the transition metal ions into the cryptomelane structure differently affected the vibrations of Mn-O and Mn-OH bonds. The doped Cu2+ ion practically caused no change in the OMS-2 spectrum whereas new absorption bands characteristic of Co-O and Fe-O bonds appeared in the spectra of Co/OMS-2 and Fe/OMS-2. The absorption band in 650-400 cm-1 region of the Fe/OMS-2 spectrum is complex. The catalytic activity of M/OMS-2 samples depended on the nature of the current transition metal ion doped into tunnel channels of cryptomelane. The Cu/OMS-2 sample exhibits a tendency to the steady-state mode of ozone decomposition whereas, in the case of the Cu/OMS-2 and Fe/OMS-2, the ozone concentration at the reactor outlet rapidly increases. Comparison of the activity of these three M/OMS-2 samples and OMS-2 resulted in the following order: Co/OMS-2 > OMS-2 > Cu/OMS-2 > Fe/OMS-2. Thus, the accelerating effect was observed only in the case of cobalt (II) ions.

Growth and characterization of L-phenylalanine nitric acid (LPN) and tris L-(phenylalanine)-phenylalanininum nitrate (TPLPN) as second and third order nonlinear optical materials

We synthesized noncentrosymmetric single crystals of L-phenylalanine nitrate (LPN) and tris L-(phenylalanine) L-phenylalaninium nitrate (TPLPN) by slow solvent evaporation technique. Both crystallized in monoclinic system with different acentric space groups namely P21 (LPN) and C2 (TPLPN) respectively. The IR and Raman spectral investigation was done for LPN and TPLPN and discussed. The UV-vis-studies accomplished the excitation wavelength of the grown crystals suitable to exhibit second harmonic generation signal. From the absorption data, remarkable optical properties such as direct band gap energy, Urbach energy, extinction coefficient were evaluated. The mechanical strength of the grown crystal was examined by Vickers micro hardness test. The temperature of decomposition was confirmed by TG/DSC analysis. Fluorescence emission spectrum of LPN and TPLPN were recorded and lifetime was also studied. The dielectric constant and dielectric loss of LPN and TPLPN has been determined as a function of frequency and temperature. Also the surface topologies of the crystallized salts were assessed by SEM studies. The third-order nonlinearities of LPN and TPLPN were determined by Z-scan technique with Nd: YAG at 532 nm and thereby from closed and open Z-scan data, third-order susceptibilities were calculated to be χ(3) = 8.826 × 10−6 esu for LPN and χ(3) = 2.552 × 10−7 esu for TPLPN.

Ma_MISS on ExoMars: Mineralogical Characterization of the Martian Subsurface

The Ma_MISS (Mars Multispectral Imager for Subsurface Studies) experiment is the visible and near infrared (VNIR) miniaturized spectrometer hosted by the drill system of the ExoMars 2020 rover. Ma_MISS will perform IR spectral reflectance investigations in the 0.4–2.2 μm range to characterize the mineralogy of excavated borehole walls at different depths (between 0 and 2 m). The spectral sampling is about 20 nm, whereas the spatial resolution over the target is 120 μm. Making use of the drill's movement, the instrument slit can scan a ring and build up hyperspectral images of a borehole. The main goal of the Ma_MISS instrument is to study the martian subsurface environment. Access to the martian subsurface is crucial to our ability to constrain the nature, timing, and duration of alteration and sedimentation processes on Mars, as well as habitability conditions. Subsurface deposits likely host and preserve H2O ice and hydrated materials that will contribute to our understanding of the H2O geochemical environment (both in the liquid and in the solid state) at the ExoMars 2020 landing site. The Ma_MISS spectral range and sampling capabilities have been carefully selected to allow the study of minerals and ices in situ before the collection of samples. Ma_MISS will be implemented to accomplish the following scientific objectives: (1) determine the composition of subsurface materials, (2) map the distribution of subsurface H2O and volatiles, (3) characterize important optical and physical properties of materials (e.g., grain size), and (4) produce a stratigraphic column that will inform with regard to subsurface geological processes. The Ma_MISS findings will help to refine essential criteria that will aid in our selection of the most interesting subsurface formations from which to collect samples. Key Words: Mars—Subsurface—Spectroscopy—Mineralogy. Astrobiology 17, 612–620.

Nanostructured Polyphase Catalysts Based on the Solid Component of Welding Aerosol for Ozone Decomposition.

Samples of the solid component of welding aerosols (SCWAs) were obtained as a result of steel welding by ANO-4, TsL‑11, and UONI13/55 electrodes of Ukrainian manufacture. The phase compositions of the samples, both freshly prepared (FP) and modified (M) by water treatment at 60 °C, were studied by X-ray phase analysis and IR spectroscopy. All samples contain magnetite demonstrating its reflex at 2θ ~ 35° characteristic of cubic spinel as well as manganochromite and iron oxides. FP SCWA-TsL and FP SCWA-UONI contain such phases as СaF2, water-soluble fluorides, chromates, and carbonates of alkali metals. After modification of the SCWA samples, water-soluble phases in their composition are undetectable. The size of magnetite nanoparticles varies from 15 to 68 nm depending on the chemical composition of electrodes under study. IR spectral investigations confirm the polyphase composition of the SCWAs. As to IR spectra, the biggest differences are apparent in the regions of deformation vibrations of M–O–H bonds and stretching vibrations of M–O bonds (M–Fe, Cr). The catalytic activity of the SCWAs in the reaction of ozone decomposition decreases in the order SCWA-ANO > SCWA-UONI > SCWA-TsL corresponding to the decrease in the content of catalytically active phases in their compositions.

PHYSICO-CHEMICAL PRoPERtIES OF The SOLID CoMPONENT OF WELDING AEROSOL. 2. IR SPECTRAL CHARACTERISTICS

Polyphase composition of SCWA-ANO-4 and SCWA-TsL-11 samples has been confirmed with the help of the IR spectral investigation: absorption bands of iron and chromium oxides and calcite have been detected. The absorption bands whose maxima are at 1748 and 1381 cm-1characterize stretching vibrations of carbonate-carboxylate groups which appearance is due to the oxidation with air oxygen of CO formed on the oxide surface as a result of the electrode burning.

Synthesis and antitubercular screening of some novel 4H-1,4- benzothiazines and their sulfones under environment benign solvent free conditions as future anti-tubercular agents.

Some novel analogs of 4H-1,4-benzothiazines were synthesized under environmentally benign solvent free conditions by one pot oxidative cyclocondensation of substituted 2- aminobenzenthiols with compounds having active methylene group and then converted in to sulfones. These compounds were examined as antitubercular agents against Mycobacterium tuberculosis H37Rv using REMA plate method. The best results have MICs from 6.4 to 8.8 μg/mL, comparable to phenothiazines. IR, NMR and mass spectral investigations are included for structural elucidation.

Influence of sesquioxides on luminescence features of Nd3+ ions in PbO–PbF2–B2O3 glass system

The emission characteristics of Nd3+ ions in PbO–PbF2–B2O3–M2O3 (M=Y, Sc, Al) glasses were studied as a function of M2O3 concentration. The IR spectral investigations have indicated that the network of the glass mixed with Y2O3 is more depolymerized when compared with other two sesquioxides. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were studied as functions of concentration of M2O3. The luminescence spectra of these glasses have exhibited three NIR bands corresponding to the transitions 4F3/2→4I9/2, 4F3/2→4I11/2 (at 1.06μm) and 4F3/2→4I13/2. A clear enhancement in the luminescence emission corresponding to these transitions has been observed with increase in the concentration of M2O3 upto 8.0mol%. The comparison of emissive characteristics of the glasses mixed with three sesquioxides indicated the highest luminescence efficiency for Y2O3 mixed glasses among the three series glasses studied. The increase of luminescence efficiency has been attributed to the possible declusterization of Nd3+ ions by M3+ ions in the glass network. The reasons for low luminescence quenching observed in case of Y2O3 mixed glasses have been explored in terms of the ionic radii of the sesqui-ions and their possible positions in the glass network.

Studies on optimizing sesquioxide contents to enhance luminescence efficiency of Pr3+ ions in PbO−PbF2−B2O3 glass system

Pr3+ doped lead oxy fluoro borate glasses mixed with three sesquioxides (M2O3) viz. Y2O3, Sc2O3, Al2O3 of different concentrations (0–10mol%) have been synthesized. The preliminary understanding over the structural modifications due to the insertion of the sesquioxides in the glass network could be obtained by IR spectral investigations. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were studied as functions of concentration of M2O3. The luminescence spectra of these glasses have exhibited the bands due to 3P0→3F2, 3F3, 3H6, 3H4, 3H5 transitions of Pr3+ ions. From these spectra, the radiative parameters viz., spontaneous emission probability A, the total emission probability AT, the radiative lifetime τ, the fluorescent branching ratio β of different transitions originated from 3P0 level of Pr3+ ions have been evaluated. A considerable enhancement in the luminescence emission corresponding to 3P0→3H6, 3F2 transitions has been observed with increase in the concentraion of M2O3 up to 8.0mol%. The increase has been attributed to the possible declusterization of Pr3+ ions by M3+ ions in the glass network. The comparison of emissive characteristics of the glasses mixed with three sesquioxides indicated the highest luminescence efficiency for Y2O3 mixed glasses among the three series glasses studied and this has been explained in terms of different degrees of variations in the structural modifications in the vicinity of Pr3+ ion in the glass network.

Investigations of the historic textiles excavated from Ancient Ainos (Enez – Turkey) by multiple analytical techniques

Some metal ornamented textile specimens and a textile button, excavated from Ancient Ainos (Enez – Turkey), have been investigated using FTIR and EDXRF spectrometry, for the purpose of material identification. FTIR spectral results indicated that textiles were made from partially degummed Bombyx mori silk. The IR spectral investigation of the textile button revealed that some cellulose fillings were used inside the button. The EDXRF analysis of the metal ornaments showed that they were silver plated copper. Surface morphology of the textiles and the metal ornaments were investigated by SEM images. It was shown that textile fibers were highly degraded.

Induced smectic-B and smectic-G phases in hydrogen-bonded complexes (nOBA:PFOA): thermal and phase behaviour studies

A new series of intermolecular hydrogen-bonded liquid crystals are synthesised. The hydrogen bond formed between the mesogenic p-n-alkoxy benzoic acids (nOBAs) and non-mesogenic perfluorooctanoic acid (PFOA) (where n represents the alkoxy carbon numbers from 4 to 12 and 16). The IR spectral investigation confirms the hydrogen bond. The thermal and phase behaviour of these materials were studied by the use of polarising thermal microscope attached with a hot stage and the differential scanning calorimeter. From the experimental observations, both smectic-B and smectic-G phases are induced in the complexes having the chain number n = 7–12 by quenching smectic-C phase.

The ‘partial resonance’ of the ring in the NLO crystal melaminium formate: Study using vibrational spectra, DFT, HOMO–LUMO and MESP mapping

The molecular geometry and vibrational spectral investigations of melaminium formate, a potential material known for toxicity and NLO activity, has been performed. The FT IR and FT Raman spectral investigations of melaminium formate is performed aided by the computed spectra of melaminium formate, triazine, melamine, melaminium and formate ion, along with bond orders and PED, computed using the density functional method (B3LYP) with 6-31G(d) basis set and XRD data, to reveal intermolecular interactions of amino groups with neighbor formula units in the crystal, intramolecular H⋯H repulsion of amino group hydrogen with protonating hydrogen, consequent loss of resonance in the melaminium ring, restriction of resonance to N3C1N1 moiety leading to special type resonance of the ring and the resonance structure of CO2 group of formate ion. The 3D matrix of hyperpolarizability tensor components has been computed to quantify NLO activity of melamine, melaminium and melaminium formate and the hyperpolarizability enhancement is analyzed using computed plots of HOMO and LUMO orbitals. A new mechanism of proton transfer responsible for NLO activity has been suggested, based on anomalous IR spectral bands in the high wavenumber region. The computed MEP contour maps have been used to analyze the interaction of melaminium and formate ions in the crystal.

Synthesis, growth, spectral and thermal properties of a new organic crystal: 2-Carboxypyridin-1-ium trichloroacetate

A novel organic optical material complex of 2-carboxypyridin-1-ium trichloroacetate has been synthesized and crystals were grown from aqueous solution employing the technique of controlled evaporation. The crystal structure has been determined using single crystal X-ray diffraction studies. The single crystals were successfully grown by the slow evaporation method with dimensions 12×8×3mm3. FT IR spectral investigation has been carried out to identify the various functional groups present in the grown crystal. Molecular structure was confirmed by NMR spectral analysis. Melting point was found using thermal measurements.

Characterization and FTIR spectral studies of human urinary stones from Southern India

Urinary stones resected from urinary bladders of patients hailing from Kollam district of Kerala State, India were analyzed by SEM, XRD and by thermal analysis techniques. The analytical results indicate that, stones have different composition, i.e., calcium phosphate, calcium phosphate hydroxide and sodium calcium carbonate. Infrared spectral studies also reveal the presence of phosphates or carbonates in these samples. Further, IR spectral investigations have revealed that amorphous carbonated species are occupied in PO 4 sites in calcium phosphate type stone and OH sites in calcium phosphate hydroxide sample. Thermal studies of these samples also reveal that, carbon dioxide is released from carbonated samples upon heating which is related to amount of carbon content and bond strength. Crystals with defects and irregular morphology are grown inside the urinary bladder due to variation in crystal growth conditions.

Nature of the Active Sites in Ethylene Oligomerization Catalyzed by Ni-Containing Molecular Sieves: Chemical and IR Spectral Investigation

Thermoactivated Ni-exchanged AlMCM-41 mesoporous materials were found to be very efficient heterogeneous catalysts for ethylene oligomerization. By means of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy of adsorbed CO, it has been established that, during the thermal activation under dry atmosphere, the Ni2+ ions were partially reduced to Ni+ ions. A very good correlation between the activation temperature and the catalytic activity in the ethylene oligomerization was observed. Both Ni+ and dehydrated Ni2+ ions were proposed as catalytic active sites in this process.

Mass, IR, UV and EPR spectral characterization of the complexes of (NPH2)3 with CuII compound

Hexahydrocyclotriphosphazene (HHCTP) was refluxed with Cu II acetate in chlorobenzene when two products, Cu II A and Cu II B were obtained. On the basis of their Mass, IR, UV and EPR spectral investigations, Cu II A and Cu II B complexes have been formulated as (P 9 N 9 H 16 -Cu) and (P 3 N 3 H 2 Cu) 2 respectively.

Synthesis, spectral, and antifungal studies of transition metal complexes with sixteen-membered hexadentate macrocylic ligand

A novel hexadentate nitrogen donor [N6] macrocyclic ligand viz, 1,5,11,15,21,22-hexaaza-2,14-dimethyl-l4,12-diphenyltricyclo[15.3.1.I(7–11)]docosane[1,4,6,8,10(22)-11,14,16,18,20(21)]decaene (L), has been synthesised. The Co (II), Ni (II), and Cu (II) complexes with this ligand have been prepared and subjected to elemental analysis, molar conductance, magnetic susceptibility measurements, mass, 1H NMR (ligand), IR, electronic, and ESR spectral studies and electrochemical investigation. On the basis of molar conductance the complexes can be formulated as [M(L)]X2 (where M = Co (II), Ni (II), Cu (II) and X = Cl− and NO3−) due to their 1: 2 electrolytic nature in DMSO. All the complexes are of the high-spin type and are six-coordinated. On the basis of IR, electronic, and ESR spectral studies, an octahedral geometry has been assigned for the Co(II) and Ni(II) complexes, whereas a tetragonal geometry for the Cu(II) complexes was found. Antimicrobial activity of L and its complexes as growth inhibiting agents have been screened in vitro against two species (F. moniliformae and R. solani) of plant pathogenic fungi.

Iron(III) complexes: Preparation, characterization, antibacterial activity and DNA-binding

Iron(III) have been combined to well known quinolones (ciprofloxacin) and some Schiff bases with the help of coordination approach. Characterization of these compounds have been done using elemental analysis, magnetic measurements, thermogravimetric analysis, IR, UV-VIS, 1H NMR and 13C NMR spectral investigation. Analytical studies suggest that the iron(III)-quinolone complexes assume a six-coordinated dimeric distorted octahedral geometry. All the compounds show a good antibacterial activity against broad range of bacteria like Bacillus cereus, Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Salmonella typhi and Serratia marcescens, whereas no significant inhibition towards growth of fungal strains like Aspergillus Niger, Aspergillus flavus and Lasiodiplodia theobromae. Analyses of all these compounds show effective sperm herring DNA inhibition.

Template Polymerization of Nano-Scale Poly(1-Naphthylamine): Effect of Oxidant on the Spectral, Thermal and Morphological Characteristics

For the first time the template synthesis of nano-scale poly(1-naphthylamine) is reported in CSA micellar medium using benzoyl peroxide, ammonium persulphate and potassium dichromate as oxidants. The nanopolymers were characterized by FT-IR, UV-Vis, DSC, TGA, XRD, DLS, as well as SEM techniques. IR spectral investigations revealed the polymerization of 1-naphthylamine through N–C(5) linkages. The UV studies revealed the differences in the chain conformation of the polymers and their polaronic states. The nanosize of the conducting polymers was analyzed by SEM. DLS analysis showed that the particle size of the polymer prepared using the three oxidants varied between 115 and 117 nm. SEM showed that particle size of the three polymers varied between 100 and 312 nm. XRD, as well as DSC analyses confirmed partial crystallinity of these polymers. Conductivity was found to be in the range of 10–3 to 10–2 S/cm, which could be correlated to the conformation of the polymeric chains and delocalization of polarons. The nanopolymers were found to be thermally stable up to 400°C.

Synthesis and Spectral Investigations of Manganese(II), Cobalt(II), Nickel(II), Copper(II) and Zinc(II) Complexes of New Polydentate Ligands Containing a 1,8-Naphthyridine Moiety

2-(o-Hydroxyphenyl)-1,8-naphthyridine (HN), 2-(4-hydroxy-6-methylpyran-2-one-3-yl)-1,8-naphthyridine (HMPN) and 2-(benzimidazol-2-yl)-1,8-naphthyridine(BN) react with acetates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) to yield metal ion complexes of definite composition. These compounds were characterized by elemental analyses, molar conductivity, magnetic susceptibility measurements, thermal studies, IR, UV-visible, NMR and mass spectral investigations. The complexes are found to have the formulae [M(HN)2(H2O)2], [M(HMPN)2(H2O)2] and [M(BN)2(OAc)2], respectively.

Improved Imide Receptors by Imprinting Using Pyrimidine-Based Fluorescent Reporter Monomers

[reaction: see text] Optically responsive receptors toward imides based on 6-substituted 2,4-bis(acrylamido)pyrimidines are presented. The monomers were readily prepared in good yield. Solution binding to 1-benzyluracil (BU) monitored by 1H NMR appeared lower than a previously reported pyridine-based monomer. However, as indicated by 1H NMR and IR spectral investigations, the association strength was demonstrated to be "masked" by dimerization of the pyrimidine-based monomer units. Thus, from dilution experiments, a dimerization constant of 731 M(-1) was estimated for the pyrimidine-based monomer 2,4-bis(acrylamido)-6-piperidinopyrimidine whereas for the pyridine-based monomer 2,6-bis(acrylamido)pyridine, no self-association was observed. This precluded an accurate determination of the binding constant for BU to the former monomer whereas for the latter a binding constant of 757 M(-1) was measured. Despite the strong self-association, the novel monomer was shown to lead to enhanced imprinting effects when compared to imprinted polymers prepared analogously, but using the pyridine-based monomer as the recognition element. This was attributed to a higher intrinsic binding affinity exhibited by the pyrimidine based host monomer vis a vis the guest and the existence in the former of more than one interaction site for the guest. The monomers exhibited fluorescence emission informative of the mode of monomer incorporation in the polymer and the presence of guest species. Thus, the fluorescence was rapidly and selectively quenched upon template addition, with the degree of quenching correlating with binding affinity and the amount of template bound to the polymer.