High Resolution FTIR Research Articles

Time-dependent gel to gel transformation of a peptide based supramolecular gelator.

A dipeptide with a long fatty acid chain at its N-terminus gives hydrogels in phosphate buffer in the pH range 7.0-8.5. The hydrogel with a gelator concentration of 0.45% (w/v) at pH 7.46 (physiological pH) provides a very good platform to study dynamic changes within a supramolecular framework as it exhibits remarkable change in its appearance with time. Interestingly, the first formed transparent hydrogel gradually transforms into a turbid gel within 2 days. These two forms of the hydrogel have been thoroughly investigated by using small angle X-ray scattering (SAXS), powder X-ray diffraction (PXRD), field emission scanning electron microscopic (FE-SEM) and high-resolution transmission electron microscopic (HR-TEM) imaging, FT-IR and rheometric analyses. The SAXS and low angle PXRD studies substantiate different packing arrangements for the gelator molecules for these two different gel states (the freshly prepared and the aged hydrogel). Moreover, rheological studies of these two gels reveal that the aged gel is stiffer than the freshly prepared gel.

High-energy chemistry of formamide: A unified mechanism of nucleobase formation

The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life about 4 billion years ago suggest that extraterrestrial impacts could contribute to the synthesis of the building blocks of the first life-giving molecules. We simulated the high-energy synthesis of nucleobases from formamide during the impact of an extraterrestrial body. A high-power laser has been used to induce the dielectric breakdown of the plasma produced by the impact. The results demonstrate that the initial dissociation of the formamide molecule could produce a large amount of highly reactive CN and NH radicals, which could further react with formamide to produce adenine, guanine, cytosine, and uracil. Based on GC-MS, high-resolution FTIR spectroscopic results, as well as theoretical calculations, we present a comprehensive mechanistic model, which accounts for all steps taking place in the studied impact chemistry. Our findings thus demonstrate that extraterrestrial impacts, which were one order of magnitude more abundant during the LHB period than before and after, could not only destroy the existing ancient life forms, but could also contribute to the creation of biogenic molecules.

A facile synthesis of a novel three‐phase nanocomposite: Single‐wall carbon nanotube/silver nanohybrid fibers embedded in sulfonated polyaniline

ABSTRACTA three‐phase water‐soluble nanocomposite of single wall carbon nanotube/silver nanoparticle hybrid fibers embedded in sulfonated polyaniline has been synthesized by a simple chemical solution mixing process. The nanocomposite has been characterized by high resolution electron microscopy, X‐ray diffractometry, FTIR spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Optical and electrical characteristics of the nanocomposite have been determined by UV–vis absorption spectroscopy, photoluminescence spectroscopy, and four‐probe electrical conductivity measurement. A surface plasmon absorption band obtained around 460 nm indicates the presence of silver nanoparticles in the composite. The optical band gap calculation for sulfonated polyaniline vis‐a‐vis the nanocomposite supported the conductivity measurement. Over 1300 times increase in DC electrical conductivity has been observed for the three‐phase nanocomposite, with a filler loading of 20 wt %, at 306 K. This observation could be explained by Mott's variable range hopping model considering a three‐dimensional conduction. Such a nanocomposite has immense potential for use as a cathode material in lithium‐ion batteries and supercapacitors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41692.

Structure of framework aluminum Lewis sites and perturbed aluminum atoms in zeolites as determined by 27Al{1H} REDOR (3Q) MAS NMR spectroscopy and DFT/molecular mechanics.

Zeolites are highly important heterogeneous catalysts. Besides Brønsted SiOHAl acid sites, also framework AlFR Lewis acid sites are often found in their H-forms. The formation of AlFR Lewis sites in zeolites is a key issue regarding their selectivity in acid-catalyzed reactions. The local structures of AlFR Lewis sites in dehydrated zeolites and their precursors--"perturbed" AlFR atoms in hydrated zeolites--were studied by high-resolution MAS NMR and FTIR spectroscopy and DFT/MM calculations. Perturbed framework Al atoms correspond to (SiO)3AlOH groups and are characterized by a broad (27)Al NMR resonance (δi = 59-62 ppm, CQ = 5 MHz, and η = 0.3-0.4) with a shoulder at 40 ppm in the (27)Al MAS NMR spectrum. Dehydroxylation of (SiO)3AlOH occurs at mild temperatures and leads to the formation of AlFR Lewis sites tricoordinated to the zeolite framework. Al atoms of these (SiO)3Al Lewis sites exhibit an extremely broad (27)Al NMR resonance (δi ≈ 67 ppm, CQ ≈ 20 MHz, and η ≈ 0.1).

Morphology and conductivity tuning of polyaniline using short-chain alcohols by heterophase polymerization

Conducting polyaniline (PANI) nanostructures were obtained by heterophase polymerization of aniline monomer using sodium dodecyl sulfate (SDS) as surfactant in presence of the short-chain alcohols: ethanol, propanol, butanol, pentanol, and hexanol as co-surfactants, and ammonium persulfate (APS) as oxidizing agent. The resulting polymers were analyzed by Field Emission, high resolution scanning electron microscopy (FE-HRSEM), UV/Vis, FTIR, cyclic voltammetry, and X-ray diffraction (XRD). It was observed from FE-HRSEM analysis that fiber-like particles were obtained when polymerizing without alcohol and in presence of ethanol, while very big agglomerates were obtained in presence of propanol and butanol; using pentanol as co-surfactant well-defined and spherical nanoparticles were obtained, the presence of hexanol through polymerization gives both spherical agglomerated and needle-like nanostructures. Final conversions were between 50 and 73 %, in the following order: hexanol = pentanol > butanol > thanol > propanol > without alcohol. Conductivities were in the range of 0.81 to 1.1 S/m with the higher value for that synthesized in presence of pentanol. Difference in conductivity of PANI was ascribed to formation of organic acids as a consequence of reaction between alcohols and APS, thus doping in situ PANI.

Spontaneous and Photoinduced Conversion of CO2 on TiO2 Anatase (001)/(101) Surfaces

High-resolution FT-IR spectroscopy was used to study the kinetics of oxygen mobility between gaseous isotopically labeled C18O2 and solid phase Ti16O2 nanocrystalline anatase (001). Analysis of the isotopic composition of the gases produced has revealed that anatase (001) calcinated at temperatures under 500 °C is a very weakly reactive material and exhibits a low exchange mobility of oxygen atoms between the gas phase molecules of CO2 and the TiO2 lattice. Isotope exchange is blocked by both residual HF adsorbed onto the TiO2 surface and TiOF2 impurities. The presence of TiOF2 was shown by TEM and X-ray diffraction. However, the anatase (001) sample became slightly active after annealing at temperatures higher than 500 °C and upon UV illumination. Nevertheless, the effective rate constant is still 3.45 times lower than that observed for the spontaneous exchange between C18O2 and anatase (101) material calcinated at 500 °C.

Infrared absorption cross sections for 1,1,1,2-tetrafluoroethane

High-resolution infrared absorption cross sections for 1,1,1,2-tetrafluoroethane have been determined over the spectral range 750–1600cm−1 from spectra recorded using a high-resolution FTIR spectrometer (Bruker IFS 125HR) and a 26-cm-pathlength cell. Spectra of 1,1,1,2-tetrafluoroethane/dry synthetic air mixtures were recorded at 0.015cm−1 resolution (calculated as 0.9/MOPD) at a number of temperatures and pressures (22–761Torr and 191–296K) appropriate for atmospheric conditions. Intensities were calibrated using composite 1,1,1,2-tetrafluoroethane spectra taken from the Pacific Northwest National Laboratory (PNNL) IR database. This cross section dataset is intended to replace what is currently available in the HITRAN/GEISA databases.

Synthesis, immobilization and catalytic activity of a copper(II) complex with a chiral bis(oxazoline).

A chiral bis(oxazoline) bearing CH2OH groups was synthesized from a commercial bis(oxazoline) and characterized by 1H- and 13C-NMR, high resolution ESI-mass spectrometry and FTIR. The corresponding copper(II) complex was immobilized onto the surface of a mesoporous carbonaceous material (Starbon® 700) in which the double bonds had been activated via conventional bromination. The materials were characterized by elemental analysis, ICP-OES, XPS, thermogravimetry and nitrogen adsorption at 77 K. The new copper(II) bis(oxazoline) was tested both in the homogeneous phase and once immobilized onto a carbonaceous support for the kinetic resolution of hydrobenzoin. Both were active, enantioselective and selective in the mono-benzoylation of hydrobenzoin, but better enantioselectivities were obtained in the homogeneous phase. The heterogeneous catalyst could be separated from the reaction media at the end of the reaction and reused in another catalytic cycle, but with loss of product yield and enantioselectivity.

An Investigation into the Oxygen Evolution Reaction at Manganese/ Manganese Ruthenium and Ruthenium Oxide Films in Base

Alkaline water electrolysis has been proposed as an environmentally inoffensive route to the production of the large volumes of hydrogen gas required by a possible hydrogen economy [1-5]. In practice, the efficiency of water electrolysis is limited by the large anodic over-potential of the oxygen evolution reaction (OER) [5]. Over the past thirty years, considerable research effort has been devoted to the design, synthesis and characterization of OER anode materials, with the aim of achieving useful rates of active oxygen evolution at the lowest possible over-potential, in order to optimize the overall electrolysis process. Currently, the optimal OER anode materials are Ruthenium and Iridium oxides, since these oxides exhibit the lowest overpotentials for the OER at practical current densities [6]. However, the high cost of these materials compared to other metals and their poor long term stability in alkaline solution renders their widespread commercial utilisation uneconomical [7]. For these reasons, the oxides of the first row transition metals (e.g. manganese, iron, cobalt and nickel) offer a compromise solution. Even though they are not as electrocatalytically active, their relatively low cost and long term corrosion resistance in alkaline solution makes them attractive OER anode materials [7-11].In the present work, we focus on the redox properties and electrocatalytic behaviour with respect to anodic oxygen evolution of manganese and ruthenium oxide electrodes prepared at different molar ratios in aqueous alkaline solution. These films can be prepared simply via thermal decomposition of a metal salt [12]. The structure and morphology of the thermally decomposed oxide materials are examined using thin film XRD, high resolution SEM and FTIR. The redox behavior of the resulting oxide films is investigated as a function of molar ratio and annealing temperature using cyclic voltammetry. The kinetics of the OER at these films has been studied using a range of electrochemical techniques including steady-state polarization and open circuit potential decay curves. In particular, Tafel slopes and reaction orders with respect to hydroxide ion activity are determined. Interestingly, the electrochemical performance for the films is strongly dependent on the molar ratio used, as evident from figure attached. Based on the available kinetic data, a reaction mechanism utilizing the active surfaquo group concept, is proposed. Turnover Frequency numbers are also obtained. Acknowledgements This publication has emanated in part from research conducted with the financial support of Science Foundation Ireland (SFI) under Grant Number SFI/10/IN.1/I2969.

Isolation and characterization of a novel acid degradation impurity of Amlodipine Besylate using Q-TOF, NMR, IR and single crystal X-ray

Forced degradation of Amlodipine Besylate (AMD) in acidic condition gave rise to a potential unknown impurity. This unknown acid degradation product (ADP) was evaluated using a new-reverse-phase high performance liquid chromatography (HPLC), where it was eluted at 1.24 relative retention time to AMD peak. ADP was isolated using preparative HPLC from degradation mixture. Later, structure of ADP was elucidated using high resolution MS, multidimensional NMR and FTIR spectroscopic techniques, and characterized as ethyl-6-(2-chlorophenyl)-8-methyl-3,4,6,7-tetrahydro-2H-benzo[b][1,4]oxazine-5-carboxylate. The presence of ADP recemic mixture was confirmed by polarimeter and chiral HPLC. Given the complexity associated with ADP generation, single crystal X-ray crystallography technique was used to confirm proposed structure. In addition, reaction mechanism was postulated and confirmed using computational chemistry. To our knowledge, it is a novel impurity and not reported elsewhere.

Photo-Induced Functionalization of Spherical and Planar Surfaces via Caged Thioaldehyde End-Functional Polymers

The synthesis and application of a novel reversible addition-fragmentation chain transfer (RAFT) agent carrying a photocaged thioaldehyde moiety is described (λmax = 355 nm). RAFT polymerization of styrene, dimethylacrylamide and a glycomonomer is evidenced (3600 g mol−1 ≤ Mn ≤ 15 000 g mol−1; 1.07 ≤ Đ ≤ 1.20) with excellent end-group fidelity. The photogenerated thioaldehyde on the chain ends can undergo hetero Diels–Alder reactions with dienes as well as reactions with nucleophiles. The terminal photoreactive polymers are photografted to porous diene-reactive polymeric microspheres. The grafted particles are in-depth characterized via scanning electron microscopy, elemental analysis, X-ray photoelectron spectroscopy, and high resolution FT-IR microscopy, leading to a qualitative as well as quantitative image of the core–shell objects. Grafting densities up to 0.10 molecules nm−2 are reached. The versatility of the thioaldehyde ligation is evidenced by spatially resolved grafting of polystyrene onto nucleophilic groups present in poly (dopamine) (PDA)-coated glass slides and silicon wafers via two-photon direct laser writing (DLW) imaged by ToF-SIMS. The combination of thioaldehyde ligation, RAFT polymerization, and DLW allows for the spatially resolved grafting of a vast range of polymers onto various substrates in any desired pattern with sub-micrometer resolution.

Facile and new synthesis of cobalt doped mesoporous TiO2 with high visible-light performance

Cobalt doped and undoped mesoporous titania were synthesized using resin acid as template. Moreover, without adding extra cobalt source, cobalt doped mesoporous titania was also synthesized by using cobalt resinate as both template and cobalt source. These mesoporous samples were characterized by a combination of various physicochemical techniques, such as N2 adsorption/adsorption isotherm, UV–vis diffuse reflectance, X-ray diffraction, high resolution transmission electron microscopy, XPS, and FT-IR. They were used for the photodegradation of methyl blue and Rhdamine B under visible light. It was found that P25 and mesoporous TiO2 synthesized using resin acid as template did not exhibit any meaningful activity for the photodegradation of two dyes under visible light. By contrast, cobalt doped mesoporous titania synthesized by using resin acid as template exhibited more significant photocatalytic yield (94%) for Rhdamine B. Moreover, cobalt doped mesoporous titania synthesized by using cobalt resinate as template also exhibited similar high photocatalytic activity for methyl blue to the former.

The ν4, ν9, ν10 and ν6 + ν11 bands of 12CH313CH3 between 1345 and 1557 cm−1

The infrared spectrum of 12CH313CH3 is measured between 1345 and 1560cm−1 using high resolution FT-IR with a 13C-enriched gas sample cooled to 130.3K. The three fundamentals ν4, ν9 and ν10 (at 1374, 1470 and 1468cm−1 respectively) and one combination band ν6+ν11 at 1473cm−1 are analyzed for the first time. The transitions of ν10 (an infrared inactive “g” mode of the ethane) are observed through its resonant coupling with ν9 (corresponding to a “u” mode of normal ethane). Transitions of ν6+ν11 are seen due to its strong coupling to ν9. In general, torsional splitting produces two components (as in normal ethane), but in both ν9 and ν10, there is an additional small splitting of these components with degenerate torsional symmetry wherever the interacting ν10 levels become infrared active (from “g↔u” mixing); this mechanism is investigated. Several ℓ-type resonances with Δℓ=±2 and Δk=∓1 are observed within ν9 and between ν9 and ν10 while the strong interaction between ν9 and ν6+ν11 plays a role in tuning pairs of levels into resonance. As in normal ethane, a detectable K-doubling occurs in the levels k=±2, ℓ=∓1 of ν9, and the parallel band ν4 shows an intensity bias, with the R-transitions markedly stronger than the P-transitions, due to its x,y-Coriolis coupling with ν9. The spectrum is analyzed by adopting an appropriate Hamiltonian model, and vibration–rotation–torsion parameters of the four mentioned vibrational states are determined by the least squares process using 1350 observed transition line positions (RMS deviation 3.24×10−3cm−1). The values of rotational and torsional parameters of the vibrational ground state are also improved or determined anew, from data of the present spectrum. Two supplemental files are provided. One shows the fit of line positions, and the other gives the measured positions and intensities at 130K (with known quantum assignments and lower state energies) so that lines of this molecule can be identified in planetary spectra.

Basella alba rubra spinach pigment-sensitized TiO2 thin film-based solar cells

Nanocrystalline TiO2 thin films have been prepared by sol–gel dip coating method. The X-ray diffraction results showed that TiO2 thin films annealed at 400, 450 and 500 °C are of anatase phase and the peak corresponding to the (101) plane is present in all the samples. The grain size of TiO2 thin films was found to increase with increasing annealing temperature. The grain size is found to be 20, 25 and 33 nm for the films annealed at 400, 450 and 500 °C. The structure of the TiO2 nanocrystalline thin films have been examined by high-resolution transmission electron microscope, Raman spectroscopy and FTIR spectroscopy. TiO2 thin films were sensitized by natural dyes extracted from basella alba rubra spinach. It was found that the absorption peak of basella alba rubra extract is at about 665 nm. The dye-sensitized TiO2-based solar cell sensitized using basella alba rubra exhibited a Jsc of 4.35 mA cm−2, Voc of 0.48 V, FF of 0.35 and efficiency of 0.70 %. Natural dyes as sensitizers for dye-sensitized solar cells are promising because of their environmental friendliness, low-cost production and fully biodegradable.

Single-step preparation of fluorescent carbon nanoparticles, and their application as a fluorometric probe for quercetin

We report on a method for the determination of quercetin based on the quenching of the fluorescence of carbon nanoparticles (CNPs). The CNPs were prepared by carefully adding an aqueous solution of glucose to solid diphosphorus pentoxide. This single-step method proceeds rapidly and gives large quantities of CNPs. Neither high temperatures nor complicated synthesis steps are needed. The resulting CNPs have an average size of 120 nm and were characterized by high-resolution TEM, FT-IR, elemental analysis and spectrofluorometry. The fluorescence of the CNPs decreases with increasing concentrations of the flavonoid quercetin, with a linear response to quercetin in the 3.3 to 41.2 μM concentration range in pH 6.0 water solution and also in a solution containing 16 % (v/v) of fetal bovine serum. The detection limit is as low as 0.175 μM, and the Stern-Volmer quenching constant is 4.34 × 104 M−1.

Synthesis and Structural Analysis of Novel Neuroprotective Pentacyclo[5.4.1.02,6.03,10.05,9]undecane- and Adamantane-Derived Propargylamines

In this article we present a detailed structural investigation of novel polycyclic pentacyclo[5.4.1.02,6.03,10.05,9]undecane and adamantane propargylamine hybrid molecules. The structural characterization of these compounds was performed using MS, FT-IR and NMR spectroscopy in combination with X-ray diffraction analysis. The single crystal X-ray analyses of four synthons (6, 8–10) are presented; 8-(N)-propargylamino-8,11-oxapentacyclo-[5.4.1.02,6.03,10.05.9]undecane (compound 6 crystallized in the monoclinic system, unit cell parameters: a = 20.737(2) A; b = 8.127(1) A; c = 12.606 (1) A; β = 92.360(2)°; V = 2122.8(3) A3; Z = 8); 11-hydroxy-(N)-propargyl-8,11-azapentacyclo[5.4.1.02,6.03,10.05.9]undecane (compound 8 crystallized in the monoclinic system, unit cell parameters: a = 7.9624(6) A; b = 14.9332(6) A; c = 9.6162(7) A; β = 109.029(3); V = 1080.9(2) A3; Z = 4); 1-methyl-11-hydroxy-(N)-propargyl-8,11-azapentacyclo[5.4.1.02,6.03,10.05.9]undecane (compound 9 crystallized in the monoclinic system, unit cell parameters: a = 7.732(1) A; b = 15.148(2) A; c = 9.864(1) A; β = 101.728(3)°; V = 1131.3 (2) A3; Z = 4); and an adamantane derivative, N,N-dipropargyl-adamantan-1-amine (compound 10 crystallized in the orthorhombic system, unit cell parameters: a = 34.098(4) A; b = 6.825(1) A; c = 10.979(1) A; V = 2555.0(5) A3; Z = 8). From the X-ray analyses it is clear that the polycyclic structures had different modes of intermolecular interaction and molecular stacking. Compound 9 exhibited a cis configuration between the OH and CH3 moieties as expected in view of potential steric hindrance and the electron density effects of the methyl moiety on the initial amination reaction. These hybrid molecules exhibited significant anti-apoptotic activity and could thus find application as neuroprotective agents. A series of pentacyclo[5.4.1.02,6.03,10.05,9]undecane- and adamantane-propargylamines were synthesized and characterized by high-resolution MS, FT-IR, 1H-NMR and 13C-NMR spectroscopy and single-crystal X-ray diffraction. These compounds showed promising neuroprotective ability.

High-resolution FTIR spectroscopy of the ν3 band of methyl acetylene-d

The high-resolution Fourier transform spectrum of methyl acetylene-d1 (CH3CCD) at room temperature has been recorded in the region of the ν3 band (1980–2035cm−1) at an apodized resolution of 0.004cm−1. About 600 vibration–rotation transitions have been assigned, with J upto 36 and K upto 6. The spectrum shows the presence of several perturbations. The observed minus calculated deviation of the fit for K=4 subband is much more than the expected, shows the presence of Fermi resonance with the nearby vibrational state.

Synthesis and Optical Characterization of Sulfonated Polyaniline/Single-Walled Carbon Nanotube/Zinc Sulphide Nanocomposite

Polyaniline functionalized with sulfonate groups (SPANI) shows excellent solubility in water. Single-walled carbon nanotubes functionalized with carboxylic groups (f-SWCNTs) and then hybridized with freshly prepared zinc sulphide (ZnS) nanocrystals have been found to be good luminescent material with tuned emission properties. Nanocomposite of sulfonated polyaniline with embedded SWCNT/ZnS nanohybrid fibers has been prepared by a simple solution mixing process and characterized by using high resolution transmission electron microscopy (HRTEM), X-ray diffractometry, Raman spectroscopy, FTIR spectroscopy, and thermogravimetric analysis (TGA). The study of optical properties by UV-vis absorption and photoluminescence spectroscopy reveals that the composite is a luminescent material of enhanced emission intensity in the visible region of the spectrum.

Comprehensive structural studies of ultra-fine nanocrystalline calcium hydroxyapatite using MAS NMR and FT-IR spectroscopic methods

Three nanoapatites produced using a microwave solvothermal synthesis (MSS), including one with a mean crystal size of only 6nm, were characterized by high-resolution solid-state NMR (1H and 31P) and FT-IR spectroscopies. It was found that nanoapatite particles had an inner crystal core covered by a non-apatitic surface hydrated layer with an outermost liquid-like zone. Various physicochemical properties of those apatite compartments were determined. Important structural details, such as deficiency and disorder of structural OH− ions were discovered and discussed. The materials were also compared with respect to the reaction time and thermal post-synthesis treatment in order to optimize their preparation conditions to the required performance. The study emphasizes the influence of the surface hydrated layer on the physicochemical properties and biological activity of nanoapatites.

Line Intensity Measurements of the ν7+ν8 Band of Ethylene (12C2H4)

From the four high-resolution FTIR absorbance spectra recorded at a spectral resolution of 0.0063 cm−1, 123 line intensities belonging to the ν7+ν8 band of 12C2H4 were measured and fit. The upper v7+v8=1 state rovibrational constants up to sextic terms determined using a Watson's A-reduced Hamiltonian model in Ir representation were used to calculate the line intensities of the band. Results of the experimental fit of the line intensities agree well with those obtained by calculations.