Search results for " infrared"
showing 10 items of 945 documents
Organometallic complexes with biological molecules. XVIII. Alkyltin(IV) cephalexinate complexes: synthesis, solid state and solution phase investigat…
2004
Abstract Dialkyltin(IV) and trialkyltin(IV) complexes of the deacetoxycephalo-sporin-antibiotic cephalexin [7-( d -2-amino-2-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid] (Hceph) have been synthesized and investigated both in solid and solution phase. Analytical and thermogravimetric data supported the general formula Alk 2 SnOHceph · H 2 O and Alk 3 Snceph · H 2 O (Alk=Me, n -Bu), while structural information has been gained by FT-IR, 119 Sn Mossbauer and 1 H, 13 C, 119 Sn NMR data. In particular, IR results suggested polymeric structures both for Alk 2 SnOHceph · H 2 O and Alk 3 Snceph · H 2 O. Moreover, cephalexin appears to behave as monoanionic tridentate ligand coordinating th…
Xyloglucan-based hydrogel films for wound dressing: Structure-property relationships
2017
Thin xyloglucan-based hydrogel films have been synthetized and characterized in the prospect of producing wound dressings. Polyvinyl alcohol (PVA) and glycerol (Gro) were added to have an optimal combination of softness, conformability and resilience. Physical hydrogels have been transformed into permanent covalent hydrogels by reaction with glutaraldehyde (GA). Network structure-process-property relationships are discussed on the account of the results of several complementary characterizations: FTIR, rheology, thermal analysis, morphological analysis, moisture retention and swelling measurements. Selected formulations were also subjected to preliminary in vitro cytotoxicity tests. The phy…
Sintering process of amorphous SiO2 nanoparticles investigated by AFM, IR and Raman techniques
2011
We report an experimental investigation on the effects of thermal treatments at different temperatures (room-1270 K) and for different duration (0-75 h) on amorphous silica nanoparticles (fumed silica) in powder tablet form. Three types of fumed silica are considered, comprising nearly spherical particles of 40 nm, 14 nm and 7 nm mean diameter. The experimental techniques used here are Raman and infrared absorption (IR) spectroscopy together with atomic force microscopy (AFM). Raman and IR spectra indicate that the structure of nanometer silica particles is significantly different with respect to that of a bulk silica glass. In particular, the main differences regard the positions of the IR…
Dynamical properties of myoglobin in an ultraviscous water-glycerol solvent investigated with elastic neutron scattering and FTIR spectroscopy
2018
Abstract Proteins have distinctive dynamical properties, characterized by the fluctuations of protein molecules among the different minima of their energy landscape. These fluctuations, progressively activated for temperature values larger than ~180 K, lead to a steep increase in the temperature dependence of all measurable dynamical properties. This phenomenon is known as Protein Dynamical Transition and, in spite of the intense studies due to its importance in protein function and to the relation with the fascinating fundamental thermodynamics of complex systems, many aspects of it are not yet clearly understood. Among these, the relationship with the properties of the external solvent an…
Temporal control of xyloglucan self-assembly into layered structures by radiation-induced degradation
2016
Partially degalactosylated xyloglucan from tamarind seeds (Deg-XG) is a very appealing biopolymer for the production of in situ gelling systems at physiological temperature. In this work, we observe that the morphology of hydrogels evolves towards high degrees of structural organization with time, yielding to dense stacks of thin membranes within 24 h of incubation at 37 °C. We also explore the possibility offered by gamma irradiation of controlling the time scale of this phenomenon, the final morphology and mechanical properties of the system. Structural and molecular modifications of Deg-XG with dose are investigated by FTIR, dynamic light scattering (DLS) and rotational viscosimetry. The…
Hysteresis in the temperature dependence of the IR bending vibration of deeply cooled confined water.
2019
Using Fourier Transform Infrared (FTIR) spectroscopy, we investigate the temperature dependence of the bending vibrations of water confined in the pores of a silica hydrogel in the temperature interval of 270-180 K. We also investigate the presence of thermal hysteresis by cooling and reheating temperature scans. The results clearly show the presence, at about 230 K, of a crossover in the temperature dependence of the IR spectra; moreover, the presence of hysteresis is clearly demonstrated. By comparing FTIR data with neutron diffraction data and previous calorimetric data on the same samples, we conclude that the crossover and the hysteretical behavior do not involve a water glass transiti…
Self and N-2 collisional broadening of far-infrared methane lines measured at the SOLEIL synchrotron
2012
International audience; Following our recent study devoted to measurements of intensities of pure rotation lines of methane, room temperature far infrared spectra of methane diluted in nitrogen at five total pressures between 100 and 800 hPa have been recorded at the AILES beamline of the SOLEIL synchrotron. One hundred and five N-2 broadening coefficients of methane pure rotation lines have been measured in the 83-261 cm(-1) spectral range using multi-spectrum non-linear least squares fitting of Voigt profiles. Pressure-induced line shifts were not needed to fit the spectra to the noise level and line mixing effects were neglected. One hundred and seventy-six self broadening coefficients h…
Effect of silane coupling treatment on the adhesion between polyamide and epoxy based composites reinforced with carbon fibers
2020
The increasing efforts aimed to design structures with reduced weight and better mechanical performances has led in recent years to a growing use of fiber reinforced polymer materials in several fields such as marine. However, these materials can be composed of chemically very different elements and, hence, may be difficult to joint. This research aims to improve the adhesion between a thermoplastic matrix of polyamide reinforced with short carbon fibers (PA12-CR) and a carbon fiber reinforced epoxy matrix (CFRP). Two different silane coupling agents, (3-Aminopropyl)trimethoxysilane (AM) and (3-Glycidyloxypropyl)trimethoxysilane (EP), were applied, through the spray deposition method, on th…
Determination of in vivo skin moisture level by near-infrared reflectance spectroscopy
2015
Near-infrared spectroscopy has a potential for noninvasive determination of skin moisture level due to high water absorption. In this study, diffuse reflectance spectra of in vivo skin were acquired in the spectral range of 900 nm to 1700 nm by using near-infrared spectrometer, optical fiber and halogen bulb light source. Absorption changes after applying skin moisturizers were analyzed over time at different body sites. Results show difference in absorption when comparing dry and normal skin. Comparison of absorption changes over time after applying moisturizer at different body sites is analyzed and discussed. Some patterns of how skin reacts to different skin moisturizers are shown, alth…
Luminescence and FTIR Spectroscopy of ZnO Nanocrystals
2006
Time-resolved luminescence and Furje Transformation Infrared (FTIR) absorption spectroscopy for ZnO nanocrystals prepared under different chemical reactions using microwave driven hydrothermal process was studied. OH- group stretching vibration frequency is considerably different in nanocrystals studied and in single ZnO crystal. It is shown that fractions of chemicals used in synthesis process could be found in nanopowders. Luminescence at ~2.0 eV (due to defect states in ZnO crystals and nanopowders) was suppressed in nanopowders obtained by urea method.