Search results for "IR spectroscopy"
showing 10 items of 70 documents
Biogenic Selenium Nanoparticles: A Fine Characterization to Unveil Their Thermodynamic Stability
2021
Among the plethora of available metal(loid) nanomaterials (NMs), those containing selenium are interesting from an applicative perspective, due to their high biocompatibility. Microorganisms capable of coping with toxic Se-oxyanions generate mostly Se nanoparticles (SeNPs), representing an ideal and green alternative over the chemogenic synthesis to obtain thermodynamically stable NMs. However, their structural characterization, in terms of biomolecules and interactions stabilizing the biogenic colloidal solution, is still a black hole that impairs the exploitation of biogenic SeNP full potential. Here, spherical and thermodynamically stable SeNPs were produced by a metal(loid) tolerant Mic…
Thermal aggregation of beta-lactoglobulin in presence of metal ions.
2007
In this work, we report a study of the effects of zinc and copper ions on the heat-induced aggregation of beta-lactoglobulin (BLG). Kinetics investigations on aggregates growth by light scattering measurements and on secondary structure changes by FTIR absorption measurements show the different role played by the two metals during the whole process. In particular, the presence of zinc in solution promotes the formation of aggregates of BLG at a lower temperature than copper. Then, at fixed temperature, formation of a large amount of aggregates, of large dimension, is observed for Zn-BLG in shorter time; on the contrary, the presence of copper in solution does not affect the aggregation proc…
OH-related Infrared Absorption Bands in Oxide Glasses
2005
We report the infrared activity, in the spectral region of the OH stretching modes, of different composite silicate glasses whose chemical composition is established by X-ray fluorescence measurements. The analysis of the absorption line profiles is made in terms of different spectral contributions, Gaussian in shape. The comparison with analogous spectra obtained in vitreous silica samples with impurity concentrations < 100 part per million moles is evidence of the effects of the different oxides on the vibrational properties of the OH groups. In particular, for oxide glasses a red shift of the composite band at about 3670 cm(-1), assigned to the OH stretching modes of free Si-OH groups an…
On-line measurements of RuO$_4$ during a PWR severe accident
2015
International audience; After the Fukushima accident, it became essential to have a way to monitor in real time the evolution of a nuclear reactor during a severe accident, in order to react efficiently and minimize the industrial, ecological and health consequences of the accident. Among gaseous fission products, the tetroxide of ruthenium RuO$_4$ is of prime importance since it has a significant radiological impact. Ruthenium is a low volatile fission product but in case of the rupture of the lower head by the molten corium, the air entering into the vessel oxidizes Ru into gaseous RuO$_4$, which is not trapped by the Filtered Containment Venting Systems. To monitor the presence of RuO$_4…
Microchemical surface analysis of historic copper-based coins by the combined use of FIB-FESEM-EDX, OM, FTIR spectroscopy and solid-state electrochem…
2019
[EN] A multi-technique strategy, including microscopy, spectroscopic and electrochemical techniques, is proposed to study thin corrosion layers that form on the surface of historic copper-based coins. An accurate characterisation of this external corrosion layer is important for selecting a suitable conservation and/or restoration treatment. For this purpose, a series of copper-based coins from different historical periods and provenances, which mainly exhibited atmospheric corrosion, was analysed. The morphology of the corrosion layer and the upper core of coins was studied in trenches done on coin surfaces with a focused ion beam gun, coupled to a field emission scanning electron microsco…
Effect of Hydration Procedure of Fumed Silica Precursor on the Formation of Luminescent Carbon Centers in SiO 2 :C Nanocomposites
2019
The effect of hydration procedure of fumed silica precursor on photoluminescent properties of carbonized silica (SiO2:C) nanocomposite after chemo/thermal treatments is studied. Main structural effect is the formation of chemical bonding of phenyl groups to silica surface via multiple CSiO bonding bridges. Synthesized samples demonstrate very broad photoluminescence (PL) bands in near ultraviolet and visible ranges with maximum intensity dependent on temperature of thermal annealing. Two main trends in luminescence properties are: 1) hydration-induced blue shift of PL in comparison with PL of unhydrated series; 2) red shift of PL bands with increasing synthesis temperature regardless hydr…
Role of Solvent on Protein-Matrix Coupling in MbCO Embedded in Water-Saccharide Systems: an FTIR study.
2006
Embedding protein in sugar systems of low water content enables one to investigate the protein dynamicstructure function in matrixes whose rigidity is modulated by varying the content of residual water. Accordingly, studying the dynamics and structure thermal evolution of a protein in sugar systems of different hydration constitutes a tool for disentangling solvent rigidity from temperature effects. Furthermore, studies performed using different sugars may give information on how the detailed composition of the surrounding solvent affects the internal protein dynamics and structural evolution. In this work, we compare Fourier transform infrared spectroscopy measurements (300–20 K) on MbCO e…
Characterization of the nucleation process of lysozyme at physiological pH: Primary but not sole process
2013
We report on a kinetic study of the heat-induced aggregation process of lysozyme at physiological pH. The time evolution of the aggregation extent and the conformational changes of the protein were followed by dynamic light scattering (DLS) and FTIR spectroscopy, respectively, whereas the morphology of the aggregates was observed by Atomic Force Microscopy (AFM). The conformational changes of the secondary and tertiary structures were simultaneous and distinct in time with respect to the formation of aggregates. Oligomer formation occurred through at least two different aggregation processes: a nucleation process and a homogeneous non-nucleative diffusion-controlled process. FTIR measuremen…
Comparative study of historical woods from XIX century by thermogravimetry coupled with FTIR spectroscopy
2019
Thermal and structural properties of historical woods from apparatuses of the Historical Collection of the Physics Instruments of the University of Palermo have been investigated by FTIR spectroscopy coupled with thermogravimetric analysis. Specifically, the wooden portions of apparatuses from XIX century have been studied. The investigated woods belong to different taxa (Swietenia mahagoni, Picea abies and Juglans regia). The thermal behavior of the wooden materials has been successfully interpreted on the basis of specific indexes determined by the quantitative analysis of the FTIR spectra. The kinetics of the wood pyrolysis have been investigated by using a non-isothermal approach based …
Protein dynamics observed by tunable mid-IR quantum cascade lasers across the time range from 10 ns to 1 s
2017
We have developed a spectrometer based on tunable quantum cascade lasers (QCLs) for recording time-resolved absorption spectra of proteins in the mid-infrared range. We illustrate its performance by recording time-resolved difference spectra of bacteriorhodopsin in the carboxylic range (1800–1700 cm− 1) and on the CO rebinding reaction of myoglobin (1960–1840 cm− 1), at a spectral resolution of 1 cm− 1. The spectrometric setup covers the time range from 4 ns to nearly a second with a response time of 10–15 ns. Absorption changes as low as 1 × 10− 4 are detected in single-shot experiments at t > 1 μs, and of 5 × 10− 6 in kinetics obtained after averaging 100 shots. While previous time-res…