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Badescu V.,Romanian National Institute for Research and Development in Chemistry and Petrochemistry
Revue Roumaine de Chimie | Year: 2015

(Graph Presented) The aim of this article in continuation of Part I is the study of the fragmentation reactions of tetraethoxysilane (TEOS) as a precursor in the sol-gel process initiated by electronic impact in the ionization chamber of a double focusing mass spectrometer. In Part I the primary fragmentation ions at masses 207, 193, 179 and 163 were obtained experimentally by B/E linked scan by radical induced fragmentation reactions. In Part II eliminations of neutral fragments from the primary ions and the obtained ions by consecutive elimination reactions were evidenced experimentally by the B/E and B/E(1-E)1/2 linked scans. On this basis charge induced reactions with eliminations of acetaldehyde, ethylene and hydrogen are presented. The existence of fragmentation ions thus obtained is supplementary argued by measuring the ion masses at high resolution and the M+1, M+2 isotopic effects and by the calculation of the double bond equivalent (DBE). Source


Badescu V.,Romanian National Institute for Research and Development in Chemistry and Petrochemistry
Revue Roumaine de Chimie | Year: 2014

The aim of this article is the study of the fragmentation reactions of tetraethoxysiloxane (TEOS) as a precursor in the sol-gel process initiated by electronic impact in the ionization chamber of a mass spectrometer. Mass spectrum of an organic substance, as well as a silicon alkoxide such as TEOS is the result of a series of unimoleculare consecutive and competitive chemical reactions, which constitutes a pattern of fragmentation. The molecular ion of TEOS at mass 208 is a radical cation with positive delocalizated charge on the alkoxi bond Si-O-C. The primary fragmentation ions at masses 207, 193, 179 and 163 were obtained experimentally by B/E linked scan. The radical induced fragmentation reactions of the primary ions obtaining are presented and their existence is supplementary argued by measuring the ion masses at high resolution, the quantum calculations of the net atomic charges and the calculation of the double bond equivalent. Source


Peteu S.F.,Michigan State University | Peteu S.F.,Romanian National Institute for Research and Development in Chemistry and Petrochemistry | Boukherroub R.,Institut Universitaire de France | Szunerits S.,Institut Universitaire de France
Biosensors and Bioelectronics | Year: 2014

The importance of the so-called reactive nitrogen and oxygen species (RNOS) in biology and food technology has been widely recognized. However when these species are in excess, the steady-state maintained by physiological processes is disturbed. At this point, the nitro oxidative metabolic stress develops and its action in vivo over time leads to nitro-oxidative reactions in food and in living organisms, but also results in chronic degenerative diseases. Analytical methods enabling the assessment of the total antioxidant activity of a biological sample or a plant extract is therefore largely sought after. The ability of biosensors for rapid and real-time analysis that decreases the assay time and the possibility of automated and multi-analyte analysis at low cost has also allowed the quantitative and qualitative detection of RNOS. Among these RNOS, peroxynitrite (ONOO-) is a well-known inflammatory mediator during a number of physiological and pathological processes. Consequently, many efforts are underway to detect peroxynitrite in the biomedical field. This urgent demand makes the development of ONOO- specific probes of great interest. Not only they can be useful for the detection of disease states, but they will also allow for a screening-type analysis of potential signal transduction pathways in the cells.This invited review will critically discuss for the first time the very latest advancements and the challenges in the field of peroxynitrite biosensors and probes for in vivo and in vitro studies. Also, the main trends will be extracted, in order to chart the future directions and hence create an instrumental outlook. © 2014 Elsevier B.V. Source


Ion R.M.,Romanian National Institute for Research and Development in Chemistry and Petrochemistry
Journal of Biological Physics | Year: 2011

Photodynamic inactivation is a new promising approach to treat bacterial infections. Usually, the evaluation of the efficacy of this method is done through time-consuming and labor-intensive microbiological test methods. This paper describes the development and implementation of an optical method to evaluate the photodynamic inactivation of bacteria based on non-invasive diffuse reflectance measurements. Five Staphylococcus aureus cultures and 15 mice have been used in this study. A skin lesion was created on the back of all animals, and it was contaminated with S. aureus (5.16 ± 0.013 log CFU/ml). Toluidine Blue O (c = 8.67 × 10 - 3 M) has been used as a photosensitiser agent. The bacterial cultures and animals were exposed to laser radiation (λ = 635 nm, P = 15 mW, DE = 8.654 J/cm2) for 20 min. The photodynamic inactivation of bacteria was monitored by acquiring the wounds' reflection spectra at different time points and by microbiological exams on the bioptical material. The good correlation between the diffuse reflectance and colony-forming units demonstrates the value of this optical method based on diffuse reflectance measurements as a rapid technique to monitor photodynamic bacterial inactivation. © 2010 Springer Science+Business Media B.V. Source


Frone A.N.,Romanian National Institute for Research and Development in Chemistry and Petrochemistry | Berlioz S.,University of Toulon | Chailan J.-F.,University of Toulon | Panaitescu D.M.,Romanian National Institute for Research and Development in Chemistry and Petrochemistry
Carbohydrate Polymers | Year: 2013

Biodegradable nanocomposites were obtained from polylactic acid (PLA) and cellulose nanofibers with diameters ranging from 11 nm to 44 nm. The influence of treated (with 3-aminopropyltriethoxysilane) and untreated nanofibers on the thermal properties of PLA was investigated in detail using multiple session Differential Scanning Calorimetry (DSC) analysis. The nucleating effect of the cellulose nanofibers was confirmed by all the DSC runs (two melting and two crystallization steps). The morphology of both neat PLA and nanocomposites was explored for the first time using a new powerful AFM technique, Peak Force QNM (Quantitative Mechanical Property Mapping at the Nanoscale), which emphasized the nanolevel characteristics by elastic modulus mapping. QNM analyses showed a better dispersion of the silane treated nanofibers in the matrix as compared to the untreated ones. Moreover, a higher degree of crystallinity was detected in the PLA composites containing untreated nanofibers compared to the composites with treated ones. © 2012 Elsevier Ltd. Source

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