Search results for " Spectroscopy"
showing 10 items of 6851 documents
Non-linear interactions of femtosecond laser pulses with graphene : photo-oxidation, imaging and photodynamics
2017
This thesis presents a study focused on interactions of femtosecond laser pulses with graphene, a one atom thick carbon membrane. Graphene, which exhibits exceptional electronic and optoelectronic properties, could provide considerable advantage over current silicon-based electronics. Graphene alone, being semi-metal, is not sufficient for electronic applications, but requires modification. For this, a set of methods for modifying and measuring the properties of graphene was developed. With the perspective of making graphene a suitable component for electronics, optoelectronics or photonics, ultrashort laser pulses were used for drawing patterns on graphene. The procedure modifies graphene …
Synthesis and characterization of a novel high luminescent gold-2-mercapto-1-methyl-imidazole complex
2010
Synthesis and characterization of a new gold-2-mercapto-1-methyl imidazole are reported. This new organic material shows an extraordinary fluorescence activity (superfluorescence) up to 220°C with an unusual quantum yield of 0.2. Both fluorescence and NMR spectroscopy were applied to understand the behavior of the gold-2-mercapto-1-methylimidazole complex. Results suggest that the superfluorescence activity can be attributed to the shrinking of the HOMO-LUMO band gap energy following complexation of the organic imidazole system with gold. Copyright © 2010 John Wiley & Sons, Ltd.
Brain Monitoring Via an Innovative CW-FNIRS System
2015
Functional Near InfraRed Spectroscopy (fNIRS) is an imaging technique mainly devoted to human brain monitoring. It is used as a non-invasive technique, in medical field, in order to measure the oxygen concentration of blood. This because the relatively good transparency of biological materials in the near infrared allows sufficient photon transmission through tissues. Within the so-called fNIRS range (650-900 nm), the main absorbers are blood chromophores, in particular the oxygenated and deoxygenated haemoglobin (HbO2 and Hb, respectively). When two or more wavelengths are used, changes of such chromophores can be computed by employing the modified Beer-Lambert law, thus providing importan…
Design and realization of a portable continuous wave fNIRS
2015
A design and implementation of a portable functional Near InfraRed Spectroscopy embedded system prototype is described. In this theoretical and experimental work, we present an embedded system hosting 64 LED sources and 128 Silicon PhotoMultiplier detectors (SiPM). The elementary part of the structure is a flexible probe “leaf” consisting of 16 SiPMs, 4 couples of LEDs, each operating at two wavelengths, and a temperature sensor. The hardware system is based on an ARM main microcontroller that allows to perform both the switching time of LEDs and the acquisition of the SiPM outputs. The performed preliminary experimental tests achieved very promising results, thus demonstrating the effectiv…
Continuous Wave fNIRS with Silicon Photomultiplier
2015
This work is focused on the development of a Continuous Wave (CW) NIRS integrated system with multi-wavelength LED sources between 700 and 950 nm and a Silicon Photomultiplier detector (SiPM) developed by STMicroelectronics. The Signal Noise Rate (SNR), measured placing the LEDs and an SiPM in a direct contact with the surface of a plastic phantom mimicking a real human head, results higher than the calculated minimum, required to detect small variation in the HbO2 and HHb concentration, till a source detector separation (SDS) of 6 cm.
Liposomes modified by mono- and bis-phthalocyanines: A comprehensive EPR study.
2016
The impact of selected metallophthalocyanines, featuring diverse molecular structure, upon the fluidity of liposome membranes was studied using the spin label EPR technique. The “mono”-type MPc’s (M = Zn, Sn; Pc = C32H16N8 is the phthalocyanine ligand) and sandwich LnPc2 complexes (Ln = Nd, Sm, Gd) were explored. Liposomes were obtained in a sonication process, from egg yolk lecithin (EYL) in water. TEMPO and 16-DOXYL spin labels were used to monitor the peripheral and central part of the lipid double layer, respectively, which allowed to localize the phthalocyanine additive within the bilayer, as well as to perform independent measurements of changes in fluidity upon addition thereof. All …
High Resolution-magic Angle Spinning NMR Study of Olive Leaves
2013
In recent years HR-MAS 1H NMR spectroscopy has proven to be a useful tool for the rapid determination of the metabolic profile of several solid and semisolid foods, such as fruits and vegetables, cheese and meat. Olive leaves are today recognized as direct sources of bioactive compounds and natural antioxidants (flavonoids, secoiridoids) suitable as food additives, and their extracts form the basis of beauty care products and pharmaceutical supplements. Thus, olive leaves are emerging as a new and potentially important product for olive tree growing regions. In this report we present the application of 1H and 13C HR-MAS 1D and 2D NMR spectroscopy for the characterization and analysis of tri…
Authentication of extra virgin olive oils by Fourier-transform infrared spectroscopy
2010
Fourier-transform infrared spectroscopy (FTIR), followed by multivariate treatment of the spectral data, was used to classify vegetable oils according to their botanical origin, and also to establish the composition of binary mixtures of extra virgin olive oil (EVOO) with other low cost edible oils. Oil samples corresponding to five different botanical origins (EVOO, sunflower, corn, soybean and hazelnut) were used. The wavelength scale of the FTIR spectra of the oils was divided in 26 regions. The normalized absorbance peak areas within these regions were used as predictors. Classification of the oil samples according to their botanical origin was achieved by linear discriminant analysis (…
Study of the formation of carbonyl compounds in edible oils and fats by 1H-NMR and FTIR
1999
Abstract Oils and fats start decomposing from the moment they are isolated from their natural environment. Heating accelerates oxidative rancidity and frying at high temperatures produces thermal degradation with the formation of decomposition products, such as aldehydes, ketones, free acids and hydroxilic compounds that in high levels can be harmful to human health. The decomposition products formed up to 300°C were determined by means of 1 H-NMR spectroscopy and an FTIR spectroscopic method was developed for the quantification of carbonyl compounds generated during heating. The results show that there is a formation of carbonyl compounds starting at 150°C and when the sample was heated at…
Analysis of Caffeine, Sweeteners, and Other Additives in Beverages by Vibrational Spectroscopy
2001
This chapter presents a review of the scientific literature on the use of vibrational spectroscopy, near-infrared (NIR), mid-infrared (mid-IR), and Raman, for the analysis of caffeine, sweeteners, and other additives in beverages and related products. Direct analysis procedures of coffee and tea, for both classification according to precedence or variety and quantitative determination of caffeine, are available. For beverage analysis, caffeine has been determined by direct attenuated total reflection (ATR) measurement or by transmission spectroscopy in the mid-IR region after extraction with chloroform. Different strategies have been employed for the analysis of sweeteners in beverages and …