Search results for "Raman spectroscopy."
showing 10 items of 790 documents
Infrared based saliva screening test for COVID‐19
2021
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in an unprecedented need for diagnostic testing that is critical in controlling the spread of COVID-19. We propose a portable infrared spectrometer with purpose-built transflection accessory for rapid point-of-care detection of COVID-19 markers in saliva. Initially, purified virion particles were characterized with Raman spectroscopy, synchrotron infrared (IR) and AFM-IR. A data set comprising 171 transflection infrared spectra from 29 subjects testing positive for SARS-CoV-2 by RT-qPCR and 28 testing negative, was modeled using Monte Carlo Double Cross Validation with 50 randomized test and model sets. The testing se…
Raman study of crystals
1997
In this work we present a polarized Raman study of single crystals for several values of the concentration made using different scattering geometries. The Raman spectra, composed of broad bands, have been fitted in accordance with a symmetry analysis which allowed us to assign the vibrational modes, and determine their frequencies and damping constants. The results are compatible with an average hexagonal symmetry for the solid solutions with x in the range . In each of the spectra we found two bands at about 590 and , probably associated with the existence of structures in the solid solutions.
Tunable Polarons in Bose-Einstein Condensates
2017
A toolbox for the quantum simulation of polarons in ultracold atoms is presented. Motivated by the impressive experimental advances in the area of ultracold atomic mixtures, we theoretically study the problem of ultracold atomic impurities immersed in a Bose-Einstein condensate mixture (BEC). The coupling between impurity and BEC gives rise to the formation of polarons whose mutual interaction can be effectively tuned using an external laser driving a quasi-resonant Raman transition between the BEC components. Our scheme allows one to change the effective interactions between polarons in different sites from attractive to zero. This is achieved by simply changing the intensity and the frequ…
On the interpretation of the Raman spectra of Maya Blue: a review on the literature data
2011
The Raman spectroscopy of Maya Blue (MB), a nanostructured organic–inorganic hybrid material, has received considerable attention. A re-evaluation of the Raman literature data for indigo dye, genuine MB samples and model specimens obtained by the binding of indigo to phyllosilicate clays, such as palygorskite and sepiolite, using chemometric analysis of normalised spectra is reported. Available data present features in support of the following ideas: (1) dehydroindigo accompanies indigo in MB; (2) different topological isomers, i.e. dye molecules attached to different coordinative sites of the palygorskite framework, are involved in MB; and (3) different procedures were probably used for pr…
MICROSCOPIC TECHNIQUES AND A MULTI-ANALYTICAL APPROACH TO CHARACTERIZE THE MATERIALS OF TWO RUSSIAN ICONS
2018
Two 19th century Russian icons, from the Museo Diocesano of Palermo, were analysed by UV photography, X-ray fluorescence, energy-dispersive X-ray fluorescence (ED-XRF), optical microscopy, micro-Raman spectroscopy and Scanning Electron Microscopy, combined with energy dispersive x-ray analysis, (SEM/EDS). The multi-analytical study of the icons “Protezione della Madre di Dio” (Pokrov’s Icon, Protection of Holy Mother of God) and ‘’Madre di Dio Gioia di Tutti gli Afflitti’’, (Holy Mother of God, Joy of all the afflicted), have been performed to reveal materials and technological features of the original painting of the 19th century as well as the materials used during past restoration works.…
Influence of application method on the use of ammonium phosphate as preservative
2018
This work deals with the application of the Ammonium Hydrogen Phosphate as preservative and consolidant during the restoration and consolidation intervention on a twin columns group in the east side of the Santa Maria La Nova Cloister in Monreale, UNESCO Heritage from 2016. The Superintendency for Fine Arts in Palermo prescribes the use of ammonium phosphate as the only acceptable material for the consolidation of the Cloister, so this work deals with the influence of application method and solution concentration on the results achievable with this material. Particularly as the treatment have to be done on vertical surfaces the use of a supporting material is mandatory so the focus is on th…
Nanostructured anatase TiO2 densified at high pressure as advanced visible light photocatalysts
2015
This study reports on characterization and photoactivity of nanostructured TiO2 samples, which have been permanently densified under high pressures, up to 2.1 GPa. Commercial Mirkat 211 anatase has been used as a benchmark sample, in order to investigate the effect of unidirectional high pressure on structural, optical and photocatalytic properties of TiO2. Vibrational Raman spectroscopy shows that the treatment does not cause transitions among the different crystalline phases of titanium dioxide. UV-vis diffuse reflectance spectra reveal that increasing pressure gives rise to a shift of the absorption onset towards higher wavelength enhancing the photoactivity under visible radiation. Samp…
Raman spectroscopy study of β-irradiated silica glass
2003
International audience; Natural and synthetic silica glass samples with different OH content have been submitted to β-irradiation at different doses from 106 to 5 × 109 Gy in a Van de Graaff accelerator. Structural changes under irradiation have been analyzed by Raman spectroscopy. The main findings are: (i) a decrease of the Si–O–Si angular dispersion and the average Si–O–Si angle as a function of dose and (ii) an increase of number of three-membered SiO4 ring concentration during irradiation. These results show therefore that purely electronic excitation from β-irradiation induces in a-SiO2 small but significant structural changes of the SiO4 membered ring statistics (size and dispersion)…
Porous silicon based photoluminescence immunosensor for rapid and highly-sensitive detection of Ochratoxin A.
2017
A rapid and low cost photoluminescence (PL) immunosensor for the determination of low concentrations of Ochratoxin A (OTA) has been developed. This immunosensor was based on porous silicon (PSi) and modified by antibodies against OTA (anti-OTA). PSi layer was fabricated by metal-assisted chemical etching (MACE) procedure. Main structural parameters (pore size, layer thickness, morphology and nanograins size) and composition of PSi were investigated by means of X-Ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. PL-spectroscopy of PSi was performed at room temperature and showed a wide emission band centered at 680 ± 20nm. Protein A was covalently immobilized …
On-line tools for microscopic and macroscopic monitoring of microwave processing
2007
International audience; Direct monitoring of temperature, chemistry and microstructure is required to understand microwave heating in more detail, in order to fully exploit the unique features this non-equilibrium processing method can offer. In this paper, we show first that microwave radiometry can be used to follow volumetrically the thermal trajectory of microwave-heated aluminium powder. In-situ Raman spectroscopy is then shown to evidence thermal gradients between diamond and silicon grains in a binary powder mixture. Finally, perspectives and preliminary results of microstructural analysis obtained from X-ray microtomography are presented.