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5 results on '"Alvarez-Ros M. C."'

1. Catalytic modification of gallic acid on a silver surface studied by surface-enhanced Raman spectroscopy

Author

Alvarez-Ros M. C., Sanchez-Cortes S., Francioso O., Garcia-Ramos J. V., Alvarez-Ros M.C., Sanchez-Cortes S., Francioso O., and Garcia-Ramos J.V.

Subjects
SERS, gallic acid, polymerization, humic-like substances
Abstract

We studied the chemical changes undergone by gallic acid (GA) when adsorbed on a colloidal silver surface by means of surface-enhanced Raman spectroscopy (SERS). The application of the SERS technique allows a remarkable Raman sensitivity enhancement and the strong fluorescence quenching needed to characterize the highly colored products of GA oxidative condensation. We found that GA can undergo a ring opening, a polymerization of aromatic rings or a combination of both mechanisms, leading to the formation of humic-like substances. The influence of pH and light irradiation on these catalytic processes was investigated in relation to the importance of these mechanisms. © 2001 John Wiley & Sons, Ltd.

Published
2001

4. Adsorption and chemical modification of gallic acid on silver nanoparticles studied by Raman spectroscopy: Effect of anions and cationic pesticide paraquat

Author

Alvarez-Ros, M. C., Sánchez-Cortés, S., ORNELLA FRANCIOSO, García-Ramos, J. V., Alvarez-Ros M.C., Sanchez-Cortes S., Francioso O., and Garcia-Ramos J.V.

Subjects
Paraquat, Polyphenol, Gallic acid, SERS, Silver nanoparticles, Humification
Abstract

In this work, we have carried out a study of the chemical change of gallic acid in solution and on Ag colloids by using UV-vis absorption and surface-enhanced Raman spectroscopy (SERS). Gallic acid is a natural molecule occurring in plants which is involved in processes with important industrial and environmental impact, such as humification or food browning, where a chemical degradation of this phenol is involved. The adsorption of gallic acid on a metal surface can catalyse the chemical modification of the phenols, thus having interest in remediation processes where polyphenols of different nature are involved. Parameters such as pH, light irradiation and phenol concentration were checked in this work in relation to degradation mechanism catalysed by Ag. Finally, we have also tested the influence of the cationic pesticide paraquat in the chemical changes of GA as a possible agent, which may change the humification mechanisms.

5. FT-IR and FT-Raman spectra of 6-chlorouracil: molecular structure, tautomerism and solid state simulation. A comparison between 5-chlorouracil and 6-chlorouracil.

Author

Ortiz S, Alvarez-Ros MC, Palafox MA, Rastogi VK, Balachandran V, and Rathor SK

Subjects
Algorithms, Computer Simulation, Crystallization, Dimerization, Hydrogen Bonding, Models, Molecular, Molecular Conformation, Normal Distribution, Spectrophotometry, Infrared, Spectroscopy, Fourier Transform Infrared, Spectrum Analysis, Raman, Uracil analogs & derivatives, Uracil chemistry
Abstract

A Raman and IR study of the biomolecule 6-chlorouracil was carried out in the solid state. The unit cell found in the crystal was simulated as a tetramer form by density functional calculations. Specific scale factors and scaling equations deduced from uracil molecule were employed in the predicted wavenumbers of 6-chlorouracil. The scaled wavenumbers were used in the reassignment of the IR and Raman experimental bands. Good reproduction of the experimental wavenumbers is obtained and the % error is very small in the majority of cases. A comparison between the molecular structure and charge distribution of 6-chlorouracil and 5-chlorouracil molecules was presented. The effect of the hydration with the PCM model in the molecular structure and charges was discussed. The optimum tautomers of 6-chlorouracil were optimized and analyzed. Six of them were related to those of uracil molecule. The effect of the halogen substitution in the sixth position of the pyrimidine ring in the stability of the different tautomers was evaluated. HOMO and LUMO orbital energy analysis were carried out., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Published
2014
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