0000000000541969
AUTHOR
Sérgio V. P. Barreira
Electrochemical Impedance Spectroscopy of Polyelectrolyte Multilayer Modified Electrodes
Electrochemical impedance spectroscopy, Fourier transform infrared reflection−absorption spectroscopy, and cyclic voltammetry were employed to characterize polyelectrolyte multilayers (PEMs) fabricated with poly(styrenesulfonate) as the polyanion and the polypeptides poly-l-histidine, poly-l-lysine, and poly-l-arginine as polycations. The layer-by-layer electrostatic assembly was produced onto alkanethiol-modified gold surfaces. The frequency response reveals that the effect of the number of layers seems to be related to a progressive reduction in the active area of the PEM-modified electrodes. The active area after the deposition of seven layers can be lower than 10% of its original value.…
Phytochemical characterization and biological activities of green tea (Camellia sinensis) produced in the Azores, Portugal
Abstract Background Green tea is not only one of the most widely consumed beverages worldwide, but is also known for its health promoting and therapeutic effects. Green tea is cultivated in areas with high humidity and acidic soils in China, Indonesia and Japan. Those places have well-marked dry and rainy seasons. In opposite, Azores have a climate with constant average annual rainfall and, unlike eastern regions, relatively constant air humidity throughout the year. While a brand implemented on the Portuguese market, the quality of green tea produced in Azores must be guaranteed. Quality control measures based on phytochemical determination of the chemical composition and biological activi…