Sensores bioquímicos baseados em redes de Bragg funcionalizadas com nanoestruturas

Abstract

This thesis presents the results of the production and characterization of a biochemical sensor based on fiber Bragg gratings functionalized with L-diphenylalanine nanotubes. The fiber in which the fiber Bragg gratings was inscribed was etched to remove cladding and then coated with L-diphenylalanine nanotubes to produce a sensor capable of detecting vapor from ethanol-methanol mixtures. Nanotubes were studied in its two phases (hexagonal and orthorhombic), analyzed by Raman spectroscopy, FTIR, X-ray diffraction, EDS and scanning electron microscopy (SEM). The temperature transition between phases was determined by small angle X-ray scattering (SAXS). The obverse temperature at which the phase transition begins was 135 °C and the complete transition occurred at 190 °C. Considering the methanol concentration in the steam, the orthorhombic phase presented a sensitivity of (7.3 ± 0.8) pm / (% v / v), 32 times higher than that observed in the hexagonal phase, with approximately the same response time. The maximum deviation of the measured wavelength was (0.98 ± 0.02) nm. In addition, mathematical models were proposed to describe the sensor response and hypothesized for the mechanisms that could lead to its nonlinear behavior.