RESUMEN
We prepared zinc oxide nanoparticles (ZnO NPs) via a green synthesis and used them for the fluorescence sensing of ascorbic acid (AA). For obtaining these nanoparticles, we used an extract from Batavia lettuce as a reducing agent for zinc acetate in a simple, fast, and environmentally friendly synthesis. The ZnO NPs were characterized by X-ray diffractometry (XRD), ultraviolet-visible spectroscopy (UV-vis), Fourier Transform Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), photoluminescence, point of zero-charge (pHpzc), and chromaticity studies. We verified that the ZnO NPs had an average diameter of 6 nm, with a wurtzite crystalline structure, and when excited at 320 nm emitted radiation in the blue region. The methodology for AA detection is based on the observed increase in fluorescence of the molecule complex formed on the ZnO NPs surface after 20 min of interaction. The results indicated that the proposed technique of analysis is fast, simple, and highly sensitive, with a detection limit for AA of 5.15 µM. Furthermore, the nanoparticles presented excellent photostability for at least 30 days, and low sensitivity to other biological organic molecules. The green ZnO NPs also exhibited an efficient response to the presence of AA in actual complex samples, suggesting that the platform here proposed can find use in clinical analysis protocols.
RESUMEN
We report the preparation of flexible polystyrene/polypyrrole (PS/PPy) mats and their successful use as a resistive humidity sensor. These composite membranes were prepared by first obtaining PS films through the electrospinning technique, and then incorporating PPy chains by an in situ chemical polymerization of the pyrrole monomer. The PS fibers were homogeneously distributed, with diameters that obeyed a normal distribution with an average value of (1.04 ± 0.12) µm. The deposition of conducting PPy chains on the surface of the PS fibers was confirmed after characterizing the PS/PPy mats by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), contact angle measurements, and electrochemical impedance spectroscopy (EIS). When used as humidity sensors, the PS/PPy mats exhibited a sensor response of 128.6%, with fast response ((54.9 ± 3.5)s) and recovery times ((76.8 ± 11.1)s), and stable response under different humidity conditions over several days. These performance characteristics compare favorably to those of previous resistive humidity sensors discussed in the literature.