Dispositivos analíticos colorimétricos baseados em nanofibras poliméricas para sensoriamento de contaminantes ambientais.

Abstract

Portable, low-cost colorimetric sensors are emerging as practical tools for field environmental monitoring. In this study, two colorimetric analytical devices based on bacterial nanocellulose (BNC) and electrospun polymeric nanofiber membranes were developed. The environmental sensors were used to detect metal ions in samples using digital colorimetry. The BNC was functionalized with the dye 4-(2-thiazolylazo)resorcinol (TAR), widely used for colorimetric Ni2+ detection. The BNC matrix provided uniform dye incorporation due to its high porosity, specific surface area, and abundance of hydroxyl groups. The sensor demonstrated a linear response up to 10 mg L-1, a detection limit of 0.18 mg L-1, good selectivity against interfering ions, and analytical stability for at least 40 days. Applications in real water samples resulted in recoveries between 93.1% and 102.9%. Additionally, an analytical device entirely based on electrospun nanofiber (NAD) membranes was developed for the colorimetric detection of Cr(VI). The system consists of a trilaminar architecture obtained by sequential electrospinning, composed of: (i) a hydrophobic poly(lactic acid) (PLA) layer, (ii) a PLA/poly(ethylene oxide) (PEO) evidence layer containing 1,5-diphenylcarbazide (DPC), a reagent widely used for Cr(VI) determination, and (iii) a PLA/PEO sealing layer. The good adhesion between the layers, combined with the high porosity of the membranes and the distributed distribution of DPC, allowed the production of sensors with high repeatability and reproducibility. NAD showed a linear response in the range of 12.5 to 100 µmol·L-1 (0.65 to 5.20 mg·L-1), a detection limit of 0.02 µmol·L-1 (1.0 µg·L-1), and excellent selectivity. Tests with real samples indicated recoveries between 92.0% and 106%. The results highlight the potential use of nanofiber membranes, both of biological and synthetic origin, in the fabrication of complementary, sensitive, and portable colorimetric sensors.