Resumo:
This work reports on the synthesis and characterization of six spirocyclic derivatives with potential incorporation into polymeric matrices for pH and lanthanide ion sensing. Among the various possible structural modifications that spiropyrans can undergo, those containing alkylsulfonate groups are commonly classified as photoacids. These molecules can be used to describe the acid/base equilibrium and to modify materials for use as sensors. Two synthesized spiropyrans containing this group (SON and SOH) had their acid- and photochromic properties studied by UV-Vis spectroscopy, and their pH and radiation dependent isomers were observed in the system. The other four synthesized spiropyrans (SPOH, SPOCH3, SPCOOH, and SPOCH3M) contain carboxylic acid or alcohol groups, commonly used for their interaction with metal ions. These two spiropyran derivate groups were structurally characterized by infrared spectroscopy, Raman spectroscopy, nuclear magnetic resonance, and mass spectrometry. To enable practical applications, it is essential to use materials such as high surface area polymeric matrices, which interact more efficiently with external media. Such materials can be obtained by electrospinning, in which the spiropyran derivatives were incorporated into biocompatible poly-ε-caprolactone (PCL) electrospun fibers with the aim of detecting acidic and basic vapors and lanthanide ions through colorimetric changes. The fibers obtained had their morphological aspects analyzed by scanning electronic microscopy and contact angle analysis. Apart from PLC-SPOCH3M fiber, the remaining PCL fibers containing spiropyran derivates showed surface properties compatible with hydrophobic systems. Materials designed for the detection of acid and base vapors can be reversibly reused according to the presented results. Moreover, these fibers showed efficient reversibility between acid and base vapors. The combination of results, containing the remaining spiropyrans, was fundamental to selectively identify and differentiate between all lanthanide ions, La3+ and Lu3+, by changes macroscopic changes (visible to the naked eye) and by emission analysis.
