Hybrids formed between polyvinylpyrrolidone and an A3B porphyrin dye: behaviour in aqueous solutions and chemical response to CO2 presence

Abstract

AbstractThis study reports the incorporation of an A3B mixed functionalized porphyrin, namely 5‐(4‐pyridyl)‐10,15,20‐tris(4‐phenoxyphenyl)porphyrin (PyTPOPP), into polyvinylpyrrolidone (PVP), a biocompatible polymer, with the purpose of preparing water‐soluble polymer–dye (PVP‐PyTPOPP) hybrids. The hybrids were obtained in two variants, differing by molar ratios, and their molecular characteristics and aggregation in dilute aqueous solutions were investigated using static and dynamic light scattering and analytical ultracentrifugation methods. The hybrids were characterized using 1H NMR, UV‐visible and Fourier transform infrared spectroscopies, atomic force microscopy (AFM) and transmission electron microscopy (TEM). A study of the influence of acidic media on the electronic spectra was carried out, evidencing the similar behaviour of the hybrids and the bare porphyrin. The interaction between CO2 and the PVP‐PyTPOPP hybrids was studied using UV‐visible spectroscopy and a continuous hypochromic response of the Soret band in direct relationship with increased CO2 concentration was noticed. Based on the UV‐visible spectral differences between the PVP‐PyTPOPP hybrids in acidic media and during CO2 exposure, we can presume that the mechanism of CO2 detection is not based on pH changes of the solution but on chemisorption phenomena which modify the surface properties as confirmed by TEM and AFM. These porphyrin–PVP hybrid nanomaterials offer the possibility for achieving optical and colorimetric sensors for monitoring CO2 and are also promising for biomedical applications. © 2015 Society of Chemical Industry